# Testing C/D cells in Maha C9000



## Power Me Up (Nov 18, 2008)

Since there seems to be some confusion on how to connect C and D sized cells to a Maha C9000, I'll create this thread and include a photo of how I've done it:






Keep in mind that I'm using one of the earlier generation C9000 chargers that measures the cell voltage during the rest period instead of whilst the cell is under load - this pretty much eliminates the effect of the lead resistance.

The clear AA sized adapters that hold the leads in place came from DealExtreme:
http://www.dealextreme.com/details.dx/sku.3657

The C & D sized individual holders came from a local electronics store.

Feel free to post any questions!


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## Bonky (Nov 18, 2008)

very nice, though I think I would use shorter, heavier gauge wire.


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## Power Me Up (Nov 19, 2008)

Bonky said:


> very nice, though I think I would use shorter, heavier gauge wire.



It's only a gut feeling on my part, but I think that the extra contact resistances would probably be greater than the lead resistance...


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## Bonky (Nov 19, 2008)

you could certainly be right about that. at what rate do you charge 'em?


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## Power Me Up (Nov 19, 2008)

Bonky said:


> you could certainly be right about that. at what rate do you charge 'em?



The charging that I did with the C9000 was at 2A - the charger did get very warm whilst charging them at that rate, so I just charge them on the C808M now. Besides that, it's also a bit of a hassle getting the adapters to hold the wires in place on the negative ends...


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## Bonky (Nov 19, 2008)

When it was described I thought you'd soldered the leads onto the battery adapter contacts. Actually, I thought you'd drilled holes in the plastic and had soldered the leads onto the INSIDE of the battery adapter thing.


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## Bones (Nov 19, 2008)

Power Me Up said:


> ...
> 
> The clear AA sized adapters that hold the leads in place came from DealExtreme:
> http://www.dealextreme.com/details.dx/sku.3657
> ...



Many thanks for the images Power Me Up.

Regrettably, the AAA to AA adapters have been 'Out of Stock' at DealExtreme for several months now.

Does anyone know of another source, preferably in a similiar price range?


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## Power Me Up (Nov 19, 2008)

Bones said:


> Many thanks for the images Power Me Up.
> 
> Regrettably, the AAA to AA adapters have been 'Out of Stock' at DealExtreme for several months now.
> 
> Does anyone know of another source, preferably in a similiar price range?



How about here:
http://www.kaidomain.com/ProductDetails.aspx?ProductId=2704


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## KD5XB (Nov 19, 2008)

I'm wondering why such a nice charger is limited to AA/AAA only -- seems to me there might be a pretty good market for a similar charger for C and D cells.


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## Bones (Nov 19, 2008)

Power Me Up said:


> How about here:
> http://www.kaidomain.com/ProductDetails.aspx?ProductId=2704



Many thanks again Power Me Up.

Incidentally, I just determined the break-in settings on my first edition MH-C9000 range from 500mAh to 20000mAh, so I'm hoping it will provide a proper break-in for NiMH and NiCAD cells within the same capacity range.

I plan to use it to at least exercise my C and D sized Eneloops providing they ever make it out of Japan.

I understand this cooling fan set-up utilized by coppertail will suffice to dissipate the additional heat away from the MH-9000:

http://www.candlepowerforums.com ... post1903127

Providing it's not larger than 35mm wide x 15mm deep, there's also room inside the charger directly below the upper-right ventilation slots for a 12 volt fan. It could probably even be powered from the adjacent DC input pins on the underside of the circuit board.


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## Bonky (Nov 19, 2008)

I'm thinking, if you're merely holding the leads against the charger contacts, properly-cut wooden dowels could be used if the adapters can't be found.


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## Bones (Nov 22, 2008)

Bonky said:


> I'm thinking, if you're merely holding the leads against the charger contacts, properly-cut wooden dowels could be used if the adapters can't be found.



Although not something I would have anticipated either, wooden doweling isn't an ideal spacer or insulator:



SilverFox said:


> In higher humidity areas and when charging at higher currents, I recommend using something other than wood. I found some wood spacers "leaking" when charging at 2 amps. This dielectric leakage was caused by the moisture content in the wood.
> 
> Plastic works great...





SilverFox said:


> I had to modify my set up. I was charging at 2 amps and noticed that my wooden dowel was heating up. It must have picked up some moisture. I changed to plastic spacers and everything works fine now.
> ...


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## Bonky (Nov 22, 2008)

huh, so the wood was conducting? weird. Maybe if you baked it in an oven at 200F for an hour then shellacked it or something?


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## Mr Happy (Nov 22, 2008)

I think the idea of wood conducting enough to matter when used as a dummy cell in a charger is likely a case of drawing the wrong conclusion from the evidence. A damp piece of wood from natural air humidity is likely to have a resistance in the range of 100k to 1M. If we take an absolutely conservative worst case and suppose the resistance is as low as 1k or 1000 ohms then with the 1.5 volt charging voltage the current would be 1.5 mA.

We can calculate the power dissipation at this current from the formula (power) = (current squared) x (resistance). That would give 0.0015^2 * 1000 = 0.002 watts, or 2 mW. I couldn't therefore imagine significant heating to occur from electrical current.

What I think is more likely is that wood is a naturally "warm" material (it's basically a good thermal insulator and also a good holder of heat). Since the C9000 generates a lot of its own heat when charging at 2 amps I suspect the most likely explanation is that the wooden spacers warmed up from the heat of the Maha and then felt warm to the touch as a result.

Plastic spacers would not have the same ability to hold heat and transmit it to the human hand so they would feel cooler.


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## Bonky (Nov 22, 2008)

ok math smarty, can you calculate how much current would have to flow through the wood to warm it, say, to 100 degrees F?


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## JohnR66 (Nov 22, 2008)

Bonky said:


> ok math smarty, can you calculate how much current would have to flow through the wood to warm it, say, to 100 degrees F?


 
This seems to be enough current...
http://www.youtube.com/watch?v=pNsUDmlG6js&feature=related


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## Mr Happy (Nov 22, 2008)

Bonky said:


> ok math smarty, can you calculate how much current would have to flow through the wood to warm it, say, to 100 degrees F?


I sure can. 

First we need to estimate the rate of heat removal from the surface. To do this, we can assume a very conservative value of the natural convection film coefficient in air of 3 W/m2/K. (This is quite low; more likely values would be from 5-10 W/m2/K, but we want to assume a worst case scenario here.) 

Next, we need the surface area for cooling. Since an AA cell is 14 mm diameter by 50 mm long, we get a surface area of:

A = pi/4 x 14^2 x 50 = 7700 mm^2 = 0.0077 m^2

Not all of this area is equally exposed for cooling since some of it is underneath or next to other spacers. To make a worst case estimate we will take only a quarter of this area, let's say 0.002 m^2.

You asked for our spacer to have a surface temperature of 100 F. I'm going to do the calculations in SI units since it works more conveniently with current and voltage, so that becomes 38 C. Let's assume the air temperature in the room is 20 C, which is an averagely comfortable 68 F.

We now find the heat loss from the spacer is estimated at:

Q = 3 W/m2/K x 0.002 m2 x (38 - 20) K = 0.1 W.

Next, we need to see how much current would generate 0.1 W of heat with a supply at 1.5 V. Since (power) = (current) x (voltage), we find the current would be: 

I = 0.1 W / 1.5 V = 0.067 A.

Lastly, we need to see what resistance would produce a current of 0.067 A at 1.5 V. We find that by Ohm's law: 

R = V / I = 1.5 / 0.067 = 22 ohms.

Having done the calculations, we then have to see what the answer means. It suggests that for a wooden spacer to heat up to 100 F by resistive heating from a 1.5 V supply, it would need to have a resistance no higher than about 20 ohms. In practice this is a very low resistance indeed, and unless the wood was impregnated with salt or some other conductive substance, it is extremely unlikely that it could have such a low resistance. We therefore presume that the use of wood for insulating dummy cells in a battery charger is not likely to be a problem. :thumbsup:


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## Bonky (Nov 23, 2008)

oo:

:bow:


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## SilverFox (Nov 23, 2008)

Hello Mr Happy,

Interesting...

Your numbers suggest that I was "kiln drying" my wooden dowels with the heat from the charger. It has been awhile since I set that up, but I seem to remember the dowels getting hotter than the charger was.

Perhaps higher humidity and close proximity to salt air contaminated my wood...

I spent a little time looking up the resistance of wood and it seems that it is dependent on the moisture content. At about 20% moisture, wood seems to have a low end resistance of around 1000000 ohms per cm. Since an AA cell is around 5 cm, a rather wet dowel would have a resistance of around 5000000.

I still think it is better to use plastic, but it appears that wood will also work.

Tom


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## Mr Happy (Nov 23, 2008)

SilverFox said:


> Your numbers suggest that I was "kiln drying" my wooden dowels with the heat from the charger. It has been awhile since I set that up, but I seem to remember the dowels getting hotter than the charger was.


It may perhaps be that they felt hotter, but the actual temperature was similar to the charger? Sometimes the sense of touch can be misleading when comparing different materials. To be really sure of the situation I think one would need to use an infrared thermometer and measure the actual surface temperatures...

[Edit: I plan to use wood for some of my constructions since it is easy to obtain and easy to work with. I will report back if I come across any problems with that choice.]


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## Bonky (Nov 24, 2008)

yep, the reason wood popped into my mind is that it's easy to find a dowel the right diameter and easy to cut it to the right length. Plastic would have to come pre-formed (like the adapters) and would be more expensive.


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## VidPro (Mar 31, 2009)

wanna make your OWN plastic things, you could try TAP plastics acrylic tubes, and BALLS, the tubes come in many sizes, and the balls fit in the end, and with acrylic solvent (called glue) you could meld the ball into the end of the tube.
then you could saw/drill the solid ball and mount in the solid connections, it would all work out great till the heat hit and turned it all into a acrylic blob  but that is one way to get plastic that cuts as quick as dowels. with the one caveat that they are certannly not heat resistant.


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## Black Rose (Apr 18, 2009)

Is there a desired guage of wire to use for connecting the C/D cell adapters to the C9000?

All I currently have is 24 guage teflon coated silver braided wire.


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## Bonky (Apr 18, 2009)

I would assume the bigger the better.


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## Black Rose (Apr 19, 2009)

But wouldn't a larger wire result in more resistance?

The D cell holders I am looking at come pre-wired and have what looks like 22 or 24 guage wire.

I'm thinking it may be simpler just to buy a charger designed for D cells and be done with it, although using the C9000 on them would be nice.


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## VidPro (Apr 19, 2009)

Black Rose said:


> But wouldn't a larger wire result in more resistance?
> 
> The D cell holders I am looking at come pre-wired and have what looks like 22 or 24 guage wire.
> 
> I'm thinking it may be simpler just to buy a charger designed for D cells and be done with it, although using the C9000 on them would be nice.


 
the larger and the better a wire is the less resistance it has, like a good copper wire, less resistance.
The "stuff" that comes on a RadShack holder is , , , easily replaced.
also many battery holders have press-fit or riveted stuff in them, i always like to solder that direct, so the wire is on the tab and spring , so it doesnt come disconnected/loose, hard to do when they melt so easily.
speaker wire often has nice copper in it usually and its cheap.

resistance higher and lower is always confusing at first thought, less is more  and more is less, so its a bit confusing.
so a person could think ZERO resistance is "best", then its easier to think of it, anything more than zero is more resistance, and resistance is less connection. 
More resistance is less connection.
bet that didnt help


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## Bonky (Apr 20, 2009)

think of it like water in a pipe, the larger diameter the pipe the easier the water will flow through it.


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## Black Rose (May 2, 2009)

Well here's my latest invention, based on ideas I've gleaned from others on this forum.







18 gauge copper wire with #8 ring terminals soldered on the ends.
Hardwood dowels with electrical tape on the ends (in case there is any moisture in the wood).

1/4" nickel plated rare earth magnets hold the ring terminals to the positive and negative ends of the batteries.

The D cell holders that are available locally are $5 a piece and have 22 or 24 gauge wire attached.
The holders I really want are too expensive to obtain at the moment, so this will suffice for now.


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## TakeTheActive (May 2, 2009)

Is the Dowel -> Ring Terminal -> C9000 connection a "Pressure Fit" or are there screws too?
.
Is the Cell -> Magnet -> Ring Terminal connection magnetism only?
.
What is your source and price for the magnets?
.
Have you charged the D with 2000mA and checked all the connections for heating?
Thanks!


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## Black Rose (May 2, 2009)

1. Pressure fit.
2. Magnetism only.
3. Lee Valley tools - variable price depending on quantity purchased. I bought 10 and paid 0.27 each CDN.
4. No, I'm only planning on doing 1500 mA (0.5C)

EDIT: I have been checking the cells and connections during the discharge cycles (1000 mA) to check for heating.


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## Black Rose (May 2, 2009)

I did a charge of the Rayovac Hybrid D cells at 1500 mA using the C9000 and it seems to be working OK.

There were no heat issues with the cells or the connections with this first charge, so that is a good thing. 

EDIT: There was a problem with a bad connection due to the pressure fit of the ring terminal that resulted in one channel not having full contact.
That affected the overall charge for that bay. I have resolved that issue and am now recharging the cells to see what affect it had on the capacities.

I'm not sure how much additional resistance, and possibly charging innefficiencies, have been introduced by using the wire jumpers and magnets to charge the cell.


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## Bonky (May 3, 2009)

I can't imagine you could do much better than that. The voltage readings on the charger might be a little off with the extra wire, but I can't imagine it would be enough to make a difference.

Might be interesting to read the voltages at the battery terminals themselves with a multimeter to see if there's any difference vis-a-vis the charger's display.


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## Black Rose (May 5, 2009)

Well I completed a break-in cycle on the Hybrid C & D cells and it went well.

My only concern about the setup I used was that the slightest bump had the potential to break the connection to the positive or negative ends of the cells, since the only thing holding the ring terminals on them was magnetic force.

I can't afford to buy a Maha C808M, so I am tempted to buy some C & D battery holders and solder leads to those to have more solid connections.

The wooden dowels seem to have worked OK (nothing burned) but I'd like to use safer material for the dummy cells. 
I might bite the bullet and order those AAA->AA adapters from KD and do something with those.

Or I could spend $27 and get the ROV PS20 Universal charger and hope it uses a charge current that is within the preferred range for NiMh cells.


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## Mr Happy (May 6, 2009)

Black Rose said:


> Well I completed a break-in cycle on the Hybrid C & D cells and it went well.
> 
> My only concern about the setup I used was that the slightest bump had the potential to break the connection to the positive or negative ends of the cells, since the only thing holding the ring terminals on them was magnetic force.
> 
> ...


If you feel the magnetic connections were weak maybe it is because you had the ring terminals between the magnet and the battery. I somehow feel that if the magnet was fixed directly to the battery it would be very difficult to shift, especially with the very strong magnets around these days.

I am also curious why you should have any fear about the wooden dowels being unsafe...? There really is no chance of a problem there unless something gets hot enough inside the charger to start a fire, in which case your C9000 will already be melting into oblivion.

On balance I would say what you have there is fundamentally good and just needs a bit of fine tuning.


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## TakeTheActive (May 6, 2009)

Black Rose said:


> ...EDIT: There was a problem with a bad connection due to the pressure fit of the ring terminal that resulted in one channel not having full contact.
> That affected the overall charge for that bay. I have resolved that issue and am now recharging the cells to see what affect it had on the capacities.
> 
> I'm not sure how much additional resistance, and possibly charging innefficiencies, have been introduced by using the wire jumpers and magnets to charge the cell.


I was initially concerned about your using '_tinned_' ring terminals and if filing off the coating would 'reduce the resistance / improve the connection'.


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## Bonky (May 6, 2009)

There's nothing unsafe about the wooden dowels. What I would do is put a small screw in each end that not only holds down the wire (via a loop connector) but also serves as the connection to the charger.

And I would solder the magnets onto the ring connectors of the other ends and attach them directly to the cells.


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## Bonky (May 6, 2009)

Unless you soak your dowels in sea water for a month before using them, they are going to have a resistance pretty close to *∞* for our purposes..


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## Black Rose (May 6, 2009)

Mr Happy said:


> If you feel the magnetic connections were weak maybe it is because you had the ring terminals between the magnet and the battery.


I had the magnets on their sides, so that the side of the magnet passed through the hole in the ring terminal to hold it in place. 
I also tried having the magnet flat and holding the terminal in place that way. Either way the connections seemed they might come off if the wires or batteries were moved enough.



> I somehow feel that if the magnet was fixed directly to the battery it would be very difficult to shift, especially with the very strong magnets around these days.


I could try attaching the magnet to the battery, but I would have to sandwich the ring terminal between two magets. 
The ring terminals I bought do not appear to be made of a material that the magnets will adhere to. I'll check that again tonight.

Maybe I simply need to get the next size up in the magnet (3/8", 5lb strength).



> I am also curious why you should have any fear about the wooden dowels being unsafe...? There really is no chance of a problem there unless something gets hot enough inside the charger to start a fire, in which case your C9000 will already be melting into oblivion..


Good point. I had read SilverFox's comment and saw your formulas  
Not sure if I needed the electrical tape on the ends of the dowels, but it's an extra layer of protection.



> On balance I would say what you have there is fundamentally good and just needs a bit of fine tuning.


You're right, it just needs some fine tuning. 

Even my wife questioned why I want to significanlty later paths when what I did worked quite well.

She went from "You're not going to leave that thing running overnight are you?" to "If it works and it's safe, why spend the extra money to significantly change it?".



Bonky said:


> What I would do is put a small screw in each end that not only holds down the wire (via a loop connector) but also serves as the connection to the charger.
> 
> And I would solder the magnets onto the ring connectors of the other ends and attach them directly to the cells.


 
I could try that as well. The magnets are cheap enough and easily available locally if they get heat damaged.


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## Black Rose (May 6, 2009)

I confirmed that the magnets will not adhere to the ring terminals.

I did try sandwiching a ring terminal between two magnets, and that is one solid connection. I think that may be the answer to that problem.

Can too much magnetic force do any damage to a battery? 
The magnets I am using are rated at a maximum of 2.5 lbs of magnetic force.


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## Bonky (May 6, 2009)

Black Rose said:


> I confirmed that the magnets will not adhere to the ring terminals.



Sux 



> I did try sandwiching a ring terminal between two magnets, and that is one solid connection. I think that may be the answer to that problem.



Nice! 



> Can too much magnetic force do any damage to a battery?
> The magnets I am using are rated at a maximum of 2.5 lbs of magnetic force.



It'll be fine.


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## Russel (Feb 20, 2010)

I made this adapter a while back for performing break-in, and testing capacity, on D cells with a MH-C9000.

(I apologise for the poor angle. The display is a little hard to read.)






I made the charger end of the adapter from teflon with brass ends.















That way I could feed wire through the center of the teflon body, solder then to the brass ends, and thread the ends into the body.


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## MarioJP (Feb 20, 2010)

so I am guessing that the D cells are being charged in series??


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## Mr Happy (Feb 20, 2010)

MarioJP said:


> so I am guessing that the D cells are being charged in series??


What leads you to think that?


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## Russel (Feb 20, 2010)

MarioJP said:


> so I am guessing that the D cells are being charged in series??


 
No, Each cell is connected to it's own cell bay on the charger. They are independent of each other.


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## MarioJP (Feb 20, 2010)

usually battery holders are in pairs. But I see what he did. Be no way to have one channel charge 2 D cells in series but thanks for the clarification.


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## Russel (Feb 20, 2010)

I can see how it could be confusing. The cell holder that I used was made so that the batteries would be in series, but I cut the connections making each cell independent of each other.


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## Mr Happy (Feb 20, 2010)

The usual challenge with that setup is that the steel springs used in cheap battery holders have much higher resistance than copper wire. You might consider bypassing the springs for better conductivity...?


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## Russel (Feb 20, 2010)

Yep, the cheap cell holder is the weakest link in the adapter. I soldered the wires to all but one spring in an attempt to keep resistance at a minimum. The one that has a small socket head screw holding it had no where I could really solder to without melting the plastic. I only use the adapter for break in and discharge a low current levels. So, for now it works well enough.

I have been bouncing ideas around in my head thinking about how I would go about making a good cell holder. I would like to make something that didn't cover the main cell body to allow for good convection cooling. I am wondering if it would be better to have a spring loaded brass contact, or solid contacts at both ends of the batteries with some kind of screw between the cells to assure good contact pressure with the cell. If a screw between the cells was spring loaded, the electrical resistance of the spring would not be a factor. I like some of the 4AA to 1D cell adapters you can find here.

https://www.candlepowerforums.com/posts/2849142


I am just trying to figure out the best way of holding two D cells electrically independent of each other while still allowing good convection cooling.



Thinking out loud...


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## Mr Happy (Feb 20, 2010)

Russel said:


> I am just trying to figure out the best way of holding two D cells electrically independent of each other while still allowing good convection cooling.


See my other thread on analyzing batteries.

You can take thin strips of copper foil and attach strong magnets to one side of them using a dab of glue. Then solder your wires to the other end of the strips. The magnets will clamp the foil electrodes very firmly to the battery terminals giving an almost zero resistance connection. To make it even better you can silver plate the foil using some of the stuff used for circuit boards -- then you won't have to keep polishing the copper to remove oxidation.

If you get magnets with the shiny metal plating on the outside you can try soldering wires directly to the magnets like LuxLuthor does. But this takes a bit of skill to avoid destroying the magnetism with the heat of soldering.


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## Russel (Feb 20, 2010)

I was considering something like the battery clamp I 'adapted' for my CBAII, but I would rather make something with the materials on hand rather than having to purchase more. Heck, I've got the machine tools, I need to use them to help justify the cost!

Here are a couple photos of my CBAII battery clamp.











I'll be sure to read through your other thread on analyzing batteries. Thank you for the suggestions.


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## Apollo Cree (Feb 21, 2010)

Russel said:


> I was considering something like the battery clamp I 'adapted' for my CBAII, but I would rather make something with the materials on hand rather than having to purchase more. Heck, I've got the machine tools, I need to use them to help justify the cost!
> 
> Here are a couple photos of my CBAII battery clamp.
> 
> ...



The way those types of clamps work, it would be real easy to put too much squeezing force on the battery and damage it, perhaps causing leaks later. 

Even if you don't overtighten the clamps, I wonder if thermal expansion during charging might cause mechanical stress.

Most battery holders have some degree of springiness in the design. I always thought this was in order to allow you to insert and remove batteries and still get a good contact, but I wonder if springiness is needed to prevent excess force on the cells due to mechanical and thermal expansion consideration.


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## Mr Happy (Feb 21, 2010)

Apollo Cree said:


> Even if you don't overtighten the clamps, I wonder if thermal expansion during charging might cause mechanical stress.
> 
> Most battery holders have some degree of springiness in the design. I always thought this was in order to allow you to insert and remove batteries and still get a good contact, but I wonder if springiness is needed to prevent excess force on the cells due to mechanical and thermal expansion consideration.


Cells do expand a bit when charging, especially using higher C rates. I recently noticed an AA Eneloop was domed a bit at the negative end when I took it off charge. I didn't think to measure its length, but it would have been a little bit longer than when it started. A fair bit of internal pressure can build up inside NiMH cells when on charge.


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## Russel (Feb 21, 2010)

I agree that some contact pressure is needed, but that there should be some give to the holder. I am considering four strips of Teflon (I've got a sheet about 1 foot square, half inch thick) one pair of strips for each end of the batteries, with one of the strips in each pair cut to hold the batteries. Two batteries being side by side with spring loaded guide rods keeping the strips straight. That way there would be constant tension from the springs, but some give so that battery expansion would not be an issue.


At the very lease you should find my diagram humorous!


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## Mr Happy (Feb 21, 2010)

Russel said:


> At the very least you should find my diagram humorous!


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## Apollo Cree (Feb 21, 2010)

A piece of rubber from a bungee cord between the copper strip and clamp jaw might also help. 

It might be worthwhile to take a nail or punch from the backside and make some bumps on the battery side of the contacts for better contact with lower pressure. 

The big thing would probably be for anyone who builds such a clamp to realize that you can easily damage the battery if you don't carefully clamp it gently. Be sure no one else like the kid or wife is going to decide to cinch it down for you. 

It IS a neat idea.


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## Mr Happy (Feb 21, 2010)

I'm gonna mention again that magnets are a seriously underrated technology when it comes to attaching wires to cells. Look up your local craft jeweler and see if you can obtain some thin silver foil. Silver wire would be easy, but silver foil may be possible. It would be perfect with a small neodymium magnet glued to the back.


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## tsmccull (Feb 21, 2010)

Silver foil will eventually tarnish (that's why the wife haul's out the silver polish before a fancy dinner party). The right size & shape gold-plated electrical contact that would work would be a better long term choice.


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## Mr Happy (Feb 21, 2010)

tsmccull said:


> Silver foil will eventually tarnish...


I'm gonna mention again that magnets are a seriously underrated technology when it comes to attaching wires to cells. Look up your local craft jeweler and see if you can obtain some thin 24k gold foil. Gold wire would be easy, but gold foil may be possible. It would be perfect with a small neodymium magnet glued to the back.


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## Russel (Feb 21, 2010)

Here is a slightly better diagram of the Teflon parts for the 2 D cell holder I posted earlier.






I figure that the cutouts to hold the D cells don't really need to be a half inch deep. That would allow me to place half inch diameter contacts with the wiring going in a groove cut into the back piece.

I'm not ruling out a method using magnets yet, I'm just exploring this idea to see where I can take it.

Note: I made this diagram with Google SketchUp. I'm just a SketchUp novice, but it surprised me how easy this diagram was to make. The best part is that it is free! Of course, there is a pro version that you can pay for if you want.


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## Skinnysloth (Mar 4, 2010)

From the ideas posted in this thread I came up with this solution:





I'm using AAA to AA adapter to hold my end terminals in place. I took some 12 gauge speaker wires I had, crimped the end terminals and attached them to the batteries with magnets. The end terminals are sandwiched between two magnets and it held them pretty well.


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## scot (Mar 6, 2010)

Hey skinneysloth, have you done any breakin or discharges with the pictured cells? Just curious how good this setup works.


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## Skinnysloth (Mar 6, 2010)

scot said:


> Hey skinneysloth, have you done any breakin or discharges with the pictured cells? Just curious how good this setup works.



Indeed I have. I've used it to break in two AccuEvolution LSD C and D cells.

With the C cells rated at 4500 mAh the break in capacities were:
1. 4704 mAh
2. 4776 mAh

D cells rated at 10000 mAh:
1. 9417 mAh
2. 9343 mAh

These results are in the same ball park as the OP's findings.

With a similar setup on my hobby charger (no dummy cells were needed), I was able to use a charge rate of 5A and discharge rate of 1.5A (probably the limit of the hobby charger) on the D cells. On the Maha c9000, it was able to handle the discharge rate of 1A on the D cells with no problem.


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## dex138 (May 5, 2010)

Hi Russel.
Nice clean setup you got there. Where did you source your materials?



Russel said:


> I made this adapter a while back for performing break-in, and testing capacity, on D cells with a MH-C9000.
> 
> (I apologise for the poor angle. The display is a little hard to read.)
> 
> ...


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## Russel (May 6, 2010)

I purchased the brass, steel, teflon, and copper from onlinemetals.com everything else is from material I had laying around.

I've updated the D cell holder. The contacts are copper with the negative contact protruding and the positive contact recessed.


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## dex138 (May 6, 2010)

OK, then from that I must conclude that you made all the components yourself, from the raw materials?

Heh, now thats what I call a sweet holder! Did you make one for 'C's too? hmmm......prolly not I'm guessing, this one looks like it could do both.


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## Russel (May 6, 2010)

Yes, I machined the parts myself with a Sherline lathe and mill.

I only made this one battery holder for D sized cells, but it seems to hold C cells well enough also.


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## Black Rose (May 6, 2010)

Nice work Russel :thumbsup:


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## TakeTheActive (May 6, 2010)

Russel said:


> Yes, *I machined the parts myself* with a Sherline lathe and mill...


 :green: :bow: :goodjob: :santa: 
(TTA being cryptic)


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## ptewee (Jun 25, 2010)

has anyone tried doing this with 9v cells? apparently, i need to charge 9Vs more than Cs or Ds... :tired:


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## daf3m (Jun 26, 2010)

ptewee said:


> has anyone tried doing this with 9v cells? apparently, i need to charge 9Vs more than Cs or Ds... :tired:



9volt batteries need 9 volt chargers..:candle:


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## Black Rose (Jun 26, 2010)

9V cells could be done but because their capacity is so low (most are less than 200 mAh) and the lowest charge rate from the C9000 is 200 mA, you would be charging the cell at more than 1C.


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## TakeTheActive (Jun 27, 2010)

Black Rose said:


> *9V cells could be done*...


Well, kinda - if you OPEN up a 9VDC BATTERY to expose the connections to the individual 1.2VDC CELLS, you could attempt to charge it (@ 200mA minimum) as you stated. 

For me, 9VDC rechargeables have always been a PITA since it always seemed that ONE CELL would die rendering the battery useless (since it either started at a '_handicapped_' 8.4VDC or 7.2VDC anyway). Since my reading of the CPF 'Batteries Included' Archives, I've changed my '_strategy_' a bit - instead of running the device until it stops working  , I now keep a chart of 'When Installed' and *try* to recharge it earlier. I also pulled my old GE NiCD 12mA chargers out of retirement for my 2 Harbor Freight 100mAh NiCDs and 1 160mAh NiMH, going for the ~0.1C (or less) 'Self-Balancing' charge (compared to the 15mA Sears DieHard and the 23 mA RadioShack 23-428).

I recently lost 2 out of 5 DieHard 8.4VDC 150mAh NiMHs from 12/2000 with a "Green Crud" that ate through the negative terminal's rivet - something I don't recall seeing before. But, nonetheless, almost 10 years is a good run for a sealed battery. 1 out of 2 Varta 150mAh NiMHs from 01/2003 died over a year ago, which is disappointing - I was expecting better from Varta (which I thought was a good brand). That's another reason why I'm giving Harbor Freight a shot.


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## Face (Jun 29, 2010)

I would love to have a setup like this for charging C and D cells with my C9000. I can't be the only one.

Would anyone be interested in producing a kit if there was enough interest from other members?


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## Face (Jul 2, 2010)

Face said:


> I would love to have a setup like this for charging C and D cells with my C9000. I can't be the only one.
> 
> Would anyone be interested in producing a kit if there was enough interest from other members?



I guess not then. Shame as I would have thought something like this would have been a big boon to members of this forum.


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## Black Rose (Jul 2, 2010)

I think most folks that want to do this just throw something together for themselves like I did with the wires and magnets.

I plan on rebuilding the one I made with actual battery holders to make it more plug and play.
I just need to get hold of some Delrin rods to make the fake batteries.


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## samgab (Jul 3, 2011)

@ Russel ... Wow, that's impressive! I've just ordered a C9000, and ever since I've been mulling over ways to make it work with D cells... had a bit of a hunt around on this amazing forum  and whaddayaknow! People who came before me have already done it, and way better than I could hope to.


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## Russel (Jul 4, 2011)

There are a lot of ways to do it. Many people use the simple magnet method with a dummy AA cell. I went a little further, partly because I need to justify purchasing the Sherline mill and lathe that I have!


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## CyberCT (Feb 8, 2012)

Russel said:


> I purchased the brass, steel, teflon, and copper from onlinemetals.com everything else is from material I had laying around.
> 
> I've updated the D cell holder. The contacts are copper with the negative contact protruding and the positive contact recessed.



Russel, I'm very interested in doing a setup very similar to yours. I poked around at that metals site you mentioned but couldn't really find anythign familiar to what you used. If you have a minute could you maybe give me a link to each component on their site that you used for your setup? I'm probably going to end up buying those Accupower D LSD cells and I have a Maha MH-C9000 so I should be able to measure the mah values of them with the Maha. So I need to fabricate an adapter like waht you have


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## jayflash (Feb 9, 2012)

Yes, I'm also impressed with the high quality of these adapters and unless the quality is high it probably won't work well. No half way solutions for this.

I'd be interested in obtaining such a nice accessory, but doubt anyone would be willing to make them for an affordable price. I'm sure a lot of time was put into these. Unless they were mass produced and would actually sell in large enough quantities, they'll remain a wish.


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## CyberCT (Feb 9, 2012)

Just give me a link to all the parts and I will figure out how to fabricate some for myself.


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## Russel (Feb 9, 2012)

I don't remember the material sizes of the top of my head, but I'll look when I get home and post more info. Do you have a mill and or lathe?


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## CyberCT (Feb 9, 2012)

I have neither. However, if you can just provide a link to the white plastic "dummy" cell and the brass ends, I will be able to fabricate the rest myself.

I wonder if there is a place that sells good quality brass or copper springs. I have one of the original 2 D cell black battery holders (I got it from Radio Shack) and if I can get a better spring with less resistance I'll be good to go!

I also hear there are magnets people use. Do you know anything about those?


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## Russel (Feb 10, 2012)

CyberCT said:


> I have neither. However, if you can just provide a link to the white plastic "dummy" cell and the brass ends, I will be able to fabricate the rest myself.



I wish that I could, I'm sorry if I wasn't clearer in my earlier posts. I made the dummy cells from teflon rod. I drilled out the center, cut internal threads on the inside of both ends and milled the center opening where the wires come out. The brass ends were turned from solid brass rod, threaded, and center drilled with a lathe.



CyberCT said:


> I wonder if there is a place that sells good quality brass or copper springs. I have one of the original 2 D cell black battery holders (I got it from Radio Shack) and if I can get a better spring with less resistance I'll be good to go!



I don't think that brass or copper would work very well as springs, too soft. I don't know of any, but it may be possible with brass, it isn't quite as soft as copper. You might consider just using copper as the contact with a wire soldered directly to it on the end of a steel spring.


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## CyberCT (Feb 12, 2012)

Darn. I wonder where to get a teflon rod like that? Would me cutting a wooden dowel into pieces that's the width of an AA cell be a good idea instead? If you don't know where I could get a teflon rod like that?

I just got a great deal on Tenergy D 10,000 mah cells on ebay. THey are the model number 10100. Of the five modes of the MH-C9000, which is the best for D cells? And what did you put as the charge and discharge rates?


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## jalyst (Feb 12, 2012)

There's 5 "models" of C9000?

There might be slightly diff. firmware/hw floating around.
But I doubt there's notable differences between them.

Between the very oldest models & the most current one maybe.
But otherwise no....


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## CyberCT (Feb 12, 2012)

No, it's 5 "modes"


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## jalyst (Feb 12, 2012)

woops my bad, obviously need some sleep.


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## Russel (Feb 12, 2012)

CyberCT said:


> Darn. I wonder where to get a teflon rod like that? Would me cutting a wooden dowel into pieces that's the width of an AA cell be a good idea instead? If you don't know where I could get a teflon rod like that?



OnlineMetals has nylon rod, as well as many other plastic and metal materials. Both wood or plastic would work for making a dummy cell. 



CyberCT said:


> I just got a great deal on Tenergy D 10,000 mah cells on ebay. THey are the model number 10100. Of the five modes of the MH-C9000, which is the best for D cells? And what did you put as the charge and discharge rates?



For normal charging of 10000mAh NiMH cells, I use a MH-C808M charger at it's default rate of 2 amps. I do however use the MH-C9000 to run the D cells on a break in cycle once a year. I set the break-in capacity to 10000mAh. 

Unless you have one of the original MH-C9000 chargers, it won't fully charge a 10000mAh cell in one cycle. The break in mode does work with large capacities, but I think the other charging modes are limited to something like 4500 to 5000mAh. (The charge capacity max. is in this thread somewhere) To charge large capacity D cells with the C9000 you could always set a 2000mA charge rate, then when the charger stops due to it's programmed maximum charge capacity, simply start another charge cycle and it should completely charge the D cell, assuming the cell was completely depleted. Of course, if the cell needs less than say 4000mAh to fully charge it, one charge cycle will do the trick.


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## CyberCT (Feb 12, 2012)

I have 20 gage sleeved solid copper wire. Is this good enough wire to use for my adapter setup I will make to charge and test my Tenergy D cells in the MH-C9000?


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## CyberCT (Feb 12, 2012)

Russel said:


> OnlineMetals has nylon rod, as well as many other plastic and metal materials. Both wood or plastic would work for making a dummy cell.
> For normal charging of 10000mAh NiMH cells, I use a MH-C808M charger at it's default rate of 2 amps. I do however use the MH-C9000 to run the D cells on a break in cycle once a year. I set the break-in capacity to 10000mAh.
> 
> Unless you have one of the original MH-C9000 chargers, it won't fully charge a 10000mAh cell in one cycle. The break in mode does work with large capacities, but I think the other charging modes are limited to something like 4500 to 5000mAh. (The charge capacity max. is in this thread somewhere) To charge large capacity D cells with the C9000 you could always set a 2000mA charge rate, then when the charger stops due to it's programmed maximum charge capacity, simply start another charge cycle and it should completely charge the D cell, assuming the cell was completely depleted. Of course, if the cell needs less than say 4000mAh to fully charge it, one charge cycle will do the trick.



Do you know what size specifically of the nylon rod for me to buy for my adapters?

If I do a discharge at the maximum capability of the MH-C9000 (what is it, 3,000 mah?) and then just charge it in the MH-C808M wouldn't that be fine? That should tell me the mah capacity of each, correct? My main goal is to make sure none of my D cells are bad, and to do cell matching. After doing MANY tests of my specific MH-C9000 I have found the four bays are skewed with thier readouts. From highest to lowest readouts of battery mah capacity, it goes Bay 1, 2, 4, 3. And I have the percentage difference so I will apply that when I record the data using my D cells in the MH-C9000 charger. 

I wonder why Tenergy recommends charging their D cells at 1,000 mah instead of anything higher?


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## Schermann (Oct 3, 2013)

C & D adaptors are now made by Maha for the C9000!







Go get 'em...


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## jalyst (Oct 3, 2013)

.......


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## jalyst (Oct 3, 2013)

Schermann said:


> C & D adaptors are now made by Maha for the C9000!
> Go get 'em...



The one time I actually liked a neco-poster, thank-you sir.




I can't say I use C/D cells very much at all, but, it's still handy to have the adapters.
Think I'm well overdue to update the whole unit actually, unless it hasn't changed at all in the last 2yr?

P.S. You got any actual links to these adapters?


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## Rexlion (Oct 3, 2013)

AFAIK Maha does not make adapters like these. I got mine from an ebay seller called 'rdana'. I believe they're made by a company that also makes the BM200 charger. This charger has some interesting functions, but I prefer to stick with the Maha. The adapters fit in either one... but I did have to shave a tiny bit of plastic off the Maha, just above the positive contacts, for the adapters to work properly.


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## jalyst (Oct 3, 2013)

Thanks I'll search for that eBay seller. Is the C9000 still considered the best all-round charger out there nowadays?
Has it had some major revamps in the last few yrs, wondering if I should sell mine & get the latest revision.


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## samgab (Oct 3, 2013)

jalyst said:


> ...Is the C9000 still considered the best all-round charger out there nowadays?
> Has it had some major revamps in the last few yrs, wondering if I should sell mine & get the latest revision.



Have you seen the SkyRC NC2500?

The C9000 hasn't been revamped in any way recently that I've heard of, but the NC2500 is a bit like a revamped updated C9000 with a few new tricks, eg graphs and control via bluetooth to iPhones/smartphones.


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## Almighty1 (Jan 18, 2014)

Schermann said:


> C & D adaptors are now made by Maha for the C9000!



Anyone know if these works with the skyrc NC2500?


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## braddy (Jan 18, 2014)

Schermann said:


> C & D adaptors are now made by Maha for the C9000!
> 
> 
> 
> ...



Where?


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## Turbo DV8 (Feb 10, 2014)

Search eBay for seller "rdana." He sells two for $9.95, free ship. However, he states in red that although these will fit the C9000, "...Measurements are unreliable in discharge mode. Therefore, capacity testing is unreliable in some C9000 chargers. The adapters are not guaranteed to work in the C9000." 

I bet it's right back to the same old problem ... contact issues.


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