Maha MH C808M Charger

[Quickbeam]

I purchased the C808m a few weeks ago, and it seems to do a great job.

Doug P.

 

[europium]

...

Looking at these numbers, it seems that even if you leave the cells on the charger, the AA and C/D cells would still self discharge faster than the charger could trickle charge them. In light of this, I still believe it is better to develop a habit of charging your cells before use. You will usually have enough left in the cell to be able to use them even if they have been sitting for a month or two or maybe even three. If you don't use them within a couple of months, you will be better served with primary cells.

Tom

Is this also true for eneloop NiMH batteries? That the trickle charge will be less than the self-discharge rate and thus be insufficient to keep the AA and larger size cells fully charged when left on the charger?

P.S.--Many kudos to you Silverfox for all your work and data and reviews.

 

[SilverFox]

Hello Europium,

Sorry, I missed this question until now...

First of all, I don't recommend leaving batteries on a charger for any length of time. After about a day, the cells should be fully charged and removed from the charger.

Next, the response you quoted was a reply to Flash about the Ansmann Energy 16 charger and not the Maha C808M charger. I believe the Maha charger "trickle" rates are lower.

One test I have not done is to leave a cell on the C808M charger for an extended period of time. It could be that when the self discharge of the cell dropped below a certain voltage, the charge process would begin again. This might prove to be an interesting way to maintain cells, but I still don't like leaving them on the charger for extended periods of time.

Finally, the Eneloop cells have such a small self discharge rate it just doesn't make sense to leave them on the charger all the time. I believe the Eneloop cells have to be dormant to minimize the self discharge rate. Constant trickle charging may adversely effect this process, but I am not familiar enough with the chemistry to know for sure.

At any rate, it is possible that you could overcharge and dry out the electrolyte in the Eneloop cells by constant trickle charging, even at very low trickle charging rates.

Tom

 

[hank]

Cross reference this thread:
Maha MH-C800S 8 bay charger
https://www.candlepowerforums.com/threads/137843

 

[Phlack]

I have some D batteries which are slightly longer than they probably should be, causing problems in some devices. The top "botton" isn't very long compared to its base, causing problems with charging (in the accumanager20), as well as some devices that have their + terminal connection slightly recessed compared to its surroundings.

As suggested in a previous thread I posted, I got some small rare earth magnets, and they solve the problem of the connection. But not the length.

The C808M (and the D also, I suppose) sound like the + terminals are also recessed. On top of this, it doesn't sound like there's a lot of play as far as how much room there is. (The accumanager20 is spring-loaded, and there's plenty of room for the slightly-long D battery).

Are the batteries (especially D's) tight fitting as it is, or can it accomodate a battery that's maybe a few millimeters longer?

-Mike

 

[BrianChan]

Silverfox,

Hello Ben,

I just pulled 8 cells off of the charger. Most of them were at 1.44 volts. The lowest was 1.43 volts, and the highest was 1.46 volts.

Your cells at 1.39 and 1.40 volts do not seem to be fully charged.

Tom

I understand that Ben is measuring AA cells when he got 1.39-1.40v. However I get the same voltage on the 6 Maha Powerex 11000 mAh D cells hot off the charger. Another thing I have noticed is the battery icon behaves a bit differently for the D cells I have.


For example:

Charging AA and AAA cells:

'empty battery icon' > 1bar > 2 bars > 3 bars > "Done"

Charging D cells:

'empty battery icon' > 1bar > 2 bars > "Done"

In addition to that the batteries are much warmer compared to AA cells.

Any idea what's happening?

 

[wooniris]

Hi William,

Bought a Maha MH C808M about 3 weeks ago. Has been use intermitantly. Today, after the power-up diagnostics, the no:8 rightmost slot remains light up with a empty battery icon, eventhough there is no battery inserted. On insertina a bateery in the leftmost slot no: 1, the no 8 slot changes to charging even though no battery is inserted. This happens throught all the modes, slow, fast, condtioning etc. What's wrong with the charger?

Thanks

Woon

 

[etc]

Just reading this thread makes me think that charger is too smart for me.

 

[wooniris]

Dear William,

Thanks for the quick PM. Excellent support. Will do as suggested. Thanks

Woon

 

[SilverFox]

Hello Mike,

The 808M has some space for slightly longer D cells, but the spring is very tight. The spring set up with the AccuManager will probably work easier.

Tom

 

[SilverFox]

Hello Brian,

My D cells come off at 1.45 volts. Perhaps you need to do a few cycles on your cells...

I have never watched the charging bars. I will have to see if I can spend some time watching them.

Tom

 

[meditator]

Dear Folks,
Any ideas who has the best prices on the Maha MH-C808M ? Is Thomas Dist. the current best try?...Patrick

 

[Alin10123]

Hi Silverfox. Thanks for this review.
Is there anything specifically that this maha charger can do that the accupower 20 can't do? I know it can charge 4 more cells at the same time. But it's also double the price.
I'm Trying to justify the cost. I will be charging anything from AAA cells to D cells.

Thanks

 

[SilverFox]

Hello Alin,

NiMh battery manufacturers recommend charging at a rate of 0.5 - 1.0C when using -dV termination to insure a strong end of charge signal. I believe both chargers use -dV to terminate the charge.

With that in mind, the AccuPower20 charges at 700 mA, and the C808M charges at 2000 mA or if you select, 1000 mA. The AccuPower20 only charges, and is supposed to have a charging algorithm that prevents large crystal build up (voltage depression). The C808M has a condition mode that fully discharges the cells, then charges them back up. The full discharge method is the recommended method, but I have not heard any complaints from people using the AccuPower20.

I have heard nothing but good things about both chargers.

The AccuPower20 has the advantage of smaller size, is able to operate on 12 volts, it has the ability to charge 9 volt batteries, and costs less.

The C808M has the advantage of being able to charge more cells at a time, it offers 2 charging rates of which both are higher than the AccuPower20, charging high capacity cells is faster because of the higher charge rate, and it has the ability to discharge cells in the conditioning cycle.

Tough choice... perhaps you should get both.

Tom

 

[eav2k]

My third Maha MH C808M charger just died. The first lasted about two months, the second about a month, and the third about 3 months. They all died the same way, after trying to condition AAA cells. I got this charger from Thomas Distributing; who have the best customer service I have every encountered. I would be willing to try a forth C808M, but if I do get one I will not try to condition AAA cells with it. Has anyone else encountered this problem? Note that prior to these failures the chargers worked great.

 

[Jeff_Bagley]

I've had two 808's fail while charging AAA's. Both Thomas Distributing and Maha have been helpful. My third unit has been running for about a week now, charging AAA's and AA's with no problem. I really hope this one lasts.

 

[Alin10123]

hmm, this may be a problem as i will also be wanting to charge AAA cells with it.

 

[iocheretyanny]

My third Maha MH C808M charger just died. The first lasted about two months, the second about a month, and the third about 3 months. They all died the same way, after trying to condition AAA cells. I got this charger from Thomas Distributing; who have the best customer service I have every encountered. I would be willing to try a forth C808M, but if I do get one I will not try to condition AAA cells with it. Has anyone else encountered this problem? Note that prior to these failures the chargers worked great.

How do they fail?

 

[Sub_Umbra]

...The AccuPower20 has the advantage of smaller size, is able to operate on 12 volts, it has the ability to charge 9 volt batteries, and costs less.

The C808M has the advantage of being able to charge more cells at a time, it offers 2 charging rates of which both are higher than the AccuPower20, charging high capacity cells is faster because of the higher charge rate, and it has the ability to discharge cells in the conditioning cycle.

Tough choice... perhaps you should get both.

Tom

Those two chargers complement each other very well. I have both of them and together they are the best of both worlds.

The AP2020 is gentle...but may require ~36 hours to charge 10,000 mAH NiMH D cells. It may seem worse in real world situations. Since the AP2020 has only four bays it will take around three whole days to charge a 6 D NiMH set for my CD boombox. The C808M makes short work of them. It's kinda breathtaking...

All of my AAAs get charged in the AP2020. I still use some 1,000 mAH AA NiCads and I prefer to only charge them in the AccuPower since the C808M will revert to it's default 2A charge rate if it's power is interupted for even a half second.

The C808M is so fast that I may charge over 120 NiCad and NiMH cells while a hurricane approaches by using both chargers. (I use, rotate and maintain all of those cells on an ongoing basis.)

For me, I wouldn't want to be without either of them. I still hope to run the AP2020 on solar eventually.

 

[Alin10123]

Those two chargers complement each other very well. I have both of them and together they are the best of both worlds.

The AP2020 is gentle...but may require ~36 hours to charge 10,000 mAH NiMH D cells. It may seem worse in real world situations. Since the AP2020 has only four bays it will take around three whole days to charge a 6 D NiMH set for my CD boombox. The C808M makes short work of them. It's kinda breathtaking...

All of my AAAs get charged in the AP2020. I still use some 1,000 mAH AA NiCads and I prefer to only charge them in the AccuPower since the C808M will revert to it's default 2A charge rate if it's power is interupted for even a half second.

The C808M is so fast that I may charge over 120 NiCad and NiMH cells while a hurricane approaches by using both chargers. (I use, rotate and maintain all of those cells on an ongoing basis.)

For me, I wouldn't want to be without either of them. I still hope to run the AP2020 on solar eventually.

:scowl:

This isn't making it easier. LOL