Another DR MR11 HID upgrade

[Packhorse]

Rebuild with Li Ion. Its probably cheaper...until you factor in the new charger. But since you need a new charger anyway still cheaper.

 

[Bill D]

Packhorse...I am sure you are right. I might as well upgrade to Li-Ion since both my batteries and charger have died. My local Battery and Bulbs store let me borrow their charger just to see what my batteries would do. Well they didn't do much at all. So I will price a battery pack from the local store and compare it to batteryspace.com. It appears it would be cheaper to order the batteries (18650) with tabs and then solder them. It looks like I could put three in series and four in parallel. Oh, I would also need to two pcb and two polyswitches. Since I am new to this I will see what the local store can do but then again it sure would be a great way to learn some new information by building the battery pack myself.

 

[Packhorse]

Packhorse...I am sure you are right. .....

Of course!!

Switching to Li Ion may cost a little to start with, but buy a BC6 charger( or knock off) helps ease the pain. I dont use poly switches in my Li Ion packs.


I have used 26650's from Batteryspace which performed really well for a couple of years ( having issues at the mo but have not daignosed the problem) and Trustfire 18650's which perform well for cheap cells and also sanyo 18650's more recently. I prefer the sanyos as they are available tab welded, Some ultrafires are too but they are labled at 4000ma but only 1500ma in reality.\

 

[Bill D]

Packhorse are you recommending the BC6 because you are not using pcb's in you builds and this charger acts as the pcb? If so then if I decided to use PCB's then I could go with a cheaper charger? Seems buying the fancier charger upfront may be a betterr option if I understand how these items work.

Thanks

 

[Packhorse]

Not all PCB's allow for balance charging, so in that case you need a balance charger.
The BC6 clone chargers are pretty cheap and very versitile. They charge all sorts of chemistries.

 

[Bill D]

Ok the Holidays are over so now I can refocus on the task of rebuilding my light. I am still waiting on the lens and drivers to arrive. I believe the driver may have arrived but dropped off at my neighbors home. I will check with them tonight.

Here is my order list from batteryspace.com. Please make suggestions or recommendations about these items.

Batteries are 18650's with tabs. http://www.batteryspace.com/ultra-h...lindrical-rechargeable-cell-3.7v-2800mah.aspx My plan is to do three in series and 5 in parallel for a total of 14.8 volts.
PCB http://www.batteryspace.com/pcbfor148vli-ionbatterypack5alimitwithfuelguagesocket.aspx
Connector for PCB will be to match what the balance charger has.

 

[Packhorse]

It looks like those cells are 4.35v max. To get the full 2800mah you will need a charger that will charge to 4.35volt. Most LI Ion chargers ( and cells) are 4.2volt. You can still use a 4.2v charger but you will not get full capacity.
Oh, and 3 series at 4.35v is 13.05volt, not 14.8v. That would be 4 cells in series at Nominal voltage. The PCB you linked to is for 4S.

 

[Bill D]

I was only looking at nominal voltage of 3.7v. Since you pointed it out I now see the 2600 batteries are 4.2v which I would be able to get a full charge using the battery charger you stated earlier. The way I came up the 14.8 was by using 3.7v per battery with three in series, plus 5 in parallel. Looked like this (Parallel 3.7 x 5) [email protected] (series 3.7 x 3)= [email protected] for a grand total of 15.6ah and 14.8v when tied together. What am I doing wrong?

 

[DIWdiver]

You don't add the series and parallel voltages. You don't add the series and parallel currents. You simply multiply the voltage times the series number, and the capacity times the parallel number.

You have 5 in parallel, so the amp-hours is multiplied by 5. The cell you linked to is 2.8A-h, so the pack capacity will be 2.8*5 = 14 A-h.

The nominal voltage is 3.7V, and you have 3 in series so the pack voltage is 3.7*3 = 11.1V.

So a 3S5P pack of these cells will be 11.1V @ 14A-h. This gives you about 155 Watt-hours.

Of course these are 'nominal' values. The off-charger voltage will be 4.2V * 3 = 12.5V. The "discharged" voltage will be 2.7V * 3 = 8.1V. Your voltages will vary depending on your charger, your protection circuits, and your preferences as to when you consider the batteries "discharged". Your capacities will vary with charge and discharge voltages, cell selection, and the way you treat the pack.

 

[Bill D]

Now I think I understand. How about if I do 4S4P which should be 14.8v @ 10.4AH. This would be using the 18650 2600ah 3.7 min and 4.2 max . Now in this case the PCB I had linked should work or is there something else I need to consider? The charger I was going with is what Pack Horse recommended.

Also the neighbor had the drivers I had order so now I just need batteries, battery charger, pcb and the lens.

 

[Bill D]

I might as well ask about this charger while I am at it. http://www.hobbyking.com/hobbyking/store/__5548__IMAX_B6_Charger_Discharger_1_6_Cells_GENUINE_.html

 

[Bill D]

I think I may have finally grasp what y'all have been saying about putting batteries in series and parallel and about picking the right pcb. It took some reading, visual aids, calculator, data sheets and scratch paper but I think I am making some progress. Talk about a slow learner...good grief.


Again thanks for the guidance!

 

[Bill D]

Please let me know if this makes any sense. I have looked at doing the battery pack(batteries 18650's, 2600, 3.7 nominal volts, 4.2 max and 2.5 max discharge) using either 14.8v pack (7.8AH) or a 11.1v (10.4)pack.

So if I use a 14.8v pack I would use 4s3p. I would need a total of twelve batteries which would provide 16.8 max voltage, 10 volts discharge. The pcb I would need would need to be able to handle 4s pack and need a PCB like this one http://www.batteryspace.com/pcbfor148vli-ionbatterypack10alimitwithfuelgaugesocket.aspx .

The 11.1 pack would be 3s4p. This would give me a total of 12.6 max voltage, 7.5 max discharge volts and I would use a PCB for 3s@7A max discharge.

Is that right? If that is right then does it matter if I use a 14.8 or 11.1v battery?

I would love to figure out the batteries so I can have them ready for when the lenses finally arrive.

 

[Packhorse]

Your choice of driver and the amount of LED's wired in series are probably the main considerations when deciding of what voltage battery pack to use. Some drivers are designed to work with a 2s pack and have a 6v low battery warning. While the driver may still work with a 3S pack it will not offer the same low battery warning.
Also if you were to run 4 LED's in series then a 3S battery pack will not offer enough voltage. Like wise a 4S pack may not offer enough voltage head room required by some buck drivers.

For what its worth, most of my can lights use 2S packs and I drive single LED's.

 

[Bill D]

For what its worth, most of my can lights use 2S packs and I drive single LED's.

That does help. I looked at the driver but didn't see any specs other than 2.5 - 3a. So the PCB will limit the max current from the battery to the driver at 3a and will shut off at 5a to prevent discharging the battery to low. This setup will also allow the alert function to work when voltage reaches 6.

 

[Bill D]

While still in a holding pattern waiting on my lenses and batteries, I tried my hand with making changes to the driver. I am glad I ordered two. The good news is I learned a couple of things so it wasn't a total waste.

Sent by using my Infected Nusense Thunderbolt

 

[Bill D]

My project is still moving forward. A friend of mine assisted me with making the heat skink and the lens spacer/holder. I will post some pictures tomorrow and with some luck know one will see any major mistakes.

 

[Bill D]

Here are two pictures.

The Delrin is 30mm. A lip was made on the inside for the lens to sit on. It is just 14.8mm deep. The heat sink is 13mm thick.
A question is how you conntect the delrin to the heat sink? I was thinking about srewing the delrin to the heat sink and placeing threaded holes so it was help in removing the whole thing down the road. The heat sink has a tight fit inside the light head.

 

[Bill D]

How do you wire the driver that was recommended? Do the wires that come preinstalled go to the emitter? I am also assuming the driver needs to connected to the heat sink? I really would like to finish this project so I can use my light for diving. Work has really prevented me from making any progress since my last post. Thanks

 

[DIWdiver]

The red and black wires on the driver go to + and - on the LED, respectively. Battery + goes to the big round flat spot on the back side. Battery - goes to the ring around the B+ pad.