Homemade Battery Packs

Batteries, Chargers, and Battery Management Systems.
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Hwy89   1 kW

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Re: Homemade Battery Packs

Post by Hwy89 » Sep 25 2013 2:56pm

[quote]cwah wrote: What's the cheapest (hard) battery enclosure material? I'm currently using wood but it's too thick[quote]
I don't know if it is available where you are, but square pvc fence posts make good battery cases. The one I used measured 5 1/2 inches square and the cross section nicely fit 36 ea. 18650 cells (6X6). I cut it to about 11 1/2" long and put in 144 cells (12s 12p) and closed the ends with matching post caps.
In looking at the photo of your bike, it doesn't appear that you would have space for one as large as mine but if you play around with the cell configuration you might find a workable plan.
Here in the States the pvc fencing parts are available at the Home Depot stores.

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Re: Homemade Battery Packs

Post by Hwy89 » Sep 25 2013 3:43pm

I got tired of buying used laptop batteries on ebay. I bought a lot of crap before I finally accumulated enough good matched cells to build two batteries for our bikes. When I spotted an auction for a lot of 444 new, two cell, 7.4 V packs I couldn't stop myself from buying them. I took 96 of them apart and built a great 12s 16p pack that gives me over 100 miles of range.

My efforts to re-sell the remaining packs failed so I have been finding uses for them for LED lights and repowering a battery drill. I'm thinking about using 100 of them to put together a 4s 50p, 14.8V storage battery that would run my RC charger and could also be used for camping and possibly run my trolling motor.
Each of the two cell packs has a bms that blocks charging at 8.4 volts and interupts the output when they drop to 6.6 volts.

What would happen If I built a large pack without disassembling them and left the bms board in place? My thought is that it should work, but I would like to hear what others say before I try it. I may run a test with four packs in series parallel and monitor it just to see.

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DrkAngel   10 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Sep 25 2013 3:56pm

Hwy89 wrote: I spotted an auction for a lot of 444 new, two cell, 7.4 V packs I couldn't stop myself from buying them. I took 96 of them apart and built a great 12s 16p pack that gives me over 100 miles of range.

What would happen If I built a large pack without disassembling them and left the bms board in place?
Likely, the cells were for a modest drain device?
If so, discharge rate would be very limited by the BMS.
Great for low drain devices, CFL (Compact Fluorescent Light Bulbs) lanterns, radios etc.
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cwah   10 GW

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Re: Homemade Battery Packs

Post by cwah » Sep 25 2013 3:59pm

That's a good idea!!

The closest I've found is this one:
http://www.polydis.fr/epages/8d7c81fe-5 ... .sf/fr_FR/?

Or this one but a top part is missing:
http://www.leroymerlin.fr/v3/p/produits ... et&xtcr=24

This guy seem to have pvc sheets at excellent price:
http://cgi.ebay.fr/ws/eBayISAPI.dll?Vie ... TQ:FR:1123

But it looks like it might be pvc foam
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: Homemade Battery Packs

Post by etriker » Sep 25 2013 4:17pm

DrkAngel wrote:
Hwy89 wrote: I spotted an auction for a lot of 444 new, two cell, 7.4 V packs I couldn't stop myself from buying them. I took 96 of them apart and built a great 12s 16p pack that gives me over 100 miles of range.

What would happen If I built a large pack without disassembling them and left the bms board in place?
Likely, the cells were for a modest drain device?
If so, discharge rate would be very limited by the BMS.
Great for low drain devices, CFL (Compact Fluorescent Light Bulbs) lanterns, radios etc.


If you just wanted to use the bms to balance and not use it to limit current it might balance the cells.

Hook the + and - battery output right on the cells and not run it through the bms.

Sounds like an interesting test.

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Re: Homemade Battery Packs

Post by cwah » Sep 25 2013 4:28pm

Hwy89 wrote:I got tired of buying used laptop batteries on ebay. I bought a lot of crap before I finally accumulated enough good matched cells to build two batteries for our bikes. When I spotted an auction for a lot of 444 new, two cell, 7.4 V packs I couldn't stop myself from buying them. I took 96 of them apart and built a great 12s 16p pack that gives me over 100 miles of range.

My efforts to re-sell the remaining packs failed so I have been finding uses for them for LED lights and repowering a battery drill. I'm thinking about using 100 of them to put together a 4s 50p, 14.8V storage battery that would run my RC charger and could also be used for camping and possibly run my trolling motor.
Each of the two cell packs has a bms that blocks charging at 8.4 volts and interupts the output when they drop to 6.6 volts.

What would happen If I built a large pack without disassembling them and left the bms board in place? My thought is that it should work, but I would like to hear what others say before I try it. I may run a test with four packs in series parallel and monitor it just to see.
Batteries are quite expensive, and reselling them for ebike with good price tag should be easy isn't it?
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Hwy89   1 kW

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Re: Homemade Battery Packs

Post by Hwy89 » Sep 25 2013 4:37pm

Likely, the cells were for a modest drain device? If so, discharge rate would be very limited by the BMS.
That's a good point DrkAngel. I will set up a test and gradually increase the current to see if the bms limits it or if at some point it just smokes the board. I won't go over 2.2A which would be 1C for these cells.
Even if the bms cuts them off at .5C my 50p pack would provide 55 amps which should be enough.
The battery packs were made to power hand held CO2 detectors but the company went bankrupt before they were put on the market.

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Hwy89   1 kW

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Re: Homemade Battery Packs

Post by Hwy89 » Sep 25 2013 4:45pm

Cwah, try this link or just google vinyl fence post.
http://www.homedepot.com/webapp/wcs/sto ... earchAll[b][/b

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Re: Homemade Battery Packs

Post by cwah » Sep 25 2013 5:05pm

Yes I've seen that. But they are all sold in US.

The closest equivalent in france is quite expensive:
http://www.polydis.fr/epages/8d7c81fe-5 ... oteaux_PVC
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: Homemade Battery Packs

Post by Hwy89 » Sep 25 2013 5:34pm

Cwah, if you can find someone who has that fence they will probably have some broken pieces to give away. I worked at a horse ranch where we were constantly repairing and replacing parts of the plastic fence. The stuff is pretty but it doesn't stand up to being used as a rubbing post for 1000 pound hay burners. I think the UV from Arizona sunshine makes it more brittle.

cwah   10 GW

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Re: Homemade Battery Packs

Post by cwah » Sep 25 2013 5:53pm

Yeah but I live in paris so not many people have fence lol

What about this?
http://cgi.ebay.fr/ws/eBayISAPI.dll?Vie ... TQ:FR:1123
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: Homemade Battery Packs

Post by Hwy89 » Sep 25 2013 6:25pm

[quote] Yeah but I live in paris so not many people have fence lol[quote]

It's a different world from rural Arizona

My eighth grade French is long forgotten but I assume those are pvc sheets. You can bend pvc with a home made heater using wooden blocks and a clamp. I took the quartz tube heating element from a scrap toaster oven and mounted it on a metal base. Hold the pvc over the heat until it slumps then position it between the wood blocks and clamp till it cools. Use pvc primer and cement to put it together.

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Re: Homemade Battery Packs

Post by cwah » Sep 25 2013 6:46pm

Can I use any pvc cement? This one for exemple?
http://www.ebay.co.uk/itm/118ML-BLACK-S ... 45f4f6c7f2
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: Homemade Battery Packs

Post by Hwy89 » Sep 25 2013 6:59pm

cwah wrote:Can I use any pvc cement? This one for exemple?
http://www.ebay.co.uk/itm/118ML-BLACK-S ... 45f4f6c7f2
I'm not familiar with that brand but yes it should work. You should also find primer to clean the surface before you apply the cement. Make sure you have everything lined up and some kind of clamp ready because the cement works very fast. Practice on some scrap material first.

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Re: Homemade Battery Packs

Post by cwah » Sep 25 2013 7:56pm

thanks. I'll get some primer, the glue and the sheets then :)
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: Homemade Battery Packs

Post by cwah » Sep 26 2013 4:41am

Seller just told me it's PVC FOAM. He said it's 5mm thick so it's quite strong and rigid. Able to handle 50kg weight without breaking.

I'm a bit dubious because it's still foam... But he has good price at 3.5USD for an A2 sheet.

Can I use it for battery box?
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: Homemade Battery Packs

Post by DrkAngel » Sep 26 2013 7:21am

cwah wrote:Seller just told me it's PVC FOAM. He said it's 5mm thick so it's quite strong and rigid. Able to handle 50kg weight without breaking.

I'm a bit dubious because it's still foam... But he has good price at 3.5USD for an A2 sheet.

Can I use it for battery box?
See - "Forming" Custom Sized Battery Cases
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Re: Homemade Battery Packs

Post by nukezero » Sep 30 2013 2:07pm

Hi there, can someone help me a bit about this battery I bought? It is a 36V 10.4Ah pack with BMS.

I bought these batteries on eBay and they seemed like a nice pack, although a bit expensive. At $6-7/ea. I figured the pack, along with the BMS, 42V smart charger, plus assembly was worth the price I paid.

It turns out these are Samsung "pink" ICR 18650-26F cells. Can anyone tell me the following:

1. What is the chemistry? NCM ?
2. Are these what everyone uses now when they talk about Samsung's new NCM cylindrical cell?
3. Why are these cells given pink colors? What is the difference between these pink colors and other colors?
4. Should I have bought Sanyo cells?

I went to samsung's website but could not find much details about this cell. Only that the remark says NCM/LCO. But what does LCO mean?

thanks
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DrkAngel   10 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Sep 30 2013 2:32pm

NCM/LCO = Nickel-cobalt manganese /Li-cobalt.
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Optimal Charge Voltages

Post by DrkAngel » Oct 06 2013 11:44am

Moved to it's own topic - Determining Optimal Charge Voltage

Important highlights:

A Picture is worth a thousand words ... so ...

Image

Image

Image

Image
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Homemade Battery Packs

Post by powersupply » Oct 06 2013 5:02pm

Very informative, DrkAngel.

Does such a thing exist for LiPo, too?

I.e. do LiPo exhibit similar float/charge voltage vs cycles?

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DrkAngel   10 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Oct 06 2013 6:47pm

To a great degree, the Li-ion described are the standard Lithium Cobalt based cells.
Li-ion 18650 cells are basically the same lithium cobalt formulation as the standard "LiPo" and in many respects and to a great degree are very comparable.
A little learning is a dangerous thing;
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There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Homemade Battery Packs

Post by powersupply » Oct 06 2013 7:59pm

Cool, thanks DrkAngel.
How reliable do you think is the info from batteryuniversity?

I overbought batteries (4p) and was thinking of saving some (3p+1p spare).
But with this info, I'd rather use them all and just charge them less.

Will have to program the BMS accordingly.

Thanks!

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Re: Homemade Battery Packs

Post by DrkAngel » Oct 07 2013 7:07am

BatteryUniversity.com has been a reliable reference for many many years.
I have never found any site more dedicated to the sole purpose of freely, and without self-serving agenda, providing battery information.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

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DrkAngel   10 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Oct 08 2013 9:26am

Latest cell testing methodology

Before building packs I do thoroughly test and evaluate every cell.
I have developed and refined simple and effective procedures ...

Step 1
I bulk charge all cells to just above working voltage, then I allow cells to set several days and remove any with bleed down.

Step 2
Then I "Bulk" capacity test all cells - Method 2 preferred.

Step 3
Any unfamiliar brand, I choose a good sample and run a Charge Capacity Test to build a capacity map.
This test is performed by discharging cells to maximum DOD, then charging in 2/100th V increments, recording mAh required for each step. This gives an accurate map of each portion of capacity added at each fraction of a volt.

Previously, I have built capacity maps based on Discharge - mAh /100th V.
While interesting, the discharge map was flawed due to voltage sag and IR.

Step 4
Finally, I Match up the best cells for pack build. Equal total mAh per bank works nicely.

So far, and preferably, each pack is constructed from cells of same brand and oem rated capacity and results have been excellent.

I've been building eBike battery packs from recycled laptop cells for 6+ years and am continually finding-developing better methods.
The thread Homemade Battery Packs is a reasonably complete documentation of my progress.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

Index - Homemade Battery Packs - Updated - November 2018

EBike Toolbox - Bargains! $

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