Homemade Battery Packs

DrkAngel said:
Voltage sag seems excessive?
If your leads, or jumper wires, were less than 14ga, that might explain it.
12ga+ recommended, for 24Ah battery, on bike.

I am using 12ga speaker wire from a local building supply store. I would have bought 10ga but they don't have it. I could have ordered it online but everything takes a painfully long time (weeks) to get here and I did not want to wait. I live in Canada and it takes 3 weeks on average to receive a parcel from the U.S. :cry:

You are right about the voltage sag, I think the problem is that I welded the cells in a single long strip and I am connecting the load to the extremities. I am working on a different configuration to see if things gets better.
 
I wanted to say thank you to drkangel for sharing all this knowledge with us. I get it when people try to bash us for using these 18650 cells because it is not a high discharge cell. You know, most of us aren't speed junkies we just want to cruise from A to B. Thanks to you I grabbed the knowledge to build 2 large packs of 18650 2.6Ah cells. My pack is aprox ~30Ah 36V and costed ~150$. I use it in my commuter bike everyday and discharge to 3.2V under load which gives me 2 days before discharging it to maybe 75%. My kit is 36V 750watt and I cruise at around 20mph. When I feel like having a higher speed I just series connect a small 4.6Ah 5S A123 booster pack and call it a day. My off road build has 3 lipo packs inside the triangle(in series 6S) that gives me enough thrill for a couple of miles of off roading fun.
 
spuzzete said:
DrkAngel said:
Voltage sag seems excessive?
If your leads, or jumper wires, were less than 14ga, that might explain it.
12ga+ recommended, for 24Ah battery, on bike.

I am using 12ga speaker wire from a local building supply store. I would have bought 10ga but they don't have it. I could have ordered it online but everything takes a painfully long time (weeks) to get here and I did not want to wait. I live in Canada and it takes 3 weeks on average to receive a parcel from the U.S. :cry:

You are right about the voltage sag, I think the problem is that I welded the cells in a single long strip and I am connecting the load to the extremities. I am working on a different configuration to see if things gets better.
while you're inside the pack also note you can double-up (or triple-up or quadruple-up LOL) the 12ga wire you're using.
Two 12ga in parallel = about a 10ga
 
Thanks for the kudos guys.

My latest 18650 build - 25.9V 31.2Ah in an eZip pack is performing excellently!
After 1 year and 100++ cycles it still charges-discharges to, nearly perfect, equal voltages.
Either charged with with the 2A Tenergy or the 7+amp Meanwell clone, result are beautiful.
Last metered charge measured a 30Ah+ capacity!
Not bad for recycled "junk" cells?

Using, in conjunction with the recycled lipo builds of last year, I have neglected my original 4 year old 18650 Li-ion builds.
I have 3 - 37V 20.8Ah packs and 2 - 25.9V 31.2Ah, 408 cells in total.
After setting a year, I noticed that certain banks "bled down" and resist attaining full charge.

So, I shall rebuild!
1. Charge and balance all packs to 4.2V per cell
2. remove parallel balance wire from all cells
3. measure bleed down at 1 day, 1 week - remove "bad" cells (seems to be a good indicator of condition)
4. place drain on cells, measure "sag" - remove "bad" cells (indicates poor cells, or 1, of pair, bad )
5. replace "bad" cells
6. rewire with tinned copper braid and solid wire for balance

I might have to sacrifice-cannibalize 1 pack, but I have about 2 packs for each bike ...

They should look much "neater and professional" and be much sturdier.
 
DrkAngel said:
Voltage sag seems excessive?

I run a quick test today with the new configuration, on the same bat of the graph. after about 6 minutes the voltage was about 3.85+ on all three 3.6v 24ah packs :).You were right!

I can't thank you enough for opening this thread DrkAngel! I am so happy with my "homemade" battery pack!
 
Here is my submission for 18650 build. Took me a a couple tries with different ways to soldering.

306945_259110060785808_100000604484843_991297_4405855_n.jpg

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Almost accidentally, I discovered tinned copper braid.
It helped solve various problems, I found, from other wires, tabs etc.
Tinned Copper Braid - eBay

My previous tips on soldering 18650's
DrkAngel said:
Soldering 18650's.

I have soldered hundreds of cells, and have picked up a few rules for safety, reliability and ease.
Not the final "best method", but fair, basic guidelines.

If pulled from notebook packs, they are pre-tabbed, soldering is simple.

If bare cells, more difficult.

1. Make sure that solder points are clean, abrasion, with emery cloth, or dremel tool, works great. Typically, there is a "glaze" or plating present, scraping with a sharp knife works, also.
2. Use soldering paste - flux, a slight dab is plenty. (I use a Q-tip)
3. Apply small bit of solder to soldering iron, (25w minimum, higher recommended), allow to attain full temp.
4. Apply to abraded fluxed point for 3 seconds, remove iron and confirm solder bead applied. If failed, allow to cool, then reflux and retry with slightly longer application.
5. Connect cells. I just began using a pre-tinned copper braid, (Tinned Copper Braid). It works wonderfully. Pre-flux and apply small bead of solder to braid, or wire, at the connection point.
6. Apply braid to cell, apply solder to iron, pause for temp raise, push iron on top of braid till it collapses onto cell.
7. Remove iron, braid must cool for several second, before setting.(hold in place with toothpick, pencil etc.)

Method should be adjusted for variations, quality and wattage of soldering iron is the major variable.
A more powerful iron spends less contact time on battery and actually transfers less heat.

Practice can be done on "dead" cells.
"Practice makes perfect."

2008 Build 25.9V

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2008 Build 37V

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2011 Build 25.9V

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2011 37V "Braid" used as flexible Parallel-balance wires.
Less risk of ripping fragile tabs on Lipo.
Main power is channeled through 12ga stranded


file.php
 
DrkAngel said:
Red_Liner740 said:
Also, OP, would u entertain the idea of selling some of your made packs?

Honestly, 18650 packs require monitoring, and occasional repair.
If a person has the capability of, what I consider, "proper maintenance" then they would have the capability to build their own packs.
I would feel uncomfortable about supplying a pack to a person, possibly, lacking in the skill and knowledge to use and care for it.

I have built some for local persons, but I supply check-ups and service, etc. Upstate NY USA

In response to multiple PM's ...

Once again ... while I do promote "homemade" battery packs, I do not build them for others!
I try to give reasonably clear instructions on building your own.
My instructions assume basic electrical knowledge and skills.
If you are inspired, this is a project for you.
If you are confused ... please consult with, or refer this thread to a more electrical savvy friend.

I have found these "homebuilds" to require knowledgeable monitoring and, occasionally, maintenance.
 
Here some photos of my battery pack build.


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3.6v 24ah batteries ready to be soldered into 2 x 5s12p packs.





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They fit perfectly in the tackle box.




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First 5s12p pack is ready! I used a ide hard drive cable to check every 3.6v "block" as it fits the "1-8s alarm" nicely.




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10s12p pack finished. The configuration I choose will let me split the pack easily into 2 x 5s12p, I just need to find and add a banana jack/plug.


Tomorrow the first road test!! :D :D :D
 
Hi guys,

an update on my pack. Things are going quite well and I am pretty happy. The pack is performing nicely. I tracked some rides with a gps app on my phone (I don't have a bicycle computer). My ebike is fitted with a 36v 500w bafang rear hub (geared). The max speed on the flat is about 30-35kph (32 kph on average).

I estimate the range to be between 55 and 75km+ on 80% DOD.

Fullscreen capture 5152012 40756 PM.jpg

It's difficult to manage the "start" of the bike, the pack goes under 32v for less than 3-4 seconds because the throttle goes wide open no matter how gentle I am with my hand. I've found a workaround in this forum, and I am waiting for a component to test it. Apart from that the pack remains over 35.5v even if heavily under load (1100-1200w uphill for 10 seconds). Normal usage is less than 500w.
 
spuzzete said:
I estimate the range to be between 55 and 75km+ on 80% DOD.
Why estimate? Why not an actual test to get an actual range? It will also give you the actual battery capacity (Wh).

Nice data presentation. Suggestion to make it even more meaningful:
1) Add a column for average moving speed and optionally another column for top speed.
2) The 3 columns involving Ah are not very meaningful. When the battery is fully charged, 1Ah is XX Wh. When the battery is almost empty, 1Ah is YY Wh, where YY is always less than XX. This effect is exacerbated with LiCo (laptop cell) because LiCo has a wide range for battery voltage: 3.00V empty to 4.20V full charged.

Have fun and enjoy your home built battery.
 
Hi SamTexas,

thank you for the feedback and the clarification on the Ah. I calculated an estimated range because these are the very first rides and the batteries are not well balanced. I have an ImaxB6 charger but it's not up to the task. I ordered a cell balancer and I am waiting for it to get here. I do not want to discharge too deeply at this stage, but I can't wait to test the full range!

The data is just to have an idea of how the battery & bike are behaving. I have detailed rides data (speed, gps/map, altitude, average speed, distance) on the website of the app (strava) but I didn't put it on the spreadsheet yet.

8)
 
I'm a total fan of hacked packs and wild solder jobs, but I tell ya once you go tab welder you'll kick yourself for ever having had to deal with so much solder. Can't recommend it enough and it's really affordable and easy to put together. Keep the frankenpack photos coming! Love them! :)

http://endless-sphere.com/forums/viewtopic.php?f=2&t=2633

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spuzzete said:
... and the batteries are not well balanced.
When I first started building these packs, I manually balanced the pack using one or more 12V auto lightbulbs. I'm still using the same method today when necessary (not often).
 
pwbset said:
I'm a total fan of hacked packs and wild solder jobs, but I tell ya once you go tab welder you'll kick yourself for ever having had to deal with so much solder. Can't recommend it enough and it's really affordable and easy to put together. Keep the frankenpack photos coming! Love them! :)


Hey PWB, I'm not sure if I just underestimate how small 18650 cells are, but that looks like some heavier gauge nickel strip than most places seem to sell. What size is that, and do you mind telling me where you source it? I've found trouble finding affordable nickel strip. One or two of the places required a larger order, maybe I'll end up buying some after I get someone else to agree to buy half of it.
 
pwbset said:
I'm a total fan of hacked packs and wild solder jobs, but I tell ya once you go tab welder you'll kick yourself for ever having had to deal with so much solder. Can't recommend it enough and it's really affordable and easy to put together. Keep the frankenpack photos coming! Love them! :)

http://endless-sphere.com/forums/viewtopic.php?f=2&t=2633

IMG_0593.JPG

Wow man!That's pretty impressive!

As soon as I finish to work on my ebike I want to try to build a tab welder like you did, very cool 8)



@ SamTexas

I will try that! 8)
 
Kin said:
What size is that, and do you mind telling me where you source it?

Sunstone Engineering .375"w x .005"t x 25'L nickel strips. Not the most super conductive stuff for sure, but tab welds like butter with my 1.5 farad 16v welder and I've had 7-8kw bursts through it many times without melting it and routinely run it 2-3kw sustained for long periods of time. Brilliant stuff. A bit pricey with shipping, but fits perfectly to the 18650.

First one from the top:

http://www.sunstonespotwelders.com/spot-welding-accessories-nickel-strips.php
 
Shucks! That was the best stuff I could find, and the best price. I am grateful for the link, but I was convinced that was something slightly larger, perhaps because I'm not very familiar with the 18650 size yet [a large collection of LiIon packs still lie in their plastic shells, for now]. Or perhaps because I just don't yet have an eye for judging perspectives. Could have thought about it more though.

I did notice, if anyone is interested, that for 1 spool they charge $15 in shipping, until 5 packs, and at 6 the shipping charge bumps marginally to $16. If anyone lives in the northeast and is interested, I could buy two or three spools and keep one spool but sell the other two for the savings in shipping [i.e, no risked 'group buy']. it seems like shipping within the area via USPS should not be remotely $15.

Hey, i realize the last part seems off topic advertisement, I can edit that out, it was just something that came to mind while I was thinking of potential for putting together a pack.
 
Keep in mind 25 feet goes a long way. I've got 3 spools right now and 1 will likely be all I need for my current 18s10p pack... 180 18650 konion/sony cells... 1kw+ HOC. 75.6v~13.5ah pack. Capable of 8-10kw bursts easy. I'm not sure what you're looking for, but this stuff fits 18650s really well.
 
pwbset said:
Keep in mind 25 feet goes a long way. I've got 3 spools right now and 1 will likely be all I need for my current 18s10p pack... 180 18650 konion/sony cells... 1kw+ HOC. 75.6v~13.5ah pack. Capable of 8-10kw bursts easy. I'm not sure what you're looking for, but this stuff fits 18650s really well.

Cool, I'm glad to hear 25 feet goes a long way. that is encouraging. I'm surprised you get 8-10kw bursts, or even 2kw cont. Maybe I'm not thinking through this well. But so what amp rating are you putting through these nickel strips? I was under the impression that it would only be good for 10 amps continuous. Does that mean that you simply tap the parralel subpieces from several places at the pack so that all of the amperage doesn't draw along a single portion of the nickel strip? I think this was mentioned earlier with respect to not taxing the LiCo cells too much (a slightly different problem, since you're using Konions, but based on the same issue of resistance along the paralleled cells).
If you draw 2kw cont from a 18s10p pack, I suppose you're drawing 2000/3.7/18 = 30 amps
 
pwbset said:
Keep in mind 25 feet goes a long way. I've got 3 spools right now and 1 will likely be all I need for my current 18s10p pack... 180 18650 konion/sony cells... 1kw+ HOC. 75.6v~13.5ah pack. Capable of 8-10kw bursts easy. I'm not sure what you're looking for, but this stuff fits 18650s really well.

Cool, I'm glad to hear 25 feet goes a long way. that is encouraging. I'm surprised you get 8-10kw bursts, or even 2kw cont. Maybe I'm not thinking through this well. But so what amp rating are you putting through these nickel strips? I was under the impression that it would only be good for 10 amps continuous. Does that mean that you simply tap the parralel subpieces from several places at the pack so that all of the amperage doesn't draw along a single portion of the nickel strip [this would also mean each serial connection connects at several points]? I think this was mentioned earlier with respect to not taxing the LiCo cells too much (a slightly different problem, since you're using Konions, but based on the same issue of resistance along the paralleled cells).
If you draw 2kw cont from a 18s10p pack, I suppose you're drawing 2000/3.7/18 = 30 amps
 
Kin said:
If you draw 2kw cont from a 18s10p pack, I suppose you're drawing 2000/3.7/18 = 30 amps

Yeah that's typical for continuous current draw. I climb 1,600ft to work during my commute at around 2kw (more if I'm late for work 8) ). I do have multiple wire paths out of the positive and negative when it's all assembled. I've done dead stall starts during the climb when I'd see 50-60-75A spikes and it never blew any nickel stripping, but I rarely go over 30A sustained. I prefer volting up over amping up... cheaper and easier on equipment. Konion V cells will do my measly 2-3C draw all day long without getting the slightest bit warm.
 
Heya. So I thought I'd go ahead and see what I might snag from the packs I have [Only got through some of them]. I noticed a lot of bad cells, and I figure I should bring them to the batt recycling bin next time I'm at home depot, but I don't want to wrap them up nicely when they're junk cells. I've heard of LFP joke about throwing lipo in a saltwater bath. Actually, might that be a good way to kill the charge on these guys before I go recycle them? I assume the water sinks away the heat. Also, when I say the first picture is "good" I just mean these are the >3v cells.
 

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