Homemade Battery Packs

[CanadianWinters]

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.... Also, when I say the first picture is "good" I just mean these are the >3v cells.

Hi,

I recovered a lot of cells that were under 2.0v using an RC battery charger. Some of them recovered really well, other didn't but it's worth a try.

I also wrote a little guide on how I've built my battery pack, the guide is here

8)

 

[Kin]

Hi,

I recovered a lot of cells that were under 2.0v using an RC battery charger. Some of them recovered really well, other didn't but it's worth a try.

I also wrote a little guide on how I've built my battery pack, the guide is here

8)

Hmm, that's actually pretty encouraging. A few of the ones that were under 2v were in a string of other cells where the under 2v was clearly the runt. So I will toss those. But a few also seemed all at 2v, or two strings of 1v and one string of 2v (so it's the stronger cell). I might consider giving it a shot with those "better case 2v" cells. I'm not sure if it'll be worth the effort, but then again, this whole business might not be (said lovingly). It also looks like I'll need to be more generous with my cutoff since I only have so many packs. It felt like so many when I was storing them up .

Sidenote: Your guide is awesome [I really wish I'd been recording the "package label expected mAh" while I was ripping open these plastic packs, but one thing: It says "4.1-4.2v" but I think strictly speaking LiCo in these cells are 3.6v nominal, 4.1v optimal, and Lipo-LiCo is 3.7v nom 4.2v max. Obviously these are not strict limits, but I think 4.2v is alot more pushing it on these laptop cells than on the LiPo. Just speaking from the impression i've been given, not first hand knowledge or experience [itself a form of knowledge].

 

[marty]

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

See what looks like a 10 parallel, 1 series group of makita battery cells. Cells are flipped around from how they were originally. How do you remove the cells from the plastic separators so you can flip them around? Do you rip / peal the tab spot welds from one cell in a parallel group of two? Then spot weld it again?

 

[pwbset]

See what looks like a 10 parallel, 1 series group of makita battery cells. Cells are flipped around from how they were originally. How do you remove the cells from the plastic separators so you can flip them around? Do you rip / peal the tab spot welds from one cell in a parallel group of two? Then spot weld it again?

Yup. Dremel two upside down pairs, flip them and re-weld to the 3 right side up pairs. Maintains existing cell separators/pack structure, maintain all original deeply penetrated welds. No soldering. No excessive heat to the cells. So easy. I'll be starting with 18 in series in a triangle build. If there is room I'll up that to 20s since my motor is slow. Will kick out way more power than I'll ever need. Hoping to see max DoD of 50% and will be charging to 4.15v/cell. Hoping to get at least 300 good cycles.

6 quick dremel cuts... 4 seen here and 2 underneath:

 

[CanadianWinters]

Hmm, that's actually pretty encouraging. A few of the ones that were under 2v were in a string of other cells where the under 2v was clearly the runt. So I will toss those. But a few also seemed all at 2v, or two strings of 1v and one string of 2v (so it's the stronger cell). I might consider giving it a shot with those "better case 2v" cells. I'm not sure if it'll be worth the effort, but then again, this whole business might not be (said lovingly). It also looks like I'll need to be more generous with my cutoff since I only have so many packs. It felt like so many when I was storing them up .

Sidenote: Your guide is awesome [I really wish I'd been recording the "package label expected mAh" while I was ripping open these plastic packs, but one thing: It says "4.1-4.2v" but I think strictly speaking LiCo in these cells are 3.6v nominal, 4.1v optimal, and Lipo-LiCo is 3.7v nom 4.2v max. Obviously these are not strict limits, but I think 4.2v is alot more pushing it on these laptop cells than on the LiPo. Just speaking from the impression i've been given, not first hand knowledge or experience [itself a form of knowledge].

In my experience, you can't predict which cells recovers and which don't. The only way to know is to recharge them, let them rest for 24/48h, if the pass the first screening do the discharging test. It's time consuming but now I'm kinda used to it . For instance i had a pack of 4s3p that seemed ok (all voltages over 2.0v when extracted from plastic case), passed the 48h test and performed miserably on the discharge test (down to 3,2v @ 1C in less than 5 minutes). I also recharged these cells at 4.2v (I am trying a different charger to charge the whole pack) and they seem to tolerate well the recharge at 4.2v each.

Hope this helps.

Sidenote: Your guide is awesome

Thanks!

8)

 

[Kin]

I think I'll finish resurrecting these cells, but I might wait until I have a better idea what to use them for before I make the battery. I am constantly fluctuating between thinking "hey, this'll be great" and "ugh, these are not going to be reliable for a bike." But, really this thread is great! I don't have quite enough cells for a monster pack, even with the rest of the packs, but I could make a monster pack for a flashlight or anything else. At the very least, you'll see me with a 30 hour laptop battery by the end of the summer.

 

[DrkAngel]

I think I'll finish resurrecting these cells, but I might wait until I have a better idea what to use them for before I make the battery. I am constantly fluctuating between thinking "hey, this'll be great" and "ugh, these are not going to be reliable for a bike." But, really this thread is great! I don't have quite enough cells for a monster pack, even with the rest of the packs, but I could make a monster pack for a flashlight or anything else. At the very least, you'll see me with a 30 hour laptop battery by the end of the summer.

If you are going to leave them setting around ...

Rig them all as 3s, and keep a small AC inverter handy.
Will give you 120V AC for emergencies, camping etc.

Other uses ... that I have tried ...

Remove 1.4Ah Nicd cells from cordless power tools, replace with 5.2Ah Li-ion.
(Black & Decker "Firestorm" tools)
12V - 3s2p 11.1V
14.4V - 4s2p 14.8V
18V - 5s2p 18.5V
3.7x the run time, with "acceptable" brief surge output
Add 8s meter-alarm to monitor DOD.

Also tried ... running power from, 1/2 at a time, 37V 20.8Ah pack (18.5V), to run 18V weedwhacker and blower.

Pulled 2 - 6V lantern batteries and rigged in 3s8p 11.1V 20.8Ah into 12V florescent lantern.

Replace 12V 5Ah SLA with 3s8p 11.1V 20.8Ah in a cordless blower

Will try 2s?p 7.2V in 6V SLA multi lantern, light, fan, radio device.

Yeah I get bored ... and play ... a lot!

In the works - 25.9V 20Ah eZip pack with NOS(New - Old Stock) RC LiPo - $170.

 

[fredsparkle]

Hi Everyone

This is my first post on here, so a I have a fair number of questions.

I have a Costco Schwinn MidTown bike that I have converted with e-bikekit 500w direct drive rear motor kit which I was able to pick up at a local bike shop as a 36volt 9ah lead acid kit.

In seeing this thread I was inspired to peak around on e-bay and managed to email a seller who didn’t have a “make an offer enabled” an offer after a lot of brand new manufacture surplus batteries expired.

My accepted offer was only $50.00 +SH for 24 NBP001197-00 laptop batteries so I don’t have much into it.

The specs for these batteries are:

11.1V at 6600mah so I am assuming they are an internal 3s3p configuration at 2200mah?

In reading DrkAngel’s post 2600mah cells are current design so having 2200mah cells could indicate older cells that might have self-destructed though age?

I see laptop packs in generally 10.6v and 11.1v configurations what’s the difference? At 4.2v max voltage for a li-ion wouldn’t a full charge be 12.6 volts? Are they being conservative because they are not balance charging in a laptop battery pack?

Should I try to use these packs as is; or proceed directly to salvaging and testing the cells? If I wanted to use them without breaking them up, how would I capacities test them?

Or should I add balance wires so that they can be balance charged? If doing that should I charge to 11.6 or 12.6 volts?

I have a “Thunder T6 Multi-LiPo Battery Charger (4X 6-Cell) Professional Balance Charger/DisCharger w/ LCD Display” on order.

http://www.hobbypartz.com/75p-t6-multi-charger.html

Any idea if the outputs are isolated so it could be used on a large pack?

The e-bikekit controller 36/48V 20A brushless motor controller specifics that the maximum voltage is 60 nominal volts. What configurations should I build my packs for either separate cells, or ganging laptop batteries?

Thanks everyone!

Fred

 

[DrkAngel]

Li-ions have been variously rated as 3.6V (10.8V) or 3.7V (11.1V)/
You might think that the 3.6V would have less energy?
Strangely, in my testing, I have seen that a 3.6V had usable energy down to the 3.6V point ... while a 3.7V had little energy below the 3.7V point.
As for peak charging voltage, I determined this by testing the usable capacity by 100th of a volt.
Different "formulations" showed a wide variance of "usable range".
For example this 3.6V 2600mah cell displayed substantial "usable, from 3.6V through 4.2V.

While this 3.7V 2160mah cell (lipo) held little usable above 4.1V or below 3.7V.

Lithiums - mAh/100th V - Discharge Tests

I would recommend 4.15V(x3 = 12.45V) to 3.7V(x3 = 11.1V) as a very safe, long life , reasonable range.
Modify this by observation-testing, if there is substantial energy at higher and lower voltages, I say, it.s OK to use it.
It is when you try to scrape the small bits of energy that you damage the cells.

As for using the batteries "in packs", you will be using a multitude of parallel circuits, amplifying the complexity and limiting redundancies.
I would say it's best to remove cells and build into a pack, with balance wires-circuit.
Leave cells connected to each other - makes "build" much easier ... usually!

as for determining "isolated power supply-charger" :
Quick check - While charging 2 separated banks, run a voltage meter from 1 ground to the other positive, if 0V read, then should be "isolated".
But! I would recommend placing a small fuse (5A?) "in line" on each bank, at least during initial charging-test!

 

[fredsparkle]

Hi DrkAngel

Thanks for the information!

I would recommend 4.15V(x3 = 12.45V) to 3.7V(x3 = 11.1V) as a very safe, long life , reasonable range.
Modify this by observation-testing, if there is substantial energy at higher and lower voltages, I say, it.s OK to use it.
It is when you try to scrape the small bits of energy that you damage the cells.

As for using the batteries "in packs", you will be using a multitude of parallel circuits, amplifying the complexity and limiting redundancies.
I would say it's best to remove cells and build into a pack, with balance wires-circuit.
Leave cells connected to each other - makes "build" much easier ... usually!

as for determining "isolated power supply-charger" :
Quick check - While charging 2 separated banks, run a voltage meter from 1 ground to the other positive, if 0V read, then should be "isolated".
But! I would recommend placing a small fuse (5A?) "in line" on each bank, at least during initial charging-test!

Ok interesting that they quote the discharge voltage on the pack, rather then the peek voltage.

Now kind of eagar to actually receive my stuff and start testing, hopefully I will get a decent yeild.

Also since I protentionally have 216 of these cells I should concentrate on purchashing future packs that are 11.1v to maximize my chance of getting simular cells?

 

[HypnoToad]

Just finished reading this thread, it's rather long but there's lots of great info here.

I'm almost done doing a 18650 based pack, 10s 6p, I'll post some photo's when I can.

Today I was wiring up my balance cables to the pack, and I accidentally shorted out 2 of the wires with my cable cutters.

The short was only brief, but I still produced a few sparks.

Did I cause any damage to my cells at all?

All the voltages still measure ok, I balanced all the packs before paralleling them up and they're mostly around 4.082v per cell.

 

[DrkAngel]

Just finished reading this thread, it's rather long but there's lots of great info here.

I'm almost done doing a 18650 based pack, 10s 6p, I'll post some photo's when I can.

Today I was wiring up my balance cables to the pack, and I accidentally shorted out 2 of the wires with my cable cutters.

The short was only brief, but I still produced a few sparks.

Did I cause any damage to my cells at all?

All the voltages still measure ok, I balanced all the packs before paralleling them up and they're mostly around 4.082v per cell.

If the individual cells measure OK, then no problem.
"Typical" balance cables are light enough that damage is unlikely.

37V ~15Ah? 15Ah is a bit lacking, unless you're running <350w.
Might be OK, with pedal assist - getting started and on hills etc.
Highly recommend adding a few extra "p" - 20Ah minimum, 30Ah recommended.
But mainly ... to fit your use.
The more the merrier!

 

[SamTexas]

My first built ebike used a 12s6p pack (427Wh or 9.62Ah). In pedal assist mode it gave me range of 50 miles at an average speed of 17mph.
http://endless-sphere.com/forums/viewtopic.php?f=4&t=29356

 

[HypnoToad]

Just finished reading this thread, it's rather long but there's lots of great info here.

I'm almost done doing a 18650 based pack, 10s 6p, I'll post some photo's when I can.

Today I was wiring up my balance cables to the pack, and I accidentally shorted out 2 of the wires with my cable cutters.

The short was only brief, but I still produced a few sparks.

Did I cause any damage to my cells at all?

All the voltages still measure ok, I balanced all the packs before paralleling them up and they're mostly around 4.082v per cell.

If the individual cells measure OK, then no problem.
"Typical" balance cables are light enough that damage is unlikely.

37V ~15Ah? 15Ah is a bit lacking, unless you're running <350w.
Might be OK, with pedal assist - getting started and on hills etc.
Highly recommend adding a few extra "p" - 20Ah minimum, 30Ah recommended.
But mainly ... to fit your use.
The more the merrier!

I actually shorted out the tabs on the cells as opposed to the balance wires, the short was between 2 cells in series and left a black mark on my wire cutters! Still the voltages are ok, and it was only a brief short. I'm trying to be a little more careful now.

I was thinking 6p may be enough, but after seeing some of the 20p monster battery packs in this thread I'm now not so sure. I did start building it before even finding this thread however, and it was the most I can fit in the bikes existing battery mount. The bike is an Ezee Forza, which only has a 250W motor, so I guess 6p may be ok? Even so I've ordered one of those voltage monitor things, and if I'm getting too much voltage sag then I can always build a 2nd pack and run then in parallel. The bike did originally have a 10Ah Li-ion battery apparently, I bought the bike without any battery however hence me having a go with 18650's.

I did make a typo, I'm actually making a 12s 6p pack, and I did use a different method to you guys here, as I only found this thread yesterday. I kept each laptop battery pack together, as opposed to removing each cell, here's my method in case you are interested:

-=-

I had identical laptop battery packs, and either all cells were good or all cells in each pack were dead. Each pack is 4s 2p, and I chose to keep the packs together, and charge and balance them with an RC charger before paralleling them up. I used an Imax B6 with the current set to 1.6 amps charging current, and it would take between 4 to 6 hours to balance charge each pack from empty.

Once charged and balanced, I compared the total voltage of each pack and also the voltage of each cell and tried to match voltages and capacities, and I ran 3 laptop battery packs in parallel giving me 3 x 4s 6p packs. Here's a photo of one of these packs, this is the middle pack and the numbers are for each set of cells in series:

After insulating each pack I then put each pack end-to-end as I need a long thin pack to fit my battery mount, then I soldered the tabs together in order to parallel the packs:

And today I connected up the balance cables:

The short I made was actually between the tabs on the pack, but I've measured the cells voltage since the brief short and they all seem ok. I need to actually test this pack on the bike in order to really see how much current it can deliver.

I still need to solder on the main power cables and insulate the exposed connections, and once I've done that I'll make another post on how well it works.

Now I didn't test each cell individually, but I did find each pack did balance charge evenly and pretty quickly, and each 4s2p pacl had a capacity between 4400mAh-4600mAh when charging from empty according to my iMax B6 charger, so can I assume that all my cells are good? If there were any bad ones then surely balancing would have taken much longer and I would have seen reduced capacity?

My reasoning behind my method is that the laptop originally kept the pack balanced, so I'd try and avoid breaking up packs if i could, and also this method means it's quicker to build larger packs, if you have a large lot of identical packs like I do.

I would be interested to hear people's thoughts on this method as I'm learning as I'm going along here, and this is my first attempt, and it would be good to know weather building a 2nd pack using this method is a good or bad idea?

Thanks

 

[SamTexas]

I was thinking 6p may be enough, but after seeing some of the 20p monster battery packs in this thread I'm now not so sure. I did start building it before even finding this thread however, and it was the most I can fit in the bikes existing battery mount. The bike is an Ezee Forza, which only has a 250W motor, so I guess 6p may be ok?

As I told you in your other thread, you're perfectly fine. Yours is a true pedal assist ebike. You would be surprised how far you can go on that pack.

Now I didn't test each cell individually, but I did find each pack did balance charge evenly and pretty quickly, and each 4s2p pacl had a capacity between 4400mAh-4600mAh when charging from empty according to my iMax B6 charger

Assuming of course that your pack capacity is what you said it is (looks somewhat optimistic to me).

2 posts above this, I included a link to my first pack and how it performed in both pedal assist and motor alone mode. In both cases, the average discharge rate are below 0.5C.

 

[HypnoToad]

I was thinking 6p may be enough, but after seeing some of the 20p monster battery packs in this thread I'm now not so sure. I did start building it before even finding this thread however, and it was the most I can fit in the bikes existing battery mount. The bike is an Ezee Forza, which only has a 250W motor, so I guess 6p may be ok?

As I told you in your other thread, you're perfectly fine. Yours is a true pedal assist ebike. You would be surprised how far you can go on that pack. Assuming of course that your pack capacity is what you said it is (looks somewhat optimistic to me). 2 posts above this, I included a link to my first pack and how it performed in both pedal assist and motor alone mode. In both cases, the average discharge rate are below 0.5C.

Gotcha, thanks, I'm hoping to have this all up and running tomorrow if not Monday, and with any luck I will have a similar discharge rate to you. If so that will give me more than enough range. I'm not taking the mAh rating of my RC charger as gospel, as it seems to keep climbing when it's balancing each pack at the end of it's charge, but it's handy to have a ballpark figure and also good to know I'm putting working cells into my pack.

 

[SamTexas]

I'm not taking the mAh rating of my RC charger as gospel, as it seems to keep climbing when it's balancing each pack at the end of it's charge, but it's handy to have a ballpark figure and also good to know I'm putting working cells into my pack.

That's good for you. But I would not make the assumption that all your cells are good since you did not test each one (or at least each pair) individually. But you could have gotten lucky. A real life test with proper measurement instruments will tell a more complete story.

 

[fredsparkle]

Nimh like memory effect for totally drained Lipo 18650 batteries?

In a previous post I mentioned buying 24 NBP001197-00 manufacture surplus batteries via e-bay, got them all in and was able to identify the internal wiring and measure the voltages which was nil on all of them!

All of them where factory sealed in their anti-static bags, but deader than a doornail when I opened them up!

This battery form factor was actually shared between manufactures which seems rare in hindsight. The part number NBP001197-00 sometimes referred to as DR202 has a number of specification power levels, some in 10.8 and others in 11.1 voltage and mAh ratings.

Most of the 11.1 voltage specs packs I can find under this part number are 6600mAh 9 cell packs, mine have no mAh rating on the batteries.

The batteries are blue in color and labeled LGR18650P A&TB JA61A or JA61B (assuming this last part is the lot number).

Are they supposed to be 2200 mAh batteries?

Using a Thunder T6 multi charger I am attempting to revive these packs by:
1. Charging at 0.9A in Nimh mode with voltage cut off at 12.5 volts for thirty to sixty minutes.
2. Balance charging in Lipo mode at 3.3Ah until full (thinking 0.5C charge rate).
3. Measuring discharge capacity with the charger

In a marathon session I managed to get 13 of the 24 charged in one day using the four channels on the T6.

Letting them rest 12 to 24 hours resulted in voltages of:

V1 V2 V3 total
3.95 3.95 3.95 11.87
3.93 3.93 3.93 11.79
4.00 4.00 4.00 12.01
4.04 4.07 4.07 12.19
4.00 4.01 4.00 12.02
3.98 3.99 3.99 11.98
3.97 3.98 3.98 11.93
3.93 3.94 3.94 11.83
4.01 4.04 4.03 12.09
3.97 3.97 3.98 11.94
4.01 4.03 4.03 12.08
4.01 4.02 4.02 12.06
4.02 4.06 4.05 12.15

When I capacity tested the first four it was an even bleaker result:

Capacity mAh
2381
2220
2941
3854

So an initial result of 33% to 58% of expected capacity, yuck!

In experimenting with the charger I discovered that I hadn’t actually balanced charged them even though the charger complained when the individual cell leads were not hooked. So I recharged the first two of them again in balanced mode and discharged them again. With the following result:

recharge mAh Capacity mAh
3650 3359
3751 3288

They bounced back almost an Amp in one cycle! This seems like the memory effect you have in Nimh?

How many cycles should I attempt this for? Any idea of percentage capacity I should be happy with?

Unfortunately the channels on the Thunder T6 are not isolated and its charge and discharge rates are kind of lopsided 50 Watt charge verses 5 Watt discharge per channel!

That leaves me two option discharge batteries as 3S pack at 0.4Amps or do them in 1S zones at 1.0Amps.

Which option do you think will recover the most capacity in these batteries?

I.E. Should I be as gentle as possible or since these batteries basically slowly suffocated on the shelf, give them a good knock on the head to stir up the fire?

 

[Kin]

http://www.dansdata.com/gz011.htm Memory effect doesn't really exist in your sense, that link explains a bit.

However, very exciting that you are getting capacity back! Maybe it just needs to be revived, I have no idea why. When were these batteries originally manufactured, do you know? I would try a few more cycles. You could take some packs as the cycle tests, rather than cycling all 24 at a time, to see if it's worth cycling the rest.

 

[DrkAngel]

Which option do you think will recover the most capacity in these batteries?

I.E. Should I be as gentle as possible or since these batteries basically slowly suffocated on the shelf, give them a good knock on the head to stir up the fire?

I would recommend a lower amperage charge.
It is possible that your charger cuts off prematurely ... or you remove before the battery receives a "saturation charge". ... ?

Most chargers charge at a Constant Current ...
until target voltage is reached, then ...
Constant Voltage is maintained while the current tapers to nothing.
If the battery is removed before this 2nd stage, actual retained voltage and capacity is greatly reduced.

So, after your typical charge, try recharging for an extended period at a much lower (A) charge rate.
Try with 1 pack. ... ?

PS Make sure to bypass the oem circuitry and connect to cells directly.

 

[fredsparkle]

So, after your typical charge, try recharging for an extended period at a much lower (A) charge rate.
Try with 1 pack. ... ?

PS Make sure to bypass the oem circuitry and connect to cells directly.

Thanks; I haven't disconnected the OEM circuitry yet; using alligator clips to connect to the leads for the battery pack.

I was able to squeeze in another cycle on the first two batteries last night; still on a learning curve with this charger and with the 5 watt discharge rate I hadn’t set the safety timer to a high enough value to full test discharge the second set of batteries.

Discharge Capacity
[pre]Run 1 Run 2 Run 3
2381 3359 3222
2220 3288 3322[/pre]

Charage mAH
[pre]Chg 1 Chg 2 Chg 3
3650 3767 3709
3751 3784 3760[/pre]

So some sag back in this third run, will try a lower rate second top off charage after letting them rest abit, before the next dischage test.

Do you think my cells are supposed to be 2200mAh, so this testing target for 100% would be 6600mAh or 5280mAh for 80% of orginal capacity?

 

[DrkAngel]

Do you think my cells are supposed to be 2200mAh, so this testing target for 100% would be 6600mAh or 5280mAh for 80% of orginal capacity?

Should be near 6600mah for 3.2V - 4.2V.
Recommended 3.5V+ - 4.2V-. Typically very little energy below 3.5V.
Check when removing from charger, should be near 4.2V.
Try to get a static, charged voltage of 4.2V, for testing purposes.

Charger-discharger accuracy should be considered suspect, except for the very best units.

 

[fredsparkle]

Discharge Capacity
[pre]Run 1 Run 2 Run 3 Run 4
2381 3359 3222 3790
2220 3288 3322 4138[/pre]

Charage mAH
[pre]Chg 1 Chg 2 Chg 3 Chg 4
3650 3767 3709 3970
3751 3784 3760 4139[/pre]

Updated these figures with another run, so seeing some improvement. Run #4 was with a longer charge rate at 0.5A, rather then 3.3A per DrkAngel's suggestion.

Given it takes a long time to cycle and test each group of batteries I am thinking of the following proceedure to group these batteries.

1. Charging at 0.5A in Nimh mode with voltage cut off at 12.5 volts for sixty minutes.
2. Balance charging in Lipo mode at 0.5Ah until full.
3. Measuring discharge capacity with the charger at 0.4A in 3S 11.1 volt mode; if no report of cell imbalance
4. Balance charging in Lipo mode at 0.5Ah until full.
5. Measuring discharge capacity with the charger at 1.0A in for one parrellel zone of the battery, recharge zone at 0.5A.

Then should I group like batteries in parrallel groups, or try to balance capacity across the groups?

 

[fredsparkle]

As you can read from my previous posts I received a batch of new surplus laptop batteries that were discharged to zero while in storage and my efforts to revive them from this state.

Given the very slow discharge rate of my T6 multi charger and that the capacity seems to track the resting voltage. I used the following proceedure to initilize the remaining batteries.

1. Gang three laptop batteries together, tying together Grnd, V1, V2 and V3 for a 3S3P configuration.
2. Trickle charge in Nmih mode for two hours at 0.9A to bring the batteries off of zero.
3. Lipo balanced charge at 1.5A until charged (generally almost eight hours).
4. Waited a day after charging the last set and meassured the resting voltage.

Resting Voltage

• 
  #1 12.45
  #2 10.82
  #3 12.41
  #4 12.44
  #5 12.34
  #6 12.44
  #7 12.45
  #8 12.44
  #9 12.48
  #10 11.9
  #11 12.44
  #12 12.44
  #13 12.56
  #14 12.58
  #15 12.15
  #16 12.48
  #17 11.77
  #18 12.05
  #19 12.24
  #20 12.25
  #21 12.3
  #22 12.21
  #23 12.38
  #24 12.29
  

In looking at the list, my thinking is put aside the lowest four batteries and build the pack as a 48 volt pack using the laptop batteries in a four by five configuration, for a 12S15P final configuration. Which if the batteries were new would be 48v 33AH pack, since i am only able to revive about 50-60% of the orginal capacity will give me somewhere between 16-20AH.

I am thinking this will climb as they go through initial working cycles, like the first five batteries that I capacity tested.

Sorting by voltage I wind up with:

• 
  #2 10.82 Put aside
  #17 11.77
  #10 11.9
  #18 12.05
  
  #15 12.15 Group 1
  #22 12.21
  #19 12.24
  #20 12.25
  #24 12.29
  
  #21 12.3 Group 2
  #5 12.34
  #23 12.38
  #3 12.41
  #4 12.44
  
  #6 12.44 Group 3
  #8 12.44
  #11 12.44
  #12 12.44
  #1 12.45
  
  #7 12.45 Group 4
  #9 12.48
  #16 12.48
  #13 12.56
  #14 12.58

Does this seem like a decent plan or should I try to include the ones in my discard list for maybe another 3AH?

 

[DrkAngel]

Just go with your best.
Check the leftovers, good chance 1 bad 3.7V set of cells.
Keep the good sets as spares, eventual replacements etc.?