Needing Expert Advice with a 4-cell 2P2S build

[spartacus001]

Hi guys,

I’m needing some expert opinions here for a build. I'm a newb so I need to pick your brains.
I plan to build my own 4-cell 2P2S battery pack using aftermarket 18650 so I can charge them individually.

Since my
Review of Ebay: 1800 Lumen CREE XML T6 LED Bicycle HeadLight Lamp last year

This light now quits at around 35mins (high) after an overnight charge. After a year of moderate use the battery capacity is only functioning at 20%.

Build Specs

Charger to be used: SYSMAX-Ind-Intellicharge

Battery option A: Xtar protected 3100mAh 3.7v



Option B: Samsung Unprotected 2600mAh


Battery Holder type:


Configuration Wiring 2P2S:



Questions:

1. For the new pack: If I wire in the protection board from the OLD pack can I use Protected cells in the holders?

2. Will this ‘double’ protection cause undesirable outcomes?

3. If I use my individual cell charger can I Omit the old protection board and use
UNprotected (and Protected) cells directly?

Thanks

[Infinity123]

The picture of the configuration wiring might be wrong! The connecting wire in the middle should not be there. Or maybe it has something to do with balanced charging of the battery pack ?

[Toaster79]

The picture of the configuration wiring might be wrong! The connecting wire in the middle should not be there. Or maybe it has something to do with balanced charging of the battery pack ?

Wrong! Always wire cells in parallel first then in series, so the two parallel cells act as one single

[HEY HEY ITS HENDO]

see post #9 in this thread.....LINK

the battery holders will not hold protected batteries .

these are good batteries, i have tested them ... http://www.solarforceflashlight-sales.com

[Knight511]

these are good batteries, i have tested them ... http://www.solarforceflashlight-sales.com

Caution for those that may not be running antivirus... that site is laced with a Trojan.

[Vancbiker]

My experience with holders that use coil springs is that the batteries "bounce" on them over rough terrain. This breaks the connection which can cause the light to flash, change modes, or turn off, depending the driver used. Go with the Digikey/MPD holders. They use a leaf spring on each end of the battery.

[mattthemuppet]

I'd go with the Samsungs, Digikey holders and re-use the PCB from the old pack. You'll still get better run time than you did with the original pack when new and you'll save a few $. The PCB is needed to protect against overdischarge or shorts - both things that can happen before you realise it, especially if you're putting cells in and out a lot. If you don't want to re-use the PCB (no reason not to that I can think of, but others might chime in), there are a bunch of 2S PCBs on eBay for ~$10 inc. postage - aim for 2.5A or so overcurrent, 2.75V overdischarge and that's about it.

[HEY HEY ITS HENDO]

i bought a couple of 18650 off Buyincoins..
....... they averaged 450mah over 5 discharge tests!!

[spartacus001]

Thanks Guys,
I’m still waiting on parts so I put together a temporary pack for now.

Here is An older but working laptop battery from a Dead HP Pavilion 6000.


Voila! Harvested 6 working 18650s 2600mAH
*Caution* Do NOT attempt this if you don't know what you’re doing. It can lead to a nasty little boom., fire and/or serious personal injury
Read this guideline from CPF before attempting this:
Tutorial: Laptop Battery Pack 18650 Extraction



Yay. The Battery pairs are already spot welded in Parallel


The Old MS Battery Pack wiring.
Bottom side:
From what I can tell this is congruent with the wiring diagram above in my first post.



Top side with the PCB:


Soldering the replacement Pack by adding Series circuit:


Soldering on the PCB on the other side:



Now I just need to get some large Dia heatshrink to wrap it all up.
After monitoring the Charge it for about 3 hrs it remainded cool and normal.

@ 3hrs I measured the voltage: 7.88volts
Interestingly after leaving it unplugged for 9 hrs the voltage read: 8.04 volts! Voltage balancing
I'll give it a full charge and test it tomorrow night after I fix my 2 broken spokes

[MK96]

It is better to charge each cell separately. I realized that as I disassembled the original blue ebay pack. Voltage reads after day: the 1S: 3.84, 3.85 and 2S: 2.4, 2.98. After charge/discharge cycle I throw away those 2S bad cells - capacity about 750mAh and 1000 mAh under 1A load. I also have some Thinkpad T400 3.6v 2600 Sanyos sitting at 3.8 and Sonys 3.7v 2200 from Lenovo G530. I do some charge discharge tests, but it is likely to throw them away. I believe they will have small capacity

Thanks Guys,
I’m still waiting on parts so I put together a temporary pack for now.

Here is An older but working laptop battery from a Dead HP Pavilion 6000.


Voila! Harvested 6 working 18650s 2600mAH
*Caution* Do NOT attempt this if you don't know what you’re doing. It can lead to a nasty little boom., fire and/or serious personal injury
Read this guideline from CPF before attempting this:
Tutorial: Laptop Battery Pack 18650 Extraction



Yay. The Battery pairs are already spot welded in Parallel


The Old MS Battery Pack wiring.
Bottom side:
From what I can tell this is congruent with the wiring diagram above in my first post.



Top side with the PCB:


Soldering the replacement Pack by adding Series circuit:


Soldering on the PCB on the other side:



Now I just need to get some large Dia heatshrink to wrap it all up.
After monitoring the Charge it for about 3 hrs it remainded cool and normal.

@ 3hrs I measured the voltage: 7.88volts
Interestingly after leaving it unplugged for 9 hrs the voltage read: 8.04 volts! Voltage balancing
I'll give it a full charge and test it tomorrow night after I fix my 2 broken spokes

[MK96]

I also came across the old laptop batteries, disassembled the Thinkpad T400 and Lenovo G530 batteries and I have got 6 x 2600 3.6V red Samsung cells and 6 x 3.7V green Sony cells. I recharged Sonys - heat up during charge (330-360mOhm int. resistance, charger stopped at 27 degrees Celsius) - so I am not plannig to use them. Now I am charging Samsungs (260mOhm int. resistance) to see if there is at least 1600-1800mAh, if not I won't use them too. I don't think used cells from laptop are any good.

[Vancbiker]

I don't think used cells from laptop are any good.

In my experience, the usefulness of cells from laptop batteries will be determined by why they were removed from service in the laptop. If the laptop is 3 years old and only runs 30 minutes on a charge, it's probably not worth the effort to tear up the battery.

I have salvaged 6 excellent Sanyo cells from the neighbors fairly new laptop after it was irreparably damaged, and 4 very good Sony cells from my son's laptop when the pack suddenly lost significant runtime despite being just over a year old. One set of the 2P cells in that battery were bad. I suspect one failed which killed its parallel mate.

[MK96]

In my case all of the cells are exhausted, every cell is in nearly the same state

In my experience, the usefulness of cells from laptop batteries will be determined by why they were removed from service in the laptop. If the laptop is 3 years old and only runs 30 minutes on a charge, it's probably not worth the effort to tear up the battery.

I have salvaged 6 excellent Sanyo cells from the neighbors fairly new laptop after it was irreparably damaged, and 4 very good Sony cells from my son's laptop when the pack suddenly lost significant runtime despite being just over a year old. One set of the 2P cells in that battery were bad. I suspect one failed which killed its parallel mate.

[spartacus001]

My battery pack was 4 years old and it was still holding its charge.
On this build the burn time on a ride was 2hrs on High + another 30 mins on Low before it shut down.
Not bad at all.

[MK96]

Mine are 2 & 3 years old, Sanyo holds 920 mAh and Sony 730 mAh - not worth bothering

My battery pack was 4 years old and it was still holding its charge.
On this build the burn time on a ride was 2hrs on High + another 30 mins on Low before it shut down.
Not bad at all.

[rtirado]

Out of curiosity, couldn't you get one of the MagicShine 4.4AH Li-ion batteries and make it work with that light as well? Looks like it has 4×18650 Li-ion battery (8.4V4.4AH) in it.

[spartacus001]

Yep. It would definitely work but I'm don't have much faith in non name batteries.
If I do a build use quality cells then I know the light is going to be reliable over the long term.

[adrenalnjunky]

Out of curiosity, couldn't you get one of the MagicShine 4.4AH Li-ion batteries and make it work with that light as well? Looks like it has 4×18650 Li-ion battery (8.4V4.4AH) in it.

It would work just fine, but it seems that the OP is wanting to upgrade his pack to something with as much burn time he can, while keeping a 4 cell configuration. 4.4AH means 2200mah cells, and they're of questionable origin. (Not hating, I have bought one of these same packs recently.)

[rtirado]

Yep. It would definitely work but I'm don't have much faith in non name batteries.
If I do a build use quality cells then I know the light is going to be reliable over the long term.

I definitely understand where you are coming from, if I had the electrical expertise I would build my own as well. I just purchased one of the 1200 lumen versions of the light you reviewed and the main negative feedback on it was the battery.
So I guess I was asking for myself on what I should plan to buy in the future as a replacement.

[MK96]

I think you need just a little electrical knowledge and a lot has been written here and in other threads regarding ebay 1800 lumen headlight, Skyray S6 and 'other' 3 XML clone. Basic knowledge is to disassemble the bad pack and replace the cells in manner they were there before. In this thread you can see a wiring of the pack and also photos of the replacement pack. Just take care of the cell poles - the plus and minus

I definitely understand where you are coming from, if I had the electrical expertise I would build my own as well. I just purchased one of the 1200 lumen versions of the light you reviewed and the main negative feedback on it was the battery.
So I guess I was asking for myself on what I should plan to buy in the future as a replacement.

[rtirado]

I think you need just a little electrical knowledge and a lot has been written here and in other threads regarding ebay 1800 lumen headlight, Skyray S6 and 'other' 3 XML clone. Basic knowledge is to disassemble the bad pack and replace the cells in manner they were there before. In this thread you can see a wiring of the pack and also photos of the replacement pack. Just take care of the cell poles - the plus and minus

Yea I guess I could at least try it out, haha.
For now I will see how long this cheap pack lasts me and start planning on rebuilding it for optimum performance.

[MK96]

I think about 2-3 hour. I went for Lipo battery and this is my setup with the old protection from the pack and I added also a low voltage indicator with a buzzer Runs far far better now.

Yea I guess I could at least try it out, haha.
For now I will see how long this cheap pack lasts me and start planning on rebuilding it for optimum performance.

[spartacus001]

Wow. That's huge capacity.
I'm not familiar w LiPos
Are they used by RCer?

[MK96]

Yes they are used by RCer. They are made for high current draws so you can get a little higher capacity than stated on the Lipo. I gave up rescuing cells from laptops because most of the time they were too exhausted and new cells (e.g. panasonic/xtar/keeppower) are unacceptably expensive - 6Ah 2S1P Lipo costs about 27 USD which is a price of 2 18650's and 10Ah 2S1P Lipo at price of about 56 USD which is about 4 18650's. I bought mine at Hobbyking store, but so far I am very pleased with the performance. The old PCB cuts off at 3V (critical threshold for Lipo cells), so it works as it should.

Wow. That's huge capacity.
I'm not familiar w LiPos
Are they used by RCer?

[adleysh]

Just finished up my 4S2P battery pack. Instead of taking a risk with soldering on tabs i used two 18650 4S holders glued them together and wired together pairs of batteries (one from each 4S sequence). I then took a balance wire of each of the battery pairs in sequence. leaving me with a 4S2P battery pack. It took a bit of thinking to get the wiring worked out as the sequence of the reverse pack is the mirror of the front pack.

Here is a pic of it all wired up without the heat shrink cover. The zip ties are just to keep everything together until the heat shrink is on.