Replacing my Lipo setup

[jonnybump]

Hi all,
My setup consists 14S2P Multistar Lipo 16ah giving me 51.8V 32AH nominal. My controller's maximum current is 40A and at this level there's normally a voltage sag of around 3V. Today I noticed while going up a long hill that the voltage sag was much worse than usual and that the cells were not recovering as quickly as before.

When I got home I checked the pack and it was very hot. Two cells out of one parallel string were completely dead (ERR on voltage checker, I'm assuming 0V). The other string is completely fine, balanced perfectly. Buy my commute is over 20 miles and 14S1P 16AH (1 year old) probably isn't going to cut it. I suppose the cells have lasted well, they have over 370 cycles on them.

I need to look at options for a replacement battery pack, something that will last longer than my old pack, ideally in a safer package, and something that will put up with 40A burst when I need it. My bike is literally a car replacement for me - I use it all year round in ANY weather (and I'm from Wales, UK so that normally means RAIN!) and cover 40 miles a day. So lots of cycles is important - I charge at home and at work.

Has anyone come across these before? I've searched the forum but can't find any info about them. I could build a LifePO4 16S 20AH pack for around £320 (£0.31 per WH) compared with a Multistar Lipo 14S20AH pack for £275 (£0.26 per WH), but the LifePO4 chemistry should allow more cycles, should it not?

https://www.ev-power.eu/LiFePO4-small-cells/LiFePO4-High-Power-Cell-3-2V-20Ah-Alu-case-CE.html

Thanks
Jon

 

[cal3thousand]

Hi all,
My setup consists 14S2P Multistar Lipo 16ah giving me 51.8V 32AH nominal. My controller's maximum current is 40A and at this level there's normally a voltage sag of around 3V. Today I noticed while going up a long hill that the voltage sag was much worse than usual and that the cells were not recovering as quickly as before.

When I got home I checked the pack and it was very hot. Two cells out of one parallel string were completely dead (ERR on voltage checker, I'm assuming 0V). The other string is completely fine, balanced perfectly. Buy my commute is over 20 miles and 14S1P 16AH (1 year old) probably isn't going to cut it. I suppose the cells have lasted well, they have over 370 cycles on them.

I need to look at options for a replacement battery pack, something that will last longer than my old pack, ideally in a safer package, and something that will put up with 40A burst when I need it. My bike is literally a car replacement for me - I use it all year round in ANY weather (and I'm from Wales, UK so that normally means RAIN!) and cover 40 miles a day. So lots of cycles is important - I charge at home and at work.

Has anyone come across these before? I've searched the forum but can't find any info about them. I could build a LifePO4 16S 20AH pack for around £320 (£0.31 per WH) compared with a Multistar Lipo 14S20AH pack for £275 (£0.26 per WH), but the LifePO4 chemistry should allow more cycles, should it not?

https://www.ev-power.eu/LiFePO4-small-cells/LiFePO4-High-Power-Cell-3-2V-20Ah-Alu-case-CE.html

Thanks
Jon

0V on 2 out of 14S??? If you fully charged the pack in that condition, it may leave the cells at 4.9V each and that is a fireball waiting to happen. I hope that wasn't the case and if so, IMMEDIATELY take that pack outside away from your house and anything else flammable.


The LiFePO4 should allow for more cycles, should be far safer (doesn't supply it's own oxygen like LiCo), but be heavier per Watt-hour, and cost a bit more. Sounds like it would work quite well for you.

 

[zackclark70]

seems odd that a pack would die like that it would be worth taking a look to see what actually went wrong as you might beable to fix the pack

 

[dogman dan]

Odd that RC lipo cells died on you?

You can't fix those dead cells, but it might be fine to replace the dead packs and continue till the older packs die.

10c discharge rating on that lifepo4? Not a chance. But if they can stand 3c, then you could get away with using them if your 40 amps burst use is really seldom.

I'd set that controller to 30 amps for that lifepo4. It should handle that even if its only able to tolerate 1.5c without getting all hot and unbalancing itself.

After you run 30 amps awhile, you can then decide if they are staying cool enough, and balanced enough, to want to try 40 amps.

 

[zackclark70]

Odd that RC lipo cells died on you?

You can't fix those dead cells, but it might be fine to replace the dead packs and continue till the older packs die.

10c discharge rating on that lifepo4? Not a chance. But if they can stand 3c, then you could get away with using them if your 40 amps burst use is really seldom.

I'd set that controller to 30 amps for that lifepo4. It should handle that even if its only able to tolerate 1.5c without getting all hot and unbalancing itself.

After you run 30 amps awhile, you can then decide if they are staying cool enough, and balanced enough, to want to try 40 amps.

fyi 10c on a123 lifepo4 works

 

[motomech]

Hi all,
My setup consists 14S2P Multistar Lipo 16ah giving me 51.8V 32AH nominal. My controller's maximum current is 40A and at this level there's normally a voltage sag of around 3V. Today I noticed while going up a long hill that the voltage sag was much worse than usual and that the cells were not recovering as quickly as before.

When I got home I checked the pack and it was very hot. Two cells out of one parallel string were completely dead (ERR on voltage checker, I'm assuming 0V). The other string is completely fine, balanced perfectly. Buy my commute is over 20 miles and 14S1P 16AH (1 year old) probably isn't going to cut it. I suppose the cells have lasted well, they have over 370 cycles on them.

I need to look at options for a replacement battery pack, something that will last longer than my old pack, ideally in a safer package, and something that will put up with 40A burst when I need it. My bike is literally a car replacement for me - I use it all year round in ANY weather (and I'm from Wales, UK so that normally means RAIN!) and cover 40 miles a day. So lots of cycles is important - I charge at home and at work.

Has anyone come across these before? I've searched the forum but can't find any info about them. I could build a LifePO4 16S 20AH pack for around £320 (£0.31 per WH) compared with a Multistar Lipo 14S20AH pack for £275 (£0.26 per WH), but the LifePO4 chemistry should allow more cycles, should it not?

https://www.ev-power.eu/LiFePO4-small-cells/LiFePO4-High-Power-Cell-3-2V-20Ah-Alu-case-CE.html

Thanks
Jon

No other chemistry is going to perform as well for what you re doing than LiPoly.
I mean really, 370 Cycles?? For the avg. Ecyclist, that would be 3 or 4 years!
LiFePO4 is going to add a lot of weight to what must be a heavy bike as it is.
I buy my MultiStars on sale, even if I have to hold on to it for a while, and it's about half the cost of any other chem.
W/ my 12S/20Ah pack, I get almost zero sag on my 25 Amp controller and maybe 1V when the pack is down in it's last third. I suspect the 3 Volts say you see is due to tired batteries, even pulling 40 Amps.
The Multistars are low volatility, and safe w/ a little care and if I were you, I would stay w/ what works.
If anything, I would rethink your charging system of you are not bulk charging. I'm on my 4th. system and for all practical purposes, it's "plug and Play". I luv my MultiStars.

 

[jonnybump]

370 cycles is one years worth of riding for me haha! A 14s 32ah multistar pack will cost me £400 at a minimum, I don't know if I can justify replacing the pack every year

 

[dogman dan]

Those were not A123 lifepo4 cells. bet they lie about the c rate at least as much as others do. Its not really lying, but rather, if you want your pack to last a long time, it needs to discharge without getting all hot. So cut c rates in half is good practice.

If you have the cash to buy batteries every season, then go ahead and whack them.


Lastly,, all your lipo cells are not toast, just some of them. You might get much luckier next time. My last buy not so hot. I made my pack with 6s packs and 2s packs, to get to 14s. The 6s packs are doing fine one year later. the 2s packs just died. Same brand on both, but I got screwed on the 2s. Clearly they were not fresh.