[Ziggythewiz]

Originally Posted by lowcrawler

Is there a way to turn off the MiniBMS, say, for storage over winter? It would suck to have the MiniBMS take your cells down to harmful DoD levels....

Sure...

[sinopoly.david]

Originally Posted by lowcrawler

Is there a way to turn off the MiniBMS, say, for storage over winter? It would suck to have the MiniBMS take your cells down to harmful DoD levels....

The best way I think if you don't want to use battery, you'd better to recharge battery after 2~3 months

[MN Driver]

Originally Posted by sinopoly.david

I missunderstand...Thank you, Sir, But I don't know Jack Rickard's email. Can you tell me? I contact with Justin for distributing our cells in US recently.

info@evtv.me

[sinopoly.david]

Originally Posted by MN Driver

info@evtv.me

Thank you. I just opened his website and sent an email to him.

[JRP3]

Taking a quick look your maximum C rates are not very good. Also you are spamming a lot of battery threads so you might want to slow down a bit.

[noleanderthegreat]

How many people have actually used those Heter cells? I think almost nobody, especially not anyone whose opinion really has significance on this subject. Seems only newbies would consider a battery with those specs for anything.
I wouldn't even try them out for evaluation.

CALB-36 cells with no BMS, after top balance and daily charge/discharge cycles, the cells are very closely matched with no drift. Best LiFePO4 cell I have used.
GBS- I haven't found anything good or bad about the cells. I have abused them and the surefire ways to kill them is charging to over 4.2 volts or bringing them under .5 volts. The problem for me is cycle life, low C rates and cost too high. I like the plastic cases that come with the 20Ah-12volt packs, and it's a very convenient way to get batteries, as they have quick shipping times.
Thunder-Sky- Garbage. My cells are utterly useless after doing an initial top balance and installing a BMS. None of the cells were over charged or undercharged, they immediately became imbalanced and nothing I tried helped that, except very low C rates (they were in a motorcycle before). Now they are used as UPS batteries, for which they aredecent, albeit expensive.
Headway-Poor cost performance, I would never buy them again. They didn't stay in balance well enough, but were not as bad as TS cells. Their cost is undeservedly high for what you get, as there isn't any benefit I can find for cylindrical cells.

I stick with what I've tried and CALB beats all other cells by a long shot in every single category. I am using a very small pack (36s1p@40Ah) to push around my VW Beetle and they only put out a max of 350 amps, but they don't heat up excessively or seem to otherwise mind being used as such a tiny pack in a car. I would have done better with 70Ah cells, even at a bit lower voltage, as the larger Ah cells would not sag as far (from fully charged pack, mine sags to ~85 volts under WOT).

[trukr]

Originally Posted by noleanderthegreat

GBS- I haven't found anything good or bad about the cells. I have abused them and the surefire ways to kill them is charging to over 4.2 volts or bringing them under .5 volts. The problem for me is cycle life, low C rates and cost too high. I like the plastic cases that come with the 20Ah-12volt packs, and it's a very convenient way to get batteries, as they have quick shipping times.

I was looking into these cells because of their claimed 90% efficiency at -20C. I did notice the 1500 cycle life, but the C rating was 3C and 10C pulsed. Was your experience with them much less?

Seen your vid BTW. Slowed me right down. I went from add to cart, to sniffing for snake oil.

[Siwastaja]

Originally Posted by trukr

I was looking into these cells because of their claimed 90% efficiency at -20C.

Efficiency depends on both internal resistance, which depends on temperature, and power you are (dis)charging with. Low temperature increases internal resistance and hence lowers the efficiency, but if there is only little load, efficiencies near 100% can still be achieved.

At high load currents the efficiency can be very poor in cold, but it's exactly that loss that heats up the battery and therefore increases the efficiency again.

There is no single efficiency number for batteries, at least it depends on power. There is a maximum figure for a given chemistry (achieved at very low discharge currents) and for li-ion, that's very close to 100%.

[trukr]

Originally Posted by Siwastaja

Efficiency depends on both internal resistance, which depends on temperature, and power you are (dis)charging with. Low temperature increases internal resistance and hence lowers the efficiency, but if there is only little load, efficiencies near 100% can still be achieved.

At high load currents the efficiency can be very poor in cold, but it's exactly that loss that heats up the battery and therefore increases the efficiency again.

There is no single efficiency number for batteries, at least it depends on power. There is a maximum figure for a given chemistry (achieved at very low discharge currents) and for li-ion, that's very close to 100%.

Thanks for clarifying this for me. Tried to read up on this a little bit, and found numbers of 0.2C to work with. On a 144V 100ah system, that would leave me with what, less than 4hp to work with continuous? I think a temp controlled battery box that can be plugged in is a must.

I guess my biggest concern is cycle life due to cold temps. If the pack's temp was stabilized during and prior to charge or discharge, will that save cycle life even if the temp is allowed outside optimum when not in use?

[Ziggythewiz]

When not in use pack temp won't matter but if you let all that thermal mass get low it would probably take a while to safely bring it up. You're probably best off planning enough insulation so only the outer cells ever get cold enough to need the heating.