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Ping bag/cooling LiFePO4 batteries

Posted: Apr 15 2010 2:19am
by lookingelectric
I've been running my electric bike with power tool batteries. These batteries go in a waterproof pannier bag that converts into a backpack. I've never had any problems with cooling, I suspect because the manufacturer spaces the cells out quite a bit. However, after 3 years, its time to let those batteries go.

I'm about to get a set of replacement batteries from Ping. Since I need to be able to rely on them on a daily basis, I want to make sure that they are both cooled and protected from water/mud/dirt properly.

I've thought about trying to find a 2-piece heatsink where one part is attached to the bag and the other glued to the battery. I would slip them together when putting the battery inside the bag. Unfortunately, I suspect that setting the bag up for this would be quite difficult.

How are people providing cooling for dense battery packs like the ones from Ping?

Re: Ping bag/cooling LiFePO4 batteries

Posted: Apr 15 2010 2:29am
by cell_man
As long as you are keeping within the discharge rate of the Ping I wouldn't have thought you need to get overly concerned with cooling them. If you are used to power tool cells which are generally high quality, high C rated cells you might find the relatively low C rating of the Pings results in more sag than you are used to.

Re: Ping bag/cooling LiFePO4 batteries

Posted: Apr 15 2010 2:44am
by olaf-lampe
I had used my ping packs in a 1500W/2800W peak Scooter and they never got more than warm. They got warmer, when I charged them with 1C :twisted:
The bad thing with duct-tape packs is, that you can only cool the outer cells and the rest remains warm. Over time it is better to keep every cell at the same temp.

You should take care of the mechanical stress to the pack, my old packs tend to rip off the cell tabs...

Now, after I repaired the packs, i use them for my recumbent, without problems so far ( knocks on wood )
Olaf

Re: Ping bag/cooling LiFePO4 batteries

Posted: Apr 15 2010 5:13am
by dogman dan
When i got my first ping two years ago, I worried about it getting too hot. I live in desert climate, and misunderstood the temp range. So I made a tight box out of aluminum for it, by wrapping a cookie sheet around it. Bringing the battery into the house, it cooled off much faster than the bare battery. Then I realized the operating range is in centigrade. Since then, I charge in a hot garage all summer, like 120F. No problems, though I do make sure the vent holes on my chargers are big. Lifepo4 just doesn't act like nicads that have to cool off before you try to charge. The battery I was trying to cool was basicly at ambient temp, 105F or so.

You do see stuff about cooling packs in the center, but they are talking about larger packs, where heat could build up, not a shoebox size bike battery.

You do want just a tiny bit of ventilation around the bms though. Just a corner of the bag unzipped when riding in hot weather, and don't bury it in foam or something.

Re: Ping bag/cooling LiFePO4 batteries

Posted: Apr 17 2010 8:19am
by lookingelectric
dogman wrote:When i got my first ping two years ago, I worried about it getting too hot. I live in desert climate, and misunderstood the temp range. So I made a tight box out of aluminum for it, by wrapping a cookie sheet around it. Bringing the battery into the house, it cooled off much faster than the bare battery. Then I realized the operating range is in centigrade. Since then, I charge in a hot garage all summer, like 120F. No problems, though I do make sure the vent holes on my chargers are big. Lifepo4 just doesn't act like nicads that have to cool off before you try to charge. The battery I was trying to cool was basicly at ambient temp, 105F or so.
There are two reasons that I want to be sure that everything stays cool. The first is cycle life; I want to be sure that I get the full 1000 cycles/3 years heavy riding before having to replace them. The second is reliability; I'll be using these with my daily ride and need to be sure that they work all the time.

A complicated or slightly expensive solution is worth it to me if it works very well and needs little maintenance once set up.

For the record, I expect 4 load situations:
1) Single battery, 15 AH @ 17 A, continuous
2) Single battery, 15 AH @ 33 A peak, 10 seconds
3) Dual battery, 25 AH @ 17 A, continuous
4) Dual battery, 25 AH @ 33 A peak, 10 seconds

I wonder; if I were to mount a fan on the side (not top) of a bag, could I count on it keeping rain out? Would there be some way of having it come on only when the battery is being drawn from?

Re: Ping bag/cooling LiFePO4 batteries

Posted: Apr 18 2010 12:14am
by 999zip999
What motor and controller, volts & amps ? speed ? range ?

Re: Ping bag/cooling LiFePO4 batteries

Posted: Apr 24 2010 6:54pm
by lookingelectric
999zip999 wrote:What motor and controller, volts & amps ? speed ? range ?
Its a cyclone, 24/27V, typically ~17A.

I've just gotten my battery and am pretty eager to use it. I just need to find a good carrying solution.

Re: Ping bag/cooling LiFePO4 batteries

Posted: Apr 25 2010 5:06am
by dogman dan
You in a climate hotter than 105F? My ping has never been seen hotter than ambient.