12-04-2020, 06:39 PM | #111 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,167
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Re: 48volt club car limthium battery exploded
Most BMS do not provide enough balance current to do the job in a reasonable amount of time with the packs we use. I designed and built my own and I use a 1 amp balance current. This causes a fairly large voltage drop in the sense lines so I don't sense the voltage during the time that the balance current is on. I turn it off for a couple seconds to measure the cell voltages. I used power resistors and gave them plenty of air cooling space because at 1 amp they are dissipating 4W each. This is why most BMS do not balance at a very high current - they don't want to deal with the heat generated.
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12-04-2020, 07:07 PM | #112 | |
Gone Wild
Join Date: Aug 2018
Location: Orange County, California
Posts: 279
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Re: 48volt club car limthium battery exploded
Quote:
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12-04-2020, 08:18 PM | #113 | |
Gone Wild
Join Date: Oct 2019
Posts: 226
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Re: 48volt club car limthium battery exploded
Quote:
Since it was a one time thing (new pack), I just put a computer muffin fan on it to blow air across the case to help it out. I have my balancing settings pretty tight as I don't let any cell go beyond 10mv of the rest. I find it impressive that you built your own.. Not sure I'd want to invest that kind of effort into it, but if I did, I would employ multiple redundant backups for safety. |
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12-04-2020, 08:21 PM | #114 |
Gone Wild
Join Date: Oct 2019
Posts: 226
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Re: 48volt club car limthium battery exploded
Thanks! Its amazing to watch it trick the Grid Tie solar inverters to make power off grid.
Charged it at 120 amps and the pack temperature went up just 2 degreesC. LOL. I bought 70 of those cells.. wish I had bought 200. They're absolutely amazing. |
12-13-2020, 12:57 PM | #115 |
Gone Wild
Join Date: Apr 2020
Location: Hurricane, Utah
Posts: 2,788
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Re: 48volt club car limthium battery exploded
"Very nice and CLEAN work."
I second that, but you gotta cut those tails off of the wire holders-it's bugging my OCD |
01-31-2021, 12:46 PM | #116 |
Getting Wild
Join Date: Jan 2021
Posts: 104
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Re: 48volt club car limthium battery exploded
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04-13-2021, 12:31 AM | #117 | |
Gone Wild
Join Date: Oct 2019
Posts: 226
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Re: 48volt club car limthium battery exploded
Quote:
I can't imagine a routine circumstance where more than two or three cells would have to be drained concurrently.. that's 4 to 12 watts to dissipate, which isn't much.. Some lithium ion LED flashlights dissipate that much energy. My REC BMS has an internal temp sensor that stops balancing current if the unit gets too warm.. first time I hooked it up, I had 3 cells low so it actively drained the other 11.. and ya, it got warm and tripped its internal temp limit.. it just waits a few, cools down, and starts over again. But that was upon initially hooking the system up, since then, I don't think I've ever seen it work on more than 1 cell at a time. All I know is that these 100mA balance currents are a joke if trying to use them on a larger pack. From experience, I figure a BMS needs about 50mA per kWh of pack capacity. So if you have a 5kWh golf cart battery, you need about 250mA of balance current.. |
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04-13-2021, 12:33 AM | #118 | |
Gone Wild
Join Date: Oct 2019
Posts: 226
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Re: 48volt club car limthium battery exploded
Quote:
But if I do that, I'll have to tell my wife that my system is finished.. then I won't be able to add more capacity because she'll say "I thought you said you were done"... For now, I just say "I have some more work to do on it but its working so we're good for now" LOL |
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04-13-2021, 06:47 AM | #119 | |
Gone Wild
Join Date: Oct 2012
Location: Southwestern Pa.
Posts: 6,214
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Re: 48volt club car limthium battery exploded
Quote:
The ZEVA BMS advertises it's internal shunt balancing to be 120MH. This BMS has worked fine on my 14 module Leaf pack for years now. |
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04-13-2021, 08:36 AM | #120 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,167
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Re: 48volt club car limthium battery exploded
If you start with a pack in pretty good balance, then the lower balance current will do the job so it makes sense to manually balance a new pack before using the BMS for balance. Many BMS are not very large and they do not have the ability to dissipate much heat so balancing is very slow.
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Tags |
club car, explosion, fire, fire truck, linthium battery |
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