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diy solar

Sad and careless event happened today...

G

Goodoz

New Member
Joined
Sep 15, 2020
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47
Solar Friends -- Today I accidentally grounded a brand new 200AH LiFePO4. It arced pretty good. Before the ground, voltage read 13.2. After the ground, it's reading .2V.

Question/opinion: Did I cook the BMS or is it worse than that? It's a sealed battery so I'll have to destroy the case to get at the cells.

Thanks in advance! Oz
 
If momentary, not enough time to discharge the cells, it's obviously something open circuit.
Any fuses in there? Relay and wires?
We've marveled as how small the wires are inside some battery assemblies. Maybe they double as a fuse?
Relay or transistors for disconnect? Likely whatever is used for that got blown.
Does the BMS have small wires tapping all cell terminals? You could check cell voltages there.
 
What battery is it? DIY or a sealed ready made battery? What kind of documentation do you have about the battery?

Sounds like the BMS probably shut down.
 
Hedges said:
If momentary, not enough time to discharge the cells, it's obviously something open circuit.
Any fuses in there? Relay and wires?
We've marveled as how small the wires are inside some battery assemblies. Maybe they double as a fuse?
Relay or transistors for disconnect? Likely whatever is used for that got blown.
Does the BMS have small wires tapping all cell terminals? You could check cell voltages there.
Click to expand...
Hi -- thanks for your reply. I was hoping someone would tell me to "try this..." As I mentioned, I would have to cut the case to see the BMS or cells.
 
Goodoz said:
Hi -- thanks for your reply. I was hoping someone would tell me to "try this..." As I mentioned, I would have to cut the case to see the BMS or cells.
Click to expand...
How about answering the question. What battery is it?
 
Bob B said:
What battery is it? DIY or a sealed ready made battery? What kind of documentation do you have about the battery?

Sounds like the BMS probably shut down.
Click to expand...
It's not a DIY (but it's likely to become one very shortly...) It's Amazon available...200AH Amp-eeeeer-time (but ampere is spelled correctly)
 
"Our LiFePO4 battery has built-in BMS (Battery Management System) to protect it from overcharge, over-discharge, over-current, and short circuit with excellent self-discharge rate."

We don't know how short-circuit protection was implemented. Over-current could be turning off a FET. Short-circuit can mean interrupting several thousand amps, most easily accomplished with a fuse. Hopefully there's an accessible one inside.

Let us know what customer support says.
 
Usually if a BMS disconnects, the issue it is due to cell voltage too high or too low. Otherwise there might be a fuse inside your battery that blew. Perhaps your BMS sensed low cell voltage during the event and disconnected. This article discusses how to bring a battery out of low voltage cut-off. Not sure how applicable this is to your situation.

How to Awaken Sleeping Li-ion - Battery University

Learn what you can do to prevent a Li-ion battery to fall asleep
batteryuniversity.com

Looks like your options are:
  1. Return it.
  2. Contact the manufacturer and ask for help. If you admit what happened they will probably tell you too bad, sealed unit, buy another one.

    PRODUCT

    PRODUCT
    www.amperetime.com www.amperetime.com
  3. Open it up and look inside.
If you bought it from Amazon they are very good about returning "defective" goods. All you have to do is ignore your conscience.

If it had been me that damaged the battery, I would open it up and see what I could find. Odds are the cells are fine, it is possible the BMS died, but it is a more likely that there is an internal fuse that has blown.
 
Last edited:
HaldorEE said:
Usually if a BMS disconnects, the issue it is due to cell voltage too high or too low. Otherwise there might be a fuse inside your battery that blew. Perhaps your BMS sensed low cell voltage during the event and disconnected. This article discusses how to bring a battery out of low voltage cut-off. Not sure how applicable this is to your situation.

How to Awaken Sleeping Li-ion - Battery University

Learn what you can do to prevent a Li-ion battery to fall asleep
batteryuniversity.com

Looks like your options are:
  1. Return it.
  2. Contact the manufacturer and ask for help. If you admit what happened they will probably tell you too bad, sealed unit, buy another one.

    PRODUCT

    PRODUCT
    www.amperetime.com www.amperetime.com
  3. Open it up and look inside.
If you bought it from Amazon they are very good about returning "defective" goods. All you have to do is ignore your conscience.

If it had been me that damaged the battery, I would open it up and see what I could find. Odds are the cells are fine, it is possible the BMS died, but it is a more likely that there is an internal fuse that has blown.
Click to expand...
I will likely open it up this weekend...ordered another one this afternoon regardless (it's for a small overnight backup system for home...24V/200A). If the cells are ok, I'll make them part of the stationary system and use the 3rd (now, oddball) battery as a booster for the Bluetti.
 
HaldorEE said:
Usually if a BMS disconnects, the issue it is due to cell voltage too high or too low. Otherwise there might be a fuse inside your battery that blew. Perhaps your BMS sensed low cell voltage during the event and disconnected. This article discusses how to bring a battery out of low voltage cut-off. Not sure how applicable this is to your situation.

How to Awaken Sleeping Li-ion - Battery University

Learn what you can do to prevent a Li-ion battery to fall asleep
batteryuniversity.com

Looks like your options are:
  1. Return it.
  2. Contact the manufacturer and ask for help. If you admit what happened they will probably tell you too bad, sealed unit, buy another one.

    PRODUCT

    PRODUCT
    www.amperetime.com www.amperetime.com
  3. Open it up and look inside.
If you bought it from Amazon they are very good about returning "defective" goods. All you have to do is ignore your conscience.

If it had been me that damaged the battery, I would open it up and see what I could find. Odds are the cells are fine, it is possible the BMS died, but it is a more likely that there is an internal fuse that has blown.
Click to expand...
And thank you for the reading material.
 
Goodoz said:
I will likely open it up this weekend...ordered another one this afternoon regardless (it's for a small overnight backup system for home...24V/200A). If the cells are ok, I'll make them part of the stationary system and use the 3rd (now, oddball) battery as a booster for the Bluetti.
Click to expand...
You did the right thing.
 
If by "grounded" he means short circuited, it should have been easily handled by the BMS. The description says:
"Our LiFePO4 battery has built-in BMS (Battery Management System) to protect it from overcharge, over-discharge, over-current, and short circuit"

Accident or not, it sounds like a defective battery to me or he just needs to apply a wake up voltage.

The warranty:
We support 5 years warranty; And our battery life time can be more than 10 Years. That is the unique advantage for LiFePO4 battery technology.
Our five-year battery warranty includes the following privileges when used correctly in accordance with the manual instructions:
1. We’ll assist to analyze customer’s problem within 24 hours, and help solve problem, restore battery usage, and introduce the optimal use method;
2. If the problem can’t be solved, we’ll send replacement to the defective battery.
 
Last edited:
It's the BMS protecting the cells. I did a similar thing with 2x sealed units. After waiting 24hrs all was back to normal again. I found trying to use the batteries in any way shortly after the disconnect while below their working voltage just made them disconnect again, but after 24hrs all was well again.
 
pollenface said:
It's the BMS protecting the cells. I did a similar thing with 2x sealed units. After waiting 24hrs all was back to normal again. I found trying to use the batteries in any way shortly after the disconnect while below their working voltage just made them disconnect again, but after 24hrs all was well again.
Click to expand...
Well, that would be excellent so I will keep a lookout. I haven't tried to apply a load (again, they are only reading 0.2V). Hopefully, the meter would not send them back into protection mode.
 
Goodoz said:
Well, that would be excellent so I will keep a lookout. I haven't tried to apply a load (again, they are only reading 0.2V). Hopefully, the meter would not send them back into protection mode.
Click to expand...
Did you try applying a charge to the battery? That could be all it takes to reset the BMS. At this point it can't hurt to try. Apply a charge for a few seconds then see what the voltage is. I doubt the .2 volt reading is the actual cells voltage.
 
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