Low voltage on a LiFePO4. Is it dead?

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opus asked Sep 22, '21

Low voltage on a LiFePO4. Is it dead?

Greetings!
I just bought 3 x 12.8v 160AH victron batterys, sold as 'good'.
Two are indeed fine, and I've connected them (separately) to a BMS 12/200 as they haven't been used for a while, to re-charge & re-balance.
The 3rd however is reading 9.8v, and the BMS won't allow it to charge, presumably a low voltage protect. Is it dead? or could I try applying a normal charger, to try & boost the voltage above the low voltage limit?I'm guessing its dead, but I told the seller I'd see if anything could be done.

Also, I can't seem to find any info specific to this battery on the Victron website, just the smart batteries, which look a little different, so could someone tell me more about this battery? ie, is it a 'Smart Battery'? I guess its an older, non-smart one, but I'm not sure.
Also, does it have a BMS built in? so I can just charge it with any charger? or do I always have to use the BMS 12/200?
One more thing :) does that mean it doesn't have the bluetooth monitoring?
If thats the case, is a BMV700 the best kind of monitoring system?
Basically, I have one working system in a camper, with bms12/200, which is great, but doesn't have any monitoring yet, and I'm looking to build a second, larger one, with solar, and monitoring for both.

Thanks in advance.
Jody

battery charging battery

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Answer 1 · 2021-09-23T16:49:41Z

opus answered · Sep 23, 2021 at 04:49 PM

Thanks Rosamond.
Yes, I know low voltage can ruin them. I was just wonering if 9.8v is beyond salvation, as the absolute min cell voltage is 2.5, so its just a fraction under. I wondered if there was a little bit of 'safety factor' that might make it worth attempting something. I don't know what, but maybe a little boost into the voltage range of the BMS, or something.
It doesn't matter too much now, as it's being returned to the seller, but I would really like some more info on the two I have that are fine.
1. is it smart? (does it do bluetooth?)
2. Does it have an internal BMS?
3. Would BMV700 be the best monitoring system?
Any links to info on the website would be most appreciated, as I can't find any info on this product, not with a photo to verify that it's the same as the two I have.

Thanks.

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Answer 2 · 2021-09-23T16:56:06Z

opus answered · Sep 23, 2021 at 04:56 PM

For example, I see pictures of the same battery, but with 4 ventilation slots, marked 'Smart', and it doesn't say smart on mine, so I would presume it isn't, yet there's things like this, with the same battery as mine, but it's sold as a smart battery.
As i can't find it on the website, I'd just like some clarification.

smart.jpg (57.7 KiB)

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Matthias Lange - DE ♦ commented · Sep 23, 2021 at 06:38 PM

The pictures in shops are often just examples and/or old.

There should be a sticker somewhere at the battery, on that sticker is the serial number starting with HQXXYY

XX = production year

YY = production week

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Answer 3 · 2021-09-23T18:54:37Z

seb71 answered · Sep 23, 2021 at 06:54 PM

I was just wonering if 9.8v is beyond salvation, as the min cell voltage is 2.5, so its just a fraction under.

It depends.

9.8V battery voltage could mean all 4 cells have 2.45V or it can mean one cell has 0.8V (for example) and the other 3 cells have 3V each.

In the first case there is a high chance that the cells are still fine (recoverable). Not so much in the second case (for the cell with 0.8V and because of that for the entire battery).

If you were to attempt to recover them, best way would be to charge the cells individually, starting with very low current, until you get them above 3V. Then you could charge normally.

1. is it smart? (does it do bluetooth?)

"Smart" for Victron products denotes Bluetooth. That battery is not Smart (it would say so on the label if it was) and it does not have Bluetooth.

2. Does it have an internal BMS?

Most likely yes.

3. Would BMV700 be the best monitoring system?

BMV-7xx and SmartShunt products are used to monitor how much energy goes in and out of a battery, so that you can have a better idea about the battery state of charge. They are very good for that. But they are not a BMS (definition of a BMS varies, but usually a BMS means a system which monitors individual cell voltages - to prevent overcharging or over discharging of cells - and may also perform cell balancing).

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Matthias Lange - DE ♦ commented · Sep 23, 2021 at 07:03 PM

Victron batteries don't have an internal BMS (except the "Super Packs" and "peak power packs".

They only have the cell balancing internally.

The BMS has to be external.

https://www.victronenergy.com/battery-management-systems

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seb71 Matthias Lange - DE ♦ commented · Sep 23, 2021 at 07:13 PM

It's more of a special/different naming used by Victron.

I would say that in those batteries, half of the BMS is internal (in the battery case) and the other half is external (outside the battery case). The external part is called "BMS" by Victron, but the actual BMS is the internal part + the external part. They only work as a pair.

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Answer 4 · 2021-09-24T10:55:01Z

opus answered · Sep 24, 2021 at 10:55 AM

Thankyou @Seb71 , that's really helpful.
Is there any way to check individual cell voltages without cracking the case open?
eg, would a blue-smart charger tell me that?
(I'm guessing it would, but only for a smart battery, not mine.)
Cheers.

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seb71 commented · Sep 24, 2021 at 11:09 AM

Is there any way to check individual cell voltages without cracking the case open?

In your case, I don't think so.

eg, would a blue-smart charger tell me that?
(I'm guessing it would, but only for a smart battery, not mine.)

For Victron "Smart" LiFePO4 you can check the cell voltages using Bluetooth.

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Answer 5 · 2021-09-24T23:14:54Z

opus answered · Sep 24, 2021 at 11:14 PM

Thankyou very much for all your help.
Cheers.

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