ANT BMS parameters review

[justeve]

Hi everyone!
I just finished installing a BMS on a LIFEPO4 battery.
This is the first time I've installed a BMS and I think I got everything right! (Judging by no fire and good voltage on the ANT app)

I have a pack I've bought from Amazon that claims to be a 30AH 72V pack, the original BMS was 80/150 AMP bms, but it didn't charge so I got the pack for free.

The listing on Amazon said that the cells are A123 pouch cells, but when I opened the battery I've found pouch cells that I can't get any information about.

I'm not sure what the real discharge rate of the cells, so for now I'll set the controller to 80 continues and 120 peak, same continues value as the original BMS and a bit lower peak, and monitor the temp rise, would love to get your advice on how to determine how much juice I can squeeze from this pack and keeping it safe.


Now back to the subject!
The BMS I've bought is ANT 10S-24S 1.6cm thin, 120A cont 300A peak.
This is the parameters I've set / were set by default, can you please take a look and tell me if this all looks fine? I want to test it with my brand new QS138 but prefer patient over smoke.

Thanks!!

 

[amberwolf]

I have a pack I've bought from Amazon that claims to be a 30AH 72V pack, the original BMS was 80/150 AMP bms, but it didn't charge so I got the pack for free.
<snip>
I want to test it with my brand new QS138 but prefer patient over smoke.

If it didn't charge, and was a battery fault, the BMS was probably seeing cell faults so preventing charge to protect you from a fire.

What are all the cell voltages, starting from the most negative to the most positive? (not just what the BMS reads, if it tells you that, but verifying with a separate voltmeter on each cell or cell group).

If you really want to prevent smoke you should test everything and verify pack construction before continuing, and especially before charging it, especially since the sellers are already known to be liars about what kind of cells are in it--the cells may not even be new, or even be functional--there are plenty of batteries out there made of literal recycled garbage cells that are not safe to use at all.


If all cells are not already identical voltages, then the pack is made of mismatched cells of unequal capacities and other characteristics, which will only get worse over time.

If they're different enough already right now to stop the BMS from charging them, you may want to rethink using them.

Free isn't free when it costs you your ride (or home, etc).

 

[justeve]

I’ve forgot to mention that I’ve tested (using voltmeter) each cell voltage while the old bms was connected and all cells match to the 0.01 volts! I’m pretty sure the charge mosfets of the old bms are bad.

So that’s not a concern, the old bms did great job keeping the cells balanced

 

[justeve]

Anyone?

 

[amberwolf]

Keep in mind that the voltages you show there on all the cells is around the nominal voltage for Lifepo4 chemistry, and their SoC curve is very flat. This means that there could be significant differences in the cell capability or capacity; you won't know until you try to charge it up; when you do I recommend watching the cell voltage display during the charge process, checking on it as often as possible, and noting down any cells that don't remain identical to the others as you see them, and whether they were higher or lower in voltage. (higher means they have less capacity, lower means they have more).

They would probably never have been balanced by the BMS, since it didn't charge it probably can't balance them except right up near / at cell HVC (usually 3.4 to 3.65v for this chemistry).



But since they *are* all the same, it's unlikely that the original BMS would have kept it from charging due to cell voltages. Even if it was the wrong kind of BMS, for a different voltage chemistry, those are also all well above any LVC normally set in a BMS, so that shouldn't be it either.

That all said, after I go do dinner for me and the Schmoo (st bernard) I'll take a look at the settings screenshots and see if anything looks abnormal.

 

[justeve]

Keep in mind that the voltages you show there on all the cells is around the nominal voltage for Lifepo4 chemistry, and their SoC curve is very flat. This means that there could be significant differences in the cell capability or capacity; you won't know until you try to charge it up; when you do I recommend watching the cell voltage display during the charge process, checking on it as often as possible, and noting down any cells that don't remain identical to the others as you see them, and whether they were higher or lower in voltage. (higher means they have less capacity, lower means they have more).

They would probably never have been balanced by the BMS, since it didn't charge it probably can't balance them except right up near / at cell HVC (usually 3.4 to 3.65v for this chemistry).



But since they *are* all the same, it's unlikely that the original BMS would have kept it from charging due to cell voltages. Even if it was the wrong kind of BMS, for a different voltage chemistry, those are also all well above any LVC normally set in a BMS, so that shouldn't be it either.

That all said, after I go do dinner for me and the Schmoo (st bernard) I'll take a look at the settings screenshots and see if anything looks abnormal.

thanks, waiting for the settings review

 

[justeve]

Started charging, so far no more than 0.005 unit diff. this is acceptable correct?
Do I need to flip the balance switch when charging?