ISDT BattGo BG-8S Battery Meter

[johninscotland]

Hi i have 2 sets of 4 lifepo4 batteries in parallel. i would like to use my ISDT BattGo BG-8S Battery Meter to monitor all 8 cells but i can only get all 4 in the first group and 3 in the second group, i can connect to either set and get a reading but not to all 8 ?
John

 

[johninscotland]

Each set of 4 cells in series is 12v i then joined the two sets in parallel total 12v out .. i do like the ISDT BattGo BG-8S as it shows me all cells at once (well it would if it could) i would like to top ballance all 8 cells and see what is happening is this possible ? Am i getting a confused reading due to my positive and negative outputs are joined ?

 

[roly1]

Hi, What was the outcome of connecting all 8 cells to the isdt bg-8s to your 4s2P battery bank? I want to do the same for instant cell monitoring. I can’t see why it wouldn’t work; common negative and individual cell positives.
I don’t care for balancing feature and there could be issues there. Probably need one for each 4s array.
I have a bms for each 4s array.
Cheers

 

[MisterSandals]

What was the outcome of connecting all 8 cells to the isdt bg-8s to your 4s2P battery bank? I want to do the same for instant cell monitoring.

I have the ISDT 8T which is nearly identical.
Your ISDT 8S is expecting an 8S battery which is wired with a 9 wire balance wire loom.
The 1st pin is to the 8S battery negative post on cell 1.
2nd pin to positive cell 1
3rd pin to positive cell 2
...
9th pin to positive on cell 8

As such, anything that uses this 9 pin connector, expects an incremental voltage between pins 2 thru 9 to be roughly 3.2V higher.
So if you have this wired to a 2P4S battery, pin 2 and pin 3, when used against pin 1, will both read 3.2V.
This would cause a BMS to see cell 2 as having 0 voltage and shut down.

Why not just use a 4S balance wire set on your 2P4S battery? This is how its intended to work. Besides, you don't need to monitor individual cells in 2P because they will act as a single cell with the same voltage but doubled capacity.

 

[roly1]

I think we are at cross purposes here and I have wrong nomenclature. Go gentle- older grey matter.
By 4S2P I mean 4 in series then paralleled, with independent bms’s for each 4S. So I have redundancy for crucial loads. ie switching out faulting 4S.
Therefore, shouldn’t pins two to five read correctly, pin 6 is expecting 16v and would only get either 3.2 v or 12.8v depending where you tap pin6. Is my thinking correct? I presume the firmware deducts previous cumulative V to give current cell voltage?
Then this device will work for half the bank. Need another for the other half? I guess you could have two plugs switch to check other half?
Reason I am contemplating this is having two BT bms’s I want both displays at same time. I have two iPhones but that is getting a bit redic.
Cheers for explaining this.

 

[MisterSandals]

By 4S2P

Doh, my dyslexia must have been flaring up. I read it wrong.

Therefore, shouldn’t pins two to five read correctly, pin 6 is expecting 16v and would only get either 3.2 v or 12.8v depending where you tap pin6. Is my thinking correct?

No. The ISDT or any device accepting an 9 pin (for 8S) connector is expecting the voltage between pin 1 (neg) and pin 6 to be (5x 3.2V =) 16V. To pin 7 19.2V. To pin 8 22.4V. To pin 9 25.6V.