Budget 8S monitor recommendations?

[fafrd]

I’m building 2 8S 24V LFP batteries using generic 8S LFP BMS which does not include monitoring.

I’m not planning on monitoring continuously but think I will want to have the ability to monitor cells ~monthly, primarily to track matching and any mismatch/drift that develops.

I’d prefer not to chew up charge for the 99.99% of the time I won’t be monitoring, so a single monitor that can be plugged into a 9S cable harness would be an appealing solution.

Are there any low-cost 8S monitors members here can recommend? Ideally with easy capability to purchase multiple cables.

Alternatively, I might consider a wireless monitor for each battery if the standby current drain is sufficiently low and cost is reasonable.

So any recommendations on strategies for monitoring 8S LFP batteries and recommended budget products, either wired or wireless, appreciated.

 

[snoobler]

overkillsolar

 

[fafrd]

overkillsolar

Appreciate the recommendation but Overkillsolar seems to only sell BMS with integrated Bluetooth monitoring.

For my next battery I may consider that, but I’ve already got a vanilla 8S 200A BMS on my battery (which cost <40% what Overkillsolar is charging for a 100A 8S BMS).

So I’m more interested in adding a parallel cell monitor like this: https://www.amazon.com/ISDT-Battery...ocphy=9032080&hvtargid=pla-391484147019&psc=1

Especially if I can purchase additional harnesses, I can just leave a pre-wired harness in each 8S battery and connect the monitor when I want to occassionslly check cell balance.

 

[fafrd]

Appreciate the recommendation but Overkillsolar seems to only sell BMS with integrated Bluetooth monitoring.

For my next battery I may consider that, but I’ve already got a vanilla 8S 200A BMS on my battery (which cost <40% what Overkillsolar is charging for a 100A 8S BMS).

So I’m more interested in adding a parallel cell monitor like this: https://www.amazon.com/ISDT-Battery...ocphy=9032080&hvtargid=pla-391484147019&psc=1

Especially if I can purchase additional harnesses, I can just leave a pre-wired harness in each 8S battery and connect the monitor when I want to occassionslly check cell balance.

That ISDT BattGo BG-8S Battery Meter
Is an Amazon Choice product and has good reviews. And I also see that Amazon sells 10 8S harnesses for $8, so unless anyone here tells me ISDT BattGo is junk, I think I’m just going to pull the trigger on that.

Less than $40 to monitor the individual cells in as many as 10 8S batteries (and have 0mA of power leakage when not being used) is more my speed (at least while in learning mode),

Anyone here have any experience with ISDT and/or BattGo?

 

[MisterSandals]

So I’m more interested in adding a parallel cell monitor like this: https://www.amazon.com/ISDT-Battery...ocphy=9032080&hvtargid=pla-391484147019&psc=1

I have one of rhose they are the best of the budget monitors.
Nice feature is the low low voltage and out of balance alarms.

 

[fafrd]

I have one of rhose they are the best of the budget monitors.
Nice feature is the low low voltage and out of balance alarms.

Cool.

Our posts on the two threads crossed but that is exactly what I was looking for (a confirmation the BattGo delivers as promised and is not junk).

I’m going to place my order immediately and look forward to ‘seeing’ how well my cheapo 90Ah Varicore cells stay balanced as I cycle them...

 

[MisterSandals]

This one however is awesome for battery to battery charging. Far superior.

ISDT T8 Battgo Lipo Battery Charger/Discharger, Balance Charger Discharger 30A 1000W DC 2-8S LCD Display Digital Smart Battery Balance Charger for Li-Po Li-Hv Li-Ion Li-Fe NiMH Ni-Cd Pb https://www.amazon.com/dp/B077SRQR54/

 

[fafrd]

This one however is awesome for battery to battery charging. Far superior.

ISDT T8 Battgo Lipo Battery Charger/Discharger, Balance Charger Discharger 30A 1000W DC 2-8S LCD Display Digital Smart Battery Balance Charger for Li-Po Li-Hv Li-Ion Li-Fe NiMH Ni-Cd Pb https://www.amazon.com/dp/B077SRQR54/

Thanks for that. With Amazon, I have a month to ‘upgrade’ if I see the value and the good news is, since that another product from the same company, the 8S wiring harnesses I connect into the battery can probably work with either product.

I already have a 24V (28.6V) charger so what benefit would this 30A charger provide (aside from faster charging)?

Is it to rebalance cells if/when they become too unbalanced?

 

[MisterSandals]

already have a 24V (28.6V) charger so what benefit would this 30A charger provide (aside from faster charging)?

Is it to rebalance cells if/when they become too unbalanced?

I only charge by solar so can charge my utility batteries from battery charged by solar.
And i think the charge is very balanced which is nice.
I have several monitors, returned several others too. These 2 Battgo’s are my favorites.

 

[fafrd]

I only charge by solar so can charge my utility batteries from battery charged by solar.
And i think the charge is very balanced which is nice.
I have several monitors, returned several others too. These 2 Battgo’s are my favorites.

Gotcha - so if I wanted to charge my smaller ‘portable’ 24V LFP battery from my larger stationary 24V LFP battery, the more expensive unit would allow me to do that.

It’d probably same me some efficiency versus charging off of AC, but probably not a high priority for me...

But happy to hear the BatGo products deliver as promised.

 

[fafrd]

So I’ve finally got my new BatGO hooked up and balancing, but I have not been able to find any specification on max mA it draws per cell when balancing.

Has any seen a spec on BattGO balance current?

If no such thing exists, has anyone made an estimate from a balance cycle they have performed?

 

[ToadHarbor]

This one however is awesome for battery to battery charging. Far superior.

ISDT T8 Battgo Lipo Battery Charger/Discharger, Balance Charger Discharger 30A 1000W DC 2-8S LCD Display Digital Smart Battery Balance Charger for Li-Po Li-Hv Li-Ion Li-Fe NiMH Ni-Cd Pb https://www.amazon.com/dp/B077SRQR54/

That BattGo BG-8S is quite nice. It's easy to read in the sun and it's cheap.

 

[ToadHarbor]

So I’ve finally got my new BatGO hooked up and balancing, but I have not been able to find any specification on max mA it draws per cell when balancing.

Has any seen a spec on BattGO balance current?

If no such thing exists, has anyone made an estimate from a balance cycle they have performed?

The Manual says 1.2A, and it says that on anything larger than 100AH it will take FOREVER TO BALANCE.

 

[fafrd]

The Manual says 1.2A, and it says that on anything larger than 100AH it will take FOREVER TO BALANCE.

I was going to say ‘my manual doesn’t say anything like that’ but I decided to double-check first.

The little enclosed 4-sheet manual (folded) does say:

‘Support USB charging: QC 3.0, BC 1.2, Maximum Output 12V/2A’

So is that the 1.2A you are referring to? Is ‘BC’ = Balance Cell?

If you can post a link or a pic of the manual page that refers to balance current of 1.2A, I’d appreciate it...

 

[ToadHarbor]

Here is a 12 page manual. https://www.isdt.co/down/pdf/BG-8S_en.pdf

Don't see it saying it takes forever to balance 100AH cells with 1.2A of charging current. I did read it somewhere.

But if you think about it. Pushing 1.2A of charging into cells of a 100AH battery isnt much, isn't going to be fast. It took me 2 days to charge my 24V BYD pack to 26.4V. But it was kinda cloudy. I was mostly charging at 10-20 amps.

 

[fafrd]

My BattGO is currently working on a cell which is 9mV higher than my lowest cells.

Assuming the voltage curves in the sticky thread are correct, 9mV above ~3.243V translates to ~0.45% SOC or about 4Ah for my 90Ah cells. At 1.2A, that should translate to about 3-1/3 hours, so I’ll check it again at 7:30pm and see how it has progressed...

 

[fafrd]

Here is a 12 page manual. https://www.isdt.co/down/pdf/BG-8S_en.pdf

Don't see it saying it takes forever to balance 100AH cells with 1.2A of charging current. I did read it somewhere.

But if you think about it. Pushing 1.2A of charging into cells of a 100AH battery isnt much, isn't going to be fast. It took me 2 days to charge my 24V BYD pack to 26.4V. But it was kinda cloudy. I was mostly charging at 10-20 amps.

Thanks. I read through it carefully (twice) but can’t find any specification for balance current.

The only reference to 1.2A is the same ‘BC 1.2’ under USB Charging - is that what you are referring to?

 

[ToadHarbor]

Thanks. I read through it carefully (twice) but can’t find any specification for balance current.

The only reference to 1.2A is the same ‘BC 1.2’ under USB Charging - is that what you are referring to?

yes

 

[fafrd]

Well, if ‘BC1.2’ means 1.2A balance current, I should be in a position to confirm by tonight.

From watching the BattGO over the past few hours, my sense it that the Cell Balance function balances one cell at a time.

I’ve got 2 cells off by 8-9mV and all the others are within 1mV of each other (and black), so if is is balancing with a current or 1.2A, one cell at a time, I should see things unfold that way and everything should be over before I turn in for the night...

 

[fafrd]

Well, the BattGO finished ‘balancing’ at 4am, but I’ve come to the conclusion that it is next to useless.

Before beginning, I measured all cells with the same mV-precision voltmeter and had a worst-case mismatch of 12mV.

The BattGO reported a worst-case mismatch of 11mV and after balancing for ~13 hours, that had been reduced to 2mV.

However, when I unplug the BattGO and remeasure with my multimeter, the worst-case mismatch has increased to 14mV.

The BattGO states that their ‘Voltage Measurement Accuracy’ is +/-5mV and that their Balancing Cells Accuracy is <5mV.

If I assume my highest cell is being read 5mV low by the BattGO and my lowest cell is being read 5mV high by the BattGO, then those two cells are within 4mV of each other (<5mV) so it’s doing what it is specified to do, it’s just that balancing cells to within 15mV of each other is pretty useless.

15mV translates to ~15% SOC in the ‘flat’ part of the charge curve where I am now, while 15mV translates to less than 0.4% SOC in the ‘hockey stick’ part of the charge curve above 3.61V/cell, so before completely giving up on the BattGO, I’ll try charging up to 28.6V (3.575V/cell average) and try again.