Different overnight discharge between batteries - oddly a difference battery each time...

[Glenpk]

Hi All,

I have been a reader on this forum for about 2 years and taken the plunge in setting up my own system (with questionable success).

I am currently using a Growatt SPF 5000 es. I have 3x Delongtop 51.2v 200ah batters connected in paralell (no bus bar) and have 2 main challanges.

1) When connecting the RS485 and using Lith (L02) the charging seems to be capped at about 500w. On USE 2 it will run at 2500w+ This is basically what my solar panels are able to produce as I am running a single string of Jinko 440w x 7. I have a second string ready to install but working one thing at a time. (we are only running a fridge at the moment).

When I use the Lith setting I get very arcuate % reading (e.g 94% etc) so it appears to be communicate. USE2 on the other hand gives the 25% groups (e.g 50%,75%, 100% only).

Does anyone have any suggestions as to why my BMS might be capping the amps in and what I might do about it?

2) overnight there seems to be a fair amount of discharge. (estimate 5.0kw) the. I am getting uneven battery discharge . The odd thing is it is a different battery each night.

Night 1 - battery 1 (68%), battery 2 (74%) battery 3 (74%)
Night 2 - battery 1 (92%), battery 2 (74%) battery 3 (92%)
Night 3 - battery 1 (74%), battery 2 (97%) battery 3 (74%)
Night 4 - battery 1 (54%), battery 2 (90%) battery 3 (90%)

I understand that generally the discharge should be consistent. The batteries are all brand new (just installed in the last week).

Should I be concerned and if so what should I be doing?

 

[sunshine_eggo]

Many BMS don't register small currents. They might not accurately record even 100W/battery, and if that varies a little, it could account for randomness.

Do you notice any batteries suddenly jumping to 100% rather than a steady climb up?

 

[Glenpk]

Many BMS don't register small currents. They might not accurately record even 100W/battery, and if that varies a little, it could account for randomness.

Do you notice any batteries suddenly jumping to 100% rather than a steady climb up?

Hi Subshine

Not that I am aware of.

Apart from the cap when using the BMS protocol, the charging seems normal.

I have learned from the manufacturer that the batteries apparently use a Pace BMS.

Interestingly, yesterday all three batteries were at 84% in the morning. Perhaps a settling in period?

 

[sunshine_eggo]

Hi Subshine

Not that I am aware of.

Apart from the cap when using the BMS protocol, the charging seems normal.

I have learned from the manufacturer that the batteries apparently use a Pace BMS.

Interestingly, yesterday all three batteries were at 84% in the morning. Perhaps a settling in period?

Could be. Some BMS also require a handful of cycles and charges to full to accurately compute SoC.

You can always use a clamp DC ammeter to directly measure the current each battery is flowing. If they're within 5-10% of each other, you should be good.

 

[Glenpk]

Could be. Some BMS also require a handful of cycles and charges to full to accurately compute SoC.

You can always use a clamp DC ammeter to directly measure the current each battery is flowing. If they're within 5-10% of each other, you should be good.

Thanks for the tip. Any thoughts on why the BMS might be limiting the charge?

 

[sunshine_eggo]

1) When connecting the RS485 and using Lith (L02) the charging seems to be capped at about 500w. On USE 2 it will run at 2500w+ This is basically what my solar panels are able to produce as I am running a single string of Jinko 440w x 7. I have a second string ready to install but working one thing at a time. (we are only running a fridge at the moment).

When I use the Lith setting I get very arcuate % reading (e.g 94% etc) so it appears to be communicate.

The AiO is reporting the BMS-reported SoC.

USE2 on the other hand gives the 25% groups (e.g 50%,75%, 100% only).

In this mode, it's just guessing.

Does anyone have any suggestions as to why my BMS might be capping the amps in and what I might do about it?

When in closed loop mode, the batteries tell the AiO how much current it can send to the battery.

I would confirm you have the batteries properly configured. When connecting multiples, there are often specific DIP switch settings for each battery.

 

[Glenpk]

Could be. Some BMS also require a handful of cycles and charges to full to accurately compute SoC.

You can always use a clamp DC ammeter to directly measure the current each battery is flowing. If they're within 5-10% of each other, you should be good.

Thanks for the tip. Any thoughts on why the BMS might be limiting the charge

 

[Glenpk]

Looks like our issue is maintained Battery 3 is 68.11% Battery 2 81.78% and Batter 1 58.56% this morning .

The system is set up on our little farm so I will double check the DIP switch config this weekend, although I am relatively confident it is OFFF, FOFF & OOFF

I have found out from the manufacturer that the BMS installed is a 16s200a Pace. I have downloaded that believe is the PC software.