why does battery % show 49% but voltage is 53.2v

[tbaleno]

I have am mpp 6548 and the batteries (lifepower4) seem full. The led's on them show all lit up so I assume between 75% and 100%. However, the mpp is showing the battery percent at 49%. The voltage reading of the batteries is 53.1V which according to some charts on the internet should be about 90% During the day the batteries will charge up to 55V and sit there and the solar charging cuts out making me think they are full. At that time they show about 69% but when the sun goes down the battery percent drops to the 49-50% range and voltage drops to the 53.1-53.3 range.

I'm just curious as to what is going on.

 

[Bobert]

I have am mpp 6548 and the batteries (lifepower4) seem full. The led's on them show all lit up so I assume between 75% and 100%. However, the mpp is showing the battery percent at 49%. The voltage reading of the batteries is 53.1V which according to some charts on the internet should be about 90% During the day the batteries will charge up to 55V and sit there and the solar charging cuts out making me think they are full. At that time they show about 69% but when the sun goes down the battery percent drops to the 49-50% range and voltage drops to the 53.1-53.3 range.

I'm just curious as to what is going on.

The unit probably doesn’t actually count watts with a shunt so the soc is likely guess based on voltage dependent on your charge profile.

 

[tbaleno]

Ahh, I thought it would just look at the voltage and know. I didn't realize it used the charge profile to calculate.

 

[Bobert]

Ahh, I thought it would just look at the voltage and know. I didn't realize it used the charge profile to calculate.

I am only guessing that is the case but I’m pretty sure that is how my AIO does it.

 

[Ampster]

I didn't realize it used the charge profile to calculate.

That is not it either. It typically resets to 100% at the top of the charge. Maybe that is what you mean. Then it should count Coulombs (Amphours and/or Watthours) to arrive at a guestimate of SOC. Of course you have to enter the correct amount for capacity of your pack.

 

[Bobert]

That is not it either. It typically resets to 100% at the top of the charge. Maybe that is what you mean. Then it should count Coulombs (Amphours and/or Watthours) to arrive at a guestimate of SOC. Of course you have to enter the correct amount for capacity of your pack.

My AIO has no means to enter the size of the battery only it’s chemistry. I’m not sure about the mpp.

 

[Ampster]

My AIO has no means to enter the size of the battery only it’s chemistry. I’m not sure about the mpp.

Then it is using some other less precise method of determining the SOC and that number it reports will always be off. If you can track kWhs of discharge since last full charge that may be your most accurate number.

 

[tbaleno]

When I used the following parameters the capacity seems more "normal"

Setting 5 to USE (user defined)

Setting 12 to 46V (Setting voltage point back to utility source when selecting SBU)
Setting 13 to 58V (Setting voltage point back to battery mode when selecting SBU)
Setting 26 to 58V (Bulk charging voltage (C.V voltage) )
Setting 27 to 56.5V (Floating charging voltage)
Setting 29 to 44V (Low DC cut-off voltage)

I got these settings from this video:

where he was having problems with balencing. Apparently he got them from signature solar.

Just thought I'd post this in case others were having the same issue.

If these numbers don't seem sane to anyone please let me know.

 

[camelCase]

Is the 53.2V you're seeing while charging, or at rest?

 

[tbaleno]

Is the 53.2V you're seeing while charging, or at rest?

At rest. It definatly looks like the 6548 uses the configuration parameters to calculate the battery capacity % and not the actual voltage of the battery.

 

[Risky Rob]

Early this morning, my SCC was showing the battery at 100%, but the actual voltage of the battery, tested with a multimeter at the battery terminals showed it at about 70%.

 

[Dforster]

Do yourself a big favour, buy one of these things https://www.victronenergy.com/battery-monitors/smart-battery-shunt. I have fitted all manor of solar systems and this little shunt gives you very accurate readings, with a turnaround value reading, so you can see what goes and what comes out easily. It bugs me it’s not WiFi (it’s Bluetooth) but the app to connect works well and will help you in achieving good turnaround numbers.