diy solar

diy solar

Battery never charges higher than 26.6

Cruzian3

New Member
Joined
Mar 31, 2021
Messages
17
I've got 3x335 watt solar panels in series going into the MPP LV-2424-MSD through 30 feet of 10awg solar wire and charging a 24v Wolf battery from Bigbattery.com.

Bulk is set to 28.8
Float is set to 27.0

When I see videos of similar batteries their voltage is usually around 29v fully charged.

Can someone explain to me why my battery never charges higher than 26.6 even if there's no load?
 

Attachments

  • 20210316_174234.jpg
    20210316_174234.jpg
    114.5 KB · Views: 12
It can't possibly charge to 29V when your settings are less than that.

I'm not up to speed on your unit .... does it has an absorb setting? The absorb voltage is what you would normally expect to be the high end unless the BMS is cutting off charging because 1 cell is getting high.
 
It can't possibly charge to 29V when your settings are less than that.

I'm not up to speed on your unit .... does it has an absorb setting? The absorb voltage is what you would normally expect to be the high end unless the BMS is cutting off charging because 1 cell is getting high.
Thanks for responding. Sorry my particular battery model has a max of 28.8v. Whereas the video that I saw were of different 24v batteries also from Bigbattery.com with a max of 29v. So I know I assume my battery should charge higher. I reached out to Bigbattery.com and all they said was... that's a peculiar situation but weren't helpful in diagnosing the issue.

There is no absorb setting on the MPP.
 
Does that charge stop because the BMS cuts off charging .... or because the MPP drops back to float level?
 
Does that charge stop because the BMS cuts off charging .... or because the MPP drops back to float level?
Not sure. The display of the MPP shows the solar array is still charging the battery though, so I assume the BMS isn't cutting it off.

Maybe you can help me understand this... When Will suggests that the sweet spot for charging a 24v battery is between 24.0 and 26.6, how exactly do we set the upper limit? Do other charge controllers have an upper limit setting?
 
I've got 3x335 watt solar panels in series going into the MPP LV-2424-MSD through 30 feet of 10awg solar wire and charging a 24v Wolf battery from Bigbattery.com.

Bulk is set to 28.8
Float is set to 27.0

When I see videos of similar batteries their voltage is usually around 29v fully charged.

Can someone explain to me why my battery never charges higher than 26.6 even if there's no load?
Or maybe you battery’s BMS is cutting off the charge because a cell is going into over voltage before the whole pack can reach 29V.

It’s one of the nice things about getting a BMS you can monitor, like the Overkill BMS and can see how each cell is doing in real time.

I have a group of used cells I bought from eBay. 1 of the cells starts to run away at around 3.45V then quickly goes to 3.650V while the other cells are still at 3.4ish volts. Ultimately, I can only charge my pack to about 28.2V before I hit cell overcharge protection. Still not bad. I get about 68ah out of the original 72ah designed capacity.

Attached is a photo nearing the end of its top voltage.
 

Attachments

  • 10594CBD-3D15-48C6-BEB9-9917F509C694.jpeg
    10594CBD-3D15-48C6-BEB9-9917F509C694.jpeg
    102.5 KB · Views: 7
If those are A123 packs 28.8 is the max charge recommended. On mine I set my charger to 28.4- 28.6v or there one cell that runs quicker than the others and trips the BMS. I have tested capacity and it still tests at 2450wh so it’s pretty much a full charge.
maybe set charge to 28.6v and see what happens.?✌️
 
Not sure. The display of the MPP shows the solar array is still charging the battery though, so I assume the BMS isn't cutting it off.

Maybe you can help me understand this... When Will suggests that the sweet spot for charging a 24v battery is between 24.0 and 26.6, how exactly do we set the upper limit? Do other charge controllers have an upper limit setting?
I don't know the setup for the MPP .... maybe someone will check in that has one working successfully.

It doesn't seem to be a battery problem.
 
Will do. Thanks.
On a different note, I just read another thread on this forum with a similar setup as mine and a battery from the same company. The op said he called bigbattery.com tech support and they told him to set both bulk and flight to 29.2 which I believe is the "GRILA' model's max charge limit.

This is totally against Will's recommendation of 27.0 for float.

According to bigbattery.com, from reading the thread, it's safe and the bms will protect the battery.

Should I try it?
 
Ok. Max charge for my battery is 28.8. I set bulk to 28.7 and float to 28.6.

I'm now getting 28.5.
 

Attachments

  • 20210401_132007.jpg
    20210401_132007.jpg
    125.7 KB · Views: 4
+1 on float setting.. Voltage drop between inverter and battery explains the new .1v difference. No problem. Reset float setting lower and call it fixed
 
28.5v float is not recommended. I would set float at 26.8-27v.
why would you want the float so far below the bulk? that means the battery would have to discharge quite a bit before the solar starts charging again. I am fairly new to this but i set my bulk at 13.80 and float at 13.73 so that it can stop charging but not discharge much before it tops it off again. I would separate the voltage more if i was in the upper limit lets say 14.4v and 14.1 since the voltage moves much quicker in that range.
I would like to understand different reasons for settings since this is all my opinion
 
why would you want the float so far below the bulk? that means the battery would have to discharge quite a bit before the solar starts charging again. I am fairly new to this but i set my bulk at 13.80 and float at 13.73 so that it can stop charging but not discharge much before it tops it off again. I would separate the voltage more if i was in the upper limit lets say 14.4v and 14.1 since the voltage moves much quicker in that range.
I would like to understand different reasons for settings since this is all my opinion
Because when you remove the bulk charge from the battery, the voltage settles by about 1 volt. This is where you should float. Otherwise, you are constantly, frantically shoving charge at the battery. ALSO, this area between float and bulk is where your controller powers loads directly without discharging the battery.
 
Back
Top