diy solar

diy solar

Battery state of charge @ 13.3V when I put a 15watt DC load Voltage drops to 12.6. Cant figure it out why

S

SolarHawaii

New Member
Joined
Jun 28, 2022
Messages
19
I have a 12V 115AH LIFEPO4 Battery from Simpliphi. I am not sure if something is wired wrong or battery is bad. All terminals are very tight. Battery is charged and reads 13.3V and when I plug in a 15 watt load it drops to 12.6. Help would be much appreciated I have been working to try to get this system going for way to long now haha
 

Attachments

  • 20220721_124914.jpg
    20220721_124914.jpg
    191.7 KB · Views: 26
  • 20220721_124921.jpg
    20220721_124921.jpg
    182.6 KB · Views: 26
  • 20220721_124925.jpg
    20220721_124925.jpg
    150 KB · Views: 22
  • 20220721_125023.jpg
    20220721_125023.jpg
    187.7 KB · Views: 27
Can you put an amp clamp meter on it to confirm how many amps is being drawn off the battery at the time when the voltage drops?
 
13.3 is 3.32V per cell, or about 50% state of charge. Unless it is accepting charge, then the battery could be anywhere.
12.6 is 3.14V per cell, and is nearly 100% depleted.
I think your battery isn't fully charged. Need to be above 13.8 for a full charge.
 
Samsonite801 said:
Can you put an amp clamp meter on it to confirm how many amps is being drawn off the battery at the time when the voltage drops?
Click to expand...
When I put clamp meter around positive battery wire it reads 0.4 Volts when I have 15 watt load on. When I put around negative wire it reads 0.2-0.3 Volts
 
Supervstech said:
13.3 is 3.32V per cell, or about 50% state of charge. Unless it is accepting charge, then the battery could be anywhere.
12.6 is 3.14V per cell, and is nearly 100% depleted.
I think your battery isn't fully charged. Need to be above 13.8 for a full charge.
Click to expand...
I am going to start generator now and put LIFEPO4 charger on until full to see
 
SolarHawaii said:
When I put clamp meter around positive battery wire it reads 0.4 Volts when I have 15 watt load on. When I put around negative wire it reads 0.2-0.3 Volts
Click to expand...
It does not look like you set the meter correctly, the current is read in Amp not Volt.
Can your meter actually read DC Amp?
What is the measured Voltage at the battery terminals?
If you are drawing 15W from battery, then the current reading should be 15W/12.6V = 1.19A
 
Bud Martin said:
It does not look like you set the meter correctly, the current is read in Amp not Volt.
Can your meter actually read DC Amp?
What is the measured Voltage at the battery terminals?
If you are drawing 15W from battery, then the current reading should be 15W/12.6V = 1.19A
Click to expand...
 
At 20A rated of charger, to charge from 115Ah from 50% to 100% should be about 3 hours.
What is the Voltage reading now on the battery terminals without nothing connected to it?
Too bad you do not have a way to test DC current.
 
Bud Martin said:
At 20A rated of charger, to charge from 115Ah from 50% to 100% should be about 3 hours.
What is the Voltage reading now on the battery terminals without nothing connected to it?
Too bad you do not have a way to test DC current.
Click to expand...

Some of the other regular non-clamp multimeters (maybe he has one of the other kind), but they, a lot of times have the inline amp measure function (usually up to around 10a or less), where you plug the positive cable into the other probe port on the multimeter (the one for amps, it will say what is the max amps allowed without blowing the internal fuse), and wire the + and - into series onto one of the cables going to the load, and could potentially measure the current in the circuit that way.
 
Bud Martin said:
At 20A rated of charger, to charge from 115Ah from 50% to 100% should be about 3 hours.
What is the Voltage reading now on the battery terminals without nothing connected to it?
Too bad you do not have a way to test DC cur
Click to expand...
I do not have a way to test DC currently, Ill look into buying one tomorrow. The battery is not fully charged 14.4 and then it dropped to 13.4 which as I assume is resting charge level. I plug in the 15 watt load and it still drops down to 12.7. I am guessing I damaged a cell or battery is pooping out even though it is only a half of year old.
 
SolarHawaii said:
I do not have a way to test DC currently, Ill look into buying one tomorrow. The battery is not fully charged 14.4 and then it dropped to 13.4 which as I assume is resting charge level. I plug in the 15 watt load and it still drops down to 12.7. I am guessing I damaged a cell or battery is pooping out even though it is only a half of year old.
Click to expand...
I do have a DC clamp meter you can borrow...

Did you get this one used off facebook/craigslist? I was tempted.

EDIT: Nevermind--I see the used one I was watching is 24v and still for sale.
 
Last edited:
That's a lot of voltage drop. If that voltage drop is measured at the battery terminals then I suspect the battery. Otherwise, eliminate connections/components that are between the battery and the load. Bypass the 150 amp fuse by placing both ring terminals on the same stud. This is just for testing purposes, don't leave it like that for normal operations.
 
You must log in or register to reply here.

Similar threads

S
(LIFEPO4) Battery is at 13.3V when I put a 15watt DC load Voltage drops to 12.6. Cant figure it out
Replies
0
Views
203
SolarHawaii
S
DXHum
What does it mean when a battery does this...
Replies
7
Views
374
Hedges
Hedges
B
BMS Drops to about 1-2 amps when I put a load on it?
Replies
11
Views
416
bass-o-matic
B
I
Always switching load from grid power to battery/inverter when panels produce more energy than currently being used - Advantageous?
Replies
0
Views
152
Influencer
I
S
24v catl battery issue
Replies
3
Views
174
aliarifat794
A

diy solar

diy solar
Back
Top