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ok crazy thing. New here.

themicks

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I have a LiFePo4 battery that is 100ah. I tested it with my meter and it had 12.48 volts. A little low but not bad. Hooked it up to a charge controller set the charge controller to the LiFePo4 battery type and it is showing only about 1/5 the charger and starts trying to charge the battery. I changed the battery type to another type (Ternary or Lith) and they show charge is full.

My battery has a BMS and came with a charger to hook into the power outlet at home so it could charge. I am charging the battery now. Been charging for an hour. It shuts off when it is done.

Also in a side not the solar cells were showing around 21 volts prior to hooking up the LiFePo4 battery. When I hook up the battery the voltage from the solar cells always drops at least 5 volts.

Any ideas or suggestions.


I tested my rig last night all night with fridge hooked up. Checked it at 2am and it was fine. Checked it at 4am and the controller was off, battery?????, Inverter and Fridge off.
 

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I have a LiFePo4 battery that is 100ah. I tested it with my meter and it had 12.48 volts. A little low but not bad.

EXTREMELY LOW.

Hooked it up to a charge controller set the charge controller to the LiFePo4 battery type and it is showing only about 1/5 the charger and starts trying to charge the battery. I changed the battery type to another type (Ternary or Lith) and they show charge is full.

Switch it back to LFP setting. A LFP battery at 12.48V is < 15% SoC.

My battery has a BMS and came with a charger to hook into the power outlet at home so it could charge. I am charging the battery now. Been charging for an hour. It shuts off when it is done.

Okay.

Also in a side not the solar cells were showing around 21 volts prior to hooking up the LiFePo4 battery. When I hook up the battery the voltage from the solar cells always drops at least 5 volts.

Normal. You can't pull current from a panel without dropping voltage. Look at your solar panel label. The Vmp value is where the maximum power output is, and you will almost always show a lower panel voltage than that at max power unless your panel cells are not higher than 25°C, and they usually are.

Any ideas or suggestions.

Yep. You have no clue about LFP voltage vs. SoC.

1690238519789.png
Note the huge jump between 13.2 and 13.1V 70% to 40%, respectively.

LFP voltage curve is VERY flat.

Lead-acid resting voltage (sitting for 24 hours) full charge is 12.6-12.9V typically. Note how little remains in an LFP battery. Abandon all you think you knew about 12V batteries.


I tested my rig last night all night with fridge hooked up. Checked it at 2am and it was fine. Checked it at 4am and the controller was off, battery?????, Inverter and Fridge off.

No surprise when starting with a nearly dead battery.
 
Last edited:
EXTREMELY LOW.



Switch it back to LFP setting. A LFP battery at 12.48V is < 15% SoC.



Okay.



Normal. You can't pull current from a panel without dropping voltage. Look at your solar panel label. The Vmp value is where the maximum power output is, and you will almost always show a lower panel voltage than that at max power unless your panel cells are not higher than 25°C, and they usually are.



Yep. You have no clue about LFP voltage vs. SoC.

View attachment 159167
Note the huge jump between 13.2 and 13.2V 70% to 40%, respectively.

LFP voltage curve is VERY flat.

Lead-acid resting voltage (sitting for 24 hours) full charge is 12.6-12.9V typically. Note how little remains in an LFP battery. Abandon all you think you knew about 12V batteries.




No surprise when starting with a nearly dead battery.
ok thanks. Got it back to LiFePo4 setting. Changed the way I have my solar cells wired (now getting 43 volts), thanks for explaining it
 
100AH battery is unlikely to power a refrigerator overnight.

A typical inverter probably has an idle power draw of around 40 watts. That is, the inverter is on with no loads. Even in ideal conditions, at most you can expect 8 hours of solar generation. So the remaining 16 hours will be drawing from the battery. 16 hours x 40 watts = 640 watt hour. This is only with the inverter on with no loads. Your battery has about 1300 watt hours available when at full capacity. That leaves 660 watt hours for your refrigerator. That is not a lot and you probably don't want to run the battery until it's completely dead.

I did the same thing and made similar mistakes too. I expected too much from a 100AH battery and grossly underestimated what the inverter and refrigerator will use. And I also underestated the solar generating hours. During summer, sunrise to sunset is about 16 hours. More than half of those hours are not useable for solar power generation. You'd be lucky to get 5 to 8 hours of solar generating time, not counting an ocassional cloud or bad weather. I eventually got a 300AH battery which could power my refrigerator overnight. Soon I found out that when there are clouds or rain for even just one day, the battery ran out the next day.
 
100AH battery is unlikely to power a refrigerator overnight.

A typical inverter probably has an idle power draw of around 40 watts. That is, the inverter is on with no loads. Even in ideal conditions, at most you can expect 8 hours of solar generation. So the remaining 16 hours will be drawing from the battery. 16 hours x 40 watts = 640 watt hour. This is only with the inverter on with no loads. Your battery has about 1300 watt hours available when at full capacity. That leaves 660 watt hours for your refrigerator. That is not a lot and you probably don't want to run the battery until it's completely dead.

I did the same thing and made similar mistakes too. I expected too much from a 100AH battery and grossly underestimated what the inverter and refrigerator will use. And I also underestated the solar generating hours. During summer, sunrise to sunset is about 16 hours. More than half of those hours are not useable for solar power generation. You'd be lucky to get 5 to 8 hours of solar generating time, not counting an ocassional cloud or bad weather. I eventually got a 300AH battery which could power my refrigerator overnight. Soon I found out that when there are clouds or rain for even just one day, the battery ran out the next day.
I was using the fridge as just a test here at home. The farmhouse I am going to be installing the solar system in only has lights and a well pump (That only runs to refill the pressure tank). So nothing like running a fridge in. Question, I have 2 100A batteries if i use them both at the same time will that help?
 
update:

solar cells 44 v average
battery 14.3 (but showed 14.5 after charge) so controller is doing some work charging it.
 
I was using the fridge as just a test here at home. The farmhouse I am going to be installing the solar system in only has lights and a well pump (That only runs to refill the pressure tank). So nothing like running a fridge in. Question, I have 2 100A batteries if i use them both at the same time will that help?
Generally, running a well pump is much more demanding than a fridge. Do you know much about the well pump?
 
Generally, running a well pump is much more demanding than a fridge. Do you know much about the well pump?
I used male and female 120vac plugs as a jumper, separated the connecting electrical cords and use that when plugging in an unknown amps rated device. Then I can use my clamp amp meter to determine its draw.
 
I used male and female 120vac plugs as a jumper, separated the connecting electrical cords and use that when plugging in an unknown amps rated device. Then I can use my clamp amp meter to determine its draw.
This will get you a general use amperage, but certainly will not tell you he power factor or running Wh usage for the day.
Better to get a killowatt style meter that logs all this, and have a real number to know what is needed.
 
I used male and female 120vac plugs as a jumper, separated the connecting electrical cords and use that when plugging in an unknown amps rated device. Then I can use my clamp amp meter to determine its draw.
I only visit the farm house once a month. Water usage would be minimal.
 
My 1/2 hp well pump pulls around 11-12A at 120VAC, or about 1300-1400W. I've observed it pulling a pretty steady 55A from my 24V LFP battery.

I don't have a soft start on my pump, and I've measured about 35A on start-up. It's only for a fraction of a second, but that equates to over 4,000 watts.
 
May be a dumb question. Probably is. I am only using on battery now at 100ah. If i add another 100ah batteries and i use them together, does that increase the ah ??
 
May be a dumb question. Probably is. I am only using on battery now at 100ah. If i add another 100ah batteries and i use them together, does that increase the ah ??

Multiple 12V in parallel adds capacity, so 100Ah per 12V battery.

Multiple 12V in series adds voltage, same capacity, so two 12V in series for 24V is still only 100Ah.

BUT

The energy stored is the same:

12V * 2 * 100Ah = 2400Wh

24V * 1 * 100Ah = 2400Wh
 
Multiple 12V in parallel adds capacity, so 100Ah per 12V battery.

Multiple 12V in series adds voltage, same capacity, so two 12V in series for 24V is still only 100Ah.

BUT

The energy stored is the same:

12V * 2 * 100Ah = 2400Wh

24V * 1 * 100Ah = 2400Wh
Thank you for the prompt answer. I have learned a lot over the last 2 days. Definitely need a bigger boat (battery) so that the system can handle a bigger power draw and not drain my battery.
 

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