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diy solar

DIY 12V Lithium Battery Low Voltage while under light load

Bob B said:
The charge and float are both set to 14.4 ..... That should charge the battery fine, but wouldn't be good for the batteries long term. Once you get things working properly, I would set the float voltage quite a bit less.
Doesn't seem like you should be having problems achieving the charge voltage with 2 100 W panels.

I keep stressing .... use a different charger to see if the problem is with the charger or the pack.
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alright, thank you for the advice. I will order a charger from Amazon and try to charge it by plugging it into the wall. Will be cheaper than buying another charge controller. Appreciate the help, will update if/when I get the pack fully charged.
 
wlfpck1 said:
alright, thank you for the advice. I will order a charger from Amazon and try to charge it by plugging it into the wall. Will be cheaper than buying another charge controller. Appreciate the help, will update if/when I get the pack fully charged.
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Didn't you mention you already had a plug in charger for SLA? An SLA charger will charge the Life pack fine .... maybe just not to the full 100%
 
Bob B said:
Didn't you mention you already had a plug in charger for SLA? An SLA charger will charge the Life pack fine .... maybe just not to the full 100%
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Yes, my SLA charger only gets the pack to ~13.2V. That's about the same I can get on the solar charge controller. The battery charges fine with the SLA charger.
 
HMMM .... not sure what to think. Seems like the SLA charger should get the pack higher than 13.2 .... how long did you leave it plugged in?
 
Bob B said:
HMMM .... not sure what to think. Seems like the SLA charger should get the pack higher than 13.2 .... how long did you leave it plugged in?
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Left it plugged in about 12 hours. Wouldn't the SLA cut off around 13.2V since most SLA batteries wouldn't need to take more than that? See attached picture of charger. Thanks for your guidance as I am a newby to all of this!
 

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OK ... that is more of a battery tender ..... only .3A output. Gonna take a LONG time for that to do anything.

I'd go back to checking the voltage in and out of the SCC in full sun. Shouldn't be that hard to charge a 90 AH battery. How many days have you had the pack connected to the SCC?
 
Oh .... Sorry. That is 1A DC ... but still the same thing. Not really a charger, just a tender.

Does your Renogy have an indication of current into the battery while charging?

Edit .... just looked at the charge controller page. Looks like you should be able to tell quite a bit from the monitor screen. Maybe post some pictures of that during full sun tomorrow.
 
Bob B said:
OK ... that is more of a battery tender ..... only .3A output. Gonna take a LONG time for that to do anything.

I'd go back to checking the voltage in and out of the SCC in full sun. Shouldn't be that hard to charge a 90 AH battery. How many days have you had the pack connected to the SCC?
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Bob B said:
Oh .... Sorry. That is 1A DC ... but still the same thing. Not really a charger, just a tender.

Does your Renogy have an indication of current into the battery while charging?
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I can see this screen from my Renogy app. Wouldn't the PV panels have to consistently produce above 14.4V to get the pack up to 14.4V? Here's a few screenshots from the past few days with some data.
 

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The highest charge current you are seeing in those shots is less than 5 A .... Assuming your average is 4 amps, it would take 22 hours to charge the 90 AH battery.
Sure seems like you should be getting more from 2 100 W panels. Looks like the pack did go from 13.9 to 14.2 .... but since you said earlier it was 14.1 with a meter .... maybe it just isn't charged up fully yet.
It kinda looks like your panels aren't performing very well. Maybe they are dirty or not angled optimally for the sun conditions?

How many days have you had it on charge? How many of those days have been sunny?
 
Bob B said:
The highest charge current you are seeing in those shots is less than 5 A .... Assuming your average is 4 amps, it would take 22 hours to charge the 90 AH battery.
Sure seems like you should be getting more from 2 100 W panels. Looks like the pack did go from 13.9 to 14.2 .... but since you said earlier it was 14.1 with a meter .... maybe it just isn't charged up fully yet.
It kinda looks like your panels aren't performing very well. Maybe they are dirty or not angled optimally for the sun conditions?

How many days have you had it on charge? How many of those days have been sunny?
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I must have taken those screenshots with some clouds going by. I usually get about 130W with full sun. I can try and clean the panels/adjust angles and let them sit on the charge controller for a week and see if that gets them to full charge. Maybe I am overthinking this entire issue and voltage drop is from the battery being low SOC.
 
wlfpck1 said:
I must have taken those screenshots with some clouds going by. I usually get about 130W with full sun. I can try and clean the panels/adjust angles and let them sit on the charge controller for a week and see if that gets them to full charge. Maybe I am overthinking this entire issue and voltage drop is from the battery being low SOC.
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The pack was still taking a charge at 14.2V .... So, probably not charged yet. I'd get it fully charged up so you can start doing some load testing to see how much you actually put in and get back out of the pack.
 
The next time you're producing significant power, check that the battery voltage at the battery terminals is the same as the output voltage of the charge controller. A loose connection or high resistance in a fuse/breaker will prevent the battery from ever seeing sufficient voltage... not likely at those low amps, but we're just looking for reasons to say your cells aren't junk.
 
Took some screenshots of my panel/battery stats for today. Did not put any load on the battery at all and will not until I get the pack up to 14.4V.

As you can see as the sun goes down/panels produce less power the battery voltage drops. Very interesting. Note the time stamps in the top left of the screenshots.
 

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If you remove the charger .... what voltage does the battery settle at now? Looks like it is still taking a charge.

Is you temp sensor disconnected?
 
Bob B said:
If you remove the charger .... what voltage does the battery settle at now? Looks like it is still taking a charge.

Is you temp sensor disconnected?
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Battery is now resting/not being charged since it's dark outside. Reading 13.3V.
Temperature sensor does not work on Renogy Wanderer solar charge controller when the charge controller is set to lithium mode.
 
wlfpck1 said:
Battery is now resting/not being charged since it's dark outside. Reading 13.3V.
Temperature sensor does not work on Renogy Wanderer solar charge controller when the charge controller is set to lithium mode.
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That's what I figured with the temp sensor .... I think that resting voltage is up a couple tenths from yesterday. Wasn't it 13.1 yesterday?
A LiFeP04 can stay in that range for a long % of the charge.
 
Bob B said:
That's what I figured with the temp sensor .... I think that resting voltage is up a couple tenths from yesterday. Wasn't it 13.1 yesterday?
A LiFeP04 can stay in that range for a long % of the charge.
Click to expand...
Yes I think it is slowly taking charge which is exciting. I'll leave it on the charger for a few days and see how high I can get the voltage. Wonder what the correlation is between LiFePo4 voltage and SOC.
 
wlfpck1 said:
Yes I think it is slowly taking charge which is exciting. I'll leave it on the charger for a few days and see how high I can get the voltage. Wonder what the correlation is between LiFePo4 voltage and SOC.
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It looks like the SOC right now is based on voltage .... which is not a good way to measure it for LiFeP04. Some chargers will reset to 100% once fully charged and then track based on amps in and amps out after that.
I don't know how that Renogy charge controller handles it.
 
Bob B said:
It looks like the SOC right now is based on voltage .... which is not a good way to measure it for LiFeP04. Some chargers will reset to 100% once fully charged and then track based on amps in and amps out after that.
I don't know how that Renogy charge controller handles it.
Click to expand...
You have any good recommendations for external SOC meters?
 
I have on I am testing with ... but the jury is out on whether I would recommend it. Maybe someone else has one they will recommend.
It might even be less expensive overall to get a better SCC that tracks SOC. I'd wait and see what yours does one it gets to full charge.
 
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