I have 24 12v 100ah Deka Batteries that I got for $20 each, I had planned on running two SPF 5000 ES inverters with two sets of 10 - 330watt panels on each. I am having bad shading issues and having tree taken down but still have too much shading on my roof to put all 20 panels out. So for now I'm running one inverter with 10 panels on it with 4s3p battery. I have lots of batteries left. Should I just keep adding more sets or should I just leave it at 300ah?
Can you have too many batteries?
- Thread starter barkster
- Start date
sunshine_eggo
Happy Breffast!
What is the state of health of the batteries? Batteries may hold voltage very well, but that doesn't tell you their capacity. You believe you have 300Ah, but do you have any data to support it?
I purchased 8 used Trojan T-1275. I spent weeks testing and equalizing them before deployment and knew their actual capacity. I wouldn't do it otherwise.
When building 48V strings, did you fully charge each 12V battery individually to full and then again in parallel to ensure that all 12V were fully charged before placing them in series?
Different battery manufacturers recommend different things. You'll rarely find more than 4 parallel strings. You literally need to be monitoring each individual 12V to ensure its not going out of range. You already need to monitor 12.
Are these flooded cells? If so, you need to be checking specific gravity regularly as well.
I purchased 8 used Trojan T-1275. I spent weeks testing and equalizing them before deployment and knew their actual capacity. I wouldn't do it otherwise.
When building 48V strings, did you fully charge each 12V battery individually to full and then again in parallel to ensure that all 12V were fully charged before placing them in series?
Different battery manufacturers recommend different things. You'll rarely find more than 4 parallel strings. You literally need to be monitoring each individual 12V to ensure its not going out of range. You already need to monitor 12.
Are these flooded cells? If so, you need to be checking specific gravity regularly as well.
Ampster
Renewable Energy Hobbyist
FLAs are more sensitive than Lithium. They need to be fully charged frequently and Floated. That creates overhead that needs to be matched to the capacity of your panels to produce enough to do that.
I did charge them all individually before paralleling them using https://www.amazon.com/gp/product/B01F3R4SUW. I did use a 100amp tester to test each one before using. That's about all I've done
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sunshine_eggo
Happy Breffast!
Okay, so you charged them all to full in parallel? That's better than nothing. Doing it individually allows you to identify any outlier behavior.
Have you checked all 12 12V for voltage at peak charge, right before float? If so are all batteries within 0.05V of each other and below 12V charge spec?
Building on what @Ampster said, there's a range of "safe" charging for FLA/AGM. The amount of current you send to 300Ah of lead-acid should be about 30-60A in bulk mode. Some batteries have different ranges. My Trojans were 0.13C max, so I was limited to 39A. Your 3300W of panels could send 69A to your batteries if you achieve peak output.
Of course, the 30-60A is based on the new rating of the batteries. If they are degraded, charge limit should be adjusted accordingly.
Have you checked all 12 12V for voltage at peak charge, right before float? If so are all batteries within 0.05V of each other and below 12V charge spec?
Building on what @Ampster said, there's a range of "safe" charging for FLA/AGM. The amount of current you send to 300Ah of lead-acid should be about 30-60A in bulk mode. Some batteries have different ranges. My Trojans were 0.13C max, so I was limited to 39A. Your 3300W of panels could send 69A to your batteries if you achieve peak output.
Of course, the 30-60A is based on the new rating of the batteries. If they are degraded, charge limit should be adjusted accordingly.
