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LastOutlaw
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# Posted: 7 Jan 2019 12:14
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I am setting up a solar system.
It will be comprised of four 300 watt panels wired as 2 panels in series as two strings then connected together in parallel. This will feed into a Midnight Kidd charge controller. The charge controller should charge my battery bank at the rate of 21 amps at 57.6 volts from this panel array setup.
Now I will be using eight Trojan T150 batteries with an AH rating of 225AH.
I have two choices as to how I wire this battery bank.
24 Volt or 48 volt
The 24 volt arrangement would be as follows:
Two strings of 4 batteries wired in series then connected parallel.
225AH x 2 = 450 AH @ 24 volts = 10800 watt hours.
The 48 volt arrangement would be:
One string of 8 batteries connected parallel.
225AH @48 volts =10800 watt hours
Would the charge rate of 21 amps at 57.6 volts be better suited for the 48 volt system @ 225AH rather than the 24 volt system recieving 21 amps at 57.6 volts for 450AH?
The other question is would two strings of 4 batteries charge more evenly than one long string of 8 batteries?
Because the panel wiring layout would have the Kidd operating at about half it's limit I prefer to keep it wired as it is designed above. This way later on I can double the panels and double the battery bank using the same charge controller.
Is my math correct? Also are my questions valid?
I think I'm better off with the 48 volt battery bank wiring but would like other's opinions on this.
Also once I expand, 4 strings of four batteries each in 24 volt sounds like too many strings whereas 2 strings of eight batteries as a 48 volt layout sounds more in line.
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creeky
Member
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# Posted: 7 Jan 2019 13:51
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I prefer 48v as the system efficiencies between solar controller and inverter add up. Albeit to around 3-4%. Lithium batteries add 20% so ....
Lead acid, from what I've learned, parallel strings are best kept to a minimum.
Your solar controller will change the 57.6vx21a to whatever the battery needs; therefor your amperage rises to 42a at 24v. If the kid handles 42a. Otherwise you're seriously over paneled.
I don't know the specs on the kid. 30a?
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LastOutlaw
Member
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# Posted: 7 Jan 2019 19:05 - Edited by: LastOutlaw
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Yup 30A... will be setting up the batteries at 48 volt.
I'm guessing that means a string of eight six volt batteries.
Also can not double the panels in the future without adding another controller or running a different one. This Kid is at 70% according to the sizing estimator on their site.
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