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Old 04-26-2021, 05:34 PM   #1
Mini-Skoolie
 
Join Date: Mar 2021
Location: Montreal, QC
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24V system review

Hi,

Please review my system to be 100% solar. Based on many videos I have seen!

16 x 12v, 280ah batteries 2 x 8 in series then paralleled for 24V, 560ah or 13,440 wh.

8 x 400w solar panels, 40.8v, 9.81 amps. 4 x 2 in series then paralleled for 81.6v and 39.24amps

Growatt 3kW 24V Inverter 120V Growatt 150V 80A

Might be tempted to go 48v depending on your suggestions!

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Old 04-27-2021, 12:31 AM   #2
Bus Geek
 
Join Date: Nov 2016
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8 series strings in parallel is a horrible design, uneven current flows will greatly shorten longevity.

Any paralleling if needed should be at the 1S voltage level, not paralleling strings at higher voltage.

Look for single cells over 100Ah, 200+ even better.

If you need to parallel strings, 3 in total would be maximum, fewer the better.
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Old 04-27-2021, 06:13 AM   #3
Skoolie
 
Join Date: Oct 2018
Location: Georgia
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At this scale consider lithium batteries. You will get better high drain performance and more usable energy out of the pack. Costs are now similar to Lead if you hunt around for a good deal.

Or to avoid the parallel issue, just get 2V cells and get 12 of them, that's fewer batteries total and no parallel issues.
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Old 04-27-2021, 08:42 AM   #4
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Quote:
Originally Posted by Ben3361 View Post
Please review my system to be 100% solar.
Hard to do without knowing your requirements (loads), sounds like you've done some homework.

Quote:
Originally Posted by Ben3361 View Post
16 x 12v, 280ah batteries 2 x 8 in series then paralleled for 24V, 560ah or 13,440 wh.
As others have stated, parallel first, then series.

What stands out to me is this:
Quote:
Originally Posted by Ben3361 View Post
8 x 400w solar panels, 40.8v, 9.81 amps. 4 x 2 in series then paralleled for 81.6v and 39.24amps

... Growatt 150V 80A
The charge controller needs to support more than 80A. You say 81.6V/39.24 amps, but that's solar input. The charge controller converts this to a 24V charging voltage, which means it ups the amperage- 400W * 8 panels is 3200W, 3200W / 24V is 133A. You would need a solar charge controller capable of 133A, the 80A charge controller would only support a little over half your needs at 24V.

Quote:
Originally Posted by Ben3361 View Post
Might be tempted to go 48v depending on your suggestions!
The above is a good reason to consider 48V. 3200W / 48V is 66A, which would be within the specs of the charge controller you listed.

My rule of thumb for system voltage selection is the 100A threshold- if you're ever charging or discharging regularly at or around 100A, its time to consider a higher voltage.

No experience with Growatt stuff, I always recommend looking at Victron Energy's offerings. Again, consider lithium especially given the size system you're thinking of building, economical options are available.
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