I've built a 48V 280AH 16 cell battery for an emergency backup system for my house. Since it incorporates a 6000W split phase Growatt controller/charger/inverter, I decided to move my water well circuit off grid to give the system something to do between blackouts. The well barely consumes 4Kwh a month and my panels produce about 5Kw in full sun. My panels are broken up into 5 strings of 3 panels each connected through a combiner box with individual fuses on each string. It's a simple matter to enable or disable however many strings I need depending on how many kw I need for any particular load. One string keeps the battery at virtually 100% even with the well pump doing its normal duty. Here's the question. How important is it to allow the LIPO cells to do a deep discharge down to about 20% periodically and how often should I turn off all the panels and let the well slowly drain the battery? I'm pretty sure that to keep maximum capacity you need to "drain" your battery occasionally. I'm just not sure how important that is and how often it should be done. Advise from someone experienced in trashing batteries by keeping them perpetually fully charged would be appreciated.
Deep discharge schedule?
- Thread starter gnomie
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timselectric
If I can do it, you can do it.
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For a long life, they shouldn't remain at a full charge.
Cycling daily is the best option. But it doesn't have to be a deep cycle. Just get the cells below 3.4v so that they aren't constantly held in the upper knee of the charge curve.
Cycling daily is the best option. But it doesn't have to be a deep cycle. Just get the cells below 3.4v so that they aren't constantly held in the upper knee of the charge curve.
sunshine_eggo
Happy Breffast!
Not at all important. Zero need to ever do this.
+1 to @timselectric, and
I would leave the inverters on in full power mode to ensure they burn 80-100W continuously to cycle them nightly.
Charge to 55.2V absorption, float to 54.0V.
Thanks. I will probably let them run the well for a few days and keep an eye on the sum voltage. I can recharge the bank in a few hours on any sunny day.
sunshine_eggo
Happy Breffast!
Your inverter uses 1.9 - 2.4kWh/day just by being on unless you're using a power saving mode. IMHO, the overnight discharge of the batteries powering the inverters should be more than enough to prevent high SoC issues. If you're using power saving feature, turn it off and keep it simple.
timselectric
If I can do it, you can do it.
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As long as you don't use the grid to hold it at a high SOC. It should cycle just fine, on its own.
sunshine_eggo
Happy Breffast!
Most of the Growatt use charge on/off based on voltage in settings 12 and 13. If voltage is above settings 12, no AC charge. if it is, only charges until setting 13 is reached - then it terminates.
I'm assuming that's the case here. Should be a trivial matter to set #13 to something around 53.6V (3.35V/cell) to insure it never fully charges it.
