Solar crunch time! Please review my plan.
I would like begin my first post with a big thank you to all who have shared their knowledge and experience on this forum. Without that, I probably wouldn't be entering the solar jungle! I hope yo...
Forum Discussion
pianotuna wrote:
Hi BFL13,
No, the four battery bank will require more amp-hours to get to 100%.
You already know this from the generator days. No one does 90% to 100% using a generator because it is not cost effective because the charge tapers.
Since above 85% there will be no more than about 12.5 amps per 100 amp-hours going in. As the bank gets closer and closer to 100% there will be more and more loss. The loss may be around double for four jars vs two jars.
Whether that makes a difference in 'real life' situations or not I could not say without a careful experiment.BFL13 wrote:
Each needs the same AH to get to 100%. Assuming the solar can do that many AH that day, the time is the same, the AH is the same, so the amps must be the same.
Same amps, same size solar array.
So now you are saying the four batts will need more amps (and so a higher wattage array) than the two batts to cover the "higher" losses to do the same AH in the same time. This is a 180 in your story!
However, the acceptance rate in absolute amps (twice the amps actually) of the four batts is higher at high SOC than the acceptance rate of two batts at the same SOC and voltage, and with half the charging rate, the four batts will get to a higher SOC before tapering, and they started at 75% instead of 50% so IMO there will be no difference to get to 100. A lab test to show what really happens would be good though! :)
The assumption is the solar amps will be at least the acceptance rate all the time to 100% in both cases. But against that is the controller itself dropping to Float voltage up in SOC somewhere, that costs you amps delivered that the batteries might still take. Let's assume the controller will stay at Vabs to 100% SOC in both cases, to remove that side-issue.
(My Eco-Worthy controller will not co-operate in that. It drops to Float voltage as soon as it reaches Vabs, so I set Float as close to my Vabs setting as it will go to get longer in the day at the higher amps. IMO it would still be a wash even with that controller)
