What is the best max solar charging voltage for a car battery?

[wdc]

Hello, I have a 5 years old used car battery of 70 Ah and 4 solar panels connected in parallel giving 8A aprox. and today my charge controller (CC) is set to 13,8V max to charge, I want to change this setting to achieve maximun solar charge in winter (right now it's spring here), I think 14,8V should be a good value but maybe higher is better. My CC is the cheap chinese blue one from ebay. Any advice?

Thanks in advance.

[Mike90250]

How low do you take the battery on a daily basis ? 8 A of charge is a good point for a 70ah battery.

[wdc]

How low do you take the battery on a daily basis ? 8 A of charge is a good point for a 70ah battery.

thanks, I guess about 12,4V.

[Mike90250]

What is the voltage shortly after the sun goes down and charging has stopped ?

Generally a car charges at 14V, I'd not go higher than that voltage.

How often do you have to add water to the battery cells ?

[wdc]

What is the voltage shortly after the sun goes down and charging has stopped ?

Generally a car charges at 14V, I'd not go higher than that voltage.

How often do you have to add water to the battery cells ?

thanks, about 12,7V
I read somewhere that you can charge a car battery up to 16V and high voltages are good because they are made to charge very quickly.
not very often, once a year maximum.

[Mike90250]

Here's the generic lead acid battery voltage chart

battery-state-of-charge LeadAcid.jpg

[wdc]

Here's the generic lead acid battery voltage chart

battery-state-of-charge LeadAcid.jpg

Thanks! I've decided to charge my battery at 14,1V in summer and 14,7V in winter, this way I can charge it fast and avoid losing too much electrolite.