It would make more sense to ask how much current you need to effectively trickle charge the battery in question and then look at a panel that can generate that sort of current. When I looked into it for a motorbike it got confusing because of the electronics needed to monitor the charging.
I've gone over to a lithium battery and the combined weight loss and high starting amperage is noticeable on a big cylinder boxer. So far I've had no drop in battery condition with very minimal use. I've not had it on there long but so far I'm pleased with it. Main downside is the damage caused by fully discharging but you can get a battery condition monitor to connect with your phone to keep you on top of that.
I assumed you were interested in car batteries because of the other thread.
It would make more sense to ask how much current you need to effectively trickle charge the battery in question and then look at a panel that can generate that sort of current. When I looked into it for a motorbike it got confusing because of the electronics needed to monitor the charging.
I've gone over to a lithium battery and the combined weight loss and high starting amperage is noticeable on a big cylinder boxer. So far I've had no drop in battery condition with very minimal use. I've not had it on there long but so far I'm pleased with it. Main downside is the damage caused by fully discharging but you can get a battery condition monitor to connect with your phone to keep you on top of that.
I assumed you were interested in car batteries because of the other thread.