need help buying the "right sized" onboard charger

[keakar]

what is the "proper" charging amps (for each bank) to buy? i will be using two series 27 trolling motor batteries for a 82lbs. thrust 24v trolling motor

I have heard 10 amps to each bank is a good size to use and the formula says to use a charger that is at least 10% of the batteries rated amps which in this case is 875 so that would equal a 8.75 amp charger is needed.

i don't know if the formula is overestimating the needs so what im asking is, should I buy the 10 amp per bank chargers or could the smaller and more affordable 5 amp per bank charger do the job?

then there is the price, the 5 amp per bank charger cost around $125 and the 10 amp per bank charger run around $250

so is the 5 amp per bank charger ok to do the job well or would it be undersized and not good enough to fully recharge the batteries overnight to fish 2 days in a row?

the way I will be using this onboard charger is to plug it in to recharge right after a trip then not plug it in again except to do a quick refresh charge the night before I go.

I want to save money if i can but not at the expense of not fully recharge the batteries overnight (12 hours) to be ready for the second days trip.

[papap]

If you fish back to back days the 5 amp may not fully charge them overnight depending on how long you have to charge them.

[papap]

I went with a 3 bank charger. This way it fully charges the main battery also.

[keakar]

thanks, i'll go ahead and order the 20 amp 10/10 one then. I was pretty sure that's what I needed but I guess I just wanted reassurance before spending the money.

I don't need a 3 bank because the 2 trolling batteries are up front by themselves so a two bank charger is all I need.

I check the starting battery from time to time but it never needs charging because it is just for starting (Suzuki df40) so it doesn't get drained much and starting such a small motor doesnt take many amps so never needs recharging at home (but I do have another charger in case it ever does), the motor recharges it well enough when I use it and they have lasted 4-5 years that way. suzukis have better charging systems then a lot of other motors too so that helps.