Your question is sort of like the old threads
what is your favorite--
You will get lots of opinions.
You don't mention what kind or number of batteries you have.
1 or 2 12v?
2 deep cycle 6 volt?
There are plenty of chargers out there that have 2 or 3 ranges.
Just get one that's fully automatic--ie it will automatically charge
and then go into "float charge mode" and finally shut off altogether.
I have a 2/10/25 amp charger like this one--
Amazon.com: Black & Decker VEC1095ABD Smart Battery 25/10/2 Amp Battery Charger: Automotive
This is a high frequency charger that's transformer-less. This means it's
quite a bit lighter than the old fashioned chargers. It might also be less
resilient but I've had good luck with mine. Some of the online ratings
are good and some are bad for this charger so I'm only recommending it
with some reservation.
For keeping them charged while in storage I firmly recommend a
These guys have the absolute lowest online price and free shipping.
Battery Tender SUPER SMART BATTERY TENDER JR. from Derby Cycles
and they're just down the road from me.