E34-2 Battery replacement/upgrade

There are 2 group 24 batteries under the bunk (and a dedicated start battery in the lazarette). They used to be good for several days - now 1/2 a day at best. The NewMar 20/35 charges them...some, charging with the alternator is the same result...some.

I'm trying to repair them with a NOCO genius charger.


The space is almost 14" wide. Will group 31 fit under the lid?

When considering purchase of new batteries some research is usually well worthwhile. Most battery sites give the dimensions, length, width and height, so you can determine if they will fit. Group 31 were too large for our boat, but your battery locker may be different. Group 27 may also be an option for you.
It's also important to determine what kind of battery is most suitable-- flooded wet cell (cheapest, but takes longer to charge and gives off gasses when charging, so not approved near sleeping quarters), AGM (more expensive, can be drawn down lower, recharge faster and don't give off gasses) or even lithium, though that gets alot more complicated. Adding a solar panel with appropriate controller can help solve some charging issues. The kind of charger (multi stage, amperage, etc) is also important.
Lots to think about....
Frank

My 87 e34 has two group 27 wet cell batteries in the compartment just under the mattress in the rear berth and I put one group 24 starting battery near them in the space one would normally go to service the packing nut or dripless seal.

I have 2 group 31 in the battery compartment on our 34-2 (1987).

Are the batteries old? Probably just need new ones--with a modern charger.

I'm a fan of AGMs, eight years and counting, originals still good. I never enjoyed digging into the battery compartment to check fluid levels.

"Group" is just the physical size, and yeah, they have to fit. I have made that mistake.