I currently have EverStart Maxx Marine Battery, Group Size 29DC batteries. I want to buy Optima blue top batteries. My problem is I am having trouble figuring out the right size to buy.  (equivalent size or better ) Any help would be greatly appreciated

 

Folks are going to want to know how you're using them, etc.

I have an electric only boat. The bow mount trolling motor is a 24volt and those are the batteries I want to replace for now. The area that the 2 batteries are stored in is a very tight fit and I want the blue top batteries for more accessibility

 

By Blue top I assume you are asking about Optima marine AGM's?

Tom

yes

you can't get them in an equivalent size capacity wise.

 if you feel that's what you must have, buy two of the biggest ones you can get that will fit in the space you have.   Look at the reserve minutes and get the highest number you can.

I've been doing a little research on these batteries,  trying to find the right ones. I'm wondering if I should just deal with an agm battery(size wise) ? they seem to have a better rc and ah. The only reason I was looking at the blue top battery, was because it was getting to be a hassle getting the wet cell batteries out to check the water levels every few week. am I correct in thinking, that they are maintenance free and will my Norco 4 bank charger able to charge a agm battery? 

Yes, AGM's are easier to maintain, and if you have having to disconnect and remove the batteries just to check levels, then AGM is probably what you need to look at.  With that said, I will also say I'm not a fan for the spiral wound AGM's. As for reserve minutes capacity, AGM's are not going to give the RC numbers a good, flooded cell battery will give, however, they should give you a much higher cycle count if properly charged and maintained.  As for the RC number, spiral wound batteries normally have the lowest, some a low as 165 minutes for a group 27/29 size battery where a similar size stacked cell AGM will give 200 (similar to a maintenance free flooded cell) and a flooded cell with the service caps will give 225.  Also, the spiral wound batteries had a much higher failure rate than the stack celled batteries, back when I was dealing with them on a daily bases. 

The reason the maintenance free flooded cell has a lower RC number than the one with caps, they reduce the size of the places to make room for more electrolyte.

Maintenance free is also a bad name for a battery also, they still require maintenance, keeping the terminals cleaned at least annually.

I would suggest, before buying a spiral wound battery, check out the stacked cell AGM's like Deka and other companies make.

I'm not saying the Optima is not a good battery, but I think you might find one of the major name brand stack cells give you better numbers.

VMax Tank marine AGM MR137-120 is close to group 31, check the dim's and specs.

Free shipping and 10% off sales from time to time. I have been using 2 of these batteries since 2005, same Norco charger. Have not taken them out of my boat, no maintenance.

Tom