Let's Revisit Batteries

[Shaka 146]

It's been a while since we have addressed this subject. I have two Group 29 MAXx dual purpose batteries from Walmart. They are good for about a year and a half and their time is up. I'm debating on just getting a couple more wet batteries from one of their competitors or maybe a couple of Blue Top Optima dual purpose. So what are you guys using these days? Are people going for a cranking/deep cycle combination or going with two identical dual purpose batteries? What group (27,29,34) are you using?

My batteries need to last for week long Powell trips. I don't do a lot of sitting around with the stereo cranked up (maybe an hour every so often) and I really haven't had a problem with battery depletion while down there. 

Edited April 30, 2018 by Shaka

[Hein 63]

We just replaced two 12v wet cell batteries (one had a shorted cell) with two group 24 FullRiver AGMs from NWbattery Supply in Portland.  We use and recommend Full River batteries in our van builds.  Guessing the AGMs were 15 lbs heavier each. I do like that fact that an AGM can be turned upside down or the case punctured (not recommended) and no significant amount of acid will leak out. They do require a more sophisticated 4-stage maintenance charger. We like Ctek for those. Price was considerably more than what I could have scored at my favorite warehouse store.

The previous owner relocated the batteries to in front of the kick panel and added a Perko switch. The cables were a joke so replaced those with 2 gauge welding cable with hydraulically crimped lugs. (say no to hammer crimper.) We carry another fully charged AGM (larger size) on the opposite side for emergency use (jump start, trolling motor) and weight.

Edited April 30, 2018 by Hein

[Jlagos 23]

I'm sure others will pipe in who know alot more than I but if i prefer to select the battery for the specific purpose. Cranking to start the engine, and a deep cycle for the radio and accessories when floating. I would imagine the deep cycle, as opposed to dual purpose, is able to tolerate the constant discharge/charge cycles better having thicker plates. Do your batteries sit sometimes in a partially discharged state or do you completely discharge your batteries prior to recharging? Both scenarios will kill batteries more quickly. I get the deep cycle with the highest Reserve capacity I can find locally. I have heard the Duracell batteries at Sam's are made by a very good brand (can't remember which manufacturer). I have thus far just purchased the flooded and have had pretty good results. I too do not have a huge sound system that requires multiple batteries and am often moving when on the water. Not sure why your batteries are lasting only 1.5 years I would have thought longer.

[Nick213 583]

I used 3 interstate group 29 batteries in my avalanche and if you recall the system I had in that boat was ridiculous with 6 amps and over 7000 watts. I'd go on week long lake trips without recharging them on shore power. 

[Wylie_Tunes 146]

A lot depends on the switch type and how the banks will be used. if one plans to drop anchor and power up house loads for extended periods and on a regular basis, I would suggest a more true house bank over a dual purpose battery. 

Most any quality group-24 marine is more then enough for a cranking battery. A g-27 gives you a bit more cranking amps if you like.

The size, in terms of amp/hours, will depend on the potential draw and how long you want to have the loads going. I like to get pretty liberal on the amp draw here. You end up with a padded Ah number. The extra capacity prevents the bank form being draw too deep. More batteries cycled shallower will last longer then less batteries drawn deeper. 

Next up is shore charging. The larger the battery capacity gets, the more you need to rely on shore charger and not on the alternator. 

For the money, there are better AGM's then the optimas. They are rated at 75Ah. The same group size wet cell is going to be 100+ ah and likely half the cost. Other AGMs in that size are going to be 100-125 Ah. 

Depending the end needs, a pair of 6V golf cart batteries is a very efficient way to get in the 250Ah range. 

[Shaka 146]

It turns out that my cranking battery is fine. (Duracell going on its third season.) It's my accessories battery that looks like it has a bad cell. I'm going to replace it with a wet deep cycle and call it good. It looks like a lot of folks like Interstate so I'm going to try and fine one of those that fits the bill. If not another Duracell.