need new batteries

[Viper]

Some may have had differing experience but in mine, and unless stats have changed recently, the lead acid design is still the best bang for your buck. AGM has it's place in certain apps where pounding is the norm and voltage drops aren't tolerated very well but other than that, in my experience with them, I still don't see enough of a longevity benefit to justify the additional expense. The technology is getting better and so is production so perhaps one day that cost to longevity ratio will improve.

[tomschauer]

The 355 and 356 have a shi**y battery system. Three batteries, mine are 31's. There is a single selector switch for two of the batteries, the third battery is dedicated to the genny. The position of the switch controls all loads, house and both engines. As factory installed there is no way to isolate house from starter loads. Soooo, either upgrade the system (where do you put the extra batteries so they aren't a PIA?) or get three good batteries, 1 starting for the genny and the other two most likely dual purpose or deep cycle, so if you do run them to near zero they will recover a FEW times. Alternate from 1 to 2 regularly ( i do every week) and if you ever use the both, make sure your genny runs so you can charge them when and if needed.

[Viper]

Source of the post .... There is a single selector switch for two of the batteries.... The position of the switch controls all loads, house and both engines. As factory installed there is no way to isolate house from starter loads.....

I'm a little confused; you say you have a selector switch, so your banks ARE isolated unless you have the switch on ALL! That's the purpose of the switch. One bank (#1) should be Start batteries that you switch to start the engines, the other bank (#2) should be Deep Cycle batteries that you switch to for house loads at anchor or at the dock. The two banks are isolated! It's not the ideal setup but you do have isolated banks, you just have to manage the switch properly.

Ideally, you'd have one Start battery bank per engine, and one house bank (3 banks total) ALL isolated from each other at all times with the ability to momentarily parallel two banks in case of a dead start battery. This does not include the generator battery. Engine charging considerations need to be addressed for properly charging three banks from two alternators and maintain isolation but there are creative ways of doing that. There is definitely re-wiring involved but it's doable if you're electrically savvy.

[tomschauer]

the banks are (or can be) isolated from each other. But you cannot isolate the engines (start load) from the house load. What ever position the selector switch is in feeds everything down stream, both engines and the entire house load.

[tomschauer]

I guess its a matter of opinion and boating styles. I personally do not care to continually switch from 1 to 2 every time I start or stop the engines, even if I did, I know I would forget sometimes. The way we boat, on a good day, could be five or more times as we move from raft to raft. All the while the refer, stereo, gps, vhf etc are running. Someday, I will add a second switch to separate start from house, and hopefully find some space for at least one more house battery.

[Viper]

Correct but you can still manage which bank you start your engines with and which bank you draw house loads from when the engines aren't running, and that's the key. If that ability is there, why not have a start battery and a Deep Cycle battery? You then have the best of both designs rather than the compromise of a dual purpose battery. The only circuit design I would consider using a dual purpose battery in is where one engine has its Start battery and the other engine shares its battery with the house loads but there is no selector switch in the circuit. Because you have to start that engine off the same battery that you run your house loads on, other than rewiring the system, you have little choice but to go with a design that can handle a bit of both types of loads.

[Viper]

Ya switch management is a pain, that's why I don't like them and prefer/recommend rewiring to isolate loads with their own banks. The "ALL" position is also the cause of many emergency calls because of dead batteries on the water....I don't like those switches because of the "forgot to switch back." A lot of manufacturers are moving away from that design because of it. It just costs them more to build but they pass that expense on anyway. But you're right, it really is a matter of preference. I prefer not to have to remember managing a switch.

[Reelpriority]

We just replaced all three batteries on our 1999 Carver 356 with new flooded Trojans SCS225. The Charles Battery charger in the 1999 era Carvers will only charge GEL or Flooded batteries. Carolina Eneregy recommended the Trojan SCS225 or Deka 8G31MDT GEL. AGM Batteries will not be compatible with the Charles Marine charger assuming your Carver 356 has the original factory charger.
The Trojan batteries are very heavy and you will need to utilize a dock line to lower the batteries in place. You may want to get a mechanic for this remove and replace project. Not a lot of room to maneuver.

[mjk1040]

Personally I have no problem with the battery configuration on the 355/356's. It's manageable by all means, and installing anything else would surely be a PITA! Maybe as an after thought Caver should have used the genny battery as the house battery and not the engine batteries. Maybe the installation of a solar maintainer charger would be a more meaningful install then a bank of expensive, heavy batteries? What ever happened to the KISS method? Keep It Simple Stupid! IMO!!

[bud37]

So I am jumping into the bath here........as has been mentioned the factory battery wiring only provides one battery to start both engines at a time unless you switch between starts......so why not just use a dedicated start battery , you will have to switch after start but here is why I see it working.The alternative as has also been mentioned above is all the Blue seas stuff ( read, real cool but also real expensive ).

If you check out the hard wired loads to the battery sides of the switch for your boat , you will find a difference between bat1 and Bat2....the one with the most load that can not be controlled manually would be the one selected to choose as house, that way there is always a start available. I know there are space issues with some but that side would be where to put the extra bats.
Easy way to see if you have make before break battery switch, put radio on and then switch from 1 to all to 2, if radio stays on seamlessly it is make before break and battery switching is safe to do with the engines running, just don't switch to or thru OFF.......