Mixing batteries?

[JSailer]

Hello,
I need to know if it is ok to replace an existing (bad) 12v wet cell battery with 2 golf cart batteries while still keeping a 12v wet cell starting battery?
If so, is there any particular wiring issue or simply put the 2 6v in series?
Thanks.

[KindOfBlue]

Do a search on this site for battery and you will find a thousand different configurations, most of which are supported/correct. I think that the answer depends on how you plan or if you plan to have the existing wet cell connected to the golf cart (also wet cell) batteries.

I don't think that you can simply just slide the 2 new new batteries in series into place as it charges at a different rate than the existing battery.

[k1vsk]

the simple answer is that you are fine if you isolate the new batteries as a house bank and use your good 12 V as a start battery and don't try charging them as a group unless your charger is properly configured to differentiate.

Some chargers can't tell what or how many batteries are in line and charges them regardless of their individual state.

[chucklesR]

In the should and could category, you SHOULD have a bank of batteries that are composed of the same type and same capacity, ideally the same age batteries.
You could mix them up, doing so will cause them to charge and discharge badly (meaning damage them).

[xort]

What you should do is buy Nigel Calders book; complete guide to sailboat maintenance and repair. He goes into great depth on battery use, charging, configuration, etc. etc. etc. Everything you'll need to know. Well laid out in detail with all the facts and figures.

find out the real experts opinion.

[chucklesR]

xort,
I just parrotted Nigel's opinion. He is my source of knowledge for all things electrical and mechanical on a boat.

[camaraderie]

I am assuming the 6v batteries are wet cells as well.
You may simply substitute them for the dead 12V battery and wire them in series. There is NO issue as the regulator sees them as the same 12V load.
This assumes the existing starting battery is is excellent shape. It is not a good idea to combine a battery on its' last legs with new batteries.

[sailingdog]

Should be fine.

[JSailer]

Wow, you guys are fast. Way to end the year!!!
Thanks.

[JSailer]

Ok, I guess I'm not quite done with this...
After reading more on the deep cycle batteries and going through Don Casey's book, I have further questions:
I will be using the house battery for the usual day sail requirements and occasional weekend overnight (anchor lights, water pump and eventually car stereo) in South Florida.
Since my motoring time is very short, I am worried I won't be recharging the battery enough between overnights (I currently do not have a way to chahrge the batteries at the dock). I do not know my alternator's capacity but will check on it later on. (Atomic 4, on a 30' O'day).
So, should I look into other types of batteries? I'm looking at the Dual Purpose batteries sold at WM.
Also, is an AGM for house ok if I have a wet cell Starting battery? I'm thinking not but I want to make sure as many batteries I see advertised seem to be AGM.