Battery Question

[mjsmjsb]

I recently purchased a used 1987 Hunter 31. The batteries have been located in the rear berth, Surveyor noted that this was not a good idea and should be moved.
Having looked at several Hunter 31's I have seen batteries everywhere, in the storage lockers aft of the cockpit, in the are under the lazaretto, right behind the engine under the rear berth.
So my question is 3 parts.
1. There are 3 batteries a pair of 6 volts in series for the engine and a single 12 volt House. Can I add another 12 volt to the existing 12 in a series set up. 2.
2. Can I relocate the present setup to the area under the lazaretto, which will add about 6ft of cabling?
3. Will the alternator be able to continue to charge a larger bank?
When in port there is a battery charger that is tied to shore power that can handle another battery, (not needed if it's parallel right?)? I know a question within a question.
In closing 'nothing' that the previous owner did was done to better the boat. Everything has sat for almost 18 months never leaving it's berth, clean under and in but not behind the systems.
So a system by site rebuild I do. Any help is appreciated.

[Pete7]

Why did the surveyor suggest they should be moved?

Are you sure there are 2 x 6v engine batteries and 1 x 12v house? Normally they are the other way around. I think you mean add another 12v battery in parallel to the house bank, not series.

Yes they can be moved and if the battery cables are the correct size then the alternator will cope.

[Cheechako]

Originally Posted by mjsmjsb

I recently purchased a used 1987 Hunter 31. The batteries have been located in the rear berth, Surveyor noted that this was not a good idea and should be moved.
Having looked at several Hunter 31's I have seen batteries everywhere, in the storage lockers aft of the cockpit, in the are under the lazaretto, right behind the engine under the rear berth.
So my question is 3 parts.
1. There are 3 batteries a pair of 6 volts in series for the engine and a single 12 volt House. Can I add another 12 volt to the existing 12 in a series set up. 2.
2. Can I relocate the present setup to the area under the lazaretto, which will add about 6ft of cabling?
3. Will the alternator be able to continue to charge a larger bank?
When in port there is a battery charger that is tied to shore power that can handle another battery, (not needed if it's parallel right?)? I know a question within a question.
In closing 'nothing' that the previous owner did was done to better the boat. Everything has sat for almost 18 months never leaving it's berth, clean under and in but not behind the systems.
So a system by site rebuild I do. Any help is appreciated.

-I agree with Pete, usually the golf cart batteries would be for the house. You don't need deep cycle for the engine start.
-There are a ton of boats out there with batteries under the berth. I don't get what your surveyor is driving at. Unless an insurance requirement I would leave them.
-Yes you can add a battery in parallel.
-The alternator will charge a larger bank, how well depends on how many amp output the alternator is.

[RocketScott]

+2 on the house/start configuration explanations posted above

The problem with batteries in a berth are fumes. If something goes wrong with the charging system they can produce hydrogen sulfide, which is poisonous

I have no idea what the odds are of that, or how concerned we should all be, but that's why it was pointed out

[boatpoker]

Originally Posted by RocketScott

+2 on the house/start configuration explanations posted above

The problem with batteries in a berth are fumes. If something goes wrong with the charging system they can produce hydrogen sulfide, which is poisonous

I have no idea what the odds are of that, or how concerned we should all be, but that's why it was pointed out

I've also seen a battery explode and cover everything in the cabin with sulfuric acid.

https://www.yachtingmonthly.com/arch...-avoid-it-3930

[ranger58sb]

AGMs generally off-gas less than normal flooded lead-acid batteries. A common use case is when they need to be located within living spaces.

Lifeline, and maybe others, do make 6V AGMs. Not as inexpensive as FLAs, but then it might head off a relocating/rewiring project.

-Chris

[Pete7]

Originally Posted by ranger42c

AGMs generally off-gas less than normal flooded lead-acid batteries. A common use case is when they need to be located within living spaces.

Lifeline, and maybe others, do make 6V AGMs. Not as inexpensive as FLAs, but then it might head off a relocating/rewiring project.

-Chris

I will accept that, but is this down to the lower charge voltage say 14.4v rather than the 14.8v you can charge FLA? all be it at the cost of some water which needs topping up.

The problem with AGMs is there not great house batteries. We have AGM as the engine start, but will use other types for the house bank.

Just going back to what RS said, hydrogen sulfide stinks and normally a quick indicator of battery problems. We had a UPS go nuclear at work in the server room. the outside steel case of the UPS was so hot I couldn't touch it. The smell from boiling acid inside the AGMs alerted us to the problem even when walking down the corridor. We used a pallet truck to put the UPS outside in the carpark over night.

On board like a lot of European yachts, we sleep on top of the batteries. Indeed my head is separated by a piece of foam and 3/4" of plywood. Perhaps totalling 8" with a pillow.

Pete

[ranger58sb]

Originally Posted by Pete7

I will accept that, but is this down to the lower charge voltage say 14.4v rather than the 14.8v you can charge FLA? all be it at the cost of some water which needs topping up.

The problem with AGMs is there not great house batteries. We have AGM as the engine start, but will use other types for the house bank.

Each maker has their recommended charging regime, you just have to check. I didn't much care what the bulk voltage value was, only that our charger set-up and their specific batteries were well matched. Current seemed more important than voltage for speed of charging, so 60A at 14.whateverV seemed faster than 40A and the same 14.whateverV.

I'd guess most 12V AGMs on the market are either starting or dual-purpose batteries, so not perfect for house.

OTOH, there are 6V AGMs, and some 12V AGMs, purposely designed for deep-cycling. Lifeline's deep cycle 6V and 12V batts, for example, pretty much have the same cycle curve as anybody else's 6V batts, for example. Firefly Carbon Foam AGMs probably another decent example.

IOW, there are AGMs and there are AGMs... just as there are differences in wet batteries.

-Chris

[mjsmjsb]

Originally Posted by Cheechako

-I agree with Pete, usually the golf cart batteries would be for the house. You don't need deep cycle for the engine start.
-There are a ton of boats out there with batteries under the berth. I don't get what your surveyor is driving at. Unless an insurance requirement I would leave them.
-Yes you can add a battery in parallel.
-The alternator will charge a larger bank, how well depends on how many amp output the alternator is.

Thank you guys for the help. now to build a small bank adding a 12 to the 2 sixes. Presently all batteries are in plastic battery boxes. I believe the surveyor recommended they be moved as they are presently next to the rear berth, reach out and touch them. So yes they will be moved probably to the starboard storage area, behind the galley next to the engine.

[boatpoker]

Originally Posted by mjsmjsb

Thank you guys for the help. now to build a small bank adding a 12 to the 2 sixes. Presently all batteries are in plastic battery boxes. I believe the surveyor recommended they be moved as they are presently next to the rear berth, reach out and touch them. So yes they will be moved probably to the starboard storage area, behind the galley next to the engine.

Adding a 12v to the existing bank of two six volts will drag the new battery down to the same level as the older batteries.

Best practice is to have all identical batteries of the same age in any bank.