Adding batteries

[S.A.M.]

I want to add a battery to the port and starboard bank in case the genny goes out on me, that I have plenty of back up for 12v systems. Problem ,to me, is where to put them.

If I put them forward of the existing battery box, I cover my access to the midship bilgepump and the raw water strainers. If I put them to aft of the box, I'm afraid that they're to close to the genset.

Any suggestions or input?

[captainrob1985]

I have heard of and myself am running heavy gauge cable up an putting them in the galley cupboards, thus they are dry from bilge water and easy access.
Rob

[Paul]

Keep in mind that batteries give off dangerous gasses when charging and discharging. The cabin might not be the best place to put them unless you can ventilate them outside.

[wowzer52]

Paul is right, I have experienced four different battery explosions in my life. One was on a charger and a spark four feet away set it off and the explosion sent battery parts and acid everywhere. I'm glad I was twenty feet away but still got some acid on me that burned my clothes. Another was at my brothers feet on a charger when it went off, Heavy clothes saved him from the acid. Another was in a car, as I disconnected the battery cable the spark set it off. I was lucky it didn't get in my eyes, but I did loose my shirt. Another was in a boat engine compartment. For no apparent reason the battery just exploded and the engine room was covered with battery chunks and sulfuric acid. From those experiences alone I have learned to keep batteries (in my boats anyway) in a battery box in the engine room where the bilge blower can take away not only the gasoline fumes but the gases from a charging battery also. I don't like worrying about another battery explosion, especially on my boat where my family and friends are. I suggest that if you need more battery capacity and don't have room upgrade your batteries to the amp hours needed or service and maintain your genny often enough that you trust it.

[ready123]

If I put them to aft of the box, I'm afraid that they're to close to the genset.

Too close why?
My view would be to satisfy yourself on the reliability of your generator rather than to add batteries to existing banks. A genny should be easy to achieve comfort on it's reliability.... continuing your line of thought what kind of backup are you going to have for your engines? A bank of outboards on deck just in case?

Genny's like to be run frequently... run it each day you are out even if only for 1hr. I run mine morning and night to make my coffee's if nothing else.
Not sure how your Trojan's wiring is different to mine but my house lighting is from one engine's circuit not both. I also have a house battery for fridge, Inverter, stereo... I have left lighting on the engine circuit as I consider it low load in the grand scheme of things.
So I have a port engine battery, starboard engine battery, house battery, genset battery (isolated from everything but genny).
My charger handles the 3 initial batteries only... genny charges it's battery *only* as required in the manual.

[S.A.M.]

Thanks for the replies. But I guess things got confused.

The 10M has 3 batteries; the port controls the port engine and 12v circuits to that side. The middle battery is for the genset only and the starboard handles its side. I want to add amphours by adding a battery to the port and starboard.

Will there be too much heat produced by the genset to creat a safety issue if the batteries are about 12 inches away from it?

[wowzer52]

Thats what I would do.

[ready123]

Thanks for the replies. But I guess things got confused.
The 10M has 3 batteries; the port controls the port engine and 12v circuits to that side. The middle battery is for the genset only and the starboard handles its side. I want to add amphours by adding a battery to the port and starboard.
Will there be too much heat produced by the genset to creat a safety issue if the batteries are about 12 inches away from it?

I doubt the genset would run that hot.... Is the engine compartment that hot after running the genny?
OK so you have 12 V circuits on both sides... I would still suggest to put the high load items on a house battery that is apart from the engine batteries, that makes the chance of running down a starting battery less likely.... and you only need to buy one deep cycle rather than two. NOTE a pure deep cycle rather than a deep/starting (that would be needed on the engine circuit) will supply power for longer and also last for more cycles.

[Paul]

Hi Sherman,

I have a small engine bay and just having a generator really fills it up. For this reason one of my batteries is located about 10 inches away from the genny with no ill effects from a warm generator. At one point the generator overheated due to a water restriction and did not effect the battery.

I would say installing a battery 12 inches away shouldn't be a problem. I would suggest putting it in a battery box.

Hope this helps,

[S.A.M.]

Thanks for the input.

Don't think I want to rewire the 12v systems. I'll run the batteries in parallel to up my amp hours.

[ready123]

Thanks for the input.
Don't think I want to rewire the 12v systems. I'll run the batteries in parallel to up my amp hours.

Not really that difficult... the fridge is likely the highest draw and all you need to do is wire it's DC connection directly to the house battery with a fused connection.
If you don't want to do that why not just up the AH size of your existing batteries rather than adding two more... that will require much less physical space.....
One big is better than two in tandem, especially if you are mixing old and new together (age and size).... another thing to consider is 120V charging of those mismatched batteries, if you are treating each pair as two banks then nothing to worry about (a charging circuit to each battery, likely you don't have this capability), but if you are charging both on one leg then you are setting up a situation with negative potential.
These suggestions are things you should consider when spending the extra $$ to ensure you are in fact getting quality and reliability out of the modifications.
From where I sit I would not add two more batteries when I have a genny... I would focus on the genny if it is a weak link, though often they are not really a weakpoint when used regularly and maintained... they are in fact a very simple and low risk item IMO. My 30 yr old genny still performs and ensures I always have power should I need it.
The reason I am making this argument is that at the outset you wanted to add batteries in case of a genny failure not that your usage regularly runs the batteries down... which would be a reason to add Ah IMO.
Just some other things to consider if you are really wanting to rely on this upgraded system... you could add new batteries to old and end up with a weaker system than you have now.
Don't let the greater Ah number fool you into thinking you are buying safety... how you get to that higher Ah hour is in fact more important than just the raw number!
Oh and I have not even touched on considering the situation of the engine's Alternator charging system on these two batteries while underway!!
There is much more to consider here than just adding batteries

[S.A.M.]

All valid points. I have group 27s now, maybe blue top group 31s. Any bigger would not fit in the factory battery box. My battery charger has 3 independent charging banks, so that would have never been a problem.

[ready123]

All valid points. I have group 27s now, maybe blue top group 31s. Any bigger would not fit in the factory battery box. My battery charger has 3 independent charging banks, so that would have never been a problem.

How does three bank charger service 4 batteries, that is my point. With three bank charger I would go one for each engine battery and one for the house battery.... genny should charge it's own battery.
How do you plan to charge the 4 engine batteries with that charger? You need to put two one one bank thus creating a weak point. My concern is moving from a well designed system that seems to be working OK other than personal worry for 'what if' to a system that by design will have weaknesses. That would increase my 'what if' fear level and should not reduce yours.