Generator Battery

[Yacht Jim]

Hi Everyone.
I could use a little help and advise. My Onan generator on our 1977 46C does not have its own start battery and I'm thinkin it might be a good idea to install one. My questions are; Where is the best place to locate the battery. What size would be best. What is the best way to charge the battery - should I get a alternator, separate charger or what. The current charger is for 2 banks. How do I go about wiring the battery selector for 1,2,all scenario - do I need a new selector for 1,2,3,all? The gen set is in a sound shield, could I mount the battery on top.
I just ordered new WEMA sensors and gauges for all the tanks. Once they are installed I will report how good/bad/indifferent they are. I'm looking forward to knowing the actual tank level on the flybridge. Thanks for your help.

 

[REBrueckner]

What makes you think so?? What are you trying to accomplish??

That's a lot of time consuming work. Why not add a larger house bank and use that for appliances and your genny?? or do nothing....an alternative is to carry a small portable generator aboard, like a 1 or 2 KW HONDA, and if you ever go dead, just start it up for recharge...lots of options depending on your objective. One way to avoid bad batteries, is to replace port and stb engine banks at different times, say two years apart, then you'll always have a recent bank....

What generator do you have..the manufacturer will specify the cranking amps required....you don't need to match CCA, that's for a zero degree start, very unlikely.....a group 24 auto battery should be fine, but I'd use larger if you find space. Why not use an 8D if that's what's in your start bank??

The simplist way to charge another battery which you want isolated is to add a battery combiner...like the PATHFINDER, which automatically connects your start battery to,say, your port bank during charge and disconnects automatically when the charge is removed...it's not the least expensive but allows you to select connect and disconnect voltages....

Yandina used to make the West Marine combiner, now Defender sells Yandina directly: http://www.defender.com/realproduct.jsp?path=-1|328|51495|606044&id=1349491
Yes you'd need a new 1,2,3 switch...or a pair of battery jumper cables which are useful to have aboard...

 

[Yacht Jim]

Rob, I appreciate your reply and insite. I guess what I'm thinking is that if my start/house batteries went tits up I'd be stuck. 2 "D's" for each side. So I thought adding a separate start battery to the gen set would be the right way to go. I realize the PITA it will be to set up but didn't consider the total cost. Your idea of a small portable generator isn't bad, I'll investigate that angle. This is a Onan generator in sound shield and there is not a great deal of "spare" room available for the battery and alternator. Thanks, Jim

 

[Yacht Jim]

Rob, I looked up the Yandina. Never heard of this idea but it sounds like a viable option as well. Thanks again for the info. Jim

 

[REBrueckner]

I do not know how you use your batteries nor how much but a way to avoid losing all battery power is to never parallel your port and starboard banks.
I assume you have a battery paralleling switch...but if not or if you worry that could fail, a pair of auto jumper cables are a nice security blanket to carry aboard...I actually used a pair one time....

When at anchor for extended periods, I often had to run my 15 KW Onan to heat water and charge batteries simultaneously....about 30 minutes daily...that's one way to avoid dead batts. I also carried a 4KW pull start portable gas genny in the cockpit of my 1972 48 YF and loved it....could charge batteries also in 30 to 40 minutes daily. I had a box shaped soft cover and ran shore power cables aft from my shore power connectors...so I could start it up and have in plugged in within a minute...in summer, it kept heat OUTSIDE the boat and helped keep it more comfortable in my salon.

 

[spartonboat1]

I entirely agree with the dedicated genset battery- it would dramatically reduce the chance of being caught with dead batteries. I intend to do the same thing and will be using a Group 24 or 27 AGM battery, which are long lived, and resistant to abuse. They can be drawn to zero volts and recharged without issue and can be mounted upside down, if necessary; or at least they can operate for a time at any angle.

This is for an Onan MDJE 7.5Kw.

 

[captbuddy]

It has already happened to me. Several times. I have 3, 8D's for the house & port engine and 1, 8D for the starboard engine and the gen set. Have had to use the parralle switch several times because I used up my house bank or either I started the gen set to charge the bank back up. Also have 4 golf cart batteries for my inverter. I would not want my gen battery tied to my house bank.
captbuddy

 

[Genesis]

Get an AGM battery; look at the primary cable sizes to figure out how big you have to go. You'd be surprised how small it can be and work - remember, it just has to be able to roll over the generator in reasonable conditions - a 0F start ("CCA") is, as mentioned, rather unlikely in a boat.

A small Optima RedTop will work fine. Get a Yandina combiner and tie it to the NON-HOUSE side so if the alternator on the generator fails you still get recharged, and you're good. This also gives you emergency boost capability if for some reason the Optima fails - you can still start the Genset.

With a COMPLETELY DEAD battery system the easiest engine to start is the first one you need to get running, as once you have one engine running you will eventually be able to start the rest of them. For most powerboats this means the genset is the priority.

 

[Yacht Jim]

You guys are all GREAT. really appreciate the help.
So I go out and get a battery, box, cables etc. and hook it all up. Then go pick up the alternator, bracket and new belt and hook it up. How does the Yandina hook into the system? Are there any special need to know items with it?
thanks jim

 

[jim rosenthal]

You might also think about two separate banks- one for engine start, which would start either of the engines, and one for house, which would only help start the engines if you hit the parallel switch. Also dedicated genset battery.

That is the way I had my Hatteras rewired, and it has worked out very well. I have two Group 24s in parallel which just start the engines- they are Trojan 24s and have held up very well. All they do is engine starting, and they are not deep-cycle batteries. I have a separate bank for house- used to be two 4Ds, but is now two Odyssey AGMs which are slightly smaller and have more punch than flooded 4Ds.

Odyssey batteries are quite a bit better than Optimas. I would recommend them without reservation. A small Odyssey like a 625 will easily crank over a medium-size diesel genset. It will crank a high-compression 427 Ford, so it will easily start an Onan.

I spent a fair amount of money to accomplish the above conversion, but it has been worth it. It also includes a battery combiner called an EchoCharge, and smart regulators on the drive engine alternators. The battery charger is a Xantrex that will charge three banks- the start, house, and genset batteries. Everything has held up well and I have not been stranded yet. Good luck on all this.

 

[Yacht Jim]

Thanks Jim. appreciate the input. At lease now I have some excellent ideas and related parts.
Jim

 

[Fanfare]

I have had Onan and Phasor generators on boats, and all of mine have had a 12v battery charger for their own generator battery built in. These chargers did not have the high capacity needed for our ship's systems, but could handle their own battery and were regulated for continuous running. Your generator wiring diagram will show whether you have one too. Could save you a lot of trouble!