Adding another 2 house batteries....Need suggestions

ready123 · Post by **ready123** » Wed May 13, 2009 11:52 am

jwrape wrote:What do you mean one large battery? What type do you recommend? Would I need a different charger? Is it something I can find local or have to order?

First thing to do is calculate what amount of power you need..... how much electricity do you require for how long. Then that information defines the size of battery. Now you decide what kind of battery you want... flooded acid, gel, Absorbed glass mat etc:

Modern batteries (any really) do well with the new microprocessor chargers. Does your charger have a switch to handle different types of batteries? I would expect not.
Look back at my prior post with a link to Lifeline batteries to see what I use... spend some time reading that site and you will have a better appreciation for the things you need to consider for house supply.
I went the AGM battery route because it stands up to frequent discharge/recharge best and can take fast recharges so less genny time(high power, my charger is 40 Amp).
Start reading here for info on the kinds of decisions you are asking about http://www.lifelinebatteries.com/

I happily charge mine from the genny when out for several days...

jwrape · Post by **jwrape** » Wed May 13, 2009 12:36 pm

jav wrote: There's also one other thing I didn't bring up (and others but this would become a novel) but you need to be aware of it. When working with larger capacity banks- you need to consider your charging methods. Hooking up the genny start circuit and ALTERNATOR to a 400+ amp hour bank is going to stress the hell out of it's alternator. That alternator was was likely designed to replenish a starting battery, which is very light duty charging since it only needs to replenish 1 or a couple of start cycles. Now it's going to be asked to charge this large battery bank that, at only 10% discharged, is going to put about 400% more load on the alternator. Smaller amperage wall chargers will also be stressed. Ideally, you want a decent 3 stage charger with a built in equilizer to get the most out of a marine battery or bank of batteries.

AS for the charging of my house and generator batteries, they are only charged by either the mouted on board charger via 110v either shore power or generator power so no altenator involved in charging the battery bank I am contemplating upgrading. The engine batteries are charged from the motors and are isolated from the house. Should be fine.

jav · Post by **jav** » Wed May 13, 2009 12:56 pm

jwrape wrote: AS for the charging of my house and generator batteries, they are only charged by either the mouted on board charger via 110v either shore power or generator power so no altenator involved in charging the battery bank I am contemplating upgrading. The engine batteries are charged from the motors and are isolated from the house. Should be fine.

So your genset has no alternator for it's starting battery?

jwrape · Post by **jwrape** » Wed May 13, 2009 12:57 pm

jav wrote:
jwrape wrote: AS for the charging of my house and generator batteries, they are only charged by either the mouted on board charger via 110v either shore power or generator power so no altenator involved in charging the battery bank I am contemplating upgrading. The engine batteries are charged from the motors and are isolated from the house. Should be fine.
So your genset has no alternator for it's starting battery?

Oh, don't know...... If it does I have never seen one unless it's a generator type thing that is on the starter. Ya know it might have one but it might be on the far side of the beldge where I can hardly get to.

jav · Post by **jav** » Wed May 13, 2009 1:15 pm

Most will have some sort of built in charger to keep the starting battery fresh. Whenever the Gennie runs- it will try to top off that starting battery. Except in your case- your "gennie start wires" are attched to the house bank. So- your out on the hook and realize your house bank is getting low and start the genset (using the house bank). The moment the genie starts- it's "starting battery charge cicuit" is live and connected to this huge bank that's maybe at 50-60%.

My 440 AH bank can consume over 100 amps at this state of discharge. That's going to max out the charge circuit and dependin on design, may or may not pose some problems. I know the new Kohler 5K gennie is limited to 15 amps on the charge circuit and it's driven off the flywheel/ignition circuit. I beleive there is an inline 25A fuse that would likely blow in this application?

jwrape · Post by **jwrape** » Wed May 13, 2009 1:17 pm

jav wrote:Most will have some sort of built in charger to keep the charging battery fresh. Whenever the Gennie runs- it will try to top off that starting battery. Except in your case- your "gennie start wires" are attched to the house bank. So- your out on the hook and realize your house bank is getting low and start the genset (using the house bank). The moment the genie starts- it's "starting battery charge cicuit" is live and connected to this huge bank that maybe at 50-60%.

My 440 AH bank can consume over 100 amps at this state of discharge. That's going to max out the charge circuit and dependin on design, may or may not pose some problems. I know the new Kohler 5K gennie is limited to 15 amps on the charge circuit and it's driven off the flywheel/ignition circuit. I beleive there is an inline 25A fuse that would likely blow in this application?

I'm not as familiar with what you are talking about but my charger does say 80 amps on the front of it.

jav · Post by **jav** » Wed May 13, 2009 1:20 pm

jwrape wrote: I'm not as familiar with what you are talking about but my charger does say 80 amps on the front of it.

Which charger? The one on the gennie? or a seperate charger you have on the boat? I know the one you bought from ebay you listed as 8 amps- not 80?

jwrape · Post by **jwrape** » Wed May 13, 2009 1:22 pm

jav wrote:
jwrape wrote: I'm not as familiar with what you are talking about but my charger does say 80 amps on the front of it.
Which charger? The one on the gennie? or a seperate charger you have on the boat? I know the one you bought from ebay you listed as 8 amps- not 80?

No, there is an on board charger that is in my wheel house that charges the 2 banks of batteries while connected to the dock or if the generator is running. It says 80 amps on the front of it. I am in question to whether or not it is working properly right now but it's there and on

I did buy a 8amp 2 banks charger from Ebay that i have not decided whether to use or not. It's MUCH smaller in size

jav · Post by **jav** » Wed May 13, 2009 1:29 pm

OK but that 80 amp charger, even if working, is running of the AC side of the genset AND- unless it's automatic, it may need to be turned on in order to "charge" the house bank.

Most gensets have mulitple independant outputs. The primary being they supply AC power to AC side of your boats electrical system. You decide what to use or not use once it's running.

Many also have a seperate DC output that you can tap into to run DC loads

BUT MOST- also have a seperate DC charging circuit dedicated only to making sure the generators starting battery is recharged after you use power from it to start the gennie. This output normally happens automatically as soon as you start the genie. SO- if you use the house bank as the gennie starting battery (which is how you showed it) as soon as you start the gennie, THIS output will attempt to charge the house back.

jwrape · Post by **jwrape** » Wed May 13, 2009 1:35 pm

jav wrote:OK but that 80 amp charger, even if working, is running of the AC side of the genset AND- unless it's automatic, it may need to be turned on in order to "charge" the house bank.

Most gensets have mulitple independant outputs. The primary being they supply AC power to AC side of your boats electrical system. You decide what to use or not use once it's running.

Many also have a seperate DC output that you can tap into to run DC loads

BUT MOST- also have a seperate DC charging circuit dedicated only to making sure the generators starting battery is recharged after you use power from it to start the gennie. This output normally happens automatically as soon as you start the genie. SO- if you use the house bank as the gennie starting battery (which is how you showed it) as soon as you start the gennie, THIS output will attempt to charge the house back.

Yea, the on board charger comes on automatically and regulates itself. It is only on when 110v is on either Gennie or dock power.

I don't think I have a 12v output on the Gennie. All I know is it produces 110v. I'm not sure if it has it's own altenator but I really don't think so because I know my father and I have never done any maintenance to it and I figure after almost at least 9 years it would have needed something.

I think if anything it has a stator that produces the power it needs to run and beyond that it produces only 110v.

I could be wrong but I don't think I am.... I'll have to look on the 18th when i am out there with the Onan Technician to fix the darn thing. LOL!

Maybe I can ask a bunch of ?'s

gjrylands · Post by **gjrylands** » Wed May 13, 2009 1:46 pm

If it were me I would have a separate battery for the generator and use the eBay charger with it. The battery would only be used to start the generator so there should be no problem with overloading the charger of the generator. When hooked up to shore power the eBay charger would keep the generator battery topped off. When at sea with the generator running the generator charging circuit should charge the battery and the eBay charger should sense that and stop trying to charge it as well. If on the other hand the generator charging circuit was not charging the battery to its full capacity the eBay charger would kick in and top off the battery. Either way the battery would be fully charged. If the generator charging circuit was putting out too much voltage the battery would start to over charge and that would damage the battery. In that case, the generator should be serviced to correct the problem.

jwrape · Post by **jwrape** » Wed May 13, 2009 1:48 pm

gjrylands wrote: In that case, the generator should be serviced to correct the problem.

I'm having Cummins South come out to service the Onan 6.5K cause of running issues. Hopefully it will run perfectly after he is done... It better for $99/hr... It's gonna cost a fortune.... Hopefully he will fix it quick

jav · Post by **jav** » Wed May 13, 2009 1:50 pm

jwrape wrote:....I could be wrong but I don't think I am.... I'll have to look on the 18th when i am out there with the Onan Technician to fix the darn thing. LOL!

Maybe I can ask a bunch of ?'s

That's a great idea!

I know on the surface these things seem pretty simple and there's lots of folks out there that do lots of things that "works for them". When you really dig in though, there is a lot lof ittle details that have to be addressed to get 100% out of a system.

jwrape · Post by **jwrape** » Wed May 13, 2009 1:51 pm

jav wrote:
jwrape wrote:....I could be wrong but I don't think I am.... I'll have to look on the 18th when i am out there with the Onan Technician to fix the darn thing. LOL!

Maybe I can ask a bunch of ?'s
That's a great idea!

I know on the surface these things seem pretty simple and there's lots of folks out there that do lots of things that "works for them". When you really dig in though, there is a lot lof ittle details that have to be addressed to get 100% out of a system.

Yea, hopefully the Cummins guy will be able to fix it and give me a little advice.

ready123 · Post by **ready123** » Wed May 13, 2009 2:15 pm

jav wrote:BUT MOST- also have a seperate DC charging circuit dedicated only to making sure the generators starting battery is recharged after you use power from it to start the gennie. This output normally happens automatically as soon as you start the genie. SO- if you use the house bank as the gennie starting battery (which is how you showed it) as soon as you start the gennie, THIS output will attempt to charge the house back.

I believe his Onan is like that as mine is. The genny charges it's own battery thru the battery leads (the fact it does this is not visually obvious unless you read the manual

). Which is why way back when in his initial sketch I said he should disconnect the house from the genny battery.
NOTE: My Onan manual says to NOT charge the genny battery with an onboard charger.... the genny handles that.