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Author Topic: Generator battery  (Read 1879 times)
Mex-Busnut
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« on: November 16, 2011, 09:08:49 AM »

Dear Friends,

I am wondering if I really need a separate battery for my generator's starter, (I actually do have a small Volkswagen bug battery I could use.) or is it O. K. to use the house batteries that are in the same cargo bay as the genny?

My generator does NOT have capability to charge the starter battery.

Thanks in advance for your input!
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Dr. Steve, San Juan del Río, Querétaro, Mexico, North America, Planet Earth, Milky Way.
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« Reply #1 on: November 16, 2011, 09:59:06 AM »

I start my generator off the house batteries, why have a seperate batter?
ED
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« Reply #2 on: November 16, 2011, 10:20:46 AM »

I start my generator off the house batteries, why have a seperate batter?
ED
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    If I trusted myself to not do something stupid and run down both the house and start batteries, I'd feel the same way.  But I'm gonna like the redundancy that a separate battery will give.  At least then, I'll be able to start the gennie and charge up the start batteries and get going.

    And, Steve, I'm the last one to offer electrical advice but I think I've seen that it's pretty easy to rig up a separate battery charger to charge your starter batteries off your generator/house system.  I hope that somebody who knows will fill in that blank for you. 
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Bruce H; Wallace (near Wilmington) NC
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« Reply #3 on: November 16, 2011, 10:43:03 AM »

The reason we are keeping our genie start battery separate is for the redundancy as well. 

If the house battery system is dead, this allows us a way to start the generator to get it back up.  (Ours isn't yet hooked into the bus engine's alternator or solar panels, which would be additional charge sources that one might have to give you that redundancy while not plugged in.).

 - Cherie

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luvrbus
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« Reply #4 on: November 16, 2011, 11:05:56 AM »

Cherie,he has redundancy on his generator it is called a pull start rope sorry I could not help myself 


good luck
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Mex-Busnut
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« Reply #5 on: November 16, 2011, 11:58:39 AM »

Thanks for your input, gentlemen!

Yes, I do have the pull-start chord on my generator as well, for a backup. But since I already have a spare battery, and I also have a spare small 6-amp battery charger, I guess I will probably go ahead and use them.
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Dr. Steve, San Juan del Río, Querétaro, Mexico, North America, Planet Earth, Milky Way.
1981 Dina Olímpico (Flxible Flxliner clone), 6V92TA Detroit Diesel
Rockwell model RM135A 9-speed manual tranny.
Jake brakes
100 miles North West of Mexico City, Mexico. 6,800 feet altitude.
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« Reply #6 on: November 16, 2011, 02:38:43 PM »

My generator is wired to the starting batteries.  Then if the house batteries are dead, can still start the generator.  Course, I do have a jumper solenoid that can jump the starting to house batteries-helpful to charge the house batteries going down the road. Good Luck, TomC
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« Reply #7 on: November 17, 2011, 06:49:42 PM »

Any rig should have a switch to separate the house and start batteries. There is no excuse for discharging all the batteries at the same time.

This gives you all the redundancy you need.
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bobofthenorth
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« Reply #8 on: November 17, 2011, 07:02:15 PM »

Any rig should have a switch to separate the house and start batteries. There is no excuse for discharging all the batteries at the same time.

This gives you all the redundancy you need.

I agree with the "no excuse for discharging all the batteries" part but not with the separate house and start batteries.  If I was starting from scratch I'd have one big bank that started the engine and ran the house.  In my case it would be 5 x 8D.  Then I'd have a single Group 31 battery to start the genset.  That's the way my boat is set up and at first I thought it was dumb but the more I got to know it the more sense it makes.  Right now I'm carrying around 2 x 8Ds that get used for 3 or 4 seconds roughly every 3 or 4 days on average.  That's silly.
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R.J.(Bob) Evans
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« Reply #9 on: November 19, 2011, 03:32:18 PM »

Bob,

The only problem with that theory is that start batteries don't take kindly to long term slow discharge.

House batts should be slow discharge (deep cycle) because they handle it much better.

It won't hurt to have a separate genset battery but if you have the house and engine batts separated it is like wearing suspenders with a belt.

The good thing about being a bus nut is you can do anything you like with your bus that doesn't harm others!!
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« Reply #10 on: November 19, 2011, 03:43:05 PM »

I would use deep cycle batteries for the entire bank.  The starting loads would easily be handled by the deep cycles because there would be such a huge excess capacity.  The generator would be separate on its own starting battery.  That's exactly how our boat is wired and like I said, at first I thought it was dumb but I have come to think it is the sensible way to do things.  When our current Lifeline AGMs eventually die I expect we will end up with 5 x 8D AGMs to replace them and I will alter the wiring accordingly.
 
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R.J.(Bob) Evans
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Mex-Busnut
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« Reply #11 on: November 19, 2011, 04:42:13 PM »

Any rig should have a switch to separate the house and start batteries. There is no excuse for discharging all the batteries at the same time.

This gives you all the redundancy you need.

You understand we are NOT talking about the engine start batteries, but a separate battery for the generator's starter, right? Just want to make sure!
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Dr. Steve, San Juan del Río, Querétaro, Mexico, North America, Planet Earth, Milky Way.
1981 Dina Olímpico (Flxible Flxliner clone), 6V92TA Detroit Diesel
Rockwell model RM135A 9-speed manual tranny.
Jake brakes
100 miles North West of Mexico City, Mexico. 6,800 feet altitude.
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« Reply #12 on: November 20, 2011, 05:25:17 AM »

I have a separate genset battery.  The battery came with the original genset I bought.  I later switched gensets, but kept the battery.  At the time I never thought about connecting to the house batteries, but it would probably cost more for the long cables required than to buy another battery when necessary.

I was thinking about it this summer that my generator battery is fairly old.  It was used when I got it more than five years.  I have no idea how old it really is.
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Joe Camper
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« Reply #13 on: November 20, 2011, 06:29:24 AM »

Yes Dr. Steve the thread expanded a bit.

I would give the Gen its own battery separate from the house battery's.

You could also connect the gen to the house bank with a cable that runs thru a start solenoid that you could control from the control panel in the bus.

When energized it would be sending charge to the gen battery while your driving and also allow you to jump start the gen should that battery get low  AND still be able to have the 2 banks isolated when everything is good to give you back up and redundency.

This is how our camper is wired.

We also have the chassis and house banks configured the same way. They are both 24 volt and with the big alternator. I can tie them togeather when we are driving and separate them when we are not.

Wiring a start solenoid in is a very simple project. If the banks are separated to any degree use the correct size cable carry the loads. This will be the only real expence of doing this.

Our gen has an alternator and it gives us the additional option of charging the house bank off the gen alt too and you would be suprised how well that little alt on the gen keeps the house bank up if the inverter charger is out.
« Last Edit: November 20, 2011, 06:52:21 AM by Joe Camper » Logged

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luvrbus
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« Reply #14 on: November 20, 2011, 06:34:56 AM »

Steve if go the solenoid route for charging it has to be a constant voltage solenoid a regular starter solenoid will just melt they are made for momentary volts only   


good luck
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« Reply #15 on: November 20, 2011, 06:53:40 AM »

Thank you luvrbus for that correction.

Adding this will let you have it both ways if you so choose.
« Last Edit: November 20, 2011, 06:56:14 AM by Joe Camper » Logged

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robertglines1
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« Reply #16 on: November 20, 2011, 07:01:07 AM »

Steve ; your gen set(if still the same one) will not require much amperage to start. A small separate battery prob would be best. But if not run a cable to it from coach system. You do have starter rope for emergency use? correct.  Just a suggestion.  prob could tap large cable coming to front box no more amperage than you need to start.  Check size first. Just a thought.. Good luck.  Bob
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« Reply #17 on: November 20, 2011, 07:09:07 AM »

Great thread! There's different ways to do the same thing, none better or worse than the other. It all depends on what you want!

Some redundancy is desirable for me, but within cost and complexity restraints.

Your generator has a pull start, as well as electric start.
That's a big redundancy that discounts the need for a separate generator battery. Many of us would be jealous of your pull start option, if not now, then when the whole thing is dead, despite our efforts at separation and preventive maintenance...

Your generator has no capacity to charge its stand alone battery.
That means you need a bunch of money for hardware to connect and disconnect the generator battery from the system, or a dedicated battery charger. Mixed types of batteries between your generator battery and the bank you tie it with can make tying them all together troublesome from a battery health standpoint. And that's health for both the gen battery and the bigger bank. Rate and state of charge issues.


After a busnut gets over the novelty of the whole "designing stuff to my own wants" or "do it my way", and into the life cycle costs for the second or third time, replacing all these different batteries, and maintaining/troubleshooting/replacing the separation/charging hardware as it ages, it can become a financial burden, not to mention a big pain in the @$$.

FWIW, the generator I have waiting for me to install in the coach is electric start only, and has no capacity to charge its own battery(delete option by previous owner, it can be added). Same as some other posters, I am also planning to abandon the coach start battery system in the future and change to a single bank of deep cycles.

For the desired redundancy, I will have a dedicated generator battery, same as bob, the wildly popular, and inexpensive for it's size, group31 truck battery, and either add an alternator to the generator or use a simple AC battery charger wired in to the house system and powered whenever the coach is.

With just deep cycle batteries for the other system, the coach regulator can be changed out to a modern 3 or 4 stage one to direct the stock alternator to take good care of them going down the road, and the Trace 4024 takes care of them otherwise. Always an option is a bit of solar on the roof for battery tending when the coach is stored between uses.

Again, great thread, where nobody is wrong and everyone is right!!

happy coaching!
buswarrior


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« Reply #18 on: November 20, 2011, 07:37:56 AM »

The idea of the combined house and starting battery bank definitely has some merit.  I wish I had read that idea before I replaced my starting batteries a year ago.  The required cabling and new regulator would almost certainly have cost less than what I paid for my starting batteries.

The only downside I can see is if the batteries are down from use on the house side when you need to start the bus.  Of course, if you're running the batteries down so much they won't start the bus you're going to kill the batteries eventually.
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« Reply #19 on: November 20, 2011, 08:14:46 AM »

The only downside I can see is if the batteries are down from use on the house side when you need to start the bus.  Of course, if you're running the batteries down so much they won't start the bus you're going to kill the batteries eventually.

You're right - we shouldn't be running them that low anyway.  But in the event they do end up too low to start the coach that is why the genset has its own battery.  Start the gennie, have coffee while the genset brings the battery bank up enough to start the coach.  And BW is right - the ultimate redundant start system is a rope on the side of the genset. 
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R.J.(Bob) Evans
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« Reply #20 on: November 20, 2011, 08:18:30 AM »

Having a method to auto start the generator as a battery protection/maintenance strategy would be part of it for me, and I suspect the others will have similar ideas.

The batteries simply will not be allowed to go below the recommended state of charge, regardless of what is attempted by me or my fellow campers, and we all know it is the other campers who are to blame...  Wink Roll Eyes

Accidentally draining the single bank would fall into the same category as all the failures a two bank system can suffer that accidentally drains everything down. It can happen, no matter what we try to remember or maintenance we do or don't do, stuff goes wrong eventually.

Saving the money every so many years on a pair of 8D's for starting and use when the coach is running, while another even bigger bank that must also be purchased periodically is in the belly loafing, and then reversing their working/loafing roles at the campsite...

When I am religiously preventing either set from being abused or unwittingly dragged below the manufacturer's recommendations for state of charge, the longer I think about it, I wonder why as busnuts, we haven't been deciding to do this earlier and in greater numbers? We've had the technology and know-how to do it quite intelligently for some time now...?

happy coaching!
buswarrior 
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« Reply #21 on: November 20, 2011, 11:51:33 AM »

  Looking up batteries a while back, I kept pulling up this site for some sign company that used 8D's rather than trojan golf car batteries, saying they would deep cycle better, at least in their application. This is the site:http://www.allmand.com/products/documents/batteryqareva.pdf

  I would be curious what other peoples thoughts are on 8D's, one nice thing they point out is being a 12 volt you have half the connections to maintain as well as current losses.

  If you were running a single bank without start batteries, whether or not you had a genny battery you could always jump off the towed, I mean, how often are we going to screw up??

  Has anyone considered two smaller, seperate banks, like a bank A and bank B, and switch back and forth while charging the one thats offline??

 
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buswarrior
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« Reply #22 on: November 20, 2011, 01:11:44 PM »

8D is a battery size, not a battery type.

There are 8D size deep cycle batteries, as well as the 8D size start batteries that a coach typically uses.

There are posters here who have 8D deep cycles for the house bank.

happy coaching!
buswarrior
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« Reply #23 on: November 20, 2011, 01:40:24 PM »

I think the battery configuration we typically see is an artifact from the history of how conversions evolved.  When we started RVing "deep cycle" essentially meant that the battery had a rope handle on it.  When the grandfathers of this hobby/art started converting buses the coach bank was the big battery bank.  House loads were much lower than what we expect now - they ran some 12 volt lights, the water pump, the control panel for a propane fridge maybe.  As time and expectations have progressed we now expect our coaches to have all the 110 volt conveniences we have at home. 

When the coach bank was the most important/largest bank then it made sense that it should be a start type bank.  The only reason the idea of using the house bank to start the coach makes sense is because it typically is ridiculously oversized relative to the start requirements.  If the house bank was two Group 31 batteries with a rope handle then they wouldn't be very useful for starting.  When the house bank can be 5 x 8Ds then they can be deep cycle batteries and still deliver enough inrush current to start our engines.  I'm not sure if my boat is an oddball or if boats in general have progressed further through the evolution but I assume they must have followed a similar path.  I just know that when we bought the boat I thought I'd be changing the it's configuration and now I'm thinking I should change the bus config.

That's my theory and I'm sticking to it.
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R.J.(Bob) Evans
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« Reply #24 on: November 20, 2011, 03:06:11 PM »

Some gensets have a built-in alternator in the flywheel, Onans come to mind. If there is no battery connected to that type the alt will self destruct.

Deep cycle batts are ok for starting if the engine starts quickly, I've used mine numerous times when alt/start batt problems gave me no choice, but my 8V71 starts on the first crank.

If you live/drive in a cold climate you can easily destroy deep cycles during hard starts.

That being said, it is hard to find strictly deep cycle marine batts anymore, they all seem to be dual purpose!!
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