Generator battery

[Joe Camper]

Thank you luvrbus for that correction.

Adding this will let you have it both ways if you so choose.

[robertglines1]

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

[buswarrior]

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

[belfert]

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.

[bobofthenorth]

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. 

[buswarrior]

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... 

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 

[artvonne]

  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??

 

[buswarrior]

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

[bobofthenorth]

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.

[gus]

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!!