How to hook up my 3 RV batteries

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Rob&Deryl

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Unless you are dry camping (boondocking), your batteries should not run down. Any campground has electric hookups.
If you are using the electric hookup and the batteries run down then get to the root of the problem. I found that the dealer didn’t turn the battery disconnect back on when they dewinterized it. I found it at the 3rd campground with insufficient power to use the landing gear.
If you decide to get a generator, you only need one big enough to charge the batteries and run a few items if you are dry camping.
 

ButchW

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If you decide to get a generator, you only need one big enough to charge the batteries and run a few items if you are dry camping.
But be mindful if you are in areas where you might want to run an AC... Pretty heavy load there...
Butch
 

Gary RV_Wizard

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I hear i need 7000 watts to run all my appliances, im interested in a dual fuel, any recommendations?
Unlikely for a 1990 Southwind, which is almost surely a 30A system. That's only 3600 watts. And it probably had an onboard generator when new - is it still there?

My 1 battery was good, 2 were not, and they were just depleted from going empty and recharged over and over, so i need a generator.
"Need a generator" doesn't follow from that battery status. A generator could run a charger, but that doesn't fix the "recharged over & over" situation and you probably cannot run a generator 24/7. It's both noisy & expensive (fuel) to do that, and few places would even permit it. Besides, if you are using campgrounds, they typically have electric power anyway.
 

phil-t

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Ogdensburg, NY
Still need a knowlegable technician to look at this system and get it straightened out. Generator, by itself is not going to fix anything permanantly.
 

Scards

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Chino ca
Im at a place without hookups, so i was just running my batteries without being plugged into any source.
 

Scards

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Unlikely for a 1990 Southwind, which is almost surely a 30A system. That's only 3600 watts. And it probably had an onboard generator when new - is it still there?


"Need a generator" doesn't follow from that battery status. A generator could run a charger, but that doesn't fix the "recharged over & over" situation and you probably cannot run a generator 24/7. It's both noisy & expensive (fuel) to do that, and few places would even permit it. Besides, if you are using campgrounds, they typically have electric power anyway.
My Onan Emerald III is still there AND it does work but needs tuning up and i have to keep it filled up half way with gas in my RV for it to run. That didnt stop my batteries from going dead, i dont know, ill talk to someone...im frustrated due to my ignorance of all of this, time to learn and fast!
 

Lou Schneider

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My Onan Emerald III is still there AND it does work but needs tuning up and i have to keep it filled up half way with gas in my RV for it to run. That didnt stop my batteries from going dead, i dont know, ill talk to someone...im frustrated due to my ignorance of all of this, time to learn and fast!
Having the generator stop running before the tank is empty is intentional - it keeps you from being stuck out in the middle of nowhere with no fuel to drive to a gas station.
 

WILDEBILL308

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FORT WORTH TEXAS
Im at a place without hookups, so i was just running my batteries without being plugged into any source.
Did you get your batteries tested? Did you get them hooked up correctly?
What are you trying to run off the batteries?
That is a very small capacity batterie bank for any extended use.
Bill
 

WILDEBILL308

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My Onan Emerald III is still there AND it does work but needs tuning up and i have to keep it filled up half way with gas in my RV for it to run. That didnt stop my batteries from going dead, i dont know, ill talk to someone...im frustrated due to my ignorance of all of this, time to learn and fast!
I would get a mobile teak to change the oil and do the tune up before it doesn't run any more.
The Onan Emerald III will use between 1/2 to 3/4 gallon per hour depending on load.
Bill
 

Ex-Calif

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My Onan Emerald III is still there AND it does work but needs tuning up and i have to keep it filled up half way with gas in my RV for it to run. That didnt stop my batteries from going dead, i dont know, ill talk to someone...im frustrated due to my ignorance of all of this, time to learn and fast!
Probably time to learn a little electricity math. The secret is "power" usually defined in watts.

Watts is handy to convert AC and DC voltages. Simply divide the watts by the voltage.

4000W / 12 V = 333 amps.
4000 W / 110V = 36 amps

Then you need to add up all the things you are powering up to understand what is heppening to the batteries. Incandescent bulbs on the DC circuits are very power hungry and changing to LED bulbs or fixtures is the easy way to go.

40W incandescent / 12V - 3 amps. 5 or 6 of these could really drain a battery.

A single battery usually has about 80 amp hours - or will run 80 amps for 1 hour. Actually about half of the amps is usable until the battery is drained so 40 amps per battery is about what you get. For 2 batteries that's 80 amps in total.

So back to the generator... If you take 80 amps out of the batteries then you have to put 80 amps back in. Batteries can only accept amps on a limited basis because as they charge they heat up and that causes resistance. So 80 / 333 = 1/2 hours of charge time. In reality the battery can probably accept 20 amps per hour so you are looking at 4 hours to fill up the batteries.

And due to the vagaries of heat and resistance you probably will not "top off" the last bit of charge with a generator. You will likely get it to around 90% or 72 amps on average.
 

Mark_K5LXP

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Albuquerque, NM
Actually about half of the amps is usable until the battery is drained
What makes the other half unusable?

Batteries can only accept amps on a limited basis because as they charge they heat up and that causes resistance.
Heat is not a consequence of charging a good battery with a proper current profile. The reduction of current for the last 20% is intentional to allow for electrolyte diffusion and to allow the entire plate surface to charge evenly.

And due to the vagaries of heat and resistance you probably will not "top off" the last bit of charge with a generator.
Charging from a generator is no different than shore power so there's no reason you can't charge 100% if you want to. What can be limiting though is time, one may not want to run a generator for the time it takes to finish the absorb phase but there's no heat, or resistance.

Mark B.
Albuquerque, NM
 

silversport

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Dec 11, 2020
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Hayward, ca
First thing that jumps up for me is only replacing one of three batteries, the system is only as good as the weakest battery. With all those leads tap off every battery is not the way I would wire a system.
 

Cameodon

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Jul 2, 2021
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Edgewater, fl
I suspect that it is correct that the far right battery should be the chassis starting battery but as I look at it, I see only a white wire to the negative post and no motor-vehicle negative battery cable as it should have. If you look at the cell caps, the two batteries to the left are definitely 12V as there are 6 cells. The one to the far right looks to be the same but is difficult to see for sure.

All 3 negative posts are tied together so that could be the negative being used for the starting battery, but it is not usually that way in my experience. Only 2 of the positives are connected so they are probably the 2 for the coach working in parallel. There are 2 red cables connected to the positive post of the far right battery, and one of those could be from the RV's converter, but I see no way to know. I also see 4 heavy cables attached to positive from outside, but only 1 to a negative post, and that seems very strange to me.

Scards, it would be my advice that you need someone who is qualified and who has a good volt/ohm meter to figure this out for you.
I almost agree, being very careful how/what I say here as I’m relatively new here. The way I see it all three are chassis and all three are engine-vehicle batteries! Note Ididn’t say they SHOULD be that way. I see the motor (engine) negative cable attached to the extreme left battery which makes all 3 in parallel serving both the engine and chassis. Since all 3 go dead over night my guess is the only source of charging is the engine.
 

Cameodon

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Edgewater, fl
I agree with Ex-Calif. With your lack of knowledge and experience, it may be time to call in a mobile repair guy and have him straighten everything out and do a little trouble shooting to see if everything is up to snuff.
Again, still being careful, in your case I would strictly follow this advice. Just to be safe..
 

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