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Charging 24V Chassis Batteries With 12V Charger
Turns out it is easy if the bus has the typical Vanner Equalizer.
Look closely at the picture and on the Vanner there is a schematic for how it is wired to the 4 chassis batteries (2005 XLII shell in my case). The 12 volt connection attaches before the batteries are in series, before they are 24 volt output.
Connecting a 12 volt battery charger at the +12 volt terminal (negative charger alligator clamp) and the +24 volt terminal (positive-red alligator clamp) will charge both banks of the chassis batteries. It saves the cost of purchasing a 24 volt battery charger.
I did not figure this out on my own, I had help!
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18 Replies
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Very good to know, Les.
I am still very new to Prevost and am curious under what circumstances would one want or need to charge their four chassis engine starting batteries in this manner?
I am assuming the house batteries could also be charged in this manner? THANK YOU
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Jeff, my Guest charger (maintains the chassis batteries when plugged in to shore power) recently died. I saw that the light on the charger were off and discovered that it had failed internally.
To keep the chassis batteries charged while waiting a new Guest charger, this method will prevent running the chassis batteries too low.
Below is a picture of the Guest charger with no lights lit.
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And Jeff, your inverters are for keeping your house batteries charged when plugged in to shore power (or running the generator).
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I know I sound like a broken record but if you have to use or maintain a charger for your chassis batteries something is wrong.
A decent set of chassis batteries will hold a sufficient charge to start a bus after several months of bus storage. No charger is needed to do that unless the batteries are old and failing or there is a phantom load on the batteries. In either case using a charger is nothing more than putting a band aid on a serious problem.
There are reasons to use a chassis battery charger, such as to recharge or maintain batteries that have had a load on them, such as when working on systems such as lights that are going to pull down the batteries.
A charger will mask battery problems so if you go on a trip you might find yourself unable to start the coach after you fill up at a truck stop or after a night in a campground without having the charger powered up.
In these times when our coaches are effectively in storage for an unknown period it makes perfect sense to use a multi-stage charger every couple of months just to keep the batteries topped off, but it makes no sense leaving a charger on all the time. Some chargers will destroy batteries if left on all the time.
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I have a question regarding these Vanners. I have only one of them, the second was removed at some point and my alternator does not charge my house batteries. Does anyone have a copy of the schematic showing how the 2 of these should be hooked up?
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Does anyone know if this is harmful to the Vanner since you are hooking up your charger to the 12v post and the 24v post?
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I connected my Chassis battery charger directly to my Chassis batteries. I used the engine Block heater circuit to turn mine on and off via the switch on the dash.
1984 96" with 8V92TA
(remodeled Liberty Coach)
Greenwood, MO -
I did the same thing but the charger over heated and melted. So I just got new batteries. I go months without a problem of dead batteries now.
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The Chassis batteries with both of the switches off, draw almost Zero load. They don’t need to be in charge state all the time. Usually a few days before a trip i push the charge switch and monitor the voltages. When in storage between trips it is not charging. I would never leave it plugged in all the time charging.
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Mike … precisely what I do.
If I don’t leave the lights on or something hooked to the chassis batteries, they will last six to eight weeks sitting and still start the coach.
If your chassis batteries “run down” in a short period of time of not starting the coach, I think you have one of three problems:
1. Your chassis batteries are old.
2. One (or more) of your chassis batteries has a problem that will only get worse. Possibly leaving your stranded. BTDT!
3. Someone (hopefully NOT your converter) has wired something directly to the batteries or an “always on/hot” power source that shouldn’t be.
4. You (or someone else) inadvertently left “something on” that shouldn’t have been left on draining the chassis batteries.
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We full time in our Prevost and not having a charger connected to the coach batteries will result in dead batteries in a couple of weeks. Just can’t turn everything off.
You can also charge your 24V battery bank 2 batteries at a time. There are 2 12V banks of 2 which can be charged with a standard 12V battery charger. You can then connect the other bank to the charger and in the end they will be charged enough to get started.
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Easiest way for chassis batteries is using the 24v jump lug and a 24v charger. Battery Tender has a 24v trickle that works well.
Clint & Tammy Summers
2000 XL 45 Country Coach (rivets)
1977 FC31 Bluebird Wanderlodge (more rivets)
Vonore TN -
We got 8 yrs from our last set of chassis batteries (4). We keep a cheap $5 Harbor Freight 12v trickle charger on them via the Vanner 12v and 24v post.
Here’s an Article by Victron Energy titled “Five Ways To Extend The Life of Your Lead Acid Battery”: ARTICLE -
To top off the charge of the chassis batteries, while in the bus, which method would be preferred?
To connect a 12volt charger to the Vanner as shown in Don’s photo.
Or to get a second 12 volt charger and connect them:
Putting 1 charger on the bottom right battery and 1 charger on the top right battery.
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If you use 2 chargers you would connect 1 to the 2 batteries that are wired as 12V and then the other to the 2nd 2 batteries that are wired for 12V. You can put a multi-meter on each set to verify a 12V output. So the chargers would be connected to the negative post of 1 battery and to the positive post of the 2nd.
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