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Old 06-24-2016, 09:44 PM   #1
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Join Date: Jun 2016
Posts: 6
Electrical Modifications

I have a new-to-me 1994 class C. Other than a few running problems that are being fixed right now, everything's in good shape.

On a recent trip, we decided to dry camp for one night. Since our coach battery was toast, I bought a 12 volt deep cycle (group 24) from Walmart. This gave us adequate power for. An overnight, but is not adequate for our future needs. After plugging in to shore power for a couple of days, I reached the following conclusions:

Our converter/charger does a poor job of charging the batteries. Even after two days of being plugged in, the battery wasn't completely charged.

The battery status lights are not accurate (actually, none of the status lights are very accurate).

The wires carrying the charge from the converter aren't adequate to handle a significantly higher charge rate.

One battery (101 amp hours) is marginal for dry camping, especially if we need to run the furnace at all.

Here's how I plan to address this:

Add two 6 volt golf car batteries (approx 200 amp hours),in addition to the existing 12 vole deep cycle. I'll also add a battery selector switch, sinc I'll have different capacities on the two battery banks. I'll never plan on using the "both" setting.

Rather than replace the converter charger, I'll add a 25 amp smart charger (Stanley has one that looks good, for a bargain price). To set it up, I'll disconnect the charger wires from the old converter, and hard wire the charger to both battery banks. This will allow me to use a shorter run, with larger wire than what runs from the converter. I'll have a selector switch, allowing me to charge either battery bank, so I'll always charge the bank that's Isolated. The charger will be on a switched outlet that's energized through both shore power or the generator.

All 12 volt lights will be converted to LED, to reduce the load on the batteries.

I'll install a volt meter / amp meter, to improve my ability to monitor the batteries. This will be switched so each battery bank can be checked out while isolated from a load.

I'll plan on running larger than required wire, both for the charger and the load on the batteries, since I'll have to relocate the batteries to make room for the extras.

Does anyone here see a problem with this plan?

Sorry for the extra long post......

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Old 06-24-2016, 10:54 PM   #2
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Join Date: Jul 2015
Location: Lake Havasu City, AZ
Posts: 509
No expert, first observations


Wondering if the Walmart battery was truly deep cycle? Generally those marine batteries are kind of hybrids doing neither job well. Was it rated in AH-20 or CCAs?
Granted your older converter might be under powered your choice of a 25A charger addition doesn't sound like a screamer either, for several batteries.
What does the nameplate rate the current converter at?
With weight and space at a premium I'd be prone to replace the converter 75A with a multi-stage (bulk, absorb, float) charger with adjustable voltage output. A temp sensor circuit would be nice also.
Although it might not be in your budget now, Explore an inverter which does those charging things. It would also give you flexibility for a few light duty 120v items.

Agreed on the 6V GC cells, isolation switch, heavier wire, and the shunt type battery monitor, LEDs.

Remember you only have 50% of the rated AH rating usable on the true deep cycles. The marine battery will probably die quickly even cycling it to 50%.

Happy motoring

J & J + Kickr's the Vonderhund
DRV, ES-38RSSA, 19.6K#
GMC, 3500HD-Max, CC, 8'-DRW, 9.1K#
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Old 06-24-2016, 11:54 PM   #3
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The battery is a deep cycle, not a marine starting battery. I know it's not as good as a golf car battery, but it's what they had that would fit. I'll keep it, and use it as long as it lasts - when it dies, I'll get two more 6 volt.

I know the charger wasn't doing the job, because the battery wasn't fully charged after two days on shore power.

The problem with replacing the converter isn't buying the converter - it's routing new wiring to charge the batteries. What's there now is woefully undersized, and getting large wires routed to the battery compartment would be difficult.

I'll look into the inverter. I have a 1200 watt inverter, but we don't use it for anything now, except to plug in iPhone chargers.....
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Old 06-25-2016, 04:19 AM   #4
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Add the 2, GC2 batteries into the system without the A/B switch and replace the old converter with a 55 amp, 4 stage " Go Power " charger. Run proper size charger cables to the new batteries and tie the new batteries to the old. Add fuses where needed.

The charger will then charge all of the batteries.

Charging different size battery banks together is not the perfect setup but it is done every time a MH alternator charges house batteries.
In most, once at a set voltage is reached, they simply interconnect both banks thru a high amp relay ( solenoid ).

Drawing down 1 battery then the next, while managing them thru a A/B switch, will cause you to run each one lower. That will shorten their life more then tied together as 1 bank.

I have done as I suggested on my 1999 Class C. It has been 3 seasons of full time summer living without problems.

For some info on combining different size banks, read the FAQ section about it on " yandina.com "
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Old 06-25-2016, 03:33 PM   #5
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I added a second battery on my Class C with a selector switch. I used fairly large wire to install the 2nd battery and add the selector switch, I believe they were 4AWG.

At the time my converter seemed to charge both batteries, at least I didn't see a huge difference. The Class C didn't have a huge parasitic draw. I would use one battery during the day and then switched over to the second one at night. In the AM I'd start the generator to charge both batteries..
Jim J
2002 Monaco Windsor 38 PKD
2005 Jeep Grand Cherokee w/5.7 Hemi
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