Community Forums

MarkS · 05-04-2008, 05:35 PM

I've got my inverter and just finishing the final planning for the installation.

Is a motorhome's factory-installed 12v battery charging system heavy enough to deal with the increased load added from the inverter?

Was the factory-installed 12v charge system designed to have a draw that is significantly higher than if it were simply charging the batteries?

Will a constant 50-Amp draw from an inverter cause damage to the coach's automatic-charge-relay, the wiring from the chassis' alternator to the coach's automatic-charge-relay, or the writing from the automatic-charge-relay to the battery, or to the coach chassis' alternator itself?

I'm estimating that my television plus my DirecTV HD-DVR will draw about 500 watts. The inverter claims 90% efficiency, so I rounded up to 600 watts draw on the AC side. 600 watts @ 120 volts is 5 AMPS. That means the inverter will be drawing 50 AMPS from the house battery bank while I am driving my RV down the road and the kids are watching TV.

My Damon coach has an automatic-charge-relay that is designed to allow the chassis alternator to charge the house battery once the chassis alternator has charged the starting battery. I am concerned that this charging system was sized only for a battery charge load. Will adding an additional 50-AMP draw on the charge system cause damage to the charge system?

Thanks
Mark

MarkS · 05-04-2008, 05:35 PM

I've got my inverter and just finishing the final planning for the installation.

Is a motorhome's factory-installed 12v battery charging system heavy enough to deal with the increased load added from the inverter?

Was the factory-installed 12v charge system designed to have a draw that is significantly higher than if it were simply charging the batteries?

Will a constant 50-Amp draw from an inverter cause damage to the coach's automatic-charge-relay, the wiring from the chassis' alternator to the coach's automatic-charge-relay, or the writing from the automatic-charge-relay to the battery, or to the coach chassis' alternator itself?

I'm estimating that my television plus my DirecTV HD-DVR will draw about 500 watts. The inverter claims 90% efficiency, so I rounded up to 600 watts draw on the AC side. 600 watts @ 120 volts is 5 AMPS. That means the inverter will be drawing 50 AMPS from the house battery bank while I am driving my RV down the road and the kids are watching TV.

My Damon coach has an automatic-charge-relay that is designed to allow the chassis alternator to charge the house battery once the chassis alternator has charged the starting battery. I am concerned that this charging system was sized only for a battery charge load. Will adding an additional 50-AMP draw on the charge system cause damage to the charge system?

Thanks
Mark

historyljc · 05-04-2008, 07:47 PM

Mark,

Properly installed, you're good to go. Your alternator has the capability of putting more amps in than your talking about drawing out.

Some of the electrical wizards can give you a more technical explanation.

Ray,IN · 05-04-2008, 10:00 PM

Most of today's autos come with at least a 135A alternator. I suspect your coach has near a 200A. I would monitor the wiring though, that much amperage, over long periods, may generate a lot of heat.
FWIW, Mac the Fire Guysays diesel MH's have more fires(mostly engine fires) than any other RV type.

hamguy · 05-05-2008, 09:56 AM

Mark, I cannot believe your TV + Sat Rcvr + DVD will draw more than 250 watts.

Each piece of equipment has the power requirements on a label on the back. If you can't see the back, look up the model on I'net for specs.

John Hilley · 05-05-2008, 12:32 PM

In your planning how far from the battery are you planning on installing the inverter. 2 to 4 ft is optimum and 2/0 cables should be used. Another consideration is that if you use it during dry camping and you use the generator to charge the batteries it will take quite awhile to recharge the batteries depending upon the charge rate of your converter/charger, some are only 40 amps.

MarkS · 05-08-2008, 03:45 PM

Thanks for the info so far.... To answer the questions, I am planning on installing the inverter adjacent to the existing house battery bank. I will be using 2/0 cables, less than 4-5' in length, with a current limiter on the positive cable in case something goes horribly wrong with the inverter.

My intention is solely to power my entertainment system as I drive, for the kids. I am not intending on using the inverter for boon docking, so long battery life is not a factor at this point.

My primary concern is whether the load from the inverter will cause harm to my coach's 12v charging system. I am assuming that the coach's 12v charging system was designed only to charge the house batteries. With the addition of the inverter, we would be adding a 25 to 50-Amp continuous load. This is in addition to the load for charging the battery.

I have a 2007 Damon 376 on a 2007 Ford F53 chassis, which has a 115-Amp alternator. Obviously the alternator is large enough to support the additional load.

But Damon has installed their own wiring and an automatic-charge-relay (ACR) between the Ford chassis and the coach's house battery. Damon installed wires from the chassis to an ACR, and then to the house battery. (The ACR is similar to a battery isolator)

The question is whether you think the Damon charging system can handle the additional 50-Amp draw.

My fear is that the chassis alternator will charge the starting battery, and when the ACR closes to allow current from the alternator to flow to the house battery for a charge, that the either the ACR contacts will arc weld closed, or the wire that Damon used will burn.

Has anyone had any problems hooking up an inverter to a house battery vice hooking up to the starting battery?

Any help is appreciated.

Thanks,
Mark

Ray,IN · 05-08-2008, 05:35 PM

This 12V wire size calculator may be of use in determining if the present wiring will be adequate or if you need to upgrade.

Gary RVRoamer · 05-09-2008, 07:19 AM

Your charge relay should be sized to handle at least 50A, since it is not unusual for a battery bank to draw that much charging from the alternator. I say "should", because not all manufacturers size things for worst case loads and Damon may not have provided wiring from alternator to house batteries that can even carry 50A continuous. It should be fused for whatever load it is designed to carry, so locate the fuse and see what happens.