I plan on upgrading my popup camper,to a new one with electric top.I plan on running 2 series 27 rv batts.I plan on running a 6 guage wire to the truck batt with solenoid with switch and 100 amp fusethat I can switch in or out.My question is if the microwave load is 1050 watts or about 90 ampsand I switch in the truck batt and Idle the engine,will the load see the alt as a 4th batt and take 22.5 amps from each source.The alt is rated 155 amps,90 to 100 at idle.

The load will not be equal. A starting battery has many more plates and will take the majority of the load.This is a case of "Never say never". While I wouldn't recommend it, you could test it with a short run. Go back right after and check the starting battery voltage. The starting battery has a limited reserve capacity and cannot hand deep discharge without immediate recharging (i.e. starting engine and time to recharge).

Probably won't be evenly distributed. But, no matter.

You have 3 batteries yes? Two 27s on the trailer and something in the truck.The microwave is 1050w input power or cooking power? Input power it will draw 90+ amps, cooking power it will draw closer to 120+ amps. If using a modified sine wave inverter the power will be reduced by 20% to 50% and cooking times will be longer.The long #6 will supply 20 to 50 amps with the balance coming from the two 27s. The truck battery probably will not discharge as the alternator should hold voltage above 13 volts at the front of the truck.For maximum transfer consider some shorter jump cables direct from the truck battery to the trailer pair. Look for #4 copper cables.Best to have 4x group 27 on the trailer to drive a microwave.

As others said, no. That's in part because the long run of 6 awg wire will function as a current limiting resistor.

I should add the a MH normally has a solenoid (or solid state switch) that allows the alternator to charge the house-batteries and starter battery while the engine is running, but blocks drain from the starting battery when the engine is off. The cable gauge is usually 2 or heavier to allow maximum current from the alternator.It looks like your trying to do the opposite without the engine running.

Inverter amps question | Good Sam Community

ScottG
Nomad
Dec 21, 2014
As others said, no. That's in part because the long run of 6 awg wire will function as a current limiting resistor.
time2roll
Nomad
Dec 21, 2014
You have 3 batteries yes? Two 27s on the trailer and something in the truck.
The microwave is 1050w input power or cooking power? Input power it will draw 90+ amps, cooking power it will draw closer to 120+ amps. If using a modified sine wave inverter the power will be reduced by 20% to 50% and cooking times will be longer.

The long #6 will supply 20 to 50 amps with the balance coming from the two 27s. The truck battery probably will not discharge as the alternator should hold voltage above 13 volts at the front of the truck.

For maximum transfer consider some shorter jump cables direct from the truck battery to the trailer pair. Look for #4 copper cables.

Best to have 4x group 27 on the trailer to drive a microwave.
Mandalay_Parr
Explorer
Dec 21, 2014
Probably won't be evenly distributed. But, no matter.
MNtundraRet
Navigator
Dec 21, 2014
The load will not be equal. A starting battery has many more plates and will take the majority of the load.

This is a case of "Never say never". While I wouldn't recommend it, you could test it with a short run. Go back right after and check the starting battery voltage. The starting battery has a limited reserve capacity and cannot hand deep discharge without immediate recharging (i.e. starting engine and time to recharge).

Forum Discussion

Inverter amps question

About Technical Issues

Related Content

Inverter question

Inverter question

Magnum Inverter/Converter Question

50 amp question

30 and 50 amp genny question