....Anyone with experience attmpting to temporarily maintain battery pack with small charger?
Jim,
We were staying in a friends driveway for a few days. Running the Onan was not a good idea in this particular quiet neighborhood.
The best hookup available was a 15amp outlet in the garage with a 50 foot 14 gauge cord. I could have plugged the MH primary cord into that but the odds of tripping the breaker was high. Any appliance on top of the charging circuit would be too much.
Instead I hooked up an old Sears automotive "automatic" charger to the house batteries. At full output it only draws about 7 or 8 amps. I could not trip the breaker. My idea was that if anything, like the lights, TV or microwave, were used the batteries would supply the power and the charger would slowly replace it.
It worked well. In the evening the lights and TV would draw the batteries down like when dry camping. As I went to bed the MH battery gauge would show about an 80% charge. It would be near 100% in the morning. The charger I have does not switch to "maintain" or "float". I checked it frequently and the charge rate would vary, but it didn't shut off.
In your case, you have 120 for all the appliances and you only need 12 volt for lights. I think you should be able to maintain the house batteries with the charger. If you have a new "solid state" type charger you may have more trouble than if you have the older and cheaper variety.