Charge Batteries by Idling Tow Vehicle?
This may be a dumb question, but since every tow vehicle has a generator which is connected to the batteries and they charge while driving, how about hooking up and charging at the campsite while idli...
Forum Discussion
We don't RV with a towable (a small Class C motorhome), but we do sometimes idle the engine for an hour or so for the initial boost charge of our RV batteries before we start up a very small Honda generator for 3-4 hours to bring up the batteries to around 90% of full charge. Here's how we do it and what the conditions are:
- We use AGM batteries, which charge faster than regular batteries.
- The wiring between the engine alternator is short and a large size, 6 AWG.
- Our idling engine is a gas Ford V10, which is whisper quiet when idling (a lot of ambulances have it and sit idling) ... and once it's catalytic converter is hot, there are no fumes we can notice coming from it's exhaust pipe.
- The V10 came with a large stock alternator ... 130 amp.
A few days ago we drycamped for several days. After about the 3rd day the batteries needed topping up. We started up the V10 and ran it at an idle. It's alternator output immediately spiked to 80 amps, and then slowly tapered down to around 30 amps during the next hour of idling. At that point we probably had restored around 40-45 amp hours back into the batteries. I could then take the batteries around a 90% charge with the tiny Honda, or the built-in coach generator.
The type of batteries, the size and length of the cable, the large stock alternator, and the quiet engine idle made this type of quick and convenient boost coach battery charging possible. I can monitor this happening because of a digital ammeter and digital voltmeter mounted on the dash in the cab.
When on the open road between camping sites for 4-5 hours, the engine alternator will bring the coach batteries to 100% ... which I can determine because at that point current is no longer flowing into the batteries according to the ammeter.
Before solar and quiet small generators, idling the main engine was the only way to top up coach batteries. I had a 1969 Chinook motorhome way back when for awhile that was designed to use this method ... except it's alternator wasn't anywhere near the capacity of modern ones.
- We use AGM batteries, which charge faster than regular batteries.
- The wiring between the engine alternator is short and a large size, 6 AWG.
- Our idling engine is a gas Ford V10, which is whisper quiet when idling (a lot of ambulances have it and sit idling) ... and once it's catalytic converter is hot, there are no fumes we can notice coming from it's exhaust pipe.
- The V10 came with a large stock alternator ... 130 amp.
A few days ago we drycamped for several days. After about the 3rd day the batteries needed topping up. We started up the V10 and ran it at an idle. It's alternator output immediately spiked to 80 amps, and then slowly tapered down to around 30 amps during the next hour of idling. At that point we probably had restored around 40-45 amp hours back into the batteries. I could then take the batteries around a 90% charge with the tiny Honda, or the built-in coach generator.
The type of batteries, the size and length of the cable, the large stock alternator, and the quiet engine idle made this type of quick and convenient boost coach battery charging possible. I can monitor this happening because of a digital ammeter and digital voltmeter mounted on the dash in the cab.
When on the open road between camping sites for 4-5 hours, the engine alternator will bring the coach batteries to 100% ... which I can determine because at that point current is no longer flowing into the batteries according to the ammeter.
Before solar and quiet small generators, idling the main engine was the only way to top up coach batteries. I had a 1969 Chinook motorhome way back when for awhile that was designed to use this method ... except it's alternator wasn't anywhere near the capacity of modern ones.
