How much gas does your genny use? And a charging question

Let me get this straight....
You're running your vehicle to provide 12v to the inverter to provide 120v to a charger to provide 12v to a battery.

doesn't your vehicle charge batteries off the alternator? :h

I use my Honda EU1000i late evening to bed time. 5 hours on about a quart of gas or less. I start the Honda when my house batteries get to 12.5 volts. I set the charge rate at 5amps on my Inverter/Charger. This allows the TV, 2 computers, the ice maker, and what lights that are needed to run. Fridge is on gas. By bedtime, the batteries are in the float stage. 13.2 volts.

I once had a Honda 1000W generator that I used to re-charge two 12v batteries on my TT. It was very quiet and would run all day on about 1/2 gallon of gas.

The 1000w was enough to run lights, TV and VCR at night and then charge batteries the next day.

It worked great when boondocking.

From your posting a few weeks ago & now that you have experienced first hand, attempting to charge via the vehicle, I think the conclusion as was stated by several responses then.

In your circumstances, you need a small generator & a good smart charger when dry camping.

Any small genny uses very little gas & in the long run will suit the purpose & pay for itself with less fuel consumption.

My Vector smart chargers work ok on MSW.

How did you measure that amount of recharge achieved for the comparison of times?

You would need to start from the same state of charge (SOC) and get to the same higher SOC and compare the times. It is fairly simple to get the starting SOC from a "mostly" resting voltage (nothing much 12v running at the time) it is very hard to determine the subsequent SOC as charging proceeds because now your battery voltage rises, and your hydrometer is behind the problem due to "SG lag"

If you have an amps read-out on the charger that helps a lot. My "marker" for 90% SOC when to stop the charge is when amps have tapered down to 5 amps per 110AH of bank at 14.5 volts. eg with a pair of 27s at 110AH each, that would be when amps are down to 10 amps.

Anyway, without some way to tell charging progress, how can you say it takes three times longer using that method?

Hi,

The charger doesn't "like" the wave form from the MSW inverter.

Running your van engine to charge the batteries is rather wasteful, both of gasoline and of engine life on the van. I've a little ECQ 1800 watt inverter generator that will run for about 5 hours on the quart of fuel in its tank. I've also got a 5500 watt open frame generator that will run for at least 12 hours on 7 gallons of fuel, a lot longer (but I don't know how long) on a light load such as a 30 amp battery charger (which, after all, claims to provide only 360 watts worth of charge to the battery). What you did is in some ways equivalent to hitching up a full-size bulldozer to pull up your tent stakes.

I'm thinking that the reason that your battery charger took so long is the MSW inverter you used to feed it. Obviously I've no knowledge of the circuitry in that charger, but I suspect that it would be much faster if feed from a pure sine wave power supply. Most battery chargers of the automotive sort use a transformer to reduce the voltage to 12 from 120, (at least the ones I've seen), and a transformer is only going to provide power during the rise/fall time of the waveform, meaning that for most of the cycle, they will yield nothing, thus being very inefficient.

I quite understand the costs involved in buying a suitable small generator. I passed through a Northern Tools store just yesterday and saw that they had a pile of 2000 watt inverter generators of their own Powerhorse brand claiming to run at only 52 dB noise level (which is quieter than Hondas, albeit not by much) for only $599.

Do be aware that for running that battery charger, even one of those tiny 900 watt, 2 cycle, $99 Harbor Freight generators is quite adequate.

I find it odd the charging took 3x as long as at home. More likely the battery was lower on charge than you think. Did you monitor the charge to verify it was not shutting down intermittently? Need an ammeter to verify the charger is working same on inverter vs. utility power. Most don't charge to 100% while camped because the last 10% does take an extended period.

My honda eu3000 will run twenty hours on 3.5 gallons of gas on eco mode which would be plenty to run a charger. That's weird that it took three times as long with the inverter unless of course its not supplying your inverter with enough power. In which case maybe that is not good for your charger.