IDEA...charging house battery(set) underway.

Yes most of the threads about this stress the need to run your wires from the alternator itself and not from the vehicle battery if you want decent amps and also to bypass the voltage regulator IIRC also something about temperature under the hood knocking truck voltage down.

That's why I mentioned in my initial reply that the OP's inverter/truck connection might allow for a higher truck limit than what I got. There will still be a limit.

I forgot to mention in my case, the inverter had to be hanging outside the engine compartment in cooler air. It overheated sitting up near the battery with the hood up. Ok for doing it when parked. No idea where you could mount the inverter close to the engine area for going down the road like the OP wants.

The gen in the back of the truck thing sort of worked when I tried that out. Every so often the Honda would quit. Speculation in a thread about that was vortex air messing up the Honda air intake, also bumps disturbing the oil level, whatever. I had to pull over and restart the Honda when it happened--or rather when I noticed it had stopped, which was who knows how long after it did stop.

If you are willing to spend bucks on this, and your alternator has an external regulator (or could be wired that way) by far the best solution would be to fit a SMART REGULATOR. Similar to smart charger (120 VAC), in that it has different voltages for bulk, absorption and float. Inverting 12 VDC to 120 VAC and then back to 12 VDC has a lot of build-in efficiency losses and extra complexity.

Used this one on the sailboat 120 amp alternator-- did all the battery charging for months at a time: http://www.westmarine.com/high-output-alternators/balmar--ars-5-12-volt-regulator--7807969

A problem with this is the cabling used between alternator and battery by the vehicle manufacturer, and why I suspect higher RPM's made no difference in BFL13's case. This cabling is not adequate to pass high currents for long, It was designed to be just adequate for the briefly lasting loads expected by the stock systems and a battery which never goes below 90% and can never ask for much. The bean counters won again.

This can be negated with a fatter cable between alternator and battery. I've done this, just adding a parallel circuit and the amperage increase is close to 60% when the house battery(s) are depleted and the RPM's are there.
I just have this pecky 13.7 volt issue where my engine computer located voltage regulator will randomly decide that 13.7 is fine and dandy, even when the batteries are crying for 14.8v.

Using an INverter on the engine battery to power a regular battery charger is Standard procedure In Australia, especially when the 'caravan' is towed and quite a distance from the alternator.

My alternator, rated at 130 amps can barely make 32 amps at hot Idle, so If I were to employ this system, I would be robbing peter to pay paul whenever idling.

Dunno if this will work for other folks, but I picked up a 50ft 12 gauge outdoor extension cord from Menards for $50... I cut off the regular outlet end and put on a twist-lock end that fits my trailer. Then I strung it under the trailer inside the box sections of the frame (there are access holes cut already). The male end coils up and hangs on the propane tank clamping bar.

After I boondock, during the next driving day I fire up my Yamaha in the bed of the truck and plug in the trailer. Once I'm at highway speed I can't hear the generator anymore, and it gets plenty of cooling air. Usually the batteries are charged in a few hours when I stop for a stretch, and I can shut off the generator.

The truck would run but the battery would get run down with low voltage I suppose. Anyway, lots of people run inverters from their trucks one way or another and you could charge a set of other batteries with a charger from the inverter. The Devil is in the details.

Try it out.

BFL13 wrote:
The MSW didn't matter with the Vector charger, but it would matter with the PD converter. That brand is known to need PSW where a WFCO does not ISTR.

I don't know how the truck's 12v system all works. I gather they have some variations in what you can do among different trucks. I described what happened in my case. My alternator is 105amps.

I figure the same sort of thing will happen with any version of that method, but the limiting factor amounts would be different. Same limiting factors though. Inverter limit and truck limit.

Only way to find out what yours will do is try it.

BTW it is no use running the inverter at just above its alarm off voltage for its input, when the truck won't run on that low a voltage. You have to keep the truck's voltage up to normal 14v. It (mine)doesn't sag down a little below 14 and stay there. Once it starts to sag it just keeps dropping like a collapse.

Your truck SHOULD run on 12.0 volts for certain, and most probably as low as 10-11 volts, the latter possibly with ABS (and other) fault lights, but "run" she should.

Remember that the goal is to reliably and safely charge the house battery while underway, no engine idling issue there.

Hi,

The cut off point for me is 12.9 volts. When that is displayed I reduce the load on the alternator.

The MSW didn't matter with the Vector charger, but it would matter with the PD converter. That brand is known to need PSW where a WFCO does not ISTR.

I don't know how the truck's 12v system all works. I gather they have some variations in what you can do among different trucks. I described what happened in my case. My alternator is 105amps.

I figure the same sort of thing will happen with any version of that method, but the limiting factor amounts would be different. Same limiting factors though. Inverter limit and truck limit.

Only way to find out what yours will do is try it.

BTW it is no use running the inverter at just above its alarm off voltage for its input, when the truck won't run on that low a voltage. You have to keep the truck's voltage up to normal 14v. It (mine)doesn't sag down a little below 14 and stay there. Once it starts to sag it just keeps dropping like a collapse.

BFL13 wrote:
I don't think the 750w inverter nor the 1000w one will do the job as described. eg, the PD converter has a power factor of 0.7 which makes its VA draw on the inverter near or over 1000.

1000VA ONLY at full load, 55A (maximum)charging rate to house battery = ~65A input current to the inverter. Additional loads on the PD should be minimal when underway.

Meanwhile the alternator has to be able to run the inverter and the vehicle and there are limits to that. I tried a version of doing that charging method and posted about it some time ago.

In my case I powered a 600w Vector 35a charger from a 1000w MSW inverter (no advantage to have PSW for this job) that worked ok, but the limit was in the truck.

The inverter was connected to the truck's battery with short fat wires so that was ok.

The truck engine running (in idle--revving made no difference with this truck)

That seems not just improbable but practically impossible.

As the engine revs rise the amperage production capability of the alternator will rise accordingly. Unless this particular alternator could produce maximum current output (90A?) at or near idle and that maximum current was somehow being "used" at the time. Both highly unlikely.

Or was the chassis battery (and house?) fully, DEEPLY, discharged during your test?

was able to keep the truck's voltage (dash meter) needle pointing up at 14v as long as the inverter load was not too much.

But what was the total of other loads on the chassis alternator/VR system>

When I tried to increase the inverter load by adding a second Vector charger but set to less than 35a at the 20a, I found the inverter could handle it (300w at 20a vs 600w at 35a so 900w total) but now the truck's voltage fell off, needle sagging down to the left. 10a more ok needle stays up quivering like it is on the verge of sagging down to the left again. So that is the limit. Got to keep the truck's voltage holding at 14v. (It helped when I shut off the truck's climate control too!)



So the OP set-up could work given that:

-the chosen inverter is high enough in watts to supply the VA draw of the PD converter, and
-The vehicle's 12v supply will be 'strong' enough to run the inverter plus the vehicles own requirements to hold its voltage at 14v.

Most MSW inverters do not shut down until the input voltage drops to <10.5volts

I know you can do better connecting from the alternator instead of the battery, so the OP method could be better than what I did for that part.

The factory wiring between the alternator and chassis battery will not be critical at the maximum charging rate to the battery.

PS: What was (is?) your alternator output rating?

I don't think the 750w inverter nor the 1000w one will do the job as described. eg, the PD converter has a power factor of 0.7 which makes its VA draw on the inverter near or over 1000.

Meanwhile the alternator has to be able to run the inverter and the vehicle and there are limits to that. I tried a version of doing that charging method and posted about it some time ago.

In my case I powered a 600w Vector 35a charger from a 1000w MSW inverter (no advantage to have PSW for this job) that worked ok, but the limit was in the truck.

The inverter was connected to the truck's battery with short fat wires so that was ok. The truck engine running (in idle--revving made no difference with this truck) was able to keep the truck's voltage (dash meter) needle pointing up at 14v as long as the inverter load was not too much.

When I tried to increase the inverter load by adding a second Vector charger but set to less than 35a at the 20a, I found the inverter could handle it (300w at 20a vs 600w at 35a so 900w total) but now the truck's voltage fell off, needle sagging down to the left. 10a more ok needle stays up quivering like it is on the verge of sagging down to the left again. So that is the limit. Got to keep the truck's voltage holding at 14v. (It helped when I shut off the truck's climate control too!)

So the OP set-up could work given that:

-the chosen inverter is high enough in watts to supply the VA draw of the PD converter, and
-The vehicle's 12v supply will be 'strong' enough to run the inverter plus the vehicles own requirements to hold its voltage at 14v. I know you can do better connecting from the alternator instead of the battery, so the OP method could be better than what I did for that part.