Charging While Towing

[mattherrington]

Newbie to the forum here. Looked around a bit and didn't see anything specific so worth a fresh post.

We just took our first long trip in my 16ft TT after I installed a new (4)6-volt 460AH system in lieu of the single group 27 marine battery. Installed a Victron 700-BVM which was/is the coolest gadget. Love the AH consumed/charged function as that and voltage were my real measurements of state of charge. Didn't quite like the percentage used so that'll take a little programming change (hopefully).

Overall on the six night trip we used 170AH with the kids watching DVDs every night, ending voltage when we got home was around 12.25V. Pretty respectable. Just the smoke detector, carbon monoxide, propane detector, propane fridge controls, and a USB that stays hot draws about .85A an hour and if we were out for the day I'd just shut it down.

To my surprise though I didn't get the charge I thought I would when we were out on the road. We relocated twice 2-3 hours each and drove home 8 hours yesterday and the change in AH and voltage was seemingly negligible each time.

I've got a 30A lead wired from a empty fuse slot to the 7-pin connector. My big battery system install is right to the original connection points on the TT to keep things simple. When I start the truck I can see the Amps inbound to the trailer peak at about 5A but then really quickly it dropped down to 1/0/-.85. The AH meter moves backwards and forwards so I recorded a little dent in AH used right at startup but that was it.

My simple math said even at 5A inbound I'd see a real dent in total AH consumed on our crazy long drive home and it was at 175AH when we left and 171AH when we got home. Every time it basically felt like it was a wash and I thought I'd see a 30-40AH pickup after a whole day on the road. Truck voltage the whole ride was considerably above (runs around 13.4 to 13.6 on the move) the trailer batteries in the mid/low 12's.

Only thing I can come up with is that I run full lights on (lights on for safety!) all the time and the running/marker/brake lights on the trailer are still incandescent and that's consuming most of that trailer feed?

Seems like I'm missing something. Any insight from you experienced folk would be appreciated.

[brulaz]

Is that battery box vented to the outside?
And a sealed plastic box perhaps to protect against spills?

My previous trailer had two GC2s in a plastic box inside, with maybe 2" flexible plastic hose out the top, maybe 2' long, going to the outside.

[theoldwizard1]

Bedlam wrote:
I have a constant duty solenoid and 150A breaker under the truck hood going to a 2ga run to the receiver with an Anderson connector. My trailer batteries also have have 150A breaker to a short 2ga run and Anderson connector on the tongue so I get better vehicle charging.

My setup is slightly different because I also run 2-way power to my truck camper and have two banks of batteries in my truck in addition to the bank in the trailer.
.
.
.
As was already posted, it does not fully recharge my battery bank but it will bring it up before shore power or solar top them off with an intelligent charger.

A very nice, clean installation ! As long as you understand the limitations of your system and can live with them, you are fine.

Personally, I would go withe the CTEK D250SA DC > DC Charger. They make an add-on device that can do high current charging if your TV can make the power.

[mattherrington]

profdant139 wrote:
For someone who says he's electricity dumb, you sound like you are doing quite well! Just FYI, I have a similar trailer (even smaller), and we get along great with a 120 watt portable solar -- plug and play, easy to use, store, and deploy. There are pluses and minuses to rooftop systems (or should I say positives and negatives?).

Also, replace those incandescent bulbs with warm white LEDs asap -- big savings on juice!

And welcome to the forums! What kind of a trailer do you have, and where are you going next?

It's a 2015 Pacific Coachworks Mighty Lite 16BB that somehow didn't sell, got repo'd, something and went to auction where it got bought/flipped to me last summer. Had all the manuals, dealer prep delivery checklists, but couldn't find a scratch on it. I was really just picking around for a 3,000 lb trailer with bunks AND a full and as few moving pieces as possible. Somehow I got it matching my rig!

This electricity thing was just my second real mod. First was to upsize from those scary 14" pizza cutters to a D-rated 215/75R15 LT tire, over/under the axle, and mount some Monroe gas shocks under there all with the intent of dragging it down a bunch of off road trails.

Next up is some dispersed wilderness near Sequoia NP and down into Kings Canyon NP by the river.

[Bedlam]

I have a constant duty solenoid and 150A breaker under the truck hood going to a 2ga run to the receiver with an Anderson connector. My trailer batteries also have have 150A breaker to a short 2ga run and Anderson connector on the tongue so I get better vehicle charging.

My setup is slightly different because I also run 2-way power to my truck camper and have two banks of batteries in my truck in addition to the bank in the trailer.









As was already posted, it does not fully recharge my battery bank but it will bring it up before shore power or solar top them off with an intelligent charger.

[SoundGuy]

brulaz wrote:
So installed a left-over 1000W inverter in the truck (which has a 220A alternator).

SoundGuy wrote:
Curious - did you install the inverter under the hood or elsewhere, how long is the run to the inverter input, what input cable gauge did you use, and did you connect directly to the starting battery or elsewhere? :@

brulaz wrote:
Its in the bed of the truck on a shelf behind the cab and under the cap.

Didn't want the hassle of putting it in the cab ...

And I didn't trust the heat and possible water in the engine compartment.

The wires are some extra 6 awg I had around, with a 60A Maxi fuse and 140A (13.3V on, 12.8V off) Princess Auto isolator.

The + and - wires comes off the truck's passenger side battery terminal (diesel truck with 2 batteries)...

I've got the same Motomaster inverter, currently mounted in the trailer's front pass through cargo compartment, so thanks for the info ... I'll have to muse on this as an option. :B

[SoundGuy]

brulaz wrote:
So installed a left-over 1000W inverter in the truck (which has a 220A alternator). Good for other things too (like charging tool batteries), but primarily use it to run a 650W battery charger in the trailer. Added an extension cord with water tight couplings between truck and trailer and we're good.

theoldwizard1 wrote:
That will work ! Not as "clean"/simple install as a DC-DC charger, but if you have the "left-over" inverter, it IS less expensive !

brulaz wrote:
One advantage is that you can use an existing more sophisticated 120VAC charger in the trailer. One with temperature compensation and multi-stage charging.

The CTEK D250SA DC > DC Charger is specifically designed for this purpose and includes temperature compensated charging. :B

[GordonThree]

When I need to charge while towing, I fire up my little blue friend and let it run in the truck bed. it gets plenty of cooling while in motion, and you can't hear it at all once at highway speed.

[BFL13]

Inverter in the engine compartment dubious due to heat. When idling, hood up, inverter on fender by battery, it quit from overheating. Had to hang the inverter out over the fender to get it away from engine heat.

[brulaz]

theoldwizard1 wrote:

brulaz wrote:
So installed a left-over 1000W inverter in the truck (which has a 220A alternator). Good for other things too (like charging tool batteries), but primarily use it to run a 650W battery charger in the trailer. Added an extension cord with water tight couplings between truck and trailer and we're good.

That will work ! Not as "clean"/simple install as a DC-DC charger, but if you have the "left-over" inverter, it IS less expensive !

One advantage is that you can use an existing more sophisticated 120VAC charger in the trailer. One with temperature compensation and multi-stage charging.

[brulaz]

SoundGuy wrote:

brulaz wrote:
So installed a left-over 1000W inverter in the truck (which has a 220A alternator). Good for other things too (like charging tool batteries), but primarily use it to run a 650W battery charger in the trailer. Added an extension cord with water tight couplings between truck and trailer and we're good.

Curious - did you install the inverter under the hood or elsewhere, how long is the run to the inverter input, what input cable gauge did you use, and did you connect directly to the starting battery or elsewhere? :@

Its in the bed of the truck on a shelf behind the cab and under the cap. Makes it easy to use for charging tools, as I can open the side door of the cap and get at it. Also I can see the display (it's one of the Cantire 1000W PSWs) from inside the Reg/Std cab.

Didn't want the hassle of putting it in the cab, and the fan noise may also have been an issue. It's a Reg/Std cab so space is at a premium and noise carries. (Still don't know how best to get big wires through the firewall.) And I didn't trust the heat and possible water in the engine compartment. Besides there's very little room there as well.

The wires are 6 awg with a 60A Maxi fuse and 140A (13.3V on, 12.8V off) Princess Auto isolator. The wire goes under the cab and being a Std/Reg cab it's ~15 ft. That 60A is all I need for the trailer's 500-700W charger, and tool charging.

The + and - wires comes off the truck's passenger side battery terminal (diesel truck with 2 batteries), on top of all the fuses and other wires there. The 220A alternator is close by with fat wires to the battery.

I never see less than 13V at the inverter, usually over 14V. There's definitely voltage drop and wasted energy but with that big alternator it doesn't really matter. But if I wanted to use the full 1000W of the inverter, I'd would have to go up in wire/fuse size or move the inverter into the cab or engine compartment. But for now it's all I need.

[jkwilson]

DavidP wrote:

Not exactly. The remote/trailer battery will receive the full voltage the tow vehicle provides but the tow vehicle in many applications and in all modern (factory install) cases uses a battery isolator to protect from discharge of heavy loads and rapid discharge of the remote/trailer. True they are installed in parallel but it is one sided. No matter the state of charge/discharge of the trailer battery the tow vehicle battery is isolated from loads/discharge originating from the remote/trailer battery

I've never seen one with any kind of isolator. At best you have a relay and a fuse to break the connection when the key is off, but many vehicles only have a fuse.

[SoundGuy]

brulaz wrote:
So installed a left-over 1000W inverter in the truck (which has a 220A alternator). Good for other things too (like charging tool batteries), but primarily use it to run a 650W battery charger in the trailer. Added an extension cord with water tight couplings between truck and trailer and we're good.

Curious - did you install the inverter under the hood or elsewhere, how long is the run to the inverter input, what input cable gauge did you use, and did you connect directly to the starting battery or elsewhere? :@

[theoldwizard1]

DavidP wrote:

Not exactly. The remote/trailer battery will receive the full voltage the tow vehicle provides but the tow vehicle in many applications and in all (?) modern (factory install) cases uses a battery isolator to protect from discharge of heavy loads and rapid discharge of the remote/trailer. True they are installed in parallel but it is one sided. No matter the state of charge/discharge of the trailer battery the tow vehicle battery is isolated from loads/discharge originating from the remote/trailer battery

I disagree with this statement !

If have looked at a few different wiring diagrams (mostly Ford products) and there is NO ISOLATOR between the vehicle battery and the 7 pin trailer connector. Usually just a fuse and a relay.

Voltage drop from the vehicle battery to the trailer battery IS MEASURABLE ! Easily 0.2V-0.8V depending on the gauge of the wire, and the "condition" of any connectors. Modern vehicle charging system typically put out about 13.2V-13.6V most of the time. Subtract the voltage drop and you just don't have enough voltage at the house battery to properly charge it.

[theoldwizard1]

brulaz wrote:
So installed a left-over 1000W inverter in the truck (which has a 220A alternator). Good for other things too (like charging tool batteries), but primarily use it to run a 650W battery charger in the trailer. Added an extension cord with water tight couplings between truck and trailer and we're good.

That will work ! Not as "clean"/simple install as a DC-DC charger, but if you have the "left-over" inverter, it IS less expensive !