Trailer Battery Charging: Solar? DC-DC?

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woytovich

woytovich

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I'm setting up my car trailer and I'd like to add a winch and a battery for it. I am doing some research on what to do to keep the battery charged and I'm seeking some input. I'd like to use the battery for the winch (VERY occasionally) and to power some 12v LED work lights mounted to the trailer. For the winch I wil' most always be hooked up to the tow vehicle... for the work lights not always.

I have read that some people run a small-ish (10ga) fused wire from the tow vehicle battery to the trailer battery - simple, but isn't that just a redneck dual battery system? And this needs to be disconnected whenever high load is put on ANY part of the system to prevent unintentional draw of a lot of amps through that 10ga wire.

I know there is at least 1 DC-DC charger out there but it is $$$ and this is not that critical an application:
http://www.ctek.com/lu/en/chargers/D250S DUAL

I was looking at some relatively inexpensive solar solutions like the 10w BatteryTender Solar kit:
http://www.amazon.com/Battery-Tender-021-1164-Solar-Charger/dp/B004Q86JJ8?tag=ihco-20

There is adding the trailer battery as half of a properly set-up (isolated) dual battery system with heavy gauge wire back to the trailer... again, this seems like overkill.

And I COULD just resolve to use long leads (jumper cables) to run the winch on the rare occasions I'll need it and use some sort of portable 12v power supply if I want to run the lights when not connected to the tow vehicle.


Thoughts?

What have you done in a similar situation?

Thanks!
Mark
 
I will be able to 120v charge the battery between trips out so it'll start every trip fully charged.
 
the bit with the 10ga wire indeed better be limited I think to low draws on the trailer battery. And if so should be fine probably. With a winch running on the trailer that's probably not a good idea if the wire runs under carpet etc.

10W is nothing. Take your typical 100Ah battery. 10W is less than 1A. (Very) roughly speaking, picture needing well over 100 hrs to charge the battery with a 10W solar charger. That'd be like 2 weeks.
 
I think I would get some 1# or 2# welding lead and Anderson clips.

Run it from the battery down the frame to rear, put the Anderson connection in the bumper, then make an applicable set with clamps for the trailer side. Just plug in while winching. I don't think you'll be using any huge battery whallop, because you're only using it with rolling resistance. ...not like the truck is stuck.

Battery tender while trailer is sitting, and reg 10# to keep it topped off while moving.

I have a set of extra red/black copper clamps if you want them.
 
So Pat, what you are saying is "all of the above" more or less?
 
Maybe i'll just pull the battery out when it is going to be parked for extended periods and put it on a Tender in the shed. Then a #10 wire for the drive times.

The trailer brake battery charges through the regular harness so that is not part of this.

Add a Disconnect for the #10 when winching to prevent the winch drawing thru it. The stand alone battery should be able to handle the occasional pull of the winch AND use of led work lights for quite a while.
 
When I bought our TrailBlazer camp trailer it was set up for remote Baja excursions. It had 2/0 cable in Anderson connectors that ran it's full length, stopping off at the batteries. The dedicated tow rig had a Warn M6 in a cradle (made well before Warn offered such a thing) that could plug into either it's receiver hitch, or the trailer's receiver hitch. The tow rig's connector was mounted flush in the face of the custom rear bumper. The pair of red top batteries were charged by these cables. I've no idea what the tow rig for a battery separation scheme, but unplugging the trailer was most certainly not it.

Over on the Tear-drops & Tiny Trailers forum there is a small following who put an inverter on the tow rig, and run an extension cord back to the 120VAC on-board battery charger. The idea offends me from an efficiency point of view, but it does have some advantages worth considering.

We have a pair of Trojan T-125's in our pop-top camper. I monitor them with a Bogart Engineering Tri-Metric. I use a BEP Marine VSR (fed with 6ga. cable) to charge the camper batteries after the starting batteries are topped-off and have an on-board Battery Tender 120VAC charger. All lights are LED, rarely run the water pump or Fantastic Fan, and only ever run the fridge on DC while the engine is running or will be very soon.
Since installing a 100W solar panel and a SunSaver Duo solar charge controller I've never seen those batteries below 96% SoC. It's actually a little worrisome, I'd like to see them get cycled a little more than that.

Something to consider, seems obvious but gets over-looked often (I did!), the charge wire needs a breaker or fuse at BOTH ENDS. If you use a manual reset breaker then it is easy to break the circuit for winching, and it'll break on it's own if you forget.
 
woytovich said:
So Pat, what you are saying is "all of the above" more or less?
Click to expand...


I'm thinking all the above.

Without seeing it ( and if we discussed it, it has eluded me at the moment) I would think that in order to pull the 60 (or something in that weight range) on the trailer, you need to power an 8000# range winch.

Although it's not like pulling it out of mud, or up a 45 degree slope, still all and all, it's a pull that will require some steady power.

That being said, maybe some of the guys that winch and load there60/80's could jump in here, but I'm not sure a battery in good shape will have enough ass to pull a vehicle up om a trailer before draining it down dead, which is bad. That's why I'm thinking good heavy leads, designed to handle welding tasks, installed at the truck battery, fused with some thing to protect the system, and run down the frame of the Yukon, and run it to the rear with some flush mount Anderson clips in the rear bumper, or perphaps protected inside from the elements . Then take and make up a set of "jumper cables"....one side Anderson clips to plug into the truck, to take advantage of the charging from the truck alternator, and the truck battery. The other side would be like conventional battery clamps, or with the right battery, you could use copper eyelets and wingnuts.

Not sure what battery you had in mind, or your budget, but I think at a group 31 or 34. That should have enough combined with the altenator, to drag anything you need to on the trailer.

As far as maintaining a charge on the trailer battery, the conventional (separate, fused with a 30amp) #10 would be fine to keep it topped off while driving. At home I would think a battery tender, or a 100 watt solar setup to maintain would be fine .

If you need further assistance, or its something want to discuss just call. I do have some spare stuff lying around as well.

Don't forget that NYS requires a "breakaway" system to engage the trailer brakes in the event of a catastrophic uncoupling, and that battery needs to be tied into something to keep it topped off too.
 
The trailer has a breakaway setup with its own battery.

I think a good battery would have no trouble pulling the 60 up onto the trailer... The alternator is not going to be able to do it on its own and is only going to add a little bit to the equation during winching.

I like the idea of full battery power at the back of the Yukon to run the winch.

How about a dual battery setup with the second battery in the back of the Yukon. That way it is close to the trailer and will be available in the Yukon all other times AND will stay charged always. Still do the Andesen connector rig to get power to the trailer. Only problem is there is no power for the work lights on the trailer unless it is hooked to the Yukon....

If I do put the battery on the trailer, #10 to keep it charged while driving etc AND have a set of long jumper cables as a back up if i need to connect tow vehicle battery to trailer winch if the trailer battery fails....

Arggghh need to sleep on this....
 
I think there would be a lot to be said, for treating the trailer like the #2 battery in a dual battery system. Given the voltage drop on a long run to a trailer, 10g is not going to cut it. It may charge, but so slowly it likely won't matter. Still, an alternator is way more powerful than any solar, so it would be nice to have that option to charge the #2 battery.

I like the idea of a split charge relay at the main battery, feeding 2g cable back to an Anderson plug at the bumper, then another Anderson plug and 2ga wire feeding the trailer. With appropriate fuses on both ends, so you don't burn down your truck in the event of a short. That should net fast, efficient, safe charging, with a solar panel to back up the whole thing when camping.

Just remember that voltage drop is your enemy in low voltage systems, so you need much bigger wiring to compensate.
Concentrate on fast reliable charging of your trailer battery and you will be fine. I would not put a battery in the back of your Yukon. You just don't need it.

It would look like this:

Main battery>Blue Sea ACR>Fuse>2ga wire>Anderson Plugs>2ga wire>Fuse>Trailer Battery. You could fuse it with 100-150 amp fuses to protect the wires (and your truck) in the event of a short.

10 watts of solar is nothing. I would not bother. Having a smart charger for shore power at home is a good idea. I like the BatteryMinders but I'm sure any legitimate brand will work.
 
I think that I'd slightly alter what CruiserDrew is suggesting. Put a marine battery bank switch in parallel with the ACR/VSR & breaker/fuse. Set it up such that with the switch off you still get charging, but at a breakered, reasonable current limit. If you need more for winching etc. then turn the switch on, which by-passes both the ACR/VSR and the breaker.

Put all of the trailer loads on one battery; winch, lighting, & break-away.

Solar if there's a place for it on the trailer. Say that's a 100W panel. That's best case, sun at just the right angle, clear, cloudless day, preferably a cold day. Any deviation from those ideals will cause a significant reduction in output. A little over-kill on solar isn't a bad thing at all.
 
I thought about switching the breakaway to them full size batttery but it is all brand new so Ill likely leave that part alone.

As far as the bypass, i would then need to be sure the wire could handle the amps that the winch might draw, and that is going to be much higher than the charging demand. If this were for a rear winch in a wheeling vehicle then i would do that, but the NEED for this trailer winch is not that critical.
 
ntsqd said:
I think that I'd slightly alter what CruiserDrew is suggesting. Put a marine battery bank switch in parallel with the ACR/VSR & breaker/fuse. Set it up such that with the switch off you still get charging, but at a breakered, reasonable current limit. If you need more for winching etc. then turn the switch on, which by-passes both the ACR/VSR and the breaker.

Put all of the trailer loads on one battery; winch, lighting, & break-away.

Solar if there's a place for it on the trailer. Say that's a 100W panel. That's best case, sun at just the right angle, clear, cloudless day, preferably a cold day. Any deviation from those ideals will cause a significant reduction in output. A little over-kill on solar isn't a bad thing at all.
Click to expand...

Actually, this would work fine. Very common to have a charge relay bypassed by a switch. In fact you can buy that pre-packaged combo from Blue Sea.

Still just a charged battery and a winch will load a truck on the trailer 100% of the time, so you may not need to get too fancy. One other thing to consider is that you can always add the switched part later, if your winching needs are so great that the battery alone isn't working. You can even use the same main wires if you use at least 2 ga to start. (Rule of thumb, but consider your winch lines are 2ga to start with)

The nice part about a charging relay is it will disconnect the loads if voltage drops on one side of the relay. So if winching, you'll get a big voltage drop (to around 8 volts typically) the relay will open anyway protecting your main battery. The Blue Sea also has an isolation circuit that you could trigger automatically that would open the relay and prevent any unintentional draw down. You could even run the start isolation circuit to a switch, and turn it off anytime you feel it's an issue.

I think most people over plan for rare-to-never events like dual battery winching, or self jumpstarting. Plan for common events like 2 charged batteries, and add the rest as needs surface.

The universal problem with charging a trailer battery from the alternator is wires that are too small resulting in so much voltage drop the trailer battery will hardly charge.

I'm not sure where solar plays for you in this, but that would be the thing I would do last unless you stay in remote sunny places and run a 12v fridge. Otherwise not needed for what you describe.
 
you don't need a whole lot of winch power to pull a rolling vehicle up on the trailer.... as long as it has 4 tires and rolls off a hard surface.
 
Even just for a trailer battery charging only circuit I would seriously consider running both power and a ground cable. The ground path without a cable isn't all that great and will drop the voltage.
 
ntsqd said:
Even just for a trailer battery charging only circuit I would seriously consider running both power and a ground cable. The ground path without a cable isn't all that great and will drop the voltage.
Click to expand...


No question about it. Definitely need a return ground, not a chassis ground. And, it needs to be fused at both batteries, no matter what. If you use 2ga which would be my recommendation, you can fuse with 150 amp fuses and forget about it.
 
Yeah, I think the dual battery route is where I am going to go. That seems to provide the most functionality with the least messing around. I'll use Andersen connectors to get the power to the trailer.

Thanks for the link Elbert... I have some of the wiring here already... just need to settle on the "brains" of the system.
 
woytovich said:
Yeah, I think the dual battery route is where I am going to go. That seems to provide the most functionality with the least messing around. I'll use Andersen connectors to get the power to the trailer.

Thanks for the link Elbert... I have some of the wiring here already... just need to settle on the "brains" of the system.
Click to expand...

Your talking two batteries in the truck....or one still at the trailer?
(Just for clarity)
 
One in the truck, one on the trailer.
 
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