Single Battery 12V only expo trailer build recommendations

[Hoologan]

Hi guys,

I want to install a single AGM battery in my Smitty Scout trailer to run 12V lights, USB ports, and a water pump. I don't need 110VAC, but I would like the ability to charge the battery via shore power at camp or in the garage when stored. I would also like the ability to add a solar panel later.

Is there an affordable charger on the market that will handle a shore power input, a solar input AND an input from the tow vehicle's alternator? Most of the ones I've seen are dual input solar/alternator, but no shore power input, for instance, the CTEK D250SA (unless I'm missing something).

Thanks in advance!

 

[john61ct]

No, and you are better off buying quality gear that is single function.

Of course good stuff costs, lots more than even the best battery.

Focus on the batt and charging from mains / genny first.

Where are you?

 

[luthj]

Alt charging from the tow harness is usually a futile endeavor. The factory wiring is small, and voltage drops mean that charge rates are very slow. Since your electrical needs are modest, a 3-5A shore power charger would suffice. Just pick one with a true 3 stage charge algorithm, and correct voltages.

A quality solar controller, such as the victron 15A unit, will have monitoring options, and is a good choice. Combined with a 100-200W panel, and you should have minimal needs such as you describe covered.

 

[rayra]

'futile endeavour's hindquarters. The aux power on a 7-pin is typically fused at 15amps. You think it's delivering less usable power than your 3-5A shore power charger?
All sorts of folks in the Tiny Trailer hobby would be suprised to learn their trailer connector is a 'futile endeavour'.

 

[dreadlocks]

first of all, screw AGM honestly.. your paying extra money for a shorter lifespan, plain and simple.. FLA is alot more reliable and can take far more typical abuse that most people give when camping.

in my experience, the aux 7pin provides about 4A of charging power maximum as measured at the trailer battery on my last 2 vehicles, my shore power charger provides 45A of power.. 6h of driving barely puts 25% charge back in my battery whereas 6h of shore power completely charges my battery.. so yeah, unless you drive >8h every single day.. you should focus on external charger.. my previous setup involved a 100AH AGM and charging only via trailer plug, was a terrible mistake.. battery lasted one season then crapped out on me in the middle of a 2 week vacation at the beginning of its second season.. learned that lesson the hard way.

 

[john61ct]

A high quality heavy gauge wire run straight from the alt/starter circuit to the van bank through an Anderson plug

is certainly better than the usual stock dinky trailer wiring.

I shoot for well over 40A charging whenever possible.

 

[dreadlocks]

eh, a single deep cycle FLA battery is unlikely to even take 40A, the ones I've used might take >20A for a little bit but they spend the vast majority of the bulk charge between 8-15A when hooked to a large charger.. now if you start running multiple batteries or absurdly large batteries then yeah sure.. otherwise 40A charging capacity will be largely unrealized unless you go for a Lithium.

 

[john61ct]

Or go to a high-CAR AGM, or expand to a higher AH capacity.

But the point is also lower resistance, not just for fire safety but minimizing voltage drop.

In some cases eliminate the need for a DCDC charger completely.

 

[dreadlocks]

I get what your doing, but its really not needed.. if you run 20A @ 1% through the blusea calculator it tells you to run the same cable as 40A @ 3% voltage drop.. so just change the voltage drop to minimal instead of doubling up on amperage and you get the same results.. for working with his alternator ok fine, but this dont mean he should go buy a 40A shore charger for a single 12v deep cycle on a little smitty that he admits he has minimal electrical requirements for.. but he absolutely should wire up charge sources for minimal voltage drop for best results, overkill here is good and design for more than needed, better to have it and not need it than need it and not have it.. right now he's being limited by his wiring and that sucks and needs to be avoided.

 

[john61ct]

If that was addressed to me, I never said anything about mains charging. Which would presumably go close to the target bank anyway.

Yes topic here is charging off the alt.

Lowering amps to keep V high is fine for those driving for many hours per day.

Ideal for general use is as many amps as possible, and Absorb voltage in spec.

Going to heavier wiring as a once off investment, and no longer needing an expensive gadget with limited lifespan, IMO makes sense.

If you are set on limited amps and a DCDC charger anyway, then I agree lighter gauge wiring is fine.

But 20A would be my minimum target in any case.

 

[Hoologan]

You guys are right, charging from the tow vehicle alternator (via isolator and dedicated cable) is overkill for my needs.

Perhaps I’ll prioritize the solar option and simply plug into a battery tender when stored in the garage.

We’re talking weekend trips here so my #1 priority is being able to charge at home before a trip and have a battery that will last a few days. I’m not even a fan of organized campgrounds, so I can really do without shore power as well since I don’t plan on having any 110VAC loads.

I do not want a generator. I’d use my Coleman gas lantern for lighting before I use a genny.

Thanks for the input.

 

[john61ct]

Perhaps I’ll prioritize the solar option and simply plug into a battery tender when stored in the garage.

That will work well, if

you ensure you know the batt gets to 100% Full

and the batt's capacity is big enough.

Can even try it without the solar to start!

 

[luthj]

Your needs are small enough, that a 100W poly solar panel would likely do the trick. Home depot has a good deal on this 100W poly panel. Its not as compact as a mono panel, but shipping is free to the store.

https://www.homedepot.com/p/Grape-S...JtGzMfnz80MMLFr7WphoCOxkQAvD_BwE&gclsrc=aw.ds

 

[dreadlocks]

get your self a nice onboard charger, not a trickle charger and just fully charge it at home for weekend outings.. that may be enough if your not running a fridge.. and if you need it you can put solar on later, try to mount it so it provides a charge while driving while being able to chase sun at camp, then you can likely stay out indefinitely as long as you get enough sunlight or drive it around in the day once or twice a week.. onboard charger is going to be your main charge source, and it can come in handy even if you dont camp at sites w/power.. frequently I'd spend a day w/some family on a trip and run an extension cord to top off battery, then do laundry and take showers before hitting the road again.

consider a low voltage disconnect so it cuts off loads when battery gets too low, then you can just let it do its thing without checking on the battery all weekend.. if you find your self triggering it too much then add a solar panel or two

 

[Hoologan]

@dreadlocks any recommendation on an onboard charger? This is pretty much exactly what I’m looking for now that I’ve decided that charging from the vehicle isn’t worth the effort.

Thanks