Questions about trailer solar systems and charging off the tow vehicle, and shore power

[Pastryslayer]

Bear with me. I'm good with suspensions and plumbing but electrical stuff still feels like voodoo to me.

I have, sort of, a Borderlands trailer. I say sort of because it was their prototype and is quite a bit rougher than their end product. Quite a bit cheaper too, which is how it came to be mine. It has a pretty nice solar panel on the roof and two 6v 265 amp AGM deep cycle batteries on board, with a controller, master breaker, and a 110 inverter. There is also a shore power hookup and external 110 plug ins.

Short version is this: I want to run power from the tow vehicle to charge the trailer batteries while connected/driving. It didn't come that way, but I know which wire in the 7-pin is the hot one. The advise I got was to simply run a wire from the 7 pin directly to the positive post on the first battery in the system. Does that sound right? Is that how tow-vehicle charging usually works?

Both batteries are dead right now. I thought having them on shore power would keep them topped up, but a friend of mine with more trailer experience said that shore power is generally more of a bypass for the batteries than a connected charging system. Which would explain why they were dead, since it's been inside all winter with no sun on the solar panel. When it had sun last summer, it didn't seem to charge much, but I also wonder if I forgot to turn on the breaker. So my second question is, in a solar setup does the breaker/controller need to be on to let the solar panels charge the system, or will the panels charge the batteries even if everything is off?

Quite likely the 5+ year old (abused by the previous owner) batteries are dead. I'm having them tested and charged at Interstate today, and have designated replacements if needed. Just trying to figure this thing out with no manual or working knowledge. Wanting to get it all done in one shot since accessing the batteries requires tearing the front wall off the trailer. Which requires removing the tongue box. ?

Thanks for any help in advance!

Pastry

 

[carbon60]

Yeah, you need a larger conductor from the tow vehicle to the trailer, if you want to have meaningful charging. I am working on this, myself. Aussies often have a dedicated Anderson SB50 connector for this purpose.

The cheap/fast/acceptable approach is to simply use jumper cables from the tow vehicle to the trailer when you really need to cram more angry pixies into the latter. Otherwise, rely on the solar.

 

[Pastryslayer]

Yeah, I didn't really expect to full charge the batteries off the 7 pin, just maybe enough to top it up on long drives. Would it hurt anything? Or just be ineffective? It's about $2.00 in parts i already have.

I hadn't considered the anderson connector. I have one for my winch and about 23ft of cable for it...I suppose I could put another anderson connector directly on the trailer batteries and run the cable into the battery compartment and just use the running car as a charger when needed...any reason that wouldn't work?

 

[Pastryslayer]

Sounds like I need a float charger for winter storage.

 

[john61ct]

The problem is, the rate of current amps pulled by a lead bank varies enormously depending on how depleted it is.

At very high SoC might only be 5-10A, but when at 50% might draw 60A or even more depending on the battery capacity and chemistry.

So to be safe, the wire gauge and connectors should be sized for the maximum current that circuit will see.

A DCDC charger at the bank will put a cap, limiting the amps.

 

[Pastryslayer]

I don't have the option to store it outdoors, unfortunately.

ETA: I'm pretty confident in the solar panel while travelling (Still wondering if the breaker has to be on for it to charge), but I'll for sure need something to keep it up in the winter.

 

[john61ct]

Avoid the cheap garage style "trickle charger".

Get a proper quality intelligent charger that you can use when actually deep cycling and stay at a powered campsite.

Every 3-5 weeks give them an overnight charge.

You could leave them on Float, but that's a lot of trust. . .

 

[dreadlocks]

a good onboard charger goes a long way for extending life expectancy of batteries, both at home and on the road when AC power presents its self.. I like the timer idea for long term storage than a permanent float.. its real easy to forget about something you dont look at all winter.

other things to really help extend your battery life is a Low Voltage Disconnect that drops all loads before you over-discharge the batteries, and a Battery Monitor that calculates a somewhat accurate State of Charge so you can predict your runtimes when variables change and monitor battery health.

Most rec trailers are wired so solar is always hot and would just have a master battery disconnect switch on the battery, but that dont mean there is not a disconnect switch on em somewhere.. should be pretty easy to tell if your solar is working, at LEAST get you a voltmeter if nothing else.

 

[john61ct]

If I had a bank worth thousands not sure I'd trust a timer more than a charger costing hundreds.

 

[dreadlocks]

if this guy spends thousands on two 6v batteries he's doing it wrong.. though he should just get FLA GC batteries instead of AGM's..

I wasent implying a cheap timer avoids need to get a good charger, but I've got some mechanical timers that are extremely reliable.

 

[dwh]

(Still wondering if the breaker has to be on for it to charge)

Still wondering, "what breaker"?

You said something about a breaker...but not what circuit the breaker is in. Solar input to the charge controller? Battery output from the charge controller? Inverter feed from battery? Inverter output to 120v plugs?

Incoming main from Hoover Dam to your workshop on the back 40?

Is the breaker labeled by any chance?

 

[dwh]

Solar charge controllers all recommend connecting the battery first, then the solar. That's because the charge controller needs power to run its internal electronics, and it gets that power from the battery (so it keeps running even if the sun is down).

If the breaker kills the solar input to the charge controller, the charge controller will still be turned on and will still be a parasitic drain on the battery.

 

[Pastryslayer]

Still wondering, "what breaker"?

You said something about a breaker...but not what circuit the breaker is in. Solar input to the charge controller? Battery output from the charge controller? Inverter feed from battery? Inverter output to 120v plugs?

Incoming main from Hoover Dam to your workshop on the back 40?

Is the breaker labeled by any chance?

All excellent questions that further highlight my ignorance in this area. I'm thinking some photos are in order.

Basically what I was calling a breaker is a big switch in the control area of the trailer labelled "On" and "Off." None of the other switches work when it's off (water, overhead lights, plug ins, etc). There is what I thought was an inverter that also has some sort of voltmeter built into it. It also goes off when the main switch is thrown (and if I don't switch it off first, it makes a horrible squealing noise). That's the only monitoring device in the whole setup.

I appreciate all the assistance and will get some photos up to help illustrate, clearly I don't have the knowledge to communicate the issues effectively. I swear I'm not usually this useless.

Also, the battery folks just called. One battery is shot and the other only partially charged, so they're both getting replaced Saturday. We also discussed a charger and he assured me they have smart chargers particular to my type of battery available. (I've had good luck with these guys in the past, good customer service).

 

[Pastryslayer]

if this guy spends thousands on two 6v batteries he's doing it wrong.. though he should just get FLA GC batteries instead of AGM's..

I wasent implying a cheap timer avoids need to get a good charger, but I've got some mechanical timers that are extremely reliable.

If that stands for Flooded Lead Acid Golf Cart battery, why is that better than an AGM?

(My quote for the two AGMs they have for me was $310 apiece, they'll take mine for the core and waive the charging and test fees).

 

[dreadlocks]

you can get a FLA for $100 each from Sams Club or Costco, they are more robust, take more abuse and are cheap and easy to replace when the time comes.. AGM's provide practically zero benefit for you other than emptying your savings account every time you need a new bank.. AGM's are finicky, easily damaged, harder to recover, and for recreational trailer loads provide nothing extra of value what so ever... maybe if you were full time off the grid with very high loads and reliable charge sources you could take advantage of its gains, but even then its almost never worth the premium because you need to buy top grade batteries from one of the like 3 good AGM manufacturers that cost many times more than "cheap" AGM's

AGM's are marketing snake-oil, they wont last any longer than FLA, in reality its likely less.. so you can buy 3x sets of FLA Golf Cart Batteries for the same cost sunk as 1 set of AGM's and they will perform every bit as well.