Hooking a solar battery

I have 4 100w solar panels & 2 1000w batteries that I would like to hook one of them into my trailer only when I use it. Is there a way I can hook it up to my trailer without using the regular power cord? I don't want to use any solar power to go to my 12v lead battery but I don't want to use any power from it either. All lights in my trailer are LEDs, but still on the convertor circuit so 110v or 12v still work. . I guess I can plug into the solar battery and disconnect my main battery or put a switch on it as long as I don't use the AC. Any suggestions? My solar batteries(2) have 3 110 outlets, 2 USBs, one USBC, and a 12v outlet on them. I guess my biggest question is would the convertor pull or use power even when nothing is on or running?

Don - I'm having a difficult time understanding what you are trying to accomplish - blame it on my advanced age (83) and fading brain cells. From your description, it sounds to me like you may have a "solar generator"? (This device combines solar collectors, a controller, a storage battery, and an inverter.)

If you connect this to your trailer's converter, with the shore power cord, it WILL draw power from the generator, even if nothing is on, because the converter has its own power needs any time it is "powered", but that draw is minimal. Also, the converter is hotwired to charge the trailer's battery, so that would be getting charging power too, if the converter is powered.

I suppose you could rewire the trailer's circuitry to bypass the converter and use the generator to supply direct power to the AC and DC circuits in the trailer, but that seems a complicated mess.

- Jack

I have a solar battery that I use. But to run the lights in the trailer with it, how would I hook it up without it trying to charge my main lead battery? I don't have a controller, just a battery with 3 outlets and USB and USB-C on it.

Don, if you have a "solar battery" there IS a controller between it and the solar panels that charge it. The controller is needed to regulate the charging voltage and current to prevent battery damage.

If the battery is connected to the trailer through its converter, you WILL be charging the trailer's lead-acid battery. From your description, I think your solar generator does not have its own "converter", which transforms 12VDC to 120AC, and your 12VDC output from the solar generator is limited to very low Wattage USB outlets. These may not have sufficient output to power your trailer's 12VDC appliances and lights. They may not have sufficient output to power just the lights alone.

I think the simplest way to do what you want, would be to connect the solar generator to the trailer via the shore power cord and insert a switch between the trailer's converter and the trailer's battery to disconnect it. I THINK your trailer's converter will still supply the 12VDC trailer circuits that way (without a trailer battery).

The other way would be to modify your solar generator to supply a higher Amperage 12VDC output and then modify your trailer's wiring so that you could connect the 120VAC outpur of the solar generator directly to the AC circuits in the trailer and do the same with the 12VDC wiring in the trailer so you'd connect that new 12VDC output from the solar generator directly, both connections bypassing the trailer's converter. This sounds to me like a kluge, and I wouldn't do it.

- Jack

I suspect you may have discovered that the 1000 Watt solar generator is not really up to the task of supplying a lot of power over a prolonged period. The battery in that thing is a 12VDC battery and to supply 1000 Watts, it has to deliver 83.3 Amps. Typical 12V lead-acid batteries have a capacity of around 55 Amp-Hours. So it likely will go flat after about 30 minutes if there's a heavy drain.

Then, you have to recharge that battery, using 400 Watts of solar power. The 400 Watts is a "no-load" rating and under load, you can expect to get about 200 Watts on a good day, due to the panel's inefficiencies. So it's going to take 5+ hours to fully recharge that battery in the sun.

I don't think solar generators live up to the "hype".

- Jack

The Solar Battery has the controller built in as it has 3 110v outlets. I will have to play with it when it warms up and look at it. I might have to put a switch on the lead battery but probably will need the converter as the lights are 12 volts and the plugs are 110. But all I want to use is the pump and the lights. I don't care about the 110.

I'm well on the way to 83 too so having some trouble understanding what the goal is here but it seems that you want to use one solar battery to exclusively provide your trailer DC power needs when you are at rest with it. You have no interest in 110 volts but it appears you may want to charge the solar battery via AC conversion at times when solar isn't sufficient but you don't want to loose battery power to charging your trailer 12V battery. The trailer battery probably supplies electric brakes in addition to trailer driving lights and is currently connected to the converter. Hopefully this is an accurate problem statement.

I have a trailer with the dreaded Elixer converter which right on schedule burned up fortunately without burning anything else. At the time of failure I had a good solar converter installed that has worked well for years. Rather than doing a one to one Elixer replacement with something like WFCO, I decided to build a custom replacement with a standalone converter. The Elixer box was repurposed for just fuses/breakers and switches to manage a main trailer converter connectable to shore power, the solar converter and a kill switch for the trailer circuits to the battery without interrupting driving lights or brakes. This gives huge flexibility in power options. I even added additional direct 8 gauge wires for the solar converter to the battery (to ensure voltage accuracy in managing charging) which could be diverted to something like you solar battery instead of to the trailer battery.

When shore power is connected, the DC converter output either complements or replaces solar when it is turned on. When the trailer converter is turned off, shore power only supplies AC circuits. A fully featured battery monitor allows me to understand the current battery state and net in or out voltage / amperage. The wiring for all this is incredibly simple so not at all hard to manage / troubleshoot (have never had any trouble - touch wood). If I were adding a solar battery to my system, I would just add another switchable circuit to my solar converter. Plug the solar battery into that, an presto - DC power to the trailer and with the inverter and kill switch off, would have DC internal power. The brakes and the trailer lights would still operate without having to remember to turn any switches before driving away.

Bill - Welcome to the forum. Just one small point: The trailer exterior lights (running/braking/turn signals) are all powered by the tow vehicle. There's no connection between these and the trailer's DC power supply. I'm pretty sure the electric trailer brakes get their power from the tow vehicle too, since their stopping force is proportional to how heavy you apply the brakes. However, if you disconnect from the trailer while towing, then the safety brake feature gets its power from the trailer battery.

- Jack

Jack - thanks for pointing that out - I mis-spoke about the trailer running lights which of course are powered by the vehicle along with brake lights and turn signals. However, I was albeit clumsily referring to break-away braking from the battery though, as that is essential. I should have specifically mentioned that. For an Elixer converter implementation at least, but probably many of the others, all these wires are emmeshed in a bundle and if you are not careful with rewiring, it is easy to disrupt the breakaway brake circuit with something like a DC kill switch. We should all be testing that brake circuit regularly (especially on cargo / utility trailers where you might not notice that the onboard battery is dead because the vehicle battery does nearly everything else) but I confess that I don't do that before every trip - but definitely do it after a re-wiring escapade!

Bill

Hi again, Bill. I wasn't trying to be a "know it all", but we DO have new trailer owners who don't have a clue about the trailer wiring and I was trying to keep them from getting confused. Those are excellent points you point out about the breakaway brake system in the trailer. I have to admit I don't check it like I should either.

And yes, it's very easy to miswire something when you are adding things or upgrading systems in the trailer. I did it when I installed the PD Dynamics converter in my trailer and I included that error, and the correction in my thread on the installation of that converter. I also made a minor mistake in the wiring of the DC-DC converter when I changed from lead-acid batteries to LiFePO4 batteries.

Complete testing of all circuits is mandatory! Things happen, even if you don't do DIY work on the trailer. I lost the left turn signal and brake light on my trailer due to a mouse chewing through a wire and didn't realize that had happened until we were halfway through a trip.

- Jack

I finally figured out how to wire my solar battery to the trailer to operate the lights and pump. I put in a toggle switch at the fuse box. Up will connect it to the trailer battery and down will connect it to the solar battery. Was trying to attach photos but would not do it.

tcongdon said:

i finally figured out how to wire my solar battery to the trailer to operate the lights and pump. I put in a toggle switch at the fuse box. Up will connect it to the trailer battery and down will connect it to the solar battery. I was trying to attach photos but would not do it.

Click to expand...