Quote Originally Posted by carlschmid2002 View Post
Thanks Warbs that was very informative. I have recently purchased a Power Top from Bain tech power products and I am now looking for a suitable solar supply. This is for car/ trailer.
I've never seen on in the flesh, but it looks like an easy way to get a turn-key solution. I did notice that the manual on Baintech's website says it has a voltage warning at 11V - it varies a bit with the design of battery, but normally with a gel battery 11V would be regarded as fairly well completely flat! It might be worth asking if this is an error in the manual, or if you can adjust it, because having a warning a couple of minutes before the lights go out, and well after the battery has got to a longevity reducing state, seems rather futile!

If you're going to locate this unit (or any other battery) in your trailer, and want to charge it from the vehicle, you'll need to do some thinking. It's a long way from the alternator to the trailer, so voltage drop will come in to play, if the alternator is producing 14.7Volts that's great, but by the time it reaches the trailer that might have dropped to a lower voltage that won't fully charge your battery! So you need thick cables, and ideally a DC-DC charger in the trailer, which will take whatever voltage it is fed and "boost" it up to the correct voltage to fully charge the battery.

On my Prado there is another issue, being that Toyota (for fuel economy reasons) chose to limit the output of the alternator after the engine has been running for long enough to recharge the standard battery. That's great, but my setup has dual batteries in the Prado, plus batteries in the trailer.......

So I have a Redarc DC-DC charger in the Prado, which charges the second battery in the engine bay. It takes power from the alternator when the engine is running and boosts it to the correct voltage, no matter what the Prado's management system decides to do, but will also allow connection of solar panels when the vehicle is parked. I then have a basic (also Redarc) automatic solenoid ("dual battery") switch which, when the engine is running, supplies power via a heavy cable to an Anderson socket on the tow-bar. This connects to another Redarc charger in the trailer, which voltage boosts and charges the trailer batteries. When the engine is not running, the solenoid prevents the trailer from flattening the car battery without having to disconnect it, and the trailer's Redarc also allows connection of the solar panels in the same way as the car mounted unit if the trailer is unhitched. There is also a small solar panel on the trailer tool box, which trickle charges the trailer battery when nothing else is happening.

That all sounds complicated, but it means I have a fully automatic system that charges everything to 100% (not limited to 90% because of voltage drop, or 70% because of Toyota's management system!). It means that when travelling everything is charged by the vehicle, with no user input
(other than connecting the Anderson plug when hooking up), and when parked both the vehicle and the trailer can be charged by solar, and there's no risk of the trailer or fridge etc. draining the car battery.

The Redarc chargers I highly recommend. Mine have been all over Australia and never given me an issue!