Battery Isolator

[bdosborn]

Here's the Yandina Instructions using a Radio Shack DPDT switch, part number 275-1533.



APPENDIX
1. REMOTE CONTROL
The GREEN REMOTE wire is usually left
unconnected for automatic operation. It may be cut short if
desired.
It can be connected through a single pole, center off,
double throw switch for remote control. Switching it to
ground forces the Combiner 100 off, switching it to +12
forces it on. The response of the Combiner 100 to remote
operations is delayed by turn on and turn off timers.
When disconnected in the center position you are in
automatic. If you only need one function, a simple on/off
switch will do. The remote control input is purely voltage
sensing so a light gauge wire is sufficient.


Bruce

[absolutsnwbrdr]

Ooooooh OK. The DPDT is what was throwing me off. I thought you had wired it up some fancy way using a DPDT. But you're only using 1/2 of the DPDT switch contacts, which acts just like a SPDT. Ok gotcha.

[droid_ca]

ok I'm confused will any switch work or does it have to be that specific type thanks for all the help with this

[bdosborn]

Ooooooh OK. The DPDT is what was throwing me off. I thought you had wired it up some fancy way using a DPDT. But you're only using 1/2 of the DPDT switch contacts, which acts just like a SPDT. Ok gotcha.

Yeah SPDT with center off would work just fine but the last time I was at Radio Shack I couldn't find any so I had to use the DPDT.

Bruce

P.S. Yes, you could use a single switch but you'd only get manual off *or* manual on, not both.

[working on it]

I'm not meaning to muddy the waters here, but in my experience running dual batteries, with and without isolators/combiners, I've always found that if your two batteries are not of similar size and condition, then the weakest one will draw more power from the stronger. I'm sure an electrical wizard could figure out the right configuration of diodes to prevent that, but unless that ideal situation is set-up, then eventually the isolator will fail to maintain both batteries. I've had three isolators, and all three finally went sour on me, because of two things 1) I didn't use two fresh (twins) batteries once, and didn't equalize their draw-down time , twice. On my TTT, incomplete at this time, I'll keep the two batteries-TV and TTT- separate, charging the TV with the alternator while towing, and having a freshly charged deepcycle on board the TTT to be refreshed at camp sites with shore power/on board charger or on board generator/charger.

[droid_ca]

P.S. Yes, you could use a single switch but you'd only get manual off *or* manual on, not both.

Ok Im presuming that this was directed towards my question, what does this do if there is more then on /off does the second on have a different feature then the other and off is just that off. Cause my current setup I will be having extra batteries on my truck and possibly a solar panel, I still want to have it connected to my trailer but don't want to burn anything up, will this set up prevent that? I like the idea of everything working together but I don't like the idea of killing batteries.

[bdosborn]

I'm not meaning to muddy the waters here, but in my experience running dual batteries, with and without isolators/combiners, I've always found that if your two batteries are not of similar size and condition, then the weakest one will draw more power from the stronger.

That's what the combiner takes care of. When the car is running, the system voltage is around 14.4 V or so. The combiner closes and both batteries can be charged without discharging each other. Stop the car, the voltage falls to 12.7V or so and the combiner opens and separates the batteries. The cheap way to do the same thing is to unplug the trailer from the car whenever you stop and turn the car off.

Bruce

[bdosborn]

P.S. Yes, you could use a single switch but you'd only get manual off *or* manual on, not both.

Ok Im presuming that this was directed towards my question, what does this do if there is more then on /off does the second on have a different feature then the other and off is just that off. Cause my current setup I will be having extra batteries on my truck and possibly a solar panel, I still want to have it connected to my trailer but don't want to burn anything up, will this set up prevent that? I like the idea of everything working together but I don't like the idea of killing batteries.

I wouldn't worry about adding the switch to your setup. Just let the combiner do its thing in automatic mode and don't worry about it. Nothing will burn up and your batteries won't discharge each other. If you want more information about the combiner, click here. There's tons of info at the Yandina FAQ page.

Bruce

[droid_ca]

Thanks Bruce that link will be helpful

[absolutsnwbrdr]

FWIW, here's my latest wiring schematic, with the Yandina included. Bruce - as you can see from my schematic, I tied the green wire into the 12V+ of the RV battery (through the SPDT switch). Look correct?

[bdosborn]

The Yandina is bidirectional so I would put a fuse on the trailer battery side to go with the fuse on the start battery side. That trailer side wire is unprotected.

Bruce

[absolutsnwbrdr]

The Yandina is bidirectional so I would put a fuse on the trailer battery side to go with the fuse on the start battery side. That trailer side wire is unprotected.
Bruce

Good catch! Thanks!

[PcHistorian]

guys, check me on this. something seems too easy, but for a common charge point for two batteries, with a common load (LED lighting circuit I wanted an extra battery that couldn't get drained by any other system. But that would be saved for later and have the main battery power it, if the main battery had power.) Each battery could have its own separate load that is not shared by the other battery, too. And still have both systems share a common charge point.

So I want a systems isolator. I know Radio shack has 25 amp full wave bridge rectifiers. (bolt it to a heat-sink) Heck, I've salvaged some that must be at least 10 amps from old PC power supplies. I know car alternators put out 60 - 100 amps, commonly, so I'd have to get different diodes/rectifiers if I included the tow vehicle's primary battery and electrical system, but that is do-able, too. (I have a source for 100 amp alternator diodes, no problemo. 4 arranged accordingly... )

using a full wave bridge rectifier as a battery charge & isolator.
should charge the heaviest to the lower voltage (charged) of the two batteries, while drawing power from the higher voltage (charged) of the two batteries.

[absolutsnwbrdr]

Been about 10 years since I've seen one of those diagrams, so I had to look at it for a few minutes but that looks like it would work. Heck, that might be part of the simple internal circuitry of the device I got.

Btw thanks for reminding me that I havent installed my battery isolator yet.

[bdosborn]

It would work fine if the batteries are right next to each other and there are commercial versions of that approach that probably cost less than it would to build it yourself. However, they don't work very well in in a teardrop because of the diode voltage drop. There's a 0.7 to 1.1 V drop across the diode, depending on the type used. That drop combined with the voltage drop on the wire back to the trailer battery often leaves you with an end voltage too low to charge the battery.

Bruce