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Old 05-06-2015, 09:00 AM   #1
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isolator/solar question

Sorry if this has been discussed, here's my issue. I have the blue (big heat sync) isolator that SMB installed in 1995. It works fine, I think. It charges house batteries when van is running. It does NOT do the opposite, like my previous 'smart isolator' I added to my homebuilt van did. Should it charge both ways? In other words, when I'm plugged in to power, my AC and DC circuits all run and the house batteries charge, but the van battery does not. I drive my van often enough for this not really to be a concern, but my goal now that I have solar is for the solar to also charge the van battery, which it does not, because it's wired right to the SMB fuse block/distribution, which only charges the house batteries. My alarm system and chargers drag my van battery down (from 12.8 or more to 12.3) in about 3-4 days. I have never let it get lower.

If this is normal for the SMB isolator, can I run a wire from the solar to my van battery, perhaps switched, to connect the solar to the front battery only when needed?

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Old 05-06-2015, 09:09 AM   #2
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Re: isolator/solar question

A isolator will not charge both ways. This is normal as it is how it is designed. It uses diodes to make sure the current can only flow one direction. Yes, you could probably wire around it, but there could be other unintended consequences of that. I believe the best thing would be to replace the isolator with a separator. It would end up being the cleanest solution.

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Old 05-06-2015, 10:52 AM   #3
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Re: isolator/solar question

Thanks Greg. At least I now know its operating properly.
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Old 05-06-2015, 11:09 AM   #4
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Re: isolator/solar question

On the other hand, there could be a reason to prefer a uni-directional one (although I'm not saying I wouldn't upgrade to a modern one). If you don't have any parasitic loads to speak of (on the start battery), and/or you drive reasonably often, and you have your solar charge controller set up for the parameters of your house bank (say you have an AGM house bank, but a flooded cell start battery), then maybe it's nice to keep the solar doing its thing with the house bank and not "interfering" with the start battery (different charge parameters/water might dissipate faster/etc.).

Not saying that's the best way, but just that I don't know that bi-directional is "automatically" the best way to go for all vans/situations (?). I'm setting my solar charging system up to be only on the house bank in the default position (with an option to combine so that it reaches the start battery if desired, but that won't be the norm).
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Old 05-06-2015, 02:02 PM   #5
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Re: isolator/solar question

Separators come uni-directional or bi-directional....and there seems to be +'s and -'s to each type with and without solar and/or shore power charger.
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Old 05-06-2015, 02:37 PM   #6
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Re: isolator/solar question

I just feel people kill their batteries from either over or under charging them. Depending on the type batteries, over charging seems less of an issue, while letting the batteries sit w/o a charge tallies up more as the bigger battery killer, at least it seems that way with AGM's.
I've always thought a constant higher amp solar charging might be harder on maintenance free or standard wet cell starting type batteries especially when the solar is putting out as much as it can to replenish what was taken from the house battery over the night. It takes a while to put the solar controller into a float mode and while the house battery system is accepting a charge, the starting batteries are being over charged. It would be nice to have a smaller solar panel take care of the starting battery system and let the larger array deal with the house battery. The only issue I see is w/o a separator is you'd have to manually close a switch to push the charge through from the alternator to the house. That's too much to go wrong IMO. Also there's the real estate needed on a small vehicle. A lot of big RV's have split solar systems for that reason... they have the room for a lot of panels and can size each array to the battery system. Starting batteries need a very little amount of charge to keep them topped off. I would never bank two solar controller together from different arrays and there is a point to keep it as simple as you can. I just changed my starting batteries to AGM and use the 2-way separator. Seems to work for me. Easy to troubleshoot, I have full control and can jump start the vehicle just in case the starting batteries go flat.
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Old 05-06-2015, 05:23 PM   #7
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Re: isolator/solar question

Thanks all. I think I'll just leave my setup alone for now. It's getting to be summer and the van won't even sit as much as it does now, which isn't much. I just hate to not take advantage of solar with it putting out juice, but some good points made and I don't want to overcomplicate things.
I will, however, go with a bidirectional isolator/separator/whatever when my original one craps out.

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Old 05-06-2015, 09:32 PM   #8
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Re: isolator/solar question

Add some solar if you can. So what if it doesn't charge the starting batteries. That really only matters if you let the vehicle sit Eric. SMB at one time had a conversion kit to go from the isolator to a separator. The main issue is the buss size where it makes it safe to jump start the vehicle. Dead starting batteries combined with the amps required to turn an alternator is substantial but not as much as a diesel engine. A little understanding goes a long way. If your starting batteries are too low to start the engine, forcing the separator to combine and letting the amperage flow from the solar plus the reserves in the house system will usually get you back on the road provided you leave it connected for enough time and there isn't a short (or draw) causing the original problem. Just like using jumper cables, sometimes it takes a while for the batteries to "equal out" before you can turn it over.

Even with a isolator you'll still have the solar advantages it provides to the house system. That's a lot on its own.
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Old 05-06-2015, 09:53 PM   #9
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Re: isolator/solar question

I can't add more solar, I'm out of space! My 100 watt panel does ok but my roof box takes up the rest of my roof. I would love to add another 100 watts if I can figure out where to put it.
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Old 05-06-2015, 09:56 PM   #10
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Re: isolator/solar question

Quote:
Originally Posted by 86Scotty
I can't add more solar, I'm out of space! My 100 watt panel does ok but my roof box takes up the rest of my roof. I would love to add another 100 watts if I can figure out where to put it.
A hundred is better than nothing. Real Estate matters. Many are fine with a single 135 watt panel. I got 270 and am happy. There is always adding a portable. I have a 65 watt portable panel I stow under my lower bed...only used it a couple times but when you need it...
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