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Old 10-27-2012, 10:54 AM   #1
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Using solar controller without PV panels

I'm not that familiar with solar controllers, which I guess are more or less voltage regulators, usually with smart charging functions. So they take say 12-17 V input and regulate it so that it doesn't get above say 15 V, and shuts off below say 10.5, and doesn't run in reverse.

Could one attach another 12 volt source, i.e. a vehicle's, to a solar regulator? I see that solar regulators are typically limited by amperage. Does this mean they limit the amperage, or that you, the user, has to attach something to them that is limited in amperage? So that if I connected my vehicles 12 V output to a solar controller it would blow because that vehicle is obviously capable of generating many more amps. The voltage regulators I've seen on boats that attach directly to alternators don't have such limitations. Most 12 V small bank battery chargers don't pull that many amps, so I'm wondering why I couldn't use a solar controller for charging.

EDIT: Obviously there are other power loads besides the battery charger; the refridgerator will pull a few amps for example. Don't know how controllers deal with this, but ideally you could run a lot of amps in the house from the van charging system so that you do more than just charge batteries. Usually there's enough power to do both.

thanks,
Rob
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Old 10-27-2012, 09:24 PM   #2
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Re: Using solar controller without PV panels

Interesting question but I'm fairly sure if you ran the amount amperage through a solar controller that the alternator puts out it would have to de designed to handle that amount. Most RV controllers are designed for lighter loads (15-30A). Is that what you're trying to do...regulate the alternator charge to the house batteries?
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Old 10-28-2012, 11:26 AM   #3
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Re: Using solar controller without PV panels

I'm not sure what you mean by "RV controller," but the output of the alternator is already regulated by the engine system. That passes through the isolator; the regulator makes sure the voltage doesn't get too high and that both batteries charge.

I'm not what exact isolator I have, but it probably passes through a lot of amps.

Lots of people essentially run a solar charging setup in parallel to the alternator; going down the road the alternator is providing power to the battery and so is the PV system. I'm not sure how the two systems deal with sensing the battery power in that situation, since that is used to adjust the voltage in a three or four stage charger. And some of the power from both systems is used for things like the refridgerator, lights, charging laptops, whatever.

My question is essentially whether one could run BOTH the alternator/isolator output AND the solar through ONE controller. The van system would not, in that case, even know the house battery was there. It would be just like any other 12 volt accessory. And to the solar controller it would be like a 13.7 volt-ish panel. But I'm not sure what amps it would pull, because unlike a panel the alternator output go way high in amps.
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Old 10-28-2012, 12:31 PM   #4
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Re: Using solar controller without PV panels

Basically the answer in NO...

The solar controller (and what daveb called RV Controller) is in fact a voltage regulator but sine your vans alternator puts out very high amps it would not be able to handle the vehicle amp load as an input. The 10, 15 or 30 amp number for controllers is the maximum amperage input that they can take. Depending on what year your van is your charging system output is from 80 amps to over 200 amps thus much more that the contoller can handle. These controllers many of which are Pulse Width Modulated have very small light gauge circuit boards and can not handle high amps very well.

I am not sure just why you woukd want to usde a controller in the manor you described. Your van has abuild in regulator and will not over charge anything unless there is something wrong with it. As amatter of fact it is a common misconception that a vehicles alternator will really fully recharge the batteries. The truth is that an alternator is only designed to keep a fully charged battery full not completely rechage a low battery. Thats the beauty of solar, it really does fully charge the battery/batteries just like a 110 volt charger does. When using both solar and the vans charging system the solar controller basically lets the altenator do its job normally and does not really add much to thecharging while driving. One has to remember that these controllers while used for RVs are really designed to be stand alone solar regulators but just happen to work fine when used in conjunction with an alternator.

One last thing a 12volt battery should never be over 14.7 volts and really should be charged before it gets below 12volts if you want it to last. Some solar controllers do allow slightly higher voltage to top up the battery but it is in very low limed doses and with very low amps.


Hope that helps...
...Jamie
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Old 10-28-2012, 12:42 PM   #5
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Re: Using solar controller without PV panels

Quote:
Originally Posted by rob_gendreau
I'm not sure what you mean by "RV controller," but the output of the alternator is already regulated by the engine system. That passes through the isolator; the regulator makes sure the voltage doesn't get too high and that both batteries charge.

I'm not what exact isolator I have, but it probably passes through a lot of amps.

Lots of people essentially run a solar charging setup in parallel to the alternator; going down the road the alternator is providing power to the battery and so is the PV system. I'm not sure how the two systems deal with sensing the battery power in that situation, since that is used to adjust the voltage in a three or four stage charger. And some of the power from both systems is used for things like the refridgerator, lights, charging laptops, whatever.

My question is essentially whether one could run BOTH the alternator/isolator output AND the solar through ONE controller. The van system would not, in that case, even know the house battery was there. It would be just like any other 12 volt accessory. And to the solar controller it would be like a 13.7 volt-ish panel. But I'm not sure what amps it would pull, because unlike a panel the alternator output go way high in amps.

No, it would be a bad idea to try to tie alternator and solar outputs together and run the output through a solar-type controller. They have very different charging characteristics, and a single controller won't manage them properly, not to mention you could well have electrical problems with outputs in common, either in the panels or alternator.

If you have permanently connected solar panels, you need a solar regulator.

As to whether you might ALSO want a "charge controller", "alternator controller", etc., it depends on how you use your system, the type of batteries you have, and what kind of regulator is in the van for the engine battery charging. Used to be, before the advent of AGM batteries, the answer was almost always YES, you do need an alternator controller for the house batteries. That's because the automotive regulators used to be very inefficient charging deep cycle batteries.

Now, it's more complex -- there isn't one right answer. Many/most RVs do have them, but the quality of the stock installs varies a lot. If you ONLY have one type of battery (AGM, gel cell, wet cell) AND you do a lot of driving, you may not need one. With mixed battery types, or wanting to charge the house batteries quickly on high idle, then you probably do want a separate controller for the house batteries.

It all has to do with charging voltages, how the regulator(s) are designed, how the different types of battery construction absorb a charge, even what kind of battery isolator is installed (splitting diodes have a built-in voltage drop which complicates deep cycle charging). And how much performance you want out of your house battery set. If you never tax them much, then the van can probably handle them. But to get max performance, you want to be able to "bulk charge" them without running the engine for hours. That takes either a smart controller or a shore-power charger.
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Old 10-28-2012, 01:56 PM   #6
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Re: Using solar controller without PV panels

Rob, I still don't know what your goal is. If it is to transform the alternator charge to a smart charge there are ways to do it but those little RV solar controllers won't cut it as what was posted.
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Old 10-28-2012, 02:12 PM   #7
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Re: Using solar controller without PV panels

Yes, that's why I asked.

I had been corresponding with Mike, who installed an inverter. Essentially you use your van power to run the inverter which inputs power just like your shore power, which means it goes through a smart charger (in my and many others' vans; some don't have this). He used a 750 inverter, and a delayed switch so that the power to the house comes on after the van gets going. You lose I would guess about 15% in the inefficiency of the transfer and change to AC, but you do get a better charge into your battery than the van alternator could do alone. And you also have some AC left over to charge your laptop or whatever.

You said the they have different charging characteristics. An AGM uses a particular charging profile that doesn't vary depending on the source, does it? I seem to recall that you could get a faster charge with more amps, and a solar source might be more limited than shore power for that obviously. For example, when charging with a generator I can put my shorepower charger in "boost" mode manually. You can hear the charger grab more amps from the generator and it revs up; ditto when it tries to desulfate the batteries. Are you saying there's no solar controllers that act similarly? (And my recent research seems to indicate ones capable of generating more amperage seem to cost a lot.)

thanks for the help,
Rob
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Old 10-28-2012, 02:41 PM   #8
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Re: Using solar controller without PV panels

Quote:
Originally Posted by rob_gendreau
Yes, that's why I asked.

I had been corresponding with Mike, who installed an inverter. Essentially you use your van power to run the inverter which inputs power just like your shore power, which means it goes through a smart charger (in my and many others' vans; some don't have this). He used a 750 inverter, and a delayed switch so that the power to the house comes on after the van gets going. You lose I would guess about 15% in the inefficiency of the transfer and change to AC, but you do get a better charge into your battery than the van alternator could do alone. And you also have some AC left over to charge your laptop or whatever.

You said the they have different charging characteristics. An AGM uses a particular charging profile that doesn't vary depending on the source, does it? I seem to recall that you could get a faster charge with more amps, and a solar source might be more limited than shore power for that obviously. For example, when charging with a generator I can put my shorepower charger in "boost" mode manually. You can hear the charger grab more amps from the generator and it revs up; ditto when it tries to desulfate the batteries. Are you saying there's no solar controllers that act similarly? (And my recent research seems to indicate ones capable of generating more amperage seem to cost a lot.)

thanks for the help,
Rob

The difference between solar and alternator controllers is that with solar, they have no control over what the panel output is, the controller can only regulate the battery side. However, an alternator controller (which is really a smart external regulator, btw) DOES have control over how much power the alternator produces, in that it acts as a regulator and can boost / cut alternator output as needed up to the max any particular alternator can produce at a given RPM. Thus, it has control both over input and output power.

This is why you can use an alternator controller to bulk charge your deep-cycle batteries without the engine running at high rpms -- it varies the alternator output as necessary during the charge cycle.

They are completely different designs. One won't substitute for the other.
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Old 10-28-2012, 03:34 PM   #9
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Re: Using solar controller without PV panels

Rob, I know a couple of people who have set up a system like that. It would be a way to "peak" the batteries. It is possible to let the alternator provide the bulk charge and have a small say 5 amp smart charger apply the final top off charge by using an inverter to power the smart charger while driving. You really wouldn't need a heavy amp smart charger unless you don't have an on board converter/inverter smart charger that takes care of the day to day shore charging. Myself I want things automatic. If I had to turn on or off any device to provide the only charge going to the house system, I would forget and I'd end up with dead batteries on a regular basis.
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Old 10-28-2012, 10:08 PM   #10
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Re: Using solar controller without PV panels

Chromisdesigns, thanks. That's obviously what's happening with my generator (and probably why it has problems when I try to run it in economy mode while charging, since it's getting mixed messages).

I think I'll just go with a separate solar controller. It's hard to control how long you are driving anyway, so you may not get a complete charge due to time. With boats it was easier since you're running at a constant rate for much longer.

Rob
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