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Originally posted by Lee:

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This prevents dual charging from the alternator circuit and the IntelliPower charger/converter.

Is that a bad thing?........I just did the Intelipower/Smart Wizard install and routinely run the genset for the A/C while on the road, and I sure wouldn't want to hurt the new house battery if this is an issue......

There are two considerations here:

1. Whether or not any charging device can be damaged by parallel charging devices can only be answered by the company making it. I ruined a Sears charger by using it in parallel with another charger. The Sears charger was selectable for type of battery and was automatic. Sort of a "Smart" charger. The second charger was a Stone-Age "Dumb" but powerful charger that has been in the family since the demise of the Tungar bulb. I suspect something on the circuit board was damaged by a spike or transient. It could have been caused by connection one or the other charger or just by a surge when the big one was plugged in. I don't remember any more what the sequence was.

2. I do not like batteries being charged when paralleled. The only time it is OK in my book is when the banks are identical type, age, condition and state of discharge. If these conditions are not met, charging is less than optimum. As an example, I found that I had partially run down my starting battery by extensive radio and CD use. Since I have solar charging, the house batteries were fully charged. It was simple to connect the starting battery in parallel with the coach battery bank. I measured the current going into the starting battery both when it was in parallel with the full batteries, and when it was the sole recipient of the solar charging. My notes are elsewhere, but the starting battery got a lot more power solo than in parallel. My on the road observations were more dramatic than these measurements, but every situation is different, as the internal resistance of a battery is always different. I remember driving from Mammoth to Bakersfield and still not getting a full charge with an isolator system.

I once found myself with a mismatched pair of coach batteries for economic reasons. I set them up with switches that allowed me to charge and use them solo as well as parallel. Parallel was never as good.

I do not like isolators, as they do not ever allow full charging due to the built-in silicone diode voltage drop of around .7 volts. A Schottky diode isolator will address that issue, but you still have the parallel charging. If anyone really wants to do the parallel charging thing while driving, a standard constant duty RV relay can be wired up quite simply to obviate the isolator voltage drop. Instructions on request. It is much cheaper than the Schottky set up, and accomplishes automatic charging when the engine is running and incorporates the emergency start/parallel in the same solenoid control circuit.

Before I had solar, I did indeed use my alternator to charge the house batteries as I drove. I used a Perko make before break marine battery switch to select which bank would be charged by the alternator. That way, the alternator would be reading and responding to only one battery.

I know the Delco alternators drop their output when hot, by design. They are not designed to do anything more than replace what you took from the battery when you started, then power normal accessories, so their voltage drops when warmer. To the mid 13s. Coach batteries like 14.2 or 14.3 volts during the bulk cycle. Anything less than that can shorten battery life.

None of this means that alternator charging of batteries connected in parallel, with or without an isolator, is bad. Obviously, thousands of RVs do this. But it is not the best way. The short battery life experienced by so many RVers speaks for itself.

Oh yeah, I am not a total hater of batts being charged when connected in parallal. Once my coach and start batteries are fully charged, I parallel them for the float when the RV sits.

Ah Heck, this is getting to be a soapbox. And I haven't even started on mineral oil or EDTA......But I am on year 7 of my coach batteries, all boondocking, so some of this ranting must be close.

Well said, bill h.

With the generator running, there shouldn't be a parallel charge by the engine alternator, as the voltage on the house battery side of the isolator (if working properly) should shunt the alternator output to the chassis battery.

Lloyd wanted to run the genny off of the start/engine circuit without regard to recharging that circuit. What were trying to tell him is the battery maintainer will usually recharge only his house batteries while he's draining the start circuit.

When Bill G. stated:
"I added a second 45 watt IntelliPower converter/charger with a Smart Wizard to charge the start batteries when running the generator"
He's trying to insure that both the start and coach circuits are getting there charge regardless of which circuit he's hooked too.

Rusty's statement:
there shouldn't be a parallel charge by the engine alternator, as the voltage on the house battery side of the isolator (if working properly) should shunt the alternator output to the chassis battery.
Well said, even though Rusty is talking about the alternator this would still apply to two chargers. One on each circuit bank, because of the isolator's ability to separate each circuit.

Now, if you take the isolator out of the system (Big Switch, Perko, Green Knob) then you run the risk of parallel charging. The alternator and genny would be parallel if your running the gen set at the same time as your engine.

Bill H. is spot on when stating:
If anyone really wants to do the parallel charging thing, a standard constant duty RV relay can be wired up quite simply to obviate the isolator voltage drop.
Just use it only while trying to maintain or float voltage. To many people hook these things up to an electric switch and leave them on 24/7.

While they are called "constant duty" they are not meant to be left on for weeks or months at a time. For that you would need a latching relay or pulse type relay.

Bill H:
I do not like parallel charging. The only time it is OK in my book is when the banks are identical type, age, condition and state of discharge.

When the additional constant duty switch is turned on then you could have a parallel charge while running the genny. If your going to do this invest in a new style intelligent type of charger and make sure it can parallel charge for fear of burning out the alternator (unlikely) or the charger/s.

While adding an additional charger is simple to do, one must remember that some might mistake one circuit for another and also might not realize that there are additional considerations to think about. Which is the point of my post.

Bill N.Y.

Bill NY, when I said I did not like parallel charging, I was speaking with regard to batteries connected in parallel during charging. I should have been more clear. I will edit to clarify that. And probably add a little to the post, as well.

As far as parallel charging sources, situations can be all over the map, some good, some not good. I would be guided by the manufacturers' tech guys for each individual situation. I do parallal charging when my solar and gennie are running with no problem. As stated earlier, I ruined a charger in parallel, too. There are too many variables to make a blanket statement

Just cleaning up Lloyds response. It kind of got lost in the mix of my post...

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Lloyd Knudson
The reason I wanted to do that is when Igot home with the rv after the had had it for wk I tried to start genny and house batteries would not start it.then tried acc start nothing. so Iam thinking only works for cat. I may have to bite the bullet and pull the 8ds deep cycle and put 4 golf cart batteries. the 8ds just don't seem to be working out. the rv shope says every thing is ok but Iam nothappy with the use I can get out of them

I went back to rv shop and had them pull the 8d s and put in 4u2200 series golf cart batteries to the tune of $603.80. I sure hope thas the end of that problem. the 8d s just didn't hold up all though they where less then 2 years old. I use them in boat and get 6 to 8 years out of them not so in rv. I have smart charger on boat. the only thing was I tried to to use them for start bateries for about 6 months not knowning that the 2 8d s where start batteries and I replaced with deep cycle and it them outtook in short time. costly misstake. IF if you have regency and its original equipment the 8d s are the start batteries.
Lloyd