u.s mma

So my battery isolator is giving my camper battery right at 17 volts. Or it was for a minute until I turned my truck off and disconnected it.It had been working fine, camper was at 14.2 or so. I have 8 gauge hot wires and a 6 gauge ground. Im thinking the isolator is screwy, I don't no what else would cause this. Fresh alternator, my primary battery is right at 14.7 while the truck is running. Any advice would be appreciated. I feel like a real hillbilly pulling my camper battery out and charging it with jumpers on my front bumper. Thanks, Jordan.

CTD NUT

The best advice I could give would be to ditch the isolator. They suck. I have never known anyone to ever have one work well for any length of time and currently know nobody that uses them. Solenoids are the way to go.

But to answer your question, yes, if you are inputting 14v to the isolator and output at the battery is 17v, the isolator is the problem.

2006Mega

check the water level in the batteries that saw the 17v, make sure that none boiled off.

FiverBob

Man am I ever confused. What are we calling a battery isolator? What does it do? Do you mean an isolator relay that will kill the 12v line from the truck to the trailer when the ignition switch is turned off? If so, what apparatus is in an isolator that can take 14v and make 17v out of it? Wow, that is cool.

I guess the real question is "what are we calling an isolator?"

Bob

CTD NUT

Well, there you go....could just be me making assumptions. I think you are referring to something like this, which is just a relay/solenoid:



I was referring to the older heat sink-encased units that are NOT solenoids like this:



^^Those suck. They drop on average, 1 volt of charging power from the charging system and fail frequently....they do not have a long service life from my experience. Since the OP said the voltage jumped to 17v and knowing a solenoid could not do this, I assumed he was using a traditional isolator.

HiJenks

I'm with FiverBob.....
I have to question the Isolator input of 14v and output of 17v.
My understanding of an isolator is that it allows current flow in one direction, by using diodes, so that drawing from the "isolated" battery won't effect the main battery.

If the camper battery was being charged by the vehicle alternator the input and output from the isolator could have been 17v.

CTD NUT

I would agree. Only a step up transformer can accomplish an increase of output voltage over input voltage and there sure isn't one of those in an isolator.....to my knowledge!

FiverBob

Yep, and they don't work well with DC.

I know what both "isolators" look like - - I have the relay on my truck. The diodes are used to prevent a low battery on the RV running down the truck batteries if stopped like overnight and still plugged in. The relay just plain opens the circuit between the truck and RV, normally hooked to the ignition to turn on and off. There is no way you can put 14v in one side and get 17v out the other side. Normally an alternator will not put out 17v, that is only seen with special chargers that rebalance your cells. I think if an alternator put out 17v, there would be something wrong.

u.s mma

Well, Im confused. Unless my multimeter was just reading off, but when I was getting that 17 volt reading the dc lights in the camper got way brighter. I checked the primary battery in my truck, it was reading at 14.6-.7, so its not the alternator. So, it sounds like an isolator would not be able to increase the voltage,. Yep, Im lost. Ill connect it again in the morning and report back.

Jeff in TD

Instead of taking a voltage reading at your truck's batteries, try taking a reading at the alternator with it running and reved up a bit.

I'm wondering if the truck's regulator could be messed up, but with the batteries having the ability to absorb lots of power and the smaller wire from the alternator that you aren't seeing the alternaor's true output voltage at the battery?

It doesn't make sense to me how an isolator could increase the voltage to the camper...

John Faughn

There seems to be an inconsistent ideas here , where you take your measurements and maybe what you think the voltages should be .
So because the the communication method of a forum , we have to state things clearly up front / or verify what is being said ?
Charging voltage from the alt. should be about 14.5 - 14.7 , depending on state of charge the battery is in , but also need to measure amps from alt. to battery ?
A fully charge lead acid battery [ at rest , at least a 1/2 hour ] after being fully charged , should be 12.75 volts .
Then knowing what you have for a camper / how it is set up , many have transformers / converters in them , for AC to DC , combined with a charger , so knowing how your trailer is wired [ schematic / diagram ] .
Then what kind of meter do you have , some of the older analog meters , that had what looked like a strip of a mirror across the face , could get maladjusted , by your fingers touching the plastic face of meter .
I always calibrate / confirm before testing , even simple tools like test lights , many times , under a dash , worst possible times , I would get several negative results , only to find that the ground connection was not good .

Jeff in TD

That thought occurred to me, too, that the camper could have a solar charging system who's controller is messed up, or the converter/charger might not be putting out correct voltage.

I kind of assumed the voltage reading in the camper would have been with the camper unplugged from AC...

FiverBob

Well DUH on us, Jeff. I assummed the same thing. But, even a converter that is operating correctly is not putting out 17v - - unless it could be on balancing mode as I stated earlier, but most converters won't even go that high doing that, only higher priced inverter/chargers.

Jeff in TD

I didn't mean for it to sound like that... I just meant I wondered if something else could have overcharged the camper battery...