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Old 01-02-2012, 11:31 PM   #1
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Default Battery separator override

There was a very good discussion on the Yahoo board a while ago about batteries using a lot of water, charge voltages, battery types, etc. We were among the ones that have noticed a fairly large amount of water used by our two SCS200 Trojan 12volts, in our 07 Roadtrek C190P. It could be plugged in all winter on shore power, in the garage, and barely use any water at all, but after 2500 miles of driving it would be down half way to the plates. The net conclusion was that the driving voltage (in the Chevy) of 14.1 volts is too high and is causing the batteries to gas continuously on long drives, especially when you start out with them fully charged. AGM users may also have issues of the batteries getting hot, and/or damaged by the continuously too high voltage.

I looked at 12v to 12v chargers, but they are very spendy, and would be a lot of work to put in, requiring an added contactor and a bunch of wiring. At that point a disconnect for the coach batteries looked to be a better solution. A big disconnect switch would work, but could accidentally be left off when you want charging of all the batteries, and on shore power (the chassis battery wouldn't be charged).

When I looked closely at the separator, it was obvious it is just a single pole, normally open, contactor, with an add on control to turn it on when it sees charge voltage from either side. The great part is that the add on module bolts onto the contactor coil inputs, so it can be easily modified to break one of the coil connections and be able to turn the contactor off when you want to. A simple switch in that line would work, but again could be forgotten like a big switch.



My plan was to find a way that it would work totally as a normal separator would, except when the van was running, when it could be disconnected manually. That way if it was forgotten on, it wouldn't affect anything except when you are driving, and with an indicator light on the switch, on the dash, you should see it immediately, if it is forgotten.

The circuit is simple. Power from the run side of the ignition powers the coil of a small relay, through the override switch. The relay's normally closed contacts are put into the line from the control module to the contactor of the separator. Because of the normally closed contacts, the separator works as stock, unless the relay is triggered, and it can't be triggered unless the van is running because it gets it's power from the run side of the ignition.

Getting the run side power was not terrible, but I did cheat a bit. I didn't want to open up the taped and sleeved harnesses to get to wires to splice to, and fuse box had "spare" fuse positions available. I also didn't want to disassemble the fuse box to tap into the spare fuse mount, so I made a "fuse" adapter to get the power. The fuse socket has power on one side from a built in buss, but the output side isn't connected to anything. By using a fuse, and adding a wire to it on the output side, you can get the power without doing anything else. Only downside is if you blow the fuse, you have to do another one. If this was a critical circuit, I would use a 30 amp fuse and add an inline 10 amp, but it is no big deal if this circuit doesn't work for a little while, so I didn't do an inline fuse.

Here is the modified fuse.



And how it sits in the fuse box.



The relay mounts on an existing bolt on the power steering reservoir.



There was room in the headlight switch to add the override switch. It has an indicator that only comes on when it has power and is switched on, so it only lights when the separator is disconnected by the switch, with the motor running.



I drilled a 3/8" hole through the firewall just inboard of the harness boot and seal, which I couldn't get the wires through. My harness was only 1/4", which allowed me many wraps of friction taped right at the hole to seal it and protect the wires, as I couldn't get at it to add a grommet.



I put a plug and socket in the wires so the could be unplugged if I have to remove the headlight switch in the future, and tied the harness up under the dash.



This is the underhood wiring before harnessing and tieback.



And with it taped and finished off.



You can see the tap in to the controller to contactor at the bottom of the separator. I just unbolted the small strap, bolted a faston onto the strap, which was connected to the controller, and put a ring terminal connection at the contactor.

I haven't run the van to test it yet, but I did simulate the engine charge voltage with a battery charger on the chassis battery, with the key in the run position, and it worked as expected.

I will be very interesting to see what effect it will have on our water use and battery life.

Almost forgot the important part. Under $15 and about 3 hrs work. Maybe a 2 or 3 in difficulty, minimal tools needed.
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Old 01-03-2012, 12:39 AM   #2
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Default Re: Battery separator override

Nice work Jim, both on the simple design and the execution of it!

Dick, Marti, & Glen RT09/10C190P "no more deadlines" Allegany NY (currently in Fort Bragg CA)
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Old 01-03-2012, 11:02 AM   #3
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Default Re: Battery separator override

Interesting and effective solution to an equally interesting problem.

Do you think this problem would affect those with an isolator? Or would the .5 volt drop caused by the isolator prevent this problem?

I wonder if the alternator voltage at highway travel speeds is higher than the 14.1 volts you mentioned.

Did anyone in the discussions try Hydrocaps? http://hydrocapcorp.com/about.htm They are advertised as being able to recombine the hydrogen and oxygen gasses into pure water that is returned to the battery.
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Old 01-03-2012, 12:36 PM   #4
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Default Re: Battery separator override

Quote:
Originally Posted by markopolo
Interesting and effective solution to an equally interesting problem.

Do you think this problem would affect those with an isolator? Or would the .5 volt drop caused by the isolator prevent this problem?

I wonder if the alternator voltage at highway travel speeds is higher than the 14.1 volts you mentioned.

Did anyone in the discussions try Hydrocaps? http://hydrocapcorp.com/about.htm They are advertised as being able to recombine the hydrogen and oxygen gasses into pure water that is returned to the battery.
It appears that the folks with separators have less water usage than those with isolators. I had heard an even higher voltage drop of .7 volts with an isolator, but I have never actually measured one. That would put you very well within the "float" voltage for the batteries. It would also make them charge a bit slower, and possibly not get to a full 100%. Many of the folks that have isolators, are also in Dodges, which seem to run a bit lower on voltage when warmed up, IIRC. Our 07 Chevy runs right at 14.0/14.1 once warm, and doesn't vary with speed at all.

No one ever mentioned the Hydrocaps, I will have to look into that, thanks.
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Old 01-04-2012, 07:55 PM   #5
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Default Re: Battery separator override

Quote:
Originally Posted by booster
.............. I had heard an even higher voltage drop of .7 volts with an isolator, but I have never actually measured one. That would put you very well within the "float" voltage for the batteries. It would also make them charge a bit slower, and possibly not get to a full 100%. .......................
That was my concern with my B+ RV. It had a converter that only put out 13.8v and about that same voltage when running the motor after the isolator loss. I wondered if the battery would ever get 100% charged. Newer/better RV's will have a 3 stage charger so your batteries will get fully charged whenever you plug in.

I'm straying a little off-topic but it is all related. For example, if someone has a converter/charger that only outputs 13.8v like mine did, and they have battery separator like yours then they could actually use the the 14.1v or so from the alternator to get their batteries fully charged while driving.
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Old 01-04-2012, 08:07 PM   #6
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Default Re: Battery separator override

Quote:
Originally Posted by markopolo

I'm straying a little off-topic but it is all related. For example, if someone has a converter/charger that only outputs 13.8v like mine did, and they have battery separator like yours then they could actually use the the 14.1v or so from the alternator to get their batteries fully charged while driving.
You are absolutely correct. Having the 14.1 volts is a good thing if you driving a short distance and need to top off the batteries. You don't run into problems until the drives get long, with the batteries full. I surely wouldn't want to do anything that would just drop the voltage all the time, for exactly the reasons you state. I am sure it will take us a while to learn the appropriate amount of time to leave the separator on, and when to turn it off. The good thing is that it can only be off while driving.

On our last, fairly long, trip last year (13 days, 2700 miles), we had shore power every night, so we drove pretty much the entire time with full batteries seeing 14.1 volts. That is somewhere in the 55 hours of overchanging voltage time.
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Old 01-09-2012, 05:11 PM   #7
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Default Re: Battery separator override

Ours is a 2009 RT190V, Chevrolet, and uses a Separator, and the 3 stage charger/inverter.

Do the house batteries get charging power directly from the alternator, when driving, or does it get any conditioning from the charger/inverter?
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Old 01-09-2012, 06:23 PM   #8
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Default Re: Battery separator override

Quote:
Originally Posted by Photog
Ours is a 2009 RT190V, Chevrolet, and uses a Separator, and the 3 stage charger/inverter.

Do the house batteries get charging power directly from the alternator, when driving, or does it get any conditioning from the charger/inverter?
Directly from the alternator, and if yours is the same as our 07 Chevy, the batteries are probably seeing 14.0/14.1 volts continuously while driving.
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Old 01-09-2012, 07:45 PM   #9
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Default Re: Battery separator override

So what kind of schedule are you going to use with your switch, when you are traveling?
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Old 01-09-2012, 08:00 PM   #10
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Default Re: Battery separator override

Quote:
Originally Posted by Photog
So what kind of schedule are you going to use with your switch, when you are traveling?
I think there will be a bit of a learning curve on that, especially with the added capacity we have now (375AH). I do know that when we leave home, after being plugged in and fully charged, we will run with the separator disconnected and run the frig off the starting battery while driving.

If we start out with partially discharged batteries, we will have to guess a bit until we learn how long to leave it connected, but it is easy to check by disconnecting it and seeing what the battery voltage reads for the coach batteries.

Luckily, a bit of miss in either direction causes very very little risk of anything bad happening.
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