Tow vehicle overcharging Scamp battery - Fiberglass RV


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Old 10-08-2013, 10:28 AM   #1
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Name: John Michael
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Tow vehicle overcharging Scamp battery

Fgrv folks.

My new Scamp is due Jan 1st and in my excitement I may be over-processing a bit so please tell me to lighten up if you feel its warranted.

I am planning a 5 week trip with daily driving. I hope to put a charge wizard on my converter, but how about the tow vehicle charging wire. Will the daily driving charge and then over-charge my battery and boil off lots of water? I am considering a cut off switch that I can open when the battery is full though something automatic would be easier than climbing out the back hatch every few minutes and checking the battery with a voltmeter. Does such a device exist? Will the tow vehicle itself limit the over charging with its own regulation? Is this much ado about nothing?

Best Autumn to you all, john
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Old 10-08-2013, 12:23 PM   #2
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John,

Welcome to the Scamps.

If you take your voltage from the battery of your tow vehicle you can no more overcharge your trailer battery than you can over charge your tow vehicle's battery.

Of course the wire to your tow vehicle should be protected with a fuse. I pick off voltage at my fuse box, using one of the unused fuses.

As well I have a switch in series with the wire to the tow vehicle to allow me to turn on the voltage to the trailer once we're moving. This can also be handled with a solenoid that switches voltage to the trailer's battery once the car is running as described in a recent post.

We carry a small bottle of distilled water and I check our battery water level as we travel, no more than once a month.
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Old 10-08-2013, 02:28 PM   #3
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John, Welcome to FGRV.

AFAICT the charge wire from the alternator is often just in parallel to the TV battery.

Since the charge wire(s) between the TV and the TT are usually 10 gauge, you will get significant voltage drop in that line and so you will be providing less charging voltage than the alternator is providing to the TV battery.

Now, if the TT battery is ever actually fully charged and you managed to provide a "bulk charge" voltage to the TT battery (doubtful given the wire gauge) then you could theoretically over charge the TT battery.

This seems really unlikely however.
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Old 10-08-2013, 03:04 PM   #4
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Not trying to hijack this thread. I think this thread may have solved a problem for me. A truck I use to tow a lot of non RV trailers with shows signs of over charging (electrolyte around the vents). After a lot of troubleshooting I have never been able to detect any charging issues. A lot of these trailers have weak batteries especially the dump trailers. I now think the weak trailer batteries are causing the truck battery over charge issues. When ever I work on the truck no trailers are attached. If my theory is correct the tow vehicle is more likely to have the charging issues.
Thanks
Eddie
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Old 10-08-2013, 03:28 PM   #5
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I think dead, or almost dead batteries on the TT is a large problem in general. The alternator may very well continue to try to charge based on having a bad TT battery it is trying to charge, potentially overcharging the TV battery.
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Old 10-08-2013, 04:30 PM   #6
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Originally Posted by jwcolby54 View Post
I think dead, or almost dead batteries on the TT is a large problem in general. The alternator may very well continue to try to charge based on having a bad TT battery it is trying to charge, potentially overcharging the TV battery.

Simply put.... It's not going to happen that way. It don't work that way.
Don't worry about overcharging your trailer battery. It's not going to happen. Many people have put in extra heavy wire in an attempt to get the trailer battery to full charge.

And neither is the trailer battery going to cause the tow battery to overcharge.
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Old 10-08-2013, 04:51 PM   #7
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Simply put.... It's not going to happen that way. It don't work that way.
Don't worry about overcharging your trailer battery. It's not going to happen. Many people have put in extra heavy wire in an attempt to get the trailer battery to full charge.

And neither is the trailer battery going to cause the tow battery to overcharge.
Byron, I understand the first part and agree entirely. However if the TT battery is "dead", i.e. continues to accept a large current, then what happens?

I have zero expertise as a mechanic. My thought was simply that the alternator sees a large current being drawn and continues to put out a high voltage / current in an attempt to service the request.

Again, I am just searching for information, not arguing your statement that the second part "won't happen".
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Old 10-08-2013, 05:11 PM   #8
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Byron, I understand the first part and agree entirely. However if the TT battery is "dead", i.e. continues to accept a large current, then what happens?

I have zero expertise as a mechanic. My thought was simply that the alternator sees a large current being drawn and continues to put out a high voltage / current in an attempt to service the request.

Again, I am just searching for information, not arguing your statement that the second part "won't happen".
One part of your statement is correct, there will be a higher voltage present at the tow battery than at the trailer battery. This caused by the IR drop of the wire going to the trailer battery. When the voltage regulator sees the cut off voltage it will stop charging. The two batteries will continue to attempt to get to an equilibrium. Meaning the tow battery will continue to supply current to the trailer battery. When tow battery gets below the threshold of voltage regulator the charging will begin again until the voltage regulator see the shut off voltage, this process will continue until that equilibrium is reached. No overcharging can occur assuming the voltage regulator (built into the alternator) is operating properly.
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Old 10-08-2013, 05:16 PM   #9
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As mentined multiple times, your TV usualy won't overcharge your rigs battery if all is well.
However, "Charge Wizard" is a trademark belonging to Progressive Dynamics denoting it's multi stage charging system. If you don't have it from the factory (no chance!) you won't have one unless you wire a new Progressive Dynamics converter section into your existing system. But leave that worry until you get back, it's not a biggie when everything is new.

But, if you can find one, a "VoltMinder" is handy to tell you actual condition and chargeing values in your system.
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Old 10-08-2013, 05:30 PM   #10
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As mentined multiple times, your TV usualy won't overcharge your rigs battery if all is well.
However, "Charge Wizard" is a trademark belonging to Progressive Dynamics denoting it's multi stage charging system. If you don't have it from the factory (no chance!) you won't have one unless you wire a new Progressive Dynamics converter section into your existing system. But leave that worry until you get back, it's not a biggie when everything is new.

But, if you can find one, a "VoltMinder" is handy to tell you actual condition and chargeing values in your system.
I understand your love of Progressive Dynamics, but there's many other 3 stage converter/chargers on the market, without the need to purchase the add-on "Charge Wizard". If it works for you that's great.
NOTE: This discussion was about tow vehicle charging, not shore power charging.
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Old 10-08-2013, 05:50 PM   #11
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The P.O. stated: "I hope to put a charge wizard on my converter" in the post.

And I replied that let him know that it wasn't yet a generic term, and that it wasn't something that could be "added" to an existing converter anyway.

And the only add-on from PD pertaining to the Charge Wizard system I am aware of is the indicator pendant, which isn't needed for the Charge Wizard to work correctly.

While some other converters used in FGRV's may be upgradeable to a "Multi Charge Level" charging system, let's respect what PD brought into the world.

Scamp owners wouldn't appreciate someone referring to ones Scamp as "One of those Burro things"
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Old 10-08-2013, 05:55 PM   #12
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Originally Posted by Bob Miller View Post
The P.O. stated: "I hope to put a charge wizard on my converter" in the post.

And I replied that let him know that it wasn't yet a generic term, and that it wasn't something that could be "added" to an existing converter anyway.

And the only add-on from PD pertaining to the Charge Wizard system I am aware of is the indicator pendant, which isn't needed for the Charge Wizard to work correctly.

While some other converters used in FGRV's may be upgradeable to a "Multi Charge Level" charging system, let's respect what PD brought into the world.

Scamp owners wouldn't appreciate someone referring to ones Scamp as "One of those Burro things"
I believe Shumacher was the first or close to the first to come up with militstage charging. So let's give credit where credit's due.
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Old 10-08-2013, 05:57 PM   #13
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Assume for a minute that the tt battery is truly fully discharged and presents 11.5 volts to the cable at it's terminals and accepts a large current. Wouldn't this cause the alternator to see a small enough voltage to continue the charge phase, even when the tv battery is fully charged?
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Old 10-08-2013, 05:59 PM   #14
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Assume for a minute that the tt battery is truly fully discharged and presents 11.5 volts to the cable at it's terminals and accepts a large current. Wouldn't this cause the alternator to see a small enough voltage to continue the charge phase, even when the tv battery is fully charged?
I just knew you were going to try and argue with me. You'll just have to figure it out for yourself.
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