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12-22-2010, 12:54 PM
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#1
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Winnebago Camper
Join Date: Apr 2010
Location: Western Montana
Posts: 41
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Battery Boost Switch
Hi all
I was wondering if others run different types of batteries in their rigs for the starting and coach power systems?
I found that my Coach is wired so that the Battery Boost Switch is always activated while the ignition switch is in the RUN position. A simple check is to press the boost switch before starting and listen for the click, then press if after the engine is running, no click. It has been activated by the ignition switch. To verify I checked the solenoid power line it was indeed activated.
A question that comes to mind.
Why have a boost switch at all if indeed it is always activated when starting the motor?
The alternator does as it should and outputs loads of power. The problem is that is outputs to much. It was factory set at 14.5Vdc at the starting battery. This excessive voltage was measured with highly accurate digital meters and my TriMetric 2025.
Both sets of batteries get this excessive voltage all the time the engine is running. Not something good for the AGM batteries supplying power for the coach.
Just wondering if others have found this to be true with their machines?
__________________
Please do not toss your defective Converters / Inverters / etc. in the trash
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12-22-2010, 03:50 PM
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#2
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Winnebago Camper
Join Date: Nov 2010
Location: Williamsburg, VA
Posts: 37
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the boost switch connects the batteries when the key is in the start position. hard to hear when cranking the engine, but the boost relay drops out when cranking. the boost relay should be pulled in when the key is in the run position to allow the alternator to charge the chassis and house batteries. as for the AGMs, sorry, dont know.
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1999 Winnebago Minnie 29', Ford V10, Close to stock.
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12-22-2010, 04:43 PM
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#3
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Winnie-Wise
Join Date: Oct 2010
Location: Warren County, NJ
Posts: 300
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That is normal voltage for a alternator to put out.
Have you had any problems with any of the batteries?
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12-23-2010, 07:33 AM
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#4
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Winnebago Camper
Join Date: Apr 2010
Location: Western Montana
Posts: 41
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Yes - the first set of cheap RV/Marine batteries that were connected in parallel died after two years.
I added a Morningstar Tristar MPPT-60 solar charge controller that has very flexible charging capabilities and just wonder why a constant 14.6 could be the right thing for the new batteries. Unlike the alternator system the Morningstar outputs multiple different voltages depending on the batteries need.
__________________
Please do not toss your defective Converters / Inverters / etc. in the trash
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12-23-2010, 09:04 AM
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#5
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Winnebago Master
Join Date: Dec 2005
Location: Buxton, North Dakota
Posts: 1,037
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Many vehicles have AGM batteries. I have one as a start battery in my Jeep Wrangler and pickup. In cold weather the charging voltage is about 14.8 volts. Have not had any problems with them. If the isolation relay didn't do that, the only charging you would have is from the converter.
__________________
2003 Winnebago Adventurer 38G F53/ V10 605 watts of Solar
1999 Winnebago Brave 35C Handicap Equipped
F53/V10
1999 Jeep Cherokee & 1991 Jeep Wrangler Renegade
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12-23-2010, 09:27 AM
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#6
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Winnebago Master
Join Date: Jun 2003
Location: Palisade CO
Posts: 895
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I just replaced the two Interstate house batteries that came in my motor home after 7 years and 46,000 miles. One had a dead cell and the other had one cell with a very low specific gravity reading.
My alternator output averages 14.4 volts.
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Clay WA5NMR - Ex Snowbird - 1 year, Ex Full timer for 11 years - 2004 Winnebago Sightseer 35N Workhorse chassis. Honda Accord toad.
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12-23-2010, 09:27 AM
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#7
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Winnebago Camper
Join Date: Apr 2010
Location: Western Montana
Posts: 41
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Thanks for the responses
Still trying to wrap my head around the alternator thing - guess I have a ways to go before I fully understand the issues
Another question
"Why do battery manufacturers and solar charge controllers promote three stage charging if the stock alternator system does the job?"
I don't like seeing 14.6 Volts at the battery for 5 or 6 hours at a time while driving, yes sure the current drops to a very low value since the battery voltage rises up. My solar charge controller recommends 1 to 2 hours max duration at that higher voltage otherwise the batteries gas / boil excessively.
Yes agreed the voltage should increase in colder weather the reason for battery temperature sensors. The stock alternator system had no temperature sensors, my solar system does.
I guess my system is a bit different from others. I tossed out the cheap "Converter" that was basically a 12Vdc power supply, replaced it with a proper three stage battery charger / converter and installed a proper PV powered Morningstar MPPT-60 Charge controller, they both do a great job at keeping the coach batteries up.
My thought is to simply add a cut off switch at the Boost Switch to disable the alternator from charging the coach batteries. Then maybe adding a Sterling Power A2B charging system.
__________________
Please do not toss your defective Converters / Inverters / etc. in the trash
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12-23-2010, 10:57 AM
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#8
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Winnebago Camper
Join Date: Oct 2010
Posts: 19
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Normal alternator charging should be in the range of 13.7 - 14.6V. It is normal to see slightly higher periodically but never constantly. If you have anything higher, replace the alternator
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12-23-2010, 01:09 PM
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#9
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Winnebago Master
Join Date: Dec 2005
Location: Buxton, North Dakota
Posts: 1,037
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Optima Charging Recommendations
It looks like your charging voltage is within the limits recommended by Optima
Optima Recommended Charging Voltage and Current
__________________
2003 Winnebago Adventurer 38G F53/ V10 605 watts of Solar
1999 Winnebago Brave 35C Handicap Equipped
F53/V10
1999 Jeep Cherokee & 1991 Jeep Wrangler Renegade
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