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Old 09-29-2012, 01:54 PM   #1
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Question Parasitic House Battery Drain

I have a 2007 Georgetown 370TS motorhome. The house batteries run down within 7 days unless I start the generator to recharge the batteries. I do not have shore power available where I store it.
After a week in order to start the generator I must first start the coach Ford motor and use the jump switch on the drivers panel to add the motor battery to the coach house battery and then there is enough power to start the generator. How many items are parasitic to the house batteries after I cut off the electric disconnect switch by the door when leaving the coach?
I have 2 12 volt batteries NAPA #8231 Lead Acid Deep Cycle 650CCA.
Thanks,
Elmer
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Old 09-29-2012, 02:50 PM   #2
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I'm not 100% sure if there are more but here goes.
1) fridge (if left on)
2) low pressure gas detector
3) a back feed to the rectifier
4) storage lights (I have bumped the switch on several occasions and not noticed on bright days) I will be taking the bulbs out and storing them in the lens so that I can install them when and if I need them.
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Old 09-29-2012, 03:36 PM   #3
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On my Class C Solera, the disconnect switch seems to disconnect essentially everything. Maybe a battery internal short? I would try disconnecting a battery wire and seeing if that stops the discharge.
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Old 09-29-2012, 04:46 PM   #4
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Yep, I'd second the idea to try disconnecting the battery if possible next time you store it and see if that stops the drain. If not, then it may just be the battery.

Usually if you activate the shut-off then it should kill the power to any of the battery draining applicances like a CO and/or LP detector, etc.
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Old 10-04-2012, 09:37 PM   #5
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I have a 2011 Georgetown 350. Had the same problem for almost a year. I finally convinced the dealer the batteries were bad because one of them got hot when charging, they were boiling over (I used several gallons of distilled water), and the propane gas detector kept going off during the night.

Once he replaced the batteries I can leave it 4 weeks after using the disconnect switch and the batteries will still show 3/4 charge and everything works/starts just fine.
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Old 10-05-2012, 08:06 AM   #6
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You need a battery disconnect switch. Leave the dome light on in your car for 7 days and see what happens. The newer your RV is, the more electronics are in it draining the battery. Simple things like power supplies for radio, TV, dvd player, etc. all add up. Fridge, electrical panel, gas detectors, etc. suck up even more juice. Hook up a DC ammeter in series with your battery terminal to measure draw on battery when you think you turned everything off. Things are still running you will find out.

The affordable works good enough solution here. Google battery quick disconnect terminal.
http://www.amazon.com/Moroso-74103-B.../dp/B000COO1P4
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Old 10-05-2012, 08:31 AM   #7
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Quote:
Originally Posted by oldprof1 View Post
I'm not 100% sure if there are more but here goes.
1) fridge (if left on)
2) low pressure gas detector
3) a back feed to the rectifier
4) storage lights (I have bumped the switch on several occasions and not noticed on bright days) I will be taking the bulbs out and storing them in the lens so that I can install them when and if I need them.
To this I will add "internal battery resistance" which will "self discharge" a battery over time; the radio (even when off); and any clocks powered by your house battery.

Using just the gas detector and the radio, there is about 1 amp of power used unless the battery is completely disconnected. At this very low discharge rate you will get a little over twice the life out of the battery than at the rated 100% discharge rate (5 amps per hour) or about 200 hours. This is for a BRAND NEW battery. As the battery is "cycled" (charged and discharged) total capacity decreases over time (see attachment). Desulphating batteries can help but not stop this process.

So a 100 amp hour battery bank will be completely discharged at a 1 amp hour draw in about 200 hours (a bit over 8 days).

If your house battery is more like most OEM batteries, it is most likely a 70 AH battery and will discharge below its usable voltage in about 140 hours with a 1 amp draw (about 6 days)

Using the on board converter to keep your batteries charged (provided you have a 3 stage charger) will keep your batteries healthy and prevent them from freezing. If you don't keep your camper plugged in or have a 3 stage converter, you must use a disconnect to completely remove power from the battery and use a solar charger to overcome power loss due to internal resistance.
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Old 10-06-2012, 05:13 PM   #8
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Originally Posted by joelek View Post
You need a battery disconnect switch. Leave the dome light on in your car for 7 days and see what happens. The newer your RV is, the more electronics are in it draining the battery. Simple things like power supplies for radio, TV, dvd player, etc. all add up.
My 2011 327DS has a pair of 12V batteries wired in parallel. I was surprised to discover that there's + power being drawn from both of the batteries. The battery disconnect relay is fed from a cable that is properly wired to balance the load between both batteries but there's at least one lightweight, independently fused, power line that's hooked to the other battery's + terminal.

I'd need two disconnect relays on my coach to fully disconnect the coach batteries or I'd have to move the tap(s) on the second battery to the first one.

Phil
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Old 10-06-2012, 05:34 PM   #9
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6 volt batteries

Along these same lines, I just replaced my oem 12 v batteries with two six volt golf cart batteries hooked up in series to create 12 volts. The new batteries are 230 amp hours, twice as much as the oem.

As stated, the older the batteries get, the less oomph they produce and the quicker they run down. And if you don't keep the water level up, they will go dead quick.

I neglected mine, and they lasted a little over a year and a half. Costco sells the 6 v batteries for about $85.00 ea. I bought mine at Battery Mart, they were a little more expensive, but they installed them for me.

They shouldn't run down now overnight with the furnace running!! LOL

Forrest
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Old 10-07-2012, 12:00 PM   #10
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Originally Posted by fbconsults View Post
Along these same lines, I just replaced my oem 12 v batteries with two six volt golf cart batteries hooked up in series to create 12 volts. The new batteries are 230 amp hours, twice as much as the oem.

Forrest
Actually, if the OEM batteries were a pair of 115AH 12V wired in parallel, you'd have the same 230AH that your series wired 6V ones have now. The (wrong) assumption here is that the battery's capacity was measured the same way. If you carefully check a deep cycle battery, you MAY find the specification on a label that states how the AH capacity was determined. Many of the 115AH batteries I've seen, including ones from WM were tested with a 1A load on them. You should expect the "full" capacity of the battery, when used in your RV, only when it's feeding the parasitic loads on it during storage.

All batteries have internal resistance in them. The higher the current load placed on the battery, the more power is dissipated internally as a result of this internal resistance. Go check any battery manufacturer's web site and look at their graphs of battery capacity and you'll see that the capacity drops as the load increases. If you want to make your batteries look better than they are, then you rate them when testing with a 1A load. The traditional load test for rating a deep cycle battery used to be either a 10 hour (10% of capacity) or a 20 hour (5% of capacity) load test. The "reserve capacity" rating is supposed to be done by placing a 25A load on a fully charged battery and counting the minutes until the voltage, under load, drops to 10.8V.

Golf cart batteries are designed for severe abusive use, since once a cart leaves the clubhouse it won't come back until at least nine holes have been played. These batteries are ususally manufactured with thick solid lead plates, great for long life with a 10%-20% of capacity load. This construction also has the smallest plate area (compared to perforated thin plates) and the poorest capacity to provide 250+A to run a starter motor for 5-10 seconds. Their intended use makes them a great match for RV use.

I had problems with the batteries in my (new) 2011 327DS from the day it was purchased. The batteries had sat in the coach, fully discharged, for an unknown period of time before it was purchased. (There wasn't enough charge in the pair to start the generator.) After our first trip, the coach sat for a month with an unknown multiple amp parasitic load from the jack system on it. During our second trip, a cold weather one, we discovered that, on an overnight dry camp with the furnace running, the propane detector would trip due to low battery voltage. I finally tested one of the coach batteries and discovered that, when fully charged, it's actual capacity with a 10A load on it was 45AH. Both batteries were replaced just before the end of the 1 year FR warranty and I'm planning on the next set being golf cart batteries. When I install the golf cart ones, I'll also get one of the auto fill systems to keep the water levels up which will avoid my having to crawl inside the wall of the coach with a mirror and flashlight.

The house batteries box location on my coach is one of the biggest gripes I have with it. I think that at the next FROG rally in Goshen, I'll ask the factory techs to show me how they expect the owner to check the water level in the house batteries. It'll be interesting to see their answer.

Phil
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