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02-06-2017, 09:31 AM
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#1
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Senior Member
Join Date: Feb 2016
Posts: 655
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Charging Both Battery Sets in Storage
I am getting familiar with our 'new to us' 2011 Coachmen, first bus. I have two 12 volt chassis batteries in parallel, and two 6 volt house batteries in series. History and care of all batteries is unknown but at the moment all are working well. Due to poor access I plan to pull them out, clean them, set distilled water levels correctly, document sizes and ages, and install a remote watering system this month. My question for today:
Can I use a single battery charger to maintain all four batteries in storage? I have presently hooked up a charger to the chassis batteries across the parallel posts that I confirmed to be 12.3 volts. If I added jumpers to also pick up the 12 volt series posts on the house battery set could this lead to any problems? Further background, the coach has a single battery disconnect for both banks. When it is off, there are at least some 12 volt items energized, including backup cameras and some overhead lights, making me think that the single battery disconnect is actually only isolating the chassis batteries.
Thanks for any advice and info you can share!
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2022 RAM 3500 Cummins SRW long bed, 2019 Open Range 319 RLS, Reese Goosebox, disk brakes
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02-06-2017, 10:15 AM
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#2
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Senior Member
Monaco Owners Club
Join Date: Jan 2008
Location: Olympia, Wa
Posts: 2,772
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You should be fine. That is what the commercial battery tenders do with on board charging systems. You may only need the jumper to the positives as both banks could/ should go to ground.
LEN
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2004 Clss C 31' Winnebgo
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02-06-2017, 10:40 AM
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#3
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Senior Member
Join Date: Jul 2010
Location: FT on the Road
Posts: 3,895
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I wouldn't. Battery profiles need to be checked. You may find one set needs an absorb voltage of x while the other requires y. The times to charge could be different. Float voltages can have the same issues as they can be different.
In general one should only charge like batteries together (like as in model, make, age, state, etc.). If one doesn't the stronger set can/will be degraded.
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Cheers!
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02-06-2017, 10:46 AM
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#4
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Senior Member
Tiffin Owners Club Appalachian Campers Mid Atlantic Campers Coastal Campers Freightliner Owners Club
Join Date: Jan 2015
Posts: 1,622
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Well, but......
When you are driving the coach, your engine alternator charges the chassis battery, and then connects in the house battery bank to that thru a charge solenoid (relay). So certainly when driving/charging, they are electrically tied together.
And, when you hit the Aux start button on your dash, it connects both battery banks together.
So if I HAD to, it's probably safe for a period of time. They make a device called an Amp-L-Start which would make the connection for you, when the batteries are in the coach. Turn on your house battery charger, and it will keep the chassis batteries topped off.
I wouldn't do it, but I have two chargers so no big deal. You can also pick up trickle chargers for a couple bucks at the Tool Supply stores. Over the winter, I keep one on my motorcycle, another on a tractor, and have a third for an auto if I'm planning to be gone for a month or more.
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DaveB, Raleigh, NC
2015 Tiffin RED 33AA, w/Honda CRV
VMSpc, Magnum BMK/ARC50
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02-06-2017, 10:48 AM
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#5
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Senior Member
Winnebago Owners Club Workhorse Chassis Owner
Join Date: May 2016
Location: Kamloops, BC, 60 miles from the Center of the Universe according to the Rinpoche, of the SF monks.
Posts: 8,018
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IF you decide to charge them all at the same time, disconnect them after they are charged. Being different, one could discharge the others if you leave them connected together. Best to charge the similar ones, then the others. If they are cleaned and stored properly they can sit for extended time without any attention. Just give them each a top-up before you put them back in your rig. Good luck.
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Happy Glamping, Norman & Elna. 2008 Winnebago Adventurer 38J, W24, dozens of small thirsty ponies. Retired after 40 years wrenching on trucks! 2010 Ford Ranger toad with bicycles or KLR 650 in the back. Easy to spot an RVer, they always walk around with a screwdriver or wrench in one hand!
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02-06-2017, 11:03 AM
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#6
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Senior Member
Winnebago Owners Club Solo Rvers Club
Join Date: May 2015
Posts: 1,869
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On a modern 2011 model, you should have a "smart" battery isolator that bridges all your batteries together when it senses charge voltage, generally above 13, across one battery string or the other. This is fairly common, so that the coach charger / converter also puts charge to the chassis batteries when you have the coach on shore power. So if you have power at your storage location, if this is the case, you can just put your coach on shore power. Since it's a modern 2011 model, its built in converter charger will be "smart" and will drop to float charge mode and not over-charge your batteries.
How to confirm? Put your RV on shore power. If you are stored in a quiet spot, you should hear a "click" after a few seconds, that is the contactor in the smart isolator tying the the two battery strings together because it sensed the converter putting charge voltage out (13 or more volts). You can also confirm visually with a voltage reading across the chassis batteries.
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Randy - Manhattan, Kansas
2015 Vista 27N
2024 Ford Escape Plug-In Hybrid
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02-06-2017, 12:27 PM
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#8
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Senior Member
Join Date: Nov 2011
Location: Full time RV'er
Posts: 5,528
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Fully charge the batteries. Measure the resting voltage across each set. Than pull them out, clean them along with all the connectors. Check water levels. Put 2 oz of mineral oil (3-in-1 Oil) in each cell, top them with distilled water. If they are already filled with water, suck out 2 oz with a turkey baster before adding the 3-in-1 oil. Reinstall the batteries after cleaning all the corrosion residue from the battery trays. And connect ONLY the positive cables. Leave the negative cables unconnected while the RV is in storage.
Next trip, (assuming no more the 2-3 months away), reconnect the grounds. Check the voltage. If should be fine. 11.96V or greater. With a good battery, it'll likely be 12.4 or greater. Drive away. If the voltage is low, have them load tested or just limp along with them that way. I've done it for years (but I don't boondock much).
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02-06-2017, 01:11 PM
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#9
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Senior Member
Join Date: Dec 2013
Location: Lake Havasu City, AZ & Plover, WI
Posts: 6,403
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The Amp-L-Start is a good product. When charge is available from shore power or generator, it will take 15 amps from the house batteries to keep the chassis batteries up to full charge. When there is no outside charge available, it will not drain the house batteries like many trickle chargers will. Keep in mind that after a days driving, all batteries are charged to approx 13.6 volts. That's plenty for the chassis batteries as they are then fully charged. However, the deep cycle house batteries are only at about 85% charge. They require a three stage charger (the inverter/charger) to charge up to 15+ volts for a period of time to saturate the plates. A lot of people think the house batteries are full charged at the end of a trip and then wonder why they discharge more quickly to 50%. That's why.
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2006 Monaco Executive 44 Denali
2013 43 QGP Allegro Bus ( SOLD )
2013 Avalanche
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02-06-2017, 06:25 PM
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#10
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Senior Member
Join Date: Feb 2016
Posts: 655
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An Update
I made it out to the storage yard today. I tried Powercat's suggestion to plug in my shore power line but unfortunately I tripped the breaker. There are 4 of us on a 15 amp circuit. I might try again if I can determine how to shut down all house loads and get down to 3 or 4 amps. I received a bundle of wiring diagrams from Coachmen today and will work to understand them. In the meantime I will alternate which battery set I put on the charger. Today, the chassis batteries were at 12.8 volts, and the house batteries were 11.5. I set up the charger on house batteries, and have about a 130 mile trip on the books for tomorrow. I looked at the Amp-L-Start and the other links from 2 Stroker, thanks very much! One of these devices will be simpler than setting up 2 chargers whenever we park, just have to set up 1 and the device will manage the 2nd set of batteries from there.
I'll get them all removed and cleaned up/serviced in about a week or two. There are a few items ahead of batteries on the list. Thanks to everyone for your time and advice!
Oh, I did notice today that I will have to get a different set of cable jumpers as the present ones are going to block installing a watering system....
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2022 RAM 3500 Cummins SRW long bed, 2019 Open Range 319 RLS, Reese Goosebox, disk brakes
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02-07-2017, 10:08 AM
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#11
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Senior Member
Winnebago Owners Club Solo Rvers Club
Join Date: May 2015
Posts: 1,869
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Quote:
Originally Posted by Dark Sky
I made it out to the storage yard today. I tried Powercat's suggestion to plug in my shore power line but unfortunately I tripped the breaker. There are 4 of us on a 15 amp circuit.
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When you plug in a RV to shore power, the converter charger will initially start up in "bulk charge" mode for at minimum a few seconds, during this time it will draw as much as 700 watts, if your RV has a typical 55 Amp max output converter/charger. Could be more if you have a bigger converter/charger.
During this initial time, the converter charger senses the state of the batteries. If it sensed that batteries need bulk charge it will stay at around that power draw level until the batteries charge to 70 or 80 percent. If batteries are already at 70 or 80 percent, then after a few seconds it will drop down to the "topping off" mode and will draw many less watts. Finally it will go into float charge mode and will draw less than 50 watts.
The converter charger is on it's own circuit breaker in your RV's breaker box, so you could take it off and still plug in your RV to be able to use it's outlets. Then you could put portable battery charger that draws less watts on.
If your RV has the smart battery isolator, the portable battery charger will still cause it to tie the batteries together so that one should be enough to tend to all the batteries.
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Randy - Manhattan, Kansas
2015 Vista 27N
2024 Ford Escape Plug-In Hybrid
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02-08-2017, 08:03 AM
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#12
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Senior Member
Join Date: Feb 2016
Posts: 655
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With the available amps at my storage yard circuit, I'll never be able to plug in the shore power connection. I'll look for a breaker that takes the inverter/converter off line, but I'm coming back to the idea of just getting a 2nd battery charger. For a longer stay in storage it will only be a couple of minutes to hook them both up, especially if I add permanent connections to the battery sets and use a couple of two pin SAE connectors. Then both sets should get the charge profile that they need for longevity. I did find another battery isolation switch. The large obvious one only isolates the chassis batteries. A toggle switch with a status LED at the front door takes the house batteries off line, but I need to test and see if there aren't some small loads that remain hardwired in. This may include the CO & propane sensors and the door steps.
A 140 mile trip brought the voltage up on both battery sets.I will have to start logging my readings, but from memory the 6v house batteries were up to about 12.8 v and the chassis set was something like 13.2, so it looks like they are healthy enough to take a charge. The good news is we have a very busy camping year planned. Short trips in February, Big Bend in March, short trips in April through June, Ontario in July, and Atlantic seaboard in September-October. I won't have to worry about longer term storage until then, should have a very good handle on the electrical systems by that time. Thanks again!
__________________
2022 RAM 3500 Cummins SRW long bed, 2019 Open Range 319 RLS, Reese Goosebox, disk brakes
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02-08-2017, 09:11 AM
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#13
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Senior Member
Forest River Owners Club
Join Date: Feb 2015
Location: Johnson City, TX
Posts: 1,060
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Quote:
Originally Posted by Crasher
The Amp-L-Start is a good product. When charge is available from shore power or generator, it will take 15 amps from the house batteries to keep the chassis batteries up to full charge. When there is no outside charge available, it will not drain the house batteries like many trickle chargers will.
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I love mine.
Keep in mind that when you leave an RV plugged in 24/7, you need to check the water in the batteries at least monthly. My RV's manual even says "every 2-3 weeks", but I've found monthly to be fine.
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2018 Rockwood 2304DS Ultra Light pulled by 2018 Ram 2500 Cummins Diesel 4x4
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