How long store without shore power?

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How long store without shore power?

March 17, 2013, 07:13:50 pm

I have not found this though I imagine it is answered within some prior discussion. If a coach must be parked with no shore power available, and you do not want to leave the generator on Auto, then how long can a coach sit and still be cranked and no batteries damaged if the coach is not connected to shore power?

Assume good batteries and that for voltage drains the refrigerator is off, the 12v system is turned off, level system off (I understand the slide bladder air tank is kept filled even with 12v disconnect switch thrown), no heat system is left on.

Perhaps the better option is to leave the generator in Auto but I am hesitant to leave it that way unattended.

Mike

Re: How long store without shore power?

Reply #1 – March 17, 2013, 07:34:44 pm

The electrical gurus probably have a better answer but here is something from Trojan's web site:

"All batteries, regardless of their chemistry, self-discharge. The rate of self-discharge depends on the type of battery, the age of the battery, and the storage temperature the batteries are exposed to. As an estimate, Trojan batteries self-discharge approximately 4% per week at 80o F. "

So I would guess that if you disconnect both house and start batteries by removing their negative leads, you would still have 75% capacity remaining at 6 weeks and 50% at the end of 13 weeks. Might go as long at 17 weeks to hit 50% SOC depending on how you calculate it. Worth trying and measuring with a voltmeter to see.

Re: How long store without shore power?

Reply #2 – March 17, 2013, 07:37:41 pm

Quote from: Michael & Jackie – March 17, 2013, 07:13:50 pm

I have not found this though I imagine it is answered within some prior discussion. If a coach must be parked with no shore power available, and you do not want to leave the generator on Auto, then how long can a coach sit and still be cranked and no batteries damaged if the coach is not connected to shore power?

Assume good batteries and that for voltage drains the refrigerator is off, the 12v system is turned off, level system off (I understand the slide bladder air tank is kept filled even with 12v disconnect switch thrown), no heat system is left on.

Perhaps the better option is to leave the generator in Auto but I am hesitant to leave it that way unattended.

Mike

It all has to do with the currant draw and parasitic loads if the batteries are not disconnected.
If you have 2 8d8g batteries at full you have approx 440 amps.
If you dont want to go below 50% you have 220 amps available.
If your currant draw is 5 amps per hour, you have 44 hours. 220/5=44 If you have a 10 amp draw you have 22 hours.

Re: How long store without shore power?

Reply #3 – March 17, 2013, 08:43:59 pm

I'm in the same boat. We brought our coach home last Saturday and haven't been able to plug in. What battery starts the generator? If the rain stops soon I may be able to see about getting at least some power to the coach tomorrow. I don't really like playing around with electricity in the rain, to say nothing of the hail and sleet we had today.

Re: How long store without shore power?

Reply #4 – March 17, 2013, 09:16:13 pm

Mike, Unless your going to leave it setting unattended for weeks or months, I would leave the auto start on and relax, go enjoy your what ever your doing, with everyting turned off, the generator will about 3 hours every 4 days. No panic as I see it, just make sure the fuel tank has plenty fuel.
Enjoy
Dave M

Re: How long store without shore power?

Reply #5 – March 17, 2013, 09:43:38 pm

My 95 sometimes sets for 6 or 7 days without shore power and I have never had a starting problem or a discharge problem. If the weather is really cold I will use the boost switch.
Gary B

Re: How long store without shore power?

Reply #6 – March 17, 2013, 09:46:46 pm

The generator should start from the house batteries

Re: How long store without shore power?

Reply #7 – March 17, 2013, 10:03:47 pm

House batteries start the generator, chassis battery starts the coach, boost switch ties them together

Re: How long store without shore power?

Reply #8 – March 18, 2013, 12:33:46 am

Thanks to all, I think I will leave the gen in auto as Dave says. Am comforted by his advice. Will be at a Cummins shop for about two weeks, in line to get service, no shore power while waiting. Tim, I guess you and I have the same engine. I was told by someone somewhere that it takes a bit more spin rate on the ISM and thus I should always use the boost. Do you do that too?

Re: How long store without shore power?

Reply #9 – March 18, 2013, 08:37:03 am

As for spin rate, I used to use the boost all the time, then:

Went to Cummings and they updated the ECU on the engine - there are several "hard start" updates to the ECU that you may not have in yours.

I have a "trickle start" on my chassis batteries that keeps them charged near 100%. Best if plugged in if you are leaving coach for an extended period.

Make very sure that all the battery connections are clean and tight. For some reason mine have a habit of getting loose over time, sitting or running down the road. Now when it sits any period of time, i tighten the battery connections when I get to the coach (or a couple of days before I plan to leave if I am at the coach. Huge difference. Always find some that can be tightened, not sure why - anybody have any ideas?

If below 40 degrees outside, use electric or aquahot (if not plugged in) to heat engine for at least two hours prior to start.

Spins fast, starts quickly, no problem. You can search for posts about cable modifications from battery to starter on the forum, but I feel no need after these steps.

As for Generator autostart, I love it. However, I stored my previous coach (U-270) for a couple summers at my buddies farm, and left the generator in Auto Start. Worked fine, until it started one day and my buddy called me later that week "hey Tim, your generator has been running four days, is that right"? Seems the controller board had gone bad, it knew how to start the genny, but not how to sit it off any longer. So while leaving in auto start is a good option, best is plugged in, or hopefully someone around to sort of keep an eye on your coach.

Good luck, bet if you do the things I did you will be happier with your spin/start. I used the "boost assist for a long time, don't think it is bad, but I don't see the need any longer.

Re: How long store without shore power?

Reply #10 – March 18, 2013, 02:25:11 pm

thanks Tim, will try without boost, but think I had a warning to not do that? Why would that be, what would it hurt? I did meet a man, very nice but forget his name, who got his to start without boost, which was a signal to me that I had a problem even after I added the wire from batteries to starter, and found it was a starter going out. Rebuilt and wow. Thanks for your time. Mike

Re: How long store without shore power?

Reply #11 – March 18, 2013, 06:25:23 pm

My AMP+ is continuously on so I monitor that for how much is drawn. I typically go 3-4 weeks between starting and driving or charging with the generator.

Re: How long store without shore power?

Reply #12 – March 18, 2013, 06:54:13 pm

Mike, I'm feeling stupid here... but what or where is the 12 vdc disconnect? is that accomplished by the switch at the entry door? Does it shut off Everything 12v or does one have to physically disconnect batteries?
(I have an aftermarket strip up in my TV component area that has a shut off switch. It plugs into the OEM outlet,but has a switch on it that stops all parasitic loads from draining anything to do with TV. Like you, I'd like to be able to know how to save batteries.

Tim, I've been suspect of the quality of castings of battery terminals for many years so thanks for bringing this up. The metalurgy of this cr__ that is our source for these terminals might I suspect be poor. I had found this to be a new and surprisingly more and more common problem in my marine travels. I suspect the main casting of these components but it could also be the bolt itelf.

If my thinking cap is on right, I see no problem with adding the magnitude of both banks for starting even if the voltage of each is slightly different, but it might be wise to once in a while check the standing voltage of each bank separately prior to any Boost Switch connection... Check first, as to how each bank has faired.

Re: How long store without shore power?

Reply #13 – March 18, 2013, 07:23:19 pm

Funny how things get started, my ISM starts very fine on its 3 batteries, but I always use the boost, it gives the warm & fuzzies

Re: How long store without shore power?

Reply #14 – March 18, 2013, 08:08:13 pm

Hey Ron, yes the 12v cutoff switch is in the entry step passage, to the right on the wall as we go up the steps. I find often that coaches even when plugged in have the 12v cut off. I think it is just to be sure all the lights and such are off. It does not impact (turn off) the 12v supply to the refrigerator and does not turn off the small aux air compressor, as I understand it.

I have a feeling that it may leave some voltage to something in the dash, around the radio, that leaves a small drain on the batteries. It turns off more than lights though, such as the back camera/tank monitor. I wonder if it would prohibit turning the generator on though while the 12v disconnect is thrown? It has been suggested so but I have not tried.

As for using the boost, I asked again about that at the service department and was told it good to use it. I did not hear it damaging to not use it.

Cheers, Mike

Re: How long store without shore power?

Reply #15 – March 18, 2013, 08:28:05 pm

The biggest draws with the switch off are the propane safety valve, the gas sensors and the radio memories. I put switches on all and can get the draw down to about 100 to 150 milliamperes.

Re: How long store without shore power?

Reply #16 – March 18, 2013, 09:53:13 pm

I don't see any switch marked "boost" but I do have a momentary one called "override." Is that the same thing?

Re: How long store without shore power?

Reply #17 – March 19, 2013, 12:18:39 pm

Quote

I don't see any switch marked "boost" but I do have a momentary one called "override." Is that the same thing?

No, that "override" is for the DDEC. If the engine computer is forcing an engine shut-down you are supposed to be able to hit that momentary switch and it will allow you more time to get our of a potentially dangerous traffic situation - i.e. at the risk of engine damage.
The boost switch should be on the same panel. Mine is top row second from left. I can't imagine your coach doesn't have it!

Re: How long store without shore power?

Reply #18 – March 19, 2013, 12:50:43 pm

One thing some of you may wish to consider for long term parking withoout shore power is a solar panel.

Trojan indicated 4% loss per week, so two 8D batteries at 450 amphours capacity would loose 18 amphours per week which is about 2.5 amphours per day. My phantom loads are 300 milliamps which amounts to 8 amphours per day. Total amphours lost per day for me is about 10. A 60 watt would provide about 10 amphours per day and could be connected to the batteries without a controller. You could then, turn off your master switch at the door and leave your coach parked indefinitely, as long as the sun shines most days.

With the 850 watts of solar that I have, I do not use shore power when parked on my driveway, unless I have the refer turned on.

For those of you who have higher phantom loads than Dave Head and myself (probably most of you), you could dtermine what your phantom load is and install appropriate wattage of solar panels.

Just my ramblings.

Re: How long store without shore power?

Reply #19 – March 19, 2013, 01:48:33 pm

Mike,
I don't know if you coach is home or in a storage facility. I don't use a storage facility. Mine in plugged to the stick house electrical circuit in the garage. It is a 20 amp circuit and I use a adaptor and my 50 amp cord. Am okay for charging the batteries, lights, etc. Have even ran the AC off of it.

Re: How long store without shore power?

Reply #20 – March 19, 2013, 02:29:43 pm

Before I replaced the dino converter charger I was storing with disconnects thrown on both batteries for about three weeks between an overnight on charger (boost on) and that seemed to work ok. Now with the PD with intellicharge I'm plugged in all the time with the Trik-L-Charge device between the batteries and have no issues. As long as you disconnect the batteries you can go a long time between charges. If they were fully charged and in good condition you might could go a month or more between charges.

Re: How long store without shore power?

Reply #21 – March 19, 2013, 05:20:36 pm

Thanks all for helping.....Pat we have Gus at a Cummins shop and they do not plug in while waiting our turn. After reading the things that were current at the time, I delivered to the shop and turned on Auto for gen and have plenty of diesel. Later I read (Tim maybe posted?) about what can go wrong on that deal (failure of gen control panel) but too late, Gus already gone to service. SO.....I think about Saturday we may run up to see progress, check on the batteries, the generator. Whenever we get in the shop it will have shore power. I may be over worrying this thing, but the analysis someone gave me of thinking in terms of the amps that I have available in the 3 8ds gave me a way to think of time without charging. I turned off the refrigerator, etc. but do not know what the phantom load may be. Got me curious.

Just do not want to go to get the coach one day and find dead or ruined batteries. Very professional folks but I do not think a FT motorhome is all that familiar to them. At least they asked good questions. And they liked the engine access of the FT.

As an aside, got to meet Dean and Dee today and tour their coach. Couple almost as nice as their coach! Reminds me how I miss the 36 ft coach that we had before this one (sorry Gus, it was a really good size for us.). Mike

Re: How long store without shore power?

Reply #22 – March 19, 2013, 05:34:17 pm

Found the boost switch right where it is supposed to be.

When I brought our coach home I didn't think much about plugging in, so I didn't get close enough. Yesterday I tried to stretch cords, but not long enough, so I tried starting. No start. Last night I remembered that I have a 15,000 watt generator, so I charged the battery overnight, and today Jo Ann and I got it out by the coach. Fired right up, so I plugged the coach in and turned on the block heater. In a few minutes I'll go out and see if I can start the engine. If so, I'll move the coach up to where I can plug in. The ground is still too soft to try to actually get it where it needs to be, but at least I'll have things charged and power on so that if we need to move to the coach we can. Blizzard may (or may not) be coming Thursday. The generator can power the house, including the well, so we'll actually go that way before going to the coach, unless we just want to try it. Haven't cat-proofed it yet, though.

Worked perfectly. Engine started right up, air pressure built quickly, and I was able to get close enough to plug into the 30A outlet. I think it will be pretty easy to back into the parking place once the ground is drier.

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