Chassis/House Battery Charging 4 Motorhomes

[Jim Tyrney]

When the 86 345 is plugged in to shore power, does the Univolt only charge the coach batteries and not the start battery? I think that is the way it works thru reading threads, manuals, voltmeter, etc, Is it possible to charge start battery with Univolt if it is not set up to do this? When on shore power, I checked isolator and 13.6 VDC @ top connection (coach batteries), 0 VDC @ center connection and 12.2 VDC @ bottom connection (start battery). I believe this should be correct. Thanks for any replies/help. Jim

[PeterH-350LE]

you got it right, Jim.
The univolt only charges the coach batteries.
Your voltage reading at the isolator indicates it's properly functioning.
The motor battery gets charged from the alternator and the generator when running.

[Jim Tyrney]

Whew!!!! I was hoping that was correct. My start battery had dopped charge over couple weeks or so and had not driven, working on odds/ends. I will check a little deeper for reason to discharge. all batteries are setting on metal bottom of pan and think should have some type of isolation. Could be reason for discharge but may have leakage in some circuit. Thanks for the reply. Jim

[uncleneal]

Jim, I've had a 310 and 345. On both of them the the starting battery would go dead when it sat. Seems to be characteristic of most motorhomes, not just Airstreams. One way to prevent it is to disconnect the starting battery when it sits. I kept a plastic bag in the battery box of the 345 to put over the pos terminal when I pulled it off the battery. (If you use the booster switch to start off the house batteries with the starting battery cable off, it will be hot) Another alternative I've used is to get a little trickle charger for the starting battery and use it enough to keep the battery up. You can hook it to the battery, or you can open the hood and clip it on to the starting battery terminal of the isolator. You can tell which one that is by disconnecting the battery and see which one is dead. Unless all three batteries are identical (age, capacity, condition etc) they won't charge properly if they are jumped together for the univolt to charge.
A lot of the big motorhomes like the Bluebird that a previous employer had, have one set of batteries to do everything. Seems like an Airstream could be rewired for that. You would just have to be careful when dry camping not to run them all down. If you had a toad you would have a source of a jump start.
I wonder if it is possible that the isolator has enough phantom load to kill the battery? That's the only thing that stays hooked up on a mh that a regular truck doesn't have. I know that you have a voltage drop thru them, so they use some power.
Neal

[87MH]

Jim:

Check the age of the start battery, it just may be that "Its time is up".

Things that I usually check:

Hydraulic system (make sure switch on floor is "off").

Various light switches (glove compartment, engine bay, etc.)


In addition;

There was a significant amount of corrossion on almost all of the contacts and terminals on my unit. This is to be expected in a vehicle 17+ years old. I took a day, disconnected a bunch of the terminals and contacts, and brushed them clean. Not sure if I got all of them or not, but most had a goodly amount of "crap" on the terminals and stud connectors.

[swebster]

Jim,
I'm also getting many things resolved by cleaning grounds. Also, things like the radio clock, bedroom clock, etc. are usually still "on" even when you turn "off" the coach.

The PO installed two marine battery disconnects in the battery compartment in my 345 (you can get them from West Marine ). If I leave her for more than a week I'll disconnect the batteries completely.

I also like the idea that if someone wanted to try and steal my coach they would have to figure out where the batteries are and break two locks on the battery locker to get at them. (unless they travelled with a battery)

[ALANSD]

Steve- the disconnect is a good idea, my 280 came with one as well. I also have the blade switches that disconnect the individual coach batteries.
Unfortunately leaving mine plugged in too long killed them anyway. This prior to me learning the correct care fro them.

[Jim Tyrney]

I really appreciate all the feed back on the batteries, both the coach and start batteries. After I finally got the MH started (had to put charger on start battery, it was so low, that it would even pull down the coach batteries), took short trip and start battery is now up to "snuff". When I switched to coach batteries with monetary contact switch, the lever broke off so I had to pull dash loose and replace( not too bad a job, easily reached). It seems like it is time to replace the coach batteries due to will not hold charge and I checked to ensure they were getting charge voltage( 13.4 VDC with digital Fluke meter). Have ya'll found any paticular batteries that seem to hold up better than others? A little info about my first trip from Louisiana to Tennessee. On the way up, had a flat on drivers side rear tag axle that really destroyed itself, bent area were flap was attached to inside of wheel well, broke off grey water dump vale extension,bracket & missing and cap on outlet went also. No jack so luckily had AAA RV Plus and changed to spare after 2 hour set on interstate. All went well until last day before returning when Onan started hunting when started that AM ( still working that one). On the way home in Alabama after short stopat a resturant, came out to a completely flat passenger side rear tag axle flat, lost all the air and could not get to hold air due to tire seperation from rim. Another call to AAA RV Plus, wrecker service got it aired up and could not find any leaks( still holding as of today). Very eventful trip!!!! I checked in manual and it said that rear tires should have 60# and front tires should have 70#. Wrecker service said most RV's running 90 to 100#. How much are you guys running? Sorry for the length of reply but thought ya'll may be interested in my first trip. Jim

[TexasStars]

Had the same problem Jim after sitting for several weeks without use, it's the first time my batteries have discharged and need to start and run gen. and engine at least this often....lesson learned.

[87MH]

Jim:

You may want to check the age of your tires. There is a code on the side of the tires that will indicate the build dates.

I believe that most of the Forum will recommend tire replacement after 5 years, regardless of remaining tread.

On the Onan - have been experiencing similar dificulties. I rebuilt the carburetor, but only got a few hours of good time out of it. I have purchased a new Nikki carb (only 140 bucks), and hopefully will have it installed this weekend.

[87MH]

Michelin recommends 70 to 90 psi in the 8R19.5's, high side for their 225 X 19.5 tires varies from 85 to 95 psi max, and allowable load is dependent on pressure.

You might want to get an actual weight on your unit and get a recommendation from the manufacturer of your particular tire.

AccessMaster, a forum member, presented an excellent dissertation on proper inflation here:

http://www.airforums.com/forum...&threadid=4300

and here:

http://www.airforums.com/forum...&threadid=4519

[ALANSD]

I have since found that keeping my batteries disconnected with the aid of the blade switch had really improved thier life. I also use a small charger as necessary to top them if, but they rarely drop in voltage much.
It does mean you lose your radio memory.

[guy99]

Alan,
Thanks for the pointer to this thread. The only outstanding question I have is whether the Chassis (starter) battery should be charged by the genset? My MH has a water cooled Honda installed by the PO. When the genset is running the house batteries are charged, but not the chassis battery.

When the genset is running is it charging the batteries via the converter or through some other circuit?

[noiva]

General question for anyone about disconnecting the batteries on the MH when not in use. I've trailered for over 30 years and have always left my trailer plugged into shore current when not in use. The trailers have had converter/chargers just like the one that was installed in my "new" 370LE several years ago. It charges at a constant 13.8 volts when plugged into shore power, charging BOTH sets of batteries. I've never had any problems with the batteries in the trailers, but would like to know if I need to start disconnecting the MH batteries, and what the advantage might be. I've not had the MH long enough to have experience with this particular issue. Anyone with an experienced opinion? I'll be happy to do the disconnect if there's an electrical benefit.

Thanks,

Noiva (Tim)

[ALANSD]

when i first got my Moho I left it plugged int shore power thinking I was doing myself a favor by saving battery life. It fried both fairly new GM Delcos in a short time. I replced with an inexpensive Wal Mart chassis battery and a more expensive yellow top house one, used the disconnect blade, and I have not had a problem since. I check the charge level every week or so, and plug in when it drops below fully charged if not driving the coach.

[noiva]

Thanks for the info. I'm going out to cut mine off right now. Must be something different with the MH setup. My "new" 370 has 3 very good and almost new batteries. I certainly don't want to cook them. I've always used just cheap batteries in my trailers, but I have noticed that the electrics of the house battery system are far superior on the Airstream than I've ever experienced with any trailer. Do you meter yours with one of those digital plug-in meters, or just check each at the battery with a mulitimeter?

Noiva (Tim)

[Chuckles]

Just to throw a “spanner-in-the-works”, I recently lost the generator - it died in a cloud of smoke and flame - probably a simple thing like bushes. However it gave me the excuse to get rid of the genny. (I hate generators with a passion - noisy smelly etc..) The only time I can see using it is for the AC and that wont happen too often here in the UK! I would rather sit out side under the awning than in a “cocoon” watching the world go by….any way I digress…

The space it left gave me the opportunity to fit in two more 110Amp/Hr Batteries, the 240VAC distribution panel, a 3kWatt Inverter (12vdc to 115vac) and a battery charger. It also rendered the Univolt surplus to requirements.

But! What a difference..... The voltage now from the house batteries increased by as much as 1.1 - 1.2 vdc. From this I can only assume that either the Univolt doesn’t have any blocking diodes or that they were not working.

So if the house batteries do lose power, remove the house battery positive connection from the fuse panel and check for any current loss between the cable and the connection.

Hope this helps

Chuck
Dorset UK

PS. Any UK members going to any shows in the UK this year?

PPS. I have a local chap who has made me the graphics (Wave) for the spare wheel cover; it’s a beauty (also smaller ones for the wheel hubs) – photos to follow when fitted. Also we may be able to make up new covers in GRP.

[noiva]

[quote=Chuckles]Just to throw a “spanner-in-the-works”, I recently lost the generator - it died in a cloud of smoke and flame - probably a simple thing like bushes. However it gave me the excuse to get rid of the genny. (I hate generators with a passion - noisy smelly etc..) The only time I can see using it is for the AC and that wont happen too often here in the UK! I would rather sit out side under the awning than in a “cocoon” watching the world go by….any way I digress…

The space it left gave me the opportunity to fit in two more 110Amp/Hr Batteries, the 240VAC distribution panel, a 3kWatt Inverter (12vdc to 115vac) and a battery charger. It also rendered the Univolt surplus to requirements.

But! What a difference..... The voltage now from the house batteries increased by as much as 1.1 - 1.2 vdc. From this I can only assume that either the Univolt doesn’t have any blocking diodes or that they were not working.

So if the house batteries do lose power, remove the house battery positive connection from the fuse panel and check for any current loss between the cable and the connection.

Hope this helps

Chuck
Dorset UK]

Chuck,

As this is the first motorhome I've owned, and all my previous vehicles were trailers, this is also my first experience with generators. I have always thought-as you-that they were noisy, smelly, and totally unnecessary. Sounds like you have greatly improved your setup with the death of your gen. (What's the 240VAC distribution panel for? Does it have to do with the European use of 240 vs 120 in the USA?) However, since I live in Virginia, traveling without AC can be very difficult. With the trailers, I was traveling in an air-conditioned tow vehicle. With the MoHo I've learned it's usually impossible to get enough cooling from the dash AC, and the forward roof air unit has become almost a necessity on the highway. For that reason, if for no other, I have seen the need of the generator. I use mine only on the highway in hot weather. I try to never use it in a campground unless I'm without electrical hookup and the batteries need a boost to keep the 12v up. Then I just run it for short periods as needed.

Since this is the first MoHo I've owned, I'm still learning all the time. I'm experimenting this winter with leaving the MoHo plugged into my garage current (120v). I check the batteries at least monthly, and take the MoHo out for about an hour drive once a month. So far, so good. I think if I ever have to leave it unplugged for any length of time, I'll disconnect the batteries since I see no way to stop the constant "trickle" leaks that are inherent in an electrical system like a recreational vehicle. I'll likely install the disconnect blades as have been discussed on this thread if I run into that situation.

Just as an aside, we have friends in Lightwater Surrey, southeast of London. They came here in 1993 and spent two weeks. They stayed in our trailer in our back yard. We had a great time. The lady was my wife's 6th grade "pen pal", we had never seen each other before, and by the time they left we all felt like old friends.

Best,

[ralley]

In general, the main reason that us folk are having problems with our batteries is that the charging systems in the older AS MH's are, shall we say, POO. (ask your dog, if you don't understand!) The problems, without being technical, are:

1. There is insufficient capacity in the battery banks supplied, causing the "deep cycle" batteries to cycle through a very wide range of state of charge (50% or more) during use. This causes the batteries to fail prematurely--usually because the plates in the battery "clog up" (highly technical term here) and are never "equalized" to "unclog" them.

2. The normal charging cycles in our systems are too primitive to take advantage of the best currently available battery technology today. My 350 has an energenius (ca. 1991) which is a two stage charger without (as nearly as I can tell--there was no technical info with it) any charge sensing or temperature compensating capabilities. Left to its own devices, it will charge batteries until they fry themselves.

Our UK friend is on the right track. The proper answer is to double (or more) the Amp Hour capacities of our battery systems (so they cycle, on the whole, to something like 20-25% of capacity instead of 50-80%) and use a best quality battery charging system which is designed to properly charge AND maintain these bigger battery systems.

Example: My 350 was designed to have 2 series 27 deep cycle house batteries, or ABOUT a total Amp Hour capacity of 210 AH. If I am really careful when off the grid, we use about 70-80 AH in 24 hours for all purposes. That's about 40% of capaqcity. At that cycle rate, 40% per day, and without any further action on my part, the charger must replace 80 per cent of my capacity every two days. The charge cycle might be, say, 6 amps, which means it will take more than 12 hours just to bring my battery voltage back up to what my system thinks is a full charge (it won't be, but nevermind.)
That's a lot of generator time!

Bottom Line:

A deeper, larger battery box should be fitted to allow the AH capacity usage to be no more than 20-25% of total capacity, and you should replace the stock charging system in your AS with the best available today. Over the life of your vehicle, it will pay you every day.

PS I don't work for anyone that makes this stuff, and never will.

Rob Alley

[Pat370]

The 370LE MH system is not the same as all other models.
On all 370's came standard with a inverter charger not a
converter charger like on trailers. When pluged into shore
power the inverter charges only the house batteries. The
starting battery starts the engine and the Onan generator.
When the Onan plant is running the house batteries are
charged with the inverter and the start battery is charged
with the DC charge system from the Onan plant. The only
you can charge the start battery when pluged into shore
power is to use one small jump cable from the positive post on the house battery to the positive post on the start
battery or use a small AC battery charger. Pat370