House Batteries

[rogjoan]

I have a 2003 Adveturer 33v. When the motor is running does the alternator charges the house batteries? If not how can that be fix? Thanks for an early reply

[Wetboy5776]

Yes, all motor homes today charge both the engine battery, and the house batteries. With your unit, yo should have what is called an isolator after the alternator. This piece of equipment determines how much charge is needed for each type of battery and delivers the appropriate charge.

The isolator also separates the batteries so if you run one down, usually the house battery, you can still start the engine. Old RVs like mine (1985) had a very simple mechanical type of isolator. The newer, larger coaches usually come with electronic ones.

If your coach battery is not charging with a good hour plus run down the road, then the problem is either the battery, or the isolator. Both can be tested. If the battery in your 2003 is the original, I'd put my $$ on the battery. Even well taken care of batteries don't usually make it past 5 years in an RV application.

Hope that helps...

[justimagination]

Yes............the house batteries are hooked in series with the starting battery, or @ least they should be, and anytime the engine is running, the alternator charges all of the batteries. You may also have a small solar panel on the roof which supplies some charge while parked. Hope this info helps, good luck, happy trails & travel safe.
David G.

[georgetown350]

House batteries have to take a number and get in line as the alternator takes care of the chassis batteries first. Its the other way around when plugged into shore power or running the genny. Note that not all motorhome chassis batteries receive a charge from shore power.

[rogjoan]

The house batteries are new june 2010. All cell check o.k. When I check them with the volt meter and the motor running I get no incoming voltage. Even after a long drive my house batteries are still low after a weekend out with no shore power. I have to recharge them with a charger. Coach batterie alway full charge. Will look for the location of the insolator. What should I be looking for and can it be check Thanks

[Wetboy5776]

Yeah, definitely sounds like an isolator issue. The original ones that come from the manufacturers are pretty cheap. If you have an mechanical one, they work like this:

The alternator begins charging the chassis battery, and once the battery is charged to a pre-set voltage level, a contact will cross over inside the isolator and now routes the power from the alternator to the coach batteries.

The problem with this is, often the chassis is using enough power from all it's systems ( AC, lights, engine coil, etc.), that the voltage limit to crossover is never reached. The alternator can lose output power over time, so that further exacerbates the problem. You wouldn't notice if you were only running chassis systems but once you add the demand for coach battery charging, and a 12 volt fridge...it becomes apparent.

This happened in my lil 21ft toyota RV that only came with the factory 30 amp alternator. Once I replaced it with a powerful 160 amp specialty alternator it improved greatly.

OK, so lets assume you have a powerful alternator AND it is cranking it's full output. The next likely issue is the isolator itself. Mechanical isolators are basically the same solenoids they were putting in cars 50 years ago. They go bad easily, but they are cheap, so are usually whats installed. There is an electromagnet inside that when energized mechanically pulls the little contact to one side or another, thereby deciding which battery will receive the charge. Eventually with all that sliding back and forth, the contact goes bad.

With a 33 ft modern coach, I would highly suggest you go, as I did, with a solid state isolator. These are basically two big diodes, placed in a big aluminum heat sink. A diode is just a one way valve. It allows electricity to flow one way only. It keeps the chassis battery juice from being used by the coach, and vice versa.

There are no moving parts, but they do get warm as there is some resistance the more amps you push through them. They need to be located in a place that is relatively cool, they don't like being in a hot engine compartment. My 200 amp isolator, which may often have to handle 140 amps coming from the Alt, had to be moved behind my driver's seat inside the cab. I imagine in a big coach, there are more places to mount it.

Now, here's the catch with Solid State isolators. They eat some of your voltage. About half to 1 volt in some cases. It's called voltage drop, and most mnfctrs list what the voltage drop is. The problem with this is, if you have a marginal alternator already that puts out say 13.8 volts, you may be down in the upper 12s or low 13s for charging. This will severely limit your charging. You either need to get a pricier isolator with little drop, or upgrade the alternator to one that puts out 14.7 volts. That's what my Powermaster Alt puts out.

I have a huge coach battery bank that can take hours on the road to charge if severely run down. So I wired the alternator output directly to the coach battery, so it reads THAT voltage to determine how much power to put out. My chassis battery then goes through one of the diodes with the resultant voltage drop, but it is still more than enough to run everything. However, my coach batteries get the full charge from the Alt with no voltage drop, as the other diode just sits there unused.

Took me a while to think through this arrangement, and I doubted myself that it could be so easy, but it has worked for thousands of miles! The upshot to this arrangement is, you still get battery isolation but you can use a much smaller (cheaper) isolator.

I bought a 200 amp isolator knowing alot of current would be going into my coach pack. But my chassis system, even with everything running, probably never takes more than 30 amps. Unless I let that battery run down, and it needs to really pull the amps to charge up.

So basically, if I were you...I'd have the alternator checked UNDER LOAD to make sure it is putting out full power and voltage. Then, follow the output line from the Alt and it will lead straight to the isolator. Then you can check those. Most likely that's your problem if the Alt is good. Solutions to that problem are prescribed above...

[scotts_rv]

Originally Posted by rogjoan

The house batteries are new june 2010. All cell check o.k. When I check them with the volt meter and the motor running I get no incoming voltage. Even after a long drive my house batteries are still low after a weekend out with no shore power. I have to recharge them with a charger. Coach batterie alway full charge. Will look for the location of the insolator. What should I be looking for and can it be check Thanks

rogjoan,

I was exactly where you were at this last winter but mine was intermittent. If your alternator is charging your chassis then there is nothing wrong with it. It can only be the isolator/solenoid which parallels the house and chassis battery together when you run the motor and also when you push the battery boost switch on the dash. It is located just above the battery compartment behind a hidden panel (mine has carpet on it). After taking off the panel you will see a metal panel that has two latches on the left and right. Take this off and you will see some circuit breakers. The solenoid is behind this. Since a picture is worth a thousand words I have attached pictures. The first is after you remove the circuit breaker panel. The second is a close up of the solenoid you need to replace. Here's a link from Winnebago of your electronics for the breaker compartment and solenoid.

http://www.winnebagoind.com/diagram/...ire_141254.pdf


The right stud on the solenoid comes from the chassis battery and the left stud goes to the house batteries. The center stud is what triggers the solenoid (You might want to check and see if your getting 12v or more on this when the motor is running). Your part is the same as mine. Winnie part number 8188-01-000 which is a Trombetta part# 936-1215-011-21. I got mine from lichtsinns, a sponsor on this web site. Very nice and well informed people. Be ready to give them the Winnebago serial number to your RV. It was about $30 shipped to my door. My local dealer wanted $45 plus tax and I had to drive 15 miles to go get it!

All you need is a large philips screw driver to get the solenoid off and a socket wrench to remove the wires. I took the pictures to make sure I new how to put it all back together! Make sure you have both the chassis battery and house batteries disconnected (remove the grounds leads from them).

This seems to be a common problem on Winnebago's which you can find by searching on "solenoid" on this forum. You will see that others have come up with a more robust solution. I took the easiest route by just replacing it. I hope it lasts longer than the original.

-Scott

[bachler]

On the last 3 motorhomes the engine DID NOT charge the coach batteries, Our present one an Ultimate The engine charger does not charge the house batteries;; I do not want to discredit any one. However the statement that the engine charges all batteries should not be made. then followed with the statement (some manufactures are cheap) This type of talk, should NOT be made. Some do ,some don't OK. if yours don't,and You want yours to charge INstall a diode, Some install a solenoid, That is a manual fix and not reccomended for extended uses. Those that dissagree complain about solenoid failure.. Life is so good;;

[Paul R. Haller]

Originally Posted by bachler

On the last 3 motorhomes the engine DID NOT charge the coach batteries, Our present one an Ultimate The engine charger does not charge the house batteries;; I do not want to discredit any one. However the statement that the engine charges all batteries should not be made. then followed with the statement (some manufactures are cheap) This type of talk, should NOT be made. Some do ,some don't OK. if yours don't,and You want yours to charge INstall a diode, Some install a solenoid, That is a manual fix and not reccomended for extended uses. Those that dissagree complain about solenoid failure.. Life is so good;;

I am prepared to take issue with this statement. All motorhomes should charge both sets of batteries and if they don't, don't buy that brand of motorhome. RV manufacturers are notorious for finding any way to save 1 penny as evidenced by d rated tires on a trailer that weighs 15,000 lbs and 6000 lbs axles under the same trailer. Oh I know many will say you have 20 % of the weightof the 5er is on the truck but you still have to stop all that weight. See what happens to a d rated tire carrying beyond its rated load rating when you hit a pot hole at 60. I'm sorry but when they go to that lengh to increase their profits by endangering my family, and everone elses on the road, that is simply negligence. For all you out there in RV land, do your homework and vote with your checkbook. You are to blame with letting manufaturers get away with things like this. Yes, you by being an uninformed buyer. you do not have to lay down a take it! Fight back. Fight back by buying the manufacturers who really are doing the right things.
-Paul R. Haller-

[scotts_rv]

Originally Posted by bachler

On the last 3 motorhomes the engine DID NOT charge the coach batteries, Our present one an Ultimate The engine charger does not charge the house batteries;; I do not want to discredit any one. However the statement that the engine charges all batteries should not be made. then followed with the statement (some manufactures are cheap) This type of talk, should NOT be made. Some do ,some don't OK. if yours don't,and You want yours to charge INstall a diode, Some install a solenoid, That is a manual fix and not reccomended for extended uses. Those that dissagree complain about solenoid failure.. Life is so good;;

Bachler,

I'm more than a little surprised at your comment. I can't tell from your profile what year your Ultimate is but I looked at Winnebago's drawings for 1999 to 2003 for which they had a 38' and they all look to have a battery isolator solenoid. Is yours an older model?...or maybe it's just not working like rogjoans

You can tell if it came from the factory with one by looking at Winnebago's drawings:

Wiring Diagrams

Select year and your model then select the Body 12V wiring diagrams, automotive wiring diagram or Chassis electrical box assembly if it has one for your year.

-Scott

[John Hilley]

With most motorhomes using battery isolation solenoids there is no voltage sensing, the solenoid closes when the engine starts, some times there is a delay, but that requires more than the isolation solenoid. For full charging an isolation solenoid is preferable to diodes as there is a voltage drop across the diode reducing the charging voltage to the coach batteries. The voltage drop on silicon power diodes is .7 volts.

[bachler]

Originally Posted by bachler

On the last 3 motorhomes the engine DID NOT charge the coach batteries, Our present one an Ultimate The engine charger does not charge the house batteries;; I do not want to discredit any one. However the statement that the engine charges all batteries should not be made. then followed with the statement (some manufactures are cheap) This type of talk, should NOT be made. Some do ,some don't OK. if yours don't,and You want yours to charge INstall a diode, Some install a solenoid, That is a manual fix and not reccomended for extended uses. Those that dissagree complain about solenoid failure.. Life is so good;;

Most of them Do have a solenoid; That is Not an isolater OR diode. . I do not want to get into a stupid , mine is better then yours; Not all motorhome engines charge the house batteries. Unless dash switch is triped. And held in position.. After all I have only been repairing them Since My 1958 apprenticeship;; Now some do and some don't. Let It rest .boys.

[scotts_rv]

The link below clearly illustrates the different kinds of battery isolators and how they work. They are meant to "isolate" one battery from the other.

battery isolators

Peace.

-Scott

[John Hilley]

Originally Posted by scotts_rv

The link below clearly illustrates the different kinds of battery isolators and how they work. They are meant to "isolate" one battery from the other.

battery isolators

Peace.

-Scott

This is a good reference, but is meant for a vehicle with a large audio system or winch. On a motor home the ignition and accessories are connected to the chassis battery. Some higher end coaches have a BIRD Relay Control.

[RJay]

If you find that the alternator is not charging the chassis batteries because it's a feature not included on you motorhome then you may need one of these. I had a 2000 Itasca that didn't charge the start battery when connected to shore power.

[scotts_rv]

Originally Posted by John Hilley

This is a good reference, but is meant for a vehicle with a large audio system or winch. On a motor home the ignition and accessories are connected to the chassis battery. Some higher end coaches have a BIRD Relay Control.

Agreed that it's a little simplified but explains the basic differences in isolator types I was considering installing a BIRD relay but decided that's not for me since my RV unfortunately sits at a storage lot without any power most of the time. Solar power was the only way to go for me.

It looks like the BIRD will have some parasitic draw off the coach batteries while not plugged in or running the motor, even with the coach and chassis disconnects activated based on the diagram in your link. That might mean dead batteries if your RV hibernates over the winter like mine.

Thanks.
-Scott

[rogjoan]

The insolator was right at the place indicated where Scotts_rv said. Went out bought a new one for $22.00 replaced it and now the coach battery are being charged when the motor in running. Thanks for the help it sure was appreciated and saved me $$$$.

[Wetboy5776]

Originally Posted by bachler

Most of them Do have a solenoid; That is Not an isolater OR diode. . I do not want to get into a stupid , mine is better then yours; Not all motorhome engines charge the house batteries. Unless dash switch is triped. And held in position.. After all I have only been repairing them Since My 1958 apprenticeship;; Now some do and some don't. Let It rest .boys.

Alright, I was going to stay out of the sillier arguments...but now I have to jump in! Bachler, you are just wrong. This is not a "mine is better than yours argument", it is simply how things are.

Every major coach mnfctr that installs a set of coach batteries, will have installed a way to charge them. Think about it. Are the coach batteries only to be charged when you are hooked up to shore power or a Gen? That's ridiculous! What would be the point of having coach batteries then?

I think some of your confusion is in the terminology. You said most of them "have a solenoid, but not an isolator". It's the same thing, for battery charging purposes. The solenoid is technically the little sliding contact INSIDE the isolator, but they are often used interchangeably.

If you had to hold down a momentary switch on the dash to get your batteries to charge, that was some kind of a rigged job by a previous owner. I've seen tons of them, even MY system is technically "rigged". (Albeit better than new). But at some point, these coaches were designed to charge both batteries. Either that, or you are still working on coaches from 1958. Maybe I'm not understanding you correctly.

If the system is operating CORRECTLY, the isolator, depending on type, will feed power to one or both of the batteries as needed. My preference is for the solid state (diode based) type... wired as I stated in my previous post. But a solenoid type can work, just not as efficiently IMHO. If the solenoid type that usually comes with most coaches is NOT charging the coach battery after long trips, then it's time to find the problem. Not just give up and say, "Well, guess it wasn't designed to be charged!"

It's ridiculous to say that any modern coach mnfctr is putting out systems that are not designed to charge the coach pack. And the rig that was originally the subject of this thread, DEFINITELY was a newer system that is supposed to charge both batteries. That's why rogjoan was able to fix it quickly and cheaply with the help of those of us who know what we are talking about.

Since you claim to be an expert, please give me specific model and year of a coach that does include coach batteries, but no way to charge them, and I'll stand corrected. Otherwise, I'll stand by my previous post.

[movin-on]

I would think that your house batteries would get pretty low fast if they were not being charged with the engine running especially driving 8 to 10 hours a day and the potential loads...Refrigerator control board...detectors..water pump..furnace etc..all run off the house batteries...

[Wetboy5776]

Originally Posted by movin-on

I would think that your house batteries would get pretty low fast if they were not being charged with the engine running especially driving 8 to 10 hours a day and the potential loads...Refrigerator control board...detectors..water pump..furnace etc..all run off the house batteries...

Exactly. As a guy who full-times out in the boondocks with only a solar panel, a wind gen, and a BIG alternator...I can tell you those little loads add up fast! But I assure you, every coach builder out there, even the one who built my little 1985 Toyota MH, includes an isolator to charge the coach battery. Some are just better than others.

But alot of it depends on how you use your RV. If you mainly drive from park to park, you will probably never notice that your isolator is shot, unless it stops charging your chassis battery.

I got everything hooked up to amp and voltmeters, so I can tell quickly if there is a problem somewhere in my system. But I'm just a techno nerd like that... :-)