Bad Alternator or Bad Batteries?

[distaff]

Originally Posted by ereadingrv

When I wrote the original post, I accidentally omitted the fact that the coach is run and moved every one to two weeks. That was my error; but the sarcasm by TeJay, rather than simply asking if we moved the coach (as you did) was uncalled for. Thank you for asking; and I have clarified that yes, as I said, we do move the coach and travel in it. Thank you.

Ok. Not unusual for a coach to have a phantom draw, but you should see some consistency - the batteries should lose charge at a consistent rate over time. Fairly easy to check what is going on:

1. Use a multi meter and check your voltage on the chassis batteries, even fully charged new batteries will sit at or under 13v.
2. Start the engine and check the voltage with the engine running, if you don't see the voltage up near 14v or slightly above, wait at least a few minutes and check again since some coaches have a delay built in.
3. A working alternator should put out about 14v.
4. If you are seeing a healthy charging voltage the problem is elsewhere, there are cheap testers you can buy to test the electrolyte in your batteries. I use a refractometer that can you use to check batteries or coolant, but they are more expensive. You can get a battery tester at any autoparts place.
5. A real test of your starter batteries requires load testing them, this is usually done at a place that sells batteries and takes about a minute. It can be done with the batteries in place. A load test is called for when you see a healthy voltage on the batter (above 12) but it doesn't have enough power to crank the engine - meaning you are getting a surface charge but the batteries are sulfated.
6. No matter what, travel with a battery charger, I also care 20 foot heavy duty jumper cables. When boon-docking you want to unplug the charger when you are running off the house batteries, which can be annoying.
7. Add a battery cut off switch to both banks of batteries (do it on the negative terminal) and cut off the chassis batteries when you park (this does mean you lose the dash radio).
8. If you want to get fancy, add a solar panel and a controller, it can keep your batteries charged even with a draw.

[RobRoy]

Originally Posted by ereadingrv

Thanks for the advice. Question: is there a different process for checking the battery than just the voltage? In other words, is there some kind of indicator or other factor, besides voltage, that would point to whether the battery is bad versus just discharged?

Yes...but to so you would need something that reads the circuit amperage output when running of the alternator to your suspect battery.

If the battery is discharged but yet strong enough to start your vehicle or you jump start your vehicle, what you should see at first is lower than normal voltage output readings and higher than normal amperage readings and if the alternator is good and the batteries are good you will see both these numbers head the opposite direction in short order ...meaning once started and if all is well you will see the charging voltage start to rise as the amperage output start to go down.

Constant alternator high amperage output to your batteries with no loads on the system is a dead give away the batteries are headed south.

The above all somewhat mumbo Jumbo at this point.

1. As stated you need to have your batteries tested properly.

2. You need to know that your charging system is functioning correctly when the coach is running ...and as stated 1vdc over open circuit battery voltage should suffice.

3. Are the chassis batteries being charged when the coach is plugged in and not running?

4. Are the chassis batteries being charged when the genny is running?

On my coach it charges both the chassis and house batteries ...as stated by others already, many coach's do not ....so your fix may be a simple as needing to add a inexpensive smart charger Bada-boom! Bada-bing! job done.

Happy Hunting

[nothermark]

Mostly because I don't want to be part of "all". I would not waste my time getting the batteries tested. I know a lot of folks seem to like the idea but I see it as potential battery damage from the high load current used in the tester. I'm not sure the results are that useful.

Either they start the unit or they do not. If they have enough charge to start the unit that is all that is needed. With a MH there is always the magic button to add the house batteries to the mix in case of a soft engine battery. If I know the engine batteries are getting charged when parked, hence the Trik L Start or equivalent, than needing to use the boost button twice would have me at the battery store. I said twice because I would be checking the charge condition before the second attempt. If it was full charged then the batteries are toast. If not there is another problem to fix.

[RobRoy]

Dont test the batteries .........that's O.K.


But keep this is mind when not doing so ....YOUR BATTERIES TELL YOUR CHARGING SYSTEM WHAT TO DO.


So with marginal batteries your charging system... ie: your very pricey ALTERNATOR.... is killing itself trying to keep up with your marginal batteries that you don't want to test.


Think not?

Check the ALTERNATOR charging rate amperage OUTPUT on marginal batteries as compared to good ones ....you can flat out see the difference ..big time.

Load testing good batteries does not harm them ....if they fail they were junk to start with.

Trying to keep your steed going with marginal batteries is killing your alternator.......no if and or butts about it.

Batteries cost $129.99

Alternator min $329.99 plus labor ...and it wont fail until you on the side of the road at midnight ta boot.

Happy Hunting

[twinboat]

A battery load test draws about 100 amps max, for 10 seconds.

A diesel starting motor will draw 200 to 300 amps for 10 seconds or more.
More then that on a cold day. Just look at the size of the cables !!

No harm in testing start batteries.

[Monacoach]

The batteries are old. There testing days are over. The only fix for old batteries is to get new batteries. Then you can start testing things with the elimination of a battery problem. Different story if they were newer batteries of course.

[twinboat]

The batteries are old ? Just replace them ? How old is old for batteries ? Did the OP state the age ?

I believe they've only had the MH for 2, maybe 3 years.

Just blindly changing parts is not how you fix things.
Step #1 of reparing something is to troubleshoot to find the problem.

If the problem rears its ugly head 6 months down the road, do you replace them again ?
Or shrug your shoulders and think, guess it wasn't that.

The OP had already dumped a bunch of money on repairs to a bad engine that ultimately needed to be replaced anyway.

It probably is the batteries, but you need to return them anyway. Why not spend 2 minutes having the guy throw a FREE load test on them. Then you know its at least part of the problem.

It's that simple, folks.

[RobRoy]

Originally Posted by twinboat

The batteries are old ? Just replace them ? How old is old for batteries ? Did the OP state the age ?

I believe they've only had the MH for 2, maybe 3 years.

Just blindly changing parts is not how you fix things.
Step #1 of reparing something is to troubleshoot to find the problem.

If the problem rears its ugly head 6 months down the road, do you replace them again ?
Or shrug your shoulders and think, guess it wasn't that.

The OP had already dumped a bunch of money on repairs to a bad engine that ultimately needed to be replaced anyway.

It probably is the batteries, but you need to return them anyway. Why not spend 2 minutes having the guy throw a FREE load test on them. Then you know its at least part of the problem.

It's that simple, folks.

Thank you!

[Unplanned Tourist]

Originally Posted by twinboat

The batteries are old ? Just replace them ? How old is old for batteries ? Did the OP state the age ?

I believe they've only had the MH for 2, maybe 3 years.

Just blindly changing parts is not how you fix things.
Step #1 of reparing something is to troubleshoot to find the problem.

If the problem rears its ugly head 6 months down the road, do you replace them again ?
Or shrug your shoulders and think, guess it wasn't that.

The OP had already dumped a bunch of money on repairs to a bad engine that ultimately needed to be replaced anyway.

It probably is the batteries, but you need to return them anyway. Why not spend 2 minutes having the guy throw a FREE load test on them. Then you know its at least part of the problem.

It's that simple, folks.

I completely agree! Load testing a battery will do zero damage to it. I have a load tester that is electronic and uses size 14 wires for the leads. Not much likelihood that it will be putting a huge load on a battery for any amount of time.

[distaff]

Old batteries, what is old. Bought mine in 2009. Tested them a few times. Testing is really cheap or free. Twice I tested them when I assumed it was time for new ones. Last test was three years ago.

Yup, don't test them, just buy new ones.

[YC1]

We do not buy batteries, we RENT them. None last forever and most batteries are murdered by poorly "electrically" educated folks.

I am posting a paragraph out of my Monaco manual. Storage and boondocking is the same basically.

These monsters have electrical drains in all kinds of places. Take the steps for example. They may be on the engine batteries. That is just one example.

Many great suggestions for aftermarket charge devices. Later models come with some sort of device now.

Be it a BIRD, IRD, or Turd there are many variations.

As suggested the easiest way to tell if the alternator is working is with a voltmeter. IF you are seeing a nice 13.5-14 volts across the batteries while running you should be fine assuming all connections are shiny and clean.

Old batteries simply do not work as well as new ones. Forty years of chasing battery issues in my communications service center taught me plenty.

If you add the trik-l-start or similar item your alternator will thank you for it. Always run your generator to refill coach batteries after boondocking versus trying to have the alternator work itself to death to refill them.

[YC1]

Note from manual:

[distaff]

Originally Posted by YC1

...

Be it a BIRD, IRD, or Turd there are many variations.

...

Old batteries simply do not work as well as new ones. Forty years of chasing battery issues in my communications service center taught me plenty.

All of the factory cross charging systems are turds, but once you understand them you can make them work.

Regarding old batteries - in electronics I agree that new batteries are always the first thing you try. In a vehicle it is not usually very subtle. Either it takes and holds enough charge to crank or it doesn't. As I noted, a couple of times I assumed it was time for new ones because I had accidentally discharged them completely (problems with the BIRD, or turd as you pointed out) and they were old.

The real challenge for starter batteries is cold weather, of which we have plenty, and I had mine tested because it was fall and I was worried they wouldn't be up to cranking in -20. Tests proved they were good and years later they are still reliable.

[YC1]

Even in the rather mild weather of Central California the Winter cold always found bad batteries. Customers would show up saying their two way radios were running their batteries down.

I should have sold batteries but I never did. The customers trusted me when I told them to go get a replacement and if it didn't solve their problem I would pay for it. I did several tests of course but the customers knew I was not trying to sell them something.

I had a fire chief with new vehicle battery problems his mechanic insisted was radio/electronics related. After about the third trip in I just bought a new battery for his brand new Expedition and solved the problem.

I never billed him for the new Battery. But he knew he could trust me.