How Do Your Batteries Charge?

[Shadowman]

First of all, I apologize for asking so many questions, but hopefully others will learn from the responses I get, just like I have been learning from all the other questions.

So here is the question - How do the batteries charge? I was under the understanding that the batteries would charge under 3 conditions. First while driving. Second, while running the generator. Third while plugged into shore power.  Have I been misinformed?

Over the past weekend, I pulled into camp on Friday night and turned the coach off so I could figure where to park, went to move it, and the battery was dead. (Engine Battery 1 year old). So I used the house battery (emergency start) to get it started. The next morning I made sure all connections were tight and tried to start it and it fired right up. When we went to leave it was dead again.

In addition, during our time at camp, I ran the generator for a number of hours in attempt to charge the house batteries. They never got to higher than 3/4 fully charged.

On the drive home, I continued to use the emergency start when we stopped for gas. When I pulled up to the house and unloaded the trailer, I went to start the coach and again, dead battery so went to use the emergency start, and dead battery?

The 2 aux batteries were put in new 4 weeks ago. So for some reason I'm not getting anything to charge. Could this be multiple problems or could I be lucky enough to have one source creating this problem?? Is the same system used to charge from the Generator and the engine?

As always, thanks in advance for your insight. I'm learning.

 

[blueblood]

First of all, I apologize for asking so many questions, but hopefully others will learn from the responses I get, just like I have been learning from all the other questions.

So here is the question - How do the batteries charge? I was under the understanding that the batteries would charge under 3 conditions. First while driving. Second, while running the generator. Third while plugged into shore power.? Have I been misinformed?

Over the past weekend, I pulled into camp on Friday night and turned the coach off so I could figure where to park, went to move it, and the battery was dead. (Engine Battery 1 year old). So I used the house battery (emergency start) to get it started. The next morning I made sure all connections were tight and tried to start it and it fired right up. When we went to leave it was dead again.

In addition, during our time at camp, I ran the generator for a number of hours in attempt to charge the house batteries. They never got to higher than 3/4 fully charged.

On the drive home, I continued to use the emergency start when we stopped for gas. When I pulled up to the house and unloaded the trailer, I went to start the coach and again, dead battery so went to use the emergency start, and dead battery?

The 2 aux batteries were put in new 4 weeks ago. So for some reason I'm not getting anything to charge. Could this be multiple problems or could I be lucky enough to have one source creating this problem?? Is the same system used to charge from the Generator and the engine?

As always, thanks in advance for your insight. I'm learning.

It's an all depends answer i.e. it depends on the design of the motorhome. But, yes , all three will charge batteries in some motorhomes. The alternator can charge them or the genset or shore power through the Inverter/Charger device. Some brands have setups that isolate the chassis batteries from the coach batteries so one can't inadvertently drain the chassis batteries while dry camping and using inverter. These units usually provide that the Inverter/Charger brings house batteries up to a set point then open circuit to allow the dual charging i.e. both sets of batteries.

 

[Dan Walters]

Well, I thought I would comment on this problem as well.  This sounds EXACTLY like what I went through with my batteries.  I ended up replacing all three (chassis and 2 house) batteries.  After I did that, I discovered that my alternator was not charging the batteries either, so I had the alternator re-built.  If your MH has the Chevy chassis with the 454, it's probable the same alternator.  I could not find a new one anywhere in this area (Southeast Texas) so I took the old one off and had a local alternator shop re-build it.  I will get it back this afternoon and will find out if this cures all my battery and charging problems.

 

[Gary RV_Wizard]

Yes, there will necessarily be a  lot of "ifs" and "it depends" in any answer to this problem.

The primary charging means for the house batteries is the converter/charger (or inverter/charger, if so equipped). The converter gets its input power from the house 120VAC circuits, which in turn are powered from either shore power or the generator.  In late model rigs, the house charging system may also charge the chassis (engine battery) when the engine is not running, but this is not generally the case in older rigs. If the converter charger is not functioning, you cannot charge the house bateries from either genset or shore power.

The primary charging system for the chassis/engine battery is the engine alternator.  If the alternator is not prducing a chaging current, the chassis battery will not get charged (except as noted in the previous paragraph).  In most rigs the alternator will also charge the house batteries while the engine is on, but not every rig is wired this way. The chassis battery is normally isolated from the house batteries so that you cannot inadvertently drain the chassis battery while using house power.  The Emergency Start switch bypasses the isolator so you can start the engine with the house batteries. It works the other way too - you can use the engine battery to supply house power by holding in the Emergency Start switch and doing so also allows the house converter/charger to re-charge the chassis battery.

It is necessary to avoid having more than one charger attempting to charge the same battery at the same time. That's why some rigs simply don't provide more than one way to charge each battery.  Those that do provide this capability have a fairlycomplex set of circuits that detect what chargers have charge voltage available and then sets  one or more relays to allow one (and only one) charer to send charging voltage & current to each battery.  If those sensing circuits and/or relays fail, then charging may not occur when it should.

Most of your symptoms sound like a defective alternator, one that is not putting out enough charge to keep the chassis battery alive.  This is a common symptom of something called alternator diode failure, where the alternator produces enough voltage to keep the dashboard alternator warning light off but does not produce enough electrical current to do any useful charging.

It's possible that your final episode of dead house batteries happened simply becasue you used them to start the rig several times. The house batteries are not designed for starting loads and will be depleted fairly quickly. And you didn't mention wheher they are relatively new or in good condition or not. It sounds as though they may not be, but there isn't enough information to tell for sure. Running the generator for several hours is not enough to fully charge depleted batteries, so your 3/4 charge level might well be within normal expectations.  It takes 24 hours or more to get a battery from 3/4 charge to full charge, especially on older rigs with wimpy converter/chargers. Some of them produce only 5 amps max and are reduced to a trickle once the batteries reach the 3/4 charge stage. 

 

[John From Detroit]

I am going to second what Romer said and add that on the newer coaches where, as he mentioned, both the engine alternator and the inverter/converter can charge the chassis and house batteries there may well be a safety cut out that is voltage based.

On my rig, for example, when the batteries are nice and full of charge, they are also connected in parrallel, but should the system drop to a set point (and I have no clue as to what it is) the batteries are isolated from each other.  Just normal starter draw will usually take the system below that set point.

They reason for isolating the batteries is to insure you have enough to go,  But if I had to guess I'd say the set point is 3/4 charge and the reason the house batteries never got above that was because the chassis battery was draging the system down

 

[Karl]

Gary,

He did say that the aux batteries were only 4 weeks old. Sounds like the alternator isn't charging the chassis battery and the either the converter is shot or has a blown fuse, or the inverter wasn't turned on. Not sure which he has, but on mine, the generator or shore power powers the inverter which must be on to charge the house batteries. Same with the engine alternator - inverter must be on to charge the house batteries. Makes sense since the Link 1000 controls the aux battery charging.

 

[Ned]

Generally, charging from the engine alternator is independent of the inverter/charger.  There should be an isolator in the circuit to allow charging both the chassis and house batteries from the alternator, even if you don't have an inverter/charger.  Strictly speaking, the inverter has nothing to do with charging the batteries, it's the charger part of the box that does that.  They just happen to be in the same enclosure and share the battery leads.  With the Link 1000, you can turn the two devices on and off independently.

 

[Shadowman]

Thanks guys, as always, great advice. I did pull the alternator, based on the input I got from everyone. Took it to the local Checker Auto and they confirmed what most here were saying. The Alt was only putting out a little over 8 volts, which was enough to keep the engine running and the lights on, but not enough to turn it over. I bought a new alternator, but I got home to install it, and wouldn't you know it, I forgot to take the bracket off the other, went back to get the bracket, go home and went to put it in, only to find out they gave me the wrong alternator.  I shouldn't be surprised, there has never been a time where I can get away with 1 trip to the auto parts store or the hardware store. Just a fact of life.

Again, just wanted to thank everyone for the advice. I'll be up and running in no time.

 

[Jeff]

Thanks guys, as always, great advice. I did pull the alternator, based on the input I got from everyone. Took it to the local Checker Auto and they confirmed what most here were saying. The Alt was only putting out a little over 8 volts, which was enough to keep the engine running and the lights on, but not enough to turn it over. I bought a new alternator, but I got home to install it, and wouldn't you know it, I forgot to take the bracket off the other, went back to get the bracket, go home and went to put it in, only to find out they gave me the wrong alternator.  I shouldn't be surprised, there has never been a time where I can get away with 1 trip to the auto parts store or the hardware store. Just a fact of life.

Again, just wanted to thank everyone for the advice. I'll be up and running in no time.

Shadowman:

Our 83 Pace Arrow (Chev 454 on a P-30 chassis) went through alternators regularly because of the continuous high loads the RV subjected the charging system to. I seem to remember we had an 85 amp alternator that there was a bolt on replacement  for that had internal regulator and an output of 115 amps. Lasted until we sold the coach several years later.

 

[John From Detroit]

The alternator on my toad is over 100 amps capacity.. I have no clue what the MH's capacity is

 

[Dan Walters]

When I tried to find a new alternator for mine, none of the auto parts stores had the right one in stock.  When they look up the part on their system, it does not reference the alternator for the P37 chassis(the P30 for motorhomes).  You have to give them the part number that is etched in the alternator housing.  On mine the part number was 10480088.  When they put that part number in, it tells them that they don't carry it and have to special order it.  I couldn't even get it at the dealer that serviced the workhorse chassis.  They also had to special order it.  That's why I took mine to the alternator shop and had it re-built.  It cost me $65 plus tax and has a warranty.  That's less than half what a new one costs.  Mine was a 115 amp alternator.  I think the older MH's did have a smaller output, but they started putting the larger one on them in the 90's.

 

[Karl]

Dan,

That sounds like a pretty good deal When an alternator puts out 8 volts, that almost always indicates that a pair of diodes went South. They probably replaced them all, pressed in new bearings, and changed the slip-rings and brushes - good as new.

 

[Shadowman]

Dan:

I think you jinxed me ;D

Thought I was in good shape, took the alternator back to Checker to get the right one! Believe it or not, they didn't have the right one, they searched and pulled out 4 different alternators all of which didn't work. Blasted.  So took it to my friendly neighborhood Auto Zone. The one thing that impressed me about their query is that it did include the P30 chasis as an option, rather than having them look up under 1 ton or Van.  So I've got all apendeges crossed in hopes that it will be the right one.  I wish I would have looked at the responses first, I would have requested a higher capacity, like the 115.  Oh well, as long as it charges I'll be in good shape.

Thanks again for all your advice, I'll keep everyone posted on progress.