Charging system troubles

Topic: Charging system troubles (Read 758 times) previous topic - next topic

Charging system troubles

July 29, 2018, 10:43:12 pm

I just left Nach after getting everything serviced and every little thing fixed. We did everything from changing the caliper pins to to putting a new bulb in the closet light. I drove from there to Roanoake. After about 900 miles the chassis voltage dropped and I had to come the rest of the way on the generator and boost switch.

I have no idea what's going on. I have put two alternators on this coach and Motorhomes of Texas has put one in the past couple of years. The alternators I used were Napa and MOT confirmed that's also what they use. They were a careful match for OE. Napa was kind enough to warranty the first two but I don't feel it's their problem. Something on the coach is causing them to fail.

When the Silverleaf reading started dropping on the chassis batteries it went down to about 11.7v so I fired up the generator. It was putting about 13.5 into the house batteries until I engagaed the boost switch which took it down about a volt. The Silverleaf showed about .3 v less. As I drove it dropped to about 12.3 on the Audit and 11.9 on the Silverleaf. In a little while it would come up to normal then back down. I was showing 11.9 on the Silverleaf as I pulled into the campground with the genset running and the boost on. The inverter charger isn't all that old either.

I don't trust driving back home on the genset because it's still showing marginal voltage most of the time it's running with the boost on.

The load didn't change. The dash air was on medium and no headlights or other heavy draw. The Audit shows plenty of voltage until I engage the boost switch so the problem is in the chassis side. It seems to me that enough corrosion in a wire connection or a relay to pull it down more than a volt would cause heat but I've never been able to find anyone indication of that. The batteries are not overheating and are are always strong even after sitting a few days.

This problem has repeated itself all three times I've had to come in on the generator.

Does anyone have an idea what could be going on or know someone in Roanoake or close by might figure this thing out?

Thanks for any ideas.

Re: Charging system troubles

Reply #1 – July 29, 2018, 11:15:01 pm

The first thing I would do is to check the output side of the alternator and see what the reading to ground is. Sounds as though there is a resistance of some amount like a wire that is rubbing against the frame that is passing some current but may not be enough to burn through the wire. Don't know your wiring, but sounds like it is some where close to your alternator that doesn't see boost voltage, or your alternator is capable of handling the load so far. (may burn up your alternator after some time). To get started, Disconnect wires, pull fuses, etc. and check for grounds. These kinds of troubles are hard to find and it just takes a good schematic, and diligence to run them down. Good hunting ---- Have a great day ---- Fritz

Re: Charging system troubles

Reply #2 – July 30, 2018, 02:31:53 am

Rick,
One possibility is a poor or intermittent ground path with the cable that goes from the negative terminal of the alternator to the frame. It could be that the bolt to the frame has been undisturbed all of this time (and has a poor/intermittent/variable connection), or it could be that the cable has intermittent/variable high resistance, aggravated by elevated engine bay temperatures. The reason I say that follows in my markup of your post:

I just left Nach after getting everything serviced and every little thing fixed. We did everything from changing the caliper pins to to putting a new bulb in the closet light. I drove from there to Roanoake. After about 900 miles the chassis voltage dropped and I had to come the rest of the way on the generator and boost switch.

I have no idea what's going on. I have put two alternators on this coach and Motorhomes of Texas has put one in the past couple of years. The alternators I used were Napa and MOT confirmed that's also what they use. They were a careful match for OE. Napa was kind enough to warranty the first two but I don't feel it's their problem. Something on the coach is causing them to fail. A poor/intermittent ground will cause the alternator to lose reference and will most generally undercharge the chassis battery. At the same time it can result in fluctuations in output current that overheat and possibly damage the alternator.

When the Silverleaf reading started dropping on the chassis batteries it went down to about 11.7v so I fired up the generator. OK. Chassis battery is not being charged. It was putting about 13.5 into the house batteries until I engagaed the boost switch which took it down about a volt. OK. A very low chassis battery will drag down the voltage on the House Battery Bank by that much, easily, when they are first paralleled. The Silverleaf showed about .3 v less. (Different sensing points. Not unusual at all) As I drove it dropped to about 12.3 on the Audit and 11.9 on the Silverleaf (IT being House?). OK. So the chassis battery is coming up some in voltage, just as it should. Remember, once you have the generator running and the boost switch closed, ALL of the Chassis Battery Bank charging current is having to come from your Invertor/Battery Charger, through the contacts on your boost switch (and they may be in poor condition, based upon the long term nature of this problem), so it isn't going to bring the chassis battery bank up very much, very fast. If I'm right, the Alternator has lost its ground reference and is back biased and is supplying no help. Depending upon the voltage regulator settings and Battery Charger settings, most coaches have zero charge current from the alternator once the generator is running, the battery charger is energized and the boost switch is closed. If the Battery Charger output voltage is higher than the Alternator output voltage downstream of the Isolator diodes, then both of the Isolator diodes will be back biased and no current will flow from the alternator -- Right?. In a little while it would come up to normal then back down. OK. Still sounds like a reference (ground) shifting, creating funny readings. I was showing 11.9 on the Silverleaf as I pulled into the campground with the genset running and the boost on. The inverter charger isn't all that old either. It will take the battery charger a LONG time to bring a DEAD chassis battery bank back up to good readings through the small contacts of a questionable boost switch. AND, depending upon what your Inverter/BatteryCharger settings are, and how much temperature compensation was kicking in, your House Battery Bank was very possibly having more drawn out of it than was being replenished by the Battery Charger.
I don't trust driving back home on the genset because it's (IT being Chassis or House or Both?) still showing marginal voltage most of the time it's running with the boost on. Its marginal because of the reasons stated above. Also, remember that the running engine room imposes a current burden also. Things like the ECM for the engine and the ECU for the transmission and all of that current has to go through the Boost Switch contacts — the chassis battery bank only gets what is left over. If I'm right and you start out in the morning with fully charged house and chassis battery banks AND the generator running AND the Battery Charger energized AND the Boost Switch closed, you should be able to drive from East Port, ME to San Diego with no second thoughts, as long as you don't exceed the battery banks plus battery charger output capacity (total dc current demand).

The load didn't change. The dash air was on medium and no headlights or other heavy draw. The Audit shows plenty of voltage until I engage the boost switch so the problem is in the chassis side. Agree, but it is a dead chassis battery bank and the small charging current that delay recovery while driving. So the issue is why isn't the chassis battery bank being charged? Poor sensing wire connections to the alternator?, That could be common to several rounds of alternator replacements. But I still favor a poor alternator ground reference (poor connection to frame or partially defective cable). It seems to me that enough corrosion in a wire connection or a relay to pull it down more than a volt would cause heat but I've never been able to find anyone indication of that. The batteries are not overheating and are are always strong even after sitting a few days. OK. More indication of an Alternator ground reference issue. If the batteries charge properly when plugged into shore power, when the battery charger doesn't have to supply an operating engine room through the boost switch, then the battery charger is good. The charge rate settings may be low due to the way you have it programmed or through temperature compensation sensing set up. AND, how do you charge the chassis battery bank when you are parked and on shore power?

This problem has repeated itself all three times I've had to come in on the generator.

Does anyone have an idea what could be going on or know someone in Roanoake or close by might figure this thing out?

Thanks for any ideas.

HTH,
Call if you need to talk. six oh three 770 seven 459
Neal

Re: Charging system troubles

Reply #3 – July 30, 2018, 07:14:13 am

Most likely a battery or connection at or near the batteries, as the charge path from alternator through battery isolator is COMPLETELY DIFFERENT than the inverter/ charger directly to the house bank and through the boost solenoid to the chassis battery.

Since you had issues both ways, start trouble shooting at the batteries (charge and then load test) and their connections.

Re: Charging system troubles

Reply #4 – July 30, 2018, 09:05:07 am

Thanks for the suggestions. I knew this group would come to help and even though I've never met either of you in person I'm not surprised that the two of you responded so quickly because I've seen you both do that time and time again.

When I was growing up I got so tired of hearing my dad say "look for a bad ground." He's been gone a long time but when I get into a situation I like this I still hear his words. Now you two are telling me to listen to my dad's advice.

The battery cables are spotless and I've removed the cables stacked on the lugs and didn't see any corrosion. I did have trouble with the sensor wire on the alternator but hadn't thought much about the ground from there.

I guess in a situation like this it's always back to the basics. I'll get the batteries all fully charged while plugged in then look for a bad connection on the ground somewhere.

Neil, thanks so much for the phone number. I may be calling after while or tomorrow. You two are the best.

Re: Charging system troubles

Reply #5 – July 30, 2018, 09:08:04 am

Charge to start batteries goes from Alternator to the center post on the isolator and then from a side post to one side of the boost solenoid and then from that same post on the beeost solenoid to the positive side of your start batteries.

Start with the basics. With the boost switch off and engine not running, remove the negative cable from the battery set. Then the positive cable, cober the ned so it doesn't touch anything. Make sure all of the plus side battery connections are clean, reassemble them and make sure the connections are secure. Do the same on the negative side.

With the engine running and boost switch off you should measure about 13.6 volts at the batteries, maybe 13.7 at the side of the boost solenoid, about 13.7 on the start battery side post on the isolator and about 14.4 or so at the center post of the alternator.

The most common problem will be connection points especially at the batteries. Cables can fail but that is not common. Isolators do fail and you can do a workaround for a short time. Alternators fail too but that doesn't sound like the problem be
here.

Start at the point of the problem and work backwards. Do the simple stuff first. Work safely around batteries and cables. I have some short chunks of 3/4" foam pipe insulation that I slip over + cable ends just to be safe.

Let us know what you find and what else we can do.

Re: Charging system troubles

Reply #6 – July 30, 2018, 09:18:40 am

Just to add comment All of my alternator problems related back to a bad isolator. After three alternators the rebuilder had me bring the coach to his facility and he diagnosed the real problem.

Re: Charging system troubles

Reply #7 – July 30, 2018, 09:26:57 am

He bypassed the isolator by taking the alternator charge wire and relocating it directly to the house batteries I think. Said as long as I didn't boondock it would keep me on the road... It worked and I changed out the isolator when we got home.

Re: Charging system troubles

Reply #8 – July 30, 2018, 12:35:17 pm

Rick,
A couple of comments to add to Brett and Roger's help:

Quote from: wolfe10 – July 30, 2018, 07:14:13 am

Most likely a battery or connection at or near the batteries, as the charge path from alternator through battery isolator is COMPLETELY DIFFERENT than the inverter/ charger directly to the house bank and through the boost solenoid to the chassis battery.

Since you had issues both ways, start trouble shooting at the batteries (charge and then load test) and their connections.

As you know, the Chassis Battery Bank on the 2002 is in a terrible location to work on. I agree with Brett that the problem is most likely in the Chassis Battery Bank, Alternator or Isolator close proximity. But doing what he suggests is a bear. I recently went through just that (First -- level, hard surface, creeper, raise coach, safety block, fumble in the overhead rack forward of muffler to remove insulate, clean, dielectric coat, re-land the cables. In my case, no improvement. So, remove all cables again, remove the battery hold downs, wrestle the three 70 pound batteries, up and out of the tray, out of the overhead, onto the ground, laying on your back, etc.) In my case, even though the batteries would not turn the coach over, by themselves or boosted with an iH-45, for over an hour, they tested fine in individual load tests. Because the batteries were about 5 years old, I put new batteries back in and all has been fine ever since, except it is unknown what was wrong with them, as a bank. They were clearly breaking down as a bank, under heavy load, but then individually tested fine at (0.9 (+) performance for 925 amps ea.). Stumped me and the best minds at FOT.
I was sore for days afterward from a Memorial Day weekend, filled, non-stop, with these gyrations.
John S and Brad M aren't far from Roanoke, so if you don't want the exercise, maybe they have RV Service Center recommendations. Also, I see that Salem, VA has a business (Tonie's RV). The information is somewhat dated, but the business is spoken highly of in RVServiceReviews.com

Quote from: Roger & Susan in Home2 – July 30, 2018, 09:08:04 am

...............Start with the basics. With the boost switch off and engine not running, remove the negative cable from the battery set. Then the positive cable, cober the ned so it doesn't touch anything. Make sure all of the plus side battery connections are clean, reassemble them and make sure the connections are secure. Do the same on the negative side.

With the engine running and boost switch off you should measure about 13.6 volts at the batteries, maybe 13.7 at the side of the boost solenoid, about 13.7 on the start battery side post on the isolator and about 14.4 or so at the center post of the alternator. .....................

Good advice from Roger (as always). Remember that Roger is giving you voltages for a fully charged Chassis Start Battery Bank. If you do not have a fully charged bank, as I suspect, your voltages will be somewhat different. The critical voltages, to verify proper Isolator operation, are the voltage drops across the two diodes. They should be about 0.60 to 0.70 Vdc for a bank that is fully charged and it will generally be 0.90 to 1.00 Vdc when a bank is deeply discharged (due to the current flow through the diode). Otherwise, the voltage drops across the two diodes should be similar and in that range. I had asked how you are charging your Chassis Start Battery Bank when you are on shore power. If you are not using a healthy Boost Switch or a separate, somewhat robust charger (10 to 15 amp dc or greater), a deeply discharged bank is not going to recover much overnight. Then when you start driving, if the alternator is not charging consistently, it will quickly deplete and start eating into your House Battery Bank, through the Boost Switch, as well. That might help explain why you drove 900 miles before the issue started cropping up.
HTH,
Keep us up to date,
Neal

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Charging system troubles

July 29, 2018, 10:43:12 pm

Re: Charging system troubles

Reply #1 – July 29, 2018, 11:15:01 pm

Re: Charging system troubles

Reply #2 – July 30, 2018, 02:31:53 am

Re: Charging system troubles

Reply #3 – July 30, 2018, 07:14:13 am

Re: Charging system troubles

Reply #4 – July 30, 2018, 09:05:07 am

Re: Charging system troubles

Reply #5 – July 30, 2018, 09:08:04 am

Re: Charging system troubles

Reply #6 – July 30, 2018, 09:18:40 am

Re: Charging system troubles

Reply #7 – July 30, 2018, 09:26:57 am

Re: Charging system troubles

Reply #8 – July 30, 2018, 12:35:17 pm

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