Skip to main content ↑ ↓
Topic: Roadside blues... Again (Read 1500 times) previous topic - next topic

Roadside blues... Again

 :-\  Moving from a campground down the highway, and the Heart Freedom starts blinking and the SeeLevel gauge indicates that the house bank is 17 volts! Turn the inverter off and kill the engine. Voltage drops to normal range, but house bank bay smells like sulfur. Start it up, House bank goes back up to 17 volts. Chassis battery seems normal according to VMSPC. Popped the bed, and it the isolated looks like the cable  on curb side of the isolator has been very hot. So what to do? Can I bypass the isolator with a switch or disconnect the house bank from it without destroying something? I just want to get it back home base where I can work on it with access to my stuff... Just turning the inverter off didn't help anything. Is it the alternator that may have failed and is putting out to many volts? I am not think that clearly at the moment, so any objective input would be appreciated!
Don

Re: Roadside blues... Again

Reply #1 –
We had that same problem in 06 and turned out to be the voltage regulator on the alternator. easy fix with the right part. :(

Re: Roadside blues... Again

Reply #2 –
Do not rely on readouts from the Displays.  Use your multimeter to make sure of these voltages before you go nuts looking for something that is not there.

Re: Roadside blues... Again

Reply #3 –
Don,

Yes, you can bypass the isolator so that the chassis battery is charged, but house is not.

But, first thing I would do is separate the house batteries and see if there is one bad battery that you can just take out of the circuit.

If not successful, remove the center wire on the isolator (from alternator) and nut it to the chassis battery lug of the isolator.

But, I am a little puzzled.  The sense wire for the alternator is generally on the chassis battery lug of the isolator, so a bad house battery should not trigger out of spec voltage. 

Re: Roadside blues... Again

Reply #4 –
I did check with a meter and it agrees with the SeeLevel... Just did another test. With the generator running, but not the engine, the Inverter appears to be charging the house battery normally. Generator off, start the engine, and for about 60 seconds, everything seems normal. Then, the lights on the inverter go crazy, and the house bank is showing 17 and the chassis shows normal. This was verified at the batteries. Now the question is, how can I disconnect the house bank from the alternator/isolator combo without frying something?
Don
 

Re: Roadside blues... Again

Reply #5 –
Don, Why can't you just turn the inverter off and disconnect the house batteries to get you home ?
Gary B

Re: Roadside blues... Again

Reply #6 –
Quote from: wolfe10 –
Don,

Yes, you can bypass the isolator so that the chassis battery is charged, but house is not.

But, first thing I would do is separate the house batteries and see if there is one bad battery that you can just take out of the circuit.

If not successful, remove the center wire on the isolator (from alternator) and nut it to the chassis battery lug of the isolator.

But, I am a little puzzled.  The sense wire for the alternator is generally on the chassis battery lug of the isolator, so a bad house battery should not trigger out of spec voltage.
I did separate the two house batteries from each other and they appeared to be the same voltage. Unfortunately, I apparently fried my SeeLevel tank gauges when I reconnected the house bank... should have used the disconnect switch, duh! Ironically, the voltage portion of the SeeLevel gage still works. Oh well, live and learn or die trying! Oddly enough, the curbside cable (the melted looking one) on the Isolator corresponds to the chassis battery voltage, and the the street side corresponds to the house bank. the plastic strip along the top of the isolator appears to be somewhat melted as well... but I am not sure if that is new or not.
Don
 

Re: Roadside blues... Again

Reply #7 –
I will certainly do that if that doesn't screw something else up. Unfortunately, this is one area of coach lore that I haven't explored yet, though it is on my list... :o
Don
Quote from: Gary Bouland –
Don, Why can't you just turn the inverter off and disconnect the house batteries to get you home ?
Gary B

Re: Roadside blues... Again

Reply #8 –
Don, sounds like your alternator has gone haywire.  I'm afraid you run the risk of ruining your chassis batteries also. Might consider completely disconnecting alternator and using the genset to make it home. 

Re: Roadside blues... Again

Reply #9 –
See my first post for how to isolate the house battery bank-- actually, just direct connecting alternator output to chassis battery lug of isolator.  If you recall, I basically did this on our U240 permanently: Alternator output, sense wire and chassis battery to one lug of marine ON-OFF switch.  House battery cable to the other lug.  With switch off, alternator charges only chassis battery.  With switch on, both banks charged.

But, you also want to make sure that the sense wire is in good shape, as that is the wire that "regulates" the voltage.

Re: Roadside blues... Again

Reply #10 –
Thanks Brett! I had already done as you suggested... just had tried it yet. I started by disconnecting the house bank, and starting the engine... Chassis battery showing normal charging voltage. Reconnected the house bank and it is showing battery voltage. So, my best guess is that the isolator has taken a shortcut to heaven... bloody coward. I just needed it to go another 200 miles. Thanks for your help! On the road again, will update when we make home!
Don
Quote from: wolfe10 –
See my first post for how to isolate the house battery bank-- actually, just direct connecting alternator output to chassis battery lug of isolator.  If you recall, I basically did this on our U240 permanently: Alternator output, sense wire and chassis battery to one lug of marine ON-OFF switch.  House battery cable to the other lug.  With switch off, alternator charges only chassis battery.  With switch on, both banks charged.

But, you also want to make sure that the sense wire is in good shape, as that is the wire that "regulates" the voltage.

Re: Roadside blues... Again

Reply #11 –
Don, time to put in a Sterling unit.!!!
I have not done it yet as been busy-sort of with other things. Hopefully will get it in before heading south, if not will take it with us to do in the warmth.
JohnH

Re: Roadside blues... Again

Reply #12 –
Bomb-proof solution-- wire as in my post above: PERKO Inc. - Catalog - Battery Switches - Heavy Duty Battery Disconnect Switch

Other use:  in CG with shore power this morning.  In CG with shore power tonight.  Why pay diesel to OVERcharge the house bank all day?  Leave switch off.

Other use:  Excellent/safe battery combiner for starting (rated 1200 amps intermittent).

Other use: Combine so that converter or inverter/charger charges BOTH battery banks with on shore power.

Easy to mount at the foot of the bed.

MANUAL IS SOMETIMES THE CORRECT KISS ANSWER.

Re: Roadside blues... Again

Reply #13 –
brett,

Does the alternator regulator have to be adjusted to account for the increase in charging voltage after the isolator is removed?

Larry

Re: Roadside blues... Again

Reply #14 –
Quote from: LTG –
brett,

Does the alternator regulator have to be adjusted to account for the increase in charging voltage after the isolator is removed?

Larry

Larry, 

The sense wire is left in place.  So, voltage at the chassis battery is exactly the same as before.  The only difference is because the loss across the diode-based isolator (about .7 VDC) is eliminated, the alternator does not have to "over-produce" only to have some if its production turned into heat in the diode-based isolator.  HEAT is why the diode-based isolator has all those aluminum fins-- to get rid of the heat.

Re: Roadside blues... Again

Reply #15 –
Don,
  Shortly after we bought our coach I had the same thing happen. It was a bad isolator. I installed a new 200A unit and it has been fine ever since.

Mark

Re: Roadside blues... Again

Reply #16 –
So Brett. Does the Perko switch enable you to remove the isolater from the system ? I had those on my bus but never new what they did.

Re: Roadside blues... Again

Reply #17 –
Quote from: Andy 2 –
So Brett. Does the Perko switch enable you to remove the isolater from the system ? I had those on my bus but never new what they did.

Yes, if wired:  alternator B+/positive to one lug.  Chassis battery cable to same lug.  Sense wire to same lug.

House battery cable to other lug.

Just a slight variation on the way all our sailboats were wired-- and 90% of their use was "wet-camping" (w/o shore power and no generator).

Re: Roadside blues... Again

Reply #18 –
 Thanks Brett, Next project.

Re: Roadside blues... Again

Reply #19 –
Don, I agree with all that Brett has offered.
Question, did you ever heed my advice and move your alternator sense wire off of the forward engine compartment bulkhead to the engine start battery bank (+) terminal posts?  If you did not, it easily explains everything written in this thread (both this entry and all subsequent entries).  Where is the far end of your alternator battery voltage sense wire landed? 


See:  http://www.foreforums.com/index.php?action=media;sa=album;in=170
 
Here are a few comments entered into your initial question:
Moving from a campground down the highway, and the Heart Freedom starts blinking and the SeeLevel gauge indicates that the house bank is 17 volts! That means the alternator lost good communication with BOTH battery (+)'s, and the alternator has failed to maximum output (17 Vdc), trying to increase the voltage at the far end of the sense wire.
Turn the inverter off and kill the engine. Voltage drops to normal range, but house bank bay smells like sulfur.  That means the house batteries have been grossly overcharged.  I assume that the engine start batteries were normal smell and their cases and cables were not warm or hot?
Start it up, House bank goes back up to 17 volts. Chassis battery seems normal according to VMSPC.  Engine start battery would be the normal Vdc because the Isolator diode has been burned out (OPEN circuit path) and the engine has not discharged the start battery bank for long enough to significantly discharge the bank, even though it is not being charged.
Popped the bed, and it the isolated looks like the cable  on curb side of the isolator has been very hot.  I assume that the "curb side" is the start battery bank side cable and that that isolator diode has seen over voltage and is burned out (OPEN).
So what to do? At the isolator, tie the house battery bank cable, the start battery bank cable, the Alternator output cable and a temporary Alternator sense Jumper wire  all together on the one good terminal of the isolator.  If voltages (with the engine running) return to normal, you know what the problem is.  The battery start bank sense wire (from the alternator to  the start battery bank's (+) terminal, has partially or totally failed (opened or significantly increased in resistance, which drops voltage, which makes the alternator think the start battery bank is low, which causes the alternator to increase its output, which eventually goes to maximum, which is 17Vdc.).  With the Alternator output going high (17 Vdc), it overcharges both battery banks until an isolator diode or a battery fails to an OPEN  circuit condition (usually taking out things like your SeeLevel instruments along the way because, unless specifically designed to be protected, they cannot tolerate the 17Vdc continuously).
Can I bypass the isolator with a switch or disconnect the house bank from it without destroying something? I just want to get it back home base where I can work on it with access to my stuff... Just turning the inverter off didn't help anything. Is it the alternator that may have failed and is putting out to many volts? I am not think that clearly at the moment, so any objective input would be appreciated!
 
BTW, if I am right, there is nothing wrong with your alternator (it is doing only what it should be doing).  The isolator is definitely toast and the "plastic strip" that you refer to is really a "brick" of diode potting compound that has been melted from overcurrent.  No telling how much sympathy the house batteries have for all this.  Are the sides bulged badly?  The start batteries also saw abuse until the overcharging blew the isolator diode to that bank, so check for bulging there too.

Call if you have questions, 603-770-7459
 
Neal