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Old 10-28-2012, 01:48 PM   #1
Kenneth
 
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Battery Charging Problem. PLEASE HELP!

I never dreamed I would get so self sufficient keeping this ole bus going down the road but this one stumps me. Trying to keep this short I'll say I've used an ohm meter before and have tested all that seems relevant. With engine running everything works/charges fine. With the generator running by itself everything checks out ok as well. However when the engine is running and then you turn on genset as well, thats when I have problems. In my owners manual it says that the alternator and univolt charger will charge all three batteries simultaneously if engine and genset are both running. But in my case once the genset relay closes and energizes the 120 volt system, the 12 volt meter on the dash discharges down to 10. If you are running lights or dash a/c, etc it will eventually discharge down lower until the cranking battery is dead. Coach batteries seem to be unaffected by this. Any ideas on where I should start looking? Thanks
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Old 10-28-2012, 02:52 PM   #2
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Here's how the system works on my 360 Classic system works. The coach and chassis battery are isolated. The only time they are tied together is when the aux battery relay closes via the momentary switch on the dash for extra power to start the engine.

The battery isolator allows the alternator to charge both the coach and chassis batteries. The diodes in the isolator prevent either either system to power the other. The generator powers the coach AC system which powers the DC converter/charger. The coach batteries will be charged provided the coach battery switch is on.

It sounds like someone tied something from the coach into the chassis power system.

I would start by making the two systems are isolated. Disconnect the chassis battery(s) and see if there is voltage on the + cable indicating that it is being feed from the coach battery(s).

My aux battery relay was stuck on because the switch on the dash had failed on. Caused all kinds of problems.

Make sure you Univolt (or whatever brand it is) is putting out about 13.5 volts. Mine was putting out about 12 volts which will run the system but will not charge the battery.
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Old 10-28-2012, 08:21 PM   #3
Kenneth
 
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I haven't tried that test, but I certainly will in the morning. Thank-you. It's interesting that the previous owner had placed a cable between the + terminals on chassis battery and coach battery to link them and I guess it worked for him. It seems that if they are all three linked together, things work fine. I took it off because its not supposed to be there and I want to make sure I dont run the chassis battery down using accessories. I should mention that when traveling if we have to run the genset, I have to hit the battery switch in the glove box for about 20 seconds every 2-3 minutes to bring the volt meter on the dash back up.
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Old 10-28-2012, 10:02 PM   #4
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Quote:
Originally Posted by 1987_345 View Post
I never dreamed I would get so self sufficient keeping this ole bus going down the road but this one stumps me. Trying to keep this short I'll say I've used an ohm meter before and have tested all that seems relevant. With engine running everything works/charges fine. With the generator running by itself everything checks out ok as well. However when the engine is running and then you turn on genset as well, thats when I have problems. In my owners manual it says that the alternator and univolt charger will charge all three batteries simultaneously if engine and genset are both running. But in my case once the genset relay closes and energizes the 120 volt system, the 12 volt meter on the dash discharges down to 10. If you are running lights or dash a/c, etc it will eventually discharge down lower until the cranking battery is dead. Coach batteries seem to be unaffected by this. Any ideas on where I should start looking? Thanks
Have you checked voltage at the isolator in all conditions you mentioned?
Have you checked voltage of the engine battery with just the genset running. The problem may be your genset drawing excessive voltage for reasons I would not know.
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Old 10-29-2012, 12:33 PM   #5
Kenneth
 
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Thanks Peter. The voltage at the isolator is normal (14-15 at center terminal and 13-14 at upper and lower terminals) unless you turn on the genset while coach engine is running, then lower terminal (going to chassis battery) drops way down, like 10 to 7. I will try your other idea tonight when I get home. One other thing I noticed this morning was that this isolator must have been changed. According to my manual there should only be 3 terminals on it. Mine has an extra smaller terminal which goes to the ignition. It's supposed to be hot only when the ignition is in "on" position. It seems to be functioning as intended. I think however that I may disconnect that 4th terminal and see if it has any effect.
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Old 10-29-2012, 12:51 PM   #6
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It would help if you included the brand name and number of the isolator or a picture of same.

SurePower has very good detail on their site.
http://www.grampianowners.com/Links/...lator_Inst.pdf

The isolator should be the only place the two battery banks are tied together, except for the override start boost switch on the dash. (which should be normally open)

Disconnect any other cables that tie the battery banks together and go from there.



Dave

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Thanks Peter. The voltage at the isolator is normal (14-15 at center terminal and 13-14 at upper and lower terminals) unless you turn on the genset while coach engine is running, then lower terminal (going to chassis battery) drops way down, like 10 to 7. I will try your other idea tonight when I get home. One other thing I noticed this morning was that this isolator must have been changed. According to my manual there should only be 3 terminals on it. Mine has an extra smaller terminal which goes to the ignition. It's supposed to be hot only when the ignition is in "on" position. It seems to be functioning as intended. I think however that I may disconnect that 4th terminal and see if it has any effect.
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Old 10-29-2012, 07:30 PM   #7
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Ok, I disconnected the chassis battery to see if it was somehow being fed by the coach batteries and it was not so I reconnected it. I then checked the voltage with genset only running and found the chassis battery at only 12v, but perhaps it was fully charged???. The coach batteries were reading 14v each. Same values were found when a reading was taken at the isolator. I then disconnected the exciter wire on the isolator because the original isolator didn't have one. But that only caused a voltage discharge with engine running. Didn't change when I cranked the genset either. Got some information off of the isolator. It is a Sure Power Industries brand model 1202-3A. I think the label says it is rated for one main battery and one aux battery, but I can't be sure. If that's the case it may be under rated since I have two aux batteries. Thank-you again for your help.
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Old 10-30-2012, 09:24 PM   #8
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Back to square one. Talked to the pros at the Surepower help center and they walked me through the isolator tests. It is A-ok and adequate for the application. Something is really pulling the DC system down when the AC system energizes....
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Old 10-30-2012, 10:50 PM   #9
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Call me crazy, but have you checked the battery ground strap on battery tray? May have nothing at all to do with this, but who knows?
Good Luck, Derek
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Old 10-31-2012, 06:18 AM   #10
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Back to square one. Talked to the pros at the Surepower help center and they walked me through the isolator tests. It is A-ok and adequate for the application. Something is really pulling the DC system down when the AC system energizes....

You ment to say pulling chassis DC system down.
Next thing I would do is connect a separate battery to the genset and see what happens. This way you can at least rule out the genset being the culprit.
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Old 10-31-2012, 08:27 AM   #11
Kenneth
 
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You're right Derek. A faulty ground can cause lots of problems. Although I don't believe that is it, it has been undisturbed for 25 years. I think I'll take it apart tonight, clean and reassemble just to be sure. Thank-you.

Right Peter its pulling the chassis DC system down. I'm not sure what you mean by connecting a separate battery to the genset. Let me be really detailed here. With the coach engine running everything is fine. When I start the genset it discharges momentarily but once the genset starts up everything is fine until the AC light comes on. It's bound to have something to do with the Univolt charger. I think tonight I will unplug the univolt charger and run the tests. The culprit may be the univolt or something between it and the chassis battery. Unfortunatley I don't have that particular wiring diagram. Thank-you. Kenneth
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Old 10-31-2012, 11:37 AM   #12
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We may be getting closer to a solution, and I hope this never happens to anyone else. I despise electrical issues. I went home and ran some more tests.

Connected to Shore Power
Isolator
Input 0v
Both Outputs 12v
Batteries
Chassis 12v
Coach 12v

Engine running w no Genset
Isolator
Input 14v
Both Outputs 13v

Batteries
Chassis 13v
Coach 13v

GenSet Only
Isolator
Input 0v
Chassis Output 12v?
Coach Output 14v
Batteries
Chassis 12v?
Coach 14v

Genset Only with Univolt unplugged
Isolator
Input 0v
Both Outputs 12v
Batteries
Chassis 12v
Coach 12v

Engine running & Genset running w/Univolt unplugged
Isolator
Input 14v
Both Outputs 13v
Batteries
Chassis 13v
Coach 13v

Engine Running & Genset running w/Univolt unplugged
with almost every inside chassis and coach accessory turned on
Isolator
Input 13v
Both outputs 12v
Batteries
Chassis 12v
Coach 12v

I think I can feel confident during our trip to Florida next week that we'll be ok if we leave the Univolt unplugged until we reach our destination. And then when we plug it back in and connect to shore power it will power our inside lights and charge the coach batteries. I believe it (Univolt) is not connected into the coach 12v distribution panel correctly. I am going to try and attach a photo so you can see how mine is wired. The drawing glued to the inside of the panel door doesn't even depict what my distribution panel looks like. The white wire from the Univolt you can't see in the pic must be common because it is grounded. The big red wire in the pic is the hot wire coming from the Univolt. Could you check and see how yours is wired and send me a pic. If anyone has a detailed wiring diagram of how this should be wired, I would apperciate it. Thanks, Kenneth

the pics actually are upside down from how they are in my coach


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Old 10-31-2012, 01:11 PM   #13
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I would check your fan belts. When I worked on auto electric systems years ago I had customers having the same problems with there batteries going dead if they used their lights. The belt did not sqweel. Check the belts
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Old 10-31-2012, 03:31 PM   #14
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My only electrical success story (actually my son's, he is the USAF trained electronics tech), not sure if it will help: we were having apparently random discharge/low voltage problems with our coach batteries, even after replacing. Found that several battery cables connect at a solenoid on the back of the battery tray. One cable terminal had cracked and would reposition itself every time the tray was opened and closed, sometimes making contact, sometimes not, sometimes shorting out. New cable terminal, and all is well.
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