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Born2travel

I need help finding a electrical gremlin

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When in storage I have had a problem with my house batteries losing their charge. 

The first few times I only removed the negative cable. But with grounds everywhere I moved the blade switch to the positive side. Still after a few weeks they are down.

I turn the salesman switch off. The chassis battery is switched off (it behaves). I can't find anything easy to check that has power. It was suggested a battery had a bad cell. A load test showed the batteries were in great shape. I have probed, tested, shut off everything I can think of. Now while it isn't horribly difficult to remove the positive and negative cables it is very puzzling, and has become a quest. Obviously when on shore power or driving it isn't an issue. 

Any electrical gremlin hunters out there who can cause me to slap my forehead with the palm of my hand? How can power leak when the powering side isn't connected?

 

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Back in the day (way back in the day), we had an method that help find gremlins in cars. We would put a volt meter between the positive battery post and the positive cable. The meter would show 12 volts. Then one by one we would pull fuses. Remove a fuse and if it still showed 12 volts, replace that fuse and move to the next. we would continue to the next one and so on till the meter went to zero. When the meter went to zero there was the circuit that was the culprit. It worked on cars, but have not tried it on a MH. You might try it and see if you can find your gremlin. 

Herman     

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18 minutes ago, hermanmullins said:

Back in the day (way back in the day), we had an method that help find gremlins in cars. We would put a volt meter between the positive battery post and the positive cable. ...

Herman     

If you have a battery monitor system (like the Victron BMV 712) installed you can use that in the same way. It will show any draw or charge going to the battery. Follow the same procedure Herman mentioned, and when you put in the fuse for the offending circuit a draw will show (unless the problem is intermittent or resulting from something which cycles on/off).

The key to using a system like this is to install the shunt so that ALL current to/from the batteries goes through the shunt. Otherwise you'll never get an accurate reading.

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Now a days, it's a circuit board & or the inverter...turn CB off on inverter might stop it...or back to Herman! :ph34r: 

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Richard, I agree if you have the Viatron BMV 712 in your coach you would be all set. However if you don't a BMV 712 cost $226.65 plus tax (free shipping). Plus installation. My method, you can buy a meter for $12.99 + T/Fgt. with 2 clip and a bit of wire. :rolleyes::wub:

I would like to learn more about the 712 to see how it works. It sounds like it would be a good unit to have. :unsure:

Born2, let us know what you find. I'm sure a lot of us would like to know so we will have a starting place should we have the same issue.

Herman

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2 hours ago, Born2travel said:

..... I moved the blade switch to the positive side. Still after a few weeks they are down.

 

Let's go back to this statement.

If. indeed ALL connections between battery and house are disconnected, chasing phantom draws would be unnecessary.  If battery drop in voltage is more than their self discharge rate, either they have a problem or there IS some connection to the house.

Also, a help if you tell us what coach you have/what batteries and converter or inverter/charger you have. Someone with your same coach may have experienced the same thing and be able to assist. Putting coach info in your signature means it is there on each of your posts.

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It is a Georgieboy on a P30 chassis of the 99 vintage. It is a poorboy rig but it has been solid. It has dual 24 (maybe 27) deep cells. The converter is in the "not sure" column as well because the RV is not where I am currently located. It works fine on shore power so I wouldn't think that would be in the loop. 

I didn't spell this out correctly in my original post. Can't you tell what I am thinking???? To be clear, I removed the ground. The batteries lost power over a few weeks. So then I moved the switch to the positive side. Leaving the negative connected and the positive side disconnected I still had a draw. If both were sides were removed the batteries held their charges. How can there be a phantom draw when only the ground is connected? Once I get my head wrapped around that...

I prefer Herman's option from a dollars and cents standpoint. The gadget Richard mentioned is intriguing.

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Yes, it is puzzling. Electrons need a complete path, returning to the battery in order to move.  But, the path can be different than just a wire.  Moisture, dirt, etc can allow small amounts of current to flow.

Have you insured that the tops of the batteries are clean and dry?

 

BTW, nothing at all wrong with an older P chassis Georgieboy-- many here on the FMCA Forum have fond memories of just such a coach.

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All that being said, Batteries will discharge on their own over a period of time when not in use, it's just the nature of the beast. Even new they can discharge while sitting on the shelf, however not as fast as when they are put into service. 

What you might try, clean the batteries(terminals and the top), Make sure they are fully charged, disconnect both the Positive and Negative cables and give it a week or two then check their voltage. You will see a drop in voltage, however if they are completely discharged then IHO you have bad batteries. If you can put a trickle charger on to maintain them you may get a bit more life out of them.

Good luck. 

Herman

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I have cleaned the batteries, the connections and anything else that looked dirty. The normal discharge happens when they are completely disconnected. down a bit but not crazy low. If just the positive is shut off and the ground is left connected is when they dwindle in a couple of weeks. 

Obviously, this isn't an earth shattering issue. One more wingnut and cable isn't killing me. It is just very puzzling. I have brought it up to fellow travelers over time and they don't have the same issue when they disconnect the positive side, of the ones who do this. It seems like this gremlin has my name.

This old girl has had us all over a great deal of the country. Every year we have one thing. Sometimes RV related and sometimes chassis related. Always one thing. And generally that one thing causes us to hear "I have never heard of that before" or "that can't happen." 

 

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What is actual voltage reading at the batteries after two weeks (or whatever time period you used) assuming starting from fully charged?

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They were down from 12.7 to 11.8. That was after between 3 and 4 weeks.  With only the positive disconnected it was down around 9.5 in two weeks. Again, I was told of a dead cell issue being the likely culprit but a load test showed they were in good shape, on two separate tests a year apart. The most recent being just before we placed it in storage a couple of months ago.

From a time standpoint I probably need to be replacing these batteries but with this issue hanging out there I am procrastinating. 

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You can have an internal bleed on a cell that will not show up with a load test 

fully charge battery's then separate and monitor voltage to see which one is the cause   

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1 hour ago, Born2travel said:

How can there be a phantom draw when only the ground is connected? Once I get my head wrapped around that... 

Only time I've seen that on otherwise good batteries was when there was LOTS of grime and dirt on the batteries, especially in humid weather.

Herman - The Victron BMV is really nice. I can watch what my system is doing from my phone through Bluetooth, and I'm able to see precisely what a particular device draws from the system if I want by isolating it. Once I got it calibrated, it was quite accurate regarding remaining charge.

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36 minutes ago, bm02tj said:

You can have an internal bleed on a cell that will not show up with a load test 

fully charge battery's then separate and monitor voltage to see which one is the cause   

That makes sense but it isn't an issue when both cables are disconnected. It only drains down when just the positive is disconnected. I would think that would eliminate the internal bleed possibility. But being an advanced tinkerer as opposed to a electronic wizard i may be wrong. 

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Those electrons have to have a path from the negative post back to the positive post. They're not going to jump through the air unless the humidity is really (REALLY) high, so something somewhere must be conducting the current for the battery to be draining. Also, any signs of cracking or damage to the battery case itself, especially near the posts?

Any chance you can post a photo or two of the way you've got things set up in your battery box?

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Richard, once I get paired back up with the RV I will get some pics. Also, I have searched high and low for cracks, swelling, low fluids, folds, bends, spindles and mutilates. I didn't see anything. My seeing eye dog didn't see anything either. I think my electrons are pole vaulters.

Herman, I will follow your suggestion when I get a chance. Wouldn't they lose power all of the time? Meaning when both sides are disconnected there is very little voltage drop. Wouldn't a bad cell(s) cause the problem all of the time they aren't being charged in some way?

I will soon be released from my post surgical restrictions. Being a recliner ranger is fun for a couple of days. After that not so much.

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39 minutes ago, Born2travel said:

Wouldn't a bad cell(s) cause the problem all of the time they aren't being charged in some way?

 

Yes and no. A bad cell or weak cell can do strange things. Is there a way you can keep the coach plugged in when in storage. If so your inverter will act as a charger and maintain the charge in your batteries.

Sorry to hear you had surgery, hope you recover nicely and get back on the road soon.

Herman

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5 hours ago, bm02tj said:

You can have an internal bleed on a cell that will not show up with a load test 

The internal bleed spoken of is within the battery itself. Desulphation might be an option that can be in order to help stop the phantom draw. I have been successful in getting  an extended period of life by using this method. 

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You can also have some type of internal damage. The weight of the cable/clamp on the post is enough to cause a problem. Take off both clamps and the problem disappears. I've seen weird things with internal battery failure.

How old are these batteries?

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8 hours ago, hermanmullins said:

Fully charge the batteries and test each cell with a hydrometer. I'll bet you have a bad cell or several.

Herman 

Bingo! A load test may not detect a weak/failing cell.

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On 3/21/2019 at 4:11 PM, richard5933 said:

You can also have some type of internal damage. The weight of the cable/clamp on the post is enough to cause a problem. Take off both clamps and the problem disappears. I've seen weird things with internal battery failure.

How old are these batteries?

We fall into the category of - if something weird can happen it will happen to us. I can't tell you how many times we have heard "I have never seen that before."

The batteries are approaching 5 years.  I will soon be replacing them. But I would love to find the gremlin's hiding place first. As I said it is a quest at this point.

Once I get the answers I will follow up here. Many times I see threads such as this one that leave everyone hanging as to the outcome.

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When your able to look at your coach again, without discomfort, I would try Herman's fuse approach first...due to the age of your coach, you would not have all the high tech electronics we have now!

Also, since you can't follow up on any of the suggestions, we are all shooting blanks!  

Yes, we would love to have a feedback on this thread.

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