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les marston (Les_marston)
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Posted on Tuesday, June 08, 2010 - 6:31 pm:   

I am looking for suggestions on where else to look for a drain on the house batteries.
I have turned everything off and eliminated anything that I can think of that would draw power from the house batteries. i.e. clocks, lights, T.V. / VCR.
Problem is that unless I completely disconnect the cables from the house batteries they go flat after only a few days.
Batteries test good. (both voltage and hygrometer).
I have tried to disconnect each circuit individually to locate the drain but have not been able to isolate the problem. Any suggestions?
Thanks
Les
Steve "Spanky" Aune (Spanky77707)
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Posted on Tuesday, June 08, 2010 - 6:56 pm:   

les, sounds like you have a short somewhere...?
Don Fairchild (Don_fairchild)
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Posted on Tuesday, June 08, 2010 - 7:26 pm:   

les,

Did you check the inverter, (IF you have one) if it is on even at idle it will drain the batts in short order.

Don
David Evans (Dmd)
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Posted on Tuesday, June 08, 2010 - 8:18 pm:   

Good, i thought this was a political rant! When you remove the battery cable and retouch it to the battery post do you get a fat spark? You can also attach your voltmeter between the cable and the battery and get a reading. try to keep isolating/disconnecting items (dash switches and controls for instance) till you can see where your problem is. Get the significant other a nice stool to sit on and get them to watch the meter reading as you do your dissconnecting/isolating things. Good luck and if you dont have one now is time to start your electrical notebook and take notes as you go along.
les marston (Les_marston)
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Posted on Tuesday, June 08, 2010 - 8:50 pm:   

Sorry. no politics!
I did check the inverter and it is shut off. Can it still draw DC when turned off?
I don't get an ark when I reconnect the house batteries.
I am using a digital volt meter to try to find the draw but it doesn't seem to change at all no matter what I disconnect.
I would think that a short would make heat even if it is just a small short.
The electrical note book is a great idea. I keep a fuel and maintenance log so this will be just one more bit of info for the future
Is it possible to have a bad cell in one battery, still have 12.75 volts and a good specific gravity? in all cells?
I hate these kind of problems that just defy logic.
Les
Moe Hollow (Moehollow)
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Posted on Tuesday, June 08, 2010 - 9:36 pm:   

Just so I understand here. Have you removed the + and _ cables from that bat bank to see what happens? If not, that will be necessary to see if the bats drain when there is no possible load meaning there is a battery problem. If the batteries remain good disconnected, add one load at a time and see what happens to the bank. Also, your multimeter should be able to measure an amperage draw for each individual circuit.
David Evans (Dmd)
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Posted on Tuesday, June 08, 2010 - 9:48 pm:   

Les you might need to do a load test on your batteries. and yes you can have just one bad cell. but remember you said if you totaly dissconnect the batteries they dont run down? In how long of a time are we talking? how many batteries 6 or 12 volt? Does your invertor charge the batteries when plugged into shore? I put a on/off boat switch from my batteries to my invertor 12vpositve lead just in case i needed to make sure it was off. The west coast guys should be checking in soon with more advice for you. My electrical notebook has saved me many times!(mostley from myself)
Jack Fids (Jack_fids)
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Posted on Tuesday, June 08, 2010 - 9:57 pm:   

Just a tiny FWIW...
My 4106 came a little cheaper than asking price because they couldn't keep a charge in the batteries, even with new ones installed....zippo in 48 hours or so.

4106's have a cockpit/driver's light mounted above and behind the driver.
2 weeks after I bought it I discovered that the light was a 2 wire arrangement,
the switch was broken......AND those wires had been REVERSED!

Guess where the juice was going.

A broken $5 switch & a miswired driver light
plus a lazy mechanic equalled consistently dead batteries
AND
almost a 20% discount from the price we had agreed upon,
because I was willing to take in in "as is" instead of "working"condition.
Sometimes an electrical short can a royal PITA,
and others it can put money in your pocket!
George M. Todd (George_todd)
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Posted on Tuesday, June 08, 2010 - 10:37 pm:   

Les,

A short would make heat, and burn where it is, so that's not it.

TVs and VCRs have a radio/infrared receiver in them which stays on all the time, so you can turn them on from the remote. They must be unplugged to stop the drain. (I know, they're on 120, but...)

How is your house/chassis system set up?
Do you have a LP/DC/AC fridge? (They take a little 12V for the brain all the time, and more if they have a 12V element, which they will go to if no 120 VAC available.)

If you are charging your house batts with a seperate alternator, it may have a leaky diode.

The suggestions above to look for a spark when re-connecting loads are right on, touch each wire you take off to the terminal, and look carefully for a small spark. You should also read 12 1/2 volts between the batt terminal, and the cable, when you disconnect it, if something is "on." When you find the offender, the reading will drop to almost zero.
G

(Message edited by George_todd on June 08, 2010)
les marston (Les_marston)
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Posted on Tuesday, June 08, 2010 - 11:47 pm:   

I have removed the cables from the house batteries( 2x12 volt) and the batteries remain at about 12.70 to 12 .75 volts
Because the batteries are charged thru a new solenoid from the alternator and from the manufactures inverter when plugged into shore power it is a bit hard to pull each end use off individually.
What I have done was to make sure that I don't have anything that is parasitic. and I have pulled all of the fuses out of the dc distribution panel one at a time to see if I can get any voltage change then repeated by monitoring voltage as I put them back in one at a time. again no difference.
My volt meter is digital and reads to 2 decimal places so even a small voltage drop would be measurable.
I toyed with the possibility that I had an intermittent short across the bottom of one cell in one of the batteries but I don't measure any significant difference in the specific gravity or voltage output on either battery nor can I thru shaking, tapping or holding my tongue just right get it to fail.
I think my next step will be to get a good inline DC amp meter and check to see how much draw is occurring then again do the disconnect one at a time thing.
George.
Your idea of the leaky diode has merit but because it is the same alternator that charges the house and start batteries and I don't seem to be having the same problem with the start battery it sort of rules that out too I would guess.
Please keep the ideas coming.
Just watch this turn out to be something simple like the fellow who couldn't start his coach then discovered it was in gear and park break set.
thanks
Les
Luvrbus (Luvrbus)
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Posted on Wednesday, June 09, 2010 - 12:03 am:   

I just went through this after looking and checking for a week a guy stopped by to visit and made a comment on how he liked my lighted door bell it'll be something simple
Sean Welsh (Sean)
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Posted on Wednesday, June 09, 2010 - 3:27 am:   

Les,

Small-current drains, or "phantom loads" as they are called, are usually so low-power that you'd need a voltmeter that read to five or six significant digits to see any effect on voltage. You will not find your ghost that way.

What you need is an ammeter. Many VOM's have an amp setting good for up to ten amps, which is probably more than what you are leaking. If yours doesn't, I've seen them in the hardware store for ~$15. Just make sure you don't turn anything on that would draw more than that during your testing, or you will blow the fuse in the meter.

Disconnect the negative cable from the battery, and connect your meter on the 10-amp setting between the end of the cable and the battery negative post. If you read anything other than zero, you have a leak.

Now, as suggested, you can start disconnecting other wires while looking at (or having an assistant watch) the meter until something you disconnect causes a drop. Note how much current drops for each wire disconnected, until you get down to zero.

The wire(s) responsible for the current reading on the meter will lead to your phantom load(s). As Clifford says, it will probably be something simple, like a courtesy light, or the memory backup for the radio, or whatever.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com
FAST FRED (Fast_fred)
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Posted on Wednesday, June 09, 2010 - 6:39 am:   

As well as drivers lights , some coaches had lights in the bays , that may not have been disconected , or set up properly.

FF
John MC9 (John_mc9)
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Posted on Wednesday, June 09, 2010 - 8:35 am:   

Don Fairchild = "Did you check the inverter, (IF you have one) if it is on even at idle it will drain the batts in short order. "

les marston = "I did check the inverter and it is shut off. Can it still draw DC when turned off?"

I think Don already gave you the answer, Les!

You can "prove it", using a volt meter as described in other posts,
or just disconnect it and check the batteries in a few days.

Turning it "off" doesn't solve the problem; disconnect it.
Austin Scott Davis (Zimtok)
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Posted on Wednesday, June 09, 2010 - 8:49 am:   

When trouble shooting electrical problems you have to do it logically, start at one end and work your way to the other end. if you start guessing and skipping around you will probably miss the problem.

I would start at the battery and work my way out.

1. disconnect the positive battery terminal

2. as stated earlier, connect your volt meter, one lead to the positive battery post and one lead to the cable you removed. If there is voltage you have something using power.

3. reconnect the cable and follow it to the next connection.

4. disconnect the connection and again connect your volt meter one lead to the cable you removed and one to the terminal you removed it from to check for voltage.

5. When you get to where the power splits and goes to several locations you must disconnect every line and use your volt meter to check every wire that splits off the main line. Whichever one shows voltage is the one that is under a load.


Keep working your way out following where the voltage leads you.



.
Buswarrior (Buswarrior)
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Posted on Wednesday, June 09, 2010 - 10:08 am:   

As noted, don't waste any more time trouble shooting until you confirm the inverter does not have a draw...

The inverter should have some form of protection, fuse/circuit breaker that you can use.

happy coaching!
buswarrior
Jack Conrad (Jackconrad)
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Posted on Wednesday, June 09, 2010 - 6:15 pm:   

I was taught by an old mechanic many years ago to remove the negative battery cable and put a test light (appropriate voltage bulb) in series between the negative cable and the battey post. A very small load may only make the bulb filament turn red but it will show any load. Start disconecting circuits until the light is completely out. Jack
les marston (Les_marston)
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Posted on Wednesday, June 09, 2010 - 9:45 pm:   

Well I am happy to report that the mystery is solved.
Turns out I had a 3&1/2 amp discharge through the shore power charging system. that is to say that when I was not plugged into shore power the house batteries were discharging through that charging system.
I have never run into this sort of thing before but the suggestion of bad diodes in the alternator made me think to check that charging system. Now with it disconnected from the batteries I get no discharge from the house batteries.
Thanks everyone for the help.
Les
George M. Todd (George_todd)
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Posted on Wednesday, June 09, 2010 - 10:18 pm:   

Les,

Thanks for the thanks, it really helps when we find out what was wrong. I'll try and remember to add leaky diodes in chargers as well as alternators!
G
R.C.Bishop (Chuckllb)
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Posted on Wednesday, June 09, 2010 - 10:55 pm:   

...and therefore?????....what is the "solution/conclusion/fix"?

I am only a "bus nut" ..not an electrical wizard.:-)

I think this entire thread has much application to my "problem" (see thread) of last week.

Thanx.

RCB
les marston (Les_marston)
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Posted on Wednesday, June 09, 2010 - 11:16 pm:   

Ah darn!
I was a little worried that someone would ask about the "fix"
As some of you know this is our little s&s motor home that we were having the problem with. our 102 is still a long way from ready.
the country cruiser came with a built in system to charge the house batteries and to distribute the 12 volt DC to each end use. This darn thing is located in the back of the motor home in about the most inaccessible place for someone my size.
I tore out the charging part of the unit and installed a smart charger to charge the house batteries.
Is this technically a fix? I don't know but for the time being it will work.
This old "stop gap" unit is a great teacher in how not to do some things in the coach.
Again thanks
Les
P.S. some of the guys here are very good at electrical... much better than I am so don't hesitate to ask questions it is a great way to learn
Les
Sean Welsh (Sean)
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Posted on Wednesday, June 09, 2010 - 11:16 pm:   

Les,

You could diagnose why your "charger" is discharging instead.

Or you can easily fix this with a solenoid, rated for the charger output, with 120vac coil. Energize the solenoid from shore power (or generator), and have it connect the charger to the batteries. Now when there is no 120vac incoming power, the charger will be out of the circuit and no more phantom discharge.

Depending on the output amperage of your charger, this should cost between $20-$80. I might have one lying around; give me a shout off-board.

-Sean
http://OurOdyssey.BlogSpot.com
les marston (Les_marston)
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Posted on Thursday, June 10, 2010 - 12:18 am:   

I thought about trying to repair the old unit but it only charged at 5 amps and was not regulated. It would continue to charge at 5 amps for as long as the shore power was plugged in. Hard on house batteries after a week or so.
The smart charger gives me as much as 25 amps and is very well regulated. It also got rid of a 28 year old, rather crusty wire unit that I had no faith in.
Not everything deserves to be repaired. sometimes it is better to go with newer technology.
Thanks Sean
Les
FAST FRED (Fast_fred)
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Posted on Thursday, June 10, 2010 - 6:54 am:   

Not everything deserves to be repaired. sometimes it is better to go with newer technology.


This is especially true with chargers (way smarter)

"converters " (crappy dumb chargers )

and inverters , where even modern cheapo's give a better output than the early units.

FF
R.C.Bishop (Chuckllb)
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Posted on Thursday, June 10, 2010 - 9:06 pm:   

"Les,

You could diagnose why your "charger" is discharging instead."

Would you be kind enuf to expand (embelish/detail,etc) on that Sean.....not privileged, I ass u me... :-)

Thanx.

RCB
Sean Welsh (Sean)
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Posted on Thursday, June 10, 2010 - 10:33 pm:   

Sure, Chuck.

Les wrote that the current drain was happening in the connection to the charger. I was being tongue-in-cheek when I wrote that he now had a "dis-charger", but, in reality, the charger is in fact causing the discharge.

That's probably indicative of something wrong, although certain inexpensive chargers are known to do this even when working properly. So I suggested he could either work on figuring that out, or just put a disconnect relay in.

Does that clear it up?

-Sean
http://OurOdyssey.BlogSpot.com
R.C.Bishop (Chuckllb)
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Posted on Thursday, June 10, 2010 - 11:09 pm:   

No.....:-)

What in particular, regarding the "something wrong"? Some how that seems like a ...uh...well..."no brainer"...(as they say from time to time...kinda like checking to see if the thing's in gear B-4 one tries to start the engine...)

Me thinks I have X-actly the same situation....and relates to what I wrote in an earlier thread.

AND, not being an E-Lectrical-Gu-RU... not sure how to GO about Korrect-ting it!...????

Mine is a Trace...inexpensive?... I don't know, but, never-the-less, still have a "problem".... "different" reading ...much less...than the batteries actually show on direct reading.

Thanx...again!
RCB
Sean Welsh (Sean)
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Posted on Friday, June 11, 2010 - 12:19 am:   

Ah. OK.

Without going into too much detail, a charger consists of a transformer, which steps the 120vac down to ~14vac or ~28vac (don't remember whether you have a 12v or 24v system).

That lower AC voltage then passes through a bridge rectifier, which "flips" half of the AC sine wave, so you have now a DC signal that looks, on a scope, like a bunch of humps.

Depending on the quality and type of charger, there will be some number of capacitors and possibly inductors and resistors in the circuit to smooth this humpy signal into something closer to a constant DC voltage.

In low-grade chargers, things probably stop there. This signal will be fed directly to the batteries. In better chargers, there will next be some kind of feedback circuit, probably transistorized, which regulates the output to a specific voltage. In the case of multi-stage chargers, the output will be regulated to different points based on the stage of charging; often this is achieved by microprocessor control.

The feedback circuit is monitoring the battery or output voltage at all times, and the microprocessor circuit, if any, is too.

When AC input power is removed from the unit, the monitor circuit and microprocessor continue to draw power from the batteries.

Chargers at the lowest end, with no monitoring at all, will not draw any current when the input power is removed, because the DC circuit can not pass the bridge rectifier in the reverse direction. Likewise, the highest quality units will have either a relay or microprocessor-controlled SCR or similar to disconnect most of the circuitry from the batteries when AC power is absent (although many units will still draw a tiny "phantom" current to run the microprocessor itself, which likely controls the front panel, monitors for AC presence, etc.)

It is the middle-of-the-road units, with regulated output but no advanced control, that will draw the most current when no input power is present. The simple solution is to add the $10 part that the manufacturer did not -- a relay to disconnect the batteries from the charger when the input power goes away. Bear in mind that units with parameter memories or soft-touch controls may not work right if this is done.

OK, does that answer your question?

-Sean
http://OurOdyssey.BlogSpot.com
marvin pack (Gomer)
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Posted on Friday, June 11, 2010 - 8:00 am:   

Good Post Sean!! You are da man!! Thanks

Gomer
les marston (Les_marston)
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Posted on Friday, June 11, 2010 - 11:01 am:   

Bet that helped.
I think that the rectifier in the old charging unit had failed allowing D.C. power to return to the transformer. Not sure what would happen to that current from there but needless to say it was wasted.
The Trace inverter is a very good unit, (not a cheap piece of junk)
could be but not as likely to be the reason your house batteries are going flat.
R.C.
try disconnecting the inverter from the system and see if the house batteries still go flat.
If they don't then the inverter is possibly the problem.
If they do then the inverter is not the problem.
The inverter will make A.C. power if you are not plugged into shore power. If you have any AC appliances plugged in then the inverter will try to power them.
Some things draw power even when they are turned off!
A small AC draw on the inverter = a much greater draw on the batteries.
My Trace inverter has the ability to shut itself off when the batteries are drawn down to below a set voltage. I would assume yours does too.
Sean and some of the other guys here are VERY good at diagnosing inverter and other problems but they need details.
Try the tests that I suggest then post the results. I am sure that the problem can be found and corrected.
I hope my little electrical problem and solution helps you over come yours as well
Les
Sean Welsh (Sean)
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Posted on Friday, June 11, 2010 - 11:19 am:   

Les,

If your rectifier failed, say by having one of the diodes start passing current in both directions, then you would also see charging problems, because the rectifier would not be doing its job.

If that did happen, though, to answer your question, that would allow the circuit from the batteries to be completed through the transformer secondary. You won't get any output backfed at the primary (120-volt side), because transformers won't work on DC, but with the circuit completed, current will flow and all the parts will heat up a bit, especially the transformer, which is were the energy lost from the batteries is going.

Inverter/chargers are special cases. Unless the inverter portion is completely turned off, the inverter itself will always use a small amount of "idle current."

Top quality inverters have a way to minimize idle current, by waking up every few hundred milliseconds or so, checking for load, then going back to sleep. Only if a load is present do they energize the output. If you do have phantom loads on the inverter output, such as that clock on the microwave, then a load is always present and the inverter will stay energized full-time.

-Sean
http://OurOdyssey.BlogSpot.com
les marston (Les_marston)
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Posted on Friday, June 11, 2010 - 11:30 am:   

Thanks Sean.
I hope R C can find and correct his problem as well
Les
R.C.Bishop (Chuckllb)
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Posted on Friday, June 11, 2010 - 6:55 pm:   

Gotcha....and thanx for the continued "support" from all.

But, I don't want to hijack this thread....so, I'll post what is going on on the thread I started a couple of weeks agp, so look "below." :-)

RCB

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