Battery drops from 12v to 10v overnight

[LJ-TJ]

Here's something. I'm still dinking around but. Yesterday I charge the Chassis battery to 12 volts today 24hrs later shes down to 10volts all on her own.?good,bad, I don't know. Hm?

[Arberg0]

well for what its worth i would say one of 2 things bad cell in your battery or you have a bad earth (which is Queen's English for a bad "ground").

[LJ-TJ]

Yeah I think I'll try a load test tomorrow. I'm going to figure out this darn electric thing or go crazy. STOP    I no I'm already driving you guys crazy.

[DaveVA78Chieftain]

Is this the coach or chassis battery?

What did you use to charge the battery?  Was it a standard automotive battery charger or the converter/charger in the rig?  If the one in the rig, is it the old one that came with it?

A fully charged battery at rest, after the surface charge is removed will read at least 12.6VDC.

10VDC is a sign of either a severly discharged or defective battery.  I would first remove the battery and charge it with a standard battery charger then see if it holds a charge 24hrs.  Even if you take it somewhere to be tested it has to be charged first.  Purpose here is determine if battery is good before getting caught up in looking for a parasitic load drawing the battery down.

Dave

[LJ-TJ]

Ok Dave I'm sucking it up. I'm going to do this even if I drive you guys crazy cause I'm already there. The battery is the chassis battery. I'll pull it tomorrow and charge it with a regular battery charger. By the way how long should one charge a deep cycle RV battery and what should the reading be once it's taken off the charger. Since we're talking about it. i??

Actually I'm going to go out right now and pull it and put it on the charger.

[jbmhotmail]

Disconnect battery and charge overnight, remember it has to be charged to do a load test, let battery rest (disconnected) for 8 hours. What is voltage now, if OK take battery in for a load test, if battery tests OK, then you have a voltage drop problem (see voltage drop on YouTube and that will take care of your problem.
Good luck and let us know how it turns out.

[DaveVA78Chieftain]

By the way how long should one charge a deep cycle RV battery and what should the reading be once it's taken off the charger.

Somehow I knew you where going to ask something like that   W%  Sorry to say it is not a simple answer which is why I use smart battery chargers so I do not have to jump through hoops to figure that out.  Remember you asked so here goes  D:oH!

Time is a function of how much energy is being drawn from or supplied to the battery combined with the battery condition.  Just as one light bulb only draws a small amount current, say 0.5 amps, a furnace blower can draw upwards of 7 to 10 amps.  Same thing holds true for different battery chargers.  You have small chargers that only provide 5-6 amps (like many of the old linear converters) up to chargers that provide up to 150 amps.  The higher it can provide, the quicker it can recharge.  However, while I wish it was that simple, I am sorry to say it's not.  The engine alternator, old style Linear converter, and manual automotive battery  charger all use the same principle of operation.  They set the charging voltage to a set value then adjust the amperage rate to maintian that voltage.  As the battery state of charge (SOC) increases the amount of amperage that can be pushed into the battery decreases bacause the internal battery resistance increases.  Simple ohms law; if voltage level is to be maintained (i.e 14.1VDC), then amperage must be reduced if the internal battery resistance increases as the SOC increases.  With a manual battery charger, you monitor the amperage rate until it drops down to zero (this is why I monitor both voltage and current of the house system in my rig).  Now, when you turn the charger OFF there is a surface charge left on the battery because it was charging at say 13.6VDC and 14.8VDC depending on charging source.  This has to be bleed off either by time (the 8 hr value jbmhotmail reffered to) or by placing a load on it for a few minutes (i.e headlights).  Once the surface charge is bleed off you can measure SOC using a voltmeter:


Load testing is simular (once the battery is fully charged) but they use a larger load and make sure the SOC voltage does not drop of adversely.

Now just as the length of time a battery will last is measured in AH, the length of time it takes to recharge is dependent on :
1) How big is your charging device: A 5 amp charger will take 8 times longer than a 40 amp charger
2) What is the charging voltage and is this just a linear charger or is it a smart 3-stage charger?  A 3 stage charger has a boost mode that keeps the amperage rate up high until the battery reaches about 90% SOC.  At that point it reverts back to a linear based charger (exactly like the one I described above) to complete the last 10% SOC of charging.   The boost mode just allows the charging cycle to complete faster becasue the amperage rate is kept high for a longer period of time.  The linear charger above is always ramping the current down which results in it taking longer to recharge.  The 3 -stgae charger then rverts to float mode which maintains the battery at 100% SOC using a much lower voltage.  It is mainly the charger voltage level that can cause a battery to boil dry (older converters remained at 13.6VDC which is to high resulting in high battery water evaporation/boil off)

So, as I hope you can see, you have to know what is the set of  requirements for charging, then also know what are the requirements for determining battery condition.  For charging, I have a 3-stage PD9260 converter in the rig (4 100AH batteries in parallel) and a smart 3-stage B&D BC40EWB automotive charger around the house



B&D bought out Vector Mfg and their chargers are based on the Vector design.  My orginal Vector lasted 15 years.  I have had the B&D for a few years now.  I use it on lawn mower to deep cycle batteries plus engine start.  Being a smart charger, when battery is fully charged it shuts off.  If you leave it connected to the battery it will monitor the voltage and operate in a float mode.  When first turn it on it "tests" the battery condition to see if it can even charge it.  However, if the battery is completly drained like you 10VDC one, then it may not work at all.  Sometimes I have to use a older manual style charger to get a bit of energy into the battery before the fancy one will work.  However, that may also mean the batter is no longer usable.  I had to learn the hard way that my lawn mower battery needs to be topped of every couple of months in the winter.

Dave

P.S - This is basic stuff that at some point or another, every RV owner or backyard mechanic has to get a grasp of if they do not want to drive themselves crazy.  The confusing part is the difference between charging requirements vs battery at rest requirements.  Far to many people try to mix the 2 together.

[LJ-TJ]

 :)rotflmao Dave,Dave,Dave, Yeah No's we loves yeah! We also know nothing is simple with you. But we also know we'll get a great answer from you if your around to catch the question.  :)rotflmao

[Arberg0]

Funny thing is, I was looking into all the papers I got with our rv when we bought her, books and the likes - service repair sheets, and came across one where they could not find out what causes our batterys to drain.  I always thought it was because it was due to my step daughter turning everthing on when we got her and not telling me, including the fridge and ac but now I wonder.  Will recharge her as the batterys are dead and I want to work on her so will plug her into the garage for now and see whats working.  Time to find my old tounge tester and test cables to see what is drawing when its shut down .

[DaveVA78Chieftain]

I tried to avoid the answer but you would not let me!
It is simple once you understand shall we say the different modes of operation.  Ask Kevin, he knows!  Unfortunantly, due to many varibles, there is no single answer so I have to ask questions to understand what the baseline is to start from.  For every AH you use you have to push approx 1.25AH back in.  Thonk that one around for a bit

Dave

[Arberg0]

In other words, you dont get something for nothing.  You have to push that for those who don't understand AH (amp hour) that extra .25 to get back the 1 from the start .  Hell, this takes me back to ohms law and elect school 35 years ago.  Will have to dust off the books and some of my test gear.  Knew I kept it for a reason and brought it from the UK when I moved.

[ibdilbert01]

A GREAT site that might help!

http://www.marxrv.com/12volt/12volt.htm

[LJ-TJ]

OK were down to the short strokes here. No laugh'n at the end of this. Now! I went out today and the first thing I did was check the Chassis Battery after a full charge which was 14 Volts and after 24 hours she then had dropped down to read 13 Volts.The House Battery which is a deep cycle trolling battery from Wal-Mart full charge little green dot showing 14 Volts. and after 24 hours went down to 13 Volts. Went in sat down in the drivers seat looked at the Volt Meter and she read zero. So all good.  Started her up and went out and measured the volts on the Battery Cables and she read 14 Volts.

With the Engine NOT RUNNING and the Key OFF
With the NORM/DUAL/MOM switch in the NORM position the Volt Meter showed at rest both in the MAIN and AUX position.

With the Engine NOT RUNNING and the Key OFF
With the NORM/DUAL/MOM switch in the DUAL position the Volt Meter showed at rest both in the MAIN and AUX position

With the Engine RUNNING and with NO Shore Power or Generator running.

With the NORM/DUAL/MOM switch in the NORM position the Volt Meter read between 14 and 15 Volts. and showed at rest in the AUX position.

With the NORM/DUAL/MOM switch in the DUAL position it showed 14 to15 Volts indicating that both the Chassis Battery and House Battery were being charged.

NOW

With the Engine NOT RUNNING and the KEY OFF and the Unite Hooked to the SHORE POWER or GENERATOR

With the NORM/DUAL/MOM switch in the NORM position should show the Volt Meter at rest in the MAIN position and Charging off the converter how ever there was NO charging showing. The Volt Meter shows at rest.

With the NORM/DUAL/MOM switch in the DUEL position the Volt Meter still shows at rest as well as at rest in the AUX position.
Anybody have any thoughts on how to fix that?
Yeah want to know the killer out of all this? After all the fart'n around now all the dash gauges work. Yep! After all the pull'n and pok'n around when I fire the old girl up the Oil Pressure gauge, Amp Gauge, Water Temp gauge Started working. The fuel gauge would only go to half full though. Well that's that. Thanks for all your help. If anyone has any thoughts why the Volt Meter wont show a charge when on Shore power I'm open to ideas. The converter says it has a 3amp charger on it.

[DaveVA78Chieftain]

Your tests say the dash switches and voltmeter are working correctly.  Your Aux relay is working correctly and your engine alternator is charging.

Your last test:

With the Engine NOT RUNNING and the KEY OFF and the Unite Hooked to the SHORE POWER or GENERATOR

With the NORM/DUAL/MOM switch in the NORM position should show the Volt Meter at rest in the MAIN position and Charging off the converter how ever there was NO charging showing. The Volt Meter shows at rest.

Set NORM/DUAL/MOM switch in the NORM then forget the dash stuff (it's working correctly).  Sounds like the converter is not putting out charging voltage.  The PD-694 manual says there are to leads from the converter to the battery.  Are both leads connected?  Is the PD-694 Trans-Batt switch in the Trans position?  Using your portable voltmeter do you see charging voltage (from the converter) at the battery itself?  See if there is a voltage difference between different positions of the Trans-Batt switch

At house battery itself
Shore connected / Trans position = ? VDC
Shore connected / Batt position = ? VDC
Shore disconnected / Trans position = ? VDC
Shore connected / Batt position = ? VDC

Looking for around 13.6VDC (indicates charger is working).  If all 4 readings are basicly the same the charger is toast.

Dave

[LJ-TJ]

Well Dave looks like I'm closer to buying you that Beer. In answer to all your questions. NO. Nothing actually when I put the switch to battery the volt meter dropped to 12 volts so my guess is that the charger portion of the converter isn't working when I'm on shore power or generator.
One quick last question. I know there are know quick questions. Is there any trick to getting my gas gauge to read full. Thanks for all your help. I'm going to give it a rest for a while or give you guys a rest for a while. W%

[DaveVA78Chieftain]

outside hunch is either the instrument cluster voltgae regulator (VR) is fading away or the float in the tank is giving up the ghost.  Use CW Search feature using "fuel gauge".  Several related posts.

Also:
http://www.mywinnebago.com/classicw/Fuel%20GaugeTrouble%20Shooting%20%20'73-'75.pdf
http://www.allpar.com/history/mopar/electrical2.html for a nifty upgrade.  I think JD did this.

I know, I know, always so much to read!   :)rotflmao

Sender - 61 to 85 ohms ‘empty’, and 8.6 to 10.6 ohms ‘full’ or there bouts
69-73 (old style dash) the VR was built into the fuel gauge.  74 up (new style dash) the VR is mounted tothe rear of instrument cluster.

Dave