Electical Question...Somethin Does Not Seem Right!?

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dlshunter

dlshunter

Well-known member
Joined
Jan 7, 2007
Posts
162
Location
Modesto, CA
I have a '99 Forrest River Wildwood TT with 2 12v parallel - wired so-called marine deep-cycle batteries (Energizer 27DC-850 it says on the receipt from pep-boys).  I bought the second one right after I bought the TT (almost 2 years) because I knew I wanted to run 2 in parallel to get allittle longer charge-life on boon-docking trips. 

On a recent 2-nighter during opening weekend of deer season, I inadvertanlty left the water pump on while away and/or during the night.

When I discovered what had happened, I soon found that with 1 small light on over the kitchen sink, I would turn the pump on, and the light would dim bad, WITHOUT the pump cycling...I would then turn the water on, causing the pump to cycle, but the light would not dim any further. I would then turn the water off...the light brightness (or lack there of) just stayed the same, until I would turn the pump off, then it would get brighter..alittle.

I always thought that the actual water pump switch just sent current to the pump more or less in a stand-by mode, and then the 12-volt current is only utilized when the pump actually cycles.

Is there something wierd going on?

How long should I leave it plugged into shore power for charging?

If I wanted to buy a generator, what would be my minimum output (to run the wife's necessities...microwave, toaster, hairdryer, curling iron...etc...) that can be handled relatively easily by one light-wieght guy?
 
If you want to get a good estimate on how long it takes to charge your batteries take a Voltage reading with a digital voltmeter. At 11.9-12 volts DC it's pretty much fully discharged. When the voltage gets up to about 12.7 it's fully charged. That reading needs to be taken after whatever your charging with has been disconnected for about 30 minutes to let the battery settle down. Also as you check your readings if the voltage drops down to about 13.2 after a while you have a so called smart charger. Leaving a non-smart charger connected all the time over charges the battery and decreases it's life. Normal charge voltage is about 13.7-14 volts dc depending on your charger.
 
How long to re-charge depends on your converter but the MINIMUM for a FULL charge is six to eight hours. It goes up from there and can easily be days.

Just out of coursity what is the total amp hours of those two batteries together (Add them).. You did not mention what size they are.

A pair of golf car batteries (Slightly taller than a group 27) in series (since they are six volt) = 232 amp hours, 116 usable (you should use no more than half)  Just to compare.
 
Your water pump is a demand pump uses no power unless it is actually running, i.e. water is being used. You could have a slight leak somewhere, though. You would hear the pump cycling from time to time if that's the case. The pump will also run continuously if there is insufficient water in the tank for the pump to build pressure to the point where it switches off.

Have you been checking the water level in the battery cells regularly? Charging with gradually deplete the water (boil it away), and with some chargers it can take only a week or so of charging to seriously reduce the level. If they are low on water, they will not charge and will not produce power. Refill with distilled water, covering the lead plates to about 1/4 " depth.

Check the water level in each cell and then charge the batteries for 24 hours. Then measure the voltage as Dick Bell described. If it is below 12.6v, you need to replace the batteries.  It is not unusual for a typical 12v battery to fail after two years of deep cycle use in an RV - the typical battery simply isn't designed for that kind of use.  If you get a true deep cycle it should last for several years, but expect to pay quite a bit more for them.
 
dlshunter said:
Is there something wierd going on?
Click to expand...
Yes, something wierd's going on and usually when something wierd goes on with 12 volt systems I look at the grounds closely. Usually find something that's poorly grounded.
 
OH GEEZ!!!???
I have done nothing to this TT except add a total kill switch to prevent power leaving the batteries when not in use.

I just over the weekend charged the system for about 24 hours.  I then unplugged from shore power, turned off the main power switch to preserve as above.

I just now went out to see if I couild duplicate what happened...with what appears to be a full charge, it does not occur now.

Maybe with so low a charge, just throwing a switch sending current down a wire made the lights dim?  Heck I dont know.

But I am going to check the water level this weekend.
 
Using a 900-watt generator, how long would it need to run to bring this setup to a full charge?
 
Using a 900-watt generator, how long would it need to run to bring this setup to a full charge?
Click to expand...
Impossible to say without more information. How far discharged are the batteries? What is their condition? Older, neglected batteries may never take a full charge. What is the DC output of the generator (amperage)? Or are you powering a converter from the generator to charge the batteries? If so, what is the amperage output of the converter?

Speaking about the lights going dim - is it possible that a previous owner installed a 12 volt "Instant Hot Water" heater that comes on when the pump switch is on? Or a 120 volt heater powered by an inverter that comes on with the pump switch?
 
dlshunter said:
Using a 900-watt generator, how long would it need to run to bring this setup to a full charge?
Click to expand...

I have a "1000 watt" generator which really means 900 watts continuous. I have a 40 amp power converter with the charge wizard so it thinks it's a three stage charger.

It takes about 3 hours to get from 50% to 80% charged.  It takes about three days to get to 100%.

Joel
 
I checked the battery levels today...one had cells that all together drank about 2-3 oz of distilled water...the other drank darn-near 3/4 gallon!!!!  I could not believe how much water boiled off during all those recharges...I will now make sure I do not charge for for than 24 hours at a time.

Now I will check them twice a year during the summer.
 
I see alot of amp-hours talk being mentioned.  I understand the concept from general chemistry...24 years ago...
About how much is burned with an occasional light or 2 on, the 12-foot slide going in & out once during a trip, the fridge/freezer (on gas) running, water pump used when necessary, heater only in teh AM to take any chill off of the inside air.

I usually only take 2-3 night boon-docking trips when fishing & hunting.
Its these trips I'm trying to maximize my batteries, of course.  (It's usually just me & another buddy or 2 ...wife & kids only go if full hook ups & TV & ...you get the idea)

I know there are alot of variables here, but could somebody shed alittle of their own experinces with similar set-ups?

2-12 volt group 27's are what I'm now using.
 
dlshunter said:
I checked the battery levels today...one had cells that all together drank about 2-3 oz of distilled water...the other drank darn-near 3/4 gallon!!!!  I could not believe how much water boiled off during all those recharges...I will now make sure I do not charge for for than 24 hours at a time.

Now I will check them twice a year during the summer.
Click to expand...

Now that is somewhat odd.  Clearly one battery is suffering the effects of over charging (The two most common causes of a battery boiling dry is either over charging or too rapid charging) and the other is not

You might wish to check and clean all battery terminals, ideally they should "Equalize" and all be at the same state of charge at all times.

It is also possible one battery is dying an early death
 
If I understand your original message, you added the second battery well after the first was bought, i.e. they are substantially different ages. That is frought with risk because the newer battery and the old one will react quite different to the load and to charging.  I suspect you are seeing the result of that.  Safest practice is to always change all the batteries at one time.

Now you have a dilemma - one battery is overheating during charge and probably has high internal resistance (sulphated cells and/or corroded internal connections). However, a shorted cell could also have similar symptoms when the shorted battery is in parallel with a better one.  I'd replace it, but to be safe you ought to replace the other one too.  Assuming the one that took the least water is the newest one (not a good assumption, so check it), you could gamble again and replace the other. If the one that took the least water is the older one, then I'd replace both.

You need to check flooded cell batteries much more often than twice a year.
 
I agree with Gary completely but would add that if you find one of them bad, replace both of them with true deep-cycle batteries. Those called marine/deep-cycle batteries are neither fish nor foul and while they may be somewhat better than a normal starting battery, they don't qualify as deep cycle by any stretch of the imagination.
 
When I discovered what had happened, I soon found that with 1 small light on over the kitchen sink, I would turn the pump on, and the light would dim bad, WITHOUT the pump cycling...I would then turn the water on, causing the pump to cycle, but the light would not dim any further. I would then turn the water off...the light brightness (or lack there of) just stayed the same, until I would turn the pump off, then it would get brighter..alittle.
Click to expand...

The pump motor won't shut off until it's built up enough pressure in the line to activate the cut-off switch.  Since your batteries were mostly discharged, the motor didn't have enough power to fully pressurize the line and stalled when the faucet was off.   Since it couldn't build up enough pressure to activate the cutoff, it continued drawing current until you turned it off at the switch.

In short, there's nothing wrong with your pump circuit.
 
Thanks for all of the input.
After 24 hours of charge, and then 24 hrs sitting with absolutely no drain...their was jsut enough to get the slideout moving, but very slow.

Afterr another charge, this time longer, and after about 3 days of sitting, very discharged.

These things are history (One is only 1 month older than the other, by the way)

Does it really matter which battery is connected to the main wiring of the TT?

I have had the pos. post of one battery connected to the pos wiring of the TT, then the neg post of the other battery connected to the neg wiring of the TT, then jumpers on each connecting pos to pos, neg to neg.

Is there anything technically wrong with this?
 
When replacing batteries I strongly recommend against replacing only one when there are two or more batteries.  Replace them all at the same time.
 
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