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Old 07-22-2014, 04:52 PM   #1
Join Date: May 2014
Location: Elgin, Oklahoma
Posts: 40
Coach batteries draining

We just got back from our first trip in our new (to us) 2000 Safari Serengeti Cat 330hp. Since we purchased it I have replaced the xantrex 458 2k watt with a new xantrex 3k watt. Also 4 new trojan t105's. The trip was great back home to the Gulf coast. We parked next to my mom's house and plugged into her breaker box. Everything worked great. 5 days after getting home suddenly the batteries were dead. they read from 1.6 volt to 3.6 volt. The fluid was low but the plates were still covered. I added water and started charging the batteries one at a time on my work bench in the garage. The first two batteries would only get to 5.8-5.9v and the sears battery charger would only charge them to 42%. At 19% charge on the third battery the check battery light came on. I unplugged the charger and checked the battery and it was at 5.6v. I let the charger cool down because it was very warm. I then connected it to the 4th battery and all the charger said was check battery. I disconnected the cables and checked and the meter read -1.56v. Can anybody tell how this happened? Is the battery ruined? Would it have been bad from the beginning or could I have done something to reverse the polarity. Somebody please help me. We have another trip planned soon, and electrical is not my strong suit.
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Old 07-22-2014, 05:19 PM   #2
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put a big light bulb in series with the battery to limit the charge current and try charging it for a couple of hours. Make sure you have the right polarity connections and you should have more than 6 v at the charger. Fully discharged batteries can do weird things. Often they will come back with a slow trickle charge to get the chemistry working again. The light bulb is not critical as long as it is a 6 or 12 V automotive type. My favorite is an old driving light because it has leads. ;-) A 12 V bulb will be fine for that use with a 6 V battery.

FWIW the limiting factor on charging to capacity might be your bench charger. Once you get the individual batteries up to more than 10-20% charge then try the whole system in the MH.

FWIW2 you can speed things up by doing two at a time on the 12V setting on your charger. Connect two 6V batteries in series. You might still need the light as a current limit when you start off. jumper cable works to connect the two batteries. ;-)
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Old 07-22-2014, 05:19 PM   #3
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Hi Fishkc10boom,

Given your last statement, a couple of ideas.

How do you know the batteries were good when you started ("new to us")?

I believe all T105's are 6 volt batteries. Are you charging with a 6 volt charger?

Given the age of your RV, does it have a smart (multi-stage) charger? The old, dumb chargers can certainly ruin a battery bank but I think it generally takes a while.

What is the draw on the system when sitting unused (after getting home)? Most RV's have some phantom loads and will deplete the battery if not charged somehow or completely disconnected.
JD - Full timer out west
Missy - 1998 MCI 102-EL3
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Old 07-22-2014, 05:48 PM   #4
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Measured a minus voltage...?

That is not good.

Lead acid can reverse polarity if discharged too deep.

Get the batteries connected as 12 volt units and place a TRICKLE charger on them and let them soak a few days.

Measure voltage and see what you have.

A little trick is place probes of digital meter into the water without touching the plates.

Doing this you can check voltage if each 2 volt cell.

All should be very close.

Check also with hydrometer.

Need to verify the drains too.
Tony & Lori
1989 Country Coach Savannah SE
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Old 07-22-2014, 06:01 PM   #5
Join Date: May 2014
Location: Elgin, Oklahoma
Posts: 40
The guy I bought from had only owned it 3 years and the last 20 months of that was in storage. The battery bank was nasty, corrosion on everything and all of the batteries were bulging on the sides. I bought new trojan t105's from a battery place in Oklahoma City. They were new, not refurbished and fully charged.
I replaced the old Xantrex 458 with the Xantrex Freedom 3k watt. With a new panel that lets me select what it is doing, charging, inverting etc...
The battery charger is a new Sears Gold with both 6v and 12v and choices of trickle, fast, rapid and engine start. I am not sure this charger is good. The first one I bought died the first time I used it, and this one makes a lot of noise and gets pretty hot.
As far as the draw when it is parked I don't know. I have looked for a meter that will measure current draw, but everywhere I have been radio shack, lowes, HD, The person looks and me funny and has no idea what I am talking about. If someone could recommend one I would be very grateful.
I do disable everything on the inv/chg panel and well as look at the inv/chg in the basement to make sure it is off and cooled down. And I hit the remote switch by the door to turn off any 12v items that may still be on.
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Old 07-22-2014, 06:59 PM   #6
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Harbor freight digital from free to 8 bucks will work.

Or fluke or many others.

You need dc amp meter which is one function in most multimeters
Tony & Lori
1989 Country Coach Savannah SE
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Old 07-23-2014, 07:47 AM   #7
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You are over stressing the charger with the low battery condition. That is why it is running hot and making noise. To address that add a resistor or incandescent lamp in series between the battery and charger. I have used both and know they work. You probably don't have a high wattage 1 ohm resistor sitting around so go for the lamp. Some trickle chargers might work but the lamp trick works a lot better. Once the cell chemistry gets going the voltage will jump up to around 6 v then you can connect direct to the battery. It might take a few minutes, it might take an hour. What you are doing is providing enough voltage while limiting the current flow to protect the charger.

For checking battery voltage any cheap Digital Multi Meter will work. I have $200 meters and $5 meters. It is usually not worth pulling out the expensive stuff for a job like this. Most of the DMM's have a 10 or 20 A capability. Be careful with that as you can easily draw well over that. You are not ready to go there until after you get the batteries charged.

You will have parasitic loads. The question is whether or not something like the engine computer will get upset if you disconnect all batteries. You might be better off with a float charger (battery minder). I don't know about your diesel but my gasser works that way.

The House batterys should disconnect with the switch but of they do not there is a host of ways to do that by hand.
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