Starting battery going dead!

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ChipSmith

ChipSmith

Well-known member
Joined
Aug 20, 2018
Posts
50
Location
Mid-Michigan
Need some help again, Gang! In our ?06 Four Winds 5000, we have put brand-new properly rated batteries in both the house and starting batteries. After setting in the driveway, with the battery switch off, and every thing turned off, for three weeks; the starting battery is completely dead! After a jump-start and running idle for an hour, I checked the alternator output (14.11voltsDC) and the start battery is at 12.52volts static.
I plan on letting it sit for twelve hours and reading it again.
Like I said everything in the coach is shut down, if I have a drain on the start battery, it must be in the ?automotive? side. Any suggestions for common battery drains? (P.S. The headlights are manual and yes I shut them off)
 
I would take voltage readings on the house battery(s) at the same time as I took them on the engine battery.  It's possible that whatever device is supposed to isolate the two systems has failed and they are not separated as they should be.

As far as "everything" in the house being off, I understand the on some RVs, things like the CO and LP gas detectors are wired to bypass any battery switch and stay on all the time.  The LP gas detector in particular - if you have one - uses a lot of power.  It has to heat a certain component in order to work.  That's why you'll never find one that uses a 9 volt battery, it would kill it in a day.
 
We have one of these to keep the starting battery from going dead.  There may be similar products.

http://www.bestconverter.com/TRIK-L-START_c_210.html
 
Thanx, Guys! I?ll try your ideas. As an update, I performed a ?parasitic load test? (i.e. disconnected neg. lead and placed my fluke 87 btwn neg. lead and neg. post) it shows a load of 65millamp. Should be less than 30 after the computers shut off. Then proceeded to perform voltage drop test (with my other fluke 87)
Across each fuse in the under-hood fuse box. No significant result. I then pulled the same drop test on each fuse in the coach inverter fuse panel (my house battery is at 12.52volts also, thanx OP) no results.
Don?t know what to try next!
 
Mr. Optomistic,
Beautiful idea to check battery isolator! Any idea what it looks like or where it might be located?
 
Here are a couple thing to try. Disconnect the house battery and see if the drain persists. If it does disconnect the alternator. If the diodes in the alternator are bad you have a path for the battery to discharge. You can take the alternator to Auto Zone or similar auto parts store and it can be tested. Let us know what you find.
 
Thanx, SC! Those are my next steps tomorrow. I?m leaving the neg cable disconnected overnight to assure that my ?new? battery isn?t failing.
 
I had to put a trickle charger on my starter battery.

The RV manufacturer was too cheap to include this.

What this means is that the starter battery is trickle charged when RV is plugged into electricity. When it's not plugged in, the starter battery was charging off the house battery. So that the starter stayed charged up.  8)

I learned about this on the forum years ago.

http://www.lslproducts.net/index.html

I bought it and followed the excellent instructions to install it.


 
ChipSmith said:
Mr. Optomistic,
Beautiful idea to check battery isolator! Any idea what it looks like or where it might be located?
Click to expand...

Hard to say.  There are a number of different ways to do this. It might be a solenoid, it might be a diode box with heat sinks, it might be a more advanced solid state device.  If you go to Amazon and search on 'battery isolator' a bunch of them will come up and you can see what the different types look like.  Often located in the engine compartment, but could be located near the house battery(s)
 
Mr. SC,
You, sir, are a giant among men! I disconnected the house battery and the drain was still there. So with some difficulty I disconnected the alternator lead, and BINGO, the milliamp drain went to zero!
I?m googling the alternator removal now and will let O?Reilly check it in the store. Thanx again, everybody, you probably saved my winter excursion!
 
Keep in mind that occasionally batteries will just suddenly die.  I had one once that started fine one morning, I then drove to a gas station to fill up less than a mile away, filled up with fuel, and then went to start the car, and nothing, thankfully the gas station was next door to an auto parts store.  I walked over bought a new battery, put it in the car, and it cranked right up.
 
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