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Chassis Battery Drain

New red tops installed for chassis batteries right close to a year ago.  Silver leaf generally shows 12.8ish on chassis batteries riding down the road.  It showed that from day one installing them.  I almost always use Boost to start and shut it back off.  House batteries are old and toast.  I'm working on replacing that whole system.  I have her at a detail place getting stripped naked of all vinyl.  It's sat inside for two weeks.  Went to start today and it tries to crank very little but stops.  Tried Boost and no difference (house batteries are probably toast).  Boost switch was not left on.  Put a NOCO GB150 on it but that did not work (it was half dead from sitting as well).  While it was on trying to help, it showed 11.8 then dropped to 11.5.  They will put it on a charger the next day or so.  I will take my F350 back with heavy cables to jump it.

What would cause the drain on the chassis batteries?  Anything else I should look for?  Thank you in advance.

 
Luke & Sandy (still many work years to go...)
1999 U320 36 Build #5387
2013 Jeep Wrangler Unlimited
Previous 1997 Winnebago Vectra Grand Tour 35WQ major interior remodel
Previous several SOB trailers, Class C, fifth wheels.

Re: Chassis Battery Drain

Reply #1 –
The chassis batteries may also be bad.  They should be at well over 12.8 VDC while driving-- closer to high 13's-14.2.

Have you measured voltage at the chassis battery with engine at 1100 RPM or so-- could be a gauge issue or could be a battery issue or could be an alternator issue or could be an isolator issue.

Not hard to diagnose, but sounds like it needs to be done.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Chassis Battery Drain

Reply #2 –
I went through it. I finally replaced the battery post clamp on connectors with brand new and that solved the problem. I didn't clean them, replaced them. Just sayin. If yours are permanently attached to the cables you are stuck with cleaning.
1994 U280, Build 4490
Deming, NM.

Re: Chassis Battery Drain

Reply #3 –
Quote from: coastalbuilder –
New red tops installed for chassis batteries right close to a year ago.  Silver leaf generally shows 12.8ish on chassis batteries riding down the road.  It showed that from day one installing them.  I almost always use Boost to start and shut it back off.  House batteries are old and toast.  I'm working on replacing that whole system.  I have her at a detail place getting stripped naked of all vinyl.  It's sat inside for two weeks.  Went to start today and it tries to crank very little but stops.  Tried Boost and no difference (house batteries are probably toast).  Boost switch was not left on.  Put a NOCO GB150 on it but that did not work (it was half dead from sitting as well).  While it was on trying to help, it showed 11.8 then dropped to 11.5.  They will put it on a charger the next day or so.  I will take my F350 back with heavy cables to jump it.

What would cause the drain on the chassis batteries?  Anything else I should look for?  Thank you in advance.

 
That's the biggest reason never to use the boost switch when starting the coach unless in an emergency. If it starts turning over slower, then use the boost switch. Now you have to bring your F350 back to start it. How bout if you were on the road somewhere? Did you try starting the generator and charging batteries that way?

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Chassis Battery Drain

Reply #4 –
Very valid reasoning. Thank you. It's inside a building so probably not ideal to start the generator. If it would have started....
Luke & Sandy (still many work years to go...)
1999 U320 36 Build #5387
2013 Jeep Wrangler Unlimited
Previous 1997 Winnebago Vectra Grand Tour 35WQ major interior remodel
Previous several SOB trailers, Class C, fifth wheels.

Re: Chassis Battery Drain

Reply #5 –
I will check the voltage at the battery at 1100 rpm.
Since silverleaf shows low voltage I assume it's not a gauge issue.
Probably time to start looking at alternator replacement anyway.
Luke & Sandy (still many work years to go...)
1999 U320 36 Build #5387
2013 Jeep Wrangler Unlimited
Previous 1997 Winnebago Vectra Grand Tour 35WQ major interior remodel
Previous several SOB trailers, Class C, fifth wheels.

Re: Chassis Battery Drain

Reply #6 –
And I'll check the battery post clamps when get it back home. I could make new ones if they are crimp style. Can't remember right now.
Luke & Sandy (still many work years to go...)
1999 U320 36 Build #5387
2013 Jeep Wrangler Unlimited
Previous 1997 Winnebago Vectra Grand Tour 35WQ major interior remodel
Previous several SOB trailers, Class C, fifth wheels.

Re: Chassis Battery Drain

Reply #7 –
Pretty easy to make up new cables/connectors for your coach. I noticed a 16 ton hydraulic crimp device here on the forum so I looked online and my 16 ton will arrive tomorrow. About $50 delivered with quite a few dies so you can crimp any size lug. YQK-300 16 Ton Hydraulic Wire Battery Cable Terminal Crimper Crimping Tool.... Buy welding cable and the copper lugs online or places like Tractor Supply. Heavy duty post terminals, shrink tubing and away you go for a fraction of the cost of custom cables.

When ordering, you have to be acquainted with the wire/cable AWG sizes compared to the metric size. Here is a chart so you can see how an ebay item compares to what you need.

Foretravel has the cable sizes listed on the schematics in our library. AWG=American Wire Gauge  MM2= Millimeter Squared.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Chassis Battery Drain

Reply #8 –
That was happening to me for a while too. It was frustrating for sure with all the new RedTops.

From what I understand there is some Parasitic/Phantom draw on our coaches, Keeping some systems alive? Could be wrong.

What I do now, is keep a NOCO Smart Charger on it while parked, (run an extension cord from the bay) and also I put one of those little LED Voltage indicators that plugs into the old cigarette lighter on the dash which also has a little LED segment Green/Yellow/Red, so at a quick glance, I can see if the starting batt's are OK.

Since doing this no Issues, (Year 2 of this setup)  I thought I was going to eat a whole new set of Batteries!
Prior 2003 U295  40ft  400Hp -Sold
2020 F350 Tremor - Sold
2021 Bundutec Roadrunner - Sold
2017 Airstream Classic - Sold that POS
2017 F250 - Sold
2019 Sprinter Van - Sold
2022 Winnebago Revel 4x4


Army Airborne Vet.

Re: Chassis Battery Drain

Reply #9 –
The parasitic drain on units with computers like your 1999 model will usually pull the batteries down in a couple of weeks when not plugged in or using a battery maintainer.
Jerry & Nanci
1999 U270 34'WTFI
2011 Malibu
A smart man knows what to say, a wise man knows when to say it.

Re: Chassis Battery Drain

Reply #11 –
Marine cable is fine strand, tinned and has a fire retardant cover.
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4