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Starting off house batteries only

Today I ventured to the backyard to inspect the Foretravel after a hard winter.
I knew the 3 Optima Red tops for start batteries were shot, there day was done last fall and I decided then that I would wait till spring to replace.
I wanted to start the generator and exercise it for a while, and try and start the engine using just the house batteries.
I first tried to start the engine, it barely turned over with the boost switch on. After about 5 seconds I gave it up. I then tried the generator and found it fired right up. My house batteries showed a 12.5v level at the dash monitor screen. The house batteries have been on the coach charger all winter (boost switch off).

Is it normal for the coach not to have enough battery power in the house bank (4 - 6V - T145 ) to turn the engine over alone (boost switch on but all 3 engine start batteries shot)?
1995 U320C SE 40'
Jeep 4x4 Commander - Limited - Hemi
"The Pack"  Yogi and Diesel our Airedales -  Charlie our Boxer/Akita mix. Gone but NEVER forgotten Jake our yellow Lab.
NRA Law Enforcement Firearms instructor - Handgun/shotgun
Regional Firearms instructor for national Armored Transp. Co.

Re: Starting off house batteries only

Reply #1 –
In my opinion, it is best to turn on the boost switch, then wait a few minutes for the chassis batteries to take some charge before starting the engine. I have found the chassis batteries, even when so bad off they cannot turn the starter, still can lend a hand when given a temporary charge.they cannot hold that charge for long, but benefit from being closer to the engine.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: Starting off house batteries only

Reply #2 –
Power from the house batteries will be limited by the wiring and the boost solenoid. The wires and boost solenoid will "boost" the power supplied for starting, but will be a fraction the power available from the direct wiring from good start batteries.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: Starting off house batteries only

Reply #3 –
Good (BIG! and short as possible) booster cables from the house batteries to the start batteries might allow you to start from house batteries. Another option is to physically move one or more house batteries to the start battery position and connect battery cables to the transported house batteries. If the start batteries are bad, they may be sucking power rather than helping.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: Starting off house batteries only

Reply #4 –
THANKS!
This was more of a "I wonder if" moment. NOT a true attempt to start the engine.
When it would not turn over the engine enough for ignition "I WONDERED" if It should have.
Sounds like this is normal.
I will go start battery shopping soon.
1995 U320C SE 40'
Jeep 4x4 Commander - Limited - Hemi
"The Pack"  Yogi and Diesel our Airedales -  Charlie our Boxer/Akita mix. Gone but NEVER forgotten Jake our yellow Lab.
NRA Law Enforcement Firearms instructor - Handgun/shotgun
Regional Firearms instructor for national Armored Transp. Co.

Re: Starting off house batteries only

Reply #5 –
Quote from: Lon and Cheryl –
THANKS!
This was more of a "I wonder if" moment. NOT a true attempt to start the engine.
When it would not turn over the engine enough for ignition "I WONDERED" if It should have.
Sounds like this is normal.
I will go start battery shopping soon.

You didn't say whether or not you had a trickle charger on the start batteries over the winter. Easy to install one at the buss panel as it has an AC outllet next to it to plug it in. No need to install a charger at the start battery location. Depending on battery compatibility, you can also make a 4 or 5 inch small wire gauge jumper to go from the house to engine batteries at the buss while connected to shore power during winter. Have to make sure to remove it before starting the engine. I did that if we didn't go anywhere for a few weeks until I bought a high frequency trickle charger for the engine batteries.

Take the factory 12V schematic and have it blown up. You can then easily see the reason the house batteries won't start the engine by themselves. The schematic has all the cable sizes as well as the codes at the ends.  Once you get aquainted with the wiring, it's easy to see the limitations.

Good idea to carry jumper cables in your toad or a car/truck at home. If the start batteries get low, it's easy (depending on the location of the start batteries) to just jump the coach running the toad for a few minutes before trying to start the coach. If the jumper cables are small gauge, just idle the toad for 15-20 minutes.

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

Re: Starting off house batteries only

Reply #6 –
The boost switch on my coach is rated at 200 amps. It will not start the coach alone as you just experienced. I have put a new groung and a wire directly to the starter as well and no longer need the boost switch to start.  In fact it turns over much faster then it did before even with the boost swith on.
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: Starting off house batteries only

Reply #7 –
With a dead chassis battery, as Tom mentioned a few posts back, don't try to start right away. Before you flip the boost switch get the genny running, this will then power your converter (battery charger) for the house batteries. Now, flip the boost switch, don't try to start yet, and let the converter charge all batteries for say 30 minutes.  Then with boost switch still on, try starting the engine.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: Starting off house batteries only

Reply #8 –
Quote from: prfleming –
With a dead chassis battery, as Tom mentioned a few posts back, don't try to start right away. Before you flip the boost switch get the genny running, this will then power your converter (battery charger) for the house batteries. Now, flip the boost switch, don't try to start yet, and let the converter charge all batteries for say 30 minutes.  Then with boost switch still on, try starting the engine.

Exactly!

Although the chassis batteries may be nearly dead, with maybe 30 minutes of charging, they can still add some Amps to what the House batteries can provide to the starter, even if their voltage is low.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: Starting off house batteries only

Reply #9 –
It might take more than 30 mins if they are dead.  Also if they are really low the batteries might be dead.
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: Starting off house batteries only

Reply #10 –
All six of my coach batteries are new, as is my towed car's battery, so I don't have much cause to worry, but that was not the case a few months ago. At that time, I started carrying a spare automotive battery and set of jumper cables in the house battery bay. Plenty of room on the floor and I can occasionally jumper it to the house batteries while on shore power to top it off. Still a Boy Scout...be prepared.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: Starting off house batteries only

Reply #11 –
Quote from: Pierce & Gaylie Stewart –
You didn't say whether or not you had a trickle charger on the start batteries over the winter. Easy to install one at the buss panel as it has an AC outllet next to it to plug it in. No need to install a charger at the start battery location. Depending on battery compatibility, you can also make a 4 or 5 inch small wire gauge jumper to go from the house to engine batteries at the buss while connected to shore power during winter. Have to make sure to remove it before starting the engine. I did that if we didn't go anywhere for a few weeks until I bought a high frequency trickle charger for the engine batteries.

Take the factory 12V schematic and have it blown up. You can then easily see the reason the house batteries won't start the engine by themselves. The schematic has all the cable sizes as well as the codes at the ends.  Once you get aquainted with the wiring, it's easy to see the limitations.

Good idea to carry jumper cables in your toad or a car/truck at home. If the start batteries get low, it's easy (depending on the location of the start batteries) to just jump the coach running the toad for a few minutes before trying to start the coach. If the jumper cables are small gauge, just idle the toad for 15-20 minutes.

Pierce

No, I pulled the plug on these batteries last fall. I milked them along for the tail end of the RV season here up north, by keeping a charger on them all the time except when driving. I knew there time had come but didn't want to buy new batteries only to have them sit all winter. I will buy new batteries soon (3, group 78).

I thank you all for answering my question, the house batteries alone can't be expected to start the coach with  out help from the engine start batteries.
I appreciate the advice about how to use jumper cables to use the house batteries to start the engine and where to tap off the power.
My house battery bank is located all the way up front in the bay just behind the drivers window. The engine start batteries are located on the passenger side rear just behind the right rear wheel.
1995 U320C SE 40'
Jeep 4x4 Commander - Limited - Hemi
"The Pack"  Yogi and Diesel our Airedales -  Charlie our Boxer/Akita mix. Gone but NEVER forgotten Jake our yellow Lab.
NRA Law Enforcement Firearms instructor - Handgun/shotgun
Regional Firearms instructor for national Armored Transp. Co.

Re: Starting off house batteries only

Reply #12 –
It would have been nice to have a de-sulfater plugged in over the winter to attempt to bring around the start batteries.

I'm wondering, if I'm the only one that carries a small generator? pc
 
S/W Houston 95" U320C SE/40' 
Build #4778  Cummins M11
Repairs & Covered RV Parking (BAO)
PPL is close..

Re: Starting off house batteries only

Reply #13 –
We carry a honda 2000 generator, have for years and use it, especially when I am baking bread, just enough juice to handle the convection oven.

Roland
1993 U280 4341
2010 Jeep Liberty
The Pied Pipers

Re: Starting off house batteries only

Reply #14 –
My coach came with a diesel gen so do not need another as I never use this one anyway!!
JohnH
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Starting off house batteries only

Reply #15 –
Quote from: Roland Begin –
We carry a honda 2000 generator, have for years and use it, especially when I am baking bread, just enough juice to handle the convection oven.

Roland

I have two 2000's one a companion so you wire them together and get 3200 watts of 30 amp 110 and a honda 1000. 

Belts and suspenders I guess. 

They came by in deals new
"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