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Topic: Charging Batteries (Read 779 times) previous topic - next topic

Charging Batteries

Our new to us motorcoach has walmart flooded batteries for the chassis and gel batteries (two) for the house. It is my understanding that the engine alternator charges the chassis and house batteries through a battery isolator while the engine is running. It is also my understanding that while on shoreline or while the generator is running the inverter/charger charges the house batteries. There is a boost switch that when on combines the chassis and house batteries and therefore both chassis and house batteries are being charged by shoreline or generator. When the boost switch is on the inverter/charger is charging both battery banks which are of different battery types. Now, if the motorcoach had the original Optima chassis batteries they would be AGM types and therefore the inverter/charger would still be charging two different types of batteries when the boost switch is on. Now my question, Foretravel knew this when they built the motorcoach. Why would they install two different types of batteries? Unless for the short time that the boost switch would be on it would not really make a difference. Thanks. Larry
Larry and Terry
Ex 2004 U270 36'

Re: Charging Batteries

Reply #1 –
I had gels as chassis in 01.
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: Charging Batteries

Reply #2 –
The boost solenoid is a "non-latching" type and while it is rated continuous duty, it also uses current in the "boost" position. It is used when the engine starter may need a few more amps in cold weather or other similar occasions but I don't think it is wise to use it in the application you describe. Cole-Hersee has constantly tried to upgrade the solenoid used in our Foretravels but it's reliability still leaves a lot to be desired. A shore power outage with the boost switch in the on position would quickly deplete the batteries if it lasted any length of time.

Foretravel never designed the boost switch to be used this way so a mix of different types of batteries is not a oversight by them.

A small trickle charger or solar panel connected to the engine batteries is the best way to keep them charged year around.

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

Re: Charging Batteries

Reply #3 –
Quote from: Pierce & Gaylie Stewart –
The boost solenoid is a "non-latching" type and while it is rated continuous duty, it also uses current in the "boost" position. It is used when the engine starter may need a few more amps in cold weather or other similar occasions but I don't think it is wise to use it in the application you describe. Cole-Hersee has constantly tried to upgrade the solenoid used in our Foretravels but it's reliability still leaves a lot to be desired. A shore power outage with the boost switch in the on position would quickly deplete the batteries if it lasted any length of time.

Foretravel never designed the boost switch to be used this way so a mix of different types of batteries is not a oversight by them.

A small trickle charger or solar panel connected to the engine batteries is the best way to keep them charged year around.

Pierce

I had a 1979 35' Foretravel eat an alternator far from home.  The boost switch was intermittent only.  No constant on.  Hmmm  Started the generac generator and put a toothpick in the switch to keep it engaged. 

Now what.  Oregon somewhere in the 80's.....look up and there was a Foretravel sign on a tree in front of me with an Arrow on it.  Followed the arrows to a motorcade rally and Foretravel had the parts trailer and two service guys there.  And they had the alternator and installed it for me.  Typical Foretravel luck.

We seemed to have someone looking out for us don't we?

Bob
"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

Re: Charging Batteries

Reply #4 –
Pierce,
I agree with you. However, the service advisor at FOT told me that when in storage it would be a good idea to turn on the boost switch a day or so every week or so to charge the chassis batteries. Larry
Larry and Terry
Ex 2004 U270 36'

Re: Charging Batteries

Reply #5 –
I use my boost solenoid to charge my cranking battery when I'm plugged in to shore power. It works fine that way. I leave it on all day long sometimes. I shut it off when I'm not home because if there's a power failure while I'm gone I don't want to discharge the cranking battery. The boost solenoid is only about $30 from Foretravel's parts counter as I recall, and it only takes a few minutes to change it if it fails. It's probably available for less than that on the internet. I never use my boost solenoid to crank the engine. The solenoid is only rated to handle 200 amps and I don't want to fry it. It would probably take well over 1000 amps to crank a Detroit Diesel with straight 40 weight motor oil in cold weather... If you really need that much amperage to crank the engine you can probably put a heavy gauge jumper across the isolator terminals temporarily, but remember to disconnect it after you get the engine started.
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: Charging Batteries

Reply #6 –
The voltage drops across the isolator and over the long lengths of cable eliminate any problem over-charging the gels in mixed battery applications.  If gels are used as chassis batteries, extra care must be taken in setting the alternator voltage regulator correctly.
Regards,
Brett

'99 42' Foretravel Xtreme
'14 Brown Motorsports Stacker
'05 Chevy SSR
'02 BMW R1150R

Re: Charging Batteries

Reply #7 –
I agree with Brett (the other Brett) in that voltage will drop INITIALLY to the gel batteries due to loss in long cables to house battery bank.  But, as amps decrease, there is less voltage drop, so after several hours of driving, voltage will test the same at both banks.

And, while there is around .6 VDC drop across the diode-based battery isolator, the sense wire on the chassis battery lug of the isolator compensates for this.  Said another way, by putting the sense wire on the "far side" of the isolator, it fools the alternator into putting out .6 VDC MORE than you want at the chassis battery.

Best answer is difficult to find on an RV, difficult NOT to find on an offshore boat.  And that is a SMART REGULATOR. Goes through bulk, absorption and then into float, just like your smart inverter/charger.  Here is the one we use on the sailboat:  http://www.xantrex.com/power-products/power-accessories/alternator-regulator.aspx

And because of voltage loss during high amp charging (i.e. running the boat main engine only to charge batteries), I have the voltage sense wire on the engine battery positive terminal.  So the battery sees full voltage, irrespective of line loss.

Brett
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: Charging Batteries

Reply #8 –
Quote from: amos.harrison –
The voltage drops across the isolator and over the long lengths of cable eliminate any problem over-charging the gels in mixed battery applications.  If gels are used as chassis batteries, extra care must be taken in setting the alternator voltage regulator correctly.
Yup.  When my alternator failed in Ohio, I drove all the way to Kearney, NE with the boost switch on and generator running.  Was 2-3 days.  When they put in the new regulator, it came from the factory set at about 15.1V and I didn't know better.  Since my coach batteries are Gel, I took it off and back to the shop to have it reset to 14.1.  No problem, and now I know better and will make sure they bench test and adjust it the first time.  BTW, on my ISL, one of the bolts/nuts to R&R the alternator required an 18mm socket. Go figure.  This seems to have kept my 14 yr old AGM starting batteries happy too.  Pro-sine 2.0 is also set to 14.1.
The selected media item is not currently available.Brad & Christine Slaughter
Was:  1990 U280 36'
Was:  2002 U270 36' (With a bathroom door) Build #5981
Is:  2021 Leisure Travel Van Wonder 24RL
2015 Jeep JKU, 2003 S10 QC 4x4 or 2017 C-Max
Lake Havasu City, AZ (or Gillette, WY)

Re: Charging Batteries

Reply #9 –
My ekectrical buddy I misquoted earlier mentioned the new coaches have two seperate systems to charge the chassis and house batteries.  No isolator.  Was not paying attention at the time so the exact details I do not remember but will ask.  Seperate outputs from the alternator?  Will ask more next week. 

My other ex Foretravel tech mentioned a transistorized isolator that will allow more than the 1volt difference in charging the two battery systems. Maybe I got that one correct also.

Both work on high lines only and one mostly brand new stuff for mc mahons Rv in so cal. 

I am getting closer after a lot of coach bucks to getting my coach to being up to date and reliable. 

Will see how many coach dollars to change the charging system to the new way and if its worth it for my uses and the inverter and off the grid solar as I get my lottery winnings.

My buddy showed me a customers prevost with ten panels and said it put out 25amps.  I think 24volt.  Four MK gels.  Two measured good. Two were bad.  9 years old.  Replacing all four.  Older female driver/owner.  Husband did not like rving so she took the kids and drove the bus herself.  22 years owner since new on a 91 le mirage xl. 

Both buddies are twenty year expensive motorhome/bus experts so its fun to have them work on the unicoach. 

Bob 
"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