Skip to main content ↑ ↓
Topic: Keeping Engine Starting Batteries Charged (Read 1360 times) previous topic - next topic

Keeping Engine Starting Batteries Charged

Our 2001 U270 came with 3 Optima engine starting batteries. I replaced them with 3 larger ones about a year ago. We keep the motorhome at our place in the country and turn on the boost switch for around 24 hours about once a week. When I was gone for about 2-1/2 weeks the batteries showed 10.9 volts on my digital volt meter so I charged them overnight at 10 amps, AGM setting. A week later they showed 12.6 volts so I assume they are OK.
I realize that I could disconnect the batteries every time I leave but would prefer not to.
Is it OK to just leave the boost switch on all the time, except when driving or is this asking for other problems? Other suggestions are also welcome.
Thanks, Robert.
Rob & Di
2001 U270 34'

Re: Keeping Engine Starting Batteries Charged

Reply #1 –
There are some great previous discussions on the forum to get you started.  Search on trickle charger, Trik-l-start, battery minder as some of your search terms.  Another thought is to search for storage charging batteries since those words will turn up a bunch of relevant threads.

Boost switch should not be left on all the time because all you are doing is linking the 2 battery banks together.  If you lose shore power you will take down both sets of batteries.
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Keeping Engine Starting Batteries Charged

Reply #2 –
Yandina Combiner is what I used. I used the Yandina to replace the battery isolator.
1998 U270 34'

Re: Keeping Engine Starting Batteries Charged

Reply #3 –
Why not put a 20w solar panel on the roof for start batteries. I have been doing that for over a year and never a problem to start.
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: Keeping Engine Starting Batteries Charged

Reply #4 –
I am plugged in to shore power just like you, and I used to do the same by putting the Boost switch on once a week, but it is a pain and then walking through the snow etc.  So I fitted  battery maintainer on the engine batteries as have many others, see posts here today, and leave it alone.  Works well.
Speedbird 1.
2001 U320 Build #5865
Daihatsu Rocky Toad
VW Touareg
'82 F100 Stepside
Beech' Debonair

Re: Keeping Engine Starting Batteries Charged

Reply #5 –
I'm so dumb & lazy that I plug my charger into a timer set to charge for one hour a day. Saves me having to go out & turn anything on or hook anything up. It has worked for five years now and keeps the batteries charged and yet not over charged.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: Keeping Engine Starting Batteries Charged

Reply #6 –
Thanks for your suggestions. I leave my motorhome under it's carport, plugged in to 50 amp service with the auto start switch on and a full tank of fuel. The rural area where we store it is subject to occasional power service problems and I arrived there one time to find the generator running. We also use this 10 KW generator for powering the home appliances during power outages.
I'm thinking that the easiest/cheapest solution is to just use a small trickle charger.
Rob & Di
2001 U270 34'

Re: Keeping Engine Starting Batteries Charged

Reply #7 –
As long as you have a shore power setup I can recommend from experience the Amp-L-Start charge stealer 15 amp. $65. Using your boost switch means that solenoid is always on and that many batteries makes any charging system play to the best battery for    leveling charge and etc. The amplstart simply diverts some charging current from your inverter/charger and on its own levels off at correct charge level so overcharge doesn't occur. Easy to install. I installed mine in bedroom at foot of bed so it was not exposed to engine bay temps. Once it is installed you can rest assured your engine starting batteries will be ready to rumble any time you have been sitting on SP. The unit will also charge those batts if generator is running.
Every day is a gift
Bob and Pat
2000 36 U295 cummins 350hp
Coach has been sold thanks to MOT 11/2016

Re: Keeping Engine Starting Batteries Charged

Reply #9 –
I have Optima batteries and use the "Digital 400".  I run the monitor from the start batteries up thru the bed and mount it on the bed wall under the skirt.  Have been using it that way for 2 years.  No issues at all.
 John

OPTIMA® Battery Chargers |OPTIMA® Digital 400 and Digital 1200 12V Performanc...
John and Stacey Smith
Motorcade NO: 11973
1997 U295 CSGI 40'..Build No. 5036     
920 Watts on the roof..CAT Power w/fuel Inj. Programmer
2021 GMC Sierra AT4 1500
EX..2015 Jeep Wrangler Sahara
Ex 1990 U280 RSAI 36'..Build No. 3638

Re: Keeping Engine Starting Batteries Charged

Reply #11 –
I have used the Genius Battery Chargers on both my starter battery and my house battery for the past 3 years. I only connect the coach when it is going to be below freezing. Only $59.95 from Amazon. In MHO, well worth the money.
NOCO Genius G3500 6V/12V 3.5A UltraSafe Smart Battery Charger
'91 U240 GV / 36'
CAT 3208 w/Allison MT 643  4 speed
'10 Ford Flex

Growing old is mandatory
Growing up is optional

Re: Keeping Engine Starting Batteries Charged

Reply #12 –
Just finished installing Trk-L Start. Battery isolator right next to my chassis batts. Took coach battery power from isolator, ground to chassis and charge lead to chassis battery. Working great, when I add solar it will maintain start batteries automatically as well. Under $30.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.