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Battery Boost

Can you leave the battery boost switch on from time to time when plugged in at storage to keep the engine batteries topped off?
Brian & Lisa Freeze
1996 U295 36FT Build #4914
Motorcade #18760

Re: Battery Boost

Reply #1 –
Don't know that you can't, but I would use a more KISS way of doing it that did not require the solenoid to be on 24/7.  Make a 1' pigtail from #8 wire with eyes at each end and go from one side of the solenoid to the other.  Electrically the same, but not using the solenoid AND if power ever goes out, you will not have the drain of the solenoid.

If the battery isolator is easier to access, you can span outer lug to outer lug.  Electrically the same-- connects the two battery banks.

Other options are a separate small smart battery maintainer OR smart "thief" device that charges the chassis battery when house bank voltage is high enough to indicate that it is being charged. Xantrex Echo charger is an example.

Most of us go with one of the latter two choices.
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: Battery Boost

Reply #2 –
Maybe a bit confused but recently I enquired about charging the house batteries here on the forum and was told on the forum if you are plugged into shore power and your inverter(mine is a magnum2812) is set to charge, and the inverter part not on, the house batteries would be kept charged. Is this not the case?  I do have a charger on the start batteries all the time...
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: Battery Boost

Reply #3 –
Quote from: dicksop –
Maybe a bit confused...I enquired about charging the house batteries here on the forum and was told...if you are plugged into shore power and your inverter...is set to charge...the house batteries would be kept charged.
Peter,

Not sure why you are confused.  What you state is correct...your HOUSE batteries would be kept charged.

The original question in this thread pertains to charging the START (engine) batteries.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Battery Boost

Reply #4 –
No, this leads to many potential problems. The boost solenoid is NOT a latching solenoid and draws juice when activated and because of this, it gets quite warm. If you lose shore power with the boost solenoid on, it will flatten both sets of batteries in a fairly short time. A nice bank of AGMs may not recover from this.

You can either do as Brett posts above or make a cockpit jumper like I did and have posted many times.

The boost switch should only be used in situations where the engine batteries won't do the job. Others may differ but this is my opinion.

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

Re: Battery Boost

Reply #5 –
Peter your 2812 should charge your house batteries. I imagine you know that there is a
button  at your Magnum panel that that says charge that can stop it from charging other
wise something is wrong.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Battery Boost

Reply #6 –
Chuck.  Completely misread the post.  Geez I am getting old....
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: Battery Boost

Reply #7 –
Quote from: dicksop –
Geez I am getting old....
Join the club.  Photo below taken at my last Birthday party. 

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Battery Boost

Reply #8 –
I leave my boost switch on a lot since 2000 and have never had a problem. I disagree with Pierce and pretty much any one else that seems to think it's a problem. The boost solenoid is EXACTLY the same solenoid as the ignition solenoid which is on the entire time you are driving and never gets hot. And as far as losing power, an airplane engine might fall on your rig, also. It is what it is.
1994 U280, Build 4490
Deming, NM.

Re: Battery Boost

Reply #9 –
One concern with leaving the boost switch on in storage is that if the shore power is lost, both house and chassis battery banks will drain since the boost solenoid connects the two together.  This can create the issue where you can't start the coach or the generator at all, and can damage both banks of batteries.

If you don't store at home where you can keep an eye on it, I wouldn't recommend it.
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: Battery Boost

Reply #10 –
I'm putting one of these in, Blue Sea Systems 500A Remote Battery Switch Solenoid. It will get
rid of my isolator and could get rid of my boost solenoid. I'm not sure I can get rid of the boost
solenoid, It depends on the cables, but the Blue Sea Systems will be hooked in parallel with the
boost solenoid. I don't know it this is good with different batteries. 
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Battery Boost

Reply #11 –
Quote from: oldguy –
I'm putting one of these in, Blue Sea Systems 500A Remote Battery Switch Solenoid. It will get rid of my isolator and could get rid of my boost solenoid.
I went the route you describe two years ago.  I've been very happy with my simplified charging system sans isolator.  Link below to my post (Reply #2):

Delco Remy 28SI Alternator Installation

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Battery Boost

Reply #12 –
Shocked and disappointed that LSL may be out of business, as they have several practical devices that many are using, like Trik L Start, etc.

Many years ago, we installed Blue Sea SI-ACR to keep start battery bank under charge when house bank is being charged, both at the same voltage. We wired it to both banks at existing connections at the top of the bay wall 12-v breaker panel. Also, can use boost solenoid posts.

SI-ACR has a couple of features that we used:

  • With a small wire run from SI-ACR, we have a LED in kitchen showing when the SI-ACR is combining.
  • Another small wire run to SI-ACR from a connection that is live only when ignition is on, prevents SI-ACR from combining. This feature is called Start Isolation and is designed to momentarily stop combining when cranking engine, but we used to limit when batteries are being combined.

Blue Sea SI-ACR uses battery voltage to determine when to start combining and when to stop combining. We have observed during hot weather that our temperature-compensated battery charger will correctly limit GEL battery charging to around 13 volts when battery is around 100 degrees, which was not high enough to tell SI-ACR to start combining, as observed by the kitchen LED being off. This is a normal reaction for voltage-controlled battery bank combiners.

Diode-based combiners like the very popular Trik-L-Start will always feed some voltage from house to start bank, but because of diode characteristics, the start battery will not have enough voltage to be charged up.

LSL's newest voltage-sensing combiner had an option to lower battery voltage sense to close at a lower voltage to compensate for hot batteries. This is one of the reasons LSL has great products. There was another option for Lithium battery charging.

Re: Battery Boost

Reply #13 –
Last summer I was working on my Cousins boats wiring when I first came across the Blue Sea System.
It took me awhile to figure what it was for and how it worked. Using it I get rid of the isolator, boost
solenoid hopefully and my homemade  Trik L Start system. Another advantage is until the voltage
gets down to 12.75 volts I have an extra 300 AH to use for the house.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Battery Boost

Reply #14 –
If one opts to leave the boost switch on while connected to shore power, wouldn't the generator auto-start function kick in if
power is lost for any significant amount of time?
Frank & Connie Williams
1999 U320 '36
Build: 5466
MC: 18335

Re: Battery Boost

Reply #15 –
Frank.  Curious what that answer will be.  But yet another good reason for having the AGS.  It's getting installed by Off Grid in Quartzsite on 1/11.

  Also Lithonics makes a similar device to the blue sea one.    Developed for commercial use where two battery banks are used. Lithium included.  We've used it for a year and engine batts are always topped off.
  And replaces the isolater and boost switch but does the job of both.
Robert and Susan
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR

Re: Battery Boost

Reply #16 –
Yes, to gen auto start if boost switch depletes batteries, IF gen auto start works okay and every time. Have you tested gen auto start to be sure it works and is set to run?

Let gen auto start fail one time and all batteries in coach could be damaged

Keep in mind based on what battery voltage gen auto start kicks in every time batteries, and in your example all house and start batteries, are brought below or around 50% -12.2 volts, their life is reduced.

Buy an automatic battery combiner and forget about the boost switch for charging start battery bank as it is a battery cost saver.

It is important to periodically test gen auto start. To save batteries, we set our gen auto start to kick in at about 12.3 12.4 volts. We also saved our batteries several times when after plugging in to campground shore power, we forgot to throw the pedestal 50-amp breaker to ON. Within the hour after settling down, guess what, the generator auto starts to remind us to turn on the campground breaker. . . More than once we tested gen auto start.
 

Re: Battery Boost

Reply #17 –
I check my gen auto start and set the run time for two hours and then shut it off. I can't rely on
it as if it gets too cold starting the generator needs to go through an extra start cycle so the glow
plugs are hot enough for the engine too start so I prefer to manage the batteries so I don't need
the gen auto start.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport