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Charging house batteries while driving

I know I have read articles on this before but can not for the life of me find the topic.
So my question is, I just installed a residential fridge(love it) and inquiring how to charge the house batteries when driving to ensure the fridge still runs when driving?
Is it just turning in the boost switch or not?
Peter
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: Charging house batteries while driving

Reply #1 –
As long as your isolator is working which it should be your house batteries are being charged by the alternator.

Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Charging house batteries while driving

Reply #2 –
Thank you Peter. I am good to go!
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: Charging house batteries while driving

Reply #3 –
Insert a digital volt meter in one of the dash sockets and watch the voltage balance between the engine and the house batts . They should read within a couple of tenths .  You may not charge the c house batts if the voltage stays under a crossover value at the isolator switch. 
If the boost switch shows the house batts getting a charge , then the isolator may be bad or simply not at the dual charging value.

Re: Charging house batteries while driving

Reply #4 –
Expanding on Mike's comment (above) it has been highly recommended for many years on this Forum to install two simple digital volt meters somewhere inside your coach.  One is connected to the chassis (engine) battery bank, and the other to the coach (house) battery bank.  This inexpensive mod allows you to see, at a glance, the relative voltage levels in each battery bank.  You can quickly tell if one bank is not charging properly, or if there is a phantom drain on one of the banks.  It's also a way to verify the operation of the BOOST solenoid.  Starting with the two banks at different voltage levels, when you turn on the BOOST switch they should immediately equalize.  If they don't, there is a problem in the BOOST circuit.

My digital volt meters are on the dash.  However, the add-on meters can be mounted anywhere they are easily viewed by the operator.  Including the factory analog dash volt meter (which reads engine battery voltage) and the SeeLevel volt meter (which reads chassis battery voltage), I have a total of 4 sources of voltage information.  Surprisingly, they all seem to be in very close agreement.  See photo below.  My battery banks were connected in that photo, so all three volt meters in the photo are showing the same voltage. 

I have the habit of glancing at our volt meters every time I step into the coach.  They are constantly powered, and consume only a few milliamps of battery power.  Very comforting to always know the exact SOC on both banks.

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: Charging house batteries while driving

Reply #5 –

So on my 2000 GV320 I have 2-12volt plugs that are factory installed.  One is tied to the house bank and one to the starting bank.  You can get 2 cheap voltage meter that will plug into these.  Not sure if your 98' has 2 but I bet it does.  On mine the top is house and the bottom is chassi.

Something like this, there are hundreds on Amazon
Amazon.com: PALUMMA 24W/4.8A Dual USB Car Charger, 12V to USB Outlet with...

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

2000 GV320 4010 build #5712  2019-?
1999 Bounder 2000-2008
Bardstown, KY
🥃The Bourbon Capital of the World🥃

Re: Charging house batteries while driving

Reply #6 –
My 98 U270 is same as Tommy D's description.  I have a combo USB/voltmeter in each plug so as Chuck says, always have an indicator of house and chassis batteries. Also serves as a night light.
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.

Re: Charging house batteries while driving

Reply #7 –
With the addition of the residential you are now much more dependent of having power available and to best enjoy this upgrade you will need some options for power management. As efficient as new refrigerators comparatively they are still a significant load, especially at the 12-volt to 120-volt inverter process. It is all about the watts, power used. To get power we need pressure, (volts), flow, (amps). volts*amps=watts.  That ~600 watt load of the fridge represents and excess of 60 A/H at the battery. So while your coach is designed to charge the house batteries while driving, can the system keep up with this and all the other loads. Will it do this long term? Do you have enough battery capacity to run this for the time needed? How fast can you charge the batteries while plugged in or more importantly using the generator. My coach has 600 A/H of battery, with a 2000 watt inverter/charger, that only provided 70 A/H for charging. Runing the heat pulls 26 A/H of that. Dry camping I needed to run generator almost 4 hours day just to run heat and other common loads. Adding a current based battery monitor will display actual usage, battery state of charge, and provide the information needed to make sensible upgrades. My inverter charger is now the Xantrex Pro Mariner 3000. 3000 watts, 150 A/H charge, and power share to reduce charger current as needed to support 30 A/H circuit feeding it. It works extremely well.
Dennis Haynes
Bohemia NY
2008 Nimbus 342 SE Carlyle
Build #6475
Motorcade #19148

Re: Charging house batteries while driving

Reply #8 –
Thanks for all the comments!
I did purchase the "cigarette lighter" meters for the front dash(2) and they are a great help for quick reference
My magnum 2812 provides 125 A/H charging with power sharing feature as well so I do not see any issues there
My challenge , because I have only 2 8D batteries will be enough battery power. I am soon to remedy that though, as I have plans to replace them and install 3 batteries ( which is the standard install .. the previous PO only had two installed because the installer said only 2 would fit.....he had them installed the wrong way... ) which should help
Batteries here in Canada run about 3500.00 cdn dollars to replace the 3...sigh
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: Charging house batteries while driving

Reply #9 –
At that price point you are easily into lithium including a B2B charger. Just to complicate your thought processes. You could sell your two good AGM batteries to help offset.
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.

Re: Charging house batteries while driving

Reply #10 –
You can get epoch 460 ah lithium with Bluetooth  for  1399 each with 10% off coupon now.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Charging house batteries while driving

Reply #11 –
The epoch 460 batteries in Canada are 2800.00 each...
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: Charging house batteries while driving

Reply #12 –
Quote from: Peter –
The epoch 460 batteries in Canada are 2800.00 each...
Can you order from the US?
Tim Dianics
Pam Sapienza
Vader PupZilla Labrador Canine Beast (AKA Pup)
Columbia, MO
1996 U320 4000
2021 Jeep Gladiator, Diesel

Re: Charging house batteries while driving

Reply #13 –
The lithium will reduce the capacity loss that occurs from partial charge then more use from AGM's or open cell batteries. Open cells would be dangerous as the compartment is not vented. 

A residential refer puts an extreme load on the electric system as you probably already  know.

Gels or lithium are not as damaged from partial charging then more use.

Double cycle life to use east Penn gels.  Even more life difference if you opt for AGM's and partially charge then use them further.

50% to 85% takes about the same time as 85% to 100% does.  Hence the high cost and noise to run a gen to get to 100%

AGM's will work ok if charged fully overnight. Still 50% cycle life versus gels.  5 years? Versus 10 or more? 
"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