Skip to main content ↑ ↓
Topic: Shore Power and House Battery Charging (Read 1895 times) previous topic - next topic

Shore Power and House Battery Charging

I have not dealt much with these issues, and need some guidance.

We temporarily relocated our coach to a friend's front yard while we had some paving done.  While there, the generator auto switch started the generator to charge the house batteries.  I did not know the button was pressed - may have been that way for ages.

It SEEMS like the house batteries did not accept a good charge, but that is secondary.

When plugged into shore power, I get no AC in the coach.  I checked and cycled all of the breakers.  Inverter charging is off.  When I run the generator, I get AC, and the inverter starts charging the house batteries.  A few years ago, I replaced both transfer switches with PD52s.

1.  I cannot think of a reason that low house batteries (11.6 volts) would prevent the transfer switch from operating.

2.  I THINK one transfer switch is for allowing shore power, and the second is for prioritizing shore over generator.  Correct?

3.  I THINK there is an AC wire that signals the transfer switch to operate.  Is there anything between the big AC input on the transfer switch, and the wire that triggers?  Any separate breaker or circuitry?

4.  Should manually pressing the contactors in the transfer switch make the power transfer (assuming the contactor is not burned up?)

I will be digging for some paper manuals, and I would welcome your guidance.
Matt B
1998 u-320

Re: Shore Power and House Battery Charging

Reply #1 –
Looks like I found the problem!

My "hold against" AC tester showed power at the inlet of the transfer switch.  But it was only the hot, and not the neutral.  A little adapter was the problem.  Things electrical seem OK now, and I will see if the house batteries charge properly.
Matt B
1998 u-320

Re: Shore Power and House Battery Charging

Reply #2 –
I am sure someone more familiar will chime in but I believe one transfer switch is for the inverter and the other to switch between shore and generator. Priority is determined by how the transfer switch is wired.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Shore Power and House Battery Charging

Reply #3 –
Quote from: oldmattb –
2.  I THINK one transfer switch is for allowing shore power, and the second is for prioritizing shore over generator.  Correct?
Actually, like Chuck (craneman) says, one transfer switch selects between shore power or generator power.  The other one selects between main panel power or the inverter/charger.

See typical 110V power schematic linked below:

The selected media item is not currently available.
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: Shore Power and House Battery Charging

Reply #4 –
Yes!  That makes sense.  Thanks!
Matt B
1998 u-320

Re: Shore Power and House Battery Charging

Reply #5 –
Main transfer switch: Inputs= 1)Shore 240volt & 2)Generator 120volt (or 240volt), Output= Main breaker panel main 50-amp 240volt breaker.
Secondary transfer switch: Inputs= 1)Main breaker panel sub 50-amp 120volt breaker & 2)Inverter 30-amp output breaker, Output= Inverter breaker panel (often on front of bed) input main breaker.
Note:  All coaches do not have Secondary transfer switch.  With Secondary tran-sw, inverter breaker panel can handle more appliances when coach is on Shore or Gen, fewer appliances when inverting off house battery bank.  Coaches without Secondary tran-sw can only handle 3600 watts of appliances all the time.

Re: Shore Power and House Battery Charging

Reply #6 –
Thanks for the schematic and the written explanation.  Aside from replacing the transfer switches to eliminate the noisy hum, I had not yet dealt much with that part of the coach.

It looks like my house batteries might still be good.  The inverter went from bulk charge to float yesterday, so the batteries are accepting a charge and responding.  Today, I will disconnect the AC and see if the batteries retain a charge under a small load.
Matt B
1998 u-320

Re: Shore Power and House Battery Charging

Reply #7 –
If you want to leave your shore power on  you can flip the inverter breaker at the bed to check house batteries
SLC12

Re: Shore Power and House Battery Charging

Reply #8 –
One thing not noted when understanding how the two transfer switch's input & output work IS what triggers each transfer to switch from input 1) to 2). . .

When BOTH transfer switch inputs are present, one input will control the output.  This control is called "Priority" and coaches can be built with one or the other.  It is very important to know how your coach is wired.

Main transfer switch will be either Shore or Generator Priority.  Secondary will be Inverter or Shore-Generator Priority.

With Shore connected, when tripping the main panel inverter breaker to simulate 'no Shore' to change from charger to inverting, the separate inverter panel may still be sourced by Shore if the secondary transfer switch is Shore-Generator Priority.

Tripping both inverter and the secondary-tranfer-switch breakers would cause the inverter to power coach outlets.  If a coach just has one transfer switch, only the inverter breaker would be needed.

Re: Shore Power and House Battery Charging

Reply #9 –
If both transfer switches are dual contactor switches, even with the inverter or AS faked out transfer switch 2 can only provide power to panel #2.  Would be rare to see it done this way as the inverter/bypass is now usually done in the inverter or inverter charger.  Note the main feed to ATS #2 does not have over current protection. So panel #2 needs that large breaker.
Dennis Haynes
Bohemia NY
2008 Nimbus 342 SE Carlyle
Build #6475
Motorcade #19148

Re: Shore Power and House Battery Charging

Reply #10 –
To add to this.

In the drawing that is in post #3, it is showing that shore power takes priority for both the main and inverter transfer switches.  I have seen the main transfer switch where either shore power or generator has priority.  I have never seen where the inverter take priority but never say never.

For those that do not know how priority works. If the transfer switch only see power on one of the sources, the transfer switch will activate that relay(contactor).  If the transfer switch sees power coming form both sources the transfer switch will then activate the relay for the one that has priority.
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: Shore Power and House Battery Charging

Reply #11 –
Quote from: Sherry Casteen –
If you want to leave your shore power on  you can flip the inverter breaker at the bed to check house batteries

Based on the drawing in post #3 just turning the breaker to the inverter will not test the inverter. The reason for this is when the inverter sees lose of shore power it will start up (unless if inverter has search it would not see a load and not turn on), but the inverter transfer switch will not switch over since it is still seeing shore power.  You would need to trip the main breaker off to test the inverter and  batteries.
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: Shore Power and House Battery Charging

Reply #12 –
With the coach properly plugged in, the house batteries charged "fully," from bulk charge to float.  The next morning, the battery charge was down to under 12 volts, with only the refrigerator (original propane-AC unit) and the usual small drains.  So I removed the cables from one of the house batteries, charged it with a free-standing charger and let it sit overnight.  Down to under 12 volts overnight.  I guess the batteries have lost their magic.

I briefly considered the lithium conversion, but we usually have very modest demands when we are not on shore power.

I was impressed with the long life of the batteries that are in there, the Intimidators, but was not warming up to the $900 each, what with repaving our driveway last week, and a new heat pump for the house awaiting our order.  Chuck and Jeannie, in a thread a year ago, suggested the O'Reilly 8D AGM as a good budget replacement.  I went to our new and local O'Reilly and asked about the batteries.  The can get them in a few days, and $525.99 each.  I asked about a price break, hoping for 10 percent, expecting maybe 5 percent.  They offered $895.23 including tax.  For three!  Well, OK!

I am still wondering if they will call and declare an "oops!"
Matt B
1998 u-320

Re: Shore Power and House Battery Charging

Reply #13 –
Those are/were good batteries.  I also used them when I had my 1997 u295.  I marked, disconnect, taped up the ends of the battery cables.  I then drove coach to store,  they removed old and installed new ones.  I didn't have to pick up a  battery. When I got home I rewire them
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: Shore Power and House Battery Charging

Reply #14 –
If your battery connectors are showing their age, this is a good opportunity to replace them.

I prefer the solid lead military style, rather than the lighter duty zinc ones.

Thinking about new house 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: Shore Power and House Battery Charging

Reply #15 –
I think you can easily replace your AGMs with lithium for under $900 and have more capacity and less weight.
Jerre and Kathy Griffin
2003 U320 4220 Special
Build # 6207
2022 RAM Laramie 4X4 EcoDiesel
2002 Country Coach Magna 37 Tag- Forever Coach-Died in fire 7/23
1997 Country Coach 32 Intrigue-No slides-Wonderful

Re: Shore Power and House Battery Charging

Reply #16 –
Quote from: DaBus –
I think you can easily replace your AGMs with lithium for under $900 and have more capacity and less weight.

I believe in lithium,  but in this case I would go with the auto parts AGM batteries. Simply change,  Matt says he has gotten by before with regular AGM, don't have to fiddle with the charger, or add b2b charger, or worry about taking out his alternator.
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: Shore Power and House Battery Charging

Reply #17 –
Yes on the simple.  We have had a very busy year, what with driveways, a bunch of yard projects, car shopping, soul searching, and Kelly's bone marrow transplant.

I am liking the idea of chucking those batteries in and relaxing some.  If/when we switch to a residential fridge, or do lots of in-place boondocking, I can revisit the issue.  The cool savings on the O'Reilly batteries versus the alternatives will make that an easier decision later.  And an easier time of it now.
Matt B
1998 u-320