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Old 10-20-2022, 08:17 AM   #1
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Location: WA
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Question Why Shore-Power not fully charging House Battery

Hello, and Thank you

This is a continuation of a previous thread.
van is Ford E-250 2001 RB-50

Charging House Battery Without Driving?

Note, in Aug 2022, I installed a new Fullriver DC210-12APW

House Battery Drain Test:
To assure fully charged, drove 200 miles.
Parked, turned on house Norcold frig to full power 5 to provide power drain.
Using 12V Plug-in Car Battery System Tester:
  • start drain test
  • 0hr, 12.65 green, 60F
  • 2hr, 12.55 green, 32F
  • 6hr, 12.40 yellow, 28F
  • 12hr, 12.20 yellow, 26F
  • 24hr, 11.90 yellow, 26F
  • stop drain test

House Battery Shore-Power Charge Test:
Plugged Van to Shore-Power, turned off house Norcold frig, did nothing more, no change to the main house breaker, set the same as when driving.
  • start charge test
  • Plugged shore-power
  • 0hr, 11.90 yellow
  • 1 day, 12.25 yellow
  • unplugged shore-power
  • 2 days, 12.20 yellow
  • 7 days, 12.15 yellow
  • stop charge test

Plugged into Shore-Power never got to the full 12.65 green as achieved by driving, maxed at 12.20 yellow

Clueless, what step am I missing, or what is the issue not charging to full 12.65 green plugged into Shore-Power?
or... Is this the best that Shore-Power can provide?

Thank you
much appreciated

Jeff in Seattle
2001 Ford EB 250
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Old 10-20-2022, 11:31 AM   #2
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With out knowing the charger that is installed it would be hard to make a real assessment. That said, it does appear to be very low for a 24 hour charge. For the record 12.65 is not a fully charged battery. There obviously could be some voltage drop based on location and monitoring device. interested in why you stopped the charge at 1 day, but kept recording data for up to seven days. It obviously can't charge when not plugged in.

Are you positive that you had everything turned off (frig) in the shore power test? Any power consumed would not go to the battery. Do you know if you have a diode based isolator or voltage controlled relay Separator, ACR) hooked up for Charging via alternator

So try to look around data on the charger used, see if you have a charge wizard installed.

But yes, you should be able to do better than that for shore power charging, much better.


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Old 10-20-2022, 04:39 PM   #3
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It seems like there is no charging from the shore charger. Your drain test stops at 11.9. At which you start the charge test.
That should immediately go well above 13v at least. It barely climbs past 12 which is probably just it’s rest state. Then slowly drops after a week.
You need to get in there and see what charger is there and if it is coming on at all I think.
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Old 10-20-2022, 07:24 PM   #4
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Agreed, you should see up in the 13's while charging. I routinely see 13.4 on digital meters with most chargers, and sometimes higher.
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Old 10-20-2022, 08:35 PM   #5
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So again, this would really depend on the charger. But I do tend to agree the charger is bad. Generally the beginning of a charge cycle would be bulk which is generally considered constant current. With a battery drained that low it would not be unreasonable not to see the voltage go up to a high potential. As the battery gets charged the voltage will continue to get higher. When it reaches the absorption voltage it would then switch to the the absorption stage. In this stage (constant voltage) it will hold the voltage, and slowly reduce current until it reaches a certain time limit and or tail current. After that it would go into a float charge which would be in the mid 13.

I suspect that this is just a converter, so it probably tops out at the mid 13 anyway. Unless it has a charge wizard, which will be put it at the 14 range.

It seems the battery is around 40% DOD, so you have around 120 to 130 plus amp hours to put back in the battery. So even if it was a 10 amp charger we should have seen it get full in 12 to 14 hrs. The output of the charger would also be reduced by and consumers going on at the time.

I would also check for any loose connections as those generally just become a resistance to your voltage reading and charge current.

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Old 10-22-2022, 10:33 AM   #6
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Do you know if the vehicle even has an isolator?

I know of a few instances where there were issues with the isolator's commonly used in your year vehicle. If the isolator isn't isolating from the vehicle battery, I can see the house being pulled down to the starting battery voltage level. Have you checked the starting battery voltage and compare to the house? If the house shows a specific voltage in the mid 12 v range with no load and you turn on the headlights, the house battery voltage should not move while the starting battery begins to taper off. It's an EZ check.

What type battery are you using for the house system?

I would get a 10 amp automotive charger with a AGM (if you have an AGM) setting, disconnect the battery and let it charge for a couple days. Then check voltage and note the voltages as it sits over a day w/o any charge/load. A fully charged AGM (depending on the manufacture) should sit around 12.75 (or higher) for several days w/o any load.

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charging, house battery, shore power

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