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Old 03-29-2015, 02:43 AM   #1
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Brand: Thor Motor Coach
Model: Vegas 24.1
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THOR #1670
Charging Voltage Shore Power

What voltage should I read when I am hooked up to shore poer and check the house battery voltage?
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Old 03-29-2015, 03:31 AM   #2
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THOR #1150
I believe it's 13.5V or so.
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Old 03-29-2015, 11:57 AM   #3
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THOR #531
You cannot directly read the battery voltage when it is connected to the converter. You can read the state of the converter voltage, and that depends on the type of battery and the current mode of the converter/charger. Assuming lead acid batteries (not AGM):

Absorption mode: 13.6VDC
Bulk mode: 14.4VDC
Float mode: 13.2VDC

When you are using the DC appliances in the coach, your charger will probably be in Absorption mode as it is replacing demand from the battery/or being supplied by the charger. This mode not only provides slow charge to the battery, it is the primary power-supply mode of the converter.

99% of the time in operation, your system will be (or should be) in this mode.

When you are not actively drawing any current from the coach, and the batteries are fully charged, the charger should switch into Float (trickle) mode, which keeps a top-off, or trickle charge on the battery.

In practical experience though, you may never see this mode as all of the low-level loads (fridge, water heater, furnace control boards, TV amplifier, contactor, etc) might keep enough load on the battery that it is always in discharge mode.

Bulk charge is the primary fast-charge mode, used when the battery needs significant recharge. It is limited to 4 hours in the WCFO chargers.

So, essentially:

Bulk mode = fast charge.
Absorption mode = slow charge.
Float mode = top off charge.

Each of these charge modes apply a different voltage to the system.

Some chargers also have a Desulfation mode, which basically cycles the Bulk mode on for a few minutes every day to keep the batteries healthy... but I am not so sure this is really a huge advantage.

If you want to measure the battery itself, it has to be disconnected and at rest for 24 hours to get an accurate measurement - although a reasonably accurate measurement can be achieved with a 1 hour rest.

When disconnected, a Lead Acid battery should read:

100% charged = 12.6VDC
75% charged = 12.4VDC
50% charged = 12.2VDC
25% charged = 12.0VDC
0% charged = 10.8VDC

(AGM and Gell batteries will have slightly different voltages).

Note also that on Thor coaches, disconnected can only be assumed if the battery cables are disconnected, as even if disconnected by the disconnect switch - some parasitic loads may still be present.

Hey Jamie; here is another project we need to do - build a window comparator to show the charge mode...

Maybe it's a function I can add to my yet unrealized tank monitor project.
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Old 03-29-2015, 03:00 PM   #4
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Yeah figured FW28z would provide a much more thorough explanation than my "yeah about X" answer! LOL
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Old 03-29-2015, 07:56 PM   #5
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Sorry... I guess I am a Raconteur.
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Old 03-29-2015, 09:21 PM   #6
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Quote:
Originally Posted by FW28z
Sorry... I guess I am a Raconteur.
LOL No need to apologize: More information is always better.
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Old 03-29-2015, 10:19 PM   #7
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THOR #1503
That was a definitive answer as well as a good primer on charging,

Bruce


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Sorry... I guess I am a Raconteur.
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Old 03-29-2015, 10:29 PM   #8
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THOR #1765
Good post. You are right about parasitic loads. One of the first things I did to my Vegas (after installing a clean dump system) was to install a manual on/off switch to completely disconnect the coach batteries when it is in storage. Otherwise, they will run down relatively quickly.
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