Is 100Wh from a standard Group24 battery reasonable?

[Reflex439]

I don’t know the condition or actual specs on the battery, but its a used battery in a RV I purchased used.
Here is how it is marked;
M24-1 starting marine battery
Marine cranking 625
Cold cranking 500
Reserve capacity 95

When using it, I can get a hour or so running a 19” 12V TV, running the fantastic fan on low most of the night, a couple LED lights, and the refrig on LP setting. In the morning the monitor I have installed shows ~100Wh of energy used, voltage of around 11.8 to 12.0 with a light load (refrig on LP and fan on low), and needing to be recharged.

I am not familiar with watts vs amps over a time frame, so I don’t know if 100Wh is typical for a Group 24 battery before needing to be recharged. Does this seem normal for similar batteries? If not, what might be considered more reasonable for a Group 24 deep cycle battery? 1.5x, 2x or ???

Currently this is the only house battery installed, other than the vehicle battery which is isolated. I have just enough room for two side-by-side group 24 batteries (see dimensions below).

Just looking for ideas on increasing the current capacity, and hoping for a minimum of a two fold increase. I do not want to modify the existing battery compartment, so the right solution needs to fit in a 14”W x 10.5L” x 9.5”H space

Thanks...

[MEXICOWANDERER]

Watt hours is a scientific method to absolutely determine energy capacity of a battery and is not used outside battery test protocols. AMP HOURS is more easily defined for the regular consumer.

[tenbear]

MrWizard wrote:
1 amp at 12v would be 12 amp hrs

How about: 1 amp at 12v would be 1 amp hr or 12 watt hrs.

Am I missing something?

[Reflex439]

The above is the display for the monitor. When the lower right number, labeled "Wh" reads 100, the Voltage is in the 11.8 to 12.0 range, and the display is flashing indicating the alarm I set if it drops below 12.0.

I should note when the photo was taken, the RV was connected to shore power. The 70Wh was how much energy was used prior to connecting to shore power.

[MrWizard]

Are you sure you Don't you mean Amp Hrs ?

1 amp at 12v would be 12 amp hrs
TV using 8 amps for two hrs would be 16 amp hrs which at 12v is 192 watt hours

100 watt hrs is next to nothing and the batteries should be reading at least 12.6

100 amp hrs is over 1000 watt hrs would leave you with a battery needing recharge

If you installed an amp meter, that reading is 100 Amp Hours

[Reflex439]

Thanks road-runner, those estimates help put things in perspective for me.

I actually don’t know how accurate the 100Wh figure is. The battery monitor is hooked to a 100amp shunt on the battery. I reset it after a full charge and its usually around 100Wh when the voltage drops to just under 12V. Its a number that I can better judge and plan for vs the LEDs’ that were standard on the RV. It may need to be calibrated, but even as is its very helpful as a ‘fuel gauge’.

[Reflex439]

I thought it might be a cheap battery, but wasn't sure. So a 200 amp hour total capacity should get me 200Wh before needing recharge? If so,
I could get two group 24 batteries and get 400Wh, quadrupling my current capacity, that would be awesome.

[road-runner]

100 watt hours is 8.3 amp hours at 12 volts. If the 100 watt hour figure is correct, a group 24 battery should be able to handle this easily. For a comparison, running headlights (and taillights) for an hour would consume in the ballpark of 150 watt hours. An hour of furnace run time would be about 85 watt hours. A dual golf cart battery can supply about 2500 watt hours (but it's generally recommended to not use more than half of that before recharging).

[MEXICOWANDERER]

Normal. Your battery is a cheapo. recommend 200 AMP HOURS TOTAL CAPACITY.