What voltage under load is 50% T-105's

BFL13 wrote:
Also you can get away with several lower than 50% deep cycles with 6s, so no big deal if you do go down to 40% or whatever.

A 1.0v drop from just watching tv/receiver seems excessive to me. If RJ does this on a regular basis, that can't be good. I don't know what reason there could possibly be for doing that.

2oldman wrote:

RJsfishin wrote:
..the voltmeter get down to 11.0, I figure its very near time to recharge.

Yah, I'd say so- it's way past. :E

He said it went back to 12.0 with load removed so not quite so bad but still time to recharge at maybe 40%.

At 11.0 the inverter alarm starts sounding with many models. A one volt drop under the small load described could be reduced several ways if RJ wanted to, but he must have his reasons.

The problem with the OP's question IMO is that the same load can have different voltage drops in each rig depending on the wiring etc resistances, so it is hard to say exactly.

T-105s no load 50% is 12.1v, so a small load might show 12.0. Also you can get away with several lower than 50% deep cycles with 6s, so no big deal if you do go down to 40% or whatever.

RJsfishin wrote:
..the voltmeter get down to 11.0, I figure its very near time to recharge.

Yah, I'd say so- it's way past. :E

Thanks guys.

I wont let the voltage get below 12.2 just to be safe.

I have a LED voltmeter right next to the TV. While watching TV.(and sat receiver) and the voltmeter get down to 11.0, I figure its very near time to recharge.
If I flip the inverter off (tv & sat off) the voltage jumps to about 12.0
But this may be different on other RVs, depending on voltage loss on any given circuit.

Here's how you can figure it out.

Turn everything off and let the batteries rest for 12 hours or so. NOT at full charge with a surface charge on them, but at 70% or so; wherever in the range you think you'll typically operate. Take the voltage. That's your true state of charge voltage.

Turn on the fridge and other normal parasites like propane detectors. Check voltage again. Now you know what the difference is between resting voltage and idling voltage.

Do it again with the water pump or furnace on and now you'll get some eye opening info on the voltage sag with a real load on.

Now with that you can easily do the math. So using Oldmans's 12.1 above as an example: if the idling load drops you .05 the 50% SOC with idling load is 12.05.
If the furnace drops you .2 volts then 50% with parasites and furnace is 11.85. Easy peasy.

on propane load varies from 1.5 to 0.5 amps. You would need to make a table for your specific RV.

Unless your Norcold is a true 12v refrigerator, which is uncommon, the only load is a tiny amount for its control board. If it's a 'real' 12vdc refer, then it pulls around 30a, and a battery reading would be inaccurate, and too low.

12.1v is 50%. Full chart is in here: 12v side of life.