What voltage under load is 50% T-105's
I have two trojan T105's for my toyhauler. For the most part, my norcold refrigerator is the only load , other than a occasional light in the bathroom and the water pump. We use flash lights allo...
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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.
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.
