my understanding is that lithium batteries hold a relatively steady voltage across their period of discharge, only reducing right near the end of their capacity. If this is correct, how do I determine the State of Charge as the battery is used up?
Peter_n_Margaret said
11:29 AM Dec 2, 2019
It is difficult to establish the state of charge of any battery while it is in use.
Use a controller or secondary instrument that can count all power consumed and charged.
Cheers,
Peter
T1 Terry said
03:02 PM Dec 2, 2019
A Victron 700 or 712 BMV with the Peukert factor set to 1.00 and charge efficiency to 100% and once the battery is fully charged, the State of Charge will remain reasonably accurate for about 1 mth, then a full recharge just to reset the 100% SOC to clear any errors that have crept in from small loads and small charge currents the current threshold setting has missed. That one can be tricky to set unless you have well set up cabling that avoids "noise" on the power circuits. Set too high and some loads sneak under the radar, set to fine and noise on the circuit is identified as either a charging current or discharge current.
The quality of the lithium cells will also come into play, so the Peukert factor and charge efficiency might need fine tuning as well if you see unrealistic errors creeping in to the readings.
One important thing I missed, reset the charged voltage to 14v, otherwise the BMV will keep resetting the 100% SOC well before the actual 100% level has been reached.
T1 Terry
glassies said
12:16 AM Dec 15, 2019
Terry im scared just reading all of that im still in the midst of getting my van in order ive got the cb radio in and a nudge bar fitted i will email you some pics of my lil sweet home and my van soon give marg a big hug for me xx might even catch up next year
my understanding is that lithium batteries hold a relatively steady voltage across their period of discharge, only reducing right near the end of their capacity. If this is correct, how do I determine the State of Charge as the battery is used up?
Use a controller or secondary instrument that can count all power consumed and charged.
Cheers,
Peter
The quality of the lithium cells will also come into play, so the Peukert factor and charge efficiency might need fine tuning as well if you see unrealistic errors creeping in to the readings.
One important thing I missed, reset the charged voltage to 14v, otherwise the BMV will keep resetting the 100% SOC well before the actual 100% level has been reached.
T1 Terry
Terry im scared just reading all of that im still in the midst of getting my van in order ive got the cb radio in and a nudge bar fitted i will email you some pics of my lil sweet home and my van soon give marg a big hug for me xx might even catch up next year