I think I have my low voltage cut off set a bit high and I want to maybe change it. I have a 12S system using all 30Q’s. Does anybody know the safest low voltage for those cells?
If safety only so 2.8. But for the cell durability, 3.6 if much better. And between 3.6 and 2.8, the gain in ah is quite small. See the documentation…
[https://lygte-info.dk › batteries2012 Web results Test of Samsung INR18650-30Q 3000mAh (Pink) - Lygte-info.dk](https://lygte-info.dk › batteries2012 Web results Test of Samsung INR18650-30Q 3000mAh (Pink) - Lygte-info.dk)
So if you don’t want power cutting, set to 3.4 to have some margine versus 3.6 under load
Awesome, thanks for that!
What is the formula to figure out state of charge? Like if 50.4v is 100%, and 40.8v is 0% (for our purposes), what would I use formula wise?
3v cut off
3,2v cut off start.
If you really want some extra range, cut off: 2,8v
There is not much capacity left in lower voltages. It’s not linear
Soc is not linear and changes from cell to cell plus temperature and load current. It is always better to look in to the cells datasheet there are usually graphs with some sample data. With some acceptable error rate you can predict the soc during the run time and good accuracy no load idle voltage with just following those plots and ignore temperature if it is not provided. Also It is good to keep in mind li ion rule of thump 20 to 80% soc range! Means you should not charge/discharge in full rate below 20% soc, usually for high discharge cells like 30Q and lg hg2 I follow: 0.5C for charge below 20% soc and 1.5C between 20 to 80% and again0.5C above 80% soc For discharge below 20% usually only discharge at 1C and and above 20% up to max discharge rate. All these ignored the temperature by assuming cells are above 5 degree Celsius and below 50I even limit it to 45 celsius. I follow these complicated control system not for longevity of the pack but More importantly for safety so I dont become the ”sitting pack in the garage got in fire by itself and burned my house ” story
I know it’s not linear. It’s mostly so I know when my session ended about how far I went with the packs. Right now I stop whenever I start to feel really bad voltage sag and I imagine that won’t really change even with low voltage cutoff adjustments. Just trying to get an idea of where I end each time so I can somehow make some references.
I have my voltage alarms set to 3.0v
Samsung says not to got below 2.5v per cell. I know a lot of people who think the battery will last longer if you don’t go that low. I average 3.2v for my discharge depth.
When I ride untill the alarm goes off it’s under load. So, when I go to charge the battery it’s always 3.2 - 3.3v.
Pack voltage to Ah remaining isn’t very accurate. Every time I charge my battery I look at the voltage prior to starting the charge, and the total AH the battery takes to be fully charged. The average I have noticed is 3.65v is about 50% charge on my setup.
Hi. Soc base on voltage will ve always wrong because it’s depend of the load! The only way to be accurate is to compte the ah (coulomb method). It’s what I have done on my remote :