Hi all,
I recently changed my wife’s go go elite traveller mobility scooter from lead acid to LiFPo. I used a non-shunt Bluetooth battery monitor that gives ballpark estimate of SOC. I have ordered the SmartShunt 300A to replace this. I was curious about power draw (Bluetooth) when not in use. I tell my wife when not using the battery to leave it at around 50% SOC. She uses it a few times a month (3 to 5) for them parks (FL) so it doesn’t sit very long and she charges it just before she goes to the park.
Do I need to install a power switch to the ouside of the battery box to turn off the SmartShunt or is the power draw small enough that it should not drain the battery much when not in use. The current non-shunt monitor doesn’t seem to use much power draw, hoping the SmartShunt is the same. Thanks - Jeff
The smart shunt draw is <1mA.
But shy leave the battery at 50%? A charge then discharge will keep the battery warmer that is actually worse for the battery cells than charging it and leaving it at full.
When I say she charges it before going to the park, I mean there is a delta of 1 to 2 hours between charging and using, so temps should resolve in that time. LiFPo I know is generally more forgiving of leaving at 100% for longer periods of time than say NMC chemistry, I just recommended to her the 50% SOC when not in use since she never really knows when she may go until she decides to go and the LiFPo batteries take a far less time to charge than the lead-acid ones.
Although the non-shunt monitor works, it is not very accurate - she recently took it to Dollywood in TN, it has very hilly terrain and it lasted all day w/o recharging. It was complaining (alarm), but when she did charge it back up it did not take very long so I doubt it was as low as it thought it was, hence trying the SmartShunt product to get better accuracy.
If the SmartShunt draw is less than 1mA I should be OK w/o an on/off switch as often as she uses it.
One of the other things to watch out for is one cell running lower than others. Can happen if top balancing is not taken care of. It can trigger low battery alarms before the battery as a whole is low.
You are right the efficiency of lithiums over lead acids is wonderful. And definitely safer than nmc.