Whizbang Jr. and LiFePO4 SOC

[openplanet]

I'll be taking delivery of a 400ah 48v LiFePO4 system in a month.  As shipped, the system will be configured at 40% SOC.  Given the known LiFePO4 self-discharge rate I'll then know the SOC on arrival.  I'll want to MANUALLY set the WBJr SOC to that value.  Alas, I see no way to accomplish this.  Very much hope I'm wrong.  Please set me straight.  Thanks.

***
After reading the thread "Force reset of WBJ AH meter" a workaround occurs to me.  Given that I want to stay strictly between 20% and 80% SOC, I could run the new batteries down from the known delivered value to 20% SOC then manually reset WBJr SOC to zero. I could then tell the Classic that my Ah capacity is 240 rather than 400.  The WBJr SOC 0% - 100% SOC range will then map onto the actual 20% - 80% SOC.
Does this make sense?  THanks.

[ClassicCrazy]

First thing - is your lithium battery coming with a BMS ?

Yes - one way you could change the SOC % would be by changing the capacity setting .

One way to do what you want to do might be by bottom balancing it - really depends a lot on your BMS.
Lithiums are tricky since their voltage stays the same and can suddenly drop .
To do what you want to do I think you might have to figure out an ending amp  and use bottom balancing.
Hard to give advice on lithiums because there are so many factors like the BMS . Lithiums are easy to ruin by messing up if there is no BMS and even with those you need to be careful about voltages and current.
You should go by the manufacturers info .

Larry 

[mahendra]

My experience is that there is no need for additional bms.The wbjr is a bms.The only feature is that it cannot measure individual cell temperature and cell voltages and individual cell soc.
There is this little device called Batt Go isdt battery balancer that seems o. Amazon it does a good job monitoring cell soc and voltages. Just for broad area monitoring it can be used to get a bit of piece of mind and some level of monitoring.

[boB]

My experience is that there is no need for additional bms.The wbjr is a bms.The only feature is that it cannot measure individual cell temperature and cell voltages and individual cell soc.
There is this little device called Batt Go isdt battery balancer that seems o. Amazon it does a good job monitoring cell soc and voltages. Just for broad area monitoring it can be used to get a bit of piece of mind and some level of monitoring.

So, are you suggesting that you want to build your own Lithium battery BMS to take care of the balancing, temperature and safety factor ?

Sure, if you're the technical type, then that's fine.  If not, then I would say to use a reputable product with BMS built in.

You can use a WB Jr. in addition to that of course if you want to get an idea of the SOC but I haven't seen how the WB Jr. works with those kinds of batteries.  What is the Amp-Hour efficiency of Li batteries ?  Is it the same % efficiency at all SOC % ?  I don't know.
Does it change with battery temperature ?  Not sure about that either, myself.  I guess I will be learning a lot of that sooner or later.