Highest safe transport SOC of Lishen 272ah cells

[hammick]

I'm on day 8 of my top balance and still not done. I am out of time.

10 of the cells are at 3.400 - 3.402 6 of the cells are between 3.397 - 3.398

So I am am going to let them finish at 3.400, rest for an hour or so, put them in series and start discharging to a safe transport level. We are driving these batteries 1,200 miles to our off grid vacation place. Leaving in 22 hours.

How many AH should I take out for transport? Since I might start the top balance again I want them at the highest SOC possible without damaging them. If I remove 90ah is that enough? My top balance probably won't start again for four or five days.

Thanks for any advice.

 

[Steve_S]

You do not have to discharge them at all... Storage voltage is only if they will be sitting for a long period of time.

 

[HRTKD]

Transport voltage? What? Do you think all these LiFePO4 batteries in RV's are discharged before leaving home and then charged at their destination? Nope. Charge those batteries up, load them for transport and hit the road.

 

[hammick]

Transport voltage? What? Do you think all these LiFePO4 batteries in RV's are discharged before leaving home and then charged at their destination? Nope. Charge those batteries up, load them for transport and hit the road.

Thanks. What I really wanted to know is how many days is OK to leave these at 99% SOC? Sounds like a week or so is fine.

 

[Sojourner1]

If you're going to use them bi weekly you shouldn't have a problem. These aren't fragile eggs even though reading enough forums and post newbies or non users regurgitate bad info.

 

[ArthurEld]

If you're going to use them bi weekly you shouldn't have a problem. These aren't fragile eggs even though reading enough forums and post newbies or non users regurgitate bad info.

barf, are you talking about me?

 

[Sojourner1]

Not anyone on this forum.

 

[HRTKD]

barf, are you talking about me?

We only talk about you BEHIND your back.

 

[ArthurEld]

I regurgitate some ideas that don't pan out

 

[hankcurt]

The state of charge is only unimportant if you can guarantee that the cells will not be exposed to high temperature conditions for an extended period of time. In your case, it sounds like you intend to put them back into use in a relatively short period of time, so this is probably not a factor. But, if it were me, and especially if I was transporting them in a hot environment, I would want them below 25% state of charge. The reason is that the 'calendar aging' damage from high temperature - high state of charge condition has been shown to be irreversible. If someone throws their fully charged batteries into astorage shed for a few months, and it gets hot, you can do a years worth of damage in a few weeks (as compared with room temperature at low state of charge).

Below is the temperature / state of charge / relative aging (stress) chart from a 2017 study on a standard LiFePO4 cell.

 

[Sojourner1]

Can you post the source for gragh? I like data and don't understand what the left side is saying. TY

 

[hankcurt]

It is from this paper from NREL. It contains a lot of math I don't understand, but what they are trying to do is come up with a predictive formula that can be used to project calendar aging and cycle aging under various conditions. The vertical scale units have a use in their formula, but for our purposes it can be used as a relative rate of calendar aging. So for instance, a battery under conditions that have a k(stress) factor of 1.5 will age three times faster than one stored at conditions that have a k(stress) factor of 0.5.

If I can get a better grasp on this study, I will post a thread on it so we can all argue about its relevance and application.

 

[hammick]

Thanks Hankcurt. They are all packed up and loaded. They will not see any warm temps. Resting voltage is around 3.32 volts.