How does the Liitokala 500 work to discharge cells?

[Cyclomania]

So I have the Liitokala 500 from the video below. I am going to use this to discharge the cells before building my battery. At least that is my thinking. So that they have lower voltages than they are capable of having at any given time.

Someone gave the tips that they become slightly less explosive/burny when discharged. Is that right?

Also, when building the battery I am going to keep all the cells being at the same voltage right? Because otherwise it could lead to a short, right? Because when the BMS equalises it could then give rise to sparks?

So basically what I have to do is to discharge the cells with the Liitokala-500 to make them a bit less dangerous.

In this video he has a tutorial over the Liitokala-500. But I don,t quite understand how to discharge the cells from it. Perhaps it is done through the "fast test" that he talks about?

 

[From-A-To-B]

I think you're confused about a few of these points.

So I have the Liitokala 500 from the video below. I am going to use this to discharge the cells before building my battery. At least that is my thinking. So that they have lower voltages than they are capable of having at any given time.

Someone gave the tips that they become slightly less explosive/burny when discharged. Is that right?

When cells are at a lower voltage, they have less potential energy to output if something does go wrong. But there's no real need to build with empty cells - just don't build with them when they're at 4.2 volts, if possible.

Also, when building the battery I am going to keep all the cells being at the same voltage right? Because otherwise it could lead to a short, right? Because when the BMS equalises it could then give rise to sparks?

Shorts are caused by completing circuits with parts of your battery that are at different voltages in relationship with each other. This has little to do with individual cell voltages.

So basically what I have to do is to discharge the cells with the Liitokala-500 to make them a bit less dangerous.

Given your unfamiliarity, it occurs to me that you may be better off leaving the cells in the resting voltage they arrive at, assuming they're all balanced. Discharging the cells will inevitably bring them out of balance with each other, something that you or your BMS will have to correct down the line. Might as well start off with all your cells at the same state of charge.

In this video he has a tutorial over the Liitokala-500. But I don,t quite understand how to discharge the cells from it. Perhaps it is done through the "fast test" that he talks about?

Sorry, I haven't used that tool and cannot comment.

 

[lnanek]

For chargers that support a storage or discharge function, you'd generally press the mode button until the display offers that. I don't think that charger does, however. It does have a capacity test function that discharges then charges the battery. I suppose if you pulled the batteries out in the middle you'd have discharged batteries.

It also offers USB 5V output when unplugged with batteries installed. So I suppose you could just use that function and plug a phone into the USB port as the discharging load.

Personally, when discharging cells/p-groups I use a cell meter with a balancing discharge function:

https://www.amazon.com/dp/B0178P8H9U

For balancing p-groups I use an active balancer:

https://www.amazon.com/dp/B0B3D5JCRC

And for discharging packs I just plug them into a standard AC incandescent lightbulb, which works fine on DC. Be sure to discharge packs through a BMS unless you are checking the p-group voltages yourself manually so you can stop discharge at low voltage cutoff yourself.

 

[lnanek]

When cells are at a lower voltage, they have less potential energy to output if something does go wrong.

More than that, some safety features the more expensive cells have like vents work better at lower states of charge:

Compared with the battery with a safety vent, the thermal runaway behaviors of the battery in the absence of a safety vent are greatly worsened with ignition and thermal runaway occurring far earlier. As the battery SOC increases, it is demonstrated that the effect of the safety vent on battery thermal safety is reduced to some extent, with the difference in the times to thermal runaway between the batteries with and without a safety vent decreasing gradually.

https://www.sciencedirect.com/science/article/abs/pii/S0957582022000179

 

[Cyclomania]

More than that, some safety features the more expensive cells have like vents work better at lower states of charge:

Personally, when discharging cells/p-groups I use a cell meter with a balancing discharge function:
https://www.amazon.com/dp/B0178P8H9U

https://www.sciencedirect.com/science/article/abs/pii/S0957582022000179

That cell meter might be a good investment? This one can discharge cells to a certain level determined by you?

 

[batteryGOLD]

if you just need to discharge cells, for safety storage at home/ battery building (safety while U're building pack and spotting, the less voltage, tha less worries..), I recommend discharge down to 3.0V (10% SOC) any cells or batteries stored at home..
good cells will keep this voltage long time storage, if is a bad cell it will leak some voltage.. but if a good 18650 cell stored at 3.0V, it will keep that value for long time, +months, years..
also some concerns (not much) about logistics/shipping system when shipping batteries. most batteries are shipped at 50% SOC, maybe thats a lot of pyrotechnic energy packed inside a mail box.. no rules for battery shipping % State Of Charge? could you easy send a 84V 50Ah charged at 120% anywhere worldwide or debalanced with cells at 5volts?

there are a lot of LiPo packs circulating inside just a simple envelope packing. imagine a giant mail warehouse, and one pack contains a LiPo pack that decides go on fire, it will spread fire to entire mail warehouse. (dhl,tnt,royal mail,china mail and others careful with batteries at your warehouses!!)

anyway..
a dirty 1S discharge system is using 4ohm resistor for discharge cell at avg 1A P=RI^2 = 4x1 = 4W . use 5W resistor.

if you need fast discharge , just parallel 4ohm resistors, one 4ohm resistor discharge @ 1A, so x10 parallel resistors discharge @ 10A. (all 5W resistors ->40W heat losses at 10A discharge a 18650)
make sure to control volts until cut point of 3.0V, otherwise your cell or multiple parallel cells will discharge down to 0Volts..

dirty resistors or a good smart charger/discharger to control/monitor Ah, Wh, Volts, Amperes ?
remember, dischargin cells at 1A is very time consuming.. soo play with fast discharge

example one 3000mAh cell discharge in 3hours @1A ( fake cells are not detected at 1A discharge, to detect fake cells U need at least 5A-10A discharge rate..)
a 3000mAh cell just take 18min dischargin @10A (make sure cell supports 10A discharge, otherwise use lower discharge current..) butt example at a 6P system, discharge @10A will just pull 1,7A from each cell, soo discharge time would be 3/1,7= 1,76hours aprox 106minutes to discharge a 1S6P array @ 10A

 

[Cyclomania]

Given your unfamiliarity, it occurs to me that you may be better off leaving the cells in the resting voltage they arrive at, assuming they're all balanced. Discharging the cells will inevitably bring them out of balance with each other, something that you or your BMS will have to correct down the line. Might as well start off with all your cells at the same state of charge.

Yeah, perhaps that is best. But I still have to figure out how to even measure the cells with the liitokala in the first place.

I don’t know how it works yet. I am doing research before my very first battery build right now. This is my first.

So all you pros basically measure the cells to see if they are almost the exact same voltage?

So you mean the cells can be at the voltage they came at as long as the voltage is almost the same with every cell then, right?

If they are at 3,7 volts they are more dangerous right? This is why I thought it would be best to discharge them a bit before the build ? Down to about 2 volts or so?

 

[Cyclomania]

Shorts are caused by completing circuits with parts of your battery that are at different voltages in relationship with each other. This has little to do with individual circuits.

When you say circuits you mean the series? So for example if one of the 14 series is not the same voltage as one of the other 14 series, that could lead to a short? Is that how it works or what causes the shorts?

 

[Cyclomania]

Personally, when discharging cells/p-groups I use a cell meter with a balancing discharge function:

https://www.amazon.com/dp/B0178P8H9U

For balancing p-groups I use an active balancer:

https://www.amazon.com/dp/B0B3D5JCRC

Would you say they are both necessary for absolute safety? My thinking is to buy the cell meter but not the activate balancer since that one is a bit expensive. But maybe they are both necessary?

Or is the balancer necessary for best practice and top safety perhaps? Then I might order that one too. But I am curious about what you think first.