Shload of old 18650s. Best approach to charge?

Batteries and Chargers Rechargeable Batteries
41

If you treat the 144 3500 mAh cells as one big cell, it’d have 504 Ah of energy. Take 30% of that, divide by 3 years worth of hours, and it works out to at least 6 mA of standby drain.

For comparison, a lot of the flashlights around here use about 0.03 mA in standby, or 0.1 to 0.2 mA when the battery monitor LEDs are lit up and monitoring. It would take over 100 years to drain a battery that size from 30% to zero, and that’s basically just the power needed to blink red non-stop to ask the user to recharge it.

I think the manufacturer just didn’t bother optimizing its standby power, because it’s such a big battery they probably assumed it wouldn’t matter.

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42

The manufacturer was thinking about retirement on an island drinking pina coladas. Definitely not thinking about your batteries.

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43

I wonder if the Bluetooth feature can be shut off – that by itself will draw a good bit --then lots of BMS use power in order for them to operate — I’m wondering also what is actually 30% charge – I know some suppliers ship 3.3v and below – not 30%

44

I would imagine the Bluetooth turns off but I could definitely be wrong. It’s definitely possible. That’s about when you would start to worry, after about 3 years. But I’ve taken 18650s out of packs 10 years old, still in the box, that were >3v. And packs that were 15+ and still over zero. Too discharged to use, but not at zero yet. But you never know, that’s bad luck

45

I don’t know exactly what BMS is in the scooter. But, the scooter manufacturer refered me to this iPhone app for an ability to monitor battery state of charge, etc.

The app page says it is for working with a jiabaida BMS (JBD-SP15S001 / JBD-SP05S002).

I don’t know much at all about BMS’s. But, it’s my GUESS that the scooter manufacturer is buying this BMS and plugging it into the pack. So, I’m not sure if the scooter manufacturer has much control over things like standby power management.

The scooter does not provide a way to turn off the Bluetooth. As it is setup, if I turned off the Bluetooth, I would have no way to turn it back on.

It does seem like it would be nice if the scooter had a way to power the BMS off and back on. But, maybe that would cause it to lose its calibration info for the battery or something, so…

In the end, the simple solution for me is to never let it sit so long again that the batteries completely die. Which should not be difficult…

46

That’s the same App I use on several of my BMS – There’s a way to turn the battery off from the App, the bluetooth goes in standby after so long — I have 2 of them setup with a manual On/Off switch to turn the BMS off
They draw power, but not a large amount ( 120 amp all the way to 300 amp models)

Let’s just say your cells were shipped with 1000mah in each cell , so 9000mah total–that’s nothing – The batteries I have these BMS on are 75 AH all the way to 360 AH — even with this big of batteries I still check them every few months for voltage drops

I don’t know if your manual or anyone told you – when you start putting those new cells in the boards – I would make sure all the cells were within .05 v of each other – the higher voltage cells can discharge way over the recommended charge current to the lower voltage cells – ruin cells, burn traces on your boards
I usually build my packs with cells fully charged-- Sort of like a Top Balance

47

Thank you!

If I turn the battery off from the app, does that mean the Bluetooth is also off? If so, how do I turn it back on?

The manual does say to check every cell’s voltage before installing, and that they should all be within 0.05V of each other. But, the manual does not explain why. Thank you for that!

The manual implies that the new cells should all come charged to the same level. I think it said they are typically 3.48 - 3.51V. So, I will check them all before I install them. If they’re all within 0.05V, then I’ll just put them in and then connect the supplied pack charger. If they are not, then I’ll have to charge them all to full with an individual charger and then hope they are all that close after charging.

48

Here is a way to charge several batteries.
I have a longer one for 18650s that can hold 20 or so cells.

Not recommended (to put it very lightly), but I didn’t feel like buying a ton of chargers and wanted to see how well it would work and I knew what i was doing. You can easily burn your house down doing this. The cells I used and the paper clips are high enough resistance that each cell won’t ever see more than 2 amps when connecting a dead cell and a charged cell (parallel charging) or even with the RC charger maxed out set to 8 amps lol (always drops to about 2A per cell, so with 2 batteries I can set the charger to 8 amps but it will only provide 4A).

Takes forever to charge 20 18650s lol.

In all seriousness, I would just invest in a ton of chargers, no way around it with that many cells. But also check the voltage of each one and throw away anything below 2.5v.

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49

:rofl: :rofl: :rofl:

Man, that rig is hilariously ghetto! LOLOL!!

I have 3 chargers that, combined, have a total of 16 slots. But, I’m hopeful that the all-new cells will be good to go and I can just put them all in my 144-slot charger… :wink:

50

If a hobby charger that can balance charge is available, you could use a similar setup, but just wire in the balance harness… I say similar, because the mechanics could/should be better.
I did something with magnets soldered to the balance and charge leads. Including the balance harness allows 6 cells in series to be balance charged. Has to be done carefully or you get failures do to connection breaks. No danger, the charger just screams and stops charging.

51

Like this ---- I can charge 24 Cells ( 3S8P ) at a time – Sometimes when I buy a large quantity , I’ll have 6 Opus chargers discharging – I use one parallel holder and one charge to charge all cells to the same level – I mostly use this holder to Storage charge cells

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52

That is a cool idea.

Not that I’m going to build a pack thing like that for charging or discharging. That is beyond my personal scope.

But, I was thinking that if I find that my new cells are not all within 0.05V of each other, then I would have to charge them all to full.

The idea of using my Opus charger and doing a discharge on them all to get them to the same level seems like a really good one.

That will run them all down to the same voltage level, right? I’m guessing it’s faster than charging them.

And, bonus, when I install them in my scooter and charge them with the scooter charger, they will be starting from a discharged state, so the BMS can calibrate itself correctly.

The manufacturer told me that it would be possible that I would need to run the scooter down to like 20% charge and then charge it up to Full in order for the BMS to be calibrated correctly.

53

With my BMS that are like yours, it takes a few cycles to establish the correct percentage of charge – Also I set my upper and lower limits to non extreme levels – for instance charge level 4.10 and discharge 3.10 – you don’t loose that much capacity and it’s a lot less stress on the cells

when you get your new cells – check them all-- put them in groups – let’s say you have 7 on one board at 3.70 and you add the last 2 that are 3.90 – that’s not that big of a deal – they will all level out with each other

Do Not put 7 at 3.90 and add 2 at 3.70 – it will cause a surge to the lower cells – are you kind of getting the logic here

54

Yes. I totally get that. Thank you!

55

I received my new cells today. I need 144, so I ordered 147, for just in case.

3 of them tested at 3.51V. The other 144 of them tested at 3.50V.

I tested all the old cells as I removed them. They varied from 80 mV to about 160mV.

So, what is the best way to dispose of this box of 144 dead cells?

56

I built the battery pack with the new cells, installed it in the scooter, checked it with the BMS app on my phone, then hooked up the scooter’s charger.

It has been charging for a 7 or 8 hours now, I think.

I’m curious about some things I’m seeing in the BMS app.

The main, top, part of the app display says the battery is at:

100%
74.88V
26.00 of 26.00 Ah

It is still charging at 0.81A.

It shows 4 temp sensors, all between 80 and 84F.

It lists all 18 layers of cells in the pack. The lowest voltage layer is 4.158V and the highest is 4.162V.

The scooter manufacturer told me that the cells are full at 4.12V.

So, why is the pack still charging?

Should I unplug it to prevent it from overcharging?

In the BMS app, there is a setting called Delta to balance. The value is 6 mV.

With my pack layers having a max difference of 4 mV and all being greater than 4.12V, I would have expected it to stop charging.

What determines when it stops charging?

There is another setting in the BMS app for “Batt over voltage”. Its value is 75500mV.

Does that mean it will keep charging until it gets to 75.5V?

This is its first charge and I am going to use it in the morning, so I wanted to let it charge to as full as it will go. After I use it tomorrow, if it’s not run down to less than 80%, I will turn it on to run at home and monitor the BMS app. I will shut it off after the battery gets below 80%, so I can leave it sitting stored until my next time using it (could be 2 or 3 weeks).

But, I am a little nervous going to bed with the charger still going and it already being at 4.16 on each cell.

57

Never go to bed with a battery charging – .81 across 9 cells is nothing and is adding very little to the cells – check the power supply feeding the charge , it probably will not stop until it equals out or the BMS releases ( shuts off )

Personally I would check all the board voltages with a known accurate meter , that way you know your BMS readings are acurate – there’s a tab in the app to calibrate all that – If it’s close I’d leave it alone

The main thing you want is your cells to be close around full charge and your desired discharge

I have a 4S8P pack I built for my grandsons powerwheel jeep – the power supply puts out 16.6 v — If I leave it plugged in until it completely levels out, it takes forever – the last 2 hrs of charge only adds about 100mah over 8 cells – nothing

58

Ask your local government for a household hazardous waste disposal location or take them to some store like home depot or best buy.

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59

I did not go to bed with it charging. It actually finished less than an hour later.

I already know my BMS readings are accurate because I checked every individual cell as I put them in. They were all 3.50V. After installing them and looking at the BMS app, it showed all 18 layers as being right at 3.50V.

New question: Is it important, when I do a full charge, to let it run that last little bit when it might only add 0.10V ot the whole pack, but it takes an hour to do it? Or am I safe to just unplug the charger when the BMS app shows that it is 99 or 100% full?

It seems like it must be important to let the charger run all the way through those final few millivolts. If it wasn’t important, why does the charger do it?

60

It’s only important if you want the cells to be 100% full. It would be much better for the longevity if you terminate the charge early, e.g. at 4.10V/90% or even less.
Ideally you would want to avoid going into the bottom and top 20% of charge as much as possible.

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