why are there no limit-chargers?

I think the issues is the term charger
I presume you calling a psu a charger just look at hobby chargers quite common thay let you pick your end voltage.

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Not just bike stuff look at power tools from Dewalt, makita, milwalki, bosh etc thay all say 18v when thay are 18650 2p5s so in reality 21v fully charged

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Just a side note…
IMO an important difference between a “charger” and just a constant-current (CC) power supply (which all chargers are) is that the charger knows when to stop. Typically when the bulk charge rate has dropped to 1/10th or 1/20th of its starting value. For example. A 10A charge would stop when the current dropped down to 1A or 0.5A (respectively).

Hook a CC power supply up to a pack and it will continue trying to charge the pack for as long as you leave it connected. This speeds up aging of the cells in the pack and should be avoided.

You can charge with just a power supply but that, IMO, doesn’t make it a charger.


220€ :slightly_smiling_face:



I have the cycle satiator and it is rad. You can program profiles with whatever amps and max volts you want. It has a screen with charge data and even graphs, plus lots of safety features and it’ll tell you what happened if anything goes wrong. Not to mention a solid reputation and customer service. Only downside is you gotta pay for what you get.

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I have the habit of charging overnight leaving the batteries hooked in the power supply. Never really paid attention to 1/10 cutoff as I most often terminate my charging process long after the packs’ current draw hits zero. So just how much damage does this habit incur to my packs?

Too many unknown variables for us to be able to quantify the damage for any particular pack. All we can say is that the longer it is done, and the higher the voltage, the faster your cells degrade.

If you don’t feel that your packs are dying early then it might not be a (practical) issue you need to worry about.


How long is a pice of string. Once the li-ion cells are charged and you keep holding the voltage at 4.2 it starts to plate the surface this reduces the max current flow and makes the cell heat up faster as well as ruducing the total amp hours this is some thing that happens little by little. Bare in mined that just by charging, discharging, age all degrade the cell (damage) if it didn’t it you be able to use the battery forever but most 18659 have 500ish cycles until thay down to 80% capacity

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Get a Wyze Plug and set the outlet on a timer… maybe…

so the cells don’t mind being cut off at full charging amps? btw, is there a comprehensive battery guide? I’d have lots of questions on the issue, one of them being what does count as a full cycle, when I have about 500 cycles before 80%, does that mean full cycles? totally empty (what’s empty, 3V?) to 4.2V? or do 3 partial charges also count as one full cycle? no manual or website or manufacturer every goes into these subjects in my experience…

I’d start with the manufacture spec sheet


This is a compulsory part of the charging cycle and can potentially cause fires if not followed.

Thanks. Guess I worry too much.

I have this small diy UPS consisting of a 3s3p hooked in parallel with our wifi’s 12.2V power supply. It’s like charging the pack without ever disconnecting it from the charger. No fireworks so far after over a year of continous operation.

Not at all. You can interrupt the charging cycle at any time. Packs do not explode if we stop putting energy into the cells. :slightly_smiling_face:

An incomplete charge means less range though, of course.

Leaving a pack connected to a powered down charger or power supply can cause problems though. It can cause the pack to be slowly discharged and a badly designed power supply or charger could potentially be damaged by this.

Not really, the range of topics could fill bookcases…and do.
@Darkie02’s recommendation of checking the datasheet is a great start though.

A full cycle is the discharge of a cell from its rated fully charged voltage (typically 4.20V for standard Li-Ion) down to its low voltage cutoff point (typically 2.5V) equal to the rated capacity of the cell and then back up to its fully charged point, all at a certain temperature and certain charge and discharge rates.

For a 3000mAh cell this means that a discharge of 1500mAh, and then a full full recharge, is 1/2 of a cycle. You would need to do this twice to equal a full cycle.

The rated cycle life of a cell is how many full cycles the cell can do, minimum, before its capacity drops down to the quoted number, typically in the 60%-80% range. If a cell is rated for 500 cycles then theoretically it can do 1000 half cycles.

But we can’t get crazy about these numbers. A single full cycle ages a cell differently than two half cycles. Cycling at different charge and discharge rates and different temps changes the cycle life of the cell.

It can be verrrry hard to compare the cycle life ratings of different cells because of this…these details matter.

The noob questions thread is a great place to ask any questions you might have. Lots of people there willing to help out.

It would take many books to even begin to explain all that is involved. :slightly_smiling_face:

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:scream: Whoa…that is a terrible thing to do to a pack.
I have no idea what the safety risk might actually be but those cells are being damaged. I urge you to get a new pack with a BMS.


What are you saying causes this fire risk?
Interrupting the charging? That doesn’t cause any increased risk.

Or are you’re referring to not charging at the correct charge rate or some other type of abuse?

Not terminating the charge and holding the cells at max voltage for long periods of time can lead to cells over heating and thermal runaway witch is a fire risk.

That terminating the charge is part of the charge proses on every li-ion I have seen and used.

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Ahhh…okay, I agree, continuous charging damages the cells. I thought you were referring to something related to stopping the bulk charging.

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true, exactly as worded

Exactly that, a full cycle. From 4.20V to 2.50V. Typically when we ride our boards, we are putting somewhere around 1/5 to 1/2 cycle on the cells.

Yes; a cycle is equal to 1.0 cycles

2.50V on most models (but I highly, highly recommend you don’t approach that)

If they are all 0.333 cycles then yes all put together they would add up to one cycle.

Have you looked at esk8 news?


While looking for more info bout the subject matter, I found this video of a dude figuring out how he’d undercharge / float charge his 4s pack. Basically he’s tryin to use li-ion as capacitors.

It got this really intriguing reply down comment section.

How legit is it?

It has some merit. Holding Li-ion cells at their 4.20V charging voltage will definitely age them faster. It’s just a lousy thing to do to them.

While holding them at a lower voltage is not a standard procedure, and perhaps not even recommended, it is certainly better than doing it at 4.20V.

There could be a big difference though between continuously charging them at 3.80V and charging them to 3.8V and then letting them self-discharge to perhaps 3.7V or 3.75V before topping them off to 3.8V again.

The latter would be much better for the cells IMO and accomplishes much of what someone might want to do by having their cells always at 3.80V. There’s not much capacity difference between 3.8V and 3.7V.

I guess you can just use a standard CV power supply though for the float charging (once the cells are charged) versus having to use a charger for the occasional topping off of the cells.

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