Here is a good used source for 18650 batteries

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

1500mAh is more than good enough for flashlights and USB power banks, and certainly better than some of the crap China will sell you...

This is very true I have seen a lot worse batteries before I would not even think about using

I might have a use for these in some solar lights in the yard because the ones that they sell for this purpose are real crap

[Th3_uN1Qu3]

Re: Here is a good used source for 18650 batteries

You may be interested in this thread about rolling your own - quite literally.

[eccerr0r]

Re: Here is a good used source for 18650 batteries

Thought that li-ion cells usually are specced for capacity from 4.1 or 4.2V (and even worse some people use 4.3V) to cutoff, so you will get more capacity than just using 3.9V.

[Th3_uN1Qu3]

Re: Here is a good used source for 18650 batteries

I know I've read a lot of battery papers and 4.05V is the sweet spot for maximum voltage. Above that, the lifespan of a Lithium battery decreases exponentially.

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

For testing purposes I just use 4.2 but what ever the BMS protection board does is fine as long as it not over 4.25 and not less than 3.8

[eccerr0r]

Re: Here is a good used source for 18650 batteries

BMS tend to stop charging at 4.3V or so. They don't care about lifetime, they only care about rapid autodisassembly of the cells...

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

Well I have taken apart the air compressor and it does have two battery voltage monitor modules and a dual input module that separates the battery inputs but is not isolated from each other

One module controls the motor which has three wires so I not sure what type of motor it is the other module has the battery wires going to it

So my plan to have two power supply battery packs is going to work all I have to do now is do testing on a bunch of batteries and get them in battery pack cases and hook them up and put the air compressor case parts back together and do some real world testing

Well I have bought two of the 5 amp hour battery pack and they are using Samsung 2500 batteries this why the battery pack preform so much better well worth the money for these battery packs right now they have a sale on save $18.00 when buying two battery packs

I would have taken them back and got my money back if they had not been brand name batteries

My plans have changed I will probably buy two more of them when they go back on sale again

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

Here is the more
Just as I thought the BMS balancing protection board is part of the charging board look at the top and bottom of this board I have never seen this before done like this

I like the idea that you can use the battery connector in another case if you want to

When I charged the 1.5 amp hour battery I did not notice this issue it’s when I was charging the 5 amp hour battery is when I noticed this —>

There is an issue with the switching transformer for this battery charger the transformer gets very HOT to the touch and you can smell that it getting very hot

I going to see if there a way to modify this charger because I do not like the fact that the transformer is getting this hot

Even if this might mean that I have to use my SkyRc charger to charge the battery packs

[eccerr0r]

Re: Here is a good used source for 18650 batteries

I've noticed some "current limiting" PSUs don't *really* current limit, rather it just depends on the controller from self destructing, so it's really "wattage limiting"... Not sure if this is the case when "wattage limiting" still allows the transformer to overheat.

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

I've noticed some "current limiting" PSUs don't *really* current limit, rather it just depends on the controller from self destructing, so it's really "wattage limiting"... Not sure if this is the case when "wattage limiting" still allows the transformer to overheat.

Is there a solution to this issue

[Th3_uN1Qu3]

Re: Here is a good used source for 18650 batteries

Is there a solution to this issue

Yes there is. Most power supply designs from the past 20 years use current mode controllers, so the quickest and easiest solution is to increase the value of the resistor in the source of the primary switching MOSFET.

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

Yes there is. Most power supply designs from the past 20 years use current mode controllers, so the quickest and easiest solution is to increase the value of the resistor in the source of the primary switching MOSFET.

Can you please point out the resistor in question so I know for sure which one you are talking about

I have decided to take a different route on this charger but I also have another one so please post what you have in mind and I will give it a try

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

Well what I have found out is that you have to set the voltage at 21.5 for it to work correctly if go pass this point it goes into an error if go lower than 20.5 then it does not charge correctly but the charging circuit does not seem to get very warm so the issue is with the primary side of this switching power supply it is not designed correctly it should not over heat the switching transformer like this

You set it for 20.1 volt however it does not completely charge the battery fully it about 4.1 volts per cell which I could live with

But where do I find a switching power supply that has an output of 21 volts this is hard to find 24 volts is more common

One thing I noticed is that the capacitors in this device are not very good ESR values
( at least 1/3 higher than a brand name capacitor )
for a new non brand capacitors
So I am going to replace the capacitors that are less than 100uf and see if this makes a difference or not

[eccerr0r]

Re: Here is a good used source for 18650 batteries

Yes there is. Most power supply designs from the past 20 years use current mode controllers, so the quickest and easiest solution is to increase the value of the resistor in the source of the primary switching MOSFET.

This is actually wrong, it still simply limits the wattage.

To get full current limiting you have to design your own add-on circuitry.

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

This is actually wrong, it still simply limits the wattage.

To get full current limiting you have to design your own add-on circuitry.

How would I go about doing this project part number would be very helpful thanks

Are we talking about a LM338 or something similar using it in current mode

The next question is exactly where do you put the current limiter right after the ( rectifier ) the back to back diode coming from the switching transformer or somewhere else

[eccerr0r]

Re: Here is a good used source for 18650 batteries

It's probably not worth the effort as you have to redesign the whole circuit for true current limiting for SMPS chargers - a significant change is necessary starting with current detection. Of course the current detection needs to be at the battery pack when dealing with switching supplies.

The "simple" solution using the LM338/LM317 as current is not as simple as one would think because of the voltage drop.

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

I found a 21 volt battery charger made for 18650 4.2 volt cells and also found a balancing board only from the same EBAY seller so I going to order and will have to wait a month to get the parts

Charger

https://www.ebay.com/itm/13341551537...MAAOSw9dteblyQ

Balancing board

https://www.ebay.com/itm/19226128370...sAAOSw3mdZdaQT

I will have to remove one battery cell parts to make it 5 battery cell but this is fairly easy to do

Other options

https://www.ebay.com/itm/19202702378...kAAOSwTzpfn4FZ

https://www.ebay.com/itm/39353821908...Cclp%3A2334524

[eccerr0r]

Re: Here is a good used source for 18650 batteries

interesting...now they make balancing boards without protection, like they had make protection boards without balancing. Really need to have both functions IMHO.

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

interesting...now they make balancing boards without protection, like they had make protection boards without balancing. Really need to have both functions IMHO.

I would agree with you on this but a lot of times you can find protection boards all day long but finding both is a lot harder to find

I like the idea that someone thought about doing this because now it is going to be a lot easier to get things together at least for me it will be

Because I need a 32 volt BMS balancing protection board for a battery operated LED yard that I have that the switching power supply fried because of bad capacitors that leaked all over an encapsulated board what a mess in the metal enclosure that was made for the switching power supply board

My son works nights and on his days off he want to clean his car in middle of the night and I do not want another yard light near the house on every night yea I know I could put one out there that has switch but he would not remember to turn it off so if I put a solar LED yard light out there and he forgets to turn off the switch he just will not have any light that night ( yea I know that you might find this mean oh well )

[eccerr0r]

Re: Here is a good used source for 18650 batteries

sigh. miss the "good old days" when balancing is chemically done, like in lead acid batteries...

Just add water.