Li-ion Battreries
In the seventies I used F size NiCad’s in applications like OCXO’s later
Rb’s for power backups. Later switched to Ni-MH in all cases needed complex
charge control and cutout to protect batteries. Today I have switched to
Li-ion mainly because of the low cost reliable power management including
protection of the cells. The repeated problem has been a reliable source.
Over the last couple of years I have spend more than $ 300 only to get most
the time junk, no real reliable sources. That has changed.
Fasttech does offer cells that they have tested and is a source for those
living outside the US. Even though they claim shipping free once you go to
checkout you get hit with $ 29 shipping.
After multiple trials I finally found a perfect US source. genuinecells
(http://myworld.ebay.com/genuinecells) is located in Florida and my
thought was if disappointed I could afford to ship back. Gen responded to my
request for information with data sheets and additional information. I
purchased 2x Samsung 35E 3500mAh 10A 18650 High Drain Rechargeable Battery
INR18650-35E
(http://www.ebay.com/itm/112173495496?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT) for two reason 10 A load and good price. These
cells have no protection, which I want, since I will for our applications
stack 4 with a 4 cell controller and in two application also parallel cells
for a total of 8. I have now completed my tests and concentrate my
battery work on using these cells.
After having tested 26650 cells with disappointing results my focus is on
18650. I am sure there will be 26650 cells available, but right now our
focus is on 18650.
I have no connection in any way with these two sources, but think it may
be helpful for those that look for batteris and do not want to go through
the process I went through.
Bert Kehren
Hoi Bert,
On Sat, 21 Jan 2017 08:08:22 -0500
Bert Kehren via time-nuts time-nuts@febo.com wrote:
purchased 2x Samsung 35E 3500mAh 10A 18650 High Drain Rechargeable Battery
INR18650-35E
(http://www.ebay.com/itm/112173495496?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT) for two reason 10 A load and good price. These
cells have no protection, which I want, since I will for our applications
stack 4 with a 4 cell controller and in two application also parallel cells
for a total of 8. I have now completed my tests and concentrate my
battery work on using these cells.
After having tested 26650 cells with disappointing results my focus is on
18650. I am sure there will be 26650 cells available, but right now our
focus is on 18650.
I have no connection in any way with these two sources, but think it may
be helpful for those that look for batteris and do not want to go through
the process I went through.
Some small remarks: 18650 is by far the most common form factor
of Li-Ion batteries on the market. This is IMHO the better choice
than the 26650 if you want to be able to replace them in 10-20 years.
If you stack Li-* batteries, you will need to have a controller that
monitors each cell individually while charging or has some other means
of ensuring that none of the cells are overcharged (or rather that they
are charged the same amount). This kind of circuit is called balancer.
A protection circuit does not replace a balancer. The protection circuit
is only to protect against catastrophic failure. Ie it is still possible
to overcharge a battery even if it has a protection circuit. You also do
not know what the protection circuit does to protect the cell. There are
a lot of chips out there, that simply open a switch and thus disconnect
the cell. In this case, the protection circuit of one cell will disconnect
the whole stack and break charging.
A lot of the multi-cell Li-Ion charger chips have integrated cell protection
circuitry. Ie if you use one of them, you will not need an additional
protection circuit. But be aware, the regulation for battery protection
circuit states that the circuit has to be wired fix onto the battery
in a way that this connection cannot be broken (without breaking the
housing of the battery pack). The reason for this is, i think, pretty
obvious. I would recommend that you solder each cell indidividually
into your circuit instead of using some kind of holder. Or if you are
using a holder, make it such that there is no chance any of the cells
can be accidentally short circuited.
Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.
Just a quiet message that needs to be said:
18650 style LiIon cells are indeed one of the most common
styles of LiIon cells, but with their popularity comes a
great deal of fraudulent sales activity.
The 18650 cells are used in all sorts of trendy gadgets, like
the vape appliences for niccotine addicts, over powered green
laser pointers, and vibrators for... well... urhmm...ahhh, I can't
say....<blush>.
I went on a quest to try to buy 18650 cells for cheap prices,
and then tested them on my Christie CASP battery charger/tester,
and I found that I could buy the things wrapped with the labels
of Samsung, Sanyo, UltraFire, PowerSonic, and probably a dozen
other brands, labeled with 3000 through 9800mAH capacities.
In testing, I found two things. If the batteries came from
eBay, or Amazon, they would weigh between 1/3 and 1/2 as much
as the manufacturer's spec sheets said they would, and they
would test at between 400 and 500mAH. And that was with allowing
them to discharge until their internal protection circuitry
shut them down... in other words to an unsafe level.
So, the moral of my story is know your sources, and do test
every one... a twist on the old saying: Don't trust but verify.
I quit the project, as I feared that the high number of items
I was declaring as counterfeit for refund, would soon catch up
with me and render me unfit for ebay and Amazon purchases.
The safest, surest supply I have found is discarded laptop
batteries for Dell computers. Bust them apart, and you will
find that all but one of the cells is in good condition. The
one bad cell can almost always be resurrected by charging it
manually to 4.2V at less than 1C current.
Note, they won't have the protection circuitry installed as part
of the cell, but you can buy that part on eBay with pretty good
results..
-Chuck Harris
Attila Kinali wrote:
Hoi Bert,
Some small remarks: 18650 is by far the most common form factor
of Li-Ion batteries on the market. This is IMHO the better choice
than the 26650 if you want to be able to replace them in 10-20 years.
If you stack Li-* batteries, you will need to have a controller that
monitors each cell individually while charging or has some other means
of ensuring that none of the cells are overcharged (or rather that they
are charged the same amount). This kind of circuit is called balancer.
A protection circuit does not replace a balancer. The protection circuit
is only to protect against catastrophic failure. Ie it is still possible
to overcharge a battery even if it has a protection circuit. You also do
not know what the protection circuit does to protect the cell. There are
a lot of chips out there, that simply open a switch and thus disconnect
the cell. In this case, the protection circuit of one cell will disconnect
the whole stack and break charging.
A lot of the multi-cell Li-Ion charger chips have integrated cell protection
circuitry. Ie if you use one of them, you will not need an additional
protection circuit. But be aware, the regulation for battery protection
circuit states that the circuit has to be wired fix onto the battery
in a way that this connection cannot be broken (without breaking the
housing of the battery pack). The reason for this is, i think, pretty
obvious. I would recommend that you solder each cell indidividually
into your circuit instead of using some kind of holder. Or if you are
using a holder, make it such that there is no chance any of the cells
can be accidentally short circuited.
Attila Kinali