Need to top up the discharged 10.8/4.4Ah volt battery pack approx 10% of full charge; is it ok to hook it with series resistor to say 13 or
15 volts source in order to have 200-300 mA charging current to start with(yes the proper way is to have a Current and than voltage charging but will the mentioned do in this case without destroying the pack) Thanks
Lithium Ion cells need precise voltage control of maximum voltage. For a 10.8V pack the voltage should not exceed 12.6V.
If you connect a 15V supply make sure you are ready for a potentially dramatic failure. With luck the protection electronics in the pack will protect you. I wouldn't rely on it.
could insert 4 diodes but actually what is needed is to remove the reverse charge due to overdischarge so how about a 2 second shock with 15v 500ma source
If you let the cell voltage of a LiIon battery fall below some magic number (I can't remember what it is, but it's waaaay above 1/2 the charged cell voltage) then you've trashed the cell -- if it's reverse charged, take it out to the nearest shooting range and put on a light show.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
As John says the battery is probably already damaged beyond repair.
These things really can fail spectacularly, as can be seen about 2 minutes into this video:
I suggest you get a new battery and a proper charger but if you really really want to try and recover it you could do as you suggested above but monitor the voltage across the battery terminals as it charges and then manually stop charging before you get to 12.6V, well before you get to 12.6V if you only want a 10% charge.
As I said though, Li-ion batteries can burst into flames if overcharged or damaged so be VERY careful - perhaps charge the battery outside well away from anything which will burn and use long wires so that you can keep your distance.
Sorry, I meant Tim, not John.
The problem with lithium batteries is that they are extremely sensitive to overcharge and over-discharge. Due to this, the only safe way to charge them, is to monitor the voltage of each cell and make sure it stays within spec.
Some batteries have built-in protection circuitry to take care of these issues. If your battery does have such protection, you might be OK. I still strongly recommend a proper charger, though.
-- RoRo
The proper way is to monitor the temperature as well. The peak voltage is very small and can be inverted.
i've re-charged my model planes flight pack with my bench top power supply, only did it as the proper charger had died on me, and it was too good a day to pass up a flight,
my batteries are lithium polymer, so there's no protective metal casing as with the li-ion batteries, so when a li-po goes up, it goes up spectaculary.. but most of those you tube videos of li-po's bursting into flames whilst on 'charge' are staged, usually to sell a protectice charging bag or similar, they are deliberately over charging the batteries, with no current clamping in place.
but a bench psu with a CV and CC function does pretty much what a proper charger does,
i set the voltage to the equivelent of 4.20 volts per cell, (it's slightly different for li-ion) and the current to 2 times the pack capacity (my packs are 5C charge, 30C discharge jobbies.
as the pack charged, the voltage rose limited in current by the psu being in constant current mode, once it reached the max voltage setting, the psu switched to constant voltage mode, and the current drops as the pack gets it's final 10% of the charge, which is basically what a proper charger does, just with a few electronic safety features, my safety features were my eyes, thermocouple in the outer wrapper of the pack, and a little understanding of how my pack should be charged, obviousely i was present the whole time it was charging.
BUT my packs were not so low that the proper chargers wouldent charge them, and unfortunately as has been mentioned, when the cells get too low they get dammaged, and not many people have any luck reviving them,
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is it ok to hook it with series resistor to say 13 or
NO IT IS NOT! Destroying the pack is the least of your worries. Worry about destroying yourself or burning down your house. "Mommy, why is daddy blind?" "Because he miscommunicated on the internet."
Problem with giving advice to people of unknown experience and capability is the communication gap. You might get away with using a 12V supply in the manner you suggest. Problem is that when I say 12V, I mean that I set it to 12.00V using calibrated measurement instruments. To you, 12V may mean "that radio shack power supply I used on my CB" that actually puts out 13.8V if it's regulated and possibly much more if not. 12.00V probably works. 13.8V probably makes fire.
Voltages are CRITICAL with lithium batteries. The number on the label on your wall-wart ain't sufficiently accurate to keep you safe.
Why can't you use the charger designed for it?
For lithium batteries, a temperature monitor can be used as an additional safety measure, but it is not useful for determining full charge. Normally, a fully charged battery will not even feel warm to the touch, even when charged quite quickly.
Lithium batteries are charged to a specific voltage, very much like lead-acid batteries.
Maybe you are thinking of nickel-based batteries (NiCd and NiMH)? With these, full charge is detected by the slight voltage drop that occurs because the battery's internal temperature starts to rise. If you are terminating charge based on external temperature measurement, you will always overcharge slightly, since it takes some time from full charge until the whole battery heats up.
-- RoRo
HP probably puts reverse charging protection in Notebook Batteries but could be the on board charger cannot handle a deactivated battery pack- if so,should one reactivate each cell or the whole pack and how to do it?
From
Caution! LI-IONEN ONLY!
All Lupine batteries contain a protective circuit (PCB) which prevents the battery from damage such as incorrect charging, deep discharging, short circuit etc. In these cases, the PCB deactivates the battery.
The current versions of ChargerOne and MicroCharger will automatically re-activate such a deactivated battery. An older ChargerOne, however, will not be able to identify the battery and charge it.
But help is on the way: Use the 12V power supply to re-activate your battery. !!!The power supply needs to be connected to the socket. Now connect the hollow plug to the positive pole within the male plug of the battery (the positive pole is the one beneath the =93roof=94). The outside of the hollow plug will then touch the negative pole within the male plug. After that, the battery can be charged as usual.
also!!
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