Charging Lipo's for Dummies

[cAptainslow]

Seeing as though said title doesnt seem to be in the top 10 at smiths, here is a daft question regarding charging Lipos for a novice...

I have never charged lipos before and i am slightly concerned about the possibility of losing my eyebrows in a flash of chemical horribleness

I have a Core RC UDC20 charger and some Core rc 3250 packs, normally i would just follow the instructions but to be honest they are about as much use as T*ts on a fish!

1: The pack says 1c 2 cells(?), i have set the charge current to 3.3A...is that ok?

2: I presume the voltage should be set to 4.2v per cell so 8.4V... .ok??

3: Do i use the same figures when ballancing?

4: How the hell do I know when they are done...I pressume it will knock off when complete but it reaches 8.4v and doesnt, then i start to sweat a little and hide behind my welding screen for a bit then knock it off manualy!?!

I know its lame but I aint got a clue to be honest.

Help appreciated!!

cAp'nslo

[mark christopher]

3.3 amps is fine
2s so should be 7.4 per pack, peak cut off 8.4, the charge will not terminate at 8.4 volts initially, the voltage will remain at 8.4 and the amps will drop slowly to zero, lipo charges ant CV (constant volts) not as nimh where it keeps putting max amps in until the cells are charged

[cAptainslow]

Cheers Mark, so should i drop the voltage setting down to 7.4 and expect it to switch off eventualy when the amps drop low enough?

[JJ The Boat Wizzard]

If You Put Your Charger In LiPo Model Select 3.3A And Select Go It Should Cut Off Automaticly You Shouldnt Need To Set The Cut Off Voltage Apart From When Discharging and theres no need for that with lipos unless your cycling them

Hope This Helps
John

[N7ELA]

Originally Posted by cAptainslow

Cheers Mark, so should i drop the voltage setting down to 7.4 and expect it to switch off eventualy when the amps drop low enough?

Nah you can put 10 volts in your lipos and not cause any bother. But just leave it on 8.4, C is the unit of charge in coulombs.

One coulomb is the amount of electric charge transported in one second by a steady current of one ampere.

[cAptainslow]

Excellent, thanks very much. I can now remove my gauntlets and welding screen!!

[mark christopher]

Originally Posted by N7ELA

Nah you can put 10 volts in your lipos and not cause any bother. But just leave it on 8.4, C is the unit of charge in coulombs.

One coulomb is the amount of electric charge transported in one second by a steady current of one ampere.

think if you try that you may well loose your place at a meeting and loose your brca licence, its NOT safe to put 10 volts into a 2s lipo pack they will go up in flames..................... highly danjerous to do that

the "c" rating refers to capacity, so a 5000mah pack with a charge rate of 1c would be 5 amps.


not sure where your getting your info, but its bolloxs, please dont post stuff on here that will endanjer others.

[bodgit]

also to be on the safe side get yourself a lipo bag for about £10 if they ever do go off it will contain them, You,ll need one anyway if you are going to charge them at a meeting.

[Dagger Thrasher]

I imagine the "voltage" that you're adjusting will be the charger's "peak cut-off", and not the nominal voltage of the pack as all LiPo cells are 3.7V at rest. You might want to set the cut-off lower sometimes for storage, which is why the setting is there...but in this case, you want 4.2V per cell. A charging bag is always a good idea as Bodgit pointed out, and 3.3A charge rate will be perfect for your pack.

Nah you can put 10 volts in your lipos and not cause any bother. But just leave it on 8.4, C is the unit of charge in coulombs.

One coulomb is the amount of electric charge transported in one second by a steady current of one ampere.

You can put 10V into a 2S pack if you have a strong desire for 3rd degree burns and to set the building alight, but short of that, it's a VERY bad idea.

[DCM]

Originally Posted by N7ELA

Nah you can put 10 volts in your lipos and not cause any bother. But just leave it on 8.4, C is the unit of charge in coulombs.

One coulomb is the amount of electric charge transported in one second by a steady current of one ampere.

never post whilst being

a) intoxicated, or
b) under the influence of an illegal substance!!!

As for LiPo bags, I am still very unconvinced in LiPo bags, I understand their use and what they do, but personally, as long as the charger is correct, then that bit is safe, it is in the use in a car I would bet more worried about!

[ads0021]

Has anyone had a lipo go on them? I've seen them on youtube but always on purpose. Has anyone had one go through normal use? I've seen or had friends see about 6-8 intelect cells explode. And I mean EXPLODE! But I've yet to hear of a lipo going. Judging by the hype that's been going around we're all lucky to be alive being in the same room as a lipo!!!!

[DCM]

I have heard of a couple swell up, but thats it, not heard or seen a LiPo get angry with someone.

[cAptainslow]

yeah exactly, thats why I asked! I thought all Lipos wandered around with their trackies tucked into their socks wearing hoodies and carrying flick knives!

Once again cheers fellas.

[DCM]

haha... Asbo Cells....

[GRIFF55]

Mark, doesn't it say on the rear of trackpower cells that you can put a fast charge into them that is more than 1c?

[ads0021]

As far as I am aware SMC suggest a charge rate up to 2C(2 times the capacity in amps).

Does anybody else remember the early days of thermal charging cells when one loose probe would result in running across the village hall with a pack of cells popping and spitting acid everywhere!!

I think it's all gone a bit mad over safety at the moment. At my local club they have said that if anyone is caught with lipo's over 8.4v they will be asked to leave the meeting, banned from the club, and then the BRCA will ban them from any BRCA meeting too!

Can I see the test results where charging to 8.5v results in certain death!!

I have no desire to kill myself or any of my fellow racers! And I have never, or will I ever over charge my lipo cells at a meeting! But I really think there is a huge amount of scare mongering going on!! And I dn't really know why.

If people want to put right tht's fine. But please can we start using FACTS.

If this is more an issue of fair racing can we adjust the attitude to suit. If you are going to ban people for overcharging lipo then should we do the same for running a wing that is too big?

[neiloliver]

Charging at higher current rates does not really do you much good, mostly because the time taken to get to 4.2V per cell will be reduced and then the current starts to taper down.. so doubling the charge current does not half the charge time. This is very noticable at lower temperatures when the internal resistance is higher.

Charging at 1C is perfectly reasonable and with two packs you wont have any problems charging between heats when you have an hour per round.

The term "peaking" should not be used when taking about Lithium Polymer. In a NiCd or NiMH cell the voltage does reach a 'peak' at top of charge and then drops slightly in over-charge. With Lithium Polymer the 4.2V point is normally reached at about 80% state of charge and the remaining 20% is put in during the constant voltage portion of the charge (This 80% figure will vary depending on age, temperature etc but is a good guide for C/2 charging)

Anyone who charges at voltages above 4.2V per cell should be asked to leave a meeting as it is dangerous, pointless and a more than a little stupid. Safety testing for UN transporation etc do include over charging tests but you dont drive your car into a wall to see if the airbags work do you?

Each of you had a laptop or mobile phone. The lithium ion or Lithium Ion cell in that device has a protection circuit which will either stop charging (or shunt charge current away) if one or more cells reaches 4.275V. Not becuase the cell will suddenly explode at this voltage but becuase it's cycle life will be seriosuly reduced if charged at a voltage >4.20V.

If you use a balancer during charge then this reduces the risk, especially if you have a NiMH/LiIon charger where you might set it on the wrong program.

N

[mark christopher]

Originally Posted by GRIFF55

Mark, doesn't it say on the rear of trackpower cells that you can put a fast charge into them that is more than 1c?

thats very true but

1/ the poster does not have trakpower, he has core cells
2/ charging at 2c does nothing to the volts you just put more amps in, the voltage will still level and remain at 8.4v if your charger is set up correctly.

Neil has cleared the rest up above

[Dozey83]

Originally Posted by ads0021

Has anyone had a lipo go on them? I've seen them on youtube but always on purpose. Has anyone had one go through normal use? I've seen or had friends see about 6-8 intelect cells explode. And I mean EXPLODE! But I've yet to hear of a lipo going. Judging by the hype that's been going around we're all lucky to be alive being in the same room as a lipo!!!!

i have been at a meeting where someone had a lipo 'go up' on him,

basically he had removed a part of the case to get it to fit his car, he had also grount down the piece that was overhanging this part of the cell again to make it fit, in doing so he had shortened the screw that went through said part, then when putting his car back together in a rush he put a full length screw in instead of the shorter one, and pierced the lipo as he tried to remove it from the car, this caused the cell to start smoking lots and lots and lots, he then ran across the hall and threw the smoking cells onto a patch or dirt away from anything at all and left them there!!

the thing that is dangerous about lipo is not that they will explode, but that fact that they set on fire when damaged, the problem is that they CANNOT be put out (not in any easy way anyway!) as they create their own oxygen for the burn.

i would reccomend as many others have for this to charge at 3.3V, but i am still not sure about lipo sacks, i use one for transporting my cells, but unless it is a club rule i dont use on while charging, as a friend puts it, 'I would much rather see the cells expanding and stop the charge and deal with them than plunge my hand into a bag not knowing what i was about to find.'

think thats my longest post on here! woohoo me! lol

[mark christopher]

Originally Posted by LosiRob

i have been at a meeting where someone had a lipo 'go up' on him,

basically he had removed a part of the case to get it to fit his car, he had also grount down the piece that was overhanging this part of the cell again to make it fit, in doing so he had shortened the screw that went through said part, then when putting his car back together in a rush he put a full length screw in instead of the shorter one, and pierced the lipo as he tried to remove it from the car, this caused the cell to start smoking lots and lots and lots, he then ran across the hall and threw the smoking cells onto a patch or dirt away from anything at all and left them there!!

the thing that is dangerous about lipo is not that they will explode, but that fact that they set on fire when damaged, the problem is that they CANNOT be put out (not in any easy way anyway!) as they create their own oxygen for the burn.

i would reccomend as many others have for this to charge at 3.3V, but i am still not sure about lipo sacks, i use one for transporting my cells, but unless it is a club rule i dont use on while charging, as a friend puts it, 'I would much rather see the cells expanding and stop the charge and deal with them than plunge my hand into a bag not knowing what i was about to find.'

think thats my longest post on here! woohoo me! lol

think its fair to say if the dick had not modified the case, (not allowed anyway) then the cells would not have been danjerous.