If internal resistance between charger and cell is 0 - yes, that’s how it should work (but only BEFORE termination!).
But not if there’s internal resistance between charger and cell. It just can’t know about it (and account for it).
i actually didnt know this… thanks…
on a side note several of my other chargers will charge cells to 4.22 or 4.23v (measured hot off the charger)… on the back of the charger they say 4.20v +/- 0.05v… so i guess that technically is correct… i wonder if that shortens the life at all of the cell? the articles ive found on google comment about charging to 4.3+v but nothing about 4.25
edit: i have a panasonic 3400 ncrb on charge right now - i am going to try a similar discharge test today… im hoping that the sanyos are just “tired” and my charger isnt bricked.
this story is about to get even better… i have 2x panasonic ncrb (flat top)… i went to attach the magnet leads to charge and the solder blob i had on the top became dislodged and wedged itself underneath the retaining ring.
before it even happened i knew what was coming… i grabbed the battery and moved quickly to the sliding glass door… the cell was nearly too hot to hold by that time… opened the door and threw it into a snow pile
POOF.
im not buying any unprotected batteries again…. EVER.
created a short?
got any pictures of the poofed?
wow.. this is getting offtopic now ;)
not yet… im still too afraid to go outside…. lol.
the battery started hissing as i opened the door so i threw it as hard as i could into a 4’ snow drift… the snow insulated whatever happened pretty good… although i still heard a small… rumble
time to head over to fasttech and order up some protected ncrb cells!
do it right or do it twice i guess….
getting back on topic… i am charging up a aw 2000mah IMR right now that is literally brand new… i will run a discharge test shortly… its at 4.08v (4.0v per my DMM) and charging now at one amp (cell one cycle down to 3.7v)
in the mean time i ordered 2x PROTECTED panasonic NCRB cells from fast tech… worked out good because i had to buy some other mod parts…
great prices there! seems to be the best price on NEW panasonic protected 3400mah cells (if you want usa shipping it looks like Kumabear is best)
@JM, can you please go outside and document it. Don't touch anything, just take pictures of what happened. This could be important for future reference.
When you do decide to clean it up, make sure you wear gloves when you pick up the parts and drop it off at your nearest hazardous waste place.
And finally, good job on throwing it out the door when it started to heat up. I have done that with a few of my cells (pitched them against a fence) when I thought they were gonna vent, but so far I have been lucky enough not to have that happened.
Also, if you do take pictures you can email them to me at scarudabest @ gmail.com and I will post them up for you. (Or you can post them yourself)
scaru - my apologies… i did not take pictures… about 20 min ago my wife and i agreed to get this thing out of here and asap - i double bagged it and drove down the street to the dump/landfill/recycling center and they took it off my hands…
the cell appeared to only vent and not explode - the cell appeared nearly identical to when new - except for discoloration around the top near the vent (i assume due to temp)… i didnt bother to try and measure voltage or anything i just got rid of it and recycled it right away.
i guess this is what the cell is supposed to due - vent to relieve pressure and not explode…
i assume the rumble i heard after i threw the cell into the snow pile was just the battery venting? either that or my heart skipping a few beats
again - sorry for not taking any pics - i thought about it briefly but after the adrenaline rush of digging this thing out and bagging it i just wanted to get rid of it and not have anything else happen
Ok, glad to hear you disposed of it safely. If you threw it into a snowbank then the rumble was probably the gasses hitting the snow and shoving them out of the way. Glad to hear that there were no injuries.
i also took the sanyo cells (mentioned earlier) and another panasonic ncrb cell that i had a solder blob on to be recycled… the sanyo cells seem to be tiring already… i tried them last night in a xpg2 p60 light and after 30 mins the light dimmed (low battery warning)
obviously they are no where near the 2600mah rating - i wonder why they had such a short life… they probably had a dozen max cycled on them and they were stored at about a half charge… i have 4 of these cells in my skyray king that seem to hold up better and they are the same age?
weird…
the imr i have charging on the hobby charger seems to be charging correctly! the CC/CV routine appears to be working fine…. charging at 1 amp and 4.2v - i checked the Vbatt and it was 4.09v… almost immediately the charger switched from 1a to 0.9a and has been slowly trickling down the current while charging at 4.2v… charger is at 0.2a/4.2v now and the cell is reading 4.16/4.17v on my DMM…
sounds like its working as it should
the charge finished… battery came off the charger at 4.17 volts
i put it back on to discharge at 1.0a… voltage dropped to 3.95v and is holding there now… reading 4.04 at the battery with the DMM
will update this thread with total mah after the discharge is done
Yeah, either the calibration is off or you’re getting a voltage drop somewhere between the cell and the microcontroller. It should be pretty easy to find.
Your solder joints on the magnets do not sound great if they easily broke free. Perhaps that’s the source of your problem?
the magnets do not come off - i think the solder joints there are fine - right now the cell is meas. 3.76v and the charger is reading 3.62… so there is still some voltage drop somewhere
edit: it appears the magnet are eating 0.05v themselves… if i connect my dmm to the battery terminals i read 3.65… back side of both magnets i read 3.60… checked it twice to confirm…
im probably getting nit picky here… just part of the learning process i guess…. exact science is not an exact science
results:
not bad i guess… my ddm read 3.11v before the cell quickly bounced back to 3.35v 20 sec later
so obviously there is a little bit of a voltage drop somewhere in the cables/magnets… no big deal… the cell appears to charge ok and it seems that im getting about a .1-.15v drop somewhere during discharge…
i might try some different cables and also cleaning the contacts
the weirdness i was getting was because of old tired cells. they have been recycled.
thanks for the help everyone
As I said earlier, DURING discharging, taking a reading at the magnets will always be slightly higher than putting the DMM’s probe reading ON the cell’s +/- ends because it takes a while for the cell to chemically react to the voltage reduction being done by the charger.
As to the cell bouncing back to a higher voltage compared to the voltage to which the charger discharged it down to, a good cell will almost instantly bounce back to a higher voltage, eventually going back to its natural voltage, 3.6/3.7V (being a Li-Ion), although it was discharged down to, lets say, 2.7V.
Are you sure about that? When discharging, the only voltage source should be the cell. How could the magnets be higher than the cell itself?
I have tried it countless times. In my case, I use an iCharger 106 with alligator clip outputs. I use magnets to stick to the alligators. I always get different readings, even with my niMH Imedion D 9500mAh cells housed in D-cell housings. Put the DMM’s probe on the alligators or magnets, then compare it to the reading on the cell itself.
Again, during discharging, especially at high rates, the voltage at the clips/magnet is always higher than at the cell itself since it takes time for the cell to chemically react from the voltage decrease coming from the charger’s alligator connectors.
In other words, the cell’s reaction to the voltage decrease coming from the charger is not instantaneous.
I have also tried this on my Pila ( or any charger for that matter). Try to get a reading on your DMM while charging, one on the cell and another on the charger’s terminal…and there will be voltage differences.
i have the exact same problem in my accucl8
it don’t full charge my lipos, also accuracy is so bad
i had to foal the calibration and put it under –20 down clicks to force the charger to full charge my lipos
the most strange problem i’v seen that i can’t reach the same avometer voltage readings on my charger in the calibration wizard
as my avo gives 12.50 and charger shows in the max +20 up clicks 12.45 !!!
am really disappointed as i didn’t face the same issue with my old accucel-6