New cell caring / equalising

[super__dan]

All,

I've just got my new SMC cells, they are great, having run a cycle on my pulsar the average voltage is way higher than anything else I've had before inc previous 4200's.

Anyway my point though is this, though the cells are amazingly well matched, once freshly built I noticed that the cells are not perfectly balanced. So I followed SMC's instructions, partially charged and then equalised to 0.9V/cell, there was quite a lot of variation in their time to discharge I guess because as we know 4200's seem to self discharge more than any previous cell and at various rates. As said above I then ran cycle and the results were brilliant, can't wait till Kidderminster

So what I'm saying is that even with brand new cells equalising is in my opinion essential, maybe more so than ever before. I use a Smart tray whcih holds the cells at 0.9V so when you take them off they are all perfectly balanced, ideal just before going on charge.

Dan

[DCM]

Always equalise before charging, pointless after use though.

Dan, maybe you should invest in a Tekin Battery Nurse, to hold them new cells at a safe voltage, lol.

[sosidge]

Originally Posted by DCM

Dan, maybe you should invest in a Tekin Battery Nurse, to hold them new cells at a safe voltage, lol.

That isn't released though is it?

[DCM]

just been released and sold out within a day, they are making another batch

[tc2k]

I bought a load of GP3300 cells in November, they had most likely been on a shelf for 2 or 3 years. First charge they false peaked within around 500mah and then didnt peak despite over 4000mah so I took them off. After running them they all took around 2700mah but had amazing punch. After buying a LRP conditioning tray, all the packs now take around 3200-3300mah with the same ammount of punch, my verdict, EQUALISE.

[bigred5765]

the Novak smart tray now holds voltage at what ever u set it at, to get it to do this you need to hold down the small button while turning it on, only the SE version does this.

[DCM]

the battery nurse from tekin is a storage box which holds individual packs of cells at a set voltage.

[losixxx]

i just got rid of my smart tray SE and got the new trinity dyna pro digital discharger, excellent bit of kit, discharge's at 30amps and equalize's the cells plus give's accurate reading for each cells performance.

[KyoshoK]

what does the battery nurse do? its like a trickle charger?

[super__dan]

THe tekin keeps the battery voltage up to a set level I guess essentially by a varying/monitored trickle charge. I guess usefull if you're storing cells but if you use them every 1 to 2 weeks it seems a waste of time to me as long as you leave charge in your cells, then equalise just befre you charge. It's not cheap either is it

[DCM]

well, depends on how you look at it. IB cells can drop their voltage pretty quick if not watched, so even storing them for a couple of weeks can cause problems, especialy on the WC batch.

[Slimboyfat]

hi guys, just to change the subject a wee bit although on the same lines, i guess.....

i haven't used my brand new 3700 sp2's for about 5 months now. whats the best plan of action to get them up to speed again? There was end of race charge left in them from the only meeting i've done with them.

[DCM]

I would put them on a low charge current with maybe a slightly higher delta peak setting to get a charge in them, then discharge, allow to cool, tray and charge at the correct setting.

[super__dan]

The old 3700's are more robust but as I'm going on about here I think equalising is essential after a charge in them

[ApexSpeed]

I've gotta say, the 4200s that I have are enormously high maintenance, and I can't stand it. I bought 8 very good packs for 2 different oval cars a few months ago, and because I don't race very often, I am CONSTANTLY tending to these things. 300 seconds here, 300 seconds there, discharge, equalize, re-charge, store... blah, blah, blah. It reminds me of the days of those nasty Sanyo SCE 1700s that were super expensive and had a shorter lifespan than a garden moth.

I hate these batteries. I don't care how much voltage they pump out or how good the internal resistance is. The GP3700 is the best sub-C battery that has been out in the last 20 years, and we all tossed them aside for more voltage and runtime like they were yesterday's garbage (speaking of most forms of racing outside of off road).

If it weren't for my BJ4WE needing saddle packs, I'd have all Orion LiPos in all of my cars already.

[neiloliver]

Cells optimised for high voltage and capacity have reduced cycle life and higher rates of self discharge. The IB4200 does have a high rate of self discharge and equilsation is a good idea. The reason is this: if you have one cell at 0% residual capacity, two cells at 10% and three cells at 15% in series, and you put them on charge, the three cells with the highest residual capacity will reach top of charge first (the other three guys are still playing catch-up). If you have you -dV set at 5mV per cell these three fully charged cells will have to go into further into overcharge until they reach 10mV for the charge to terminate. These three cells will be hotter than the other three which never reached full charge so there life will be reduced. They will also be more likely to vent electrolyte due to internal pressure increase. When you use the battery, the cell that was furthest behind will discharge first and be driven to a low voltage (even a reverse voltage is possible in very large cell strings such as large powertool batteries) and is more likely to vent due to reversal.

This explanation is a bit simplistic because the cells do have a degree of internal balancing in overcharge due to internal recombination reactions, but high capacity cells dont have the luxuary of good recomination systems due to the designers having to push capacity.. so in effect they are more fragile than commerical NiMH cells made by the likes of Sanyo for powertool applications.

So the best things to do are:

(1) Equalise
(2) Dont charge at high rates (4A, no more)
(3) Store cells with 2000mAh in them
(4) Use low -dV thresholds (0mv -3mV/cell)
(5) Floss
(6) Charge cells which are at room temperature
(7) Accept that lights that burn twice as bright burn half as long


N

[Slimboyfat]

ok what i have just done with my 3700's is discharge them down to 6v pack. i have let them sit for 10mins then put back 1000mah @ 5.5amps into them for storage.

I plan to on race day - discharge, equalise, fully charge @ 5.5amps.

any advise for/against/agree with this?

[bigred5765]

run them and put them away with what ever is left in them,then do no more,
before you use them again discharge and balance, when cool charge 5.5 or 6 amps and don't re peak, use them put them away till next time no big secrets or issues thats fine,

[super__dan]

Originally Posted by bigred5765

run them and put them away with what ever is left in them,then do no more,
before you use them again discharge and balance, when cool charge 5.5 or 6 amps and don't re peak, use them put them away till next time no big secrets or issues thats fine,

I agree with this, though time allowing I'm going to stick with just 5A, this then takes the charge time to a good hour so for the shorter meetings will have 2 chargers on the bench. I was lucky enough to recently pick up a Novak Millenium Pro for about £30 on ebay, freaking bargain

[DCM]

I must admit, IB42's, I have found they work better and more consistant at a lower charge current