IB4200 voltage drop

[deestingray]

I have some 4 packs of IB4200's that haven't been used at all in about 12 months. Being that they are for the new boat, I gave them a couple of cycles and all 4 packs took over 4500Mah at a nice slow .5A charge.
My problem is that after about 3 laps the voltage drops off really fast, enough to hit the low voltage cutoff on the esc however I have only lost around 900mah. I would have thought that if I was drawing that much current to put them under that much load, A: the cells would have been scorching and B: my 70A esc would have cooked by now.

Has anybody experienced this and are the cells recoverable?

[ED66677]

is your esc configured for Nimh cuttoff and not for Lipo's as factory default value? what ESc is this?

[deestingray]

It is a dynam 70A esc, I cannot remember if I set the nimh limit instead of lipo, thanks for the tip I will check that. Will the low lipo cutoff power the esc down gradually or is it just a switch off? It loses tremendous amounts of power first though but it still spins, it is very noticable and then drops off very fast indeed. A 3 second pause allows the cells to recover again and it will take off but only breifly before losing power again.

[GregS]

If the batteries were not charged in 12 months that likely could be the problem. When not in use it is a good idea to charge NiMH once a month, otherwise they can discharge to the point where they are not recoverable.

Greg

[ED66677]

depends some ESC will simply stop others will reduce power
I have a cheap Mystery that basicaly reduce the power to idle, so the motor spins at the minimum the ESC can do and of course if you wait a bit, batterie voltage goes up and the power is back again

[ED66677]

if battery was dead due to long storage, it would not have taken 4500!!!

[Doug Smock]

If the batteries were not charged in 12 months that likely could be the problem. When not in use it is a good idea to charge NiMH once a month, otherwise they can discharge to the point where they are not recoverable.

Greg

It doesn't take 12 months at less than .9v to reduce the capacity. I have had brand new 4200 SHVs and WCs show up at the door at less than .9 volts and could not get them to come up. The best that they would do on average was 3800mah. These cells have different self discharge rates so it is a good idea to balance charge them at .5amps once amonth while in storage. I balance charge mine every two weeks.
You really can't go by the 4500 they took during the charge, there is no telling how much of that went to heat.

Doug

[JimClark]

Start with the LVC setting take it off on NIMH batteries it is not needed

Jim

[Fluid]

if battery was dead due to long storage, it would not have taken 4500!!!

This is a common misconception. At a 0.5 amp charge rate a good pack of IB4200a should take over 5500 mAh of charge, mine take close to 6000 mAh at 0.4 amps. The fact that yours did not is an indication that they are probably not in top shape. You may have just a few cells that are bad - sadly this became rather common with IB4200 cells sold by early/mid-2007. Did you check the temperature of each cell in the packs? If one or two were hotter than the rest, there is your answer.


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[Fluid]

Start with the LVC setting take it off on NIMH batteries it is not needed

I'd argue that Jim. Drop the IB4200 cells below 0.9 volts each by running until the pack starts to visibly dump before you bring the boat in and you will probably damage at least some of the cells in the pack - particularly if that is the normal way you treat the packs.


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[ED66677]

Fluid,
for how long have you been using a 4200's pack that take over 5500 or 6000?
I've never heard this before so I'm curious because any battery brand I've used would take (@1/10C) around 10% more than the nominal but not as much as you discribe!
Are IB's that so good?

[JimClark]

If you slow charge them at .50 amp they will routinely take that much.

Jim

[Darin Jordan]

Fluid,
for how long have you been using a 4200's pack that take over 5500 or 6000?
I've never heard this before so I'm curious because any battery brand I've used would take (@1/10C) around 10% more than the nominal but not as much as you discribe!
Are IB's that so good?

I don't think that just because they take over their rated capacity in charge, it means they have that capacity available for use... A lot of this is lost in heat and inefficiencies in the charger...

I've had IB4200 WCs take over 5000mah @0.5amps as Jay has described... they still only take 4300-4400 when charged from 0.9V to peak under a normal 4.2amp charge... and I've never seen the DISCHARGE that much back out...

[deestingray]

Did you check the temperature of each cell in the packs? If one or two were hotter than the rest, there is your answer.


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I didn't get very much of a chance to get them hot, they don't even heat up during a run unless I peak them with a 5A charge and then run straight away. I have 4 sets of 4cell packs and run 2 at a time to give me 8 cells per run, the same thing happens on both sets of packs. Might just have to check each cell individually and take it from there, or just cut my losses and get new ones. Thankyou to those who have replied, there is a lot of useful info amonst you all for sure, I have a much better understanding now, I will however advise if these things come up ok, have to have some optimisim!!!!

[Fluid]

for how long have you been using a 4200's pack that take over 5500 or 6000?...Are IB's that so good?

I've been IB4200s for over a year and a half, all SHV and WC cells. It is not at all uncommon for an unballanced pack to take a lot of mAh from the charger. Some cells in the pack will come up to full voltage early, but due to the low charge rate the charger does not shut off. These cells turn all excess energy into heat, but at 0.5 amps this doesn't get them very hot. More and more cells come up to full voltage until the pack voltage as a whole drops and the charger shuts off. This is how the pack is balanced through charging. The cells cannot store much more than their rating, the rest of the charger output is turned into heat.

IB cells are/were great because they have very low internal resistance and thus high output voltage. They were a step change over the old GP3300 cells.



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