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Old 06-04-2019, 12:40 PM   #1 (permalink)
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Default When to deep discharge IMA for conditioning?

When to do a deep discharge of the IMA battery for conditioning? I have the time to do it now, and the weather seems to be cooperating. Are there reasons to NOT discharge a 2.5 year old IMA?

And, how far to discharge it???
Discharging my old, failing IMA, I took it down to 0.17A / 91.78V, driving a single 25W bulb. That's a true 25W, not an "equivalent brightness". I still have two of those bulbs available.

This Bumblebee battery is now 2.5 years old, plus a bit. I've probably driven it about 80K miles. Seems to be performing well. I've done a conditioning charge of this battery twice yearly ever since I installed it. I've never done a discharge on this battery, but the harness is in place and I have a simple light-bulb discharger with good gauges.

I installed this Bumblebee Oct. 2, 2016. It was a warranty replacement, and has their (newer) circuitry that runs the battery cooling fan on low unless the computer demands high speed. Additionally, I've upgraded the battery cooling fan, and also added switching so that fan normally runs on high all the time. I haven't gone as far as building Mike Dabrowski's duct from the a/c output to the fan's intake. Mostly I limit battery use severely by using the clutch switch.

Last edited by brucepick; 06-04-2019 at 12:47 PM.
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Old 06-04-2019, 06:03 PM   #2 (permalink)
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Maybe you should call or email Eli at Bumbles and ask him, see what he has to say about it?

I experimented with a single aftermarket stick, including some deep discharges, and ultimately 2 of the 6 cells failed... Not really much to go on, but this and other things make me think the aftermarket cell chemistry is different at some fundamental level - maybe the absence of some particular, 'second order' active material? This stick has been sitting for ages now and somewhere along the line some cells dropped to zero volts - that's not something I've ever seen with OEM cells. Basically, my 'finger in the wind' tells me that aftermarket cells probably don't/won't respond to deep discharge, particularly super and ultra deep, like OEM cells do...

If the voltage taps are closely balanced, I might consider a mild discharge at low current - such as your 25W bulb - down to maybe... 132 volts (or even a lower wattage bulb if you can find one/rig it up). Maybe 120 volts if I were watching it closely... OEM pack management concentrates usage in the upper charge state area, and I think that's one of the main causes of pack problems sooner rather than later. So, in kind of a conceptual sense, it seems like a mild discharge in charge state area that's rarely if ever used should do some good, you know, clear some ionic pathways, free up some active material that's heretofore gone unused, sprinkle some fairy dust all over the cell...

Oh, one more thing: Overall, I think my strongest advice would be to not do anything if you don't have a problem. If you don't see unusual voltage sag, if the pack can put out 90 amps for 4 seconds, if it can hold 20-30 amps at over 140 volts, if it can hold 45 amps above 132 volts for a long time, if voltage taps are balanced, etc. -- I wouldn't do anything.

Last edited by eq1; 06-04-2019 at 06:07 PM.
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