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Discussion Starter #1
All,
I lucked into a complete Insight Gen 1 IMA battery. All I can say about it is that it has been sitting, almost certainly for 2 or 3 years. Voltage was about 3.25 volts before any charging. I have a 250 mA trickle "grid charger", and have begun charging. Steep slope in the first 20 minutes, rising to a terminal voltage, with charger attached, of 115 V. In the next 16 minutes it rose to 164 V, and looks like the voltage rise will be pretty gradual from here on. Does this reconcile with other's experience of charging a completely discharged battery? Am I wasting my time on this battery? I have a pretty decent 2006 Insight, 100K or so miles, with a completely shot battery. It would be nice to be able to get it back on the road again. Here in MA, it won't pass inspection with IMA/check engine lights on - until next year! Thanks.
 

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You don't need a new battery to get the IMA light and CEL to turn off. There is a guide on here for creating an Arduino that plugs into some of the IMA connectors. I could probably whip one up in around 45 minutes. I actually have the complete rear contents of one of my Insights removed, and it passes Vermont's similarly strict inspection.



No CEL!

That said, your experience sounds about right. The pack should top at around 170-180v depending on the outside temperature. I'd keep charging a couple of hours after the pack peaks - you should then see the voltage start to drop a hair, indicating the cells are full and starting to dissipate the overcharge as heat.
 

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Discussion Starter #3
I have read about the Arduino hack. Very cool. But since I have this pack, I was hoping for the best. It's brutally hot here in western MA, I have a copious fan blowing on the pack - a lot of hot air ;-). I started charging right around noon, and if it hasn't peaked by midnight, I'll have to shut it off. Many thanks.
 

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A full charge from zero at 250mA will take 26 hours as it’s a 6.5Ah battery. Take into account losses etc, it’ll be closer to 28-30 hours.

NiMh batteries are funny things. If the temperature rises significantly during your charge (ie as it goes up during a hot day where you are) you’ll probably see the voltage going down even though it’s still charging. That’s just the internal resistance in the cells changing with temperature and the voltage on your constant current charger changing to compensate. It’ll be way kinder to the battery to do this in the house where it’s cooler, if you can.

I’d recommend a cycle of bulb discharge to 140v, recharge, discharge to 120v, recharge, discharge to 90v, recharge. It will take some time, but it’ll exercise the dormant material in the cells and probably reactivate some capacity so it’ll be worth it in the longer term.
 

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Discussion Starter #5
Hi J - No air conditioning here - it is what it is. I guess I could leave it charging overnight if I didn't think I'd burn down my shop ! Been charging for 1 1/2 hrs now and it's been 165.5 V for the last hour.

That's quite a regimen of discharge/charge cycles you propose. Have others had this same experience? Not questioning yours, it just seems there are lots of different experiences. If I do this bulb discharge, how fast can I go, ie two 100 W bulbs in series (USA 120 volt system). I wish there was an easy way to automatically stop the discharge at the desired voltage, without coding a micro with a/d to drive a relay etc. Thanks.
 

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It’ll sit around that voltage for at least another 15 hours then start creeping up near the end.

Consensus on here is slow is better at this point for charging and discharging, so yes, two 100W bulbs in series is what you need. Cycling the batteries up to the top a couple of times tends to reactivate material in the cells. Taking them back down to 0.8-0.7v reverses memory effect that builds up through not discharging far enough. Doing it in gentle steps like that fixes the weakest cells first and stops them sitting reversed for too long. The gentler you can do it now the better later, so it’s worth taking your time now to give it its best chance.
 

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I don't think you need to cycle the pack, definitely don't need to deeply discharge again, just charge it and use it. Your pack has sat for 2-3 years and deeply discharged - that's as extreme as you can go for getting a 'palliative' deep discharge, so that takes care of that aspect. Personally I've never seen benefits from low current cycling, particularly with cells that have already been deeply discharged, so I see no need for that.

-peak voltage for your charge will be (should be) higher than what it'd be for a not-deeply self-discharged pack. I'd expect to see higher than 175V, I wouldn't consider it done unless I saw a peak above 175V. I think I'd expect around 178V.

-a pack that deeply self discharged will take longer than normal. With a 250mA charge current, I would expect it take no less than 30 hours for a full charge (+7500mAh)... I wouldn't go longer than 34.4 hours (+8600mAh).
 

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Discussion Starter #8
Hi eq1 - thanks for your recommendation. I'm at just over 4 1/2 hrs of charging, voltage at 166. My shop is at 87 (deg)! I like your answer better, 'cause it's less work. I'm using two supplies designed for constant current to illuminate LED strings, wired in series, 90 volt each. They do run warm. The price was right. Regards.
 

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^ I think I'd still expect to see 175V or above at peak, even at around...well, pretty warm temps. I suggest taking a look at voltage at about 28 hours total charge, note ambient temp, both I guess simply as a reference. Because I think you should just end the charge between 30 and 34.4 hours, regardless of what voltage you measure. I mean, if it's below 172V something's off and I'd continue, that is, if you see a lower voltage at the 28 hour mark. If it were around 175V+ at 28 hours and then dropped to 172V I'd end the charge...

Basically, I'd be expecting to see around 174V+ at 28 hours if ambient temp were around 75-90 degrees F (and the pack shouldn't be much warmer than that either). After that, voltage should continue to rise I'm thinking up to about 178V, but temp will rise too - so it ends up being a 'competition' between voltage increase due to increasing charge, on the one hand, versus voltage decrease due to increasing temp on the other. But the real temp increase won't happen until the pack's nearly full, there's just a small window of opportunity to really catch that full juncture, because after that the pack will just get hotter and voltage will fall. Then it becomes more difficult to determine just how charged the pack is.

It's much more cut and dried with your situation because you had a completely discharged pack/cells; typical packs are imbalanced and the imbalance makes it hard to see the true end of charge. It's not like that in your situation, the end is pretty stark, clear, you just have to be watching at the right time - that window between about 28 hours and 34 hours.
 

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Discussion Starter #10
First, everyone, thanks for your comments and suggestions. I took a few minutes to plot my manually taken measurements. I wish now I had recorded room temperature. Also, the slight blip in the early data between the 4th and 5th data point is due to my stopping to replace the DMM measuring current - it began to show impossible values. This took a few minutes to figure out. Plot attached. The next few hours get interesting. I will update later.
86376
 

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Discussion Starter #11
As per EQ1, here at 4:00 pm, it's been 28 hrs, and the terminal voltage, still under charge, is at 172.7 volts. Not to far from the 174 V you expected. Voltage has been increasing hour by hour, not headed back down yet. Shop temp first thing this morning was 80 deg, currently 87 deg.
 

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Discussion Starter #13
Getting close to 31 Hrs. Voltage is 174.1, still climbing. Temp down to 83, 2 1/2 hrs ago it was 87.
 

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(we're cross-posting)

^ What Ecky says. If you're gonna watch it pretty closely then just watch for peak voltage, i.e. watch for when voltage levels-out. Since it's been increasing rapidly I wouldn't bother to wait for voltage to fall - just, if it stops increasing over say a half-hour interval, consider it done.

Cell temps will start increasing and will start to depress voltage. As I recall the adjustment is something like -0.32 volt (for the pack) per degree celsius (1.8 F) increase in pack temp... Sounds like ambient temp is not going to change too drastically in the next few hours, so I would think that reaching full will dominate the change in temp. I don't think you'll see much temp increase though, in the pack, maybe 5 degrees F? So if the expected peak were say 178V without a temp adjustment, you might adjust that down by 5F/1.8F X 0.32V= -0.89V... Doesn't really rise above the 'noise'... Just watch for voltage to level-out over about a 1/2 hour interval.

Oh, forgot to say that the temp change cuts both ways: decreasing temp will exaggerate how much the voltage increase reflects charge increase, so consider the temp adjustment formula in light of decreasing temp as well... If ambient temp were to drop say 10 degrees F over the next couple hours (if you have a fan on the pack), then that would make voltage artificially increase, i.e. you'd get a V increase that doesn't actually reflect more charge...
 

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Discussion Starter #16
Now that the pack is very close to fully charged, is the car's charging system unable to finish the charging? Is the battery management system, how do I say this politely, "lame"?
 

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The car doesn't charge the pack to full, not "lame" per se, just a design/engineering choice. Just finish the charge how you're doing it. Plus, I want to see what voltage/s you actually hit... My guesstimates are looking pretty close, though it doesn't look like you're gonna hit 178V by 34.4 hours... You can quit any time at this point, really. You don't have to go to chock-full. But for the sake of my curiosity you'd let it go...
 

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You will probably never get 100% charge from the cars system. In the range of 70-80% most of the time. IMHO
 

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Discussion Starter #19
Time to shut down, just a fraction more than 34 hrs. Terminated with battery voltage at 175.5 V
86401
Plot below:
 

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After it sets for 12 hours, you will probably end up with around 165V
 
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