[jeffffej]

Hey everyone, thanks in advance.

(real answer to my questions = get a new battery)

OK my question is this. My '03 has a 13-year old NiMH Honda battery. It used to hold for about 3 months before it popped an IMA light and required grid charging. Nowadays the light comes on every 2 weeks. I deep discharged recently but the light still comes on every 2 weeks. While I'm saving up for a new battery soon, please help with these questions:

1 How long can I drive it with the IMA light on before serious problems occur?
2 Since it's throwing the IMA light every 2 weeks is there any point in grid charging it anymore or should I just reset the light using the fuse trick and be happy till it retriggers?

 

[olrowdy01]

Hey everyone, thanks in advance.

(real answer to my questions = get a new battery)

OK my question is this. My '03 has a 13-year old NiMH Honda battery. It used to hold for about 3 months before it popped an IMA light and required grid charging. Nowadays the light comes on every 2 weeks. I deep discharged recently but the light still comes on every 2 weeks. While I'm saving up for a new battery soon, please help with these questions:

1 How long can I drive it with the IMA light on before serious problems occur?
2 Since it's throwing the IMA light every 2 weeks is there any point in grid charging it anymore or should I just reset the light using the fuse trick and be happy till it retriggers?

At what voltage did you stop the discharge?

 

[eq1]

1 How long can I drive it with the IMA light on before serious problems occur?

Probably not very long. If you're getting the IMA light in 2 weeks (I'm assuming a P1449-78, which seems likely) then you've likely got at least 1 pretty fast self discharge cell, and once that goes really empty the DCDC will disable... It actually kind of depends on how much charge you're getting into 'that cell', during drives where the IMA light isn't on. But if it's on all the time, IMA disabled, then not long. You'd need to disable the pack (turn switch off, pull BCM connectors) to avoid 12V charging issues...

2 Since it's throwing the IMA light every 2 weeks is there any point in grid charging it anymore or should I just reset the light using the fuse trick and be happy till it retriggers?

I don't think there's any point. What you need to do is bottom balance the cells and then use the pack almost exclusively at the bottom end, driving with assist until near empty after each drive. That way the fast self discharge cell/s won't cause imbalance problems. I'd recommend trying voltage tap discharges to get that bottom balance - short 5 taps at a time, every other tap, at the BCM tap connector, until tap voltage gets really low (like as low as possible, definitely below 6V). Let the voltage rebound for at least 12 hours after the last set of 5 taps, grid charge for at least 650mAh input but no more than about 3500mAh, then just drive. Use assist to empty the pack as much as possible before you get home, driving until neg recal is fine.

 

[jeffffej]

At what voltage did you stop the discharge?

Thanks for the replies guys. I stopped the discharge at whatever the Prolong charger instructions specified, I don't remember but I can look it up if it's helpful. I did exactly what it said to do, I was very careful.

 

[Bull Dog]

1 How long can I drive it with the IMA light on before serious problems occur?

At the shop, people ask this crazy question all the time.

It will last exactly as long as it will until it fails completely. No more, no less.

 

[eq1]

Just thought of something you might want to try, in lieu of anything that takes real work or money. When you do your reset thing and get the IMA to work for your two weeks, try charging as high as possible during your drives, like preferably until it won't charge no more and disables regen. But make sure before you get home you drain the pack completely (use assist until neg recal; if you can, leave the car in auto stop until neg recal or 12V battery warning light comes on). Do this several days in a row and see if it helps. And if it does, do it some more.

The idea is that you should get some balancing charge at the high end - maybe your grid charging simply can't get much into the 'low' cell/s - and then, if you drain the pack you won't lose any balance gained. Each day you should be able to push the charge state higher, which will probably have some reconditioning impact on top of the extra charge, and if you drain the pack each day (or as much as possible), you'll lose less each day as well.

 

[jeffffej]

Just thought of something you might want to try, in lieu of anything that takes real work or money. When you do your reset thing and get the IMA to work for your two weeks, try charging as high as possible during your drives, like preferably until it won't charge no more and disables regen. But make sure before you get home you drain the pack completely (use assist until neg recal; if you can, leave the car in auto stop until neg recal or 12V battery warning light comes on). Do this several days in a row and see if it helps. And if it does, do it some more.

The idea is that you should get some balancing charge at the high end - maybe your grid charging simply can't get much into the 'low' cell/s - and then, if you drain the pack you won't lose any balance gained. Each day you should be able to push the charge state higher, which will probably have some reconditioning impact on top of the extra charge, and if you drain the pack each day (or as much as possible), you'll lose less each day as well.

This is really thoughtful and helpful, I appreciate it! I’ll give it a try, though getting it to regen to the max is weird because when it does it immediately depletes to 3 bars and starts regenerating again.

I’m working on getting my lithium setup in the meantime….that was always the end goal, I’m just seeing how long I can stretch this OEM pack…

 

[Natalya]

At the shop, people ask this crazy question all the time.

It will last exactly as long as it will until it fails completely. No more, no less.

Failure mode being when it decides to stop charging the 12V battery, I'm assuming? Sometimes it takes a couple weeks, other times it takes a couple days -- really depends on how bad the battery is. I think it's the slow drop in pack voltage that eventually triggers the DC/DC shut-down. I don't know the voltage threshold at which that occurs.

 

[eq1]

^ I don't think it's total pack voltage, but either tap voltage, or the steepness of the slope of tap voltage which indicates an empty cell... I guess it could be total pack voltage, too, but one or both of these other things have to come into play first. I see DCDC shut down all the time when I run my pack empty, taking tap voltage measurements, etc. It always shuts down when one tap reaches about 14V, which in my case, though, is always when a single cell is going empty. I've seen it happen a little above 14V and a little below, so it doesn't seem like it's exactly 14V (edit: but that could be some measurement error or the like, either on my part or on the BCM's part, like a time lag, etc.)... DCDC shuts down like this even when total pack voltage is, not exactly high, but not low (maybe as high as ~152V).

 

[jeffffej]

You have all been very helpful and I appreciate it. So thankful for this community! I find myself talking to members pretty much every week outside of the forum. In any case I'm driving my Insight like I mean it with the nearly dead battery and making plans to upgrade in the next few weeks when the stars align. The time has come.