Honda Insight Forum banner

21 - 27 of 27 Posts

·
Super Moderator
Joined
·
8,231 Posts
Long Discharged Sticks

Well given the thread title, I guess this is a good place for another small bit of confusion. Someone mentioned, not sure - couldn't re-find the words, that sticks become unbalanced badly as the self discharge. Said person also seemed to prefer a low current charge to "wake" up the weaker cells. I never gave this a great deal of thought until in read that comment this evening.

Just for laughs, It occurred to me that I could simply check the cell voltages BEFORE I started my usual 3 reconditioning cycles (prior to high current testing). Welllll........on the first stick I tried I see that it is badly unbalanced, in fact two cells are so low in voltage as to be considered dead from a performance view, not a surprise since it has been sitting for a long time.

Voltages were 1.27, 1.19, .54, 1.16, .55 and 1.27 volts.

Started me wondering about best way to initially charge such a stick. I'm sure that those cells will register 7V + as soon as I hit the charge button, but is there a better plan???

I usually charge at 2A, but now I'm wondering if a lower current would do a better recovery job.
 

·
Registered
Joined
·
6,843 Posts
As I mentioned in the post above yours - cell discharge rig, or just place a small resistor on each cell, clamp them there... i.e. discharge the cells individually then charge... Of course, you don't need to discharge the already-self discharged cells...
 

·
Super Moderator
Joined
·
8,231 Posts
As I mentioned in the post above yours - cell discharge rig, or just place a small resistor on each cell, clamp them there... i.e. discharge the cells individually then charge... Of course, you don't need to discharge the already-self discharged cells...
Woops, sorry got bogged down in the quicksand and lost it right there in front of my eyes:(

You also mention that for long stored sticks you would wake them up with gentle cycling. Two questions come quickly to mind: a. what charge/discharge current are you indicating, and b. got any data or just a kinda experiential based feel that one needs to be gentle?

I really don't mean to press too hard, I know how hard it is pin down the process.
 

·
Registered
Joined
·
6,843 Posts
If you're asking about what I say above about 'gentle cycling to get the juices flowing', that's mainly based on experience. The most important aspect is to be gentle at the top, like not doing a full delta V-based charge on the first charge. It's super easy to vent cells that have sat, even before cell temps get very warm at all...

Just about the worse thing one could do is pull a stick off the shelf and set the cycling device to 3 automatic cycles with a 0.9V/cell discharge cutoff and a delta V of 4mV (the 'old-school, boilerplate' recommendations). That's a recipe for failure: You start with a very likely imbalanced stick - like the one you mentioned above, with uneven cell voltages - immediately hit it with say 6.5A current, and then the charge doesn't stop until some ill-defined cutoff/s that can be the result of various not-so-good conditions, like a 24mV voltage drop caused by one cell overheating, maybe all cells overheating a bit, etc. I mean, usually we only have one temp probe anyway - it's just a roll of the die if that one cell happens to be the hottest and triggers the temp cutoff, if you have one set...

Much better to first discharge cells individually (resistors on cells), do something like a <1.3A charge for around 500-1000mAh, increase current to say 6.5A until a total of around 6000mAh has passed (or perhaps voltage reaches about 8.7V), then drop current to around 500-600mA and let it go until about 7600mAh total has been input. Sounds terrible, I know. My Reaktor though basically automates most of this. It does a super-low current pulse charge until voltage reaches about 1.3V/cell, then it will ramp up to the user set current. Then it will go until a user defined voltage threshold is reached and taper current...

Alternatively, don't charge to full on the first charge, maybe take it up to no more than 1.46V per cell at 6.5A. Maybe use a current lower than 6.5A for the charge and not go totally full. Etc... Use a moderate voltage threshold for discharge, too. I usually do the discharge until first cell pair reaches 2V, so roughly first cell at 1V and the discharge stops. If you don't have cell-level capability, keep the threshold a bit higher, like around 1.1V per cell so 6.6V total. 0.9V per cell will likely drive one cell too low, with the possibility for high current reversal, too. Also, note that my voltage cutoffs are based on measurements at the cells, with little lead resistance; if your voltage values are on the main leads, then you have to adjust your cutoffs to account for lead resistance. Typically it won't make too much difference, though (unless it's a Superbrain)...

In a nut shell, on the first cycle of sticks that have sat for a while, it's best to keep away from the 'tails', the extreme top and bottom...

After this stuff you can do whatever kind of cycles you want, more or less...

I guess most of this applies to any sticks, really, not just ones that have sat, mainly because even sticks recently used in the car tend to get so imbalanced (that's likely the reason the pack is failing in the first place). But for ones that have sat, the risk of venting, etc. is worse...
 

·
Super Moderator
Joined
·
8,231 Posts
Thank you eq1 for your thorough response. I read it carefully and intend to read it again.

Unfortunately, I'm still on the dark side with the Rodney Dangerfield chargers, but I have modified the lead setups considerably, eliminating the alligator clips and the plastic side plugs. Also, as discussed some time ago, I do not rely on the meters but do my measurements at both the cell level and the stick level using other meters. Since the SB meters aren't accurate, I compensate with the settings to get the starts and stops I want. I also set the battery size to control charge amount, rather than relying on delta V. Anyway, I think I've gotten around most of the issues, but I do need to watch the cell meters a bit better.

Already, I do do an initial low current charge of 1000-1500mAh. Kinda seems right to me too. I am perhaps a bit heavy handed with the successive cycles. Really tough to know about possible venting since I try not to disturb the heat shrink and have not yet watched the sticks late in the charge cycle. Thanks for the warning.

Again, thanks for your effort in the detailed write-up. I need to read it another time or two.
 

·
Banned
Joined
·
1,541 Posts
Hello All,
I wanted to try and get some information on reconditioning the IMA battery at the stick level.
I continue to hear several different theories, experiences, and other ideas as to the effectiveness of stick level reconditioning.

I know that there is information already around here, but this is the problem. I continue to find conflicting information,
not only from separate users, but even the same insight central posters over the years, where they go back and forth on their
stances. I understand that the answers are difficult to pin down, and each is a case by case basis, and there isn't necessarily a definitive answer on this whole deal.

I have been looking through the forum on this topic for a few months at least, trying to determine what to do. I already have a grid charger, and while this works well, I have been having self-discharge issues with my battery, where if left for a couple of days, it drops to about 75% capacity. While grid charging seems to be working alright, it just isn't enough, and due to my living arrangements grid charging is not always an option, or able to be done due to time constraints.

I was unable to obtain the famed superbrain charger, however, I was able to get a 300w balancing charger with good reviews from amazon for 100 bucks.

Based on what I have read here, the balancing charger may help fix some sticks that are only slightly weak, but more importantly identify any truly bad sticks/cells. These sticks will need to be replaced, and then the pack should be discharged and grid charged to complete the process. Many say that this whole process is a fools errand and does not show considerable improvement over a simple discharge and grid charge.

I would appreciate any help.

highmiles
As always with a discussion forum, you need to make judgements about the veracity of the data being given, and the credibility of those giving it.

I don't have an iron in the fire (my car has no IMA or battery pack) but if you watch the forum long enough, you will see people who ride battery hobby horses like they're in an Olympic event, and others who make up their own unique theories - free of any constraints like peer referencing or even scientific common sense.

It's not of much help to you, but I suggest that you PM those who have a history of achieving battery outcomes in a commercial sense, and who (via PM) may be prepared to share some of their actual, demonstrated wisdom with you.

And a contentious final comment: the people who are really achieving seldom have time to expound long-winded battery theories here: they're too busy doing it for real!
 

·
Registered
Joined
·
33 Posts
This is a 3 year old thread but thought I might tag my advice to the new owner of my 2001 CVT regarding doing stick level balancing of the pack. I couldn't find a more relevant thread and was reluctant to start "yet another conflicting" one. I'm hoping that the new owner can follow my advice as well as using this thread to find other's with complementary (rather than conflicting) advice.

My car had a fresh (reconditioned) pack installed around 120K by the previous owner under Honda's graceful extended warranty coverage not long before I bought it. It did not begin to show IMA problems until about 180k miles at which point I began to get occasional IMA light/codes. I began to reset with a 12V power cycle and learned to avoid triggering the IMA, usually through using the IMA too heavily when it was hot... After a year and 10k miles or so it began to get worse and with the help of another Insight enthusiast we pulled both of our battery packs and did several charge/discharge cycles on each stick with a 2 week rest and full discharge to measure self-discharge. My sticks ranged from 4500 - 6300 mAh with only about 4 under 5000 mAh. The multiple charge/discharge cycles did seem to improve the range of each stick and the lower capacity ones (<5000mAh) were also the ones with the highest (percentage) self-discharge. I reassembled the pack and viola no more IMA lights... for a while. Meanwhile my friend who had rebalanced his (which were in better condition overall) decided to replace with a Bumblebee so we swapped his pack into my car, pulled my sticks form my pack and sent the empty "core" to Bumblebee (which is all they want anyway, they were not re-using old sticks). This pack worked well for another year, and I did a complete "rebalance" and "evaluation" of my original sticks whose condition was roughly the same (by measure) as when I'd worked with them before. My intention at that point was to pull the "better" pack, rebalance/test the other cells with my particular method, and put together a more balanced set from the two packs.

Meanwhile I was "overcome by events", bought a 2011 Chevy Volt that was due for a battery replacement and it became my hobby and daily driver replacing my Insight for the most part. Lack of regular use of the Insight only aggravated the IMA condition. I also began to use the spare NiMH sticks from the Insight for other projects like strapping up 5 to drive my 36v electric bicycle and a couple of water pump and fan projects with solar charging.

What I delivered to the new owner was the car with an IMA light that tends to come on nearly every time I drive it unless it is both cool and I'm excruciatingly careful not to push the boost or regen very hard. I included 8 extra sticks, several which I had tested just before I delivered last weekend.

The new owner has a 2002 MT with a grid-charger and is going to be installing a second harness and exercising/grid-charging the CVT before going to the effort of pulling/testing/balancing the pack.

For his reference here is my method for exercising/testing the sticks: I used a GOOL RC balance charger set with their NiMH profile and a 3A (.5C) charge and 1A (< .2C) discharge. My protocol was to start with 2 full charge/discharge cycles, followed by a full charge, a 2 week rest, and a full discharge to measure the self-discharge. I recorded the last full charge, and the last 2 discharges to characterize the condition of each stick. My plan (and recommendation) was to remove the 8 worst sticks from the 28. Worst would be defined by the lowest full-discharge measure before resting (first) and then the lowest discharge (after the rest).

My "theory" is that after the charge/discharge cycles, the last discharge is the amount of useful power the stick can hold when "fully charged" and that the rest defines the amount of self-discharge (from internal nickel whisker formation?). With regular grid-charging, the self-discharge may not be as important by itself. Hopefully there will be 20 good-enough sticks between the 28 that I sent along.
 
21 - 27 of 27 Posts
Top