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Discussion Starter #1
I started this to unclog another thread and have moved the info here.

I created an equalizer box that uses 10k resistors to simulate the voltage signal that IMA computer gets. If it reads all equal voltage, the IMA light stays off. You need a spare battery loom to get the plug that connects to IMA module. Works great for me. Been using it for 6 years.
This gave us a clue someone was using a BCM fooler style 10k resistor matrix with NIMH to bypass imbalance detection.

Do you mean you are using a resistor matrix to simulate perfectly balanced sticks with a NIMH pack,
defeating the cars ability to detect imbalance?
Meaning cells can be over or undercharged and reversed without protection?
Do you still have ptc strips fitted?
Can you post details on here in a separate thread please so we can see what you're doing?
TOPT Replies

Yes, defeated factory balance safeguards, but kept all the temp sensing.
First concerns raised.

Interesting experiment, but given the long history of NiMH failure modes and the series configuration of the cells, maybe not too promising. Detecting those voltage differences between the stick pairs is one of the built in battery safety measures Honda designed into the pack. Defeating that will leave safety shutdowns to the next line of defense, which I suppose would be the PTC circuit, assuming it is installed. Interesting to see it tried - just not on my car ;)

Been driving that way for 6 years, so I certainly swear by it. Would I sell it to layman? No way! But for diy who can smell when battery is stinky, and knows how to drive it to keep battery charged it's the greatest!
Also, it's only to get more use out of batteries that are no good.
85732
 

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Discussion Starter #2
I have considered this mod years ago but have always dismissed it as potentially too dangerous.
I certainly have never tested it with NIMH. So would I consider it now?

1) It removes a big protection system from the battery management and falls back on the secondary over temperature monitoring. I would certainly want PTC strips present and possibly the fan on at all times.

2) It will certainly damage cells if they get consistently reversed or severely overcharged.
But if the pack is a basket case anyway does that matter?

3) It means individual cells have to get very hot 80C or so before the IMA would shut down.
This would almost certainly cause venting and electrolyte loss with early replacement green sticks.
They leak like sieves at the best of times anyway!
OEM Sticks rarely leak, so OEM packs might tolerate this a lot better and are likely to have the PTC strips fitted.

4) The pack would behave like it was perfectly balanced and operate between it's minimum and maximum pack voltage limits.
The SOC would probably go up and down as normal, in fact allowing deeper cycling as it won't cut off when a cell goes empty or full.

5) It's an easy and cheap mod to do but you need a BCM Tap connector plug.


Interesting... I wonder if it's worth testing in a bit more depth with a basket case IMA pack.
 

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Yeah, I think it is potentially a dangerous experiment. If the battery should catch fire, there may be little warning or time to react. Fires are rare, but we have had them. The heat shrink is flammable as is the foam rubber anti-rattles and the plastic case. As retepsnikrep points out, if you should have the later Chinese Max sticks in the battery, the risk is most likely greater.

Quote topt, "Been driving that way for 6 years, so I certainly swear by it. Would I sell it to layman? No way! But for diy who can smell when battery is stinky, and knows how to drive it to keep battery charged it's the greatest! "

Considering the large variations among old batteries, you may just be lucky. I actually saw a battery, probably a cell, get so hot that it created a minor fire, just with grid charging levels of current (1.5A.) Fortunately the cover was off, and several of us were watching and were able to take immediate action. If one considers the normal coverings over the battery, a fire could be much slower and more difficult to suppress.

It is interesting, sorta like watching a film gunfight(sick humor), but I don't think I'd want to try it. :)
 

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Discussion Starter #5
I don't think suppressing the idea or deleting it is appropriate.
IMO we should discuss,evaluate and make recommendations.
 

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OK, for discussion sake, I don't think this is safe enough to mess around with and should be avoided unless your car is expendable. As retepsnikrep says above, the voltage pair sensing is one of the primary safety measures. When those go off, it means there is a weak cell, seems to me. That cell is going to reverse and take high reverse current if assist is used much at all.

Certainly, the practice should not be tried without an intact PTC circuit, which would shut the battery down with an excessively hot cell. JMHO.
 

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I might experiment with this. My Flying Cap board displays/monitors stick pair voltages from my OEM pack while driving. All the PTC circuits are there as well. Anyone have a spare BCM Connector tap plug they would be willing to sell?
 

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They are oem batteries. I did some testing with a homemade ten vom monitor and in both charging and discharging while driving,a pack that would trigger IMA shutdown, voltage varied only a couple tenths.
 

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I think for legal liability reasons, Honda probably programmed a safety factor of at least 100%, maybe 300, so I'm not worried.
 

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I noticed right before an IMA code was thrown on my 2000 Insight, the car did a series of charge and discharges on the battery, as observed on my OBDII C&C.gauge. I think Eq1 is probably correct when he thought the car measures the slope (change in voltage over time) to determine battery health. I think that's what it was doing with the charge/discharge scenario right before the IMA light came on.

My 2001 CVT has a way to monitor stick pair voltage while driving, and even though the battery isn't great, the sticks all stay within one or two tenths. I have noticed the 2001 CVT car is much easier on the HV pack than the 2000 manual transmission car. I'm still monitoring it, to see what happens with an old pack.
 

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I noticed right before an IMA code was thrown on my 2000 Insight, the car did a series of charge and discharges on the battery, as observed on my OBDII C&C.gauge. I think Eq1 is probably correct when he thought the car measures the slope (change in voltage over time) to determine battery health. I think that's what it was doing with the charge/discharge scenario right before the IMA light came on.

My 2001 CVT has a way to monitor stick pair voltage while driving, and even though the battery isn't great, the sticks all stay within one or two tenths. I have noticed the 2001 CVT car is much easier on the HV pack than the 2000 manual transmission car. I'm still monitoring it, to see what happens with an old pack.
I have noticed that exact thing, and I believe it is system diagnosing battery condition. At the time I had voltmeter and ammeter panel so I could see what it does. After using the resistor device, mine has survived that mode without tripping IMA light repeatedly. Voltage will drop off, but system just stops giving any assist until battery is charged again.
 

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That's interesting and good to know. I'm monitoring my CVT battery to try and determine what the car is looking at to throw an IMA code (e.g. voltage discrepancy between sticks). So your pack would throw an IMA previously, but now that it's seeing stick voltages all the same, it's no longer throwing a code.

I guess the charge/discharge scenario is to determine state of charge, and voltage differential is used to look for a pack imbalance. When the two meet a certain criteria a code is thrown, or maybe just the imbalance is what triggers it. I think they must work in tandem, rather than just the imbalance, or else why did the car do the charge/discharge? Maybe to decide which code to throw?

In any event, from my observations, the voltage differential must be held pretty tight. I have a 3% discrepancy warning on a crappy pack that I'm monitoring, and it hasn't come close to triggering on the CVT pack.

Did the car stop doing the charge/discharge scenario since installing the resistor matrix?
 

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No, it will do that on occasion, just like it will with good batteries. Another thing it does is limit charge and discharge amounts for a while, I think when cells get too warm.
 

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No, it will do that on occasion, just like it will with good batteries. Another thing it does is limit charge and discharge amounts for a while, I think when cells get too warm.
However, no codes or shutdown.
 
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