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I don't think the total voltage factors-in to any of the key management.
Possibly right, it's the consistency of voltage between taps which appears to be the key factor.

This voltage difference between BCM's caused the earlier issue with the OBDIIC&C code, where I tried to correct the reported voltage to the actual voltage.
When I released that code people found it did not work consistently across different BCM versions. So I removed it and the OBDIIC&C reports what the BCM thinks the pack voltage is now rather than what it actually is..
 

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Do either of you, or anyone else, have any idea why there would be such a discrepancy? For example, is it likely to be an electronics design choice difference, a different setting, maybe they're programmed differently on purpose for who knows what reason, maybe there's some electronics deterioration/issue that happens over time? Just seems like getting the correct voltage reading for the whole pack wouldn't be such a challenge, but then, I don't know a lot about what goes into it...
 

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I don't think the BCM uses Bvo for anything other than a comparison to Mvo.

If it uses pack voltage for anything, it uses Mvo for the pack voltage limit of 192V.

IIRC, Bvo can't be more than 10V different from Mvo or you'll get codes. Maybe the manipulation of Bvo is to tweak the threshold of that error?
 

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I'm thinking that, for whatever reason, Mvo and Bvo might be swapped internally when it comes to the 305 and 010 BCMs, like the 'addresses' - so if with the OBDIIC&C you pull up Bvo on the 305, the voltage value might be comparable to Mvo on the 010 BCM. I switched over to Mvo on the 010, and the voltage value looks like what Bvo would be on the 305... I might swap back to the 305 just to check, if I have time today... I don't think I ever looked at Mvo on the 305 BCM...

Other than that, I'm recalling some OBDIIC&C switch-a-roos back in the day, when Mvo was the Bvo value. At some point, maybe about 2 years ago, one of the OBDIIC&C updates caused me to have to switch from Mvo to Bvo to maintain the same value in logs over time...

Later... OK, **brain fart warning**
I swapped back the 305 BCM to check the voltage discrepancy thing - and it turns out I hadn't been reading "Bvo" on the 305 after all; I had been reading Mvo. So yes, there was a difference between the 305 and 010, but only because I was comparing Mvo on the 305 to Bvo on the 010. Bvo and Mvo read exactly the same on both BCMs, Mvo was 6 volts higher than Bvo on both versions...

I also read voltage with a calibrated DMM. I measured 157.2V for the whole pack, 157.23V sum of tap voltages. So given these readings, compared to the readouts on the BCMs:
Mvo value is +2.8V vs. actual
Bvo value is -3.2V vs. actual
...

Sorry for the detour...
 

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I swapped back the 305 BCM to check the voltage discrepancy thing - and it turns out I hadn't been reading "Bvo" on the 305 after all; I had been reading Mvo. So yes, there was a difference between the 305 and 010, but only because I was comparing Mvo on the 305 to Bvo on the 010. Bvo and Mvo read exactly the same on both BCMs, Mvo was 6 volts higher than Bvo on both versions...

I also read voltage with a calibrated DMM. I measured 157.2V for the whole pack, 157.23V sum of tap voltages. So given these readings, compared to the readouts on the BCMs:
Mvo value is +2.8V vs. actual
Bvo value is -3.2V vs. actual
...

Sorry for the detour...
Old saying, "A man with one watch knows what time it is. A (new politically correct) person with two watches is never quite sure what time it is." ;)
 

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Ever since I put in the JDM lean burn ECM my CVT is now hitting the battery hard. Regen seems to be down 20% or more and assist seems to be up 30% or more, both leading to a lot of background charging. In addition the assist does not improve MPG but actually hurts it.

I believe I have an A01 BCM. What other BCMs might give me more regen and less assist? Currently the assist is so sensitive I need to be careful or I will continue to use assist on even the slightest grade, even after getting up to speed.

If anyone has a BCM for sale I am looking to buy other BCMs to try to help this issue.
 

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Ever since I put in the JDM lean burn ECM my CVT is now hitting the battery hard. Regen seems to be down 20% or more and assist seems to be up 30% or more, both leading to a lot of background charging. In addition the assist does not improve MPG but actually hurts it.

I believe I have an A01 BCM. What other BCMs might give me more regen and less assist? Currently the assist is so sensitive I need to be careful or I will continue to use assist on even the slightest grade, even after getting up to speed.

If anyone has a BCM for sale I am looking to buy other BCMs to try to help this issue.
I have the same problem with my lean burn CVT. It works fine on the highway, but short runs around town keep the SOC below 50%. It just refuses to stay out of assist when accelerating. I wonder what is different about our cars. Surely the "stock" Japanese cars in the UK don't all do this. What BCM do they use? Or did we miss something when we did the rewiring at the ECU when we did the swap? Maybe it needs one of the wires that we left disconnected.

Sam
 

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I have the same problem with my lean burn CVT. It works fine on the highway, but short runs around town keep the SOC below 50%. It just refuses to stay out of assist when accelerating. I wonder what is different about our cars. Surely the "stock" Japanese cars in the UK don't all do this. What BCM do they use? Or did we miss something when we did the rewiring at the ECU when we did the swap? Maybe it needs one of the wires that we left disconnected.

Sam
Please correct me if I am wrong; From what I have read is that the 2000 and 2001 BCM's ran hot, overheating the IMA Modules. Switching out the BCM for the 1K100-PHM-A03, which seems to be the 2006 model, keeps the charge in between 20% and 80% charge and keeping the IMA Module cooler. My question is: Can this 1K100-PHM-A03 BCM work on Manual Transmissions as well as CVT's?
 

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Any BCM can work on Manual or CVT's

The same in fact applies to the MCM's although they are marked as CVT or MT.
The differences are minimal.
 

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Please correct me if I am wrong; From what I have read is that the 2000 and 2001 BCM's ran hot, overheating the IMA Modules. Switching out the BCM for the 1K100-PHM-A03, which seems to be the 2006 model, keeps the charge in between 20% and 80% charge and keeping the IMA Module cooler....
I've never heard/read anything like that. The only bonafide problem I've seen reported is described in posts 21 (bottom of post) and 35 in this thread - a cold weather problem, where the car might allow too much power under assist... Anecdotally, people have also reported that, in cold temps, background charge persists a lot more than usual, charging the pack longer and higher than it normally does. But I don't think that's ever been considered a problem per se...

My understanding is that all the BCMs have a general usable capacity window between about 20% and 80% nominal, with minor variations at the top... In typical driving the actual usable window is much smaller though, as there's a soft lower limit where assist is greatly reduced, harder to invoke, harder to keep going, with gas-engine charging kicking-in automatically (i.e. 'background charge' or 'forced charge')... That soft limit seems to be around 15V or so resting and/or around 38% nominal charge state... And then, it's more like 65% if you have your headlights ON and/or a heavy 12V load...

Anyway, differences are hard to spot unless you've run these things on a bench and systematically tried to find the differences - something I haven't done. I've just read what other people have reported over the years, and I've watched the OBDIIC&C IMA parameters as well, which has helped me glean some insights. If there's one difference that might make a difference, one that I'm aware of that's pretty common, it's the top end charging: some BCMs set the top limit to basically 75%, while others allow charging beyond 75% up to about 81%. I think there's probably some marginal benefit setting the top limit to 75%, in terms of longevity, and also, probably in terms of efficiency... But I don't know which part numbers are the ones that stop at 75%... I know it's not the 010 or the 305...
 

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Thank you Peter for clarifying the interchangeability of both the MCM and the BCM.
Thank you eq1 for the in-depth findings on this issue. I will go back to see what it said about the modules getting overcharged by the early BCM's.
I have a 2004 CVT with a Bumblebee that ran good for 2.5 years before I bought the car. 1 year later up blinks the 1445-78 CEL. I changed out the MCM and the BCM for 2005 units. It runs better but still has the same CEL. It reads 123 volts only when the engine is running. 0 volts when not running and will not accept a grid charge. Yes, the module breaker is turned on. My reasoning for what is wrong is that there is a stick with a short in it thus no voltage unless the motor is giving the module voltage. It won't grid charge because there is a short in one stick. I parked it to research what happened.
I found a 2001 MT with a two year old GreenTech battery. It ran great for one month after buying it and now the 1445-78 blinks on this one. My plan is to pull both batteries apart and build a battery with the 20 best sticks from both of these upgraded ones. I would prefer not to over charge this refurbished battery, if I can help it.
Any advice is much appreciated.
 

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Correction the CEL was the 1449-78.
 

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Well, if you have/had a shorted stick that would obviously cause problems, and possibly ruin your BCM from what I recall. You should post a separate thread about your problems and see if others will help work through them. My understanding is that there aren't any BCMs or MCMs that cause major problems, and no swaps that will fix any problems you have - unless you've actually damaged the units.
 

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It reads 123 volts only when the engine is running. 0 volts when not running and will not accept a grid charge. Yes, the module breaker is turned on.

Have you read the tap voltages now that the battery is in the car? That will tell you if there is an open in any of the sticks.

With zero volts there is an open somewhere in the battery connections etc.

One of the other members will have to tell us if the battery control system has a limit on the maximum voltage (123v in this case) it will apply to the IMA system with an open battery connection.


My reasoning for what is wrong is that there is a stick with a short in it thus no voltage unless the motor is giving the module voltage.

A shorted cell in one stick would reduce the total battery voltage only by ~1.3 volts or so; not reduce the pack voltage to zero.

It won't grid charge because there is a short in one stick.

It doesn't work that way. A grid charger will charge a normal IMA battery with no problem starting below 100 volts. You could probably have several sticks completely shorted and the grid charger would put a charge into the rest of the pack.

If it won't charge that sounds like an open battery condition. There are many things that could cause that; an open battery strap connection or the relay not closing or the breaker sw not completing the circuit etc.

Basically anything that doesn't complete the battery circuit.

What voltage is the grid charger putting out when attempting to charge the battery? If it's the same as not having the harness plugged into the charger then there is definitely an open in the harness or battery pack somewhere.


Any advice is much appreciated.
I would find out why you can't charge the battery in the car now. You might go through the work of building another battery only to find it won't charge either.
 

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I would find out why you can't charge the battery in the car now. You might go through the work of building another battery only to find it won't charge either.
I may have actually damaged the unit. The person I bought the 2004 from had installed a ECM/IMA reset switch. I began to get the IMA CEL every two months, I would reset it. Then twice a month. I would reset it. Then weekly, then daily. Good chance, I cooked more and more sticks as I continued to reset it. Hopefully others learn from my mistake. Once the IMA CEL comes on, fix the problem then reset the ECM or you may cause more damage to your pack.

I measured the voltage from the two poles on the top of the battery pack. I also measured the voltage from the connections of the grid charger. Both read the same. Zero with engine off, turned engine on, it would rise to about 123v. I would turn off the engine, The reading showed a slow drop to zero again. My grid charger puts out 300 miliamps. When I hook it up, I get a reading of 5 volts input max. Even after 3 hours it stays at 5 volts.

Good advice to beware of rebuilding only to find it does not work. I have read of fellow insighters that have rebuilt packs only to find that the CEL comes on. I will save up and take it to who many members say is a very good mechanic here in So. Cal, Scott in Covina, I will have him tell me what is happening and will fill you in as I get more educated. These are still one of the coolest cars on the planet, so efficient.
 

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Understood. Will accomplish and report back. Thank you
Ok, here are my tap voltages:
C9 and C20=16.4 C15 and C14=16.2
C20 and C7=16.3 C14 and C13=16.3
C7 and C18=16.4 C13 and C12=16.2
C18 and C5=16.4 C12 and C11=16.2
C16 and C15=16.3 C11 and C10=16.2
 

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They look Ok enough for it to start/engage the IMA. (Ideally they should be within a few mv of each other)
Can you measure them with a more accurate meter?

Have you measured the pack voltage at the grid charger connection points on the battery switch board?

Have you checked the main 100A fuse?
 

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They look Ok enough for it to start/engage the IMA. (Ideally they should be within a few mv of each other)
Can you measure them with a more accurate meter?

Have you measured the pack voltage at the grid charger connection points on the battery switch board?

Have you checked the main 100A fuse?
At the moment, I do not have a more accurate meter. I will see what I can find.
I measured the voltage at the grid charger connection points and the reading was 0 volts as it was 0 at the top two main terminals with the breaker turned on.
I was thinking that the 100 amp fuse may be blown. I hope it is that simple. Not cheap, but simple. I will take the board off to see what the state of the fuse is and report back. In case it is the 100 amp fuse, do I go to Ebay and buy a used one or buy it new from Honda or new from a secondary vendor that may sell at a reasonable cost?
Which is the best choice? Thank you for guidance.
 
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