[Yves M.]

Hi,

I remember that asomeone had plugged a windmill to charge his Insight's IMA battery. I wounder if anyone has built a home current charger.

I was wondering about this as I think that the IMA battery should last longer if mostly always kept charged. The resulting MPG might be better while in the 'only city' driving e.g. going to a local workplace

My question is:
If the battery is charged externally, does the SOC monitor of the car show the true charged state or will it show the last 'known' charged state from before being charged by the external source.
What would be the charge voltage , 144v or more.

 

[No. 166]

I would think that a permanent "full" battery would be bad. That's why there's always the recalibration.
A battery lasts longer if the charge changes. :wink:

 

[Armin]

Yves,

I think this has been discussed a few times.
Look at my posts in this thread.

 

[Yves M.]

Hi ,

Thanks for the link.
I checked it out and you are right.

One thing it brang up to mind:
When you do an MCM reset, the charge indication is out on the first seconds but after a while, the battery management figures out the battery state that is more than empty and shows it correctly.

This points to me that a plain dc charge (with charge level checks) to the battery only could work. The IMA level would be shown correctly maybe not at startup but while driving

 

[b1shmu63]

If the voltage monitor finds the battery voltage to be much higher than it expects according to amperage measurements it will force a recal. This won't harm the battery once in a while but it will drain off any extra charge gained by external charging.

 

[Armin]

If the voltage monitor finds the battery voltage to be much higher than it expects according to amperage measurements it will force a recal. This won't harm the battery once in a while but it will drain off any extra charge gained by external charging.

You have a point: If the external charge doesn not go throught the current sensors (or you don't keep the car on), the battery will be full without the car knowing. You might get an upper-end-recal as a consequence of this, but it won't drain any charge. All that will happen is that on the first serious braking maneuver, the car will sense the battery is full and set the SoC to show full.

 

[Rick]

No what would probably happen is the car senses the battery soc is our of sync, it dumps the soc meter then enters force charge until it realizes now it's really overcharged the pack. You've probably gotten it a little excessively hot by this point. Then it would probably default to the upper range of SOC which is 80% when it's really at 100%. So then it will be operating in a SOC range higher than it's supposed to which would probably eventually trigger additional recals. Overall this would shorten the life of your battery pack. And besides the amount you would gain from external charging probably wouldn't benefit you much if any.

Just a theory, but I'm not aware that the software can just change the SOC without dumping it and force charging until it realizes where it's at.

 

[b1shmu63]

That's right because the only reliable reference is the voltage drip that results from discharging the battery about 80 percent.

:idea: If you want to charge a battery do it to an auxiliary 12 volt battery. Use it to power the fan, wipers, radio etc....

 

[Armin]

Just a theory, but I'm not aware that the software can just change the SOC without dumping it and force charging until it realizes where it's at.

It can. It does it almost every time after a recal for me: It charges up to 16-17 bars and then jumps to full. I call it the upper-end recalibration. I'm sure it's based on a similar mechanism as the lower-end recal.

So if the SoC has 10 bars on it, but the battery got charged over night, it will just need to upper-end recal and everybody is happy.

Now, that's just a theory to...

 

[Rick]

Yeah I've seen the gague jump but only after a recal. It will never just jump up unless it dumps the SOC and enters force charge recal mode first.

 

[Armin]

Yeah I've seen the gague jump but only after a recal. It will never just jump up unless it dumps the SOC and enters force charge recal mode first.

I have seen it, but very rarely. It happened when it was so very cold for a few days on a strech and my SoC was down in the 5-10 range the whole time. (This was after it got to full after the previous recal.)

Then there was a warm day, the SoC charged up and at 17 it jumped to 19.

I think the only reason it doesn't normally happen is the same one that causes so many lower-end recals: The errors add up in to favor a too high reading on the SoC, never too low.

 

[Rick]

Huh, now thats really interesting. What year is your car? I've never ever seen that in my 02, but then again you said when it's really cold which my car has never ever seen much more than a few degrees below freezing maybe for a fer hours durring the coldest of winter nights here.

 

[Yves M.]

HI,

So readding all the messages, I will start looking at a way to keep the SOC at the -1 bar which is about the 80% real charge total

The way I drive and the route I take (start/stop all the time) keeps my charge level from 1/4 to 1/2. I seems to be low for a battery, year around.

This way I will discharge it during the day and back up at night. Battery will be exercised but will not always be low. As if I was doing it while driving.

As soon as spring comes, I will get to the IMA and check out the voltage when the battery is cold (not using car before), while the SOC is -1 bar.

I suppose that if the result is for an arbitrary example 143.7 volts, all I need is to provide that DC voltage (no more) and I will not harm anything. It will also charge slowly since to my knowledge the voltage is never under 140 volts

From the document at figure 6 http://www.ctts.nrel.gov/BTM/pdfs/2001_testresults.pdf
the voltage seems to be at around
158v at rest while no charge
140 when empty
almost 175 while full charging

Yves.

 

[b1shmu63]

Will you try to fool the computer into thinking the battery is fully charged while draining it driving to work and back?

Have you done everything else possible to increase your MPG?

Have you calculated the extra distance that the pack will take you?

Are you considering adding additional batteries?

Kip (formerly de La Belle Provence)

 

[flunkysama]

2 things ....

1) Looking at the manual, I think that if you tap the junction board at the right place and have the car turned on (the engine does not need to be running), you can probably charge the battery pack and have a correct SOC. There are 3 problems with this. A) If honda finds out, your warantee is dead, B) You can overcharge your battery pack, unless you can decode the serial line that the BCM talks to the MCM with. C) You will drain your 12V battery. Oh, and there might be a 4th problem, when working with this stuff, touching the wrong thing can kill you! Other than that, have fun.

2) I'm pretty sure that the BCM detects full charge in the battery pack like most good consumer battery chargers, by temp. Once the batteries are fully charged, any further charging causes them to heat up. In a recal, the quick jump to full is probably because the BCM saw the temps climb quickly in the pack.

 

[Yves M.]

Hi,

I drive my Insight as if it was an ordinary car. I do not watch the MPG display but drive with the flow of cars. I did not think of fooling the car computer or care of the SOC indicator while driving. Though I see it before starting and it is fairly always below half.

My only reason is to try to keep the battery life longer. It has been 4 years since I use the car and I really expect the battery to 'live' for the 8 years Honda garanties it.
I do not beleive that it will still be good enough for me but it will for Honda. I do not expect them to replace it. They will say that it is still good even if it does hold charge just a little.

They do not even provide a test procedure, it is the car computers that give the indication of being bad:
that is good only for a manufacturing problem like shortcircuit or total death. Not for "normal" wear like charge holding.

I checked the Panasonic links given on the Hybrid group and with time, I expect the charge to be 'capacitor' like: charge quickly and discharge quickly
That is already what has happen since the 'cold weather' BCM recall done in 2001 or 2002. The battery seemed to charge faster (less time) and discharge faster as if they let the SOC indicator show a smaller portion of charge e.g for example from 50% to 80% instead of the original 20% to 80%.

I doubt that adding a second battery would increase MPG because the car computers will probably not take that into account while charging/discharging. Unless the new battery would be put in parallel to the existing one but that would discharge into one another because of different internal resistance

I see a dc charger should not only check the voltage but the temp too, thanks.
Warrenty is an issue and I need an easily removable battery connection

I will check what is available as charching circuit plans and info.

 

[b1shmu63]

Yves, if your primary concearn is battery longevity, then I would think that leaving the computer to control the charge level would be the safest thing. The computer keeps the charge between 20 and 80 percent. If you charge the batteries untill they heat up they will in fact be overcharging. That will definately shorten your battery life.

Some of my Electronics experience was developing charging systems for telecomunications equipement. I wish I could offer you a practical solution, or at least make some more positive suggestion, but because of the extremely low internal resistance of these batteries, the only reliable way to determine the state of charge within the 20 to 80 percent range is to monitor current flow versus time with occasional verification such as the recal we see on the Insight. For that reason you really have to let the onboard computer sense what is happening.

Kip

 

[Yves M.]

Hi,

If the only way to charge is through the computer, then the easiest thing would be to (every one or two weeks) stay it the car and ride the engine at 3000rpm until the battery shows full. Else it would be to complicated.

I did it this morning. I do it every once in a while since my charge level is always 1/3. But once every two times, I get a power stering warning light. It does disapear once I drive but I think that the EPS is on the 144v and does not like the overvoltage while charging. I would not want to damage the power stering (removing a fuse everytime will probably wear out the fuse holder or my patience)

Looking at the Panasonic links, it did not sound to complicated. Seemed like charging nicads except that nimh does not like to 'trickel charge'.
I thought that charging at 0.2 It (1300mA) for a maximum of 8 hours or a gain in tempature of some degrees would be enough. The temp could have been stopped by checking the 4 sensors into the pack. Check this scanned page of the battery pack internals:
http://www.md92raid.100freemb.com//misc ... y_mod.jpeg
you will need to remove the "http://" in front of the URL for it to work

Panasonic info
===========
Our 6.5 AH individual batteries:
http://www.panasonic.com/industrial/bat ... HR650D.pdf

Some generic NiMh info:
http://www.panasonic.com/industrial/bat ... erview.pdf

Device design using nimh:
http://www.panasonic.com/industrial/bat ... utions.pdf

Charging methods:
http://www.panasonic.com/industrial/bat ... ethods.pdf

Battery pack general info:
http://www.panasonic.com/industrial/bat ... yPacks.pdf

I might have to forget about that idea.