Honda Insight Forum banner

1 - 20 of 430 Posts

·
Registered
Joined
·
184 Posts
Discussion Starter #1
I live at the end of a few-mile climb. By the time I park my Insight, my SoC is usually at half-charge unless I am really careful with the gas pedal not to go into Assist (easy to do, now that I have MIMA, but I find just the opposite because I'm trying to maintain a high mpg). I would like to be able to gently trickle-charge my Insight IMA battery overnight, even though NiMH batteries are nowhere near as susceptible to damage as flooded lead-acid batteries when left alone in a partially discharged state. I realize that I could fully recharge the battery while going down the hill, but with FAS it's so much fun to start off each trip with the first couple of miles pegged at 150mpg! Eventually where I hope this discussion will go is to a separate thread on battery pack modifications/expansions.

Ok, two primary issues with grid charging (ignoring personal safety-related ones for the moment):

1) Careful regulation and control over the battery charging current and voltage, with battery temperature monitoring a key ingredient. Rates of change of temperature and voltage also need to be factored into this.

2) Recal considerations.

Panasonic has some nice information about NiMH batteries on their website, which show the rapid voltage and temperature increase as the battery approaches full charge: http://www.panasonic.com/industrial/bat ... em/nicmet/

I haven't been able to find any NiMH battery chargers or specific regulators that operate in our Insight's voltage range. Anyone have any suggestions, other than designing it ourselves?

Regarding Recal - yes, we'll be confusing our SoC computer, but it usually finds itself within a few minutes of driving. Eventually we'll need to deal with it, but I don't believe it should hurt anything if we start off with a properly fully-charged battery. Can anyone comment on this?

Has anyone experimented with grid charging of our Insight battery?

Just thought I'd get the ball rolling out in the open. :roll: JoeS.
 

·
Registered
Joined
·
152 Posts
yes

This is the thread you MIMA owners should jump on!

Could you forget about your SOC display and just know your battery pack has been topped up with a gentle over-night charge?

Some elctronic shops biuld their own power supply test panels. A control chip is available that lets you dial in max volts and max current. This is what a 'smart charger' basically does. Of course inside this panel you need to start with a 175 VDC power source or so. You could have an external house current powered muffin fan at the cooling air inlet just while the battery is being charged so the only connection to the car is a low current/high volt / DC/ 2 wire connector.

This is beyond me, but Mike 'The Man' could do this on a paper napkin.

This is an area where MIMA could allow the Insight to be used as a plug-in-hybrid. Like those Prius pioneers are doing. Just use up your charge, gently, during the last 15-20 min. of your commute.

Any thoughts?
 

·
Premium Member
Joined
·
634 Posts
There is enough energy on the Insight battery for about 3 miles, at about 80 mpg average, I don't think it's worth it, unless we had a bigger battery Pack :idea:

I'm looking into increasing the capacity of the battery pack, or increase the cooling capacity on the current pack.

But if you decide to try grid charging please keep us posted.
 

·
Premium Member
Joined
·
4,389 Posts
Grid charging will be the next step to grid charged larger capacity pack. We will have both by next years tour de sol.
The personal safety issues need to be part of the design consideration when making connections to a 144V DC battery pack capable of > 100A. That will fry your A*s pretty quick.
Two people are working on this issue right now.
Armin had his grid charged in the storage bin on MIMA install day.
Sunhunter is working on a ground up design of a complete grig charging system, including a 12V aux supply for powering up the BCM and other circuits to correctly measure SOC while charging.
I will jump in soon once I get the MIMA stuff sorted out.
The other two guys will need to add the details of what they are working on, if they are ready to do so.
 

·
Registered
Joined
·
8 Posts
This is a simple circuit I made that should be able to charge the battery; I haven’t built it or thought of how to connect it yet, but this uses the 1/10th method, by charging the batteries at 1/10th the batteries capacity for 14 to 16 hours. I have made small trickle chargers for NiMH and NiCd battery packs using this method but never with such high voltages. I’m working on a more automatic charging circuit but until I find some more components able to handle the high power I’ll experiment with this.

I wouldn’t leave this on for more then 10 hours at 650mA and even then it would depend on how charged the battery is (like if it had half a charge I would only charge it for 5 hours or less). When first connecting it I would make sure the rheostat is set to the maximum resistance and once connected adjust it until I read 6.5V across the 10 ohm resistor and continue adjusting it until it’s charged to maintain a 650mA current. Just adjusting it to 650mA in the beginning and leaving it during the whole charge time wouldn’t really hurt it but as the battery became more charged the voltage across the resistors would drop lowering the current.

Feel free to point out any concerns or suggestions and if you do decided to use this remember that I am not responsible for any personal injury or damage caused to you, your property or to anyone else’s while building or using this circuit please take all precautions.



 

·
Registered
Joined
·
1,032 Posts
There are a couple of problems not mentioned so far. First, the Insight battery (and the Prius battery, etc.) are not actually fully charged when the indicator says full. It's something around 80% charged at most. (And only discharged to around 20%.) This is to maximize the life of the battery. So you don't actually want to completely charge it, you want to get it to 80% charged.

Also, the SOC meter basically measures the current drawn from the battery to keep track of how full it is. If you don't charge or discharge the battery by sending electricity through the SOC system, it won't know how full the batteries are. So you would start the day with the SOC meter thinking they are, say, 50% full, while they're actually 80% full. After a long uphill run, the SOC system will think they're down to 20% and will shut down battery assist--but they're actually still at 50%.

It seems to me that any non-hack-job approach to charging must take these factors into account...
 

·
Premium Member
Joined
·
2,332 Posts
First point, if you are going to do this don't expect Honda to warrant the battery. (Don't try this unless your warranty is expired)

Second point, charging the batteries without involving the BCM is the electronic equivalent of marital infidelity! (You might get away with it for a while, or not. :roll: )

Third point, As a technologist with 8 years experience designing power supplies up to 10,000 volts, I suggest that most people should not attempt this design. (Mike who has decades of industrial experience with digital control, would probably be an exception.)

Fourth point, as the sticker on the pack says, you could could kill yourself.

Fifth point, If you haven't done the other simpler mods and tips suggested on this forum, you should try them first. :idea:

Finally, as Yves once suggested, there is probably a better way to achieve the same end by using a deep cycle low voltage battery in a complimentary system. A typical boat battery has about the same power capacity, and is roughly 40 times cheaper.

Keith, if I was doing it and I'm surely not about to, I'd probably use a Triac instead of a rheostat or design a current regulating circuit with a high voltage transistor from a computer power supply, use an aviation style 1 amp breaker instead of a fuse, use a single auto transformer (properly grounded), use a much smaller capacitor, build the charger into the car where I could sense the battery temperature, voltage etc. See second point again!
 

·
Registered
Joined
·
184 Posts
Discussion Starter #8
The points b1shmu63 makes about safety in this area cannot be overemphasized, so don't mess with this unless you know exactly what you're doing! :!: :!: :evil:

Zircrose, thank you for providing an input. Whereas a simple low-current input would certainly work if carefully manually monitored, what I am looking for is a fairly sophisticated regulator circuit which takes into account the specific characteristics of NiMH batteries. For example, if driven by a constant-current source, as the batteries approach full charge, there is a sudden increase in both their voltage and temperature - this certainly needs to be factored in as part of safety shutdown. Thus, in addition to any active driving circuitry, at least five monitoring parameters need to be incorporated into this regulator: voltage, current, battery temperature, ambient temperature, and time.

Note that our Insight battery is compartmentalized, with multiple temperature and voltage sensors. There's a whole computer dedicated to just battery management! I'm not (yet) up to hacking into it for our external charger. Whereas we won't be subjecting the battery to the high currents it sees while we're driving, our external control must still be very carefully implemented. I'm rather sensitive to this issue, having seen the results of a conventional battery blowing up -
http://www.katiekat.net/Cruise/KatieKat ... #Batteries

As a number of people have pointed out, a low-voltage battery is certainly a cheap storage medium. What I've already gathered are the ingredients for the front end of this charger: a couple of inexpensive ($9.95 on sale at our local electronics superstore) 400W 12vdc-120vac inverters. Put the rectified outputs in series and, voila, a high-voltage source driven off a cheap easily-recharged 12v battery (Mike D. had suggested this some time ago).

Now, b1shmu63, with your experience do you have any suggestions for off-the-shelf regulator circuits, or do we have to do this all from scratch? JoeS.
 

·
Premium Member
Joined
·
278 Posts
b1shmu63 said:
Finally, as Yves once suggested, there is probably a better way to achieve the same end by using a deep cycle low voltage battery in a complimentary system. A typical boat battery has about the same power capacity, and is roughly 40 times cheaper.
I'd agree with that too! Steve Lapp has used this technique to great effect with his solar augmented Prius. The cells slowly charge the 12V lead-acid battery, which then injects its charge into the main battery while driving. Perhaps surprisingly, the computer seems to tolerate this quite well. It's possible that the Insight management could be equally benign....

There are loads of benefits from going with a 12V battery. First, you're not mucking around with the SOC of a very expensive battery only designed to hover around 60% full, and rarely reach 20 or 80% full. I think if you did cycle it between these two limits artificially day-in, day-out it would come to the end of its working life fairly quickly! Between these limits, the Insight battery only holds about 550 Watt-hours, which is only enough for about 3 miles electric range extension.

Putting in extra battery space would increase the electric range extension dramatically. In fact, lead acid is what the Priusplus amateur group used to give their first development mule 20 miles EV range. It was heavy but it nevertheless cracked 80+mpg. (The "pro" team used lithium-ion for much better results).

Assuming you go with a deep cycle lead acid battery, you could be looking at about 30-35 watt-hours per kilogram of battery. Thus for every mile of daily commuting range you want deducted from your gas bill, and placed on your electricity bill, you'd need about 160 Wh of onboard storage, which equates to about 5 kilos of battery.

For a 10 mile range extension, you'd be looking at about 50 kg of additional battery in the back.

Theoretically, assuming your daily commute is 20 miles, you could cut your gas usage by half using this layout.
 

·
Registered
Joined
·
184 Posts
Discussion Starter #10
Clett, thank you for your comments. As I mentioned at the end of the first paragraph of this thread, I hoped that a separate thread on battery pack modifications and expansions would result. The last 100-yards of my driveway are extremely steep, but I've been using MIMA to pull the car all the way up it in second gear while keeping a very light throttle, thus showing that our Insight can successfully operate *almost* in EV-mode. I would expect thermal issues (motor and battery) to be major constraints. JoeS.
 

·
Premium Member
Joined
·
4,389 Posts
All good points guys
One additional advantage of the 12V system is that the car already has a 12V 75A DC/DC converter that can charge the batteries with the IMA. Granted there are losses all the way around, but it could be a self charge maintaining system.
I happen to have some of the 6V trojan golf cart batteries, from my electric buggies, just need to get some of those cheap inverters.
Regulation could be on the 12V side of the inverter, with feedback from the HV side via an opto feedback system similar to the one I used on the signal isolators in MIMA. The problem is that on the HV pack, voltage cannot be used as the end of charge determining factor, and since we don't want over 80% SOC, we can't look for the dip at end of charge. So determining the charge terminating point is the big nut to crack, once we can determine SOC, the rest is pretty straight foward.
It may be a good opportunity to get a SOC measuring feature into the MIMA software, since the amp signal is already acquired. Then we would hopefully be able to do our own SOC determination, to control the charger. Could be lots of work needed to get that working well and tracking the cars SOC determination, but it would be worth it.
On the other hand, if we could crack the Meter serial com, all of the cars MPG and SOC information would be available for the taking. Then there are the 288V of prius subpacks that I have charged and waiting in my shop.
:wink:
 

·
Registered
Joined
·
8 Posts
I agree that there are probably better methods of doing this. Last night I was playing around with the idea of using a microcontroller controlled DC to DC converter to control the current flow and monitor the battery but using another battery in parallel with the IMA battery sounds a lot better and I think I’ll devote my time more to that.

So what you are talking about is doing something like this right?



Feeding power into the system between the battery module and MDM or somewhere along the line between the batteries them selves and the MDM?
 

·
Premium Member
Joined
·
4,389 Posts
No that was not what I had in mind.
Remember this is an idea forming, so neither of these concepts has been tried, and both may form a good starting point for further development by the group.

The LV system: Solar practicle
We would use a big 12 lead acid for a booster battery. (2-6 volts ok)
This system is a way to slowley do the background charging without the engine load, to keep the main battery charged up.
The 12 V is stepped up to at least 180VDC at at least a 1-10A charge rate, which would only be applied to charge when the system needed help, like on a big hill. It would be like a MIMA battery helper.
Or it could be set to charge at .5 -2 A constantly until a high SOC occured. During times of heavy regen, the DC/DC is allowed to charge this 12V booster battery, just as it would charge the tinsy standard battery, which could be removed from the car. The trick will be to gain control of the DC/DC charger (simple), and let MIMA determine when it is ok to charge up (lean burn)down hill. If the commute is all up hill, you will arrive with a low 12V and a low 144V pack, but you may be able to charge them both up on the way back. Lots of possibilities.

The HV battery booster: Solar difficult (HV)
a 144V booster pack that jacks into a power connector and data connection on the side of the existing pack.
This pack can be any cell chemistry. It fits perfectly right on top of the spare tire, and can be simply onplugged and lifted out.
The BCM on the new battery pack has all of the cell reversal, temp monitoring, and circuit control to properly care for the pack. When this pack is jacked in, it also ties into MIMA, and the PC through the interface.
It lets MIMA know its specs.The cell reversal sensing circuits on the booster pack, would cause the same signal change that the stock subpack monitor does, by reducing the volyage on one tap by 2 V, with a signal from the new pack. Temp problems would fool a temp sensor into thermal shutdown of charge, and diit in a way that
MIMA determines the total AH of the combined packs.
MIMA is monitoring the battery current and could send an adjusted analog ammeter value to the BCM, and fool it into treating the dual pack as one larger pack, so that after a reset at empty, both packs would share charge, the weaker one getting more to balance the batteries condition. A pack failure of open or shorted cell, would disconnect the booster pack, and tell MIMA to put the regular ammeter scale factor back in place.
Lots of development here, as well as lots of field test, but again lots of possibilities.
I can set PIMA to start assist at 100MPG, and be at full assist by the time it is at 90,75, or 50 depending on mag factor, and with full assist traveling over 40mph, I can make many hills with the MPG at 80 during the whole climb. Bigger batteries, will bring 20 to 50 mile range with this aggressive use of the electric priority concept. Anyone can get in the car and drive it once set up, and they will achieve super numbers as well. Put in a 20AH pack, and 100mpg commutes may be more common. Throw in FAS from Calpod with a MIMA joystick interface, and you have one mean MPG machine, or one mean racing machine or a little of both. 20AH would let you keep the IMA pedal to the metal for a whole autox.
Then you add Jacks turbo, and you have one hell of a little race car.
Ok where do we get the time?

:wink: 8) 8) :wink:
 

·
Premium Member
Joined
·
2,332 Posts
Thanks Clett for your (as always) Insightfull input on the historical and potential applications of the lead acid battery in hybrid mods.

Keith, you are close to what I was considering. :wink:

Understand that I will make suggestions based on personal musings. I do not intend to implement any of this while my battery pack is under warranty!!!!

The output of the IMA motor goes through rectifiers before going to the Battery Control Module and then on to the IMA battery pack. I would tie in between the rectifiers and the module. How?...... Buy an off the shelf DC to AC converter. Convert its output to DC using a bridge rectifier. Build a current limiter using a standard PWM chip and power transistor. This would control the current, preventing burning out the convertor, while introducing almost zero efficiency loss. (This could be done at the frequency of the converter provided the inductor and capacitor of the DC smoothing filter was sized correctly.) The output should probably then be split and passed through 3 rectifiers before being tied in with the three rectifiers coming from the IMA motor.

The second part of the mod would be to take the twelve volts and step it up to 14 volts using a high frequency, current limited single ferrite inductor "boost" converter circuit. The output of this would be connected to the existing 12 volt battery through a rectifier.

The effect of this would be to reduce or eliminate both the background charging current for the 12 volt battery and the hidden charging of the IMA pack.

Extra batteries for this mod would occupy the tire well or the "GPS" space at the rear of the Insight. Batteries would be boxed and vented. The rear suspension would be modified using Yves' plastic donut mod. The circuitry would be set up to run only when the car was in operation.
 

·
Premium Member
Joined
·
4,389 Posts
Kip, Clett, Kieth, JoeS
It is easy to imagine lots of booster pack configurations, and for sure grid charging will be desired when we get to that point.
Lets examine the pros and cons:

12V booster
Pros:
It is safer and easier to grid charge a 12V lead acid battery, no HV, predictable end of charge, known characheristics.
If only used as a re charging current source for the stock battery, the internal SOC determining system can accurately measure the incoming charge, and should maintain an accurate SOC display. No fancy voltage or current regulation should be needed, as the current will be low, and the stock battery SOC will determine the final voltage. We will just need to turn it off if the battery gets too full.
Cons:
To up convert to 144+ volts, we will be working against a 10-12:1 step up ratio, so the current available on the HV side will be limited to 1-5A, which is equivlant to the cars normal background charge at best. Not much help for load leveling on the 144V pack, just a "free" source of recharging energy.

HV booster
Pros:
1 or 2 prius subpack based 144V 6.5AH booster packs
If the 2 or 3 packs output current can be matched, the maximum current draw on the stock pack and the booster packs will be 1/2 or 1/3 of the total current draw, and therefore the batterys will run cooler, and be discharging in a more efficient area than the present 100A max draw that the single pack is subjected to.
Cons:
The booster packs will have all of the difficulties and complexities of the stock battery in reguards to SOC, cell reversal, and temperature monitoring. Even when we solve those issues, we need to deal with the safety issues of paralleling the NIMH packs.
Grid charging 2 or 3 144V packs will also add complexity.

The LV system wins on simplicity and safety, and will offer extended assist use even with more aggressive MIMA operation, and should be the first system we try.
Thanks to JoeS, who is sending me a nice Christmas present of 2 of the 400W inverters, and my ready supply of the deep cycle golf cart and marine batteries, I should be able to get this working pretty quickly.
The 400W will only provide 2-2.5 A @ 144V, but the large 6V batteries will put out 1000W for nearly 2 hours, so I may use a single smaller 12V deep cycle battery instead of the 6V ones, to save weight. It should be possible to top off the 144V batteries while charging the 12V batteries with a regular off the shelf 12V charger.
:wink:
 

·
Registered
Joined
·
184 Posts
Discussion Starter #16
Hi Mike,

Thank you for the overview. As usual, you're ten steps ahead of us...

For the first venture into this area I was initially thinking in terms of an overnight trickle-charge. I had envisioned a "battery charger cart" in my garage which would contain a 12V battery, a high-quality 115vac-->12vdc battery charger (I have a lovely programmable Victron Energy 30Amp charger), the two 12vdc-->115vac inverters each feeding a diode bridge and putting those two outputs in series, and a high-voltage regulator to feed the Insight's battery pack. I was thinking charge currents into the 144v Insight battery pack of less than 1/2 amp. My initial motivation was that I didn't like the idea of leaving my Insight's batteries discharged for any length of time, and I recognize that there would be a negligible contribution to lmpg.

In the 12V Booster system, you are proposing an onboard 12V power source completely separate from the car's 12V battery (for now), but with significant charging currents over some period of time which may potentially contribute to increasing our trip fuel efficiency. Need to do the math (someone?) to see how much contribution 12V @ 225AH will provide, at the penalty of carrying a couple of 65lb. batteries onboard.

The next steps (parallel HV Booster or 12V->HV high-current booster) are more exciting from a mpg standpoint.

The primary challenge is to properly control the Insight's battery charging regimen, and, as you pointed out, what better way than to try to activate and utilize the Insight's BCM for this process. The inverter HV output filtering and regulation (if any) can then be quite simple. I would expect the BCM to completely cut off any input when the battery is "full" ("80%"?). Mike, I presume that's your initial technical pursuit?

What would you like us to help you with? I'm looking at finishing the Engine Ready and Heater Standby signal measurements at the ECM and then implementing FAS before moving into this (after I finish with pesky end-of-year administrative issues). JoeS.
 

·
Premium Member
Joined
·
4,389 Posts
Joe
I think the key point to remember about grid charging is the relitively small advantage that Clett's estimated 550 Watt-hours capacity in the stock battery, which he figures will only be enough for about 3 miles electric range extension will bring to bear.
Compare this to having a load free background charge always running A simple 200V max 2.5 unregulated dc supply, would do the job nicely, and could be turned off by us initially when the SOC shows near full, as you would be in the car and driving anyways( just one more thing to keep you from getting bored).
When the charge gets down to the 30-50% SOC range, we turn it back on. On a long down hill, if the 144V pack was near full, we could charge the 12V booster battery using the DC/DC converter, to get a regeneration of charge in the booster battery.
Based on the 400W inverter, we will only be drawing ~ 25-35 A from the 12 V system at full output.
The 12V trojan SCS225 is rated for 56 minutes at 75 amp rate, and over 3 hours at 25 A rate, and weighs 66 lbs.
The 400W constant charge should keep the HV battery up as long as we use the assist carefully, and continue to use the cars regen capabilities to good advantage.
The beauty is that all it will take to increase the boost capacity is to go to a bigger inverter, then to a higher capacity 12V system.
Should be interesting.
:wink:
 

·
Premium Member
Joined
·
498 Posts
my experience

Here are some unscientific observations from my grid-charger experience:

After I got MIMA, I used the grid charger for a while, getting 72 - 75 mpg on my daily commute (35 miles each way, mostly highway). Now, this was in cold weather and with winter tires. Last years average for these conditions was around 60.

Then I had trouble with the charger (turned out it was the extension cord!). So I used MIMA in charge-sustaining mode for a week, with mileage droppig to around 65. Weather conditions seemed the same, but as you know they never really are in New England! After I figured out the problem and used the charger again this week, I was back up in the 72+ range.

So from this quick study, MIMA seems to save 0.1 gallon, while adding the grid charging saves another 0.1 that's about a gallon per week! MIMA will pay for itself in two years, as soon as gas prices rise to $6 a gallon! But we all know it's not about accounting :cool:

My basic MIMA strategy is to use the motor to allow staying in lean-burn as much as possible, and charge on downhills so the FCD stays between 100 and 125 mpg, still in lean burn, not entering fuel-cut mode.

I don't agree with calpods observation of a battery capacity enough for 3 miles at 80mpg. Maybe uphill with a stiff headwind! But on a flat road with MIMA, you can go quite a ways at 80 mpg / 60mph before the battery runs out. I haven't measured this, though.

I also noticed that MIMA allows drawing the full 90A out of the battery for extended periods of time. This helps to avoid downshift on onramps, but it is a concern for battery wear. MIMA also bypasses the limited asisst in low-battery conditions, which is helpfull since I regularly run the battery empty when I get home, but I again have to be careful to not use too much asisst when it gets empty.

Interesting observation on the SoC gauge: it goes down smoothly to 3 bars as I use up the battery charge. Then it stays at three for a very long time. My suspicion is that it only goes to two after the BCM senses a low battery condition, probably the same as a recal.

Oh, before I forget: my grid charger is a string of 24V and one 9V AC-DC power supplies in series to get 178V. Then I connected an LM7805 with a 15 Ohm resistor as a 0.33 A current source. I connect this for about 12 hours each night, which is enough to trigger an upper-end recal when I turn the car on in the morning. Soo the true battery capacity between 3 bars and full is less than 4 Ah. And this is a new replacement battery from Honda.
 

·
Premium Member
Joined
·
4,389 Posts
Armin
I aggree with your range comment. I can stretch a charge out for a 50 mile trip (pumping it back at every oppertunity). My car does that same 3 bar thing but only when it is cold. all summer, I was able to go smoothly right dorn to 1 bar, but in the cold, it seems to stick at 3. Last winter, it would sometimes stick at three, and would not force charge for days. I figured it was some kind of recal. This year with MIMA, I can keep the pack between 3-4 bars and 3/4 full most of the time.
We never got to connecting the big dc connector on our packs on install day. Where do you tie your charger into the battery?
 

·
Premium Member
Joined
·
634 Posts
Armin Wrote:
I don't agree with calpods observation of a battery capacity enough for 3 miles at 80mpg.
Armin, I think you misunderstood what I wrote, please read again what I posted.

I wrote that the battery charge is good for about 3 miles, at about 80 mpg (which is what I currently average) I don't think it's worth it, I think with more battery capacity, it may be worth it, but you can usually make up the mileage with careful driving.
 
1 - 20 of 430 Posts
Top