replacement batteries

[kalmar]

Just spotted these, 10AH NiMH D-cells.

http://www.batteryspace.com/index.asp?P ... ProdID=325

Unfortunately it has a maximum discharge current of 50A whereas I think the cells used in the Insight happily cope with 100A.

Still though, $5.56 each means $670 for a pack's worth, and if you bought twice that amount you could possibly run parallel strings for discharge (if there's room).

[highwater]

Gee's, I like to have 10 AH out of my pack

Randall

[IamIan]

well... The insight Battery Pack Technology is over 6 years old... and Since they did go with a mass produced D Cell base.... I guess eventually we will see the 80 to 100 Amp charge and discharge rates availible at cheaper prices... Gota love that technology wheel... keep on turning....

Also ... IF they are rated at 50A each then 2 pack in paralell would do 100 Amps total if both 120 cell paralell packs were putting out 50A.

The bad news is fabricating each pack so it can handel 50A and the 80 to 100A combined system.... Not to menchion working with 144+ Volts.... and the worst news of all..... Without a hack to the Insight battery computer the Amp counter wouldn't use the extra capacity even if it where there.

[Dougie]

I still think that the "requirement" for a 100A discharge rate is overstated, at least for the hypermileage crowd. How often do you actually use full assist? It might be enough to just put a limit on the assist...

[Insightful Trekker]

AFAI remember Armin is the only member to have done some direct IMA current measurements and post his results. When the IMA is in its "starter motor" function the drain is 90A+-.

Another "problem" with simply paralleling a double pack to get around the current limitations is that you double the number of cells. And decrease the time before one cell reaches its failure point and begins to pull down the _whole_ array.

Reading the fine print on the given page the highest recomended discharge rate is only 30A. With the qualification that service life will be reduced. 40-50A loads are routinely seen with full assist (albiet only for a short time, battery life saving usage).

IMO its not a good candidate for replacement of our IMA batteries.

HTH!

[Mike Dabrowski 2000]

Armin did some of the early battery monitoring with the battery test connector, and has been monitoring battery voltage as well.
All of the MIMA users are taking direct current readings whenever they use the system. the MIMA ampmeter is pretty accurate, and with the new PWM display can easily show a 1 or 2 amp change.
The Stock IMA will use 90-100A when doing fast acceleration in first and second gear, but only for 5-10 seconds. MIMA can use it at will. I have ran many 1 minute 100A discharges with my pack with only a 1-2 degree temp change.
The only way you will be able to really know if a cell can handle the current is to get 6 cells and try to make a subpack with them, then test them under load, while measuring current and temp.

Paralleling NiMH is difficult because of the low internal resistance, and the need for independant cell reversal detection on each two of the subpacks in each of the parallel packs. Thats 10 temp and 10 voltage measuring circuits for each 144V parallel pack.
If I am going to go with parallel Prius packs, I would also put in dynamic cell balancing, which would be able to charge weaker subpacks.
not a simple task.

[Dougie]

Paralleling would also effectively double the capacity of the batteries, so the IMA would only use have of the capacity it thinks it's using. It would also halve the voltage, so you'd have to have twice as many batteries.

However, there is a big mystery here, because the batteries have to come from somewhere. There is a factory making those batteries and the trick is to figure out a retail supply chain that gets them to us.

Alternatively, the ratings on the retail batteries are listed on the conservative side (unlikely for typical sales brochures), or Honda is using the cells outside their rated range. I suspect the latter.

[IamIan]

I remember reading somewhere that the NiMH D cells in the Insight are made by Panasonic... can't recall where I read that off hand right now.

It would make sense though since Panasonic is the same company that make the 15 Minute Rechargeble AA and AAA that Radio Shack sells and they make other 15 Mnute NiMH cells for other companies too...

I think something like that requires extreamly large purchase orders and minimum quantity order numbers... Tracktor Trailer Truck pulls up to loading dock at Honda factory... "Got a order of Batteries here, can you sign for it?"

I mean 120 cells per car Honda sells what just under 2,000 Insights per year?.... 2,000 x 120 = 240,000 D cells ..... even if you went through alll the red tape to be able to buy them.... that is allot of Money... even at the super cheap rate of $4 per cell that is a million dollar order.

[Insightful Trekker]

And Honda also announced the Sanyo would be its competator supplier. Not sure when the mix / match, is / was supposed to take place.

[Mike Dabrowski 2000]

To help with this battery discussion, I put up a battery pack exposed page like I had on the old website. With photos of the Insight and Prius packs opened up for comparison.
http://99mpg.com/batterypacksexpose/
I will expand it to include controllers and such at some later time.