Do-it-yourself battery pack change

[rusty41251]

Radio shack sells 1.2 volt NiMH "D" cells. 120 would cost $1,020. Is it possible to replace these within the battery pack? If not could one easily replace the entire battery pack with another say from a junk yard? I understand they run about $800? Or is this a job for Honda.
I am running fine at the moment, but someday........
Rusty

[Insightful Trekker]

Recently asked and answered here:

http://www.insightcentral.net/forum/vie ... php?t=4127

HTH!

[rusty41251]

Sorry, I did a search and it did not come up near the top so I took a chance. I should have known it would be a hot topic though. Also the Radio Shacks are only rated at 4500mAh. But I will be putting on a lot of miles so I was just thinking ahead. I doubt they will last 350000 to 400000 miles or 11 years.
Rusty

[Insightful Trekker]

No apology needed.

Unless you spend too much time in here (like me) you'd have missed it

[IamIan]

The Insight Batteries are Industrial VERY High Amp Drain rates... up to 80 Amps from a single D Cell.

Even if you were going to do this.

Radio Shack D Cell NiMH aren't worth buying.

Radio Shack $16.99 for a 2 pack of 4500 mAh
1.2V x 4.5Ah ~5.4 Watt per cell x2 pack ~10.8 Watts/16.99 ~ 0.63 W/$
120 Cell / 2 = 60 packs of 2 x 16.99 = $1,019.40 for ~648 Wh

Overstock.com Has $19.50 for a 2 pack of 12000 mAh D cell NiMH
1.2V x 12Ah ~14.4 Watt per cell x2 pack ~28.8 Watts/19.50 ~ 1.47 W/$
120 Cell / 2 = 60 packs of 2 x 19.50 = $1,170.00 for ~1,728 Wh

or $151 dollars or ~13% more for ~167% More Power.

Of course you can get much less expensive NiMH D cells if you just want the cheapest you can get... but ultimately for the Insight you need D cells that can handel 80 Amps .... Very Few Can.... it is like ~12 times the Battery Capacity as a discharge rate or ~12C.

I use the 12000 mAh NiMH D Cells in a 30 cell 36 Volt Battery Pack I made up for my Electric Assist Pedal Bike that drawls at peak 20 Amp... They handel this ~1.6C discharge rate without any thermal management really needed and the company that makes them says they can handel repeated use at up to 25 Amp rate ( or ~2C ) without any long term damage, more than this and they recomend having a rigorous battery management system.... to get 80 Amps would be a 6.6C rate more than 3 times the recomended normal rate.... 80 Amps is just allot of Amps....

You would also have to break apart a Insight battery pack to get all the sensors and such that you need for the car to use the pack ...

Oh and it is over 144Volts .... This high of voltage CAN KILL YOU.

my 2 bits.

but good thought anyway.

[Dougie]

All that aside, it's also a question whether the battery management computer would work right. It's trying to keep the batteries partially charged all the time, so presumably there are various constants in the programming that would not line up with the replacement batteries...

[Insightful Trekker]

Originally Posted by Dougie

All that aside, it's also a question whether the battery management computer would work right. It's trying to keep the batteries partially charged all the time, so presumably there are various constants in the programming that would not line up with the replacement batteries...

As long as your working with NiMH's and the capacity of the pack is the same or greater than you'll be fine. If you "oversize" the capacity of the pack it probably won't be utilized by the existing software.

Again the _biggest_ "problem" is the high capacity discharge rate requirement. _ANY_ battery not up to this task _will_ rapidly weaken and fail. The only "easy" workaround would be to disable the IMA starter, install MIMA and limit the IMA's loads to within the installed batteries capacity.

HTH!

[Mike Dabrowski 2000]

gobuchul74 was nice enough to send me the old Insight pack that he was trying to rebuild for only the price of shipping.Thanks ED.

I can fit 144V of prius batteries inside the case if I do a bit of hacking and make a new air handling system. My first impressions are that it could be made to work as a replacement for our D cells in the same form factor. Unfortunately the subpacks and temp probes for the Insight pack were already removed, so I can not use them to duplicate the temp circuitry and try it.
The prius pack has the same number of subpacks, and the same capacity cells, so the voltage taps could be moved from the old pack to the prius based one. The temp sensors could also be made to work. The biggest chalange will be to run the cooling air through the prius subpacks. The rectangular prius subpacks with the flat sides tend to bulge out when near the end of charge, so in the prius pack, they are held between two reinforced metal plates and are clamped quite tightly, so a similar clamping arrangement would need to be designed. The existing relay current sensor assembly can also be used, with a bit of wiring . In my non existent spare time, I will be building up my replacement pack, so I will be ready when it finally goes bad.

[Dougie]

I don't think I've ever had my assist gauge all the way over to the end. Well, maybe once or twice as an experiment, but during normal driving--even on the long steep hill in my commute--I never go past half-way. So depending on driving habits it might be ok to have less than full current draw capability.

On the other hand, I frequently have full assist showing...

Another idea would be to incorporate an add-on circuit to limit the assist current.

[Calpod]

Dougie wrote:

Another idea would be to incorporate an add-on circuit to limit the assist current.

I posted on such a circuit a while back, see "how to disable assist/regen" on Modifications thread.[/url]