replacing main hybrid battery for 03 Prius

I would ask each one:

• How do they measure the Ahr capacity of the modules?
• What are the range of Ahr capacity of the modules used in a pack?
• How are they charge-balanced?

Bob Wilson

 

There are more than one way to handle each. That each vendor has a reasonably credible approach described, it means they are addressing these key technical functions. But if they say 'huh', does not bode well. Also, my criteria are not 'cast in stone.' If Rex Taylor pipes in, I would defer to his years of experience. Also, Lucious Garage, Arts Automotive or any of the regular independents who visit here like Paul or Eric. These guidelines are lessons I've learned from my experiments, not by building, selling, and supporting packs over their many years.

Incoming modules should be washed, dried, and the terminal seals inspected for obvious damage. Older NHW11 modules should NOT be used due to higher internal resistance and weaker terminal seals. They are the least reliable, not impossible, but I would (and did!) pay for NHW20 modules. If someone is rebuilding NHW11 modules, well expect to be back in the same place in the future. The one exception would be a new, Toyota NHW11 pack, actually virgin modules stored and maintained by Toyota but you have that price already which should be in the $2,300 range for just the modules.

The normal specifications for our 6-cell, NiMH modules is 1.2V/cell down to 1.0V/cell. So nominally they are in the 6.0-7.2V range. But in practice, we can push the boundaries . . . a little. So please take the following as 'tickling the tiger' and by no means recommended practice without being willing to pay the price of making a serviceable module into a piece of smoking junk.

Measuring Amp-Hour (Ahr) capacity means getting the modules to a known, initial voltage in the 5.9-6.1 V range. Then apply a constant current, 1-3 A to charge them to an upper limit, typically up to about 8.5 V while looking for: a dV drop signaling charged or; a temperature rise (a safety limit) or; a maximum voltage, say 8.4-8.5 V. Modules typically show the dV drop when they have had a chance to rest ~48 hours. Then measure a fixed discharge current 1-3 A back to a fixed, low voltage, 5.8-6.0 V. The amps multiplied by duration in hours is the Ahr. There will be two, a charge Ahr and discharge Ahr. The discharge amp hours is the trustable rating. The charge amp hours is imprecise due to three potential charge limit conditions, dV, temperature, or voltage.

Modules having a minimum of 3.5 Ahr should be used but it is more important that the modules be within 20% or less of the same value. So a pack of 3.2-3.8 Ahr modules would be 3.5 -10% and 3.5 +10%. They should be matched into 19 pairs with the weakest and strongest together, 3.2 and 3.8 Ahr pair, These should be located on the ends, the coolest places. The stronger pairs, more closely matched, should be in the middle. These are not absolutes but guidelines to ask.

There are multiple approaches to balancing the charge. Charging them to say ~7.6-8.0 V and letting them sit for 24-48 hours and measuring the self-discharge works. I'm also OK with parallel all of the modules and charge up to ~7.8 V or discharge down to 7.5-7.8 V. Regardless, one thing should be universal, automation.

Anyone who claims they are doing this manually without either a well crafted, custom circuit or computer monitoring . . . I would avoid. Manual monitoring of these dang things is 'nuts' and should be avoided at all costs. We're humans and you really want the module testing and evaluation to be automated so the metrics are reproducible.

Also, I'm not a fan of cycle charge-discharge to 'restore capacity.' My testing indicates whatever the effect, it is transient and disappears within 24 hours. Others may have had more luck but that has not been my experience.

That you had the good sense to ask here is a first step. But there is a lot of engineering 'art' needed to build a quality pack and I've only addressed the modules. The buss bars and sense wires all need attention and anyone who reports replacing with new versus refurbishing the old gets a plus in my book. Rex developed a technique to nickel-plate the buss bars and that is a brilliant solution. I've also read impressive reports about cleaning.

Well I've written a lot more than expected yet strangely, not as much as I could. Hopefully, enough to give you a clue on what to look for. But I would endorse anything Rex, Paul, or Eric may volunteer as they are 'in the business.'

Bob Wilson

 

Most companies will not answer these questions and say that their process is proprietary.

I can tell you that you will get what you pay for.

The dealer is selling you a brand new battery. (Although I, and other shops can sell a brand new one for much less)
I'm certain that the $700 is not a brand new battery.

Are you considering installing it yourself? Or can you do it with phone assistance?

I'd be happy to give you some advice and help you wade through the options. Feel free to call any time.

 

Brand new battery installed for $2k.
I'm interested who this is. Or did the dealer come down on price?
Call or email mail me, or post here.

 

That's a great price. New Toyota batteries come with a one year warranty, did your installer extend that?

 

I bet that the "brand new" battery with 3 year warranty was not a brand new "zero mile" battery. They probably sold you a Dorman refurbished battery which is OK, if it lasts, but many shops have experienced failures in less than a year with those batteries. As long as the warranty is in writing you should be ok, and hopefully the warranty includes labor also.

 

I wonder if they did the full transmission fluid change along with cleaning out the pan.

 

What pan? It is just a drain and fill.

 

In a Gen1 there is a pan that can be dropped, cleaned and reinstalled with a new gasket.

JeffD

 

Yep. Hopefully the full job was done. But then again, maybe they did not realize the OPs car has a pan either.
Here is a thread from Paul of Boulder Hybrids.

"If you take it to a shop, insist the mechanic drops the pan, cleans the pan, magnet, and input screen.
The dealer does not typically do the procedure this way, so insist it gets done properly. "

Gen1 tranny service DO IT NOW! | PriusChat

 

Not to mention the pan magnet which looks like a swollen slug after it becomes covered in metal debris.

 

I apologize. I didn't realize this was a Gen I thread, and didn't know the Gen I has a pan.

I learn something new every day and am grateful.

 

That place in Upland replaced my battery. It's lasted about 30k in my car so far and I've had no complaints. Although, I never got the best feeling there. There website is terrific but the shop is pretty rough.