Prius battery pack

[Kurt]

I just picked up a Toyota prius battery pack from ebay .The pack is from a 2nd gen prius that had traveled 20,000km and is apparently in very good condition. I have a couple of questions.

I want to use them on my 48v e bike . From what info could dig up on the cells I worked out I could use 7 of the 38 modules to make a 50.4v 6.5ah pack. The modules way 1.04kg each so each 48v pack would be around 7.28kg. I would like to run two of the packs to make a 13ah 48v pack that would weigh in at 14.56 kg. My 48v sla pack is around 17kg and the weight is fine in my bob trailer.

What I am not sure about is charging the packs. I don't plan on trying to emulate the prius bms and get 1000 years use out of the battery though I don't want to kill them with the wrong kind of charger.I don't have much experience with NIMH.

At the moment the only charger i have is a sla 48 volt 1.8 amp smart charger prob no good to me now? . What kind of chargers do the e bike 48v nimh battery's come with ? What about when I try and parallel two sets of the 48v packs is nimh ok to run like this ? I remember reading something about charging nimh in parallel is a no no. I guess I could charge them individually.

Any help on making the best use of my 38 7.2v 6.5ah Nimh modules would by great.

kurt.

 

[docnjoj]

I dont believe U can charge the packs in //. Astroflight makes a high quality up to 48 volt Nicad/NiMh charger that is very bulletproof. Im sure others will offer suggestions! Ebikes.ca has NiMh 48 volt chargers. U cant use SLA charger, only dt/dv.
otherDoc

 

[Kurt]

The 48v charger from ebikes ca looks ok . not sure if the voltage will be ok as the pack has a nominal voltage of 50.4v?

 

[docnjoj]

Fully charged NiMh should be around 1.4x volts per cell! So a charged 48 volt pack should read around 56 volts+/-. It seems to be low.
otherDoc

 

[Kurt]

The pack wasn't charged in the picture.I tryed just to pep them up a little on my 48v sla charger just for 15min or so and the pack voltage came up . On the 1.8ah charger I prob put in about 1/2 an ah of charge. I turned the charger off when the pack hit 56v under charge but it didn't take very long. i then pluged it into my ebike. The wheel spun a bit faster than usual under no load.I tried stalling the bike against a brick wall with a meter on the pack and the volts didn't sag very much at all. I then took it for a quick ride around the block. I only got 1/2 way around the block down and the power dropped off like they were going flat so i limped it home. When I got home I put a meter on the pack again and the voltage wasn't that low.

This charging method of turning the charger off then the voltage gets to 1.4volts per cell seems to be reached to fast like 20 mins. if the batterys are flat on a 1.8 amp charger a 6.5 ah pack should take around 3.6hrs to fully charge then.

 

[gasfree]

Did you have any luck coming up with a way to charge the batteries Kurt?

 

[dirty_d]

so each cell is 6.5ah?

 

[Kurt]

I am not having much luck with the battery's at all. I am able to charge mine to 8.3 volts but they seem to reach this voltage very very quickly as in 10 min but when you put them on the bike they are flat in 2 min. mine just seem so sensitive to charging. Even when they are flat after 2 min of riding they still show over 7 volts.

For me personally I am thinking i will try one last thing that is charging 2 modules at just over 16v at 4.5ah using a ibm laptop charger I will charge 6 batterys in total. I just need to get my hands on the charger.

If this works and they take a charge to there full ah capacity without overheating or expanding great if not its the bin for all 38 of them.
there is a chance they could be all stuffed as they were sitting for a while. Though I have some AAA nimh that have been sitting uncharged for a long time and they seem to take a charge ok who knows.

My 4 x 20ah sla pack just seems to have a lot of balls , very little voltage sag and isn't sensitive to voltage all and the rest but its just heavy.

 

[gasfree]

What was wrong with the battery when you bought it? Bad cells or was it just taken out from a car in an accident? I managed to make a pack back in june with a warranty battery I had at work. It went pretty quick at 48v. I had 7 cells in series. I didn't know how to charger them and I didn't to risk blowing anything either. I was able to play with it for a good 30 mins over two days and had no problems. I did notice that the voltage did drop a bit but then again I had no way to charge them. I will look through the technical stuff at work and see if they have any useful info.

 

[Kurt]

My pack was from a damaged car with 20,000km on it but could have been sitting uncharged for years for all I know.as some of the cells had well under 7v on them when i first got it.

oh yes the cells are 6.5ah each and there is 38 of them in a pack.

 

[powermed]

kurt, I think those batts are toast.
z.

 

[mrbigh]

Let me tell you that by the description you made and the pictures of the Prius traction pack you bought, it is from a generation 1 Prius, sold through 2000/2003. These are OLD batteries and the shelf discharge rate is 5% a month for NEW ones.
These first gen batt have had problems venting and loosing their potential energy storage.
You may need a NiMH battery restorer and balancing "charger" to select the best ones of your 38 count pack and discard appropriately of the "dry" ones.
I own 7 of these Prius packs for my Prius PHEV conversion. :wink:

 

[Ypedal]

1st thing is to get the proper charger, then to cycle them 3 or more times at low rates, then determine if they are relly junk or not.. cool toy tho !! thanks for the pics ! :wink:

 

[Mr. Mik]

What is the lowest number of cells in a string that ou can access for charging? I cannot work it out from the pictures.

Ideally you would get access to the individual cells with 1.25V and test and charge each one by itself.

They are probably badly unbalanced due to varying self-discharge rates.

 

[powermed]

Folks looking for high performance commuting distances from 5 - 10 miles might strongly consider newer (gen III) prius cells. I've been using them exclusively on a daily basis for months now, they perform very much like A123 cells which I've had, but no longer use due to lower voltages, capacity, complexity, and far greater number of cells.

Not only can they deliver big amps continously (easily > 50 based on my actual use) they can be charged in less than an hour. Mine (a 6 cell, 44.4v pack) are set for a one hour charge. Bolt terminals, fit into various bags with chargers perfectly, etc.

These Prius cells are much more rugged than folks have commented on in other threads, based on the original article published in the 1990's (and my experience). These are good for 1000's of cycles and are exceedingly long lived. Just do not get cells more than a year or two old, packs should be from the same original battery, resting voltage around 7.4 when you get them, etc.

I've made some for family and local colleagues that are commuting, and have a few extra's I made from the last Prius battery I bought I'm selling on ebay (do a search for 44.4v* if you want to see the construction and read about charging).

I assume the technical types here might want to buy a full prius battery, carve it up etc rather than pay for ready made packs. I'm personally not into the group buy thing but someone here might have the inclination.

 

[Link]

One thing I didn't see mentioned: These cells need to be under compression. I guess they puff up and die if they're not.

 

[Kurt]

the latest thing I have tried with my prius packs is to charge each 7.2v pack using a high quality swallow rc charger programmed to detect 3ma dv. I can program the charger to what ever amps I want and have tyred charging at anything from 1amp to 6 amps.

I find that after a discharge cycle the most ah I can fill the battery to is 3ah or around 30min of charging time at 6 amps and then the cells start to swell up.I have even found under heavy discharge loads like 40amps they can swell up to . It is kinda like as soon as you put them under any stress they just fizz and carry on .I would be interested to know if anyone is using the plastic packs without compression.
kurt.

 

[powermed]

I've experienced no such swelling under either high load, or charging at 4.5A to 8.3v or delta T via infrared thermometer. Swelling is a function of internal gas production which typically occurs during over-charge. My brother who's ruined more than his fair share of Gen III cells has even tried very expensive NiMH chargers used in the prof. vidcam industry. All have failed to nail the charge. I've not lost a single cell using a "manual" method. At one point I used a stethesocope to listen for gassing at the vent. Over 8.3v and you can hear it.

According to the original paper and other research, NiMH can handle very light/slow overcharging with internal chemical reactions (H production). I do not think compression is needed in newer cells that are well treated. I've got at least 200 cycles on my current production pack that I use (and charge) twice each day.
z.

 

[Kurt]

Ok so when you start charging the battery what is the resting voltage before you charge? Are you saying it takes a full hr for them to reach 8.3v? I did find that the nimh charger wants to feed A higher voltage into the cells that makes the pack rise to 8.3v to fast .I take it your only feeding them with a controlled voltage over just over 8.3v - 8.4?

If you are charging for 1hr you are putting about 4.5ah into them. So I take it you are only using them to this capacity each ride .

 

[powermed]

Hi Kurt,

The resting voltage has always been above 7v in my experience. I stop using the batteries as soon as I notice a drop in performance, which should correspond to about 80% drain by the technical paper if all cells are balanced (and they are). I've also become quite comfortable riding for 5 miles into town, plugging it in for 20 - 30 minutes during my coffee / lunch and riding home. Typically I set the timer for an hour, and the 8.3 is usually hit sometime towards the end of that time and the fixed voltage chargers tend to cool, indicating reduced amp flow.

My typical ride does not end with a drop in peformance, so given that and the charge time I'm assuming the drain is less than 5.2amps. The power supplies are not fixed current, so after starting high, they taper towards the end as the batteries fill.

z.

 

[Lock]

http://wardsauto.com/ar/price_prius_batteries_080925/
Toyota Lowers Price of Prius Batteries
By Eric Mayne
WardsAuto.com, Sep 25, 2008 8:08 AM
PORTLAND, OR – Toyota Motor Sales U.S.A. Inc. is cutting the price of replacement batteries for its first- and second-generation Toyota Prius hybrid sedan.

Nickel-metal-hydride units for ’00-’03 models are reduced to $2,299, while batteries for second-generation Prius cars now cost $2,588. Replacement batteries for both generations previously cost $2,985.

“We’ve stated from the beginning that battery-replacement costs would continue to decline due to technology and volume-related advancements, and we believe this will continue,” says Gary Smith, Toyota’s corporate manager-product quality and service support.

The batteries are subject to warranties of 10 years and 150,000 miles (240,000 km), or eight years and 100,000 miles (160,000 km), depending on the state where the vehicles were purchased.

How many have needed replacing? “Enough to fill the navel of a gnat with room left over for two caraway seeds,” boasts Bill Reinert, Toyota’s colorful national manager-advanced product technology.

Toyota spokesman John Hanson is more precise: About 300, he says. The NiMH batteries, therefore, have demonstrated 99.95% reliability, considering the auto maker has sold a total of 635,632 Prius models in the U.S., according to Ward’s data.

Some 300 Prius hybrid batteries replaced to date.

Batteries for Toyota Motor Corp.’s hybrids, including Lexus-brand models, are sourced from Japan’s Panasonic EV Energy Co. Ltd., of which Toyota owns a controlling interest.

Meanwhile, the auto maker says it is studying the business case for remanufacturing Prius batteries in the U.S. to further lower replacement costs.

Toyota, which is hosting a sustainable mobility seminar here, has its eye on an annual output of 1 million NiMH batteries by 2010, along with a similar target for lithium-ion battery production.

The auto maker has said its first plug-in hybrid electric vehicle, set for testing in commercial fleets late next year, will feature Li-on technology.

emayne@wardsauto.com