Prius Batteries - How to make them work

I'm running Mod3 Prius NiMH 24s3p for 32volts starting output. I run them down to 24volts. They aren't draining much over the course of a week: 32 to 31.5. I don't know how many amps that equates to. Charging is highly variable, between 14 amps and 19 amps. Good temperatures on the batteries, meaning they stay cool except for the final charge phase. The product from the ebay Prius battery rebuilder in NC is outstanding and reasonable.

to clarify: the MRC jumps over to trickle when 15-19 amps have been pumped into the bank.
I got a marginal improvement of performance when I took a fully charged bank and put it back on the MRC. The super brain pumped 6 more amps into it before it shifted over to trickle.

I bought an Imax B6 charger to help charge my Prius modules. I've read the directions several times, and I am still quite lost how to use it. I was hoping to charge/discharge them. Only 10 modules of the 33 I have purchased are holding voltage more than a few days. Can someone give a description of how to set it up so that even a 3 year old (or ME) could understand it?

Can't help on the Imax. Further on the MRC Super Brain. It has no voltage control, only batt type (liPo, NicCad, NiMHetc) and number of cells and amps and temps. Max cells for NiMH is 24. Thats 4 prius modules of 6 cells each. I've got a massive battery of 648 cells, and the MRC is keeping it together. Latest adventure has been to ask the MRC to handle 216 cells at once, 24s9p. They fill up at about 3+ amps. I haven't take the charger from depleted batteries at 50-60 percent yet; just to top them off and attempt to even them out. Nothing is blowing up, no high temps. One or two modules are getting extreme green grunge buildup at the Prius terminal, and I presume these are leaking chemistry. Still, the voltage remains high. All my modules come from the NC ebay dealer. Great product.

vpoppv said:

I bought an Imax B6 charger to help charge my Prius modules. I've read the directions several times, and I am still quite lost how to use it. I was hoping to charge/discharge them. Only 10 modules of the 33 I have purchased are holding voltage more than a few days. Can someone give a description of how to set it up so that even a 3 year old (or ME) could understand it?

Click to expand...

Set it to NiMH.
Set current to 0.6A
Set timer to 16hrs.

I don't think the IMAX can do discharging but I might be wrong.

If the modules do not hold voltage for more than a few days then I think they are stuffed. Good modules seem to hold voltage for many months.

blisspacket said:

Can't help on the Imax. Further on the MRC Super Brain. It has no voltage control, only batt type (liPo, NicCad, NiMHetc) and number of cells and amps and temps. All my modules come from the NC ebay dealer. Great product.

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The cell type is a voltage control. They just tried to make it idiot proof.

For my education would you please define a "module"? How many cells in a Prius "module"? Can you take the module apart? From the pictures, I think I see several cells in series in one tube. Is this the module?
Thanks;

Gordo said:

For my education would you please define a "module"? How many cells in a Prius "module"?

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blisspacket said:

Max cells for NiMH is 24. Thats 4 prius modules of 6 cells each.

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a module consists of 6 cells.
each cell is 1.2 Volts.
module voltage = 6*1.2V = 7.2 Volts (nom)

the first gen NHW10 modules/sticks (the ones in a tube) are built up from six individual 1.2 volt cylindrical D cells which can be separated back into individual 1.2 volt cylindrical D cells (6 cells * 1.2V per cell = 7.2V per module).

later gen use prismatic modules containing six flat 1.2V cells molded together into a single package that cannot be separated into individual cells & 7.2V is the smallest voltage increment the pack can be broken down to (6 cells * 1.2V per cell = 7.2V per module).

everyone on the same page now?

Thank you. The construction of the later module had me puzzled because at first the picture looked similar to a 3.6V TS cell. At first I thought it was very hot chemistry to get 7.2V from a cell. Now I know there are 6 cells it is very clear.

Hi Guys
This is my first post, and I see some of the guys from Insight central in the mix.

I have been using Prius cells since 2005 for a number of projects including use as a 12v starter battery.
http://99mpg.com/mikestips/themusefulpriussub/
Since the cars voltage regulator tops out at 13.6V, the cells do not get overcharged.
I did have a cell short on one of the 12V packs, and the two subpack series string rapidly destroyed it self as the other cells quickly got overcharged.
I tend to charge the cells with solar, and if not carefully watched they can get quite swollen as the internal pressure bulges the cases.
http://99mpg.com/blog/batterypacksexpose/diditagainforthela/

In a Prius, they regularly are asked to put out up to 120A, and are charger at > 90A.
They are pretty tough, but do not tolerate cell reversal without damage, and will rapidly gass to the point of the case fracturing once they get fully charged.
If the high rate charging is dropped back to a safe 250-350ma for the final topping, one can charge these puppies very fast.

I have been using a very simple charging system that can be built from off the shelf switching power supplies. :wink:
350ma version:
http://99mpg.com/Data/resources/downloads/relateddocuments/grid_charger_balancer_2.pdf
1A dual rate version:
http://99mpg.com/Data/resources/downloads/relateddocuments/dual_stage_grid_charger1.pdf

The beauty of this charger approach is that one can charge a single 6 cell stick or a 350V pack, and everything in between, and it is made from off the shelf power supplies.
My experience with the charger and the prius cells has been pretty good. The 350ma CC can be applied to the subpacks for several hours after the cells are fully charged with only mild swelling, which allows save pack equilization.

The cells were configured as a 36V pack to power my solar charged hotrod mobility scooter:
http://99mpg.com/blog/pluggingintothesun/californiaorbustso/
The solar panel is set up as a 200ma and 400ma CC charger, with an autocutback to 200ma once the pack reaches ~40V.

Full prius packs as a PHEV booster system for the Insight:
http://99mpg.com/Projectcars/phevinsightiigetti/

I will soon be selling a microcontroller based universal charging system that will be able to charge from a single 7.2V subpack to a full gen 2 Prius pack at over 260V, with settings for the Insight 2 100V, Insight and civic 144v, 158V newer civics and prius 200V packs.

I use dual subpacks as my lawn tractor battery.
To start and run my 1965 John Deer backhoe.
In my electric forklift. In the forklift I use 2 of the dual 12V packs in parallel to supply the over 150A draw of the 12V hydraulic system.

Bottom line, they are a great battery of use for a large number of applications, and the good availability in junkyards makes them a great deal for the money.

Good to see you here, Mike!

Always most interesting to have a look at what you are up to. I wish you had more time!

Just a total newbie here, having just discovered your site ... I've spent several hours reading everything I could on using the Prius Batteries ...

I had thought I would have to use several hunded pounds of the heavy lead acid batteries for a small 48V - EV project, a BMW Isetta (Urkel Car) weighing 600 lbs ... using mostly upgraded 48V electric golf cart parts for the electric system ...

The cost of the Lithium battery's such as LiFeYPo4, Thundersky or Headway batteries are just too high ...

Is it possible to use the Prius Gen2 battery pack as a 48V battery power source by grouping the cells into 4 separate blocks of 7 (7x7.2V) cells in series, then being used as a 48V power supply while mounted in the origional Prius battery case ... 4 blocks or 7 for a total of the 28 cells at 48V ?

It seems like such a good choice ... the price mainly, but also durability with all the R&D that Toyota has done...
It would be almost pre packaged while still arranged in the origional Prius battery box using primarily the origional mounting and connections between the cells with the ability to replace damaged cells as required ...

Is it possible ?
Could it be charged as 4 separate blocks of 7 cells at 48V ?
What would the best or cheapest method of charging or managing each 48V block of cells ?

With the current availability and cost of the used Prius batteries ... I realize that I may be able to build a much better EV now than I had thought possible, with not having to carry around the weight of lead acid batteries, but I will definately have to do alot more research on what would be required for battery charging and management using the technology in recycled Prius batteries ...

DavidP said:

Just a total newbie here, having just discovered your site ... I've spent several hours reading everything I could on using the Prius Batteries ...

I had thought I would have to use several hunded pounds of the heavy lead acid batteries for a small 48V - EV project, a BMW Isetta (Urkel Car) weighing 600 lbs ... using mostly upgraded 48V electric golf cart parts for the electric system ...

The cost of the Lithium battery's such as LiFeYPo4, Thundersky or Headway batteries are just too high ...

Is it possible to use the Prius Gen2 battery pack as a 48V battery power source by grouping the cells into 4 separate blocks of 7 (7x7.2V) cells in series, then being used as a 48V power supply while mounted in the origional Prius battery case ... 4 blocks or 7 for a total of the 28 cells at 48V ?

It seems like such a good choice ... the price mainly, but also durability with all the R&D that Toyota has done...
It would be almost pre packaged while still arranged in the origional Prius battery box using primarily the origional mounting and connections between the cells with the ability to replace damaged cells as required ...

Is it possible ?
Could it be charged as 4 separate blocks of 7 cells at 48V ?
What would the best or cheapest method of charging or managing each 48V block of cells ?

With the current availability and cost of the used Prius batteries ... I realize that I may be able to build a much better EV now than I had thought possible, with not having to carry around the weight of lead acid batteries, but I will definately have to do alot more research on what would be required for battery charging and management using the technology in recycled Prius batteries ...

Click to expand...

First of all, David, welcome to the forum!

The answer to your question is Yes. Each 7 modules would series up to a nominal 48V block. You could then parallel the 4 blocks. Leaving all the 28 modules in the original pack would be fine. I would try to discard the heavy outside steel shell, though. You can reuse the 125A Prius fuse as the pack fuse, after combining all in parallel.The problem you are going to run into is having enough capacity. Each 48v block would be rated at 6.5ah. For 4 blocks in parallel, this would be 6.5ah x 4 = 26ah total. In reality, each module only gets about 4ah, so 4 in parallel would only yield 16ah expected.

I am currently helping a friend that has a golf cart 48v system. He wanted to convert the whole thing to Prius batteries. A review of that cart showed he had approximately 200ah of capacity with his SLAs. So we opted to simply add a whole 28 module Prius battery pack to his existing SLA pack, using the same 4 blocks of 48v (in parallel) as you had wanted. We are charging the Prius blocks in parallel using a Soneil 4804SR. It is slow, but gets the job done. The Soneil is factory set to go from CC to CV at 57.6V, which is perfect for the 7 module block. Much more than that and you start to destroy the battery. Ask me how I know.

You should exercise the Prius blocks before placing in service, discharging and charging as many cycles as you can, and do each block the same. This will help recover the capacity. This makes a great deal of difference for batteries that have been laying around for a length of time.

I hope this helps. Good luck with your project.
--Tom_D

Thank you Tom ...

Its difficult to compare the performance of the lead acid batteries and the prius NiMH batteries ...
I though the energy density would be greater with the NiMH batteries ... even assumming it would probably take the batteries from 2 packs to give a reasonable range at 48V for a 600-700# EV ...
With the Prius battery being 28 cells at 6.5ah(20) x 4 packs to equal up to 26ah(20) ... using 4 x 12V flooded batteries at 150ah(20) seems like a huge benefit ...

Using this calculation ... 6 complete Prius packs ... 168 modules making 24 - 48V Packs of 7 modules each at 6.5ah(20) x 24 = 150ah(20) ... = roughly equal to = ... 4 x 12V flooded lead acid batteries at 150ah(20) each in series from standard 48V golf cart batteries ???

Or am I getting confused relying on ah(20) rating as compared to actual energy density of the different batteries ????

Am I just going to have to stay with the standard lead acid golf cart battery ... as it seems it will be a little over 300# for the either the Prius or lead acid batteries ... ?????

Some of my experiences in case it may help someone:

I scored about 120 of the Panasonic HHR650D cells about two years ago for $80. I think these were the same cells as the 1st gen Prius. They were of unknown previous usage and were configured for laptop batteries: 20 packs each of 6 cells in series with an overtemp switch and low-current connector. When I got them, the date code was for 6/2004, which I assume to be the date of manufacture. The packs measured from 1.6V to 6.8V, with most around 4.2V. So, apparently they had not been used in some time

These guys:
http://panasonic.com/industrial/includes/pdf/Panasonic_NiMH_HHR650D.pdf

I charged them at C/10 for about 14 hours each and then load tested them at C/4. To my surprise, out of 120 cells, only 2 were bad (shorted). Since then I have had one more cell fail shorted. All the other 117 cells still put out over 7AH at the low discharge rate. These seem to be tough little units.

I bought them for a lightweight, portable lighting project, so I have had no reason yet to pull more than 2A from them. I only use 24 at a time for the lights, and the rest have been sitting getting occasional top-off charges to keep them fresh. I charge them with a home-built 10-channel simple C/10 constant-current charger with a cheesy dial timer from the hardware store that I usually set to 12-14 hours.

But then recently I got some cheap motors and started an electric bike project and am pretty excited about getting to play with these cells some more. They seem very strong: Three packs of 6 cells were (subjectively) much stronger than 2 12V 8AH SLAs when playing with the motors and a bike wheel. In fact I broke my test mount with them. They really seem to flow a lot of amps. To be sure, proper fusing will be key for this project .

elblat said:

...
...
...

In fact I broke my test mount with them. They really seem to flow a lot of amps. ...

Click to expand...

You bet they do!

Check out this thread: https://www.endless-sphere.com/forums/viewtopic.php?f=14&t=12764&start=45#p280873

I don't recommend prolonged 100A testing any more, but they'll do it!

Mr. Mik said:

elblat said:

Check out this thread: https://www.endless-sphere.com/forums/viewtopic.php?f=14&t=12764&start=45#p280873

Click to expand...

Click to expand...

Nice work (and courage)! Op amps are pretty handy aren't they?

I forgot to mention that even at the C/10 charging rate it is pretty easy to see the -dV and feel the cells warm up, so I'm going to try an off-the-shelf Ni charger to see if it works. I tried a small one (<1A) but the long charge time overheated and killed it (it was only spec'ed to 2AH max so no surprises there)

elblat said:

I'm going to try an off-the-shelf Ni charger to see if it works.

Click to expand...

It works! This one:
http://www.all-battery.com/tenergynimhbatterycharger01017.aspx

Works great for a string of 40 of these cells (not super fast though).

I got a lot of 33 1st gen batteries about a month ago and purchased a super brain 989 analyser to test with.. so far after rehydrating the cells I have 4 that are up to original capacity and another 6 that are around 4500-5000 mAh and the cells increase with every cycle. I plan to start with a 10 module 72v pack for my bike and possibly an 89v 12 module pack depending how balanced I can get the cells. Its a slow process but looks very promising so far.

Does anyone think that it's possible to rehydrate cylindrical NiMH cells? I have some F-cell packs that have experienced overheating during charge, and probably lost electrolyte (or at least water from it). One of them I use only as a lighting pack now, because it's current output is way down from what it used to be (without major voltage sag), though I can still get most of it's capacity at a lower rate.

I doubt it unless you had a way to pierce the top or bottom and add some distilled water.. prob not enough airspace inside to even hold some additional water to reabsorb.. if you have a spare bad cell to experiment with try carefully opening it up to see its construction.. might give you an idea to its feasibility

amberwolf said:

Does anyone think that it's possible to rehydrate cylindrical NiMH cells? I have some F-cell packs that have experienced overheating during charge, and probably lost electrolyte (or at least water from it).

Click to expand...

Here is a very off the wall idea;
Some people store food in previously used glass jars that have a sealing surface on the lid. To do this they drill a very small hole in the lid and put a strip of black electrical tape over the hole. They then use a hypodermic needle to pierce the tape and connect a vacuum pump to the needle. When the needle is withdrawn, the tape will seal the hole, retaining the vacuum. I am thinking you might use the needle/vacuum with a "T" fitting. The spare leg connected to a valve (turned off) into a jug of water. Suck, turn off a valve on the vacuum line, open the valve on the water line and the water will get sucked into the cell
Any old fridge/freezer compressor will work as a vacuum pump. Just give it a shot of oil once in a while.

That's a thought....I have a dented cell I can experiment with, if I ever get the chance to do so.

any prius pack owners or the like tried a modified version of this simple zener shunt regulator for cell balancing? http://www.evdl.org/pages/hartregs.html

I have a couple designs in my head but the simplest would be to use a 8.2v 5w zener in series with a 0.5 ohm 1 watt resistor. The idea is that given the zener's voltage it can safely sink up to 600 mA current. I picked the resistance so that at 8.5v, the difference of 0.3v would net 600 mA of current shunt through the resistor... 0.3v / 0.5ohm = 0.6 A.

I'm just not sure how it would effect the charger's ability to detect dV. Guess a little experimenting is in order.

First post - I finally joined the forum mainly because of this thread...

I got two Lexus RX batteries recently yesterday butchered one of them to get nimh modules; want to reorganize them into 144V strings for my soon-to-be-build EV. These batteries contain newer cell modules, main difference is joining 8 cells in one ~1.5 kg package with smooth metal walls so you get 9.6V 6.5Ah nominal. Some specs can be found at http://www.peve.jp/e/hevkinzoku.html
After removing service plug which lowered voltage to still harmful 144V instead of 288 I opened the case, there're 30 modules inside joined mechanically in three blocks (12+8+12). Other useful parts are 3 contactors rated at 400V ???A, 125A fuse and probably a current sensor (still haven't dismantled relay box).
Modules are separated with finned plastic "sheets" allowing vertical airflow between them; these separators are also positioning whole block in metal chassis. Endplates are very solid, weighing ~2 kg each, they're joined with 16 metal stripes to keep cells compressed.
My plan is to have ~7kWh from 120 modules divided into 6 or 8 strings (196 or 144V depending on motor's capability) paralleled for drive and separated during charging. Since I have to build charger from scratch I thought on single buck converter feeding 6 or 8 PWM switches with independent control.
I know going LiPO route would be much easier with simplier charging, less cells = cheaper BMS etc. but unfortunately importing from China means 23% tax which I as a private person can't "creatively avoid"; Lexus batteries cost me in $100 range.
Let me know what you think...
Mike

Hello everyone, (almost) first post,
I recently got a Prius Battery Pack for a pretty good price (sad, they are hard to get here in austria). I've been demountig it for the whole day now (been laying around for 1 year, some screws were pretty hard to open). I measured only a voltage of 0.1V on each cell, so I am prepared for the worst.
View attachment 1
So far, i charged 2 pieces of em to 8.3V to test them out. After a minute of drawing 1A (current limited by power supply) they went down to 100mA over half an hour, and then charging constantly 100mA. For some first test with a 100Ohm resistor, the voltage didnt drop so much, so im planning on cycling them some times, before planning on anything with them.

I don't own some fancy battery charger, but using a lab power supply with current limiting and watching the cells should suffice to test them out?