charging Prius battery (8 cells)

[francoisboivin]

Hi,

I came across a free used prius battery (1st gen) and I want to extract 7 or 8 cells for my trike.

I've been looking around a little bit but can't figure out the right way to charge it. Anyone has experience with this?

Thanks!

 

[Monstarr]

Yes, more than enough information available if you search for it.

Each prius prismatic module contains 6 seperate NiMh cells of 1,2 V nominal in series. So each module is 6S.
These were the 'volt/ampera/leaf' scrap cells for the cost driven DIY'er of 3-4 years ago .
Energy density low but they can deliver.

Charging NiMH is tricky though as they do not really have the typical type charging curve of li-ion/pb.
The full charge state is, what i remember, measured at a sudden change in temperature (delta T).
The modules also need to be compressed.

Free recycling available through your local Toyota dealer

 

[francoisboivin]

yes I've been reading quite a lot but the part I'm having a hard time getting info is: When exactly do I stop charging.

in this thread ( https://endless-sphere.com/forums/viewtopic.php?f=14&t=6726 ), he seems to be only charging them at 8.3v and basta.

Others I've seen uses the same approach but with a timer

Then there's also people that count the Wh spent and refuel the cell with the same amount.

But pretty much all thoses thread are a few years old, maybe somebody found a different way

So for I'm planning to go for the third approach with an arduino to count and regulate the Wh spent/charged. I would then use a 16.65V laptop charger to charge 2 cells at the time and with the arduino I could make the power go from 2-cell-group to the other when the charge is done. Or cycle it more often so the cells stays balanced if i need to remove the charger before the end of the cycle.

I was also wondering if bulk charging if alright with thoses battery. It would be easier to manage.

Thanks!

 

[francoisboivin]

Yes I understand the dV or dT part but it seems that nobody is able to detect them and no available charger can.


What do you use for charger?

 

[amberwolf]

I guess I never read anything about the Prius cells not working as normal NiMH for end-of-charge, so I can't help with that--if the info isn't in the threads about them then you might have to expand your reading to the rest of the web to see if the answer is out there.

I dont' have the chargers I used back then anymore (lost in an unrelated house fire or the cleanup afterward), and I never had any Prius cells to try them on, just regular NiMH and NiCd cells in E and F sizes, from ebike packs that had already seen better days before I got them. I do still ahve the packs, I think, but they haven't been touched since then.

I think 2 of them were "hi-power"; they might have been the most sophisticated, but I am not sure. Then there was a Tenergy, for small packs. I think there was one more but I can't remember.

RC Chargers often will do NiXX as well, but quality of those varies a lot. I have a couple of Accucel6 units that can do it but I have never tried.

I also have a Grin Tech Cycle Satiator that can do NiXX, but I've only so far used it on an old worn-out Crystalyte pack (there's a thread about it if you look up threads by me with NiXX in the title; since I didn't know if it's NiMH or NiCd). Since it has so many bad cells, I haven't been able to safely test true end-of-charge conditions, until I remove those bad cells and reconnect the rest as a lower-voltage series pack.

 

[Hillhater]

As AW has said, many of the RC chargers have a NmHi setting for charging cells in series ( not recommended to charge in parallel)
But, A problem may be finding a suitable RC charger for your pack voltage .(.6x8x1.2= 57.6 v..?)

 

[Doctorbass]

Hi,

I came across a free used prius battery (1st gen) and I want to extract 7 or 8 cells for my trike.

I've been looking around a little bit but can't figure out the right way to charge it. Anyone has experience with this?

Thanks!

François, your name look like french canadian, if so i can say that if you live in Quebec province, i would suggest you a better option for cheap than these heavy NiMh cells

Contact the president of ELMEC( they produce charge stations for EV) at Grand mère near Trois-Rivière, he is selling Leaf modules for 60$ each.. these are like new and come from a 2014 or 2015 Leaf. that's way mre energy and is simple method for connecting these and charging these! These modules are already 7.4V 60Ah.
I can give you his contact, just PM me

Doc

 

[francoisboivin]

Amberwolf, i've read this on many article. here's an exemple ( http://www.gpsy.com/ev/2012/01/charging-prius-packs.html )

Smart chargers can't detect Prius delta-T/V
NiMH batteries are tricky to charge as there isn't a fixed final voltage as with LiIon/LiPo/Lead-acid. Instead, smart chargers usually look for a very small drop in voltage (delta-V) which signals the cell is full; or an increase in cell temperature (delta-T).

Unfortunately, Prius packs don't exhibit a measurable drop in voltage and don't increase in temperature when they are full. This is partly because of their pack design (prismatic rather than cylindrical). Instead, when a Prius pack is full, it bulges due to the increased internal pressure.

or
https://endless-sphere.com/forums/viewtopic.php?f=14&t=6726

Do not even bother trying to charge them with a standard commercial NiMH charger. I have found no NiMH charger that can charge them safely - they all miss the delta V

and
http://www.mpoweruk.com/chargers.htm

I do have an RC charger (imax b6) for my 18650 batteries but it's appenrently non-suited for prius cell.

Right now I am thinking to aim for 0.1volts under full charge voltage. I would then avoid the overcharge situation but the capacity would be less...

Doctorbass:
if I had knew a few weeks ago it would have been great but all my battery-budget went into the 18650 pack i'm building in parralel. I had the prius cell for free so I'm looking for an use to them. Merci quand même pour la suggestion!

 

[Monstarr]

I once used a 40s NiMH Tenergy charger for my 42s (7-block) NiMH 'Prius' battery.
http://www.all-battery.com/48vsmartuniversalchargerfor40-cellbatterypack1a.aspx
Mine had 2A current though.

This way it provided a fairly large safety area (and all-battery didnt sell NiMH chargers with higher cell count :lol
It cut off charge all the time when it was 'full'. But I highly doubt I used these modules to their near full capacity this way.

The whole Prius pack (3th gen = 200V6,5A) has 1.3 kWh of theorical energy capacity. The hybrid system uses only half of it, to increase longevity.
My experience is that they are not really usuable in small bikes and scooters. They are way too bulky and charge sensitive to be useful. And they need to be compressed decently.
There are better alternatives.

 

[francoisboivin]

Thanks Monstarr for the link, i'll look into that.

I do have a lot a space on my trike. There was two lead batteries there before.

As said here, a 2A charge on a 6.5Ahrs would not be sufficient to trigger the dV or dT so stopping before full charge isn't an option:

http://batteryuniversity.com/learn/article/charging_nickel_metal_hydride

It is difficult, if not impossible, to slow-charge a NiMH battery. At a C rate of 0.1 to 0.3C, the voltage and temperature profiles do not exhibit defined characteristics to trigger full-charge detection and the charger must depend on a timer.

Again, I have been given a dead battery for free so I might try to see what can I do whith the cells that are still good, or I'll test and sell the good ones to buy more lithium batteries