Prius battery to power e-bike?

Well, a Prius cant go real far on them! I think only 10 miles, maybe less! It was designed to start up and drive low speed until the gas motor is needed.
otherDoc
 
I'm pretty sure that's a 1st gen battery - supposed to have some tendency to problems but I can't remember what. The one I have is 2nd gen and may be preferred. Gen 1 had 38 cells, Gen 2 has 28.
z.
 
on my prius cells it's going to be a much simpler rig - same kind of charging using kensingtons and time. From watching the voltmeter I'm feeling pretty good about 1.4v / cell max charging. I don't think the Prius cells are designed for 1.7v given how slow the charge goes once you get to 1.3v or so. No need to tap anything since the there are so few cells and the bolts are right there. Purists may choke at my discounting the last bits / neg. delta v etc., but I don't seen any reason to try and squeeze every drop out of these batteries for my application.
Click to expand...

Just trying to get this method clear in my head. I will be using 7 prius modules at 7.2 volts each to make a 50.4v pack.

This pack when charged will be around 56v or around 1.33v per cell. With your method you just shut of the charger at 1.4volts per cell or 8.4v measured at the end tabs of each module and how many amps do you charge at given that you only charge for 1hr or is it just because you charge after a short ride ?

What voltage will your charger output I am guessing around 56v for the 7 module pack?

I have a prius battery and I am keen to charge it and try it out but all i have is a 1.8ah 48v sla smart charger with a unloaded output voltage of 56v .Can I make do with this some how?

Kurt.
 
It's a second generation battery, from an NHW11. The first generation (the NHW10) was out of production long before 2002 plus was RHD, JDM only, although there are some grey imports here in the UK. Third generation (the current model) is the NHW20. Both first and second gen models used the 38 module pack with no voltage doubler, the current model uses the 28 module pack but uses a voltage doubler in the newer HSD II control system to give increased electric motor power.

The current (NHW20) model Prius has an electric only range of just a couple of km or so in practice, and has to be kept below about 28mph even to achieve this (over 28mph and the ICE starts, even when EV mode is selected). This isn't surprising, as the battery pack only has a usable Wh capacity of about 525Wh even when fully charged (it's limited to a low max discharge/charge depth by the BMS).

The second generation battery did have sealing problems, leading to water getting in and corroding contacts. Most packs should have had a service recall by Toyota to fix the problem by now.

Jeremy
 
One thing I can tell you about the prius battery's is if you are going to use them you will need some way of compressing them that is very very strong. You will need to use steel!!!for both charging and discharging they want to vent that gass and the side walls are very week to the point where they will just blow them selves apart. I cant see how anyone is using these bats on there own without clamping. If so I would like to know how you haven't blown the cells up from the pressure build up.

from my tests so fare the battery's seem kinda average at best. they don't seem to like high discharge. I tried going up some big hills at 33amp draw and they didn't like it very much.

looks like its back to the old sla pack for a while.
 
Interesting stuff, Kurt. I wonder why you're getting such low discharge capability from your cells? In the car these cells deliver very high currents, well over 100 amps, day in and day out for years. The cells don't gas either, in fact they are connected to the passenger compartment by their air venting system (primarily to keep the cells warm in winter), so if they did vent there would be a chance for fumes to find their way inside the car (although there is a temperature controlled fan that should keep the air going the other way).

The 2nd gen NHW11 Prius, for example, has a peak electric motor power of 33kW. which equates to a current from the 270V battery of around 120 amps. The newer 3rd gen Prius, the NHW20, draws more than double this current from it's battery pack, as it has a bigger set of electric motors and a lower voltage battery.

Jeremy
 
I am not sure if they get to the stage of venting but there is a pressure buildup in the cells for sure thats why they are bolted and clamped so well in the steel frame they come in. There are a couple of examples in the web of people charging them at just 5amps without clamping and the battery's have expanded.So they are very delicate when not clamped. Even when charging at just 1.8amps you can hear some very slight fizzing going on after about 5 mins of charging.

Tonday I ran them flat to around 1v each cell and charged them at 1.8 amps with clamps to stop them swelling. i also monitored the temperature and cut the charger when it reached 40 deg c . They charged for a little under 3hrs before the temp was reached.

I havn't taken them for a ride yet. The first time i charged them I only gave them 1hr of charge at 1.8 amps so they didn't have much charge in them i think i get about 2km from them i did go up some steep hills.

The 120 amps the prius pulls from the pack how long dose it pull this for as I am interested to know what the continues rating is for the pruis cells?
 
Bummer Kurt. I've no problems running a 7 module pack flat out and fast charging it. Not a hint of warmth, or swelling, tons of power - as much as my A123's....mine are more recent vintage with aluminized sides on each module.
 
My direct experience is with the NHW20 Prius, the 3rd gen one with the lower voltage, higher current, pack (50kW motor, rather than the 33kW motor in the 2nd gen cars).

The Prius will pull maximum power from the electric motor, for example when going up a steep hill, until either the battery SOC drops to 40% or the battery temperature exceeds it's safe limit. There are also a couple of other safety cut-outs that might possibly kick in, like the MG2 winding temperature or the HSDII inverter temp spiking, but I've never once heard of either of these events occurring under normal conditions. In practice MG2 rarely runs at full power for more than 15 to 20 seconds, as the car accelerates pretty well and reaches 60mph in around 10 seconds.

I've found that the NHW20 battery will happily deliver around 200 amps for perhaps a minute, although I've not really driven in terrain where I've been able to push full power for that long. What's more impressive is the way that the battery accepts massive charge rates; it quite happily soaks up 50 to 100 amps or more during regenerative braking. Only once have I ever caused the car to switch from regen to friction brakes on a downhill section and that was when descending a steep mountain pass in the South of France; after a few minutes the battery SOC was showing full and the brakes switched over (there's a very distinct change in brake pedal feel when this happens). Most of the time the friction brakes only kick in at low speed - at 50,000 miles my front disc pads were only 30% worn, indicating that the pads would easily do more than 100,000 miles as regen is the main form of braking.

Jeremy
 
I've run a number of empirical tests on my generation 2 or 3 cells and would share a couple of personal observations with them. First, I think it's important to state they are all from the same car, only 2 or 3 years old, and arrived at my door at 7.4v each cell. I have no reason to think they aren't in good shape to begin with. I have 7 cells in series, for a nominal 51.8v and have additional taps at the 5th cell for 36v.

I did this because a) 51.8v is cool on a hub motor (my wifes - now much more fun for me) and way too scary for me on my mid-engine through-the-gears rig. I confirmed that today for fun - I had to brake not to hit the SUV in front of me. My guess is around 40 mph - you guys in the 50 mph club are nuts. I'm not doing that again anytime soon. The ability of Prius cells to deliver amps is fantastic, there was a ton of power in 8th gear of my Sturmey - that is a very tall gear - at least for me. My controller is a PowerPak and it got warm for the first time in it's life. I'll be using the 36v taps to get to work tomorrow...

My charging rig is temporary, and consists of a 16v, 4.5A IBM notebook charger putting out 16.65v on the last 2 cells in the string (8.3v/cell), and a soneil 36v, 1A SLA charger putting out 42.3v on the 5 cells (8.6v/cell).

I'm watching cell voltages like crazy, and it's pretty consistent - at just over 8.3v there's the slightest sound from the vent hole when I put my ear to it (gas?). No warmth (no shock either)

Here's the interesting part to me; the IBM charged cells don't make the sound and seem to have no problems. As expected, they get up to 8.29v within the hour, and stays there. The IBM adapter cools down as it approaches final voltage. The 2 cells do not get warm.

The 5 cells on the 1A soneil get to 8.29v within 90 minutes or so but I've taken to stopping it since I can hear the sound from the vent when it gets over 8.3v.

My initial conclusion from these simple observations is that fast charging at higher amps isn't so much the problem, as is overvolting. I'm leaning towards 7 individual chargers for the cells, either DC converters or modified kensington adapters.
z.
 
It's worth remembering that the Prius never fully charges the batteries, it takes them to 80% and no more under normal conditions. It may be that the cells are optimised for this sort of operating regime and so don't tolerate being fully charged well.

I've no idea if this is actually the reason for the cells venting, but it seems possible.

Jeremy
 
Jeremy, I haven't had much luck deciphering what little technical info I've found on the prius cells, some of the more detailed sites I found are still pretty slim...

http://www.99mpg.com/resources/articlesandblogs/batterypacksexpose/

http://hiwaay.net/~bzwilson/prius/pri_batt.html - this fellow has a charge graph but was charging over 8.5v and had gassing. I'm not surprised by what I can hear at > 8.3v.

So far in practical terms, I find no reason to push the charge voltage on these (if that's the problem), but I also don't see a problem with 4.5 amps (I'll be upping that to 8 amps shortly with my trusty kensingtons) Charging the pack with 8.3v at 4.5 amps (to just under 8.3v) takes about an hour. The result is this 6.5AH 36v Prius pack takes me to work and back with a lot more power and reserver than the two tenergy packs (3.8 and 4.2 AH 36v).
 
Interesting point on the voltage, could be part of the problem I am having with my cells. I haven't given up on the prius battery's the car mine came from had only 20,000km on the clock but I think the pack had been sitting for a while in the savage yard and the voltage had dropped on the cells. They did take to a charge well and the voltage soon came up.

I was supplying them with a little more voltage than the battery's needed when charging but at only 1.8 amps and I found that after 30 min or so some slight gassing sounds were coming from the packs so I always had to pull the plug early on the packs as the voltage on each module got to 8.3v quickly. So when taking them for a ride I only got a couple of km out of them.

my plan now is to try charging them at just the voltage they need but at 2.2ah and stop at 8.3v hopefully this gives them more time to soak up the amp hrs before reaching 8.3v.The way see it is if the battery's are rated at 6.5ah then when flat they should at least take 5ah worth of charge or 2.5hrs of my 2.2ah charger before reaching 8.3v or gassing.I thought i read some where that nimh battery's need 120% of there ah rating to be fully charged as they are not 100% officiant at taking a charge ? . The second thing I am going to do is cycle the battery's a number of times to see if that brings there range up a little.

From what I have read the plastic packs like I have are the 2nd gen and the metal sided packs are from the 1st gen from jap. i can see in the links that a lot of people have over charged them and some have swelled up like they are going to pop.I wonder if they tried to over voltage on them ?

I just cant give up on the 5 beautiful neat 50v packs in my garage with out a fight.
 
Good luck Kurt - from your description the cells sound over volted and under charged. I've pretty much set LiFeP04 aside since I can buy a 36v pack of these (5 cells / 6.5 ah) for under $150 that bolts together...Criminy....what am I missing? That's at least as good as 3 dewalts - and I truly don't see the dewalts as having a better charge / discharge curve.

Longevity will be largely determined by the user I suspect, but as long as the charging is worked out, I think these are very tough cells to beat.
 
I share your view about these cells being long lived, provided that they are charged/discharged in a way similar to that in the Prius. I think the key thing might be to find out the best way to charge them without risking them venting, which may mean looking at an unconventional (by NiMH standards) charge profile. The Prius does some pretty complex stuff to measure charge in, and discharge out, of the pack, combined with sub-pack voltage monitoring. It may be that doing something like using a Watts Up to record discharge and charge might be good enough. What would be neater would be to make a simple BMS, using a cheap microcontroller to measure discharge and also control charge. This would then automate the process and ensure that the cells were never over-charged.

I'm guessing, from what's been posted so far, that these cells don't exhibit the classic NiMH "peak and dip" terminal voltage when fully charged. If so, this ties in well with what seems to be happening. Maybe Toyota got Matsushita to change the cell chemistry by reducing the capability to recombine hydrogen at the end of charge. I don't know why they may have done this, but perhaps it was a trade off that gives longer cycle life in some way.

Jeremy
 
Just got home after a 5 cell (36v) round trip to work on my summer ride (mid-engine-through-the-gears). Extremely satisfying with the ability to accelerate in any gear, even going uphill. I think I'm forming a few (no watt-meter type) conclusions of my own. I've summarized them as follows;

The cells
1. deliver all the power of an A123 pack (again, I have several). IMHO
2. may not have a charge profile like standard NiMH. IMHO
3. respond well to cv-cc charging to 8.3v at 4.5A IMHO
4. tend to swell when overcharged, but not when discharged IMHO
5. have a sudden drop in performance when depleted - however the resting cell voltage remains over 7v

We all know the cells are normally not cycled to their extremes, and we would all place a bet that such activity will shorten cell life.

I'll add I have seen reason to believe they are somewhat tolerant of "overcharging" if kept no higher than 8.3v - I'll test this voltage a bit more. I'll use a stethescope at the vent and mark when I first hear something and map that to cell voltage - but I don't really know how significant the sound is at any given voltage, but my gut tells me it is significant.

Where I think this is going is that for a commuter like me, with a set ride each day, it's fairly safe to used a timed charge (cheapo wall timer) at 8.3v based on charger amps (ie// 1.5 hours for a 4.5A charger - I did this for over a year with my A123's and never had a problem. They were also reasonably tolerant of prolonged charge times. I think current flow into the battery slows as the voltage of the charger and cells equalize, but that will have to wait for my replacement meter.

For folks unfamiliar with the idea, it's based on knowing the ride will take somewhere around 80 - to 90% of the battery. Putting that back at a moderate amperage and conservative voltage, even if overestimating the charge time by 10 - 20% is not likely to cause much pain. I may not squeak out every watt, but it doesn't matter in this application.
 
Thanks for the info powermed. I know I haven't posted anything in this thread for a while but as my luck would have it one of my friends came through and gave me a prius battery that was about to be thrown out. I unfortuantely wont be able to post much info for a few weeks since I can't do anything physical as per my doctor. However I am already wondering if my bike can hold 36v 24hr. For now I will dream on till I can do it.
 
I have been playing around with different chargers trying to find something that will charge the packs without over volting them.
what I am finding hard to measure is the unloaded voltage vs the loaded charging voltage. Some transformers state 12v 500ma but if you place a meter on them unloaded they cum up with 16v even a charger for a makita cordless drill that is 7.2v reads around 12v unloaded.

So I am not sure how you get an accurate reading on what the loaded voltage is of a charger as it changes depending on what battery you connect to it and what state of charge the battery is in . I have a charger that is for a 6v 4.5ah sla battery the transformer has 9v 500ma on it but unloaded its more like 12v. I tried connecting that to one 7.2v module and the voltage slowly went up to around 8.2v and is slowly coming up .

It sounds like even a 36v nimh charger will over volt the packs before you can fully charge them.

I did try my 48v sla charger on 7 battery's but what I found is that the charger stopped when the voltage was reached for a charged 48v sla and because this is less than 58v the battery's were under charged. i tried 6 cells but i think they charged for longer before the charger stopped but by this time they were being over volted.
 
Someone jump on me if I'm wrong, but unloaded voltage should be the one that counts Kurt, that is if the charger has a constant current (CC) output. Most chargers do for the bulk of their charge cycle.

I'd be wary of most SLA chargers unless they are of known high quality such as a soneil - they even publish their charge profile. Most NiMH chargers (I think) start out with a "soft" high voltage and then come down to deliver the amps.

Modern notebook power adapters are typically constant current / constant voltage output switchers and should work quite well. I've found their stated output varies about 10% to the upside. Using 8.3v as a goal, that means you should find plenty of 16v notebook power adapters that would work for 2 cells in series. 3 matching ones would do it for a 6 cell pack, odd number of cell packs present a challenge.

About 2 years back I figured out how to take advantage of kensington notebook adapters with the smart tips - there's a couple of snips and 2 trim pots to setup - but then you've got a completely adjustable AC - DC converter, adj. voltage and current to your heart's content. I use them a lot, and i'm settling on 3 for my 7 string pack; 2 adjusted to 16.6v and a third adjusted to 24.9v - I'll start out with them all at 4.5A but I'll be testing them up to 6A to see if I can't just charge for an hour and be done with it. I think that will be no problem.
 
I was thinking the idea of using a laptop charger is starting to seem like a good idea. I have been looking at the IBM 16v 4.5 amp chargers.
looks like you can pick them up for about $10 on ebay.Thinking 4 of them charging 2 battery's each would be fine. I was interested in the trim pot modifications to make them adjustable?

Would be nice to be able to fine tune them to exactly 16.6v and dial in the amps

oh,I also noticed the sudden drop in performance of the battery's when depleted and found it funny that the voltage was still in the over 7 volts.
 
I went to an electric bike shop and asked them about charging the prius battery cells. Although they haven't played with them the guy said that using a 36v 4amp NiMh charger would most likely work. Has anyone tried that? I guess his thinking for it was 5 cells @ 7.2v = 36v

I am going to start looking at taking my prius battery apart early next week and try to do some light testing.
 
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