Sv: Kjøpe elbil. Mars2010

[Elmo]

Kopiert herfra http://elbilforum.no/forum/index.php?topic=2380.msg19088#msg19088

Som jeg har nevnt her tidligere har jeg vært i kontakt med GP ang. deres 12V, 100Ah NiMH-blokker. Det lar seg gjøre å bygge om Think til disse, GP har sågar en ombygget Think gående i Hong Kong. Det er også like aktuelt for de franske bilene. Den originale laderen kan brukes, men må overstyres for stopp av ladingen. Batteriet må også integreres med kjølesystemet på et eller annet vis. GP er villige til å yte bistand, men de vil ikke ha med flere hundre privatpersoner å gjøre, så en eller flere personer må være frontfigur. GP foreslo et møte hvor kyndige personer fra elbilmiljøet ville få en teknisk gjennomgang av hva som kreves for å få til en fungerende konvertering.

Prisen som ble nevnt for en 120V pakke var USD 12000, hvilket inklusive mva blir ca NOK 85000.

Ti blokker á 12V veier 210 kg. De tåler 400A kontinuerlig belastning.

Dette syns jeg virker veldig interessant og vil gjerne være med på det.
Jeg er ikke veldig batterikyndig men jeg er opprinnelig svaksstrømsingeniør og har i tillegg  relativt god oversikt over mekanikken i PSAene.

[BauDemo]

I think this is very interesting... but:
- operating temperature range
- charging temperature range

Are we talking about these?
http://www.evbtech.com/Data%20Sheet/TDS%2010GP100EVH.pdf

And why not any of the cheap Li-chemistry?

[Ken]

I think these are the modules we are talking about.
In many ways are these better suited to a Nordic climate than lithium although they are not as robust as NiCds i suspect. The operating temperature range is not as high or as low but they tolerate freezing better than lithium. The charging parameters are similar to NiCds and haven``t the same requirement for invidual cell voltage management.

[eledille]

BauDemo:

Operating temp: Don't know, but they need cooling.

Charging temp: Charge cutoff can be done by monitoring temperature. They're full when temperature reaches 45 deg C. A temperature sensor for each block can be used to generate a signal to cut power to the charger. GP has got kits to do this. Equalization can be a problem, cells are equalized by charging at a low rate - full cells will produce heat. If this is necessary, then a second, smaller charger might be needed.

Some of the point of using NiMH is that one might not have to replace as much of the electronics, and as Ken points out, they don't need as much management. In principle, you charge at high constant current until the first cell reaches 45 deg C, then charge at 2A for a certain amount of time. NiMH is also a "tried and true" and very robust technology. They are also maintenance free.

[BauDemo]

I was not really concerned about cooling... if you look at charge and operating temperature range you will see that the lower limit is 0 and 10C ... I think this is worse than the spec from the LiFeYPO4 TS cells.
Again I have only looked at the spec sheet, and have experience with neither the GP nor the TS cells.
So what are we going to do when we need to charge the car in close to 0 temperatures?

On a side note - the Panasonic cells in the RAV4 are absolutelly amazing, so is this temperature thing just a spec sheet hickup, or maybe GP can wigle the formula and make them usable in close to 0 temps?

[eledille]

The reason to use these batteries is that I hope that this might be cheaper in total, if no or almost no BMS is needed, the original charger can be used and integration is easier. NiMH is also known to yield at least 200k km lifetime in the RAV4 EV.

If this is not the case, then clearly lithium is better.

But the last price I heard for a Lithium conversion was on the order of 200k NOK, which I simply am not prepared to spend on such an old and unsupported car. Then I'll wait for a MiEV or Leaf or buy a Tesla Roadster instead.

BTW, I can't get PMs to work right now, I'm getting an error message about a misconfigured server.

[eledille]

BauDemo: We will have to ask GP about that, but I can't see why GP cells would be significantly worse than Panasonic's - GP is a well respected manufacturer. This was not mentioned as a potential problem when I talked to the GP guy.

[Elmo]

Suddenly we are all English now - but OK with me 

I think there are three very good reasons to start this "project"

1) real help/participation from the manufacturer (unlike most projects I have seen)
2) relatively low price (also comparred to many projects I have seen)
3) relatively low risk. We can stop the project at any time if we dont get sufficient answers from GP to all the very good questions that has already started to come up

[El rayo]

I was not really concerned about cooling

All Th!nk BMS logs that I have checked have exceeded the max temperature for NiMH, 45 degrees. We may have to install a separate cooling cirquit for the battery. Air cooling is probably the easiest for Th!nk and sufficient for Nordic summers.

So what are we going to do when we need to charge the car in close to 0 temperatures?

Probably nothing as long as outside temperature stays above -10 degrees. With outside temperature down to -19 degrees, my Th!nk reached -7 degrees battery temperature. NiMH may behave differently concerning heating up during charging and use. For lower tempertures, I suggest installing domestic floor heating elements, activated while charging. Idea "stolen" from Kewet and Reva.

On a side note - the Panasonic cells in the RAV4 are absolutelly amazing, so is this temperature thing just a spec sheet hickup, or maybe GP can wigle the formula and make them usable in close to 0 temps?

If my memory serves me right the Rav4 EV has an air conditioning unit for the battery pack.

[BauDemo]

If my memory serves me right the Rav4 EV has an air conditioning unit for the battery pack.

This is common misconception - the RAV4 EV uses ambient air to cool the battery pack.
Maybe you are thinking of the Ranger EV or GM S-10E - I think these two were using air-conditioning (heat pump?) to cool the pack.

[BauDemo]

Suddenly we are all English now - but OK with me 

Please feel free to use Norwegian - I can manage to read, but don't ask me to write in it.

I think there are three very good reasons to start this "project"

1) real help/participation from the manufacturer (unlike most projects I have seen)
2) relatively low price (also comparred to many projects I have seen)
3) relatively low risk. We can stop the project at any time if we dont get sufficient answers from GP to all the very good questions that has already started to come up

These are very good reasons! And very good initiative!
I am very excited to see what will GP respond, and what would they recommend for managing, and protection of their batteries. Also it will be interesting to know what they are using as separators, and plate materials.
As with the Li- chemistry, not all NiMH are born equal, and GP as a big company is a good choice for a partner to try and figure out conversion/upgrade.

[elektrolux]

NiMh are not wery well suited for rapid charging.

But then again Think newer provided rapid charging output anyway.

[BauDemo]

NiMh are not wery well suited for rapid charging.

This is not entirely accurate.
I don't know what your idea of rapid charging is, or how is suitability measured, but the conductive RAV4 EV had a quick charge port that allowed for charging the pack up to 80% in less than 45 min.
It requires an external DC source capable of approx. 25KW output.

This is not the 15min charge that a lot of magazines are talking about, but it is still quite quick for me.

Also - as I said earlier - similar to Li, not all NiMH batteries are created equal.

[El rayo]

It's important that we speak the same language, so here is the definition of slow, quick and fast charging, courtesy of http://www.batteryuniversity.com/partone-11.htm

    * Slow Charger - Also known as 'overnight charger', the slow charger applies a fixed charge of about 0.1C* (one-tenth of the rated capacity) for as long as the battery is connected. Charge time is 14-16 hours. Slow chargers are found in cord-less phones, portable CD players and other consumer goods.
    * Quick Charger - Also knows as rapid charger, this charger serves the middle range, both in terms of charging time and price. Charging time is 3-6 hours. The charger switches the battery to trickle charge when ready. Quick-chargers are used for cell phones, laptops and camcorders.
    * Fast Charger - Designed for nickel-based battery, the fast charger fills a pack in about one hour. Fast charging is preferred because of reduced crystalline formation (memory). Accurate full-charge detection is important. When full, the charger switches to topping and then trickle charge. Fast chargers are used for industrial devices such as two-way radios, medical devices and power tools.

[Ken]

But we are speaking the same language, english!

This forum would be quite different if it was conducted in english. Many more would contribute to what is regarded as a good technical forum. Many are envious of our ElbilWiki, but the norwegian language makes it impossible for most. I think that the level of activity is OK and means that we don``t have to use all of our free time to keep up to date.