Electric battery Earn £175 per month from your EV!
BMW i3 wrapped in adverts

Helleo from Kent

I saw ads on the Twizy and started making inquiries with the Maidstone Renault dealer (DUH), started telling me all manner of Buffelsheiser, and stopped short when I asked him about insurance.

So I decided to do my homework as you should and have become intrigued, I want one BUT 2nd hand end of its battery contract will pay up to 2k (Well that will raise hackles no doubt but look what the trade says?)

Anyway, on big gripe is the ongoing cost of batteries - £2700 outrageous.

I am a retired professional engineer. Ive has a lot of experience with owning Ebikes and mobility scooters, so I may have some new thoughts on the problem. Ebikers (and to a much lesser extent mobscoots) have much community knowledge on tweaking their kit and avoiding extortionate dealer charges.

A quick look on Ebay and you can get 18685s Lions 5Ah 3.7V for ca £1 thats 18.5 Wh, so 300 of these are needed to give the nominal 6.1kWh for a Twizy £300

But its not that simple of course, you have to deal with charging correctly and safely - but its all out there. Ebikers do this all the time

But I stress this is not for amateurs, Lions are dangerous, firehazard and explosive - look at the Dreamliner. Remember how some mobile phone exploded causing injury cos they had been fitted with cheap chinese kit without the all important charge regulator chip.

This was a quick take on my part and needs much more research, but it shows how much you are being ripped off

I am about to replace my Ebike battery pack with a home made one (£400 from maker now £40 to my design). So I will prove the concept.

But its all there on Google

If any skilled member (in electrics) wishes to collaborate on the development of such fixes pls pm me

Hope I can help

OBTW pls advise if this board is in any way compromised by Dealers who obviously wouldnt appreciate my input, I may have to go underground

Robin

Robin,

No such worries there. This board operates freely. There are no rules other than try to be nice to each other and post in the correct categories. That’s about it.

So go ahead, I look forward to seeing what you can come up with!

Robin Welcome.

I as will many other be very interested in this project. The for you will be getting hold of a Twizy for that money as the price has began to stable out a bit. The second problem is there are None without batteries. Most Twizy owners took out the cheapest rate at the time which was for 3 years. They will not be for sale for another 12 months. Then they will be sold with the battery as the owner has to pay to get it removed.

The first place to start the research will be on the German Twizy forum as they were ahead on a number of Mods and they have owned Twizys for longer than any one in the UK and in greater numbers. That is where alternative batteries will be considered first.

As you say the problem will be around the charging and this may need a completely separate charger. The cost and placing within the Twizy will be tricky, as leaving it external will remove some of the flexibility of where you can charge. Also the loss of the regenerative power. There is a lot of power in that sized battery pack and the wiring will be complex when using such small units.

You may also find that the existing charger can be changed - It was mentioned on here that by tricking it into thinking it is very cold the charge rate drops.

Sounds like you the right man for the job and possibly have a lot more time than I. Keep us (or me) in formed with progress.
Good luck.

A bit more for you on the battery as it stands.
The battery pack of the Twizy consists of 42 cells, arranged in 7 modules of 6 cells each. Within a
module, cells are layed out 2S3P, that means there’s a total series of 14 packs of 3 parallel cells
each. Cell chemistry is supposed to be LiMn based, so each cell has a theoretical voltage range of
about 2,5 - 4,3 V, nominal voltage around 3,6-3,7 V. Renault restricts the usable SOC window to
maximize battery cycle life. Charging top voltage is 57,7 V for the pack = 4,12 V per cell.

Poor pic from Video.

That would be an exciting breakthrough, though as you say setting up the charging system and packaging the cells will add quite a bit to the cost. I’m afraid I don’t know enough about batteries to say, but the generally talked-about figure for Lithium batteries for EV’s seems to be between $350 and $500 per kWh, which is about what the Twizy batteries come to. So if with $500 raw materials and about the same again, say, for packaging you could replace the Twizy batteries for, say, $1000 I’m definitely in!

Prices are coming down, and according to this ](http://green.autoblog.com/2013/11/08/li-ion-battery-prices-headed--down-180-kwh/)we can hope for under $200 per kWh by the end of the decade. As the article says, that will bring EV running costs down to below current ICE costs, because as the EV community tends to overlook, batteries are the most costly consumable for an electric car - the cost of the electricity isn’t (at the moment) very significant (unless you buy it from a rapid charge point, which Twizy owners can’t!).

Hi everyone! My name is Johnny and I live in Gothenburg, Sweden. I have a Twizy on order, but will not get it until August or something… I have quite long experience in electric vehicles and have converted 2 different ICE cars to electric and right now I have just started converting a Yamaha Majesty 250cc scooter. There are quite a few issues involved in building a new pack for the Twizy. I prefer using prismatic LiFePo4 cells (nominal voltage 3,2V) in my packs because you can use single larger cells in series and don’t have to put alot of smaller cells in parallell, this making it easier to have control of the pack, they also have a much longer life span than the smaller LiPo-cells. When it comes to the Twizy, it has a BMS (Battery Management System) that communicates with what? Controller or central computer? Propably via Canbus. This is a thing that needs to be researched, a BMS is also needed for the new pack. Regarding Ebay cells, don’t believe the stated Ah, especially if the seller is from China, if you get half the stated capacity you should be happy :slight_smile: , the quality is a different issue… I have built a 18650-pack for my e-bike with Samsung 3Ah cells (4p10s) and those where around 5$/pcs + import tax, these are good quality cells.

Thanx for the pic, I think Ive seen the same video about how the Twizy is made in spain - “not a robot in sight” says the commentator. A curious kind of boast. Did you notice how the chassis was made, didnt look zinc plated like modern car bodies? Wonder what corrosion protection would be then?

Looks like that battery pack is installed from underneath, so a vehicle hoist would be needed for sensible access. Any idea what the battery pack weighs?

FYI My Mini crosser chariot has 2 x 120Ah 12v deep cycle batteries (cost £250 to replace) and they weigh 80kgs and hold 2.3 kWh of useable energy, so to get 6kWh I would need 3 such packs weighing 240kg but only £750 to replace and with at least 5 years of sensible use and 1000’s of charge cycles - not that Im suggesting, but just to keep a perspective.

Hi J

Thanx for your input, agree 100% Chinese imports must alway be suspect and double checked very carefully. I got some LED lamps from them, supposed to have a life of 25 years, failed unexpectedly after 3 months - that says it all. They sell, on Ebay, all their substandard off spec stuff from their production runs which would normally be scrapped. Been there done that. Certainly it will be a major task to put a new battery pack in a Twizy but thats what R uk’s policy is encouraging.
The BMS is of paramount importance or you might end up with a fire or explosion. Even Boeing didnt get it right.

A lot of info on http://www.openvehicles.com/, but the site seems to have gone dead - anyone any info?
also https://github.com/openvehicles/Open-Vehicle-Monitoring-System/tree/master/docs

and the useful manual

https://github.com/openvehicles/Open-Vehicle-Monitoring-System/blob/master/docs/OVMS-UserGuide-RenaultTwizy.pdf

nb hit “view raw”

Please keep board informed of progress/info.

cheers

Robin

The good thing about LiFePo4 is that it’s a much safer chemistry than Li-Po and similar and don’t burst in to flames or explodes when abused. But you still you need the BMS to keep the voltages within limits or the batteries can get ruined. If you buy from a good manufacturer they match all the cells in the pack for you and sometimes only an alerting Battery Monitoring System is needed. The disadvantage with this chemistry is a slightly lower power density, takes up a little bit more space. F.ex. 16 of these in series http://www.ev-power.eu/Winston-40Ah-200Ah/WB-LYP160AHA-LiFeYPO4-3-2V-160Ah.html would give you the right voltage, 8,2kWh and would weigh 93kg. Anyone know the size of the battery box in the Twizy?

Thanx for that, I am clearly out of date with that latest technology - looks significantly improved on LiPos - so place my order for august production? cost usd3,400 (£2125) but with 30% more energy so looking at a practical range of 65km instead of 50.

I noticed the claim of 10,000 charge cycles (if understood correctly http://gwl-power.tumblr.com/post/576978080/faq-initial-charging-information-the-above-is), that is a big WOW given (useable) 500 cycles for a Twizy battery. I wonder how the capacity degrades, similar to li-on?. That could give 30 years Twizy use WH?AT

Correction

Im sure the ad was a mistake, LiFe batteries are supposed to be good for 2000 cycles

but we are still getting a better deal with 5 battery packs for £2400 +vat and much longer life than LiMn

way to go

Robin

Much more work needed here, will contact maker

Cheers

Robin

Actually these have gotten very good reviews from users and have the same physical size: http://www.ev-power.eu/CALB-40Ah-400Ah/CALB-CA180FI-Lithium-Cell-LiFePO4-3-2V-180Ah.html, 180Ah, 9,216kWh. Don’t buy the “multi-small-cell” packs from BMS battery, in that case building your own pack with Headway cells is better, they are tested and proved: http://www.bmsbattery.com/lifepo4-cell/392-headway-40152s-lifepo4-battery-cell.html