[Tomppa]

Hi to all!

This is my first conversion. A lightweight "mid-sized" Volkswagen Polo/Derby.
This one is Polo but the saloon or sedan version is called in some countries Derby.
I have had this car for almost 5 years and it has been a joy. It takes 6l/100km or 40mpg regardless whether driving in a city or a freeway. Begs for the 5th gear in 120km/h speed.

I am not quite the engineer myself. I can barely weld, but that's why there's friends and machinists.

More info about the car, in short, VW Polo -89, 760kg, 1675lbs, 1.3l, 40kw (55hv), 96nm at somewhere in 3000rpm ermm.. 70 ft*lbf?

My goals are:

• Performance better or the same
• Top speed should be atleast 120km/h or 75mph, depends on gear ratios, which I can't change
• 100km/charge, 60miles per charge (more the merrier)
• Budget was at first 5k€ but now it's more like 10k€ and so on Depends much on batteries..
• I have bought already Kostov 9' 144v Series DC motor and TcCharger 144v (108v-216v) DC-DC converter. Other parts that I'm almost certain of are Soliton Junior, minibms, TcCharger charger 144v and a lot of batteries, atleast 144v/60ah Sinopoly (B) cells. Battery is still a bit open question. To achieve 100km per charge I should use the 100ah Sinopoly cells or parallel 90 60ah (B) cells to get 144v/120ah.

In this forum Kptn_Chaos is also doing conversion on a Polo. He writes:

the Polo has a "ready for conversion" weight of 585kg.

This means -> 760kg-(585kg+ Kostov 45kg+ Soliton Jr. 7kg) = 123kg to fill with batteries and etc. GWL of polo is 1130kg. For example 45x100ah Sinopoly = 3.1kgx45 = 140kg. I can remove the middle back seat though which adds 70kg to play with. Can you imagine this is a 5 seater car?

Some things concern me!

Polo's transmission is so tiny that even a K9 won't fit without a little machining. It hits the drive shaft
I ordered the fan, forced air cooling, with K9 and i fear that it hits engine bay wall. Damn. The motor and the transmission are currently under work by machinist, who will do the coupler and the adapter plate. Has to be clutchless due to limited space...

Currently Polo is waiting for a new paintwork. I have some pictures jeij!

Okay, this was my second post. Feel free to tell what you think and to give advice.

Tomi

[mora]

I'm watching with interest! I'd say it is tough to get 100km range at 144V/100Ah but it might be doable. Even I can get 80km range with tired/random 144V/90Ah Thunderskies in a bit heavier car and without driving too carefully (I mean watching amps, of course, heheh).

How about 160 volt pack? 50 cells in series. Shouldn't blow the budget. If charging voltage is 3.6V per cell then total pack voltage near end of charge will be 180V. Within limits of DC/DC. Soliton should allow motor voltage limit if you want to baby your motor. That means more motor amps over wider rpm range with less battery amps.

[Ziggythewiz]

I'd do at least the 100 AH cells, the less interconnects, the better. As mentioned above, add cells to boost the voltage and range if you can.

[Tomppa]

I chose Soliton for it's reliability, easy-to-understandability and all the fancy features, which limiting motor voltage is just one of.

50 x 3.2v x 100ah x 80%DOD = 12,8kWh usable energy. Should be able to travel 100km per charge at city speeds. Most of my driving, ~90%, is in the town.

DC-DC's max input voltage is 216v instead of 192v. I remembered that wrong.
HPIM1688.jpgHPIM1694.jpg
If the voltage is 160v, could I use TcCharger 156v charger? How much I loose capacity?
Charger's nominal is 156v -> 49 cells. 49 x 3.65v = 178,85 pack top voltage.
178,85/50 = 3.577volts per cell. And how does this affect miniBMS, which starts shunting at 3.6v per cell? Charger's end voltage can be customized, but I don't find it worthwhile.

I have 3 Polo transmissions. One still in the car, one at the machinist and this one is just a piece of junk. Ball bearings or/and something else has given up.
HPIM1687.jpgHPIM1686.jpg

Here you can see how small the Polo tranny is. 0.35l Coke bottle fits barely inside..


Tomi

[mora]

If ordering directly from TCcharger they will customize your desired ending voltage with no additional cost. Prices at GWL Power are very tempting though. I'd say there is no noticeable difference between 3.55V and 3.65V ending voltages. In capacity I mean. It takes like one minute for one 90Ah cell to climb from 3.55V to 3.65V at 10A charge. There is very little charge put into a cell during that time.

But will charge ending voltage affect lifespan or something else inside Sinopoly cells? Like older TS cells like occasional charge to 4.0V. What happens inside the cells if they are always charged to 3.55V? Maybe this could be asked directly from Sinopoly.

If miniBMS shunts at 3.6V then it should be no problem if charging ends at 3.55V per cell. You'll lose no additional energy to shunts. Charger will terminate charge before any shunts even start operating. This is the case with balanced pack. When pack gets unbalanced shunts will take care of cells going too high in voltage. This will happen very near at the end of charging process so charging current has already gone way down.

12800Wh / 100km = 128Wh/km or ~204Wh/mile. That's some serious efficiency in my opinion. But it might still be doable with light car like yours.

[Ace_bridger]

Watching with interest while I complete my Golf build.

Will keep an eye on posts and offer adivce where appropriate.

Good luck and well done!!

Adam

[Tomppa]

Mora's Golf and Eman Cardona's Fiat have been my main innovators.

Mora,

Even I can get 80km range with tired/random 144V/90Ah..
..12800Wh/100km = 128Wh/km or ~204Wh/mile

144v x 90ah x 80%DOD = 10,368kWh / 80km ~130wh per km. Your wh/km consumption isn't bad either.

It takes like one minute for one 90Ah cell to climb from 3.55V to 3.65V at 10A charge.

Oh, that's fast, thanks for the info!

Adam(Ace_Bridger),

Yes! Thank you. I have been following your conversation for awhile. Very neat Golf you have! Loved the video

Tomi

P.s Next week the Polo will have new paintwork

[mora]

I haven't measured total energy put back to pack from the wall but I believe DOD was somewhere between 90% and 100%. At 100% DOD that range would yield 162Wh/km but at 90% ~145Wh/km.

But then I got a bit over 60km max range with my 96V/90Ah pack and it calculates as ~137Wh/km. 80% of that distance was done at 80km/h. I have thought that upping voltage improves efficiency very slightly. So yes, ~130Wh/km should be possible.

[Nomad]

Originally Posted by mora

I haven't measured total energy put back to pack from the wall but I believe DOD was somewhere between 90% and 100%. At 100% DOD that range would yield 162Wh/km but at 90% ~145Wh/km.

But then I got a bit over 60km max range with my 96V/90Ah pack and it calculates as ~137Wh/km. 80% of that distance was done at 80km/h. I have thought that upping voltage improves efficiency very slightly. So yes, ~130Wh/km should be possible.

If I could get 130wh that would be amazing!! But ,y crushing speeds are around 65mph

[mora]

Yes, power consumption goes way up at 60mph (or ~100km/h).

Regarding 130Wh/km figure: if measured from the wall (total consumption including losses) then 130Wh/km is incredible. My charger is only ~93% efficient at its best. My previous figures (96V/90Ah) did not include charging losses.