DDK - Die Deutschen Klassiker

Ian Donkin wrote: ↑Mon Aug 15, 2022 3:56 pm

inaglasshouse wrote: Hi Tim,
Happy someone is enjoying reading this off-topic nonsense.

I suspect you have quite a few 'lurkers' watching this with interest, Richard....

Possibly, Ian. Looking on in horror as I defile a classic.

Anyway, back to batteries and packaging.

For a sense of scale, here's one of the 18 modules in the boot of a G Wagen:

It would be possible to get 16 of the 18 in the boot, with the top of the 2 layers being level with the wheel arch type feature you can see on the left.
Not that they are going there, but it gives you an idea.

And while we are enjoying photos of things in the back of a G Wagen, here's a standard euro crate (I am told):

Not only a thing of beauty. Also a thing with an 800mm x 600mm base, and 240mm high.
Handily that makes it the same size as 8 modules, 2 layers of 4.

If you're not yet asleep, that means 2 euro crates simulates a 16 module pack. Yes, I know I could draw it in solidworks etc etc. I'll save that for a project with more challenging space constraints.

Last crate shot. Probably.

Round the front we can get an idea of just how unchallenging it's going to be, to fit the battery pack into this particular vehicle.



Long story short: a pack of 16 batteries (4 layers of 4, 2 green crates on top of each other) fits where the engine now sits. And is probably lighter....
Nice strong engine mounts there on the chassis rails will do nicely for a bolt-on battery box solution.

There will still be space in the engine compartment for some of the new components for which we need to find homes (inverter, charger, and various other things that are needed - more on that later).

Note - we have not needed to use the fuel tank space yet, or the space freed up by the (huge) dual exhaust silencers, or the other space between the chassis rails. I'm thinking if the concept basically works, but I need more range, space will not be a problem for a second pack. Cost, however, will be - the batteries are not cheap.

As a reference point, I have 18 LG Chems in the 914, the car weighs about 1260kg. I drove at 'normal' speeds to Wimbledon and then back (with a bit more gusto) last week from East Sussex for a total of 130 miles and I got back with 38% charge left which equates to about 180 miles total. This is more than the predicted range of 150 miles. I think you may do a bit more with the Leaf motor.

I'm off to Chobham tomorrow and the air conditioning will be on so will report back!

p.s. 'normal' speeds in the 914 EV still means leaving my mate's rorty-torty 2.1 fast-road engined 914 for dust at every opportunity.

Thanks Jonny. So LG chems very similar to my CATL modules? 6S2P, about 2.6kWh per module?
914 sounds eminently usable! Well played. I need to see it in the metal. Last time I was stood next to it, it had recently arrived from the US and still had the forklift (or something) motor? Very different now!

I've made some crude predictions, and I fear 100 miles is going to be nearer the mark for me. Sadly a G Wagen does not weigh 1260kg. The aero is just as bad as it looks. And it's permanent 4WD...
Project spec: minimum usability requirement is London and back / boat and back / Goodwood and back, each of which is about 80 miles. Much more useful would be Cornwall or Yorkshire with only one stop (and decent DC fast charge speed, so it's not a 2 hour stop). The latter is version 2 stuff.

Did you implement fast charging on the 914?

.
Mercedes have nicked your idea!

https://www.autocar.co.uk/car-news/new- ... ttery-tech

Hugo 356 wrote: ↑Tue Aug 23, 2022 11:24 pm .
Mercedes have nicked your idea!

https://www.autocar.co.uk/car-news/new- ... ttery-tech

Haha. Indeed. Although I’m hoping mine will be ready before 2025, and be a tad less costly. And more environmentally friendly, but let’s not go there.

Have you seen its party trick: the tank turn?
https://www.youtube.com/watch?v=NwHbJ7HN1sU&vl=en

Neat trick. I'm doing less of those manoeuvres since sat nav came along

That tank turn is pretty cool.

I think batteries in a 914 is an excellent idea. Give me about 5 years to wear out my new engine and I will be able to buy twice the power for 1/2 of the cost at 1/2 the weight?

Sent from my M2004J19C using Tapatalk

inaglasshouse wrote: ↑Wed Aug 24, 2022 6:44 am

Hugo 356 wrote: ↑Tue Aug 23, 2022 11:24 pm .
Mercedes have nicked your idea!

https://www.autocar.co.uk/car-news/new- ... ttery-tech

Haha. Indeed. Although I’m hoping mine will be ready before 2025, and be a tad less costly. And more environmentally friendly, but let’s not go there.

Have you seen its party trick: the tank turn?
https://www.youtube.com/watch?v=NwHbJ7HN1sU&vl=en

in tank-land, thats called a neutral turn. Not all tanks can do it, depends on the steering mechanism

https://www.youtube.com/watch?v=iBbo3TelVnU

I thought I was on some illegal substance when I first saw this thread. Revised that to think I was dreaming as I have not imbibed for a very long time. Revised again into thinking it was a weird nightmare. Bump! It's real! A new reality? Richard old bean you are either very brave or a little foolhardy or maybe you have been on the magic mushrooms? Although not really interested in owning an EV I will watch with interest as you young things fiddle with your software and hope to stimulate the hardware into life. Or is that just a tortuous euphemism?
Anyway hope you are well and good luck with the project.

tortuous euphemism - how wonderful

No, it's real Kirk. Certainly foolhardy. No euphemisms, tortuous or otherwise, have (yet) been deployed.

And there has been progress. I have hooked up the pack and written V0.1 of the code for my inverter controller. My 18GBP (eBay) Prius throttle pedal now talks to the microcontroller, which sends CAN messages to the inverter, which drives the motor. It all works...
I have also implemented crude regen, and reverse gear.

inaglasshouse wrote: ↑Sun Aug 28, 2022 6:03 pm No, it's real Kirk. Certainly foolhardy. No euphemisms, tortuous or otherwise, have (yet) been deployed.

And there has been progress. I have hooked up the pack and written V0.1 of the code for my inverter controller. My 18GBP (eBay) Prius throttle pedal now talks to the microcontroller, which sends CAN messages to the inverter, which drives the motor. It all works...
I have also implemented crude regen, and reverse gear.

Thanks Richard. My head now hurts.

Pretty decent progress continues, on the coding side.
Next up is the Battery Management System (BMS).
With apologies to those who know all this, a brief summary is that a BMS, at minimum:
- measures the voltage of each cell
- measures temperatures in the battery pack
- implements cell balancing, meaning that if the charge level of some cells differs from others, it can rebalance (effectively by charging the low ones from the high ones using internal switches)

The first two points are pretty important. Full EV battery packs are not cheap, and lithium-based cells die immediately if discharged too far, and die prematurely if overcharged. So the second-worst case, if you get the battery management wrong, is a very expensive, very large paperweight instead of a battery pack.
The worst case involves flames and the rapid demise of my electric G Wagen dream.
The BMS is especially important if attempting DC fast charging, which I do intend to pursue in version 2 (or 3 or 4 or whatever).

So, worth having a BMS then.