Charade: 150kms on Li

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I, Claudius
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Joined: Wed, 21 May 2008, 18:03
Location: Sydney

Charade: 150kms on Li

Post by I, Claudius » Mon, 19 Jan 2009, 05:19

Hi all,

As some of you know, and have been waiting for updates on, our EV (EV Album) has been off the road for a few months while undergoing a re-conversion to 144V/160Ah of TS LFPs from the original set of tired old T-875 floodies (120V/170Ah).

Was (finally) able to perform the commissioning charge and first test run last weekend; it was clear from the first tentative acceleration that removing ~180kgs of battery weight had made a dramatic impact. Compared to the previous state, it feels "effortless"...

(Aside: Even pushing the vehicle around by hand is considerably easier, disproportionate to the weight removed, as confirmed with a hanging scale... which is not what we all "know" to expect. Non-linear drag region of bearing or tyre load?)

With the pack balanced after several further short test and balancing runs throughout the week, I was itching to perform a real-world range test. Yesterday, I had my chance...

Choose a nearby on-road test location: 5km circuits around a friend's place (just in case!), where it would be possible to run at the posted speeds of 70 - 80 km/hr, slowing to 0 - 40 km/hr four times every circuit (ie. on each leg), with some up-and-downs on each leg. Test to conclude when unable to maintain moderate (ie. non-embarrassing) acceleration without under-voltage event on any cell.

Conclusion: 150.1 kms

To be honest, I do have to admit that the first 20kms of acceleration were considerably more "fun" than the last 20kms -- as that 150km target became nearer, I couldn't help but be more conservative with the throttle to contrive the result.

(Aside: Interestingly though, the ~17km freeway trip to the test location used approximately 30% less Ah/km than circuits at the test location, despite a higher average speed and not dissimilar slow-go cycles and terrain -- some combination of the relative roughness of the road surface, and bumpiness of the test circuit road. Driven conservatively, on optimal surface, > 200km should be possible... if entirely unrepresentative of normal driving)

So good so far, but I'm wondering if I have a couple of runts in the pack.

Not very far into the test, at least one cell was occasionally causing undervoltage (< 2.5V) events from the BMS under harder acceleration, even though the total pack voltage remained happily above 135V (ie. suggesting an average cell voltage of > 3.0V) under such load. I have noticed that a handful of cells appear to have a higher self-discharge rate than the rest, suggesting a higher R_int, and so are the likely candidates. Will be monitoring those carefully.

Only time will tell how the pack behaves -- hopefully the niggles with these runts don't develop into premature failures.

Will eventually update the EV Album link with new pics, some time after all the remaining loose ends are finished off.

All for now...
Claudio

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Taffy
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Real Name: Taffy Flynn
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Charade: 150kms on Li

Post by Taffy » Mon, 19 Jan 2009, 05:45

Thanks for the review of your performance. Very interesting to see.

I just saw that Zilla are no longer/there is a shut down in manufacturing there controllers... Ahh damn!

You still have the same controller? and which BMS system? Your set up is very close to what i was planning.

I, Claudius
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Posts: 14
Joined: Wed, 21 May 2008, 18:03
Location: Sydney

Charade: 150kms on Li

Post by I, Claudius » Tue, 20 Jan 2009, 15:12

Taffy wrote: I just saw that Zilla are no longer/there is a shut down in manufacturing there controllers... Ahh damn!


Hopefully there will be some good news about this soon...
Taffy wrote: You still have the same controller? and which BMS system?


Still using the Zilla. For BMS, I'm using the TS90 system from EV Power.

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