Tuesday, April 14, 2009

A Touch of Spring Cleaning

Well, after a long period of Silence here, I felt it time to add some news!

The car has been parked for most of the winter - not just because of what it does to Lead Acit Batteries, but because the Landlord - while pushing snow in the parking lot - took off the front plate and holder! Just Caught it with the Blade on the Pickup, and ripped it right off - putting a bad 'Z' wringle into them both, plate and holder! I just got them straightened and reinstalled today. I had Danny at Pat's Automotive Service help me out with it, although as he was working on it - I realized I could probably have taken it to work and straightened it out there!

Oh Well - It only cost me $10 to get it fixed up reasonable, and re-mounted on the Front Bumber, but we had to mount it lower to get some grip for the screws, and I would likely need a new bumber to do it right, and get a new Plate - $97 for one Custom replacement!

I also decided to put a bit of charge into the pack, as it said 91% SOC on the Woodward Display when I started out today, and about 69% when I got back home. I think the Batteries are a bit tired, but still - I had them on the charger for 3 hours and 39 minutes before I checked up on them, and they only took 1.02 kWh, or 13.2 Cents worth of Electricity (Including: Electricity Taxes, Delivery & Ontario Hydro 'Debt Retirement Charge!')

Not so bad for a total of about 5.5 Km on the Trip meter, between the last drive and this one - that would be under 200 Watt Hours per Kilometer. Interesting - I was just reading an old post on the EEStor EESU (Electrical Energy Storage Unit), 52 kWh for under 340 lbs (I think it was 336 lbs), so that would be about 60 lbs less than my current pack, and enough energy to push it along for about 250 Km or better!

I have Been looking at the options of Lithium Choices in the mean time, with my general interest leaning towards ThunderSky TS-LFP160AHA Cells. 32 of them give me over a 100V Nominal at about 102.4V, sot 102V x 160Ah = about 16,000 Wh. Using 80% Depth of Discharge gives a usable energy of about 12.8 kWh. If my average power use is 5 Km per kWh - then I can get about 60 - 65 kms on such a pack. However - my basic calculation is about 135 - 140 Wh per Km - sot that would get me about 90+ Km range. That would be enough to cover just about all the local city driving needs, including some trips out to Pickering and Oshawa (might need a bit of a charge while there, but it would still be doable!)

Other thoughts go towards the A12326650M1 Cells, of Which I have already got 24, enough for a 4S6P Pack - or 13.2V x 13.8 Ah, in a really small pack, for a weight of only about 1.68 Kg for the cells + a bit for joining bars and whatever Cell Protection Cicuitry or BMS System might be added with it.

More Lately - I have started thinking more towards Tesla Motors Style of thinking - Lithium-Ion (Cobalt firecrackers) with critical BMS and Thermal management, due to the lighter total mass for a given available energy storage level. Using a Cell limit of 2C means I would need a minimum of about 120 Ah worth of storage for a safe load of 240 amps continuous, but such a pack would be quite a bit less than my current 400 lb lead-acid pack!

Example - the 3.7V 2600 mAh Samsung Li-Ion 18650 Battery: weighs just 46.5 gms or 1.64 oz per cell. Making a 130 Ah Pack at 103.6V would have a Cell weight of just 143.22 lbs, so even doubling that weight for BMS, Cell Protection Cicuits, and Thermal Management, is still just 286.44 lbs, or 113.56 Lbs Less than my current pack, but give a total energy of 13.47 kWh, with an 80% DOD still gives 10.77 kWh usable and about a 54 - 77 Km Range! (Some 2X - 5X my current range!)

If the BMS Complete & Thermal Management weighed in a 50% of the Pack's cell only weight, going to a 103.6V x 260 Ah Pack does 2 things - (1) ends up with an energy storage of 26.94 kWh total at a weight of just 30 lbs over my curent pack, but about 26 lbs less than the batteries that were in the car when I bought it! (2) Provides a minimum Range in excess of 100 Km (107), and a possible range in excess of 150 Km (153) at 140 Wh/Km! This is at an 80% DOD yielding just 21.55 kWh usable!

Also - the 260 Ah Pack allows higher current draws for more spectaular acceleration runs - easily allowing the controller to start over powering the motor with 260 Amps (at a battery 1C Load) or even up to 390 Amps (At a battery load of just 1.5C - within the 2C Limit)! this would be quite spectacular I am sure - as I have never drawn over 240 amps, but with Lead Acit - that gives up power because of the large Voltage Sag! At Highway driving - I used to draw about 185 Amps at about 100 Kmh, but my pack voltage sagged to about 75 Volts, so I was only getting about 13.8 kW out of the motor, but - that still gives about 138 Wh/Km!

Anyway - lots to think about while I go forward with this car, and most things get to be a bit expensive, even just adding the desired remaining instruments could cost from $400 to over $2000! Ranging from eMeter or Link-10, to the eVision from Metric Mind, or a complete custom SVGA 800 x 480 Video Display system, with custom screens.

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