4-8-06 AC vs DC

Hello to All,

I always enjoy the AC vs DC debate. One point very rarely brought up though, is what you get in terms of performance in return for your dollars invested, especially when the price of the AC system hovers in the $8000-$10,000 range. Yes, a  68 kw AC system can be had for about $6000, but that’s on the low side of power for a conversion and is more comparable in power to older tech 120V DC systems. To get up to the power level of today’s common 144V-156V DC systems being used that easily top 100 kw, the AC system will cost you closer to $8000.  For $8000-$10,000, you get an AC system with about 100-130 kw of power. For the same dollars for DC….listen up newbies and pro AC folks,  you get up to 600 kw!!!! I’m talking about raw power that can be easily had with a Zilla Z2K, stout AGM batteries, and either one BIG DC motor or a pair of DC motors.  Now, in real life, due to the fact that batteries sag under high current loads, no one that I know presently has actually gotten their 600 kw of power delivered in their EV, but I do know that 350 kw has been had :-) We’re talking about THREE times the power for the same price…I’ll repeat….THREE times the power for the same price! Not just two times the power, THREE times the power!

From Metric Mind’s web page, specialists on AC systems (good folks to do business with) comes this statement:
>Zilla 2K comes to mind….with a DC motor becomes $6100, just $800 less than a complete AC solution (100 kw).

It goes on to admit that even the Z1K at half the power of the Z2K still has more power than this AC system, but the power level thing is down-played. The problem I have is where the Z2K, a 600 kw system is compared to the 100 kw AC system, where this part is left out…..The Z2K Zilla package delivers SIX times the power for the same price (if a powerful enough battery pack is used) and in practical terms, it delivers THREE times the power!

A nice 100-130 kw AC system ‘can’ match the power delivery of the average gas car, but so can an affordable 100-130 kw DC system.
The big difference in this power range, is that a simple pack of just 13 AGM 12V batteries (156V) and a Zilla Z1K will easily make 130 kw of delivered power. Here’s the approximate cost to do this….$2000 for the Z1K LV model, $1450 for 13 Optimas or Orbitals, and $1600 for a 9 inch DC motor, for a total 130 kw package of $5050. A 100-130 kw AC system will cost you about $7000, but to run it to the power level of around 100 kw, you need a 300V battery pack. That pack will cost twice as much as the 156V pack for the DC system, even if you run smaller AGM batteries so that the overall pack weight is the same (same approx. range) as the 13-battery DC pack. So, for $7000 for the inverter-motor combo and $2800 of batteries you are up to $9800! We’re looking at twice the cost for the same level of performance. When using battery management modules, the cost of these is doubled with the 300+V AC system, too.

Am I dissing AC? Of course not. I love AC. My Insight has it, many of the forklifts I work on have it, and one of my favorite EVs I’ve driven, the EV1 had it. From time to time, I think about converting Blue Meanie to a 130 kw AC system. After all, I already have a really fast DC Datsun 1200, why not have a little regen fun and do the other 1200 as an AC system? The only problem I have is price for what you get in return. With similar weight lead acid battery packs, I’ll pit my DC powered car to ‘any’ AC powered car in terms of range per charge, 0-60 acceleration, top speed, and over-all fun factor. On the other hand, a direct drive AC Blue Meanie with a higher tech battery pack is a fun concept.

From time to time, I get to hang out with Victor (Metric Mind). A few weeks ago, he and I got together at his place. I found myself smiling at his latest AC system with a very compact inverter module and a motor that was, well, more ‘motor-like’ than some of his other square AC motors. It screamed ‘Blue Meanie’ at me. I also nearly tripped over stacks of Ovonic NiMH batteries, the same models that were  used in the EV1 I drove for 140 miles per charge years ago! I was thinking a set of them and that nifty compact AC system would turn Blue Meanie into a 150 mile per charge machine, while still maintaining ‘respectable’ performance. Alas…..it would cost about $10,000 to get these toys.

For now, I’ll be putting a pack of Hawkers into Blue Meanie to get it back to snuff (the 6.5 year old Optimas are finally ready to be recycled). Until I take the AC plunge, I guess I’ll have to settle for 0-60 in six seconds, a 120+ mph top speed, and the ‘city driving only’ range of 25 miles per charge (unless I get some really new model Hawkers I’m not supposed to talk about yet).

Kudos to Victor for helping to make AC systems available to backyard converters. It’s great to have these systems available at more reasonable prices than the $20-$30k systems of the late 90′s!

See Ya…..John Wayland

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One Response to 4-8-06 AC vs DC

  1. George Johnson says:

    I am looking for a (Kit )for a/c system like you have described. No one that I have found has a complete Kit. I would build the kit from parts but I am having trouble finding everything online. I wish someone would list ( 1-Whatever ) the componets needed complete. A wiring diagram. This could be used for any car. I know computerized cars have to be fooled so the electronics can be used and the steering will not lock up(among other things),but I am strictly after the meat and potatoes. Can anyone help? Thanks George from Virginia,USA ;)