Thursday, July 31, 2008

Visiting Synkromotive and Learning about Deka 9A31s

I visted Synkromotive two days ago to look into becoming a Beta tester of their new motor controller. It handles 600 amps and has a really nice user interface through a laptop to configure several controller parameters like the DMOC445 that I have on the AC 914EV. Other than the Zilla, I haven't seen a controller out there with this much programmable flexibility. It has inputs for over RPM, battery under-voltage and temperature as well.

During our discussions, they told me about their history with the Deka group 31 series of batteries, which I'm seriously considering using for the Civic-EV project. It turns out that, up until last year, all the public buses for Oregon and Washington used four Deka group 31 batteries in them. The bus companies were very frustrated because the batteries kept dying after 10-12 months of operation. Synkromotive worked with these companies and found out that the Deka batteries only have a 12 month warranty and only have 150 full discharge cycles of lifetime. All the buses in both states now use Odyssey group 31 batteries and have not had any issues.

It looks like the amp-hour and amperage rating for the Dekas isn't too bad, but the lifetime is horrible. The Odyssey batteries are twice as much but last three times as long and have even better amperage ratings. John Wayland uses Odyssey batteries in his EVs. Northwest Battery here in portland highly recommended Discover EV31a-a and FullRiver group 31 batteries over the Dekas as well, but they also cost more. The ZAP cars have a Discover EV31a-a upgrade, so they appear to like them too.

While I'm still sticking with group-31 batteries, I'm going to have to re-open the battery decision since I don't want to invest $2000 every 12 months in the electric vehicle. Hopefully this information will help others using group 31 batteries as well.

On a brighter note, I attended the Meeting of the Minds conference over the past two days and Oregon Governor Kulongowski announced a long term plan for supporting plug-in vehicles through a charging infrastructure and fleet purchases. I love this town. I took notes on the conference in case people want to see a huge list of factoids.



Gene said...

Heads up! Incoming slashdot link!

Kage_ said...

You have also been stumbled...

Cayle said...

Have you tried the Deka DC-31?
its rated for far more cycles than the intimadator

Mark said...

Hey, I found your site from Hack a day .com and I'm very impressed with your work! I am living vicariously through your efforts. ;)

As for the Modeling in sketchup, you can use an opensource modeling program called Wings 3D. It's not as simple as sketchup, but you can import and export with out having to pay a fee =)

I'm in the 3D industry so if you need some help with stuff like that give me a holler. Good luck and I'll continue to follow the progress.


TimK said...

Hi Cayle, The Deka DC31 is a flooded lead-acid battery. I'm shooting for an AGM battery to save on protective battery boxes and to prevent acid spillage.

Hi Mark. Thanks for the Wings3D pointer; I checked it out briefly. My one concern is that it cannot export a .DXF or .DWG AutoCAD format which enables machine shops to fabricate the resulting piece. I'm looking into In the meantime, people can simply buy the adapter plate from ElectroAuto.

Cheers, Tim

rangerpretzel said...

Hey Tim,
Have you considered the new lead-acid battery called "Oasis" by Firefly Energy? ( ) Apparently it uses a new graphite-foam core to replace much of the lead making the battery lighter and giving it a higher power density. Apparently, it also gives the battery a much greater cycle life and resists sulfation better, too. Unfortunately, the company appears to be charging a nice price premium as well, but it might be worth it anyway if it gives your EV car a longer range and less weight.

TimK said...

I've looked at the FireFly battery. I'm focusing on batteries that exist today. I believe the Firefly won't be available to hobbyist like EV converters for at least 2-3 years. In addition, I didn't think the range specifications were great for the price. I think it's a group 31, so anyone could put it in the kit if they wanted to try it out. Cheers, Tim

rangerpretzel said...

Yes, you're right that the range-to-cost ratio isn't that great. And I did notice that it appears to only be available to the "trucking industry" and not regular consumers. (unfortunate.)

Though as you already noticed, it *is* an AGM Group-31 battery (which is why I suggested it.)

Good luck!

Grampatech said...

Hey Rangerpretzel,

As a rule of thumb, more lead is better. Try to think of lead like the "gas" in an EV. More lead
means greater discharge capacity at full charge, maintaining battery
voltage under load for better performance. I think the batteries
you are looking at are for cranking
applications. Take a look at the amp-hour ratings. If they give you the 10 hours discharge rate rather than 20 hour rate, the manufacturer is being more honest about the actual storage capacity of their battery.