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  #21  
Old 09-22-2011, 04:35 PM
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dimitri dimitri is offline
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Default Re: C-Rex: Notailpipe's Honda CRX Build

This largely depends on your DC-DC connection. If its always on ( my preference ) then aux battery can be very small. I used lawn mower battery ( $25 at any hardware store ), later switched to 4 Headway 10AH cells ( under $80 and will last forever ).

If DC-DC is key switched, then you may need larger battery if the car will be sitting idle for days at a time, in which case small battery will not have enough time to charge while driving and will eventually run low.
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  #22  
Old 09-23-2011, 01:52 PM
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Cool Re: C-Rex: Notailpipe's Honda CRX Build

And now something of great importance to any car, ICE or electric…
A cupholder! CRX’s did not come with them. Many with more modern cars will not be able to fully appreciate the importance of this, but the folks over at CRXcommunity.com were excited about my writeup!

Before: Note the useless pocket (there are plenty of other places in the car for sunglasses, nothing for drinks!):


After: One ice-cold beverage plz!


The cupholder comes from an Acura Integra, and replaces one of two little pockets in the dash. Now that the heater and cupholder are installed, only one thing remains before I can re-install the dash -- the conversion of all dash lights to LEDs.
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  #23  
Old 09-23-2011, 02:12 PM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Quote:
Originally Posted by dimitri View Post
This largely depends on your DC-DC connection. If its always on ( my preference ) then aux battery can be very small. I used lawn mower battery ( $25 at any hardware store ), later switched to 4 Headway 10AH cells ( under $80 and will last forever ).

If DC-DC is key switched, then you may need larger battery if the car will be sitting idle for days at a time, in which case small battery will not have enough time to charge while driving and will eventually run low.
Can you elaborate on key switched? I plan to have the DC/DC converter always on and always topping off the battery. So the battery only helps with current surges, like headlights, and is there long enough to get me off the road if the DC/DC dies.

I am seeing some 12V lawnmower batteries at Home Depot for $25, and 14lbs. I'm liking the sound of this idea. Obviously, they will have lower capacity rating but that probably does not matter. Weight and price are the important specs for this application. So that first battery I linked to is probably paying 5x more money for capacity I'll never need.

Since it's a starter battery, not a deep-discharge, I assume it is designed to always be topped off by a charger (or alternator) safely. Do you think that's a good assumption?

The exact model I'm looking at is this one by Interstate Battery.
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  #24  
Old 09-23-2011, 02:16 PM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Yes, this is exactly the same one I used for over a year. As long as DC/DC is always on and battery is always topped off, it will work fine.

Mine was working fine and I did not have to replace it with Headway cells, but I wanted to see how Headways will work in this application , plus I was on Jihad to remove all Lead Acid from my life
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  #25  
Old 09-23-2011, 03:21 PM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Sweet. Okay, I've decided to go this route as well. Feels great to get another design decision out of the way!

I'm actually looking at a different battery now, but same idea. I like this battery by Interstate. A little more money than the other one I linked, but less than half the weight, at only 5.4lbs! It's only 7.2Ah, so a little less than your Headway battery, but the one at Home Depot doesn't list the Ah, so I can't really compare. 7.2Ah is still plenty to limp home, and at the very least get off the road. I won't be blasting my music if my "DC/DC has died" warning light goes off... haha
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  #26  
Old 09-23-2011, 04:15 PM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

I know this battery well, removed a handful of them from my UPSs and swapped for LiFePO4 as well, using cheap Chinese A123 1AH cells. It should work OK along with DC/DC, as long as you don't have any heavy loads on 12V side.
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  #27  
Old 09-23-2011, 04:47 PM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Cool. "Okay" performance is all I need for this. My vacuum pump is probably the biggest 12V culprit at 8A, but I've got a pretty decent reservoir to keep on/off thrash to a minimum. After that, maybe the stereo, but no subwoofer/amp. After that, all my lights in my car (except my headlights, which are HID and thus a little less power than halogens), are being converted to LED. So I guess I've done the most I can do.
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  #28  
Old 09-29-2011, 04:31 PM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Great thread! Very interesting to read and learn. Any updates since your last post? I'm an eye-candy addict, so thanks for the pictures too.
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  #29  
Old 09-29-2011, 05:19 PM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Sorry for the slow updates. Things have been crazy at work and at home...

My progress has been very "researchy" lately. Reading my Zilla manual, thinking about safety concerns and how I want to hook up everything, and designing my overall circuit diagram (in my head, probably won't write it down).

So far, my conclusions from my research:
  • Picked a battery --> above
  • Likely to go with 1 or 2 Tyco EV200 contactors, which support 500A nominal (that will be a ton in my tiny car)
  • Picked a charger --> Elcon PFC-2500, because I want the option to charge 120/240VAC. I'll use a 240VAC outlet and make a tiny adapter spliced together for Opportunity Charging at friend's/family's house off 120V.
  • Picked a BMS --> MiniBMS by CleanPowerAuto
  • Picked a SOC gauge --> EV Display by CleanPowerAuto (nice designs, Dimitri)

Mostly picked a DC/DC converter --> I like the price point and overall features of this converter by ACME, but I've never heard of them before. And I tend to shy away from things that remind me of Roadrunner cartoons... Anyone heard anything good or bad about this one?

The plan is to order everything and get it on the way, while I work on my battery racks this weekend!
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  #30  
Old 09-29-2011, 06:03 PM
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Default Re: C-Rex: Notailpipe's Honda CRX Build

Here's a little more of what I've been up to:

First, a lot of vacationing. That's always nice, but it's been a little frustrating to not make as much progress as I'd like on the car. I know, I know, pretty good dilemma to be in.

My wife and I took a little trip to Silicon Valley. Woulda been cool to visit Tesla (though I heard they're not doing so well)...


Being the enginerds we are...
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