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Discussion Starter #1
I am working on a project to replace the battery in my 1999 93 with super capacitors. The idea is half the weight and a lot longer life. Has anyone else done this with their car before? If so how well did it work? Also does anyone know how much ac ripple voltage the 93 computer can handle? I'd post a link to the videos of the testing I have done so far but I can't post links yet.




Thanks
 

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Wiggy: I can't answer your ripple question... but I can tell you we've seen a number of examples of them running poorly with a weak battery. You wouldn't think that would matter once they were running and operating on alternator power, but it has made a significant difference a few times. Make sure it has some depth to it.
 

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Discussion Starter #4
I should have the parts in a week to see if it will work. Right now I have it starting and running without a battery but my caps are to small to be reliable.
 

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Discussion Starter #6
I am going to be running 6 in series to get the correct voltage rating. If your interested I have been doing videos on how I set this up. They are on YouTube just search for wiggys.shop
 

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I would think that big capacitors would smooth out ripple even better than a lead-acid battery. Have you measured significant ripple in other installations?
 

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Discussion Starter #8 (Edited)
This is my first time trying this so I don't have any other installations to compare it to. When I measured the AC Ripple the oscilloscope was showing about twice the magnitude that it was with the battery. I would guess this is still small enough not to make a difference but I'm learning this as I go so I could be wrong. The screenshot of 50 millivolt divisions is with the battery the 100 millivolt divisions one is with the capacitors.
 

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Yikes. How many farads are the capacitors? What's their rating in terms of output amps?

I am thinking that there may be too much resistance in their internal wiring for them to react quickly enough to a voltage change.

A lead-acid battery has low internal resistance. That's why a metal wrench dropped across the terminals will melt.
 

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Discussion Starter #10
I was running three Banks of Green Cap capacitors. I got them off of eBay and got scammed. They not even close to the datasheet. I switched over to 6 3000 f Maxwell capacitors. I'm running them in series and the internal resistance should be 1.74 m ohms. When I get a chance I'll have to check the AC Ripple I'm hoping that these should be better then running a battery.
 

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Ha, yesterday I did a bit of checking on those "300000 mAh" charging packs. When opened up by skeptical reviewers, they have two 2400 mAh batteries....and that's trusting the battery labels. I look at my car battery, which is 61 Ah....and these smartphone-sized charging packs have 30 Ah? :roll:
 

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Wiggy: What happens if you need a second start? In other words, if it doesn't start on the first attempt and you need a second round? Maybe you could test that by pulling the fuel pump fuse, cranking it for a few cycles as would normally happen, then install the fuse and crank again?

Also, any idea of reserve capacity i.e. can you run the radio for an hour and then still have enough charge to start the car? Does a small but steady drain pull them down much at all?

Last questions: Did you do the circuit boards yourself or is that a commercial product? How much do you have into it dollar-wise?
 

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Discussion Starter #14
When I started this project my goal was to get 15 seconds of cranking time before the voltage dropped lower than what it does with the battery turning it over. I know that I'm not going to get that much out of this setup.

Hopefully I will have time this weekend to do that cranking test with the capacitors and compare the data to the original battery.

The capacitors ended up costing me $240. They came with the balancing boards I believe that those are passive balancing boards which are not ideal in this application but seem to be working good enough.

Below are the ways that I was originally testing the battery and was planning on doing the same testing to the capacitors. if you have any suggestions on better ways to do it please let me know.
https://youtu.be/RhZ9-moZ-dA
https://youtu.be/2bW2CXijFtE
 

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Discussion Starter #15
I tested the final set up. The ac ripple is less then it was with the battery. I get about 8 min of running the radio and can still start the car. Also I get about 10 seconds of turning the motor over under normal conditions. I'll try running it and let you know how it holds up.
 

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I tested the final set up. The ac ripple is less then it was with the battery. I get about 8 min of running the radio and can still start the car. Also I get about 10 seconds of turning the motor over under normal conditions. I'll try running it and let you know how it holds up.
Updates?
 
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