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Old 09-05-2007, 06:22 PM   #1
gordo5 OP
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Beware the Bat-Pac

The Bat-Pac is this device some guy is flogging on the web as a replacement for a battery in bikes that are kick start. It’s lighter than a battery, maintenance free and, as his website claims: ‘The Bat-Pac's voltage output is better at idle, and more stable and cleaner at all R.P.M.'s’

The most embarrassing thing about this post is that I have to confess to being suckered into buying one of these things. My only defense is that it was an ebay bid that I didn’t expect to win. In any event, I ended up with it and decided to try it out, but I had my reservations. So, I connected a voltmeter with a max hold function to the bike and took it for a ride with the battery still in it. I got a max voltage of 14.5V which is actually bang on spec for my bike (Yamaha xt350). Then I swapped out the battery for the ‘Bat-Pac’ and went for another ride with the voltmeter on it. I measured 16.7V. Yikes!

Convinced this thing was a farce, it was time to dissect. My findings proved there was even less to this thing than I’d imagined.

1) The ‘Bat-Pac’
2) Take the dremmel to it
3 and 4) Split the thing open and have a bit of sand fall out

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Old 09-05-2007, 06:27 PM   #2
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Fully disassembled, the Bat-Pac is revealed to be nothing but a capacitor. As always, buyer beware.

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It appears these things are selling. I decided I'd rather reveal it to the community than chase after a tiny refund. There isn't anything illegal about it, but it's criminal anyway.

Cheers all
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Old 09-05-2007, 06:36 PM   #3
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How many microFarad (uF) is that cap and what is it's voltage rating?
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Old 09-05-2007, 06:46 PM   #4
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Quote:
Originally Posted by spidennis
How many microFarad (uF) is that cap and what is it's voltage rating?
+1

That looks like a pretty tiny cap to be using for a battery eliminator.
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Old 09-05-2007, 10:33 PM   #5
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So please explain to us less electro-savvy inmates the principle behind this thing. Why and how should it work? I did poorly in Physics II.
I too have seen these for sale.
Thx
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Old 09-06-2007, 08:42 AM   #6
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Dont discount it yet...

Suzuki is going to use capacitors like this in their new fuel injected RMZ's instead of a battery.

They ARE much lighter than a battery and can provide a large amount of power for a short period of time. If you don't need power for engine-off (not running) accessories, like DOT compliant lighting, then this could be a great solution for kick-start bikes - even with headlamps and fuel-injectors.

I bet you'll see all the MX bikes using FI going to this setup.

With this said, you do not want to use this in your GS or KLR as it will not store a charge long enough for the e-button to power your starter if the bike is off for a few minutes.

PS - for those unfamiliar with these: cutting open a capacitor is not a smart thing to do if you don't know what you are doing. The unit you cut open looks like it is well insulated and protected, but if you touch the two terminals you could easily get a large voltage shock (lethal).

PSS - you need a voltage regulator for these to work. They just store gobs of power and really don't care if connected to a 12v system or not.
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Old 09-06-2007, 09:32 AM   #7
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I believe Arctic Cat (and maybe some other brands) have been using these in their "batteryless" fuel injected sleds for quite a few years now. Follows the bike manufacturers would do this too.
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Old 09-06-2007, 03:41 PM   #8
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Quote:
Originally Posted by DirtyDog
So please explain to us less electro-savvy inmates the principle behind this thing. Why and how should it work? I did poorly in Physics II.
I too have seen these for sale.
Thx
http://en.wikipedia.org/wiki/Capacitor

My explanation:

A capacitor is two metal plates separated by an insulator. If you apply a voltage to the plates, they will store an electric charge. If you disconnect the voltage source the charge will remain on the plates and the measured voltage on the plates will also remain until it is drained off by some external circuit. The amount of charge stored on the plates is related to the physical dimensions of the plate and the voltage applied to the plates.

Charge stored = Voltage across the plates * Capacitance of the particular device.



Charge is measured in Coulombs, Voltage in Volts, and Capacitance in Farads.
An Amp is the rate at which charge moves, in Coulombs per second.
A coulomb is 6,241,506,000,000,000,000 electrons.

Capacitors also have a voltage rating, usually printed on the case next to the capacitance value. It refers to the highest voltage that can be safely applied to that capacitor.

In this case, guessing by the picture, the capacitor is probably 5000 microFarads. So when charged to 15V, it stores 15*.005 = .075 coulombs of charge. Compare that to a 7Amp-hour battery which stores 7*3600 = 25200 Coulombs.

The point of the capacitor is not to provide power for any accesories -it can only run a taillight for a fraction of a second. It is there to help the conversion of AC power from your stator to smooth DC power. The rectifier converts the AC into pulsed DC, the capacitor has to provide power for the dead time between the pulses. In the case of devices running off wall current, the cap has to power them for 1/(60Hz*2) = 8.3mS. For motorcycles, the frequency is higher, 1/(240Hz*2) = 2.1mS in the case of my XR. The *2 is because there are two pulses per cycle.

So using the XR as an example, The load is 6A, so the voltage on a 5000uF cap will drop 6 * .0021 / .005 = 2.5V. So if the regulator limits the voltage to 14.5V during the pulse, the voltage will drop to 12V just before the next pulse.


Make sense?
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Old 09-06-2007, 04:00 PM   #9
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Thanks Luke for the electro-tutorial. I had always thought the capacitor was used to provide a bit-O-charge for those the need a slight charge during startup. But I now see the capacitor does other things.

A fella I once spoke with who, on the side made capacitors for M/C applications (a fella who worked with Honda Racing down in L.A. at some point), said he got his capacitors surplus from the military because that was the only way he could get one big enough that was also cheap enough for this application.

I'd send that crap back to the vendor with a sample of your own crap in the box
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Old 09-06-2007, 05:39 PM   #10
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Weatherized cap like that is big bucks. OEM KTM 2200MFD is over $70. The cap itself is around $1. Not saying things should cost that, but it's the enclosure and leads that add value.
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Old 09-06-2007, 06:21 PM   #11
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A battery uses an electro chemical reaction, and will generate a fixed voltage, that will slowly decrease as the chemistry is expended.

A rechargable battery is the same, but uses chemistry that can be "reversed". You feed power into it, it undoes the previous chemical reaction, you pull power from it, it re-does the chemical reaction.

A capacitor simply stores a charge... and will seek the voltage applied to it. So if you drop 13.2 volts across a capacitor, it will draw a LOT of current quickly until it stores enough energy to go up to the applied voltage (13.2 in this example). A capacitor will quickly go to whatever voltage you apply to it (or explode trying) based on the resistance of the current path. The more resistance, the slower the voltage goes up (by a deterministic RC time constant).

Thats a lot smaller cap then I would have expected for a battery replacement. And if I were building one, I would want some sort of current limiting, a simple resistor with a diode in parallel (arrow pointing away from capacitor) would do the trick nicely, it would make the cap charge slowly, but discharge quickly if necessary... though at the cost of a .6 volt drop.

All in all, a battery is probably a better solution, though something like this could work and weigh next to nothing. Mendelsons electronic surplus in Dayton Ohio has about 4 acres of electronic surplus, and you can probably buy a mil spec capacitor the size of a beer can for $5.

Thanks for posting that, i was looking at those as well for my "brought back from the brink of the grave" KLR 250. I'll have to hit Mendelsons and see if I can throw together something better.
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Old 09-06-2007, 07:11 PM   #12
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Its a rehash of an old idear that as old as ... well as old as a capacitor design. Back in the 70s there was an outfit that sold what was called a "Battery Eliminator" for Honda 4-strokes. Those Honda dirt bikes of the early 70s required a fully charged battery in order to kick start them. I had a a '72 SL125 that was seriously tweaked, paying attention to every ounce I could shave so naturally I instsalled one of dem devices. By tossing the battery and battery box I was able to install a Preston Petty (how many folks is old enough to remmeber that great name?) air box, fiurther reducing weight by eliminating the sheet metal air box.

Don't know if it was the Battery Eliminator, the 11.5 - 1 high compression piston, the hgot cam or over sized carb, but that hopped up Honda was a bear to start cold.
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Old 09-06-2007, 10:56 PM   #13
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Quote:
Originally Posted by potatoho
Weatherized cap like that is big bucks. OEM KTM 2200MFD is over $70. The cap itself is around $1. Not saying things should cost that, but it's the enclosure and leads that add value.

The KTM cap is a standard computer grade capacitor. It's pricing is -shall we say- enthusiastic, even compared to KTM's pricing on other replacement parts. It doesn't need any special sealing to work on a bike.

The sealing on the bat-pac is only there to hide the fact that it is just a capacitor. Trailtech sells much bigger caps at reasonable prices for the same application. So it's a rip-off, but at least it pretty much does what it's supposed to, unlike fuel line magnets, etc....


BTW, for a real value, electronics surplus stores usually have capacitors for $2-$5 in the sizes we want.
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Old 09-06-2007, 11:07 PM   #14
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Maybe it's really a fluxcapacitor.
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Old 09-07-2007, 12:38 AM   #15
rmhrc628
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Quote:
Originally Posted by BuckRider
Suzuki is going to use capacitors like this in their new fuel injected RMZ's instead of a battery.

They ARE much lighter than a battery and can provide a large amount of power for a short period of time. If you don't need power for engine-off (not running) accessories, like DOT compliant lighting, then this could be a great solution for kick-start bikes - even with headlamps and fuel-injectors.

I bet you'll see all the MX bikes using FI going to this setup.

With this said, you do not want to use this in your GS or KLR as it will not store a charge long enough for the e-button to power your starter if the bike is off for a few minutes.

PS - for those unfamiliar with these: cutting open a capacitor is not a smart thing to do if you don't know what you are doing. The unit you cut open looks like it is well insulated and protected, but if you touch the two terminals you could easily get a large voltage shock (lethal).

PSS - you need a voltage regulator for these to work. They just store gobs of power and really don't care if connected to a 12v system or not.
Actually Australian XRs all use what is called a DC voltage regulator with a capacitor - we have no requirement for lights on after engine off. So these things are still made by HOnda and do a great job
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