Instructions for adding a battery to a Batavus

I've finally posted the insturctions for adding a battery to a Batavus. This system works, but if anyone can improve or find errors in my drawings please email and let me know so I can fix them as soon as possible. My web site address is http://www.geocities.com/miniengine . Once on the home page go to 'Moped Adventures' in the directory. Good luck and happy mopeding.

Brian

Lamborn's Miniature Engines

http://www.geocities.com/miniengine

Re: Instructions for adding a battery to a Batavus

Brian,

I checked out your site. Turns out I've been there before! Printed the plans and they look pretty much like what I had in mind. One problem...I don't have turn indicators or a brake light or even a coil for them. This has been confirmed to me by the original buyer. It never had 'em. It came of the showroom floor as it is now...minus a bit of dirt and scratches. The exploded views are going tho come in real handy too. Thanks for making them available.

Richard

Upgrade magneto

Richard,

Your welcome. Since your going to the trouble of adding a battery to your Bat., why not upgrade the magneto. It shouldn't be hard to find these old parts from places like The Moped Junkyard. The nice thing is that it's hidden under the flywheel so no one has to know your secret because you maintain the stock look. Never pass up an old junk moped because it may have parts you can use on your Bat. They used off the shelf parts for the electrical system and the switches for turn signals and the terminal blocks have the zener diodes and rectifiers that you can use for your battery charger.

Brian

Lamborn's Miniature Engines

http://www.geocities.com/miniengine

Re: Instructions for adding a battery to a Batavus

Ron Brown /

Brian,

Your charging circuit looks very similar to a typical "old" motorcycle charging circuit except that they typically use fullwave rectifiers as both ends of the coil are isolated from ground.

However, you do seem to have a couple of problems. The most significant is that the rectifier diode, D1, is installed backwards. This is not good for the alternator coil, at least if you install a fully charged battery pack. Incidentally, this should be a 25 volt diode.

The second problem is the placement and value of the zener diode. First, the zener is normally placed directly accross the battery. In this position, the battery acts as a capacitor, smoothing out the peaks of the charging voltage and the zener only begins to conduct when the battery terminal voltage matches the zener voltage. The zener, depending on it's specs, should be rated at the same or a slightly lower voltage than the fully charged terminal voltage of the battery pack.

Your placement of the zener in the circuit is clamping the charging peaks at about 6 volts and I think, sinking the negative half of the cycle to ground, as I believe a zener works like a normal rectifier when forward biased. Besides heating up the zener, there is also a problem with the forward voltage drop of the rectifier diode, which will vary with temparature and current flow.

I hope this helps,

Ron

Updated the circuit

Ron,

Thanks for the heads up advice. I used a turn signal module as my circuit and am trying to copy the components into the schematic. I've updated the circuit on the web site to reflect your advice. I'd suggest that everyone wait until Ron debugs the circuit and gives the all clear sign before using it.

Brian

Lamborn's Miniature Engines

http://www.geocities.com/miniengine

Re: Updated the circuit

Ron Brown /

Brian,

This circuit looks much better. For anyone who wants to try it, here are a few things to check.

Measure the battery charging current using an analog, dc amp meter at maximum rpm with a low battery and make sure you do not exceed the maximum allowed by the manufacturer. Too high a charge rate will at least overheat and damage the batteries. They may actually explode. You should be using a battery pack capable of supporting all of the lights anyway, which is a significant amount of current and should survive the available charging current.

Also, check the charging current with a fully charged battery and make sure it is low enough to not upset the battery. Probably less than 50 ma is ok. This can be adjusted using different value zener diodes.

The zener and rectifier diodes must be single units. Semiconductors vary slightly in specifications from one to another and if you parallel them, they will burn out serialy. You should check the temperature of these diodes in operation, if you can not hold them with your finger tips, mount them on a heat sink. If your diodes are stud type, held in place by a nut, then the current rating assumes mounting on a heat sink.

Here is a piece of random info I read in a friends ham radio magazine a few weeks ago that was news to me. Apparently this article was written after consultation with major ni-cad manufacturers and satelite manufacturers who use ni-cads exclusively for powering satelites during dark periods of orbit.

With the possible exception of single cells, never discharge ni-cads completely. Apparently, if you discharge a ni-cad battery pack to 0 volts, because the cells do not have exactly the same capacity, some will discharge completely while others are still providing power. The continued current flow through the discharged cells, charges them in reverse which is very detrimental. This also causes high initial charge rates when first recharging because the reversed cells are adding to the charging current.

Electronic equipment and "smart" charger/conditioners for ni-cads, sense when the terminal voltage of the battery pack drops to a certain voltage and cease discharging.

Now I know why my lap top's battery pack died precipitously after I hooked up a brake light bulb and discharged it til it was 0 volts!

I hope this helps. I think if I were going to try this, I would at least use a 6 volt gel-cell, which is a lot less sensitive to over charging and may not need a zener at all in this circuit. The charging current should still be tested as described above and a correct zener selected if necessary.

Now you know why I never answered this originally. I knew there were lots of variables in a circuit like this and I know I have not even covered them all here. Remember that without carefull testing of a circuit like this, it may seem to work ok for a while, but then begin to fail from over stressed components. At least with this circuit, you can switch back to the alternator and mo-ped back to the drawing board.

Ron

Re: Updated the circuit

Thanks Ron for the words of advice. You've hit so many good points that I'll have to go back and check to see why my system seems to be working. I may have a time bomb waiting to to go off. Your insight is priceless and I thank you for taking the time to help.

Brian

Lamborn's Miniature Engines

http://www.geocities.com/miniengine

Re: Updated the circuit

Thanks,Brian and Ron! You've talked this hillbilly out of tryin' it.It's just `too many' for me,as Mark Twain said.BYE!

Re: Updated the circuit

Hey Ron,

If it helps, I have built a simple ni-cad discharger that can not over discharge any ni-cad. As you know, diodes don't start conducting until a .6-.7 volt charge is placed accross them. I just used that fact to build mine. Works like a dream. This will save your batteries.

Richard

Re: Updated the circuit

It just gave me more resolve to defuse my time bomb. lol

Brian

Lamborn's Miniature Engines

http://www.geocities.com/miniengine

Re: Updated the circuit

Sounds good. Could you send it to me so I can update the circuit or I can send you a .dxf of my circuit so you can make the needed changes. I'd really like to see this project work.

Brian

Lamborn's Miniature Engines

http://www.geocities.com/miniengine

Re: Updated the circuit

Ron Brown /

Brian,

In oder to protect a 6 battery pack, you would need to limit the discharge to .6 volts per cell, this would give you an in-circuit voltage drop of 3.6 volts and you still would not have guaranteed that none of the cells was reverse charged.

The "discharge through a diode" trick only works for off line discharging and really only for single cells. The clever battery pack dischargers sense only a small decrease in voltage before turning off.

Ron

Batteries

Ron,

I removed the 6 C cell Ni-Cad pack and am going to replace it with a 6 volt gel cell. This is a feasible project and I'll continue tinkering until I get something more stable. Thanks for pointing out the facts of electronics because this is helping steer me in the right direction. I think I'm going to do some research on motorcycle charging systems and see if I can't get a module that fits the bill.

Brian

Lamborn's Miniature Engines

http://www.geocities.com/miniengine

Re: Batteries

Ron Brown /

Brian,

Using a gel cell should resolve your problem. Just make sure your zener limits the charge rate to less than 100 ma when the battery is fully charged.

As for using a motorcycle charging module, the closest to a "real" regulator that I am aware of that does not require variable excitation for the alternator uses scr's, similar to a lamp dimmer and is designed for a 3 wire alternator.

Your circuit is essentially the same as old motorcycles used to use except that they did not have one end of the coil grounded and used a full wave rectifier.

Ron

Full wave rectifier?

They use a full wave rectifier, huh? I have an idea I'd like to run by you. Take a look at the wiring diagram for the Batavus on my web page. Do you notice the GRN/BLK wire coming off the other side of the brake light coil? What would happen if I tapped this side and instead of sending it to ground, used a full wave rectifier. Would this be better? Yes/No, Pros/Cons.

Brian

Lamborn's Miniature Engines

http://www.geocities.com/miniengine

Re: Full wave rectifier?

Ron Brown /

Brian,

This would work if you could get rid of the connection direct to ground on that same coil.

Ron

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