Quote:
Originally Posted by Christ
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Still debating on whether to use the batteries for something, or just sell them to someone who will use them.
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Hold on to them for a week. I have a kludge, a somewhat inefficient circuit, that I could test one of mine with. It would NOT be pretty but it might work. I think I've got the parts in my junk box.
You want to be able to start the bike with the NiMH modules, right?
For those interested, the kludge uses a forward bias Si rectifier to drop 1.2 V from the nominal 7.2 VDC B+. But in reverse, an adjustable LM317L is biased to provide no more than 7.9 VDC charge voltage. Empirically, I've seen a little over 8 VDC has the peak voltage these units should ever see. Meanwhile, the rectified alternator is tied to the vehicle 6 VDC supply to supply bulk power for lights and horn.
The theory of operation is:
- normal operation, engine off - whatever load flows through the rectifier runs the lights at ~6 VDC while the NiMH battery (hopefully) floats up in the 7.2 VDC range. About 20% of the power is wasted heating the rectifier. This mode should be as brief as possible.
- normal load, engine running - the vehicle B+ load is provided by the directly attached alternator, thus helping the NiMH stay unloaded. The rectifier prevents unregulated flow back into the NiMH that can generate excess gas.
- starting - the starter B+ side lead is directly connected to the NiMH battery. This avoids having to size the rectifier to handle starter current load.
- reverse bias LM317-type regulator - biased to provide no more than 7.9 VDC to the NiMH module, this will keep the NiMH modules under the 8.0 VDC that seems to be the peak voltage for these modules. This can be tweaked down to 7.8 for a little more safety margin. It won't be a 'fast charge.'
In practice, you'll want a higher power, adjustable voltage regulator but these parts are available from Radio Shack (not the best source.) I've got them in my junk box and a 6 V battery charger. I can at least test the theory of operation.
You'll need to figure out the maximum current draw by the lights, turn signal and horn. Does your bike have one or more fuses identified for specific loads? Whatever the fuse current rating is will be your rectifier current load limit.
Understand this is a KLUDGE as in a McGyver type circuit. It is just as likely to fail due to things we don't know about your bike alternator and loads. Also, it is not terribly efficient, the rectifier and regulator will need a heat sink.
Bob Wilson