Re: Lithium ion and battery charger
- From: Tim Auton <tim.auton@xxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Sat, 12 Aug 2006 00:40:23 +0100
On 2006-08-09 22:59:15 +0100, d_scotland@xxxxxxxxx said:
q1[snip]
Whats an easy way to turn my 7.2 V li into 6v to power some bike
lights, other than making a resistor based voltage divider?can you buy
some kind of inline product or an Ic for variable voltage?Am not that
technically proficient, so some easy suggestions would be good.
Q3
Am thinking of hooking a 12v dynamo(bike) to my battery charger(Maha
Mhc777plus). The charger is designed to take voltage from 12 - 24 from
5 to 20 W solar panels( of up to approx 1A).If my Dynamo exceeds this
current at maximum revolution will I need to regulate the current?
The folks in sci.electronics.basics will be able to offer some advice on q1 and q3.
The short answer to q1 is: a single in-line resistor is likely adequate (this would make half a voltage divider, the other half being your lights), the value (resistance and power rating) being dependant on the current your lights draw. The fancy solution is a 'voltage regulator' IC. This would be major overkill for most lights, which are very tolerant of the voltage variations a regulator is designed to smooth out, but it may be a reasonable solution if your lights have variable brightness (ie variable current draw, which would mean variable voltage drop across a simple resistor). You'd need a 'low dropout' (LDO) type, as the difference between the input and output would be well under a volt at the end of the battery's discharge. They are easy to use: A couple of capacitors and perhaps a heatsink is usually all you'd need in addition to the IC. Voltage regulator ICs are cheap (a couple of $US for one that'll handle 2A) and easy to use, but not nearly as cheap and easy to use as a resistor.
Tim
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