Flashlight Project: need some help please.

[jerrymrc]

You should be able to put your multimeter across the battery terminals and see what it's milliamps are, right? I'd suggest winding for 60 seconds, check the mah across the terminals, write that down, repeat until the you're close to 900?

It's been a long time since I've done electronics though.

Reading Ma needs to be in series. If you disconnect the + from the battery then insert the meter with the lead's inserted in the Ma holes and it set to Ma. + lead on the meter goes to the +lead coming from the generator and the - lead goes to the battery.

Like this.

[Irving]

So the negative lead goes to the plus side of the battery. This is measuring the Ma of the battery, or is it measuring what the generator produces when turned?

[jerrymrc]

So the negative lead goes to the plus side of the battery. This is measuring the Ma of the battery, or is it measuring what the generator produces when turned?

Yes +-+-+-

Voltage is potential, current (amps) is work. If you measure across the battery on volts all you see is the potential to do something. If you put the meter in series and are not cranking it or have the lights on it will show zero. If you crank the generator and still see nothing that is because the battery is/has not completed the circuit

I need help figuring out a way to measure the charge of the battery, and to figure out how to make sure that this battery is charging when I turn the handle.

If you crank the handle and you get a 100Ma reading then the battery is taking the charge because the circuit has been completed and work is being performed IE the battery is being charged.

Hope this helps.

[Irving]

Well, I went to take some pictures of various readings, and touched the leads and now the meter isn't working. Did I just blow a fuse? I guess I'm done wishing I was McGyver for tonight. I'm going to go do some searching over the next few days and touch up on the basics of electricity and circuits.

[jason303]

Just as you would measure voltage at the terminals for a household dry cell battery, such as a 9-volt or AA 1.5 volt battery, you would measure voltage from your cell phone battery likewise. Leave the flashlight on a while and the voltage will slowly go down. If cranking the handle raises the voltage on the battery, then your setup is working. From what I can see on your photos, you set your voltmeter to AC voltage. Use a DC voltage setting instead. AC comes out of your house electrical outlets; DC comes out of batteries.

Note for all: Use your voltmeter (set to DC volt) to test batteries after your flashlight, kid's toy, whatever dies. If the battery voltage is less than 85% of what it should be, replace it. Often an gadget that takes four batteries will fail after only 1 or 2 batteries lose their charge. Don't throw out the two good ones!

[Irving]

Thanks for the tip on the voltmeter, I tried both settings, but used the AC setting for the picture I took. I'll have to fix my voltmeter and try it again.

I noticed that if I put the leads on the button battery, the needle would slowly, but very visibly, go down the whole time I held it on there. When I held the leads to the cell battery for a long time, the needle never moved. Also, I've been messing with this flashlight all day long and none of the readings have changed at all, no matter what I've done.

[jason303]

I noticed that if I put the leads on the button battery, the needle would slowly, but very visibly, go down the whole time I held it on there. When I held the leads to the cell battery for a long time, the needle never moved. Also, I've been messing with this flashlight all day long and none of the readings have changed at all, no matter what I've done.

My guess is that those little button batteries have a very small fraction of the capacity as the cell phone battery so it'll take alot of flashlight shining to drop the voltage of the cell battery. If that is the case it would take a lot of cranking to charge it back up. Attach a windmill to the crank and get some stimulus money.