Understanding watts available in miniature batteries?

Question

I am doing a project with some small miniature incandescent light bulbs (like a CM7333).

Sorry for not providing more links, the system will only allow 2.

The power source is a E11A battery.

The issue I am having is the bulb is not bright enough. We need to basically double or triple its current light out put or lumens. Theses bulbs are rated in MSCP. something Candle Power I presume.

These little bulbs are available with different amp, volt, and MSCP ratings, as precribed in this [chart][3].

Ok, so it would seem a simple matter of getting a bulb with an increased amp rating or filament design (I want to use the same battery in my design, which is 6v) so the total watts is higher and hence the bulb will burn brighter. From the [chart][4]

I could say grab a CM3150 which indicates a MSCP rating 3 times higher than the current bulb I am working with, for the same Volts and amps. I assume it brighter because the filament is a lighter duty design, which burns brighter. At least that's my way of wrapping my mind around it.

This were I run into my question or were I need some education. These little batteries seem to have some kind of current limiting capability or attribute. I have reviewed the technical data but its not clear to me how many amps the battery can supply.

I don't know how to properly determine how many amps my little battery will provide. I know it says "38 mAh to 3.0 volts", but I dont know how to properly apply that. The data sheet also states the drain as ".5 mA continuous", if I ma reading it correctly. Does that mean the battery can provide .5 mAs. or .0005 of an amp? Is it saying HALF a miliamp? or half a amp? half an amp sounds like a lot and half a milliamp sounds tiny.

So, in closing I hope I asked my question in a way that can be understood. Basically, I need to understand the maximum out put of that battery in even divisions of the amp. Like my bench top power supply. .01 .357, etc. Do these little guys have a current limit over time. I don't think they can discharge all their energy in a second... I think its the current limiting that is preventing my bulb from burning brighter... I dont know

Thanks, Robert

Answer 1

It is not that the battery has a hard current limit built into it. It has internal resistance which decreases the voltage output depending on the current drawn. It is not a simple linear function, but that is what limits the current available.

To make the bulb brighter, you need to increase the current flowing through it, which means increasing the voltage at the terminals. If you are on the steep slope of your battery, putting two in parallel will do that, as each is supplying half the current. If you are at the low current end of the curve, you are already getting (almost all) the voltage your battery can supply. An easy check is to measure the open circuit voltage of the battery, then measure it again with the light bulb attached and drawing current. If the second measurement is significantly lower, a larger battery of the same type or another battery in parallel will help. If not, you need a different bulb or another battery in series to raise the voltage.

Answer 2

If your battery says: 38mAh to 3.0V it means it can supply 38mA during an hour, or 76mA in half an hour, or 19mA during two hours. If you draw only 1mA, it will supply you 38 hours of service. Consider those ratings apply to a measurement where voltage drops a certain percentage, and usually varies according if it is rechargeable or not and what type of battery is. The 0.5mA continuous it means it was proven to supply 38mAh using a 0.5mA draw. So it ran 76 hours draining at 0.5mA

NOTE: Just checked the datasheet, didn't realized it was linked. Be careful to decide what voltage are you willing to operate your circuit. The battery's voltage drops dramatically when it reaches 4 Volts. I thought your battery was a 3V battery.

Batteries have an internal resistance. That means that the more current you draw, less voltage will be available at its leads.

Check your bulb current rating. Have you tested it with a bench power supply? Is it bright enough? If the bulb is now glowing enough with the battery, it means that your battery has a high internal resistance. If you want to still use this battery, you need to put more batteries in parallel. This will maintain your output voltage and increase the available current (and Amp-hours too).