Batteries: what's the difference?

Question

I have Eveready batteries for electronic application, they come in different voltages like 15, 22.5 ets. What is the difference from regular 9 V duracell batteries, besides the voltage?

I need an 18 V DC source for 3mA current that would last for a long time. I know I could always experiment. I'm asking cause it's critical in my case that it won't die - a lot of stuff stops working and irreversible changes happen.

Can I assume that a larger (in physical size) battery will last longer?

Wow, didn't expect such detailed answers. Long time is 8 months. I don't have space or weight limitations. Well, I don't want it to be, say, more than 5 lbs.

Cirquit will stop working at 15 V. I don't want to exceed 20 V.

Answer 1

Batteries typically have two ratings. The voltage is easy to find. But sometimes you need to do some detective work to find the amp-hour rating.

A typical Duracell 9 V alkaline battery is rated for 580 milliamp-hours. Two batteries in series provide 18 volts at 580 milliamp-hours. At 3 milliamps, the batteries will last up to 193 hours at most. (probably less)

Your question is missing details of your requirements:
- How long is "a long time"?
- Do you have physical dimension or weight limitations?

If the second answer is "no", perhaps you'd want to consider wiring three 6 V lantern batteries in series. They're pretty big, but a standard Duracell 6 volt lantern battery has a capacity of 13 amp-hours. Three in series will provide 18 volts with 13,000 milliamp-hours. That's 22 times the capacity of the original two 9 V batteries.

In theory, your 3 mA load should operate for 13,000 ÷ 3 = 4333 hours. That's probably a bit optimistic, but even derating that by 20% still provides nearly 3500 hours.

I doubt the battery will hold a decent voltage near its "end of life". Depending on how voltage sensitive your equipment is, low voltage will probably cause the electronics to stop working before you drain the last amp-hours out of the battery.

>>>>> Update <<<<<

I weighed a 6 V lantern battery I had laying around. It weighs 0.602 kg. Three of these would weigh 1.806 kg or just under 4 lbs.

Another item to consider is the ambient temperature where your equipment will be operating. Hot temperatures kill batteries. Cold temperatures reduce the battery capacity. If your experiment is going to be exposed to temperatures over 90° F or below freezing, consider insulating the battery compartment.

Answer 2

Generally yes, the more physical mass generally correlates to more Amp-hours. When you say "long time" what do you mean? An hour? a day? a month? a year? 3mA isn't that much so 2 9V duracells would probably last a few days.

Also, does the voltage need to stay at 18V? Will your circuit still work all the way down to 0 Volts? As the battery drains the voltage will drop proportional to the amount of charge it has. So if you need the voltage to stay above say 12 volts you need to factor that into your amp-hour calcuations.

Answer 3

the kind isn't as important because the technologies, including Alkaline, Rechargeable alkaline, Nickel metallic Hydride (NiMH), Nickel-Cadmium (NiCad), Lithium, and Carbon Zinc/Zinc Chloride. there's a good chart outlining the version on the internet web site lower than. note: in case you purchase a 2-%. of length A23 batteries for type of $2 and open their casing, interior is 16 a million.5v button batteries -- a $40 2 fee, so that you would shop $40. See the 2d link lower than, which incorporates a video of the hack.

Answer 4

With our batteries of today you will not be able to draw 3mA for 8 months and still be 5 lbs or under, you could do it if you were talking around 200 lbs if lucky.

Answer 5

Battery voltage = # cells in series * V(cathode-anode)
V depends on the chemicals
V ~ 1.6V for alkaline battery
V ~ 1.5V for Carbon - Zinc
V ~ 1.2V for NiCd
A 9V battery is typically 6 small cells in series.
You can achieve 18V by connecting 12 typical batteries in series ( -B+ -B+ -B+ -B+ -B+ -B+ -B+ -B+ -B+ -B+ -B+ -B+)

Most batteries are rated in mA-hour, but it's often only printed on rechargeables. Yes, larger batteries (eg D-cell) have more mA-hour capacity than small ones (eg AA-cell)

Don't short circuit your batteries! The wire and batteries can get very hot very fast - battery can rupture

[I don't know what "ets" means]

Answer 6

No you can't assume that bigger is better. Better is better and may be smaller and have more capacity.

You need to talk to a professional or at least check the specs on a professional site. You want decent voltage but not much current, so you need to look at the discharge curves at somewhere like SAFT.

Answer 7

Thomas had some good advice, it looks like he posted before the "additional information" and when he talked about "lantern batteries" he used the square version at 13Ah, but one of his links leads to a rectangular version at 27Ah, three of which may do what you want, however they weigh 3lbs each, for a total of 9lbs, more than your 5lb limit but far less than 200lb. The would also cost about US $42 for 3 @ $14ea.
http://www.thebatterybarn.com/pages/store/skudetail.nhtml?profile=general&uid=10172&returnURL=http%3A//www.thebatterybarn.com/general

Where will this device be used? any chance of using solar cells and a rechargeable battery?

Answer 8

They make 18V batteries for power tools that have a long life and are rechargable. Sears, home depot etc.