Different types of D batteries?

[daviddoria]

I bought an electric lantern, put 4 D batteries in it, and turned it on expecting to see a very bright light. The first thing I thought was " oh, must be dead batteries". So I got out the trusty multimeter and check all 4 and they read 1.5v as they should. I was puzzled. I went to the store and got some more, put them in, and it worked fine. I measured the new ones and they also measured 1.5v. I measured the current through a 50 ohm resistor with both types and they both read 32mA. After closer inspection, the new batteries are Energizer D size-E95 LR20-AM1-1.5V and the old ones are Panasonic UM-1NP 1.5V. The Energizers say alkaline and the Pansonics say "Super Heavy Duty".

I'm assuming for some reason the Panasonics can't provide enough current for what the light is looking for.

1) What is the difference between these batteries ( I know "super heavy duty" is something besides alkaline which makes the life shorter, but how does that affect current output?)

2) How can I test for the max current these two types can produce? I used a 50ohm resistor so I don't think I could really use a much smaller one.

Thanks!

David

 

[Nigel Goodwin]

Stick your meter on the 10A range and place it directly across the battery, a good battery will probably read a couple of amps, a flat battery very little.

Only do this for a spilt second, and NEVER, NEVER, NEVER do it with NiCd, Lead Acid or NiMh - only smallish dry cells.

By the way 'Super Heavy Duty' just means they are absolutely rubbish, and don't last very long.

 

[daviddoria]

Ok I'll try that tonight.

I realize now it means they are rubbish, but doesn't it just mean they don't last as long? It seems that not only do they not last as long, but they wont even drive something like a lantern even when they haven't died yet?

Also, I still don't understand how they can read 1.5v but not make the light turn on?

Thanks,

Dave

 

[Nigel Goodwin]

Ok I'll try that tonight.

I realize now it means they are rubbish, but doesn't it just mean they don't last as long? It seems that not only do they not last as long, but they wont even drive something like a lantern even when they haven't died yet?

Also, I still don't understand how they can read 1.5v but not make the light turn on?

As a battery goes flat, the voltage doesn't really change, the internal resistance increases - which means under load the voltage drops.

 

[ecerfoglio]

Ok I'll try that tonight.
Also, I still don't understand how they can read 1.5v but not make the light turn on?
Dave

I noticed that some "D" cells, when they suffer some mechanical abuse, develop a high internal resistance and are incapable of turning a light on - but mantain a 1.5V open circuit voltage .

For example, dropping the lantern, if it hits the floor with its end, may cause this.

It happened with alkaline (Energizer / Duracell) D size cells, but I think it can happen with the "heavy dutty" cells as both types have a carbon rod central electrode. Y suspect that either the carbon rod breaks or it develops a bad contact where it joins the metal cap of the battery.

 

[mneary]

Please clarify: Did the Super Heavy Duty batteries light the lantern dimly or not at all?

I have had devices that didn't connect properly to certain brands of battery due to mechanical tolerances.