Weird problem with batteries
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Andy_R
Hard of hearing..I said Herd of Herring..oh FFS..
- Location
- County Durham
^^this.They might have sufficient potential difference, but do they have enough charge to supply the required current?
Wobblers
Euthermic
- Location
- Minkowski Space
[QUOTE 4989736, member: 9609"]I was wanting to use 2 "C" batteries instead of two AAA batteries, but it will not work with the "C" batteries. The two AAA batteries are delivering 3.08v and the two "C" batteries are showing 3.1v. They are connected properly with the correct polarity but I just get an error light with the "C" batteries.
It makes absolutely no sense whatsoever to me - anybody got a clue what is going on ?[/QUOTE]
What's the battery voltage under load? Open circuit potential doesn't really tell you a lot about a battery's capability to deliver sufficient current. An old battery might have a high terminal voltage, but also a high internal resistance, so its output collapses under load. Check of your C cells work in something else.
It makes absolutely no sense whatsoever to me - anybody got a clue what is going on ?[/QUOTE]
What's the battery voltage under load? Open circuit potential doesn't really tell you a lot about a battery's capability to deliver sufficient current. An old battery might have a high terminal voltage, but also a high internal resistance, so its output collapses under load. Check of your C cells work in something else.
gbb
Squire
- Location
- Peterborough
Logically, as you say, it makes no sense....so as said, it may be (probably only one of ) the c cells. Try a different set.
This. You need to measure the potential across the batteries in circuit.
Salad Dodger
Legendary Member
- Location
- Kent Coast
If your batteries are run down, get them some multivitamins and a Berocca. That will perk them up.
gbb
Squire
- Location
- Peterborough
that's probably the problem then...connecting to an LED. I think I'm right in saying LEDs are at least equally dependant on current as well as voltage. you may well have the voltage but the current available probably just isn't enough.
Tanis8472
Guru
[QUOTE 4990284, member: 9609"]I think this is my next step; try some other batteries. The ones I'm using are well out of date (mar 2014) so they could be 12 year old or more. I have about a dozen of them and quite like to use them for my lights this winter.
They work fine on a torch with a traditional bulb giving a good bright light, but when connected to the LED rear lights they just flash rapidly (and brightly) when the on button is depressed but won't stay on when the button is released. Its doing my heed in cause it just makes no sense.
I might go and bury the dam things under the north pole sign.[/QUOTE]
Illuminated northern lights. I likr your idea
They work fine on a torch with a traditional bulb giving a good bright light, but when connected to the LED rear lights they just flash rapidly (and brightly) when the on button is depressed but won't stay on when the button is released. Its doing my heed in cause it just makes no sense.
I might go and bury the dam things under the north pole sign.[/QUOTE]
Illuminated northern lights. I likr your idea
nickyboy
Norven Mankey
- Location
- You want hills? We got hills
Wobblers
Euthermic
- Location
- Minkowski Space
[QUOTE 4990430, member: 9609"]as I said in a previous post to that, the batteries work fine in another device that draws more current.[/QUOTE]
It's not that simple. Your rear light most likely has a microcontroller in it. Unlike an analogue device, microcontrollers do not degrade gracefully when the voltage gets too low - often you'll see the sort of behaviour that you described. Worse, they tend to draw current in short but high pulses. An old battery will have a much higher internal resistance than a new one (even if it's unused): that will cause the voltage to briefly dip sufficiently to crash the microcontroller.
Measure the voltage of your batteries while they're running that old incandescent torch. You'll probably find that they're much lower than you thought.
It's not that simple. Your rear light most likely has a microcontroller in it. Unlike an analogue device, microcontrollers do not degrade gracefully when the voltage gets too low - often you'll see the sort of behaviour that you described. Worse, they tend to draw current in short but high pulses. An old battery will have a much higher internal resistance than a new one (even if it's unused): that will cause the voltage to briefly dip sufficiently to crash the microcontroller.
Measure the voltage of your batteries while they're running that old incandescent torch. You'll probably find that they're much lower than you thought.
