On Monday, 22 April 2019 13:48:22 UTC+1, Roger Mills wrote:
On 22/04/2019 10:42, newshound wrote:
On 21/04/2019 00:09, Fredxx wrote:
On 20/04/2019 23:32, Roger Mills wrote:

I have a Livarno Lux (Lidl) cordless spotlight - the sort with a
large diameter lens at the front, behind which is a powerful halolgen
(55w) bulb and a ring of LEDs, and with a white LED and flashing red
LED at the back.

It normally travels in the boot of my car in case of emergency, but
tends to roll around a bit - which may be related to the problem.

I recently found that it was completely dead - none of its 4 lights
would work. [You're supposed to charge it regularly since the battery
can apparently be damaged if it becomes deeply discharged. It was
working when I tested it 3 or 4 weeks ago, so it's possible that it
got turned on while rolling around (don't we all!) and flattened its
battery.]

I recharged it for over 24 hours, and the battery's open circuit
voltage is well above its rated 6v. Three of the 4 lights now work,
but the 55w halogen doesn't. I've tested the bulb on a bench power
supply, and it lights up ok - but in the lantern, nothing. It's
drawing several amps but not lighting - or even getting warm, so I
don't know where the energy is going.

55w at 6v equates to over 9amps, so the filament resistance is only
about 2/3 of an ohm when hot - even lower when cold. Any additional
resistance in the circuit will have a dramatic effect on the current,
and probably stop it lighting.

Question to those who are knowledgeable about rechargeable batteries
. . .
What sort of "damage" is likely to result from being discharged too
deeply? Is it possible that this could increase its internal
resistance? If so, is there any remedy - or is it scrap?

What's the battery volts when the halogen is turned on?

I'm thinking the battery is happy to power the LEDs but drops all its
volts when connected to a 'cold' halogen bulb with a very low resistance.

My thoughts too. Also, what sort of battery is it? Do you *actually*
need a spotlight? I reckon those "work" floodlights are usually much
more useful, they are LED and lithium ion and hence very efficient.
Could you replace the halogen with some sort of LED?

I only use the spotlight occasionally - usually when delving around in
dark attics - so I *can* manage without it. It has to be used sparingly
anyway, because it soon drains the battery. The ring of LEDs produces a
reasonable light - but nothing like as bright as the halogen bulb (when
it's working!).

The battery is lead-acid - 6v 4Ah.

One or two people asked about actual voltages - so I've done a few
measurements.

When on charge, the battery floats at just under 8v. After removing it
from charge, and waiting an hour or two, it settles at about 6.65v open
circuit. When either the side LED or rear flasher are on, it drops to
about 6.59v. Then the front LED ring is on, it drops to about 6.51v.

Those are all healthy voltages

When the halogen is switched on, the battery drops to 0.14v !! So, for
whatever reason, the battery is no longer able to deliver the 9amps or
so required to power the halogen bulb - and appears to have developed a
high internal resistance.

Could that be caused by discharging it too deeply? If not, by what else?
Is there any fix other than replacing the battery?

Battery knackered, obviously. Sitting around discharged is fatal to lead acids. It might be worth a go discharging it to about 3.5v then immediately pulse charging it. A variant of that method was used a fair bit back in the 50s to get car batteries good enough to sell the car. You need a charger with recondition mode of course - or could do it the old way, but those setups tended to be a hazard.


NT