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UltraTec MS-5131 Automatic Emergency Light


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So I've had this camping / backup light for a year now, and i know quite a few people who have the same one, Id bet there are many many people who have it as you can get them from just about any outdoor shop. you may find this info useful. 

So the light died and after some investigation i found the battery inside to be dead and bone dry. i got a replacement battery and put it in and the light is fine, no big deal right. but after snooping a bit i found a shocking thing my new battery was being charged to 8.46V which is 2.82V per cell! Whaaaaaat?

I thought there must be something wrong with the charging circuitry, and checked some more.i mean this is obviously the reason for the failure of the previous battery, its being boiled to death gassing and venting with those high voltages.

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The charging circuitry is only one diode providing a +-0.6V drop, directly from rectified output of the transformer :o

From there the battery voltage is distributed to the switch which has 3 positions, center position is no connection so no luck of there being some current sink on the other side to regulate battery voltage, the other two positions lead to led's that are sink'ed through 2 bjt's individually, nothing else.

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So what this means, the charge voltage of the battery is dependent on the input voltage from mains power, its unregulated and a completely rubbish way to charge a battery. It is a shameful cheap-out and/or a product designed to fail.

my recommendation is don't get one, and if you have one don't leave it plugged in even though its a emergency backup light. charge it up and when you guess its full enough unplug it.

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Hey Weasel you are opening a new world for me. I have recently bought an Led motion censor light, Euro something.. problem is sometimes switches on and stays on the hole night sometimes it does not switch on at all, then again sometimes it keeps burning quite late into the day before switching of. I have played with the sensitivity adjustment, Lux adjustment, and time adjustment but do not get a consistent response

Anyone with some advise or ideas?

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Hey Green Bum, that some very random behaviour. If I had to guess its more likely to be the sensors position than anything to do with mains voltage fluctuations. Those lights will at least have a zener or something as a reference voltage for the sensors. The usual culprits I guess are that the light itself triggers the sensor or blinds the motion sensor thermally in some way. So if its position can be adjusted take it as far away from the light source as possible. The other possibility is moisture ingress. That always has a way of making things act really weird.

Sent from my SM-A500FU using Tapatalk

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I ended up whacking in another 3 diodes in series for the "Charging circuit" the voltage is now at a more respectable 7.2 @ the current mains voltage of 237. it should last a bit longer now, maybe throw in another one, it should actually be 6.5-6.9v for standby use.

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15 hours ago, Weasel said:

So I've had this camping / backup light for a year now, and i know quite a few people who have the same one, Id bet there are many many people who have it as you can get them from just about any outdoor shop. you may find this info useful. 

So the light died and after some investigation i found the battery inside to be dead and bone dry. i got a replacement battery and put it in and the light is fine, no big deal right. but after snooping a bit i found a shocking thing my new battery was being charged to 8.46V which is 2.82V per cell! Whaaaaaat?

I thought there must be something wrong with the charging circuitry, and checked some more.i mean this is obviously the reason for the failure of the previous battery, its being boiled to death gassing and venting with those high voltages.

The charging circuitry is only one diode providing a +-0.6V drop, directly from rectified output of the transformer :o

From there the battery voltage is distributed to the switch which has 3 positions, center position is no connection so no luck of there being some current sink on the other side to regulate battery voltage, the other two positions lead to led's that are sink'ed through 2 bjt's individually, nothing else.

So what this means, the charge voltage of the battery is dependent on the input voltage from mains power, its unregulated and a completely rubbish way to charge a battery. It is a shameful cheap-out and/or a product designed to fail.

my recommendation is don't get one, and if you have one don't leave it plugged in even though its a emergency backup light. charge it up and when you guess its full enough unplug it.

Most of these emergency lights and camping lights etc. etc. have chargers similar to the one mentioned here.  I have not come across any one of them having a decent / half decent charging circuit.  They are designed to be as cheap as possible and to only last for the warranty period. :) The worst I've seen was a Eurolux emergency light (twin 2 feet florescent) - transformer, bridge rectifier and a 5W series resistor directly connected to the battery.

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Yea it's unbelievable really, I actually have two of these and I thought I'd check up on the other one ant then realized it's actually trying to charge it up to 12.8 that's feken gerbege. I'm considering doing a bjt and a zener to step it down right or to just let it be.

Sent from my SM-A500FU using Tapatalk

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By the sound of things, there is enough voltage at the top to put in an LM317 voltage regulator. If it gets it up to 8.46, then you can get up to 8.46-1.25 = 7.2V with the regulator in place. Now a good float voltage is only 7V, so that is ample, and it is a bit more accurate than a couple of diodes.

Making a good float circuit with a zener and a thyristor is not difficult. I had one... somewhere...

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  • 3 years later...

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