12 volt bulbs blowing.

A 12 volt battery needs more than 12 volts to charge it. 13.8 volts is the usual charging voltage for automotive batteries and car lamps are designed to cope with that. ( They are noticably dimmer when the engine isn't running). Domestic bulbs are designed to work at 12 volts and

What type of charge controller does the panel have?

Bad batch of bulbs. Not really anything else it can be, unless youve got them in enclosed fittings. Odd that youre only getting 12v at the bulb sockets, your batteries must be half flat, or the wiring too thin.

NT

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Yes. I too think it's a problem with the bulbs. Why do you think I should be getting more than 12 volts from the sockets ? I am getting the same connecting directly to the battery. It is a 12v battery.

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It will until it's fully charged. Without a charge controller, it will then attempt to overcharge the battery. Most SLA batteries will start degrading quite quickly when this happens -- electrolyte dry out, and/or battery swell and split. They do have a catalyst to recombine the hydrogen and oxygen, but I don't think they are designed to handle the volumes generated by over charging gassing. There may be SLA batteries specially designed for this purpose.

Fit Lad Berkshire has brought this to us :

Perhaps the lamps are designed for an actual (or exact) 12v, as would be supplied by a transformer - rather than a batteries 12v?

A fully charged 12v battery, not actually being charged at the time of measurement, should show around 12.6v with no load applied. A battery charging towards the end of its recharge cycle should show around

How accurately are you able to measure the voltage - the numbers after the decimal point are important?

fit a regulator on the output anyhoo, DC-DC convertor should do you know the bulbs are being fed by a regulated supply then, What is the voltage at switch on, does it surge?

True, but with a 10w panel and 2 bulbs, or a battery reading 12v it sounds like its not getting as far as fully charged. And it'll only be used short term. Also absence of any controller is ok longer term if charge rate is less than C/?, where I cant remember ?, but 10 or 20 iirc.

NT

NT

If the output of the panel is 16volts and the voltage of the battery is

Harry it's just an old multimeter I have. I set it on 25v setting, and the needle goes just under half way across. I have now ordered a couple of caravan lights to see how they go. It says they are tolerant

No surge mate. Where would I get such a regulator ? Do you know of a site in the UK I could order one from if the caravan lights don't work ?

Sommat like this would do the job, this will only supply 30watt but if you call the RS helpline (usually very good) they might point you in the direction of a higher power version :-)

Big guns here !!

Did the OP meant 16v across the cells when _not_ connected to the battery? If so then the 4v would be lost in the internal resistance of the cells plus that of the cable, not just in the cable. Phil