incandescent bulb blowing. Over voltage?

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cygnusv

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Wheelhouse light. Saving the planet with a ten quid build? Tried that, Rubbish. So back to yer normal bulb. 1 week later, blown.
I'm wondering. My Trojan bank often runs at 29 volts (24 system). Could this explain why my lorry type bulb is blowing?
If this is the case, can I limit the voltage going to said bulb by adding a resistor? If this would do the trick please suggest to an amatuer what resistance and how to connect.
Many thanks. Stu
 
You could do this but it should not be necessary. A good quality LED unit would be better

To calculate the value of resistor required you need to know the power of the bulb in watts

Divide the power by 24 ... call the result I ( alternatively measure the current and call this I )

Divide 5 by I and call this R.

R is the largest value of resistor in ohms that you are likely to need. R/2 ohms will probably be adequate

You will need a resistor with a a power rating equal to I² r where r is the actual value of the resistor used
 
If it was a 25watt bulb then current is going to be aprox 1 amp. a 1 ohm rssitor in series will drop 1 volt or 2 ohm resistor will drop 2 volts. Power dissipated will be 1 watt or 2 watts so buy a wire wound resitor rated at 5watts (max).
A 10w bulb draws .4 amp so a 2 ohm resistor will drop .8 volt and 4.7 ohm resistor will drop 1.8v. ol'will
 
I would have thought a resistor would just give you a dim light most of the time and probably fail to protect against blowing when voltage spiked anyway. It might be interesting to put an oscilloscope on your lighting circuit to see what transient voltages are present.

I'd recommend something like a zener diode or similar voltage regulator protecting the whole lighting circuit if you were really intent on not using LEDs:
- https://www.electronics-tutorials.ws/diode/diode_7.html
- 24v regulator small and cheap enough to fit to each light.

Really my advice echoes those above - buy better LEDs - They do come in dimmable (really annoying because they fluctuate with the supply voltage flutter) and non-dimmable, different flicker rates, a wide range of colour temperatures and of course a huge power range.

What was your issue with the LED you had? Too bright/dim? Flicker? Too directional? Unpleasant or unhelpful colour temperature?
 
Filament bulbs blowing may just be vibration shaking them to bits. Does the roof of your wheelhouse vibrate when the engine is running?
Using resistors to drop volts is not a good idea, they get hot and risk fire.
Use a proper 24v regulator or better a 24v to 12v buck module and use 12v bulbs.
 
A good quality LED light is likely to be 10-30V. It'll also be a deal more resistant to vibration than a filament. If you manage to blow the LED, it's time to start looking seriously at your electrical system, because spikes that big are likely to take out expensive things like chartplotters
 
It's a little odd that only one bulb blows, if it's due to high voltage.

I have had a few installations where LEDs have got hot because the mains charger is on a high setting, especially when people have used cheap LEDs or those cheap Chinese LED strip. Sometimes, when the charger is on, they get so hot you wouldn't want too touch them. The answer is simple, fit a decent quality 24v-12v DC-DC converter, connect all lighting circuits to it and use all 12v LEDs.
 
what chargers are you running? do you also do equalisation on your batteries, or is the charger configured to do so automatically (some MPPTs are!)? what's the equal. voltage can be 31 or so iirc?
also I'd drop the abs voltage a bit so that the trojans are not such heavy water drinkers...
I noticed that I burnt a couple of solidstate float switches (grey water tank) and then matched that with lots of equal. testing to charge and test my Trojans using my Victron MPPT controller.
Haven't equalised them again since, and if and when I do, I'll turn off the 24V circuit first :-) just in case...

V.
 
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