Thread: How long would it take for an interior light to flatten a battery?

Originally Posted by JDNSW

Could be a good argument for fitting an LED bulb in your interior light?

I've got these in mine. Should also make the covers last longer.

They are bloody bright though. If someone is sitting in the middle rear seat and you open the door at night the middle row light (Disco1) will blind them.

Regarding LEDs for interior lights, don't know enough about them to comment. However I do like the interior light bright enough to be able to read things at times. On my Defender have bent the globe holding terminals so they take an 18 watt globe instead of standard 10 watt and left the cover off. Regard it as just an unnecessary thing that causes trouble, reducing the light intensity and would probably melt anyway. eg As some taillights are prone to with more powerful globes intended for indicators or stoplights that are okay for intermittent use are run continuously.
Regarding batteries, I normally run 86's, which are slightly bigger than the standard one and commonly used in tractors and trucks. Takes a long time to flatten a good one from the interior light. Fortunately my 300Tdi starts very easily and using the glowplugs makes it quicker still. Can get away with using 86 batteries too old and sick to start tractors.

Don't know about all Defenders, but in our Td5, if you leave the door open, the interior light goes out after 8 mins.

If the batteries are manually isolated, I can't see the flatter battery discharging the good battery, as everything operates from the battery selected, and at all times is isolated from the other, unless of course the manual switch is switched to Both.

A handy trick for starting diesels that need to be heated before starting (not usually modern LRs) is to tip a kettle of hot water over the glow plugs before attempting to start with a low battery. This prevents the glow plugs from draining the last of the charge from the battery if you crank it as soon as you turn the key on.
A trick learnt with old farm hiluxes with dodgy batteries.
Direct Injection diesels such as TDI /TD5 usually will start without glow plugs anyway.

Regards,
Tote

I don't know what tipping hot water on the glow plugs will achieve. Do they have a temperature sensor in them, and the hot water will turns them off, hence saving power? But this will not significantly warm the engine, in order to ease starting. Diesels need heat in order to start, and if you are low on power, you could carefully try lighting a small fire underneath the engine. The heat warms the oil so that the engine will turn over quicker, and the heat buildup will aid starting. Alternatively, just warm the inlet manifold, so warmed air is drawn into the engine. Old Bedfrod diesel engines had a heater plug in the inlet manifold, and none in the engine. If you can push/hill start it, this will turn the engine over faster, and start it quicker.
Aaron.

Originally Posted by RonMcGr

Well, in a Disco, the light goes on when you open the door and then off about 5 minutes later if the door is not shut.

Originally Posted by numpty

Don't know about all Defenders, but in our Td5, if you leave the door open, the interior light goes out after 8 mins.

Not if you slide the interior light to ON while you are sitting in it. Only if it is on DOOR.

Originally Posted by Aaron IIA

I don't know what tipping hot water on the glow plugs will achieve. Do they have a temperature sensor in them, and the hot water will turns them off, hence saving power? But this will not significantly warm the engine, in order to ease starting. Diesels need heat in order to start, and if you are low on power, you could carefully try lighting a small fire underneath the engine. The heat warms the oil so that the engine will turn over quicker, and the heat buildup will aid starting. Alternatively, just warm the inlet manifold, so warmed air is drawn into the engine. Old Bedfrod diesel engines had a heater plug in the inlet manifold, and none in the engine. If you can push/hill start it, this will turn the engine over faster, and start it quicker.
Aaron.

Glow plugs don't warm the engine, the warm the fuel that is about to be injected into the cylinders. The hot water heats the injectors enough that the diesel ignites when the engine is first cranked.

Regards,
Tote

Originally Posted by numpty

Don't know about all Defenders, but in our Td5, if you leave the door open, the interior light goes out after 8 mins.

If the batteries are manually isolated, I can't see the flatter battery discharging the good battery, as everything operates from the battery selected, and at all times is isolated from the other, unless of course the manual switch is switched to Both.

I've managed to out smart this by switching it to ON in the back and leaving the car for a week. I swear I've never seen a battery as flat as the primary one after that...