On off car battery switch - cable length?

[dmxtothemax]

The amount of power used by a cars clock is so small it is not even worth thinking about, consider this a watch can run off a tiny little battery for over a year. now how much bigger is your car battery ? They must have better ways of protecting batteries from the cold.

 

[Dubman]

I know we're talking about very very little drain on the battery. Just thought that if the car is parked in the same spot for 4 days at a time, then disconnecting the battery might make a difference. To be more precise, this parking spot is in a free public parking with around 200 other cars, and many of the parking slots are under a roof, although semi-open air, while other parking spaces are not under a roof.
I do have the battery in a lightly padded battery jacket, and even thought of adding a second jacket on top of that since it's kind of flexible material and should fit.
Other than that, do you think a new battery would be better at resisting sub-zero temperatures?
On the question of a smart trickle charger, I wouldn't be able to plug it in anywhere in the public car parking facilities. Thanks

 

[telectrix]

just buy a thermal blanket. put over engine and battery. remember to remove before starting.

 

[Squid]

I have one of these fitted to my E30, https://www.amazon.co.uk/Richbrook-1000-01-Discarnect-Immobiliser-Battery/dp/B0019ULCPW

 

[Lucien Nunes]

Anything connected in series with battery leads will degrade starting performance at least very slightly, by adding resistance to a circuit that has to carry hundreds of amps with very little voltage drop. Low-cost battery isolators do work, but can be prone to excessive resistance. If you do want an isolator, make sure it is a good one, use nice heavy cable and make the connections properly (e.g. proper crimp lugs crimped with the right tool). High resistance can also decrease charging performance (where the maximum permissible drop is in the order of 0.1V). Also note that some electrical systems can be damaged if the battery is accidentally isolated while the engine is running.

An ordinary relay is not the way to go. Because of the heavy starting currents it must carry, a contactor or relay large enough for the job uses too much power for its coil for it to sensibly remain energised all the time. Accidentally failing to isolate when you leave the car would result in returning to a flat battery.

There are electrically-operated remote latching isolators. These are used in commercial vehicles and are ideal for the job but they are expensive and overkill for your car. They only consume power while changing state from on to off and back again, not continuously, and they can be interlocked so that they will not switch off while the engine is running. see
https://cdn.shopify.com/s/files/1/0658/7343/files/ELBs.pdf?817

The best way to maximise starting and charging performance is to fit the largest, best battery that will fit the space, with an intelligent alternator controller if one is not already fitted. A larger battery scores in two ways - first, there is more capacity to serve low level background loads, which would otherwise be saved by the isolator. But when you come to start the engine, the battery has lower resistance and can deliver the starter current with less voltage drop, so even if the same percentage of discharge has occurred, the starter will get more volts for longer before the battery starts flagging. A 25% increase in capacity can make a very noticeable improvement in starting performance.

 

[Dubman]

Good information! Now I'm thinking of just adding a second lightly padded special battery jacket if it fits, which I think it should. I think my battery is about 2,5 years old. Thanks!

 

[dmxtothemax]

car batteries for cold climates - Google Search - https://www.google.com/search?client=firefox-b&q=car+batteries+for+cold+climates

 

[Deleted member 26818]

Personally, as soon as a vehicle fails to start when the weather turns cold, I replace the battery.

 

[Dubman]

Changing the battery if the car fails to start due to cold weather is my present plan. Thanks.

 

[Squid]

Personally, as soon as a vehicle fails to start when the weather turns cold, I replace the battery.

You've never owned a Lotus lol.

 

[brianmoooore]

The flashing red light. Not an alarm by any chance?

 

[LightGEN]

Most modern vehicles have an insulating jacket around the battery to give it a degree of protection from the cold.
Assuming the car is 'fairly' modern, the integrated alarm/immobiliser will place a constant load on the battery - that's likely going to be the greatest source of drain. In the real world it should be possible to park a car for a couple of weeks without the battery becoming drained to the extent that the car can't be started. If you find that it doesn't last that long, it may well be a sign that the battery should be replaced - failure to hold charge in the cold being a warning sign ....however, it's also possible that that's a fault in the vehicle. I experienced a battery discharge problem in an E39 BMW 5 series a few years ago - turned out to be a faulty temperature control device in the heating system, which caused the ventilation fans to run at random while the vehicle was parked - cured the problem by replacing what is referred to as the 'hedgehog'.