Temperature Monitors

As I’m working from home and walking the children to school my car isn’t getting much use at the moment. I’ve got an 18 month old AGM battery in it, but it will only keep the car going for about 3-4 weeks. I’ve just got back from holiday to find it was completely flat, so had to open the door with with the key to get at the Bluetooth ODB2 dongle so I could read the fault codes from the wife’s car (extra £’s needed in the fuel injection). That reminds me, I better check if its finished charging now.

I’ve just thought; I’ve got a Pi in the garage and as the ODB2 dongle is powered all the time (probably why the battery goes flat so quick), I could use that to monitor the battery voltage, and put it on charge before it drops to far. Trouble is I’ve completely flattened it about 4 times, which has probably knackered it already.

Trouble is I’ve completely flattened it about 4 times, which has probably knackered it already.

If it holds a charge and can dump enough to crank the engine, it will do (for now). Just don’t let it go too far in the future as there is likely some degree of internal damage.

I speak from experience. I wanted to run the engine of mom’s car about once a month, and usually had to put some charge into the battery first.

Until one day, it wouldn’t go above 8.4V (and trying to make it do so created quite a bit of heat). The battery is junk, replacements are about €60 for a cheap one, so I’ll just jump from my car for the time being.
Anyway, had I known beforehand I’d have kept a closer eye on the battery and kept it charged. But, you know, when it’s in a car that’s being used, it can sit there for many years and just “work” so it’s easy to overlook. Lesson learned!

Actually pretty easy unless there is really something badly wrong with the design of the VW.

Getting in is fairly easy (though the car is old enough to need a real key to be inserted into the steering column and turned in order to start; I’m not sure how that translates to a “keyless” model). The fun stuff was the sequence needed to make the alarm happy when the battery was reconnected (“Someone’s in the car, and I didn’t let them in with the central locking! Help! Panic!”) and pacify the immobiliser.

Oh, and then the real pain comes the following winter when, as the weather gets cold, the now unhappy heavy duty “stop-start” battery decides that after what was done to it earlier, it really doesn’t want to play any more.

Until one day, it wouldn’t go above 8.4V (and trying to make it do so created quite a bit of heat). The battery is junk, replacements are about €60 for a cheap one, so I’ll just jump from my car for the time being.

In my case, it went from “fully charged and happy to start the engine from cold” in the morning, to “no visible life on the dashboard” in just four hours sat in the car park at work. A jump-start from a colleague was followed by a very careful drive to KwikFit for a new one.

Might pay to have a good trickle battery charger if power is available.

Or perhaps a sun powered charger that plugs into the cigar socket.

I wonder how long Electric Car batteries last – when not used a lot.

Calling out the AA RAC – for a Electric Car’s flat battery has a totally new meaning.

Going by Laptop batteries life span.

Or perhaps a sun powered charger that plugs into the cigar socket.

My feeling is that if your battery’s good you don’t need it, and if your battery isn’t good it won’t be enough.

I think a solar trickle charger would make up for the drain from the alarm and the dongle if parked outside. However, my car tucked away safely in the garage. It does have a south facing door with a translucent panel, but I’m not sure it would be enough light to give sufficient power from the panel.

Motorcyclists have had this problem for sometime – if you have power in the garage – you could try a trip to a motorcycle shop – they should have a range of chargers – one might fit your situation.

Plenty of power, but I just need some sort of trickle charger that doesn’t involve leaving the bonnet or a window open all the time. What I need is a mag-safe like connection for cars, so it automatically disconnects as I back out of the garage,

And recouple when you return the car to the garage.

A job for a Pi?

I think a solar trickle charger would make up for the drain from the alarm and the dongle if parked outside.

(I’m assuming also the drain from the receiver that responds to the remote in your key/fob.)

For sure, if your battery’s good (no internal drain of any significance) – but only relevant if you’re not using your car for months. And it doesn’t take much of an internal drain in your battery to overwhelm anything produced from one of those little (0.06m^2) solar panels.

Obviously if you’re thinking of a square metre or more of panel then things are different, but that’s not going to sit on your dashboard. Maybe on the roof rack…

Edit: ah – what dongle is that? That might change the picture…

I was thinking under the rear window, it’s a bit like a under a magnifying glass when the sun is out, and large enough to put a fairly decent sized panel. It’s not a hatchback, so wont have to move. I’d have to wire it in to the car somewhere as the lighter socket is disconnected when the ignition is off.

It’s an OBD2 dongle, I’ve just bought another one for her car for £7.99, it’s a slightly later model and comes up with 5 fault codes for the garage to charge for with glee.

It’s an OBD2 dongle,

I think I liked cars when diagnosing a problem starting the car meant popping off the distributor cap to make sure it was dry and shiny inside…

I think I liked cars when diagnosing a problem starting the car meant popping off the distributor cap to make sure it was dry and shiny inside…

Only work on those bits if you have the car keys, otherwise you end up annoyed and offering to insert the keys and other objects into the nether orifice of the person who does have the keys.