OBD2 Solar powered battery chargers?

B0bbyEwing

https://forums.moneysavingexpert.com/discussion/comment/81978419#Comment_81978419

Thanks Goudy.

Few things - when I initially tested, I didn't know I was doing it wrong. The fuse box is right in the drivers door area (MK5 Golf) & so you need the door open. The initial video I watched on how-to didn't mention latching the door tricking the car in to thinking its closed. So that was time wasted. I can only go off the info I'm watching & if it's lacking then it's going to go wrong.

So latched this & it didn't make a difference. I forget what else happened now, I think perhaps we'd not latched the bonnet, just had it open.

Oh and when connecting the multimeter to the battery, that was another issue - one video basically just said probe here & probe there which is what I did but then later on when I started looking at other YT videos they were showing basically putting the probe on & keeping it connected throughout the lead disconnection process.

Can't remember if we re-tried after that or not. It's been a couple months or so now & on that particular day time was getting on (and I think it said you need to leave your car sat for a while for everything to power down - so didn't have time).

Regards head units - no, it's the standard one & all throughout the previous owners (relative) ownership (since 2017) they never put aftermarket in.

If I remember right the radio needs the ignition on but the 12v socket doesn't - but I was always disconnecting from there every time I parked up.

B0bbyEwing

https://forums.moneysavingexpert.com/discussion/comment/81978420#Comment_81978420

Ah you're probably getting different cars mixed up which is understandable as in the past year I've ended up with a few.

This car in question I never hardwired the dash cam because the plan was to not be keeping it too long so I didn't want to go through the faff of an install - so I was just connecting it at the 12v socket & then disconnecting it each time I parked up.

B0bbyEwing

https://forums.moneysavingexpert.com/discussion/comment/81978539#Comment_81978539

Yeah fair enough. That's why I was posting because I didn't know whether it'd work or not & I knew people here would know much more than me (which is nothing on the topic!).

Also I'm well aware it'd be a bodge. Like with the dash cam, if I was keeping the car long term I'd do a proper job but as I'm not planning on having it in 12 months I don't want to put too much time/effort/money in to it.

Even this draining isn't the end of the world because I get a couple days safety net if you will. Some may say well why are you bothering to ask about it then if it doesn't matter - and obviously I'd prefer to get it sorted if I can and if I can cheaply or free, but if I can't then using it daily is as mentioned earlier - a sort of bodge.

Goudy

You want everything off, so if a door is open there's a good chance the interior light it on and pulling power.

Some cars electrical circuits are inhibited. This means they stay live for a X amount of time after the ignition is switched off. If you're does this, wait awhile. (you may notice a relay click when it powers down)

Just undo one battery terminal, I always use the negative one and bridge the gap between the terminal and lead to get an amp reading.

Don't ever probe both terminals of the battery when the meter is set to amps. This will effectively short the battery out and shove all it's amps down the meters throat. You'll melt the cables to the meter and probably ruin the meter as they usually can't handle those sorts of amps.

Once you have a reading, take around 0.05 amps off it as that's what a modernish car would pull anyway so you have rough figure of the drain.

Now if you start to take each circuit by removing that circuits fuse and check the amps again, you aren't looking for that 0.05 amp drop, but the bigger one.

The main reasons I find for drains are abuse, like wiring up devices like head units wrong.

Glove, boot and vanity lights behind the sun visors.

Stuck/duff relays that won't power down.

Although I have never experienced it, I believe failed diodes in the alternator can cause it as well.

B0bbyEwing

Thanks.

Currently in a situation where I'm unable to test the car but I'll get it done when I can & see what happens.

The one thing I did notice though was these guys in the videos had multimeters running to 3 decimals whereas mine is just a cheapy & only runs to 2dp.

WellKnownSid

2dp should be fine.

As stated, don't put the probes across the battery terminals, I once knew a sparky that almost lost both testicles sticking a multimeter across two phases of a 1600A fused busbar… we banned all multimeters from site soon after - and to be fair they should be banned for both DIY and professional use for that very reason!

Goudy

You usually get a choice of amps and millamps. Either should give you a reading but milliamps are useful when pulling fuses as some circuits will have a low draw (that make up that normal 0.05 amps).

You say the head unit is standard factory but does it and the electric windows power down when the ignition is turned off after 30 minutes or so?

If you leave it on and turn the ignition off, it should stay on and then power down after a while, but I seem to remember there is a problem with some early VW Can Bus gateway modules (or as VW like to call them, the Central Convenience Module) that handle this task of powering down the head unit and other things like the window controls that are all inhibited circuits (live for a short while after the ignition is turned off)

I seem to think the fuse for this is F48/SB48 in the engine bay fuse box.

You could try pulling it and testing the drain (or just leaving it a few days, see if the battery holds charge)

B0bbyEwing

https://forums.moneysavingexpert.com/discussion/comment/81979675#Comment_81979675

Thanks for the info.

The car isn't actually with me at the moment. I've got it at a different address for the time being & can't get there for a few days yet so can't say for 100%.

I do remember shortly after getting it telling the OH that she needs to turn both the radio off & unplug whatever is connected to the 12v socket once she parks up, which makes me think that the radio does stay on for a short while after removing the key.

But over time I remember saying to her - oh the radio actually turns off, whereas the 12v socket is live all the time, so she only needs to worry about removing stuff from the 12v socket.

I know with the MK3 Mondeo through fuse placement you could change the 12v socket from perm to switched live. Not sure if you could do that with the MK5 Golf though.

Goudy

The head unit would usually stay on for X amount of time when the ignition is turned off OR when you open the drivers door.

This Can Bus module will control things like this but some are prone to faults which tend to keep all the systems live, so causes a parasitic drain.