How long before flat - ignition on

[CovKid]

Assuming that a T25 only has its normal ancilleries running with ignition on but not started, how long would you expect to be able to leave ignition on before battery was flat. I know this is rather rough science but my batt will start van fine if charged up but suspect that its gradually losing its storage capacity as 5 mins with ign on will take it well below power needed to start it.

So what do you reckon? 5 mins? 10 mins? 30 mins?

[AngeloEvs]

Igniion on as in all warning instruments on, relays engaged, ignition coil connected, heating elements etc? Have you tried measuring the current drain to see what is actually being drawn from the battery and when you say it wont start is that due to the starter motor anable to crank or it cranks reasonably well but won't start? 5 minutes does seem a tad short to drain a battery but you need to know the current drain with ignition on. Batterys are also rated in Amp hours as well as instantaneous cranking current and this tells you the battery's abilty to suatain a current over a particular length of time. 5 minutes is 1/12 of an hour and you would have to be consuming a very high current to discharge it in 5 minutes........me thinks your battery isn't fully charged or its time for a new one.

[Mocki]

i wouldnt expect it to last longer than 30mins with the ignition switched on but not running
although iirc you stand a goodly chance of cooking the coil too if you left it on for this long....

[AngeloEvs]

.......although iirc you stand a goodly chance of cooking the coil too if you left it on for this long....

yep.....will get hot ....very hot and then kaput! Wonder why VW didn't fit a three position ignition switch as used on most cars but is it possible to fit one like that to a T25?

[kevtherev]

My on board ammeter registers 40 amps with the ignition on... then 60 amps cranking

[AngeloEvs]

Bliddy hell! 40A?....bit gobsmacked with that figure, where is all that current going I wonder......

[CovKid]

Wouldn't surprise me though. Maybe VW cut some deal with the national grid. I wonder if its possible to build some kind of cutout that switches ignition off if vehicle hasn't been started within a preset time?

[Mocki]

40 amps is too much, the carb heater only pulls 15amps at cold, reducing aftera few seconds, it will be the biggest draw i recon.....

dont think any VW of our era has a Aux pos on the key.

why would you leave it on?

[CovKid]

Well, today needed it on as I was tracing live and non-live points across the fuse box but battery was flat in no time. Ho hum, new battery time maybe