solenoid query

I think the current drain would be too large using an ordianry starter solenoid, we have a two stage solenoid on a woodchipper to hold the fuel on, once it has made contact a second coil does the hold on.

To my mind you're going to far in expecting the solenoid to take both starting and charging current, a 60 amp solenoid with 60A fuse inline is probably enough to keep the batterry charged then disconnected when ignition off, just a removable isolator key to connect power when you need it an remove once started, in parallel with the charging relay.

AJH

Austin, you only need the sod off capacity while cranking. Charging is only likely to be a few amps, maybe tens of amps at most, so a regular auxilliary relay would be adequate for that. Use a starting solenoid to connect the two in parallel when starting. You might actually want to arange it as a split charge circuit so that a duff battery doesn't attempt to suck the good one dry, bearing in mind the good ones still capable of cranking amps.

Having reread your request, you only need a standard? split charging circuit for your 'auxilliary' battery, since your high current cranking circuit is covered by your isolating switch. Standard circuit is usually a simple relay energised off the charge warning light circuit.

Starter solenoid has a powerful coil that earths through the windings of the starter which is shorted out by the contacts when the starter windings are powered leaving a small coil which is earthed directly to ground holding the starter engaged as long as the keyswitch is held in the start position.

Martin

On or around Sun, 31 Aug 2008 11:54:16 +0100, "GbH" enlightened us thusly:

yeah, but I want the isolator to be automatic, that's the point. Manually isolating it will work fine provided I don't forget...

It's not a duff battery, they're both good. There's an unresolved issue with something on the vehicle draining the battery. I've yet to trace it, beyond knowing which circuit it's on - The current drain that's measurable is not enough to do it, so it must also be intermittently drawing more.

When it's in use every day, it's not an issue...

Its still only a problem with cranking current. Just use a dinky relay to connect them together while running and put an extra starter solenoid from back up battery to starter for cranking . That way cranking current won't go through the dinky relay, or rather try to go through before welding its contacts. You'll still have trouble mechanising the 'automatic' to detect when you need the secondary battery in circuit. Unless you just assume you're going to need it. Hang on going a bit over the top here, if I understand correctly what you need to do is a relay in series with the normal (non cranking) supply, energised off the ignition switch, so battery is completely isolated when vehicle off. That relay might need some fairly substantial contacts cos it might be required to handle all vehicle supply, lights fans demisters ect. which is possibly quite a bit, I don't know how much exactly but checking the main fuse value might suggest. Ultimately I think you might find you time better spent tracking down the real fault. Or at least isolating the bit the fault is in and then putting a relay in there.

Yes, maybe 60Amps so a simple relay will do this bit, and all automatic.

When the vehicle battery is dead is the only time the auxillary is needed at a few hundred amps, so an engine isolator in parallel with this relay, with key kept in a glove box, is all that is needed to bring that battery into circuit. Once engine is started put the key back in the glovebox.

AJH

On or around Sun, 31 Aug 2008 14:16:22 +0100, "GbH" enlightened us thusly:

possibly, possibly...

vehicle wiring products have a 200A rated relay which should do it, so one of them has been ordered.

Basically, what I want is for the 2 batteries to be in circuit normally when the ignition is on. OK, really it should have split-charge, but I doubt it's going to be a big problem as both batteries are pretty decent and not all that old.

When it's standing idle, the one battery needs to be disconnected, then it doesn't matter how much current gets used, whether it's a current leak, or the interior lights being on due to the door being open etc., I'll still have the other battery which comes in when the ignition is turned on to start it.

The fault may be the tachograph. I don't know how much current one of those should take. Equally, seeing as it still works, I'm not at all keen to replace it even if it is faulty, unless it gets more faulty, IYSWIM. I bet they cost an arm and a leg.

The offending circuit runs interior lights, most of the instrumentation and the tacho (or clock, on a non-tacho one).

Ah, that nice bit of wiring that doesn't go through the ignition switch. When you say tacho do you mean tachograph or tachometer. If its a tachometer, one driven off the altenator? probably if it's diesel, guessing but check diode pack in altenator, that could give you a nice leakage path, but everything would seem to work fine otherwise. If its a tachograph, haven't a clue, but still check the diode pack.

Radio memory?

Yeah I was thinking the same.. I have one here ready for the bin too!

Lee D

"Austin Shackles" wrote in message news: snipped-for-privacy@4ax.com...

Austin I'm betting you have a multimeter how about knocking up a doohicky like these outrageously priced leads

The tachograph should draw very few milliamps. I think we pay a couple of hundred exchange plus fitting & calibration, but at some time in the not too distant future (2010 rings a bell), analogue ones will become unobtainable, & you'll have to go digital at

Partial short to earth (usually via corrosion) on a door switch or interior light override switch? Not quite enough current to fully light a lamp, but enough to flatten a battery over a day or two. If you can pull the fuse & check the current while disconnecting bits one at a time, that might find it.

On or around Sun, 31 Aug 2008 17:11:16 +0100, "GbH" enlightened us thusly:

tachograph. It's not actually a legal requirement (luckily) to record using same, for the work I'm doing. However, if it were, I'm sure it's dead norty to pull the fuse, even if it's parked up.

On or around Sun, 31 Aug 2008 18:17:40 +0100, "Oily" enlightened us thusly:

The radio circuit only takes about 5mA or something. The circuit with the tacho, instruments and interior lights on it takes a variable amount something in the region of 170mA. That might flatten the battery in about 6 weeks, but shouldn't do so as quickly as it does - so I conclude that intermmittently it draws more current.

On or around Sun, 31 Aug 2008 19:07:32 +0100, "Derek" enlightened us thusly:

I do. It's tracing beyond the fuse to find the offending failure point that's the hard part.

On or around Sun, 31 Aug 2008 23:15:12 +0100, John Williamson enlightened us thusly:

it's the disconnecting that's the hard part, finding the wiring is next-to-impossible.

that's a good possibility. If I can find the connections to the interior light loom, of which I think there are more than 1, that might narrow it down a bit.

Having more battery won't hurt, mind.

6 x 7 x 24 x 0.17 = 171.36 AH. That's a *big* battery Austin. 170mA I'd say would flatten a normal range sized battery Tracing the wiring might be tricky but how about removing things instead like interior light bulbs, clocks, radios, WHY?

On or around Mon, 01 Sep 2008 10:12:07 +0100 (BST), "Dave Liquorice" enlightened us thusly:

well, it does flatten at least that quick. The interior light bulbs in the back are removed anyway, I replaced it with a fluorescent thing, which hasn't affected this problem. The idea of a dodgy switch somewhere is the most likely, I suppose. The circuit is "interesting" and runs all over the vehicle. That's before you look at the instrumentation circuits.