hillbillyracer
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| posted on 4/8/08 at 07:27 PM |
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OT. increasing DC voltage.
Is there an easy way to increase DC voltage without spending a fortune?
My van has solenoid operated deadlocks which sometimes play up when unlocking the van, failing to draw the bolt back. If I operate it with the engine
running it's perfect every time which makes me think it just needs a touch higher voltage than the 12v it will get when the van is parked up.
I hav'nt measured it but I'm assuming the voltage when the engine is running will be about 14-14.5v. The only way I've thought about
off the top of my head is to get a converter from 12v up to 24v then use some resistors to bring it back to about 14v.
A quick scoot about on the web found me voltage reducers no bother, inverters to run 240vAC etc, but nothing to do what I want. I'm assuming
it's possible but that there isnt much call for such a device so nobody does them.
It only needs to supply power for a couple of seconds at something less than 20a, the kit came supplied with a 20a fuse.
It's no good though if it draws power when the van is parked up, I'll have a flat battery which is worse than the current situation!
Thanks, Kev.
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rusty nuts
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| posted on 4/8/08 at 07:53 PM |
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Check the charging rate , it may be as simple as low alternator output.
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McLannahan
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| posted on 4/8/08 at 07:54 PM |
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I'd of thought it's not be voltage the solenoids need but current (Amps)?
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Macbeast
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| posted on 4/8/08 at 08:12 PM |
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Amps drawn depend on voltage applied (and resistance in series  )
I would first check battery voltage first thing in morning before starting - should be 13 at least. If not, maybe a new battery is indicated. Monitor
battery voltage when you switch on headlights - if it drops significantly the battery will have high internal resistance in which case, you guessed
it, maybe a new battery is indicated.
Does the starter spin healthily and the van start ok ? If so, perhaps the battery is ok and above is load of rubbish. If so, I would suspect the
wiring to the locks.
Is there any way of lubricating the bolts ?
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BenB
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| posted on 4/8/08 at 08:56 PM |
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It is possible but it's not the answer to the problem
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hillbillyracer
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| posted on 4/8/08 at 10:18 PM |
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Cheers fellas, battery is new & the largest capacity that will fit, it almost cured the problem but not well enough. I've got no other
problems with the van, starts fine, lights work great
It has a sticker on the bolts that says "Do not lubricate the bolt" so I presume you're not meant to.
All the wiring is new & where it's extended to reach the doors of the van (the ones that came as standard would hradly have been long enough
for a super-mini) the cables are at least the size of those already on the locks.
The one lock that's really at fault is the one in the sliding door which needs to make contact through sprung door pins which I feel is
what's really causing the fault.
As I understand electrickery if you increase the voltage used a cable/connection will be able to pass more power with no increase in cable
size/contact area.
If the voltage available when the alternator is charging (likely around 14-14.5v) is up to the job when battery voltage with the engine switched off
is not then what's wrong with upping the voltage to a level where it works?
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MikeRJ
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| posted on 5/8/08 at 08:27 AM |
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quote:
Originally posted by hillbillyracer
As I understand electrickery if you increase the voltage used a cable/connection will be able to pass more power with no increase in cable
size/contact area.
Power = Volatge x Current, so ignoring insulation issues raising you can deliver more power through a bit of wire of given cross section by increasing
voltage.
However in your case you have a fixed load at the end of the wire, and Ohms law says that by increasing the voltage, you also increase the current
proportionally.
quote:
If the voltage available when the alternator is charging (likely around 14-14.5v) is up to the job when battery voltage with the engine switched off
is not then what's wrong with upping the voltage to a level where it works?
Well it sounds like you are trying to fix a problem by working on the symptoms rather than the cause.
If the solenoid can not supply sufficient force then perhaps it needs re-locating to get better mechanical advantage?
You can increase DC voltage using something called a switching regulator, but one that is capable of reliably supplying more than a few amps is not
trivial to design.
One method that is sometimes used to reduce power consumption in relays (which need a high 'pull in' current, but a lower
'holding' current) is to arrange of a large capacitor to be charged to the nominal supply voltage, and when the solenoid needs to be
activated a relay is used to connect the capacitor in series with the supply. This gives you double the supply voltage very briefly (until the
capacitor discharges). Wiring this up to work with the existing setup for both polarities (lock and unlock) will be interesting I suspect!
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02GF74
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| posted on 5/8/08 at 09:06 AM |
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q. how long are the cables from the solenoid to the battery?
q. what cross section (current capacity) are the cables?
q. are the cables wired as driectly to the battery terminals as possible?
q. are the crimps/connectors fitted properly and of sufficient current capacity?
q. are you able to measure voltage across solenoid when you operate it?
I would suggest fitting fatter cables, keeping as short as possible with good connections as diecly to the terminals as possible i.e. not using
bodywork as ground.
To up the voltage as you suggest is not going to be a simple or reliable solution - I would suggest fitting another small low voltage battery but then
you have the problem of charging it.
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PaulBuz
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| posted on 5/8/08 at 01:37 PM |
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Originally posted by MikeRJ
quote:
However in your case you have a fixed load at the end of the wire, and Ohms law says that by increasing the voltage, you also increase the current
proportionally.
Er no.
If you increase the voltage the current REDUCES.
ATB
Paul
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Macbeast
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| posted on 5/8/08 at 03:45 PM |
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""
If you increase the voltage the current REDUCES."""
No it doesn't He said for a fixed load. You're looking at fixed power.
12V across a 6 Ohm load will push 2A through it
24V across a 6 Ohm load will push 4A through it.
I agree with above - don't treat the symptoms - find out what's wrong. Did it ever work satisfactorily ?
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PaulBuz
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| posted on 5/8/08 at 07:29 PM |
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Sorry
You are of course right macbeast!
Iwas thinking in tems of power.
If I'd took the time to even think about ohms law, I'd have realised
ATB
Paul
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hillbillyracer
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| posted on 5/8/08 at 08:50 PM |
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Sorry I should have pointed out at the start this has never worked properly, it's not like it was OK & I'm attemting to cure a fault
that has occured at a later date.
The story is it's an ex AA VW T4 Transporter that I've done up, resprayed & is now worth a few quid so I thought I'd make it a
bit harder to nick. I fitted a remote central locking kit from SPAL & used these Diablock solenoid deadlocks with it:
http://www.covert-installations.co.uk/commvehi.html
The deadlocks are "piggyback" connected onto the wires for the central locking inside the doors which is how the diagram supplied with
them suggests it's done.
The wiring to the central locking motors needed extending for the side & rear doors & I used cable a touch heavier than that already on the
motors. The wires on the deadlocks themselves is much lighter than any others in the system.
Where practical I've soldered connections so poor contacts should'nt be a problem.
It played up from the word go but I put this down to the battery being duff (would'nt hold charge for more than a couple of days) but it
has'nt completely cured it now I have a new battery & the van is in regular use.
Battery voltage when parked is 12.7v & drops to 12.6v when the locks are operated so that seems fine. When running the voltage is 14.2v at
idle.
Really I think the controller for the central locking is mabye hardly up to running the deadlocks on top of it own system & it should have a
controller for the deadlocks seperate.
Shortening the cables would likely sort the problem, is anyone any good a getting the doors on a van closer together & leave the vehicle in usable
condition?
There is no way to give it more mechanical advantage, it's just a solenoid bolt.
My original idea was to cure the problem without having to run new wires to each door, upping the voltage cures the problem so why not do it that way?
If the system can't cope with 14v then it has no place on a motor vehicle.
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