How to create reliable stable Current Drain

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Re: How to create reliable stable Current Drain

Postby Fat Freddy » Sun Feb 10, 2013 8:56 am

Have you considered making your own resistive load using Nichrome wire? http://en.wikipedia.org/wiki/Nichrome
Same as your heater element but customised to your needs.

HTH
FF
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Re: How to create reliable stable Current Drain

Postby FioranoCars » Sun Feb 10, 2013 6:39 pm

Not considered glow plugs, assumed they were lower watts than the 150w a couple that I looked up are!
However they take about 20secs to stabalise, drawing almost double the current cold, see
https://www.picoauto.com/automotivetopics/glowplug.html

But could investigate further, though the heat might be a problem as well. One for the back up plan

CRD (Common Rail Diesel) Heaters - seem a tad expensive, and a couple I saw were under 50W, so too small a load.

but thanks for the ideas, they all help!

Nichrome Wire ... never heard of being able to buy this so easily or cheaply, or known it's name before!
Looks perfect, and a fraction of the price of the water heaters, will buy a roll and have a play!

Also can now make that foam cutter I've been wanting to do!

Thanks Freddy
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Re: How to create reliable stable Current Drain

Postby hexibot43 » Sun Feb 17, 2013 4:28 am

I've been following this thread for a while and thought I'd ask a couple questions. These days we use simple hand held testers for testing batteries that do a very good job of testing the ability of a battery to provide current and voltage. I am wondering if you could do something like this to test wire itself? I've also seen testers that use capacitance to tell you how far along a damaged wire lies the break. I spent some time tonight trying to find more info on the net to substantiate my idea but have yet to find it. Will the load test you're providing catch bad connections that might take a while to heat up and start showing signs of failure...possibly. How long should you load the wire to consider it good? I'm thinking some kind of high frequency testing might catch a problem like this long before the wire/connector has heated up enough to show up with a simple load test. Something like what is used in the testing of batteries today. You could test without all the heat generated issues. I might be totally crazy. Maybe someone else could chime in if this might be possible. I know I've read something on this before. I just haven't been able to find it again.
I think testing for conductance might be the smart answer.
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Re: How to create reliable stable Current Drain

Postby FioranoCars » Sun Feb 17, 2013 11:01 am

Hi and thanks for the repl
Yes, you are right about testing the wires using a tester, for domestic and commercial 110/240v applications you use what tends to be known as a "Mega", but everything on the circuit must be disconnected, otherwise the devices connected could be damaged, lighting cable being 1-1.5mm solid copper, ring mains 2.5mm, cooker circuits/showers etc thicker again, all with their own test settings, and one of the main requirements being of good insulation between the pairs/3 wires

Sadly a car tends to not have "disconnectavble" in the same simple way, ie the device is under the dash, or in the engine under the plenum, and there not being wire pairs, the negative being the chassis or anything else close to hand (the engine) so harder to apply such kit, but without doubt could be done, if you knew enough about the tester kit and the wire parameters, as the wire capacity is key. Cars have mnany more wire specs than a house uses.

Back to the reason for the tests
Yes to tes the alternator under load, not really for heat but to avoid the dirty noise generated by zenons and other items so that ac ripple can be looked at as cleanly as possible, using a carbon pile tester means hard to achieve identical load levels accuarately, and the risk of an untrained person overloading dangerously (600+amps possible!)
So a simple 20, 40-60amp load for idle and fast idle tests. This , subject to testing the rig once the resitive wire arrives, can now be done I hope fairly safely! (at a cost of about $15|GBP10), so a GBP1000+ Mega would be overkill, though might be more scientific if you knew what you were doing

The second reason was for smaller loads to be able to test circuits that had either intermittent faults, needed to be proved, or had delicate / unsafe devices, so a substitute load would make life safer, and easier to manage, fuel pump, F1 hydraulic pumps, wipers (lots of our cars can wipe with bonnet open)

The tests could either be done as a simple wiring test (either soak or normal), from the fuse to the device connection, with the subsitute load at either end, or as a working circuit with the substitute load at the device end, and volt drop being measured over time with the ability to see if it increased over time within the duty cycle of the device. (either by manual control/switching or letting the car do it)

This smaller load I have solved 9once tested!) the same way with a 0-100% dial with LED and using the correct length resistive wire to get a 10amp load, so I have a LED read out of amps 0.1-10amp variable load, and with a couple of 5 or 10amp on/off extra loads can create anything from 0.1-50amps. So the search for the how is over (I hope), now it's just a case of working out how/what else I can use it for!

The current 0.5amp load test devices just will not be enough load to show up a wiring fault for some of these in some situations, yes it will find a basic bad connection regardless of the operating current, so will find 85% or more, it's that 10-15% of wierd and hard to solve circumstances that I'm after. They definately have their place, still a bit risk in inexperienced hands as they can blow ecu's but a lot safer than a 50amp load or a carbon pile tester!

Had a look at the new PoewerProbe "The Hook" specs and it does do a "hot Test" load test, I assume it's 0.5amps, but that makes it one of the most complete single test tools out there, at GBP 400 ish, it needs to be, but I'll be ordering mine shortly!

Thanks agai
Richard
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