Inverter reverse current

Submitted: Thursday, Mar 27, 2008 at 12:06
ThreadID: 55971 Views:1927 Replies:9 FollowUps:12
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Inverter reverse current

My 7 year old 300w inverter has finally decided to start playing up. I have had many good camping trips with it. Over the weekend I was running a 48w fluro light and I went to the car to grab a beer out of the Engel and when I touched the hatch to open the lid I got a little zap and felt some current running through me. This obviously gave me a fright and I thought the fridge was faulty. So I unplugged the Engel and tried again and the current was still there. I then went around to the engine bay to check voltage and stuff at the battery and again when I went to open the bonnet I got a nasty zap. I then relised that it must be the inverter causing this. I turned it off straight away after this and used my other inverter and the problem went away.

Does anyone have any theories as to why this happened? I am guessing it’s just age and I good really good service out of it?
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Reply By: Member - Beatit (QLD) - Thursday, Mar 27, 2008 at 12:30

Thursday, Mar 27, 2008 at 12:30
I'm guessing that you have something live touching metal but then I'm not a sparky!

Kind regards
AnswerID: 294986

Follow Up By: Member - Troll 81 (QLD) - Thursday, Mar 27, 2008 at 12:33

Thursday, Mar 27, 2008 at 12:33
that's what I thought as well but when I swapped the old one for the newer one I put the newer one in the exact same spot and there was no current
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Follow Up By: Member - Beatit (QLD) - Thursday, Mar 27, 2008 at 12:36

Thursday, Mar 27, 2008 at 12:36
So what happens when you use the old one out of the car?

Kind regards
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FollowupID: 560929

Follow Up By: Member - Troll 81 (QLD) - Thursday, Mar 27, 2008 at 12:39

Thursday, Mar 27, 2008 at 12:39
haven't tried and I am not real keen to either
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Follow Up By: Member - Beatit (QLD) - Thursday, Mar 27, 2008 at 12:43

Thursday, Mar 27, 2008 at 12:43
so are you suggesting that it is shorting through the housing?

Kind regards

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Follow Up By: Member - Troll 81 (QLD) - Thursday, Mar 27, 2008 at 12:52

Thursday, Mar 27, 2008 at 12:52
My guess is that it's going back through the croc clips into the battery
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Follow Up By: Member - Beatit (QLD) - Thursday, Mar 27, 2008 at 13:05

Thursday, Mar 27, 2008 at 13:05
Seems unlikely to me because it uses 12V to generate 240. I'd imagine that that a bit like water flowing uphill!!!???? but hey I have seen stranger things.

Kind regards
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Reply By: Member - Matt M (ACT) - Thursday, Mar 27, 2008 at 12:36

Thursday, Mar 27, 2008 at 12:36
Can't help with the problem, but I just keep getting and image of Homer Simpson in my mind.

Zap...DOH!

Zap...DOH!

Zap...DOH!
AnswerID: 294987

Follow Up By: Member - Troll 81 (QLD) - Thursday, Mar 27, 2008 at 12:39

Thursday, Mar 27, 2008 at 12:39
hahahahaha
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FollowupID: 560931

Reply By: Member - John and Val W (ACT) - Thursday, Mar 27, 2008 at 14:55

Thursday, Mar 27, 2008 at 14:55
Troll -

Suggest first, satisfy yourself it's not just a static electric bite - the sort of zap we all get occassionaly by sliding out of a vehicle then touching the vehicle.

If you're convinced it's coming from the inverter, talk to an electrician (not an autoelectrician, a mains type person.)

To get a shock from mains voltages such as your inverter produces, electric current must flow through you. One side of the 240V mains supply is connected to ground, so many electric shocks result from standing on the ground and somehow coming in contact with the other side of the mains supply.

With an inverter though, there isn't any obvious connection to the ground, so standing on the ground and touching the vehicle shouldn't result in any current flowing through you, so no shock. Get someone with a suitable meter and knowhow to make a few measurements.

When dealing with mains voltages, if in any doubt, touch with the back of your hand fiirst, not the front - that way if it is dangerous you'll jump away, not have your hand forced closed to grip it tighter. Better still - let someone else do it!

HTH

John

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AnswerID: 295010

Follow Up By: Member - Troll 81 (QLD) - Thursday, Mar 27, 2008 at 15:00

Thursday, Mar 27, 2008 at 15:00
John

When I went to open the bonnet I had to use the bonnet clip thing to unlatch and even then I felt it going through me. After I turned the old inverter off I went and touch everywhere I got zapped before and there was nothing.

I am 100% sure it was coming from there. I am not even going to try and turn it back on I am just more curios as to why. I am so proud of this little inverter it might get a little spot in my wall behind the bar for lasting so long :)
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FollowupID: 560967

Reply By: Dunaruna - Thursday, Mar 27, 2008 at 19:22

Thursday, Mar 27, 2008 at 19:22
Is it -

1. A (cheap) modified sinewave

2. Got a windnut on the back with the 'earth' symbol

AnswerID: 295061

Follow Up By: Member - Troll 81 (QLD) - Thursday, Mar 27, 2008 at 20:07

Thursday, Mar 27, 2008 at 20:07
back then it wasn't cheap but I did get it from super cheap and there is no wingnut on the back for a earth
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Reply By: Dunaruna - Thursday, Mar 27, 2008 at 20:22

Thursday, Mar 27, 2008 at 20:22
There has been quite a bit of discussion about the safety aspect of cheap (what most people buy) inverters. I hope this thread does not die, I'm looking forward to what the cause off your problem is.
AnswerID: 295086

Reply By: gasgas - Thursday, Mar 27, 2008 at 20:45

Thursday, Mar 27, 2008 at 20:45
It sounds like there is a short between the 240v Active and the 12v Negative inside the inverter, thus causing the vehicle to become live and anything else that is connected to the battery (your fridge)

WITHOUT POWERING UP THE UNIT you can prove this by using an ohm meter to measure the resistance between the Active pin on the inverter (left hand side as u look at the 3 pin outlet) and the negative terminal.
Shoul read a low resistance if my hunch is right.


PLEASE, DO NOT PUT POWER ON THE UNIT UNTIL YOU HAVE HAD IT CHECKED BY SOMEONE QUALIFIED
AnswerID: 295098

Follow Up By: Member - Troll 81 (QLD) - Thursday, Mar 27, 2008 at 20:56

Thursday, Mar 27, 2008 at 20:56
Thanks for your reply sounds like you are onto something,

The plan is to leave it unplugged for good. The unit has served me for 7 years and I am happy with that.
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FollowupID: 561041

Reply By: avro - Thursday, Mar 27, 2008 at 21:47

Thursday, Mar 27, 2008 at 21:47
You almost certainly have an inverter that does NOT have the secondary winding (the 240 volt one) isolated from the primary (the 12 volt one). Unfortunately most of the older inverters were like this, and unless it clearly states that it is isolated (all the recent Jaycar ones are) it almost certainly is not. In effect these have a single winding, tapped at one end for 12 volts. These are potentially dangerous and in my view should not be sold or used. They have recently been banned on Victorian worksites I understand, but should be banned everywhere.

You usually need to touch both an active and an inactive to get a big (usually lethal) belt, but the capacitance of your body canl cause a small current to flow and give you a tingle (or worse). My advice is to cut the leads off (so it cannot be used again) and throw it in the rubbish bin.

Regards avro
AnswerID: 295117

Follow Up By: unimog - Thursday, Mar 27, 2008 at 22:23

Thursday, Mar 27, 2008 at 22:23
Avro is on the ball, absolutely correct.

Oh, by the way, if you really like the feeling of being electrocuted you might be able to still buy the 'old' type of inverters, brand new from China for not much more then a few dollars...

Banned, but still available... where? on Ebay, where else..

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FollowupID: 561084

Reply By: Nomadic Navara - Thursday, Mar 27, 2008 at 21:48

Thursday, Mar 27, 2008 at 21:48
Being 7 years old it is possible that the primary winding in its transformer is also part of the secondary winding (called an auto transformer.) If one of the output leads had leakage to ground then the whole of the car could have been live.

Most of the newer inverters have the primary and secondary windings of their internal transformer isolated from each other. Always purchase inverters that have their 240V output electrically isolated from the 12V circuit. You can check if there is isolation with the ohms range on your multi meter. Disconnect the inverter from everything. If there is an input switch on it switch this on. Set the multi meter to a low ohms range and test to see if there is any resistance between either of the input leads and the output leads. If there is any resistance between an input lead and either of the output leads it is not an electrically isolated unit and should be thrown out or used with caution.

To see what an auto transformer is go to this link

PeterD
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AnswerID: 295118

Reply By: Member - Ruth D (QLD) - Friday, Mar 28, 2008 at 00:23

Friday, Mar 28, 2008 at 00:23
Troll 81 - guess you didn't want to see me at Gordon Country at the weekend if you had seriously fuzzy hair after the little zapp!!! LOL.Missed meeting up with you - there sure were plenty of people there. My kids had a great time - lucky I took my own lunch because the Sunday roast lamb did not eventuate.
AnswerID: 295151

Follow Up By: Member - Troll 81 (QLD) - Friday, Mar 28, 2008 at 08:56

Friday, Mar 28, 2008 at 08:56
Yea we were there camped near King Parrot right on the water
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