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Blowing fuses

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dennis.glaeser(at)eds.com
Guest

Posted: Tue May 15, 2007 10:37 am Post subject: Blowing fuses

Bob, et. al.,    

I have a Z-19 architecture (modified a bit for a Subaru engine) with rear mounted Odyssey batteries.  I have 2 lighter receptacles on the panel, each wired to a battery hot bus through a 10a fuse.  

I put a couple of lighter plugs on my Battery Tender Jr. as a convenient way to charge the batteries.  I don't have my engine yet, to charge them the 'proper' way.  

The other night I decided to charge the batteries, because I've been playing with my radios a bit.  I inserted the charger plugs one at a time to verify that the green light on the charger came on.  When I removed the plugs, the fuses blew!  Same thing on both of them, done one at a time.  I've done this before with no problem.  I double checked the wiring, and everything is connected as desired.  

I replaced the fuses, re-inserted the charger plugs, and let the batteries charge overnight.  By morning the green light on the charger was blinking (indicating maintenance mode).  I pulled the lighter plugs out, and this time one fuse blew.  I replaced the fuse and plugged everything in again.  The charger cord has a plug to allow use of multiple ends, so this time I disconnected the lighter plugs from the charger before removing the lighter plugs - no problem,  Did that multiple times, no problems.  I haven't tried pulling the energized lighter plugs out again (running low on fuses!).  

So, obviously, my question is: why would pulling out the energized lighter plugs cause the fuses to blow?     

Dennis Glaeser  

RV-7A  

Rochester Hills, MI     [quote][b]

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john(at)ballofshame.com
Guest

Posted: Tue May 15, 2007 11:31 am Post subject: Blowing fuses

How do you know when the fuse is blowing?  For example, if you plug both

in and there's a short somewhere, one fuse may blow and the other one will

look OK.  The charger still sees a battery so it'll still turn green.  You

unplug one (the blown one) and notice the fuse is blown.  You unplug the

other one, jostle something that shorts out again, and it blows the 2nd

fuse.



I'm not suggesting this happened.  I'm just curious how you determined the

timing of when the fuse actually blew.  Do you see any marking on the

connectors or recepticle that would indicate an arc?  Are you using a fast

or slow fuse?



Maybe there's just a small arc when you disconnect it and you have to use

a slow blow fuse?  That would seem strange to me.



The most obvious answer would be that there's a short in one of the

recepticles or the plugs.  That's so simple to check that it should be the

first step, I guess.  Maybe I'm missing something even more obvious.



-John



 	  Quote: 	
		   Bob, et. al.,



 I have a Z-19 architecture (modified a bit for a Subaru engine) with

 rear mounted Odyssey batteries.  I have 2 lighter receptacles on the

 panel, each wired to a battery hot bus through a 10a fuse.

 I put a couple of lighter plugs on my Battery Tender Jr. as a convenient

 way to charge the batteries.  I don't have my engine yet, to charge them

 the 'proper' way.



 The other night I decided to charge the batteries, because I've been

 playing with my radios a bit.  I inserted the charger plugs one at a

 time to verify that the green light on the charger came on.  When I

 removed the plugs, the fuses blew!  Same thing on both of them, done one

 at a time.  I've done this before with no problem.  I double checked the

 wiring, and everything is connected as desired.

 I replaced the fuses, re-inserted the charger plugs, and let the

 batteries charge overnight.  By morning the green light on the charger

 was blinking (indicating maintenance mode).  I pulled the lighter plugs

 out, and this time one fuse blew.  I replaced the fuse and plugged

 everything in again.  The charger cord has a plug to allow use of

 multiple ends, so this time I disconnected the lighter plugs from the

 charger before removing the lighter plugs - no problem,  Did that

 multiple times, no problems.  I haven't tried pulling the energized

 lighter plugs out again (running low on fuses!).

 So, obviously, my question is: why would pulling out the energized

 lighter plugs cause the fuses to blow?



 Dennis Glaeser

 RV-7A

 Rochester Hills, MI

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Dennis Glaeser

Joined: 10 Jan 2006
Posts: 53
Location: Rochester Hills, Michigan

Posted: Tue May 15, 2007 2:25 pm Post subject: Blowing fuses

John,



I actually heard the 'pop' of the fuses!  (It was a quiet evening in the

garage)  I inserted the first plug, got the green light, and when I removed

it, I heard the pop, but didn't realize what it was.  Then I inserted the

second one, got the green light again, and then removed it and heard the pop

again.  Then I re-inserted the plugs - no green light.  I'm using regular

automotive fuses.

The circuits work just fine when I insert the plugs.



I've got another data point - just went out and played again...

This time I inserted and removed the hot plugs one at a time, no problem.

So I plugged both in and removed one, and POP, the fuse of the one still

plugged in blew.  The fuse for the one I removed is still fine, and I can

insert and remove that one with no problem, and the inserting/removing other

one has no effect, now that the circuit is dead.  I'm not sure how I managed

to get both that first time (just lucky I guess 

So it appears that when both are charging, don't remove one at a time,

instead, unplug the cord (which kills both simultaneously).

But I'd still like to know why the fuse blows.



Thanks,



	Dennis

Subject:      Re: Blowing fuses

From:      john(at)ballofshame.com

Date:      Tue May 15 - 12:31 PM



How do you know when the fuse is blowing?  For example, if you plug both

in and there's a short somewhere, one fuse may blow and the other one will

look OK.  The charger still sees a battery so it'll still turn green.  You

unplug one (the blown one) and notice the fuse is blown.  You unplug the

other one, jostle something that shorts out again, and it blows the 2nd

fuse.



I'm not suggesting this happened.  I'm just curious how you determined the

timing of when the fuse actually blew.  Do you see any marking on the

connectors or recepticle that would indicate an arc?  Are you using a fast

or slow fuse?



Maybe there's just a small arc when you disconnect it and you have to use

a slow blow fuse?  That would seem strange to me.



The most obvious answer would be that there's a short in one of the

recepticles or the plugs.  That's so simple to check that it should be the

first step, I guess.  Maybe I'm missing something even more obvious.



-John

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Ed Anderson

Joined: 10 Jan 2006
Posts: 475

Posted: Tue May 15, 2007 5:10 pm Post subject: Blowing fuses

Dennis, this is just a stab in the dark, since I not certain what loads you 

have on the plugs.  But, if you have both plugs in pulling current from a 

common system and suddenly unplug one of them - if there is any inductive 

component in the system, then the termination of the current flowing in one 

plug might induce added current in the second plug.  This may be why they 

only pop when you remove one.  Again, just a stab in the dark.



Ed



Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson(at)carolina.rr.com

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.dmack.net/mazda/index.html

---

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_________________
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com

dennis.glaeser(at)eds.com
Guest

Posted: Wed May 23, 2007 10:27 am Post subject: Blowing fuses

Bob,

I'd asked this question a week ago and never got a reply that offered a

plausible explanation, so I'm trying again...



I have a Z-19 (2 batt, 1 alt) architecture, modified a bit for a Subaru

engine, with rear mounted Odyssey batteries.  I have 2 lighter

receptacles on the panel, each wired to a battery hot bus through a 10a

fuse.  I attached a couple of lighter plugs on my Battery Tender Jr. as

a convenient way to charge the batteries.



The Problem: I can insert and remove a 'hot' charger plug to one battery

at a time with no problem.  However once I insert both plugs (and both

batteries are charging), and then remove one plug, the fuse on the other

circuit blows.  This is a repeatable experiment.  Once both plugs are

inserted, the only way I can remove them is to either unplug the

charger, or unplug the charging plugs from the charger (the output wire

has a plug to enable different endings to be attached).



Can you explain the physics of why the fuse blows when one plug is

removed?



Thanks,



Dennis Glaeser

RV-7A

Rochester Hills, MI

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