Blowing Fuses on the Grid Charger

Artric · 07-23-2010, 12:57 AM

At first, I was blowing fuses because I had the fast-blow type, which were a bad idea. I switched to slow-blow 1A fuses and things had been going fine. I did blow one fuse a week or so ago, and another today.

Both times, I had no surge protector in place. Today, I plugged in in a new spot next to some huge transformer, so I'm sure that caused the problem.

I'm going to keep a surge protector in place and see if it happens again. Hopefully not. I wish I didn't have to do this though, because it's a bit of an eyesore. I wonder if I could work one into the charger itself somehow?

Anyway, has anyone else had this problem?

RobertSmalls · 07-23-2010, 11:11 AM

Are you blowing fuses on the AC or DC side?

I haven't had a single issue with that yet, and my KaW reports 67W AC draw, or about 0.5A. If it's on the input side, maybe you can get away with a bigger fuse.

**MN Driver** · 07-23-2010, 12:18 PM

The inrush current is specified at 30a/230v per each rs-25-48 unit. Seems high considering their size and output characteristics, it's clear they don't have any precharge resistor setup on their input side. I'm sure the 30A(not sure what it pulls for 120v though) is for just a few AC cycles in a very short duration but even a slow-blow has its limits before it pops in an instant. Looking at the ratings on the specsheet it says each units input ratings are .7a/115v, you are pulling 350mA instead of the rated 570mA but you might want to try stepping up the size of the sloblow fuse to a 1.5amp or maybe 2amp fuse. As long as you have suitable input wiring to handle the amperage of the fuses that isn't a concern, which I'm sure probably isn't an issue unless you are using some seriously small wires. If you get a short, it's likely going to pull more than a single digit number of amps and pop instantly with a slightly larger fuse if it does short circuit.

Are the fuses blowing immediately upon plugging it in or is it after it's been running a minute or so? If it is right away and you are certain there isn't a short, it's the inrush current it can't handle, if it is later during the charge, you are possibly pulling more than an amp through the fuse. 175*.35=61.25 watts 61.25/120v=.51amps Add a little extra for efficiency of course. RobertSmalls numbers fit the math(do you have a VA or powerfactor reading?). It shouldn't be a problem as far as average current goes but I wonder if the rectification is just ripping chunks of current off the AC sine peaks or something. I might be wrong about this, do you have any tools to measure the AC current that would't blow up with the inrush that these need when being plugged in? Kill-a-watt meter or something similar? Could it be possibly you've got a dud unit running with really bad efficiency?

Artric · 07-24-2010, 02:47 PM

The fuses are blowing on the AC side. It's not happening as soon as I plug it in (now that I'm using the slow-blow fuses). It's also not happening consistently, so I assume it's hitting some sort of surge to pop them.

I've never seen them blow, it's always been the case that I plug in, then come back some time later and see it's not charging.

I do have a Kill-A-Watt Unit. I measured it previously, and it was pulling around 60-70w, IIRC, but that was before I took the wall wart out of the equation and added in the RS-25-12 to power the pack fan and 120mm charger fan at 12v.

Maybe the addition of those two items should push me up to a bigger fuse? I've got one more of them left, so I'm going to keep using a surge protector, and if I blow another, I'll step it up. Should I go 1.5 or 2A?

JimIsbell · 07-25-2010, 12:15 AM

Quote:

Originally Posted by Artric

Maybe the addition of those two items should push me up to a bigger fuse? I've got one more of them left, so I'm going to keep using a surge protector, and if I blow another, I'll step it up. Should I go 1.5 or 2A?

Go to 10 amps fast blow. The idea of the fuse is to keep from burning up the wires if something shorts. You could probably go to 30 amps and it would still work. A short puts INFINITE current through the fuse till it blows a few milliseconds later. Thats not even long enough for the insulation to get warm. Well, not quite infinite, the resistance of the wire will limit it very quickly, but not below 100 amps.

Artric · 07-25-2010, 09:51 AM

Jim, thanks for the recommendation. I'll go that route the next time one blows. Good luck so far (using a power strip).

RobertSmalls · 07-25-2010, 10:48 AM

I can't agree with 30A. Most residential wiring is rated for 15A, and unless you're using a beefy power cord, your cord won't take 15A. Plus, if you've used "found wire" on the AC side of the charger, you have to keep the fuse below the rating of your smallest wire and your most sloppily assembled connection.

10A is probably fine, but 5A is probably better. Besides, if you blow a 5A, you're doing something wrong that you need to look in to anyway.

JimIsbell · 07-25-2010, 11:01 AM

Quote:

Originally Posted by RobertSmalls

I can't agree with 30A. Most residential wiring is rated for 15A, and unless you're using a beefy power cord, your cord won't take 15A. Plus, if you've used "found wire" on the AC side of the charger, you have to keep the fuse below the rating of your smallest wire and your most sloppily assembled connection.

10A is probably fine, but 5A is probably better. Besides, if you blow a 5A, you're doing something wrong that you need to look in to anyway.

Yes, you are right but........
No, I was being facetious when I said 30 amps. BUT......a 50 amp would work IF THE PROBLEM WAS A SHORT. A Short takes the current to the stratosphere instantly and the fuse would blow before the wire got hot. Small wire has to heat up then melt then fuse. It takes a second or two while a fuse is designed to go in milliseconds. Once the fuse goes the current is off the wire. But you cannot be sure the problem is a short, every time. So a 10 amp will take care of almost anything but a lightning strike which will go right through the fuse.

**MN Driver** · 07-25-2010, 12:43 PM

...what about the inrush current, it's a fraction of a second but how fast is the fuse compared to the large inrush current that is in their specification sheet? As long as the fuse doesn't blow right away, it will be clear that inrush current isn't a problem.

How much does the ambient temp affect things for him. It's high since its in the back of his car outdoors where its probably very hot in the back of the car, being heated even more by the battery charging. I have a hunch this might have something to do with it(other factors might cancel this out or eliminate it as a cause though), usually fuses are used in areas where the temperature is within a certain range.

I do however agree that a fast acting fuse is the best option unless you are handling motor starting currents where a motor pulls a burst of power quickly for a moment while it spins up.

...on a separate note, has anyone considered adding a self-resetting thermal fuse to their battery? The Meanwells are specced with thermal protection but if we put one in the battery compartment that wouldn't be such a bad idea, would it? ...in case unexpected things happen.

JimIsbell · 07-25-2010, 03:03 PM

Well, there may be something wrong with his set up because I have three Meanwell supplies and a 350ma CC supply and a 12V 1 amp wall wart for the fan, all in the battery compartment and no input fusing but the 15 amp breaker that is on the AC circuit that supplies current to the pigtail. I know that the 15 amp breaker will trip before anything in the battery compartment gets hot enough to be a problem. Every place that I may be plugging in also will have a 15 amp breaker on the AC line, that is building code here in the US.

Oh yes, I charge the battery in temps up to 90F with no problems.

I dont fear a thing having them in the battery compartment. I have charged as long as 16 hours with this setup and had no breakers trip or any other failures.

I think he should check his wiring.