Renogy 2000W Inverter Internal Fuse Question

[John Kinslow]

Looking at previous post, I see I'm not the first or the last to hook up an inverter with reverse polarity. Was too busy talking and not paying attention! No smoke; but sparks. Anyway checking inside I find 10 ea 25 amp mini blade style fuses bridging the positive lead in on the circuit board blown. Figure it must be part of the reverse polarity protection. I temporally bridged across the fuses and the invertor came back to life.

My question is why are 10 25amp fuses used in lieu of a 250 amp single fuse? The fuses are fastened directly to the board with lead solder and something additional like an epoxy under the solder. I believe I saw somewhere the blades on the mini fuses are aluminum.

I haven't used this unit but a couple of times in the last couple of years; but don't want to chuck it if I can replace fuses of bridge the circuit with a single fuse.

Any suggestions would be appreciated, Thanks

 

[Mattb4]

...

My question is why are 10 25amp fuses used in lieu of a 250 amp single fuse? The fuses are fastened directly to the board with lead solder and something additional like an epoxy under the solder. I believe I saw somewhere the blades on the mini fuses are aluminum.

I haven't used this unit but a couple of times in the last couple of years; but don't want to chuck it if I can replace fuses of bridge the circuit with a single fuse.

Any suggestions would be appreciated, Thanks

My guess is that 10 blade fuses of 25a is cheaper than one 250a fuse.

Since the inverter switched on once you bridged the fuses it would suggest you could use that arrangement to wire in your own fuse. Years ago I had one of those mobile inverters that came with a small sack of replacement blade fuses. Pretty much useless since the job of unsoldering and replacing them was not insignificant. But looking up your Renogy I see it ain't a cheap inverter so it may be worthwhile to do.

 

[seneysolar]

If by chance youre not experienced with soldering on a board, id recommend looking to see if your area has a TV or electronics repair guy. Most of the old school repair places are gone now but if you can find one, go support him. OEMs arent the only ones who can solder a fuse on a board.

 

[mikefitz]

why are 10 25amp fuses used in lieu of a 250 amp single fuse? The fuses are fastened directly to the board with lead solder

The copper tracks on the PCB have limited current carrying capacity, thus the need for multiple fuses and its a method for reduced manufacturing costs.

If its possible I suggest adding an ANL 250 amp fuse and holder. Ideally Inside the case, and bridge the 25 amp fuse positions with suitable copper wire.

 

[John Kinslow]

Thank you all for your responses. I bridged the blown fuses with 4ea 10ga. jumper cables and will install a 250 amp fuse on the positive input terminal of the inverter. Will take steps to make sure the unit is never hooked up incorrectly again as I'm feeling the original fuse set up prevented the unit from being a pile of components when hooked up backwards. Thanks again

 

[Daddy Tanuki]

Thank you all for your responses. I bridged the blown fuses with 4ea 10ga. jumper cables and will install a 250 amp fuse on the positive input terminal of the inverter. Will take steps to make sure the unit is never hooked up incorrectly again as I'm feeling the original fuse set up prevented the unit from being a pile of components when hooked up backwards. Thanks again

part of multiple small fuses is they will pop in a cascade never quite reaching a suitable current that could damage the unit. replacing it with one large inline fuse removes the safety factor of the smaller fuses and if you do hook it up reversed polarity it will fry the board next time with one big fuse.

 

[robbob2112]

part of multiple small fuses is they will pop in a cascade never quite reaching a suitable current that could damage the unit. replacing it with one large inline fuse removes the safety factor of the smaller fuses and if you do hook it up reversed polarity it will fry the board next time with one big fuse.

I am pretty sure what he means is he just soldered down 4 x 10ga wire across the different spots effectively removed the internal fuses and is replacing them with an external 250 amp fuse instead. So same effect of letting out the magic blue smoke if it ever is hooked up backwards again.

 

[Sennen]

Might also check if there's a Diode designed to blow those fuses in this exact scenario and ensure its functionality.

 

[Daddy Tanuki]

I am pretty sure what he means is he just soldered down 4 x 10ga wire across the different spots effectively removed the internal fuses and is replacing them with an external 250 amp fuse instead. So same effect of letting out the magic blue smoke if it ever is hooked up backwards again.

not same effect. by the maker wiring the fuses in this fashion it kind of suggest a cascade failure setup. total amps reach this, one fuse fails and then sets in motion a cascade to protect the boards.

 

[MattiFin]

Typical HF inverter is build up from multiple 200…500w transformers. Yours likely have 5 or 10 identical step-up dc-dc converters with primaries in (sort of)parallel. Some manufacturers fuse these converters separately, probably to limit the likelihood of the unit bursting into flames.
If one of the primary mosfet transistors shorts out the separate fusing limits the current and energy available.
10 mosfets with invidual fuse for each vs 10x bigger fuse for 1 shorted mosfet out of 10 in parallel.

And some cheapo manufacturers just slap 10 fuses in parallel because it is cheapest and sort of works.

 

[JayArr]

by the maker wiring the fuses in this fashion it kind of suggest a cascade failure setup. total amps reach this, one fuse fails and then sets in motion a cascade to protect the boards.

That's not how electronics work. If the fuses are all in parallel and they are all the same rating then they all, nominally, blow together. If you want them to cascade they need to be different values, eg: .8A, .9A, 1A, 1.1A etc.

Remember that the fuses are not there to protect the inverter, they are there to keep the supply wires from catching fire if the inverter shorts out. Same in a house, the breaker is there to keep the house wiring from catching fire if the toaster shorts out, the breaker is not there to protect the toaster.

Matt Fin is makes some good points but one more is that the same PCB is sometimes used for a whole line of inverters from say 500W to 2500W. When you open a low watt unit you'll see a bunch of empty places for MOSFETs that were never installed and you may see empty spaces for fuses that were never installed. As the wattage climbs the factory engineer will program the pick and place machines to populate the board to higher and higher degrees, adding MOSFETs and fuses etc as needed. The software gets tweaked slightly to adjust limit points etc but 95% is the same and the manufacturer saves big $$ by not having to design and build 5 different PCBs.

Sennen makes a good point, there should be a diode in there that takes the current during a reverse polarity event and protects the circuits until the fuses pop. It will now have been severely compromised, in fact it could be destroyed. The inverter will operate without this diode but if it's damaged then the inverter will no longer have any protection against the next reverse polarity event. Your call on if you want to get that checked out or just take your chances that it will never be hooked up wrong again.

 

[JayArr]

One other note I thought of. If you want to replace the individual fuses with a single 250A then you'll need a thick wire gauge capable of handling that and it will be difficult to solder that large a diameter of wire onto the circuit board.

One solution is to use 10 sets of small gauge wire that can each handle 25A and then buy two buss bars to hook the wires up and put the fuse between the two bus bars. This could get expensive and take some time to rig.

Another solution is to buy a good 100W soldering iron that has enough power to unsolder and replace the ten fuses. I have one by American Beauty that does this job quite easily.