Pro Charge Ultra 24V 30A Output - Fuse or Breaker?

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Currently there is a low cost automotive blade fuse holder, twin holder type, 2 x 35A fuses on the cables to the batteries. It is pants and the blade fuse terminals to cable spades are loose in the plastic housing and it gets very hot plus softening when the charger is working at 30A . I have also had low quality blade fuse plastic cover melt without the fuse blowing (30A output, 35A fuse plastic fried and dripped clear of the blade). I am thinking of replacing the fuse holder with an in line breaker instead rated at 40A. Sterling quotes that the fuse size should be around 20% bigger than charger amp rating, rounded up, according to the manual (30A x 20% = 36A, rounded up to 40A). The other option is to buy the fuse holder and fuses (40A) from Serling's web page (brass / gold plated).

  1. Would a 40A circuit breaker be suitable for a charger output cable to the battery or should fuses be actually used as described in the manual? The only reason for considering the breaker is convenience by not having spare blade type fuses.
  2. Is 40A too high a round up? The cable run between the battery and the charger is 1.5m, cable diameter as measured is 3mm (Gauge 8), so sits within the specification in the manual for 40A. The hot condition mentioned above in the fuse holder only produces a warm cable.
  3. Are the Gold Plated fuse holders and blade fuses worth the extra cost?
I have sealed lead acid batteries for engine starting and open lead acid batteries for house bank, hence the charger is set on sealed lead acid.

Thanks in advance for the help.
 
BlowingOldBoots said:
Currently there is a low cost automotive blade fuse holder, twin holder type, 2 x 35A fuses on the cables to the batteries. It is pants and the blade fuse terminals to cable spades are loose in the plastic housing and it gets very hot plus softening when the charger is working at 30A . I have also had low quality blade fuse plastic cover melt without the fuse blowing (30A output, 35A fuse plastic fried and dripped clear of the blade). I am thinking of replacing the fuse holder with an in line breaker instead rated at 40A. Sterling quotes that the fuse size should be around 20% bigger than charger amp rating, rounded up, according to the manual (30A x 20% = 36A, rounded up to 40A). The other option is to buy the fuse holder and fuses (40A) from Serling's web page (brass / gold plated).

  1. Would a 40A circuit breaker be suitable for a charger output cable to the battery or should fuses be actually used as described in the manual? The only reason for considering the breaker is convenience by not having spare blade type fuses.
  2. Is 40A too high a round up? The cable run between the battery and the charger is 1.5m, cable diameter as measured is 3mm (Gauge 8), so sits within the specification in the manual for 40A. The hot condition mentioned above in the fuse holder only produces a warm cable.
  3. Are the Gold Plated fuse holders and blade fuses worth the extra cost?
I have sealed lead acid batteries for engine starting and open lead acid batteries for house bank, hence the charger is set on sealed lead acid.

Thanks in advance for the help.
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40 amp Circuit breaker is fine next size down would be 32 amp tad on the light side.
 
I would be inclined to increase the gauge of your connecting cables while you're at it. Warm power cables make me feel uncomfortable ...
 
3mm cables for that charger are too small. Not only will they get warm, you will get an unacceptable voltage drop. I would fit 10mm cables.

The fuses are only protecting the cables, the charger has its own fuses, so fit a pair of 40a midi fuses.
 
PaulRainbow said:
3mm cables for that charger are too small. Not only will they get warm, you will get an unacceptable voltage drop. I would fit 10mm cables.

The fuses are only protecting the cables, the charger has its own fuses, so fit a pair of 40a midi fuses.
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The OP's description of his cable isn't clear - he said "cable diameter as measured is 3mm (Gauge 8)" and I'm not sure whether that 3mm includes the insulation or not.

Mr Sterling's instructions say the charger needs 6mm2 cable for a 2m run, but I think that's an error as the instructions say 10mm2 for a 2m run with the smaller 20A charger! And the instructions don't specify whether the run length is the distance to the batteries or the there-and-back distance.
 
pvb said:
The OP's description of his cable isn't clear - he said "cable diameter as measured is 3mm (Gauge 8)" and I'm not sure whether that 3mm includes the insulation or not.

Mr Sterling's instructions say the charger needs 6mm2 cable for a 2m run, but I think that's an error as the instructions say 10mm2 for a 2m run with the smaller 20A charger! And the instructions don't specify whether the run length is the distance to the batteries or the there-and-back distance.
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AWG 8 has a conductor diameter of 3.3 mm and cross-sectional area of 8.3 mm². (The closest metric size cable is 8.5mm²)

It is rated at 75 amps maximum for a single core and 40 amps maximum for a multicore cable up to 3 cores

If you want to work out the volts drop in any given length then its electrical resistance is 2.1 ohms / 1000 m ( for copper cable)

The nearest AWG size to 6mm² is AWG 10 whichs is actually 5.3 mm² . It is rated at 52 amps for a single core and 30 amps for up to 3 cores. Its resistance is 3.3 ohms / 1000 m
 
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VicS said:
AWG 8 has a conductor diameter of 3.3 mm and cross-sectional area of 8.3 mm². (The closest metric size cable is 8.5mm²)

It is rated at 75 amps maximum for a single core and 40 amps maximum for a multicore cable up to 3 cores

If you want to work out the volts drop in any given length then its electrical resistance is 2.1 ohms / 1000 m ( for copper cable)

The nearest AWG size to 6mm² is AWG 10 whichs is actually 5.3 mm² . It is rated at 52 amps for a single core and 30 amps for up to 3 cores. Its resistance is 3.3 ohms / 1000 m
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Indeed, but as I said the OP wasn't specific as to whether his measured 3mm diameter included the insulation.

There's obviously an error in Sterling's instruction manual too. I'm surprised this hasn't been corrected.

Cable "ratings" are largely irrelevant, the idea is to reduce the voltage drop to an acceptable minimum. As there's so little cable involved, I'd probably go for 16mm2 which would give about 0.1v drop. 10mm2 would give about 0.2v drop. 6mm2 would give about 0.3v drop.
 
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Sigh, here we go again with all the Google answers.

Who cares about current ratings, 4mm2 is rated for enough current, but the voltage drop will be totally unacceptable.
 
The cable is measured across the conductor using a rule, not a micrometer, hence it is an estimate but definitely not less than 3mm diameter and not more than 3.5mm. Below is the table of wire size from the operating manual that came with the charger.

50185530827_997cd76b42_4k.jpg


Okay, use a pair of the midi fuses and holders All Trade Direct 2 X 40 Amp Midi Fuse High Current All Midi Amps 40-150Amp & Fuseholder Stocked: Amazon.co.uk: Car & Motorbike
Increase cable size. I would like to change the cables to 16.0mm2, conductor to optimise the voltage drop but the stud size on the fuse holder is M5 and RS Catalogue states that M5 tubular ring terminal is only good for 10mm2, so I will go for the 10mm2 wire.

RS PRO Uninsulated Tubular Ring Terminal, M5 Stud Size to 10mm² Wire Size | RS Components

Thanks everyone for the help, appreciated. As I don't have a crimper for tubular crimps, I'll get the cables made up.
 
10mm cable is fine, with respect to PVB, 16mm cable is a bit oversize here it won't fit the midi fuse holders and it won't fit the charger terminals either. Voltage drop will only be a touch over 0.1v

I'd be wary of those fuses at £1.99 for two, including post.
 
PaulRainbow said:
10mm cable is fine, with respect to PVB, 16mm cable is a bit oversize here it won't fit the midi fuse holders and it won't fit the charger terminals either. Voltage drop will only be a touch over 0.1v

I'd be wary of those fuses at £1.99 for two, including post.
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As the distance is short, I still think I'd go for beefier cable. It's easy to buy cable terminals for 16mm2 cable which will fit M5 connections, eg here - M5 copper tube terminal ring lug crimp to suit 16mm2 cable

The fuses do look a bit cheap!
 
pvb said:
Indeed, but as I said the OP wasn't specific as to whether his measured 3mm diameter included the insulation.
There's obviously an error in Sterling's instruction manual too. I'm surprised this hasn't been corrected.
Cable "ratings" are largely irrelevant, the idea is to reduce the voltage drop to an acceptable minimum. As there's so little cable involved, I'd probably go for 16mm2 which would give about 0.1v drop. 10mm2 would give about 0.2v drop. 6mm2 would give about 0.3v drop.
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Dont forget we are looking at a 24 volt system .... you can accept twice the voltage drop that you would allow for a 12 volt system
 
VicS said:
Dont forget we are looking at a 24 volt system .... you can accept twice the voltage drop that you would allow for a 12 volt system
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I hadn't forgotten that, Vic, but we're only talking about 3m of cable. Why wouldn't you use something substantial? It's going to cost pennies more than thin cable.
 
BlowingOldBoots said:
Are the Gold Plated fuse holders and blade fuses worth the extra cost?
Click to expand...

Our Sterling fuse holder of that type outlasted the charger, which died at 14 years of age (reasonable lifespan). I've re-used the fuse holder for the replacement charger, as it still looks like new, no corrosion or anything on it. So if you want durable, yes, they last.
 
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