Unbranded battery isolator switches

[blackrose]

I just bought one of these cheap generic battery isolators from eBay which is a copy of the BEP mini isolator and I have to say the quality looks just as good as the genuine BEP isolator cluster I fitted to my batteries about 10 years ago. But is it a mistake to judge the quality just by looking at it?

 

The continuous rating is 275A rather than the stated 600A. I'm not sure where that comes from? Maybe they list it as 600A as that's approx halfway between the continuous and intermittent ratings?

 

Edited January 9 by blackrose

[IanD]

So it says 600A on the headline, 300A "working current" on the sticker under the switch, 275A "continuous rating" in the text.

 

Any or none of these might have the same rating as for the BEP isolator, there's no way of knowing, There's a lot of cheap copycat Chinese junk on the market, no doubt some is cheap and OK and some is cheap and nasty/counterfeit, the issue is how to tell which it is... 😞

 

Here's an example for the exact BEP switch you mention, and a melted cheap copy which looks just like the one you posted:

 

https://marinehowto.com/counterfeit-electrical-components-just-say-no/

Edited January 9 by IanD

[nicknorman]

The sorts of somewhat “invisible” things that can be the difference between pukka expensive  and cheap copy are:

 

Type of plastic especially the temperature at which it goes soft. Lots of current flowing inevitably creates heat in the slight resistance of the switch contacts. If the heat softens the plastic, it all goes to mush.

 

Thickness of conducting metal bits. Too thin = too much resistance = too much heat.

 

Type of plating on the contacts. Poor quality material will likely corrode over time giving high resistance connection = more heat. Poor quality material is also likely to be eroded by arcing when the switch is operated, building up oxide layer which is not conductive.

 

Contact action - if the contacts are just pressed together, it’s easy for dirt to create a bad connection. A wiping action is better.

[IanD]

8 minutes ago, nicknorman said:

The sorts of somewhat “invisible” things that can be the difference between pukka expensive  and cheap copy are:

 

Type of plastic especially the temperature at which it goes soft. Lots of current flowing inevitably creates heat in the slight resistance of the switch contacts. If the heat softens the plastic, it all goes to mush.

 

Thickness of conducting metal bits. Too thin = too much resistance = too much heat.

 

Type of plating on the contacts. Poor quality material will likely corrode over time giving high resistance connection = more heat. Poor quality material is also likely to be eroded by arcing when the switch is operated, building up oxide layer which is not conductive.

 

Contact action - if the contacts are just pressed together, it’s easy for dirt to create a bad connection. A wiping action is better.

Indeed. Like this...

 

 

Edited January 9 by IanD

[Adam]

The switch feels "soft" and often rotates past its stop. We use them on trailers at work to isolate 12v winches, they seem to stand up to the hammering up and down salty roads.

[blackrose]

6 minutes ago, IanD said:

Here's an example for the exact BEP switch you mention, and a melted cheap copy which looks just like the one you posted:

 

https://marinehowto.com/counterfeit-electrical-components-just-say-no/

 

Thanks, I notice they keep talking about "fake" electrical items. However unless an item actually falsely states it's made by a particular manufacturer it's a copy rather than a fake.

 

I wonder what the stats are on numbers of melted generic switches compared to branded? 

[IanD]

9 minutes ago, blackrose said:

 

Thanks, I notice they keep talking about "fake" electrical items. However unless an item actually falsely states it's made by a particular manufacturer it's a copy rather than a fake.

 

I wonder what the stats are on numbers of melted generic switches compared to branded? 

I don't know, presumably the cheap copies fail more due to corner-cutting in construction/materials. With no name or reputation to worry about, why spend more building it than you absolutely have to?

 

However for high-current circuits, given what can go wrong I'd always prefer to go with a reputable supplier/manufacturer not a generic one off eBay -- saving a few quid doesn't seem worth the risk.

 

Others may think that price matters more, and it'll probably be fine.

 

P.S. The pukka BEP one is about £60 compared to £8 for the copy -- I leave it to you to speculate why... 😉 

 

https://www.bottomlinemarine.com/prod_cat/P_bep--battery-switch-onoff-48v-max-600a-cont-bulk--720b_19678.shtml

Edited January 9 by IanD

[blackrose]

The weight and quality of the materials in the isolator I've bought do look good so someone is obviously concerned about it. I might be wrong of course. If it looked like crap I wouldn't use it.

 

I also noticed that "Marine How To" are themselves sellers on Amazon so while I'm sure their advice is good, I can't help thinking they might be slightly biased and alarmist. After all, there are loads of boats out there with really basic crap battery isolators in their engine rooms and nobody seems to worry about that.

 

 

Edited January 9 by blackrose

[GUMPY]

I've used several of that type of switch and not had a failure, never bought a BEP one but never bought quite as cheap as that one.

 

[magnetman]

1 hour ago, blackrose said:

I just bought one of these cheap generic battery isolators from eBay which is a copy of the BEP mini isolator and I have to say the quality looks just as good as the genuine BEP isolator cluster I fitted to my batteries about 10 years ago.

 

Out of interest why did you buy this? 

[IanD]

13 minutes ago, blackrose said:

The weight and quality of the materials in the isolator I've bought do look good so someone is obviously concerned about it. I might be wrong of course. If it looked like crap I wouldn't use it.

 

I also noticed that "Marine How To" are themselves sellers on Amazon so while I'm sure their advice is good, I can't help thinking they might be slightly biased and alarmist. After all, there are loads of boats out there with really basic crap battery isolators in their engine rooms and nobody seems to worry about that.

 

 

Like I said, you pays yer money and you takes yer choice... 😉 

 

Of course there are loads of boats out there with no problems because that's how component quality works -- and also in most cases they're probably not stressed to close to the full current. That's of little consolation if you're unlucky and operate at high currents and the switch burns out. Same principle as absolutely anything, cheap is sometimes good and sometimes nasty -- paying more doesn't *guarantee* getting something better, but it definitely decreases the chances of getting a dud.

 

For example you can pay top whack for Victron gear which is well-designed and supported and has a good reputation for reliability and support, or pay much less for no-name gear from China. Similar specification, seems to do the same job, may well be fine (do you feel lucky, punk?) -- or may die if you push it near the (dodgy) specification limits, then you find there's little support/spares/documentation so it can't be fixed.

 

Marinehowto may be slightly alarmist, but they also have many years of experience in these areas, especially electrics -- they don't sell anything any more since Rod had a stroke, and the site isn't updated as much as it used to be, but there's still a lot of useful information on there.

[nicknorman]

43 minutes ago, GUMPY said:

I've used several of that type of switch and not had a failure, never bought a BEP one but never bought quite as cheap as that one.

 

 

Have you operated them for a while close to its maximum rated current? If the switch only has to pass a few amps for some lighting and a pump, I'm sure they are fine (until they corrode after several years) but if you are going to put 200A or so through it for an inverter etc, I wonder how long they would last?

[GUMPY]

12 minutes ago, nicknorman said:

 

Have you operated them for a while close to its maximum rated current? If the switch only has to pass a few amps for some lighting and a pump, I'm sure they are fine (until they corrode after several years) but if you are going to put 200A or so through it for an inverter etc, I wonder how long they would last?

Over the years up to about 1.5kW  using various inverters in various installs.

Present one is on a 1.2kW inverter in the caravan for the kettle and the toaster.

[Ianws]

"Kill For Knob" in the item title doesn't sound promising.

[magnetman]

I suppose unbranded can sometimes be better than branded 

 

[blackrose]

4 hours ago, magnetman said:

 

Out of interest why did you buy this? 

 

Because originally I thought it was a BEP switch just from the shape until I looked at the ad more closely. Then I thought it's cheap enough to buy one and have a look.

 

I'm only planning on putting less than 50A through it between my 70A alternator to the LA battery going to a 50A B2B charger/lithium batteries. 

Edited Thursday at 23:12 by blackrose

[Tony Brooks]

8 hours ago, blackrose said:

I'm only planning on putting less than 50A through it between my 70A alternator to the LA battery going to a 50A B2B charger/lithium batteries.

 

 I would not want to use an unknown switch in that application because if it opens circuited while conducting, the alternator is at risk.

[blackrose]

50 minutes ago, Tony Brooks said:

 

 I would not want to use an unknown switch in that application because if it opens circuited while conducting, the alternator is at risk.

 

Any new switch is an unknown switch in the sense that anything can fail. While it's true that the chances of a branded switch failing is reduced it can still happen. 

 

I'm going to use the switch based on the quality I perceive from looking at it. As I said previously, there are thousands of boats out there with really cheap, poor quality switches between their alternators and batteries and nobody seems to think it's an issue.

Edited Friday at 08:53 by blackrose

[Ray T]

My observations from the boating world, various disciplines,  "Buy cheap - get cheap."

I always go for the best branded equipment I can afford.

[blackrose]

10 minutes ago, Ray T said:

My observations from the boating world, various disciplines,  "Buy cheap - get cheap."

 

 

Yes, that's generally the case, but occasionally I've bought cheap and got good quality.

[cheesegas]

15 minutes ago, blackrose said:

I'm going to use the switch based on the quality I perceive from looking at it. As I said previously, there are thousands of boats out there with really cheap, poor quality switches between their alternators and batteries and nobody seems to think it's an issue.

It's difficult to perceive quality without opening it up though, and most cheap ones are riveted together.

 

Cheap isolators used in the engine start circuit tend to fail fairly often. They go high resistance, meaning you see 12v at the starter motor until you turn the key and then just get a clunk as the isolator won't pass the high current needed. Trying to jump start won't work because of this. 

[magnetman]

17 minutes ago, blackrose said:

 

 As I said previously, there are thousands of boats out there with really cheap, poor quality switches between their alternators and batteries and nobody seems to think it's an issue.

Thats interesting. I've never had an isolator between alternator and batteries. 

 

Did you mean starter motor and batteries? 

 

 

As mentioned above putting cheap switches in the line to the starter motor very often causes problems because of the enormous current draw. 

 

Current is like water. It will find the flaws. 

 

 

I'm going to be getting a battery switch for one of the launches. 

 

I came across that one but it just looks wrong to me. Its not the price its just that the actual article to me looks tinny and puts me off. 

 

 

 

 

 

I prefer this one as it looks better. Might still be crap inside to be fair. I think it is a copy not a real Blue Sea as they are more expensive. 

 

These copy things are interesting. I use Anderson SB50 (type) connectors on the floating electric beer drinking platform. I have had failures with the cheap copies because the pieces of spring steel used to hold the terminals in place are not proper spring steel. They lose their grip and provide a bad contact leading to overheating. 

 

Cost cutting has interesting effects. 

 

[Tony Brooks]

47 minutes ago, blackrose said:

As I said previously, there are thousands of boats out there with really cheap, poor quality switches between their alternators and batteries and nobody seems to think it's an issue.

And we know they fail on a regular basis. Not just engine battery isolators, but also domestic ones when no inverter is involved, but your boat so your decision.

[cheesegas]

4 minutes ago, Tony Brooks said:

And we know they fail on a regular basis. Not just engine battery isolators, but also domestic ones when no inverter is involved, but your boat so your decision.

The Chief Bodger on one of the 12v Facebook groups recommends wiring the inverter directly to the battery via a fuse, no isolator, because he seems to think that every isolator switch will fail with the current draw. In reality, he's admitted to using only cheap isolators as he thinks the Blue Seas etc are a waster of money...

 

There's a lot of misinformation out there! A 200a fuse will happily pass 250a for a good few minutes, so in the event of an internal failure with the inverter you potentially get 3kw of heating power without the fuse blowing and no way to easily isolate it.

[magnetman]

I prefer a pair of good wire cutters to isolator switches.