Battery safety and reputable sellers - do these concepts exist?

[Barefoot_Wanderer]

Hi Everyone,
Because Amazon have excellent buyer protection I took a punt on a 15Ah 48v battery complete with rack for £175. However, when I tested it with a multimeter (after charging the battery to capacity) it only read 36.8v. I know, I know... I was kinda expecting this and well like I say I took a punt. I presume the voltage range should be something like 48v to 55v?

So, in light of this is there such a thing as a safe battery with branded cells? and if so, is it really safe or prone to explode in the night?

Do reputable sellers exist on Amazon/ eBay or anywhere else? (all the batteries are from China)

And if I test a battery for voltage what other tests can I perform to make sure it is, for example, 15Ah - I have an iMax B6 and know how to discharge single cells but I don't believe I can test a large batter with multiple cells all at once- is there a bit of kit I can use for this? But bottom line - is there a way I can thoroughly test my battery when it arrives and make sure it doesn't blow up my kitchen extension?

Minefield? You are not kidding. I'm new to all this so please excuse any naivety- my goal at the moment is to convert our tandem so it can climb those dreaded hills, and I'm even considering assembling ebike conversion kits onto new mountain bikes in the future and selling them on - but only if I get through this minefield with all my limbs intact ;-)

Your thoughts and shared experiences would be very valuable at this stage.

BW

 

[saneagle]

Hi Everyone,
Because Amazon have excellent buyer protection I took a punt on a 15Ah 48v battery complete with rack for £175. However, when I tested it with a multimeter (after charging the battery to capacity) it only read 36.8v. I know, I know... I was kinda expecting this and well like I say I took a punt. I presume the voltage range should be something like 48v to 55v?

So, in light of this is there such a thing as a safe battery with branded cells? and if so, is it really safe or prone to explode in the night?

Do reputable sellers exist on Amazon/ eBay or anywhere else? (all the batteries are from China)

And if I test a battery for voltage what other tests can I perform to make sure it is, for example, 15Ah - I have an iMax B6 and know how to discharge single cells but I don't believe I can test a large batter with multiple cells all at once- is there a bit of kit I can use for this? But bottom line - is there a way I can thoroughly test my battery when it arrives and make sure it doesn't blow up my kitchen extension?

Minefield? You are not kidding. I'm new to all this so please excuse any naivety- my goal at the moment is to convert our tandem so it can climb those dreaded hills, and I'm even considering assembling ebike conversion kits onto new mountain bikes in the future and selling them on - but only if I get through this minefield with all my limbs intact ;-)

Your thoughts and shared experiences would be very valuable at this stage.

BW

You probably forgot to switch it on. That's the sort of leakage charge that you can measure when a 48v battery is switched off. In that case, the voltage you see on the meter depends on the meter's impedence.

If you want to measure the battery voltage, it's best to measure on the charge socket if you can.

 

[Barefoot_Wanderer]

You probably forgot to switch it on. That's the sort of leakage charge that you can measure when a 48v battery is switched off. In that case, the voltage you see on the meter depends on the meter's impedence.

If you want to measure the battery voltage, it's best to measure on the charge socket if you can.

I used a multimeter like this. There is no on/off switch but there is a socket for the charger to plug into - which reads 118v on multimeter (below)
I also measured the same voltage on the charger but at this stage I'm lost and don't know what these measurements mean. Do you think the battery is fine then - how can I test it?

 

[Barefoot_Wanderer]

Ok brain-fart. The battery is turned on with the key and where I was getting a reading of 36v I am now getting 118 still not 48v? Surely I'm not reciving 118v?

 

[Az.]

Did you buy from Amazon?


In general it is better to ask for advice before buying something.

 

[Nealh]

Replace the battery in your meter , this it is a false reading one can expect with tired battery that is no good.

Typically a 48v battery will be 40v to 54.6v , I would expext a battery to arrive at about 50 - 60% chargeso about 48/49v.

 

[Barefoot_Wanderer]

Replace the battery in your meter , this it is a false reading one can expect with tired battery that is no good.

Typically a 48v battery will be 40v to 54.6v , I would expext a battery to arrive at about 50 - 60% chargeso about 48/49v.

I have just had word of the seller who states that " I found that you test it wrongly. you take the tester into AC part, you should take it into DC part to test the voltage."

So, looks like I might be doing something wrong. The lead I used connects to the discharge port which I assumed is the connection leading to my controller (when I get the rest of my kit). For now I want to test the battery is ok.

I will also try replacing the meter battery but I think I'm just not doing it right.

Any ideas?

 

[Peter.Bridge]

I have just had word of the seller who states that " I found that you test it wrongly. you take the tester into AC part, you should take it into DC part to test the voltage."

So, looks like I might be doing something wrong. The lead I used connects to the discharge port which I assumed is the connection leading to my controller (when I get the rest of my kit). For now I want to test the battery is ok.

I will also try replacing the meter battery but I think I'm just not doing it right.

Any ideas?

You need the setting with the V with a straight line above it, not the one with the wavy line above it

 

[Barefoot_Wanderer]

You need the setting with the V with a straight line above it, not the one with the wavy line above it

Oh Thank you so much! Now I get a reading of 53.5v which is normal; I missed the setting thought it was on the right one many thanks for spotting it.

 

[saneagle]

Oh Thank you so much! Now I get a reading of 53.5v which is normal; I missed the setting thought it was on the right one many thanks for spotting it.

You owe the battery supplier an apology unless it catches fire tomorrow.

 

[Barefoot_Wanderer]

You owe the battery supplier an apology unless it catches fire tomorrow.

already done ;-)

 

[Az.]

already done ;-)

Are you giving up on barefoot wandering?

 

[portals]

I would bin the multimeter, you are way more likely to electrocute yourself or set something on fire than you ebike battery catching fire.

I would edit your post title to include "safe multimeter use..." too.

 

[Wayners]

https://www.cyclingweekly.com/news/mega-retailer-amazon-now-liable-for-hazardous-products-sold-on-its-site-including-faulty-e-bike-batteries

Amazon America... Wonder if that is UK as well?