Author Topic: MP4, max current settings ?  (Read 4760 times)

Offline Amund

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MP4, max current settings ?
« on: September 23, 2015, 08:03:10 PM »
Hi,

I just got a USB cable for my MP4, currently tweaking the min voltage to get the most out of my battery. But I also tried changing from 25A to 30A, and to my surprise it worked, bike runs really well.

Well, I have just bought some LiPo's that will give 100A constant, 200A burst.... could I set the Pie controller to 100A?? I guess not, but what's the limit? Will it burn, or does it have a temperature limit/burn protection?

Offline Bikemad

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Re: MP4, max current settings ?
« Reply #1 on: September 26, 2015, 11:32:12 AM »
The current limit of the Magic Pie 4 controller is 30 Amps and you will not be able to set it any higher than this.

If you are using LiPo batteries without a BMS to limit the current flow, make sure you install a 30 or 40 Amp fuse to protect against accidental short circuits, as the impressive amount of current these LiPos can deliver can also be extremely dangerous.







I was very lucky on that occasion as it could have been a lot worse if the pack wires had burned and shorted causing the battery to explode. You have been warned. ;)

Alan
 
« Last Edit: July 04, 2017, 08:11:25 PM by Bikemad »

Offline Amund

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Re: MP4, max current settings ?
« Reply #2 on: September 27, 2015, 05:28:58 AM »
Thanks for the warning, I already saw these pictures in another thread. Did it also melt through your watt meter, or is that external damage?  :o

I admit the first test ride was unfused, but that test ride went right to a shop to get a fuse and fuse holder, they will be installed very soon, probably today.

Offline Bikemad

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Re: MP4, max current settings ?
« Reply #3 on: September 27, 2015, 11:40:12 AM »
That's the molten blob of copper (that used to be a solid connector pin) that fortunately melted itself into my Watt Meter instead of my leg or the LiPo pack. :o

I was sat on a stool with the LiPo pack and the Watt Meter resting in my lap, and after watching this video of an exploding LiPo pack, I don't really want to think about what might have happened if that the blob of copper had melted into the Pack and caused it to short out.

I now realise how lucky I was, and the damage to my Watt Meter still serves as a constant reminder every time I see it.

The picture of my burnt fingers will hopefully serve as a genuine warning to others.

Alan
 

Offline AdamB

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Re: MP4, max current settings ?
« Reply #4 on: September 28, 2015, 05:41:47 AM »
Wow Alan! Just WOW!

Please tell me that the black marks are just carbon dust/ soot, not catastrophic burns on your hands?!?

If those are catastrophic burns, I'm surprised you still have your hands today! Most doctors would of amputated your fingers min & likely the entire hand/arm!

Even then you are lucky to be alive & not horrifically disfigured & disabled!

Cases like this & others are exactly why I say that LiPo batteries have no place in ebikes! If an expert such as you, can have a brain fart & do something so incredibly dangerous... I don't want to imagine what a newbie who does not know anything about such things can & will do!

Especially because they are so common place & seemingly "safe", it breeds arrogance & false over-confidence! I hate when I hear people saying, they in my cell phone, laptop, etc. So they are safe!

There's a massive difference between what's typically a high quality, expensive, inaccessible, secured, with professionally engineered smart monitoring/management systems, device/battery specific charging & demanding international standards based around tiny capacity (less then 10w or a "C" alkaline battery) typically single (maybe a few) LiPo cell(s) &...

The flimsy, unprotected, exposed, accessible, high capacity, high voltage, high current, poor quality, cheapest, Asian knock off, DIY/unprofessional manufacturing, no or insufficient standards/ monitoring/ management systems based around the biggest cells/packs used in EVs & whatever charger is handy!  It's insult to injury that the ones most likely to use such things are also those least likely to know what they're doing or how to do it!

This is like saying that because we have domestic cats as pets, then we should be allowed to have the giant wild cats as pets; afterall, they are both felines! Surely, it doesn't matter that ones a domestic animal that hunts birds & rodents; & the others a wild predator that hunts humans if it feels like a snack or is bored!

Sure, they are both cats, just like they are both LiPos! No difference at all... Right! ::) I can already hear them saying... But, but, it's my life! Don't I have the freedom to use whatever batteries are right for me & my EV?

Well, how about my & other emergency responders right to be do our jobs safely & save their butts after they are involved in an accident with their EV? What about your neighbours' rights to not have their homes burned down just because we live next to the noob who burns down his house while recharging those LiPos they just have to have!

Or if you won't consider everyone around you, think about yourself as many emergency services department are telling their paramedics, firefighters, police, etc. that if they come on the scene of an collision, fire, etc. & they have legitimate reason to believe that such dangerous batteries are present & pose a danger to rescuers; they should not intervene (unless qualified & can be done safely), just secure the area, call hazmat, etc. & wait for the scene to be made safe before rendering aid! This means you may be dying in your EV or burning in your home but they won't save you, until & unless it can be done safely!

Think about those things, the next time you want to claim your "right" to use whatever dangerous batteries that you feel like using! Besides, there's plenty of better, safer chemistries available that are about as lightweight, powerful, large, capable, etc. as LiPos!

Sure, it maybe somewhat more expensive or lower capabilities or little heavier/larger, etc. but nothing perfect! It's still a lot better then the alternatives!

Besides the point of LiPos was never to be used in such dangerous fashions! Just because each cell wasn't in a hard case, doesn't mean it was meant to be used without any protection! It just meant that you could put all of them in 1 hard case to reduce the weight a bit!

I know some experts will say... I'm not stupids, I know what I'm doing, so it's safe & I should be allowed to! They are missing the point, it's not them, it's all the noobs that see you doing it & think if they can, then I can & then endanger us all! Besides anyone can have brain fart & do stupid things, even experts! Frankly, I think we can all agree that Alan is 1 of (if not) why most knowledgeable experts on this forum! If he can make such a dangerous & costly mistake; anyone can!

Adam