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Master V4 charging to 133.6 V


Elwood

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Got a new master, topped it off 4 or 5 times, darkness bot shows 100% at 133.6 volts each time. Is this most likely a off calibration, or am I losing close to a volt from the charger? I don't actually need the volt, but I don't want to go unbalanced due to the bats never receiving a full charge. If it's always 133.6 is it fine? Just wondering, don't wanna buy a special charger and do each pack, if it's actually getting full and just reading a bit off. Thanks for the replies.

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If it's always 133.6v I'd guess that it's actually 134.4v but that it's just off.

You could also measure the charger output with a multimeter. That measurement can't usually be compared with the wheel reported voltage as they're two different measurement devices. 

You could if you're super careful measure the charge port but this is very dangerous. Do so extremely carefully so that you don't short two pins. 

It won't set anything on fire but you'll likely destroy the port and it will need to be replaced. 

A better idea is to measure the packs individually.

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That's normal behavior for Begode EUCs. They have it programmed to not go to a full 134.4 volts. Their stated rationale is for fire safety reasons, but also it is beneficial for those who live on a hilltop or avid jumpers, to prevent overcharge cutouts. I personally would rather get the full 134.4 volts myself just to get a little bit more range, but it is what it is.

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5 hours ago, WheelGoodTime said:

I personally would rather get the full 134.4 volts myself just to get a little bit more range, but it is what it is.

Yes!! Sweet, sweet range!

Do you know when they started this? Presumably a long time ago already, but I never truly heard of this before.

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I have a Master V2 that is coming up for 2 years old / 4000 odd miles on it, and have just been down to take it off a very long charge, and check the voltage, which, coincidentally with the title of this thread was also 133.6 volts ! If I unplug it now and check again in 2 hours before I go riding it will have dropped to 133.2v or so. If I power the machine on, and roll it out of my house it'll drop to 132.something almost straight away. But then I can do a 25km ride on it and still get back with a voltage of 127 or so, which is still so much spare it's almost laughable...

So having lived with it for over a year now since I put the new charge board in that first did the voltage drop thing it has affected my range and use of the machine not one iota, so I don't worry about it. As it happens I also live at the top of a steep drive, so am even grateful for the extra leeway I get for regen braking right at the start of every ride.

Edited by Cerbera
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1 hour ago, Cerbera said:

If I unplug it now and check again in 2 hours before I go riding it will have dropped to 133.2v

I came up with a new theory last night while riding. It charges to 134.4, but when you turn it on and everything gets charged, you lose about 2/3's of a volt. If I check it, and come back and power up and check it again, it drops like you mentioned by about the same amount. As long as I keep hitting the 133.6, I'll assume it's all good and carry on. Thanks for the replies.

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You can't really trust the wheel voltage readout. It's only really accurate to broadly tell your charge level.

The charger is designed to output about half a volt above the end voltage of the packs (to ensure balancing is triggered dispite tiny losses in cables/connectors). So people that see 134.4v for a split second, could actually in reality be 134.9v, but it then comes down to 134.4v (displayed as 134.0v). 

The opposite could occur. The real voltage is 133.0v but you see 134.4v because the readout has a 1.4v inaccuracy.

You can't really know what the actual voltage unless you measure it with a good multimeter.

Common multimeters are often accurate at low voltages but as our wheels have gone from 67v to 168v we've left the "accurate range" of common multimeters. 

But even with an inaccurate multimeter you can compare the readout with the wheel's own. If they're close together, chances are it's fairly accurate. If they're apart by a bit, one or both of them could be untrustworthy.

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