Now Dumping 5KW into the Pie!

[Enpro]

Yep all 12 guage wired and not cheaping out on soldering
I use 35amps fuses on each battery and heavy 500v diodes to make sure my bms's wont trip over the 72v + one massive 75a fuse at the end.

[Bikemad]

I use 35amps fuses on each battery and heavy 500v diodes to make sure my bms's wont trip over the 72v + one massive 75a fuse at the end.

As you'll be running those batteries in series, each battery's fuse must also be large enough to withstand the possible 60A bursts of current, not just the 30 Amp continuous.

From what I can see your phase wires would have to be about 12 guage to safely run 40A DC continuously.

Elmer, when the wheel is turning, the phase wires are subjected to an Alternating Current, and its frequency varies according to the wheel speed and the number of magnets in the motor.
So the frequency of a Magic Pie's phase wire would be 28Hz@60rpm, 56Hz@120rpm or 140Hz@300rpm etc.
Also, because the current from the controller is regulated by Pulse Width Modulation, the phase current would only ever be close to 100% continuous at absolute full throttle, and the current will also reduce considerably as speed increases.

I've found that when you're drawing 3000 Watts, you don't tend to stay at low speeds for very long!

Alan
 

[Enpro]

I use 35amps fuses on each battery and heavy 500v diodes to make sure my bms's wont trip over the 72v + one massive 75a fuse at the end.

As you'll be running those batteries in series, each battery's fuse must also be large enough to withstand the possible 60A bursts of current, not just the 30 Amp continuous.

Thats where the doides come in as they level the current to 36v on each fuse and batttery.

[Bikemad]

Thats where the doides come in as they level the current to 36v on each fuse and batttery.

Unfortunately that's incorrect.

The combined voltage and current of two identical batteries will differ, depending on whether the batteries are connected in series or parallel.

Two 36V batteries, each with a maximum output of 60Amps can be combined in two distinct ways:

• In Parallel, the combined voltage remains exactly the same (36V), but the available maximum current will be doubled to 120Amps.
• In Series, the combined voltage is doubled to 72V, but the maximum current will remain the same (60Amps).

In the above circuit, the diodes are there purely to protect the Battery Management System (BMS) and they won’t pass any current whatsoever, until one of the BMS units is activated, disconnecting the battery it is protecting.
When this happens, the diode that is fitted in parallel with the disconnected battery will provide an alternative path so the current can continue to flow from the other battery.

With parallel batteries, the load from the motor is divided equally between the two batteries, so if the motor was drawing 60Amps, each battery would only be supplying 30Amps.

With series batteries, the load from the motor flows directly through each of the batteries, so if the motor was drawing 60Amps, each battery would also be supplying 60Amps.

In a series circuit, the current is always equal throughout the entire circuit, which is why each fuse needs to be large enough to withstand the possible 60A bursts of current without accidentally blowing. A 35Amp fuse fitted in series with a 75Amp fuse and a 60Amp load is a bit like having a weak link in a strong chain, and I think we can all guess which link will be the first to fail when the chain is subjected to an excessive load.

Alan
 

[Enpro]

yeah you might be right..
I originally bought the fuses for the Magic Pie internal controller thats why they're only 35a.
So how many amps would you suggest then?

[Enpro]

Okay now I got another problem.
I'm getting 79.1 volts out my battery's in series which I think its great but can my controller handle that much volt?
One my battery's is actually delivering 41volts instead of 36

Would a voltage regulator do any good?

[Bikemad]

So how many amps would you suggest then?

The fuse must be large enough to handle the peak current that your controller will draw (or what your battery can supply), but this will obviously depend upon which controller you're using. Although your batteries are rated as 60Amps max, it's possible that the current could be higher than that for a split second under excessive load before the BMS responds and limits it.

I would suggest fitting a 75Amp fuse to each battery to start with and hope that the peak current drawn by the controller won't be quite that high.

I'm getting 79.1 volts out my battery's in series which I think its great but can my controller handle that much volt?
One my battery's is actually delivering 41volts instead of 36

Would a voltage regulator do any good?

The 36V batteries can be around 42V when fully charged, which would be 84V in total, so a 72V controller should be able to cope with this voltage without any problem, but the standard Magic Pie controller would not.

A voltage regulator/convertor that can handle the amount of current you will be using would be difficult to find and very expensive to buy.

Alan
 

[Enpro]

Okay I got some problems...
I just took a couple of test runs with my new controller.
First 30 seconds I can hit full throttle and it accelerates like a beats.
Then it cuts power. The only way to regain power is switching one of the battery's off (doesn't matter which one) .Restarting controller only doesnt work.
Then it starts cutting of at 50% throttle and after a like 3 minutes of half throttle riding it starts cutting at at 25%.
I leave it rest and cool down for a while (30 minutes) still only 25% throttle max.
I recharge the battery for 15 minutes, bang 100% throttle back?
I mean if its just the bms that cuts power at a certain strain it should cutoff power right from the start no matter if its fully charged right?

Bms cutoff or bad battery?

[e-lmer]

This could be a combination of internal resistance differences in the packs.
Would it be possible to hook up a pair of cheap Volt meters to the packs and watch what happens
when it cuts out?

[Enpro]

i only have one voltmeter but one of the packs has indeed a much higher voltage.
One measures 41v and the other only 36v?
The endless sphere forum tells me the golden motor batery's cant handle the amps but now it starts to shutdown even at 10% throttle after like half a mile riding.
The first couple of meters are beast and it even handles full throttle for a moment but then it starts to shut down.
Even when I leave it "cooling down" I cant do full throttle, But if I hook it backup to the charger for like 10 minutes it does.

[Enpro]

Okay problem solved, A death battery after all.
And OMG! Scary and I'm not the type thats easily scared of fast vehicles but this is just unbelievable!
I'm seriously too scared to push full throttle longer then 5 seconds.   
Autowheelie is no problem.
It accelerates just like the stealth bikes bomber even without hall sensors.
Thx for all the help.

[Bikemad]

It's good to see you've solved the problem, but it's unfortunate that it turned out to be a faulty battery.

Do you know how many Amps your controller is actually supplying?

Alan
 

[Enpro]

Its the 45 amps version so I guess about 45 ? Maybe a little more because there is about 80/82v running trough it.
All I know it has so much torque that hanging behind the saddle and accelerating full throttle is instant wheelie.
I still haven't connected the hall sensors yet but I have this "latency" in the throttle.
It starts off almost a second after I touch the throttle and the same thing happens when I release it which can be very dangerous.