How does low batter voltage cutoff work? 48v to ??-cutoff

[OmniosTom]

I am wondering how the motor controller low voltage cutoff works. So you for example you have a 48volt battery and after use the motor controller cutoff turns off the battery after the low voltage ccutoff. So how does this actually work and also one of my main questions is if you are running your bike at 36volt with a 48volt battery, is there a way to have much better range pulling less power than the power rating for the e-bike motor and battery? Is it possible to derate a motors power other than using throttle.
Also how does voltage usage till cutoff compare or interact with say 20Ah ratings? I understand a bit about how batteries work but still have a lot of questions.

 

[flippy]

you dont get more range with your current line of thinking.

its VERY simple if you want to go further: either consume less power by driving slower or make the battery bigger.

you cant increase range by changing a setting to make the battery appear bigger. your car wont drive further if you glue the fuel needle stuck, the tank will still empty.

 

[OmniosTom]

you dont get more range with your current line of thinking.

its VERY simple if you want to go further: either consume less power by driving slower or make the battery bigger.

you cant increase range by changing a setting to make the battery appear bigger. your car wont drive further if you glue the fuel needle stuck, the tank will still empty.

Oh was talking about as stated above using 36volt of a 48volt battery which is a bigger battery while using less power

 

[flippy]

that does not work. if the controller is set to cut off at 40V then a 36V battery is not going to do you mutch good as its will conk out as soon as you accelerate.

 

[john61ct]

using 36volt of a 48volt battery which is a bigger battery while using less power

No, a bigger battery means higher Ah capacity.

You need high voltage for faster speed only.

Using less power, lower Wh per mile, requires going slower, streamlining or losing weight, wind from behind, flatter terrain etc.

Sent from my Nexus 6 using Tapatalk

 

[OmniosTom]

using 36volt of a 48volt battery which is a bigger battery while using less power

No, a bigger battery means higher Ah capacity.

You need high voltage for faster speed only.

Using less power, lower Wh per mile, requires going slower, streamlining or losing weight, wind from behind, flatter terrain etc.

Sent from my Nexus 6 using Tapatalk

Yes understood but still does not explain controller low voltage cutoff for me.

 

[flippy]

Yes understood but still does not explain controller low voltage cutoff for me.

what is there not to understand? when the voltage drops under a certain limit the controller shuts down. its that simple.

 

[Returnformer]

higher voltage isnt necessarily more capacity. think of it like two pipes of different widths. the wider pipe (higher voltage) will give more power, its a bigger flow. the ah is the capacity, thats the length of the pipe. the longer the pipe the longer itll last. if you have two pipes or the same length but different thicknesses, (ie 36v vs 48v) theyll still last the same, just one will give more power while it lasts. true, the 48v starts further from the cutoff, but it gets there faster.

 

[john61ct]

Try asking your question again, but more precisely.

A LVC is just a switch, disconnect the pack to protect it.

The voltage setting used should change depending on the voltage of the pack, so if 3.05Vpc is your desired cutoff

and you are calling a 10S pack "36V" then your cutoff should be set at 30.5V at the pack level

for 13S "48V" it should be 39.65V.

If you put that 48V pack in a system with LVC set at 30.5V then you are being allowed to destroy the pack by continuing to use it down below 2.4Vpc

Doing that would not be smart.

 

[OmniosTom]

higher voltage isnt necessarily more capacity. think of it like two pipes of different widths. the wider pipe (higher voltage) will give more power, its a bigger flow. the ah is the capacity, thats the length of the pipe. the longer the pipe the longer itll last. if you have two pipes or the same length but different thicknesses, (ie 36v vs 48v) theyll still last the same, just one will give more power while it lasts. true, the 48v starts further from the cutoff, but it gets there faster.

So what I was thinking about was to use a 48 volt battery and drawing say 36 volt at the controller thinking it would give be a larger "voltage pool. SO the battery so using a smaller as apposed to a larger water pipe and the amperage would be the same length of pipe with a larger pool in the battery so guess that would be more Ah?

 

[fechter]

Not sure I follow that, but at a lower pack voltage, the bike won't be able to consume as much power or go as fast, so consumption will be lower. Slower bike gets better range.

On many controllers, it's possible to change the low voltage cutoff point by simply changing a resistor. On some of the newer ones, you can change it with a programming app in software.

 

[flippy]

why do all that work when you can just limit the trottle input? that has EXACTLY the same effect.