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Single 18650 mod fuse question
- Thread starter hanneshbv
- Start date
Too low. I would look at a 35 amp fuse. If you are going to build low builds that use 30 amps (on a VTC4 Hopefully) then you need protection at that threshold. You might want to consider that the fuse will add a bit of voltage drop to the circuit since the function of the fuse is to break when the current rating is exceeded. In essence, the fuse will add resistance to the circuit.
the amp ratings on the fuses also come with a voltage rating.
you have to consider this when adding a fuse.
the best way to check if it works like you want is to bench test it.
there's no simple answer when using atypical voltages.
easy way is to use a power supply that will give constant voltage but varies current.
put a fuse in series w/ a high wattage 1 ohm load and start jacking up the current until the fuse blows.
then do the math.
These power supplies are used in repair/development since if a component starts to break down or is bad, the panel meters that monitor the V and A will start to jump and allow troubleshooting before a board gets damaged. Ie, the board traces acting like fuses.
battery sag or drop is a product of chemical reactions in the battery in relation to load.
the higher the load, the more the potential sag (depends upon battery design).
the more resistance in the circuit, there is a reduction in current.
a mechmod has a lot of potential places where resistance can occur.
the mosfet eliminates the biggest one (switches getting hot from low resistance oxidation from arcing)
if you measure V of a battery, then put a 1 megohm resistor in series, it will read the same voltage.
that hasn't changed.
but, the amount of current flowing through that circuit will be diminished.
current = heat.
you could short that circuit w/ the resistor, it will not even get warm.
saying that, adding fuses is like adding more low resistance heating coils to circuit.
those fuses have to melt to stop a short.
if the batteries do not have enough residual energy, they may not be able to melt the fuse too (batteries have been used a bit before short occurs).
fuse resistance will reduce current to coils.
it will also lessen V sag since current will be limited by adding resistance.
there are other types of non-parasitic fuses that will detect a short without stealing power - like the ones on protected cells.
inline fuses and such are useful in circuits where there is an undimishing power supply - like something plugged in mains or a car that has a huge amp capacity battery with multiple low current circuit loads on it.
hope you followed this and it makes sense.
you have to consider this when adding a fuse.
the best way to check if it works like you want is to bench test it.
there's no simple answer when using atypical voltages.
easy way is to use a power supply that will give constant voltage but varies current.
put a fuse in series w/ a high wattage 1 ohm load and start jacking up the current until the fuse blows.
then do the math.
These power supplies are used in repair/development since if a component starts to break down or is bad, the panel meters that monitor the V and A will start to jump and allow troubleshooting before a board gets damaged. Ie, the board traces acting like fuses.
battery sag or drop is a product of chemical reactions in the battery in relation to load.
the higher the load, the more the potential sag (depends upon battery design).
the more resistance in the circuit, there is a reduction in current.
a mechmod has a lot of potential places where resistance can occur.
the mosfet eliminates the biggest one (switches getting hot from low resistance oxidation from arcing)
if you measure V of a battery, then put a 1 megohm resistor in series, it will read the same voltage.
that hasn't changed.
but, the amount of current flowing through that circuit will be diminished.
current = heat.
you could short that circuit w/ the resistor, it will not even get warm.
saying that, adding fuses is like adding more low resistance heating coils to circuit.
those fuses have to melt to stop a short.
if the batteries do not have enough residual energy, they may not be able to melt the fuse too (batteries have been used a bit before short occurs).
fuse resistance will reduce current to coils.
it will also lessen V sag since current will be limited by adding resistance.
there are other types of non-parasitic fuses that will detect a short without stealing power - like the ones on protected cells.
inline fuses and such are useful in circuits where there is an undimishing power supply - like something plugged in mains or a car that has a huge amp capacity battery with multiple low current circuit loads on it.
hope you followed this and it makes sense.
Thanks for this explenation. I think I pretty much get it. Altough its hard because english is not my native toung.
So there is no way of calculating wich fuse is good for a certain battery?
That bothers me as I would like to keep it safe. Thank you
Verstuurd vanaf mijn LG-D855 met Tapatalk
So there is no way of calculating wich fuse is good for a certain battery?
That bothers me as I would like to keep it safe. Thank you
Verstuurd vanaf mijn LG-D855 met Tapatalk