# how do you calculate voltage threshold?



## losi b (Jul 31, 2004)

*how do you calculate voltage threshold? HELP*

i understand what it is, but, how do you calculate it?
thanx
brian


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## patcollins (Sep 29, 2001)

What do you mean calculate it?

Do you mean choose it?


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## losi b (Jul 31, 2004)

yes.
i have been using vt that were suggested, but i would like to understand how you would determine the best.
i would hope that it is not by trial and error.
there must be some theory..
thanx
brian


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## patcollins (Sep 29, 2001)

Well the higher it is the hotter your batteries get, there is no magic to it. 

You want to set it high enough so your sure your batteries are completely charged but not so high that they will never peak and will explode. 

If your batteries are still cool after they are done try bumping it up, if they are too warm reduce it a little ....go a little at a time and you will be fine.


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## losi b (Jul 31, 2004)

thank you.
i understand the basics.
do you just use trial and error? is that what you are saying, that the battery makers run trial and error until they get it right or is there a theory behind it?
i am asking, because i want to learn how and why.
i don't mean to sound like a jerk, just would like to understand.
thank you for your help.
brian


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## patcollins (Sep 29, 2001)

They usually use some common sense and then adjust from there and run some tests. If you make small adjustments its not like your going to fry a pack by going from 4mV/cell to 5mV/cell. Just dont go from 4mV/cell to 20mV/cell and expect good results.


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## DynoMoHum (Sep 25, 2001)

Losi_b,

For the most part, it's trial and error to determin the best delta peak voltage value to use in the competitive RC vehicle world... This is because all we care about is how fast we can go on the track and little else...

Battery manufacturers (as oposed to battery matchers/re-sellers) probaby have some method for choosing what's best in their minds, and it may even be scientific. However RC racers rarely listen to them, since their goals and ours are rarely the same. Manufacturers are most likely interested in saftey, product life, and things like high output high current max proformance are probably kinda low on their priority list...

Hence... RC racers and RC battery matchers just play around untiull they get what they are after... max proformance.


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## erock1331 (Apr 1, 2002)

I use this rule of thumb, if you are running GP's 3300mah, use a 6 amp .03 drop and it should get the pack about 130 degrees if the pack is about 80 degrees when you start to charge it.
Then when you repeak it should take the pack up to the 140-150 degree range.

You should be good to go.


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## losi b (Jul 31, 2004)

thanks dynomohum.
i was looking for an answer and you said it.
TRIAL AND ERROR!
just doesn't seem logical to fry packs for consumers. they are expensive.
any thoughts on where to look for "vt" calculation formulas?
thanks for your input. (dynomohum) 
brian


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## DynoMoHum (Sep 25, 2001)

Generaly what many of us do, is to listen to what our matcher recomends... or listen to some well known matcher that seems to do well with his sponsored drivers, etc..

It all depends on what you want to some degree... I'm fairly conservitive in the way I do mine... I use .03 volts (total) for a 4 cell pack, and .05 volts total for a 6 cell pack. I typicaly charge at about 6 amps... sometimes slightly higher if I'm in a hurry...

The real key in my opion is not so much what value of delta peak you choose, but in getting your packs to peak just minutes before your race starts, so that they are nice and warm when your car is on the line. About 135 to 145 F is pretty much ideal by most accounts for a GP3300 pack.


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## guver (Jul 31, 2002)

If you want a starting point b-4 trial and error there are some recommendations


Nicads 8-15 mv / cell
Nimh 4-6 mv per cell
small AA rx batts maybe 3-4 mv per cell

Most battery and charger instr will have recommendations along with matcher's websites usually have specs too


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## losi b (Jul 31, 2004)

thanx dynomo and guver.
i have posted this thread on other forums lately and here is the only answer.
so basically, listen to the matchers and the fast guys?
huh
brian


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## DynoMoHum (Sep 25, 2001)

Yup... listen to the fast guys and/or trustworthy matchers... but then some fast guys charge at 10 amps... and you WILL get a wide variety of answers, and they all may have their own pros and cons. In the end you have to decide what's best for you...

A good matcher will find out just as fast or faster then a good racer, because good matchers often have good racers that run for them and they colaberate on finding what works... 

Every time a new cell comes out, it's back to the drawing board... 

Storage and/or discharge techiques are pretty much as important as charge techniques too, so learn about that too... and again you will get many differnt opions and all have pros and cons...


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## losi b (Jul 31, 2004)

thank you dynomo!
i need all of the help i can get.
brian


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