Runtime calculation and question for the guru's - RC-Monster Forums

jzemaxx · 01:26 PM

Ok guys, ran this weekend in a 30min A-main Pro truggy class. I'm running a 2200KV Mamba system. Ran exactly 15 mins and then did a battery swap as my manditory stop. The peak voltage on the charger when charged was 12.68V....after 15min's they were at 11.32V. What kind of runtime could be possible if I would have not made a stop?? Typically under load the packs will cut off right at 10V. Could I have made it close to 30mins without doing the swap?

Also will Auto-lipo LVC cut off sooner then say setting the LVC to cut off at say 9V?

MetalMan · 05.31.2009, 01:27 PM

Typically a battery which has been run down to an appropriate level should bounce back to at least 3.7v/cell, which is 11.1v of course. I think you might have had a couple more minutes left, but certainly no more than that.

jzemaxx · 05.31.2009, 01:33 PM

Quote:

Originally Posted by MetalMan

Typically a battery which has been run down to an appropriate level should bounce back to at least 3.7v/cell, which is 11.1v of course. I think you might have had a couple more minutes left, but certainly no more than that.

My LVC though when I have ran it bashing around when it does cut off and when I hook it back to the charger I always see it at around 9.9V. I figured from 11.32V to 9.9V before it hit cut-off should at least get me another 5-10 mins...maybe??? Also keep in mine this is a 3S battery...not 4S.

SpEEdyBL · 05.31.2009, 01:38 PM

50% charged for lipos is around 3.8 volts per cell at rest. The good thing about my hyperion charger is that it tells you what percent charged your pack is based on its voltage. But even if you were only able to use 50% of the pack the first 15 minutes, you will likely need more the second half, as the voltage is lower and you will need more throttle to get the current up and get the power you need.

Patrick · 05.31.2009, 01:40 PM

How many mah's did they take to fully recharge?

MetalMan · 05.31.2009, 01:44 PM

Quote:

Originally Posted by jzemaxx

My LVC though when I have ran it bashing around when it does cut off and when I hook it back to the charger I always see it at around 9.9V. I figured from 11.32V to 9.9V before it hit cut-off should at least get me another 5-10 mins...maybe??? Also keep in mine this is a 3S battery...not 4S.

What batteries and what do you have the LVC set at? Typically higher "C" batteries should be used with a higher LVC (like 3.3v/cell). 9.9v rebound voltage is a bit low IMO.

jzemaxx · 05.31.2009, 10:21 PM

The LVC is set to auto Lipo on the MMM. I think that is 3V per cell?? The batts are 3S Zippy flightmax 20C 5000mah.

05.31.2009, 10:59 PM

are you only running 3s in your truggy? or 6s

What's_nitro? · 11:10 PM

Quote:

Originally Posted by SpEEdyBL

50% charged for lipos is around 3.8 volts per cell at rest. ... But even if you were only able to use 50% of the pack the first 15 minutes, you will likely need more the second half, as the voltage is lower and you will need more throttle to get the current up and get the power you need.

You read my mind.

Finnster · 06.01.2009, 08:38 AM

What I would do is figure out how many mah you put back in, divide that by the runtime (mins.) Then you can figure out how long a full pack will last.

You can even normalize to Watthours by multipling by pack voltage. Ie, If you are using 300 mah/min, running 6S (22.2V) then you are using 6.7 Wh/min.
I typically use 5.8Wh/min or so. Its then easy to figure out runtime on any setup, regardless of the voltage (ie 10S vs 4S)