Battery Questions from a noob: Is it safe to temporarily dip below 6.5V on a 2S?

[msf567]

Hi all!

This is my first post and I'm brand new to the hobby, so please bear with me if this question has been asked before, I did some searching and I couldn't find it on my own.

Basically I have battery power telemetry set up on my Losi Mini-B so I get a real-time reading of the battery voltage.

My car is set up with some 1/16 slash tires on them (bigger than the stock), and a Surpass Hobby brushless motor.

On my transmitter, I set my alarm to go off at 6.5 volts (i'm running a 2S lipo), and it dips below that when I go full throttle and then returns to 7.8 etc (safe voltages) when I return to neutral.

My question is: Should i be concerned about this, and set throttle limits so it literally NEVER dips below that number? Or is that to be expected and I shouldn't worry?

If it is of concern, how can I resolve the issue so my voltage stays above 6.8 or whatever is safe? Bigger motor, different ESC, etc...

Thanks for reading, excited to be here!

 

[tntpoof]

what you cutoff is reading .is the battery underload... battery will be ok .. at end voltage you could go lower in cutoff and still be safe.

 

[msf567]

Ok, so I should only be concerned about the battery voltage at neutral?

 

[biggman100]

On my transmitter, I set my alarm to go off at 6.5 volts (i'm running a 2S lipo), and it dips below that when I go full throttle and then returns to 7.8 etc (safe voltages) when I return to neutral.

My question is: Should i be concerned about this, and set throttle limits so it literally NEVER dips below that number? Or is that to be expected and I shouldn't worry?

If it is of concern, how can I resolve the issue so my voltage stays above 6.8 or whatever is safe? Bigger motor, different ESC, etc...

Thanks for reading, excited to be here!

Welcome to the asylum, as i like to say. As for voltages, and, i could be wrong, but running under 3.2V per cell for more than a few seconds isnt good for the battery. As for your transmitter, are you absolutely sure it is reading correctly? Since it is a mini, you might not have room for one, but, if you do, i would get one of these as a backup: https://www.amazon.com/Battery-Voltage-Tester-Monitor-Checker/dp/B08832NJ9Z You can then attach it to the car with velcro, and plug it into the battery as a second way to monitor it while running.

 

[nino]

Voltage drop under load is fine. It seems to be a crappy battery if it drops that much, though. So the way to solve your problem would be to get a better pack. Just make sure it's above 3.2V/cell when done driving.

 

[Greywolf74]

Id go as far to say as long as its not dipping under 6V under load, I wouldnt worry about it. Putting smaller tires on it would help or as Nino said, a better quality battery might help but it will be hard to find one the right size for that car without modding the battery tray a bit.

 

[msf567]

I'm running some protek 2s 1100 mah 50C batteries, so a higher C value you think?

I would have to dip into LiHV, i'll check my ESC to make sure thats ok.

Can I charge those on a balance charger under the LiPo setting and just pretend theyre a LiPo?

As far as smaller tires go, I would love some suggestions as to what kind of tires to get... I'm looking for some road tires for my mini-B, my carpet tires got shredded after one race on asphalt...

 

[Greywolf74]

I'm running some protek 2s 1100 mah 50C batteries, so a higher C value you think?

I would have to dip into LiHV, i'll check my ESC to make sure thats ok.

Can I charge those on a balance charger under the LiPo setting and just pretend theyre a LiPo?

As far as smaller tires go, I would love some suggestions as to what kind of tires to get... I'm looking for some road tires for my mini-B, my carpet tires got shredded after one race on asphalt...

Protek batteries are crap. Look at Liperior (not the Endurance line), CNHL (G+ series), Zippy compact, Turnigy, or SMC.

Not sure about tires, I'm using stock tires. Maybe one of the other mini B people can answer that one.

 

[bill_delong]

This is referred as "voltage sag" where a higher C rated battery will tend to have less sag under load. Lower quality batteries are going to be perfectly fine for a "basher" but there are some "race grade" batteries that are very expensive which are designed to have almost no sag under load. For a basher there comes a point of diminishing return on the expense to sag ratio where a 50C pack is "adequate"

Greywolf has posted some "Sag Ratings" on various brands of batteries here, I would encourage you to bookmark this resource:
https://www.rctalk.com/forum/threads/lipo-comparison-thread-lipo-and-nimh-aas.136829/post-1368906

I have grown to trust Zeee Premiums for my open mod classes as my preferred "best bang for the buck":
https://www.amazon.com/s?k=zeee

For stock racing where voltage sag is crucial I run Trinity White Carbon packs for a "discriminating racer":
https://www.teamtrinity.com/whitecarbon