August 18, 2019, 02:41:19 am

RCMF Donations

Enjoy using RCMF? How about a wee donation to help us keep you in the style to which you've become accustomed?

Welcome to RCMF. Please login or sign up.

August 18, 2019, 02:41:19 am

Login with username, password and session length

HV LiPo

Started by Bad Raven, February 08, 2019, 09:51:22 am

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Bad Raven

If you need explanation to the reasoning in this piece, then I suggest you move along please, nothing to see here. No need to inform you are not comfortable with what follows. This is real world experimentation under controlled conditions.

Standard LiPo at end of charge when new will end up around 4.20v. This max voltage attained slowly drops away over use/charge cycles.

HV LiPo are notionally 4.35v.

Currently most HV LiPo for sale seem to be in the 200-750mAh 1-2S range for small quads and micro planes.

With 250g laws looming around the world anything that gets a user more power and/or duration without a weight penalty is a desirable enhancement.

Existing HV and non-HV cells are often extremely poorly marked, so badly that it is sometimes quite hard to see what type a cell is. This extends to felt tip marking of label boxes that wipes off in minutes!

Further, many 1S chargers are often currently quite poor at showing what they are set to, STD or HV.

SO, there is a very definite chance that users will by mistake charge STD as HV. There is enough risk from LiPo handling already, is this additional risk being handled properly by the manufacturers and sellers?  Have to say no.

However, I have been carrying out (very careful!) experiments on such highly likely miss operation, and have found that such "over charging" is not seemingly adversely affecting any of the cells I have tried it on, in fact it is proving on the face of it to be a useful way of enhancing model performance, despite the stated risks. I have used a number of 150mAh, 200mAh and 450mAh 1S, some quite old. None so far have shown any sign of issues, all have given better performance on a range of models after such charge.

Length of testing period so far is over three months, so ongoing but already a reasonable time to comment upon.

I am not in any way advocating this process as a valid or a safe one for general use, the sole reason for posting being to explore others experiences?
The user formerly know as Bravedan........... Well if Prince can do it....................

e-flite_rules

Slightly off topic but a warning about an issue I've had with Hv-Li packs.

The first time I flew my HK Tundra with a 3S Hv-Li pack - Hyperion G7 - I nearly crashed it as it almost immediately went into low voltage cut off.  Investigation showed that the ESC incorrectly recognised the pack as 4S.  So now I know to count the beeps.  If there are 4 I simply run the motor for a few seconds and then unplug and replug. That always gives 3 beeps.  ON THAT ESC.......

Hope this helps.

Bad Raven

Equally, some Flight Controllers (using Betaflight at least) are poor at deciding if the cell(s) attached are 1S or 2S. This can manifest as not arming or permanent low voltage nagging depending on how the FC board is set up. The process is there to check manually and adjust, it just does not help you along the way.

Anyway, to topic. Have not seen the need for HV on larger packs as in nearly all cases better capacity sizing and/or higher C rating is a better solution.  Where HV IS more than useful is with 6mm/7mm and to a lesser extent 8mm brushed motor Tiny Whoops/Whoovers where increased battery weight and or size is not possible and you desperately need all the power/duration you can get within the std cell format.
The user formerly know as Bravedan........... Well if Prince can do it....................