Lipos

[Jonathan]

Please can I ask,  should lipo batteries be completely discharged before recharging,  or is it ok to top up charge them when they say something like 75 %.

Thanks Jonathan 

[Philip Lewis 3]

No you can just top them up, LiPo's have no memory and this won't do them any harm, on the other had LiPo's should never really be completely discharged anyway.

[Jonathan]

Thank you so very much Philip,  really appreciated. New to these batteries,  on the home straight with my first build in 25 years,  and have gone electric. Best regards Jonathan 

[john davidson 1]

Just to expand on that, the esc (speed controller) will cut power to the motor when in use to prevent damage to the lipo by over discharge.

They can then either be left at  storage charge if leaving for a while , or charged fully ready for use ( but not for an extended length of time as this can cause deterioration) . Important I feel if expensive lipos  , not so much if small capacity cheap ones

 

 

 

[2.4g Shaun]

Jonathan,

a few safety notes re LiPo's:-

 

*Never leave them in the model when not flying and store in LiPo safe bags on a non combustible surface. 

*Never charge them in the model. 

*If they start to swell  or get hot when charging, stop immediately and preferably put outside. 

*Do not charge in the house  or unattended. 

*Never charge at more than the recommended rate. 

*If they do combust don't inhale the fumes as they are extremely toxic.

 

BUT, with care they are a brilliant battery, just respect them and you shouldn't have problems. 

 

I've used them for many years now and never had a problem but I follow the advice.

 

Cheers,

 

Shaun.

 

Edited June 13 by 2.4g Shaun

[John Lee]

Have a read of the attached BMFA's Booklet and Overlander leaflet as a starter Jonathan:

 

Battery Safety Booklet.pdf

 

Overlander leaflet.pdf

 

[Jonathan]

Thank you very much Shaun and John,  I really appreciate your advice and have taken it on board,  I put them on charge this morning in my workshop as I worked,  never left them until charge finished. 

[Jonathan]

I'm a stonemason,  so the charger and battery was on a piece of best quality Welsh slate,  only the best haha 😄 

[Adrian Smith 1]

I  usually charge my lipos the evening before flight time. The actual business of flying usually takes each cell down to 3.7-3.8v (after about 7 minutes) which in my case is 6S lipo. I leave them until the next flying session charge. Now on very rare occasions I don't actually fly that day - in this case waiting for ceramic tiles to be delivered (not happened yet) - how long should I safely leave them fully charged without degrading the battery? I am hopeful of flying by the end of the week though. Obviously, I can discharge them to a balanced storage level on the charger setting, but this take so long with a 6000 mAh lipo. The lipo has a 40C spec on it. . I could just discharge them to an acceptable level, but I am not sure how to, or what discharge rate to set on my charger. Any advice gladly accepted 😀. Thanks. 

 

[John Lee]

This is one of those 'Ask 10 modellers & get 11 different answers' questions!

 

Here's last year's discussion on the topic, which includes my 2p's worth:

 

 

[Adrian Smith 1]

Thank for the info on the thread, John. I see what you mean by different opinions though such is life! Reading between the lines I should be OK to leave them in a charged state for 3-4 days, but beyond that I should really take them down to storage for safety. As I say earlier I rarely comeback from flying with cell voltages over 3.9v  so it's never been an issue up until now. I have UltraPower UP100AC Quad charger and while it's easy to find the discharge setting I am not 100pc sure how to set the discharge rate as in the past I have always used the storage discharge setting  and let the charger get on with it, albeit rarely.

[Chris Walby]

On 13/06/2024 at 18:29, john davidson 1 said:

Just to expand on that, the esc (speed controller) will cut power to the motor when in use to prevent damage to the lipo by over discharge.

They can then either be left at  storage charge if leaving for a while , or charged fully ready for use ( but not for an extended length of time as this can cause deterioration) . Important I feel if expensive lipos  , not so much if small capacity cheap ones

 

 

 

 

Hi John,

 

I don't think you are fully correct with your first sentence. I have not changed ESC settings in many ESC's over the years and on a few occasions have run the lipo (because the ESC allowed me to) down to a point where the lipo was seriously damaged (never had the original capacity or C rating). IMO the ESC Low Voltage Cut-off is to prevent the lipo catching fire, but it does not stop the operator damaging the batteries chemistry and thus performance.

 

There is another thread where people are not overly discharging and they obtain far greater number of charge/discharge cycles. Well worth a read.

[PatMc]

You can usualy program an ESC to choice of High, Medium or Low cut off voltage & also to reduced throttle or to cut immediately the selected setting is reached.

A High with immediate cut would give the battery most protection.

But if the motor is running at full throttle when LVC is reached the battery voltage will higher than if run to LVC at a low throttle setting - i.e. high current draw against low current draw. This is due to the battery's internal resistance.

[Engine Doctor]

On 13/06/2024 at 18:29, john davidson 1 said:

Just to expand on that, the esc (speed controller) will cut power to the motor when in use to prevent damage to the lipo by over discharge.

 

 

 

Only the better quality programable ESC will do that.  Most of the supplied in model a d cheaper plug and play ESC will run until battery is damaged. 

Also on programable ESC's only start a flight on on a fully charged battery as ESC wil think a partly used battery is fuĺy charged and allow it to be discharged to a lower voltage resulting in cell damage. 

I generally run cheaper plug and play ESC's and listen to the powerfade on a fly by. If motor revs an then sags its time to land and I usallly end up with between 20 a 25 % left in battery. This only seems to work or be more noticeable on higher kv motors and  for softer motors just set a timer be more concious of flight times.

 

[Simon Chaddock]

In my experience the cheap "plug and play" ESCs do have an LVC but it is not programmable so you have no way of knowing what it is actually set at. Whilst a single LVC event may not damage the LiPo repeated LVC activation probably will. 

it is thus best to avoid relying on the LVC and actually measure the end of flight at rest battery voltage. If above 3.7V/cell then the next full charge flight can be extended a bit but also take into account the power settings used in the flight.