Updated rules for use of LiPo sacks - please read

[SlowOne]

Following changes to the way people are using their LiPos, the BRCA Electric Board have issued the following guidance, and a change to General Rule 4. This means that the new rule applies immediately to all Electric Sections.

SAFETY PROCEDURES WHEN CHARGING/DISCHARGING LiPo/LiFe BATTERIES.

To ALL BRCA Electric Sections, 27.02.14.

Recent communications received have indicated that some competitors are discharging LiPo batteries using a high discharge current between races.
Whilst most of the current batteries are stated to have a 'C' rating that will accommodate this practice, we have to consider that a chemical change is taking place within the battery and of course we cannot rely on the often 'inflated' figures seen on Lipo labels.

If a LiPo flames whilst it is being discharged during a race, then it is unlikely to hurt anything other than the track surface.
If it happens whilst discharging on a pit-table, then the safety concerns take on an entirely different perspective.

Therefore in the interest of safety, BRCA General Rule 4 will be updated to require that :-

"All LiPo/LiFe drive batteries must be in a 'closed' LiPo sack when being charged or discharged. This applies to any discharging procedures, except during a race or when using organiser supplied resistors to correct voltage".

This procedure applies with immediate effect.

As General Rules apply to all Sections, this amendment must be enforced in all Electric Sections.

Best regards,
Paul Worsley. (Secretary, BRCA Electric Board).

[russmini]

Why not:

No Discharging is allowed at a Race Meeting. Other than the natural process that happens whilst racing. Also if Scrutineering deems to high voltage.

And

Charging must be confined to a LiPo Sack and any openings, fully closed/sealed.

[RudolfXC]

If in your final your car breaks near the start of the race, you need to discharge to leave in storage so banning is not practical.

[Chris-S]

When will we see some form of official lipo sack testing, where lipo sacks must meet a minimum standard, rather than hoping that the £15 you've spent might keep a lipo fire contained.

[mark christopher]

Originally Posted by russmini

Why not:

No Discharging is allowed at a Race Meeting. Other than the natural process that happens whilst racing. Also if Scrutineering deems to high voltage.

And

Charging must be confined to a LiPo Sack and any openings, fully closed/sealed.

how do you police weather their being charged or discharged?

stock classes are now discharging at up to 40 amps then charging at anywhere around 10 amps.

you don't need a sack to take off surface charge as document.

[danDanEFC]

Originally Posted by mark christopher

stock classes are now discharging at up to 40 amps then charging at anywhere around 10amps.

Does anyone now why these weirdos do such things?

Why are the on-road guys such crazy cheats?

[mark christopher]

Originally Posted by danDanEFC

Does anyone now why these weirdos do such things?

Why are the on-road guys such crazy cheats?

Yes I know why and it does not make those doing it cheats, unless you can show that in any written ruling....
1c charge rate is a guideline, not a rule, and Defo no discharge rule.

[Justingt5]

Am I missing something here? Why would anyone want to discharge the lipos so they can then charge them again?? I thought they were MEMORYLESS batteries? surely its faster and safer to just keep them topped up between heats?

[danDanEFC]

Originally Posted by mark christopher

Yes I know why and it does not make those doing it cheats, unless you can show that in any written ruling....
1c charge rate is a guideline, not a rule, and Defo no discharge rule.

This reply makes me happy to not be involved with stock/on road racing.

If covering your radio in petrol and setting fire to it made you 0.5secs quicker than the other guy these guys would do it.

[KRob]

There is a train of thought that when using the spec class motors (in blinky remember) the cells are not getting a strong 'work out' and that consistently only using around a third of the capacity means that the best are not being got from the cells.
For info, I only use about 2600mah in an 8 minute race doing 13.5t 12th circuit. The GT12's will be less as they only race 5 minutes.
If discharging a pack at a higher rate keeps the cell in better condition to give better performance then people are going to want to do it.

With brushless and Lipo technology reasonably settled now it's about marginal gains in motor limited classes so whether or not it actually makes a difference is still up in the air - but until people are sure they will try it to see.

[mark christopher]

Originally Posted by Justingt5

Am I missing something here? Why would anyone want to discharge the lipos so they can then charge them again?? I thought they were MEMORYLESS batteries? surely its faster and safer to just keep them topped up between heats?

Its nothing to do with memory effect.

[mark christopher]

Originally Posted by danDanEFC

This reply makes me happy to not be involved with stock/on road racing.

If covering your radio in petrol and setting fire to it made you 0.5secs quicker than the other guy these guys would do it.

A little narrow minded, there are no safety issues being broken, all done withing the manufactures specs, some thing I can guarantee you and others did not do when you charged NiMH....

[mark christopher]

Originally Posted by KRob

There is a train of thought that when using the spec class motors (in blinky remember) the cells are not getting a strong 'work out' and that consistently only using around a third of the capacity means that the best are not being got from the cells.
For info, I only use about 2600mah in an 8 minute race doing 13.5t 12th circuit. The GT12's will be less as they only race 5 minutes.
If discharging a pack at a higher rate keeps the cell in better condition to give better performance then people are going to want to do it.

With brushless and Lipo technology reasonably settled now it's about marginal gains in motor limited classes so whether or not it actually makes a difference is still up in the air - but until people are sure they will try it to see.

Around 1600 to 1800 from a 6700 pack in gt12 for me, the discharge warms the pack to lower the ir

[RobW]

The other reason may be to do with lipos working better when they are warm which discharging them at high rates can achieve. I do remember being at very cold winter touring car meetings back when I did on-road and cold lipos did not perform as well at the start of races – this was in stock class, 13.5T I think. I guess there must be some temperature window where they are at their best?


Rob

[RobW]

Spent too long typing - Mark made virtually same point but much more efficiently!

[fidspeed]

originally flying with early variants of lipos in aircraft early mornng flights in the winter would be limited to stooging around with limited performance

yet after 1 flight and some discharge during the flight (which in turn incurred some warming of the lipo ) then a recharge the performance would be markedly improved
so warming the lipo from whatever means can give a performance increase


dave

[zoaman]

so why not make the rule.Anytime a lipo battery is connected to a charging unit it must be in a sealed fire proof containment. this will eliminate charging, discharging or even checking volts amps checking.easy to police then.

[SlowOne]

Originally Posted by zoaman

so why not make the rule.Anytime a lipo battery is connected to a charging unit it must be in a sealed fire proof containment. this will eliminate charging, discharging or even checking volts amps checking.easy to police then.

Because I could equally discharge the cell on a resistor... which is not a charger... We thought of that!

We don't want it in a sealed container as the LiPo fire involves rapidly expanding gasses. That expansion would pressurise the container which would eventually either explode, or require disposal as a pressurised container. If you relieve the pressure the noxious fumes escape... see below.

We don't want it in a LiPo locker because we can't access the LiPo with sand to extinguish it. The locker relives the pressure by releasing all the noxious gasses into the atmosphere, and without access for the sand to extinguish it, this goes on for many minutes. In a confined hall that would mean evacuation and then measuring the fume levels before we go back in.

In our classes we usually have less than ten seconds covering every ten drivers. When the battery performs better (see post above about flying in the cold) it can shave 0.2s off a lap. Multiply that by the 35-ish laps we do in eight minutes and we have a time improvement of seven seconds, or getting into the higher final.

In sorting this out with the EB and the Exec, we are talking about a handful of people who do this. It isn't widespread, and it isn't something the top ten drivers have done at the two meetings I have checked.

Honestly, it is something the middle order drivers do because they think the top drivers are doing it and they have to do it to keep up. As someone said on this thread or the other one, a few missed apexes and the advantage vanishes.

One thing I can tell you does work. If you are using LiPos in the controlled blinky classes and getting a lot of low-value discharges, then discharging the LiPo to 3.6v and charging it does improve the performance. I do it once after every meeting with each cell at about 1.5C and it works. At the meeting I use the cell without discharge and charge at about 1C or less.

[mark christopher]

ill pm you with some top 12th drivers that do it all the time

[SlowOne]

Not on the chargers they have - 20A is the most an LRP will do! I was talking about the 40A merchants, and the top drivers I know don't have equipment to go to 40A. 10A is 1.5C these days for our cells, so hardly in the realms of the 40A merchants doing it to raise cell temp for best performance.

If you feel their cells before they race, they are room temp, so not getting any advantage from a warm cell to lower IR, etc. I know some discharge, but not at 40A which is where you get the real advantage... or so people think...