Over-Volting LiPos and SAW Racing

[Fluid]

I'll start this thread to take pressure off the Fire thread. If there is any interest, please post here.





Yes... In the last couple of SAW events I've attended at Legg Lake, there have been launches occurring from down beyond the left-side time trap... giving the boat a straight initial shot through the lights.
The world's fastest FE boat launched from one end of the lake on its record runs. That was years ago, but I was there. That was done to help the driver see the boat's track through the traps rather than to preserve battery power.

Technically, as the SAW competition rules are written today: "Speed running time will commence when a boat is released from the pit..." This has not been enforced at the many NAMBA SAW events I have attended.



In ROAR racing, they tech battery voltage going INTO the event, not after the pass was made. I think this would be a fairly simply way to prevent people from attempting to over-charge their cells...
The extra voltage burns off very quickly so requiring the racer to leave from the pits and make a 180* turn will eliminate any advantage to over-volting. We don't need any more stinking rules - we just need to enforce those we already have.


.

[puttekula]

Keep in mind, the most expensive class in rc-car racing is the stock class. Its now not that bad as it was back in the brush days. But still
bad enough. Whats my point with this? Is there a possibility to max things out, it will be done. No matter of the cost. And if theres a possibility
to start a race with packs "doped", it will be done. If it burns, let it burn... And if theres a rule about starting from a fixed point, everybody else has to do it.
And yes, I know that "doped" packs will dump into the right "voltage range" quite fast (not eve near to linear) but the advantage will be there. And even worse,
the batt manufacturers will produce packs that will have (maybe with some luck) better abilities to withstand overcharging. And the price for those packs, yes youre
right. Very expensive. Is it really that hard to control boats going into water for overcharged batts? Thats the only way to avoid "cheating" and danger due to Lipo fire
caused by overcharging.
Thoughts from a newbie in fe boating , but lived with rc cars since 1986....

[puttekula]

And what happened there... plz remove, someone :smile:

[Rumdog]

Why is it that the extra voltage dumps so quickly?

[keithbradley]

Why is it that the extra voltage dumps so quickly?
It doesn't. I'm not sure where they're getting that from.

[drwayne]

It doesn't. I'm not sure where they're getting that from.
Possibly from the ppl who do so ?.

The extra voltage burns off very quickly so requiring the racer to leave from the pits and make a 180* turn will eliminate any advantage to over-volting. We don't need any more stinking rules - we just need to enforce those we already have.
SAW ..if you start your pass with pack voltage higher than standard. you'd achieve a higher speed..
Leaving the shore with higher than 4.2 allows you a higher V at start of run.
Thus overcharging some correctly consider as 'cheating'.
Ive never read or heard of examples where 4.2V+17% is permissible , as stated on the fire thread by Fluid.

Please direct me to the appropriate rule book that shows me unlearned.
I may wish to rewrite the Au rules !
regs
Wayne

[keithbradley]

Possibly from the ppl who do so ?.



No. If they did, they would know that the voltage doesn't quickly drain off. Lipos are not like nimh batteries where they peak at a given capacitance and then the voltage sharply rises. They continue to store energy the same way they do at lower voltages as long as they remain stable. The "drain off" is directly relative to the amount of energy put into the battery, which can actually be a substantial amount. I don't want to get too specific with numbers because I don't want to encourage stupid behavior.

I am not speculating, I've done it. I'm not suggesting anyone has done it at any event either. I'm just saying it is more than possible to overcharge a lipo, do a lap, and still be over 4.2v/cell. It's stupid and frankly pathetic, but possible.

[detox]

I thought this was a forum where we learn. How do i charge my LIPO batteries to 4.35 volts per cell?

Can i set my charger to NIMH mode then charge while monitoring voltage at balance tap?

Charger should read voltage while charging?

I may try ................. outdoors.

[keithbradley]

Yes, learn.
Learn from my post in the other thread where I already addressed the issue.
You can charge a lipo to high voltages and get away with it sometimes, other times you might charge it slightly high and end up in disaster. There is a maximum stable voltage that you can charge lipos to consistantly, it's 4.2v/cell. I don't know how else to say it. I'm not withholding a secret that you can really charge lipos to xxxvolts every time...it's just the way it is. There's not a big margin for error.

[detox]

Kids, Allways start with a fully balanced and charged pack before topping off.

I wonder how the SAW racers do it?

In NIMH mode my Hyperion charger will charge 1~16 cells (1.2~19.2V).

4.35 volts per cell x 4 lipo cells = 17.4V

...

[Darin Jordan]

Guys... if you overcharge a lipo pack, you will quickly ruin the pack. So, unless you have the $$$ to use a pack once or twice and then toss it, all for a record, then I'd stick to a normal balance charge. I get most of my packs for no-charge thanks to my sponsor, Thunder Power R/C, and I don't have the slightest interest in worrying about getting an extra .xx per cell by this risky practice. Again, learn to tune your boat and work your props. You'll have a much more successful adventure that way!

[drwayne]

Hello Keith

Australia and Eu have 4.2v/cell as the cell limit.
Whatever happens away from 'controlled' sites is of no concern to this thread.

Ive not read or heard of examples where 4.2V+17% is permissible , as stated on the fire thread by Fluid.

Please direct me to your rule book that shows me such is allowable.
No dispute, just for clarity.

Hmm 10S at 4.2V +17% = 12S !!!!!!!!
Id call that cheating, if CD at an event.

regs
Wayne

[Fluid]

No. If they did, they would know that the voltage doesn't quickly drain off... I have, and it did. In the pack I sacrificed, the starting voltage was 4.33 volts per cell. Within 20 seconds it was back to the same voltage discharge curve as the same pack charged to 4.2 volts per cell - same boat, motor, etc. Yes, that's just a one pack example, but it's my experience. BTW I was a nervous wreck doing it, expecting things to burn up....but they didn't for that one test. The pack was then fully discharged and disposed of. And it wasn't easy to get it to overcharge, although I'm not tapped into the group of folks who do this, so my technique is probably 'wrong'. I 'assume' that the practice does come from the R/C car fraternity...don't do it.


Below are the current NAMBA power rules, they are not solid enough to prevent overcharging in all classes.

http://i45.tinypic.com/290rnkp.png












.

[drwayne]

79933

Thank you Ray

here are the Au specs for lipo charging

we have 165gm per cell limit, not mAh ceiling.
W

[Doug Smock]

If you are caught overcharging cells (and if you are you will be) at a IMPBA sanctioned Time Trial, you are going to go home disappointed.:nono:

Class Voltage limits
N 1.2 to 7.4
P 8.4 to 14.8
Q 15.6 to 22.2
S 22.8 to 29.6
T 33.3 to 37.0

1. A voltmeter will be used to measure the total voltage applied to the input of
the speed control(s), un-loaded, with a fully charged ‘pack’ will constitute
technical conformance to a class voltage limit. A plus or minus voltage
percentage of 17% will be allowed.
2. A ‘pack’ is defined as the cell(s) wired in series or parallel or any wiring
combination that is used to provide electrical power to the speed control for
the purpose of driving the electrical motor(s).
a. Only one pack maybe used even if multiple speed controls are used.
b.The pack must be made up of only one type of cell chemistry.
c. In multiple speed control/motor installations the total pack voltage
must be used as the supply input to each speed control. You are not
allowed to tap off voltage or switch a packs’ parallel/series
configuration during operation.
3. Contestants are cautioned to keep their wiring as simple as possible to make
it easy for a contest director/technical inspector to confirm class
conformance. Inspectors may require that batteries and or other
components be removed from the model to make a ruling.
4. All batteries will be removable from the model by use of some type of
connector arrangement. It is prohibited to “hard-wire” in the batteries.
Hard wiring installations is where electrical connections are physically cut
apart or de-soldered to allow removal of the battery.
5. As with any high performance battery, due consideration should be given to
the safe handling and charging of batteries. As a responsible user of high
performance batteries you will adhere to any of the manufacture
recommendations dealing with handling, storage and charging. Some
recommendations for the safe handling, storage and charging of batteries.
a. Charging of battery to be done on a non-flammable surface or in a fire
containment vessel out of the boat.
b.Typical containment vessels may be, but not limited to, fire
blanket/pouch, baking dish, firebrick, clay pot or sand.
c. The contestant will provide a fire suppressant such as dry sand or a
properly rated fire extinguisher.

D.:tiphat:

[detox]

Can i set my lipo charger to 5s (balancer disconnected) to over-volt my fully balanced and charged 4s pack? I will have to watch volt read out carefully.

[Doug Smock]

Can i set my lipo charger to 5s (balancer disconnected) to over-volt my fully balanced and charged 4s pack? I will have to watch volt read out carefully.

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[drwayne]

Thanks Don
That reads the same as down under, except for 2 a) where we allow multiple esc with individual packs .providing total individual cell count does not exceed that class limit.
eg 2x [ 3S to esc] = 6S class

regards
Wayne
AMPBA192
Au

[detox]

I allways wondered why Brian was so fast. I am sure his props have a little to do with it.

[raptor347]

I allways wondered why Brian was so fast. I am sure his props have a little to do with it.

Ah, but the interesting thing is you don't get consistent passes with an overcharged pack. The back up run always sags significantly. You'd never see say a 103.6 mph pass backed up with a 103.1 mph pass (my N2 hydro record run). I'm afraid the speed has nothing to do with overcharging, could be the spinning thing on the back.

The later generation Hyperion chargers can be programed to overcharge the cells, but not by much and does the box ever scream at you when you try it. Lots of warnings on the screen. It seems to degrade the cells in a hurry as well. I've tinkered with it, but found the penalties outweighed the benefits, at least in the classes I run.

Now low current classes like N1 may benefit from overcharging. The high power stuff, not so much.

Just my .02

[NativePaul]

Here at the UK nationals racing under the Naviga rules that apply to most countries worldwide, we have a nominal 4.2v limit with an absolute limit of 4.23v, which prevents significant overcharging but still allows a little leeway as we don't want to be disqualifying honest people that happen to use cheap un-calibrated chargers that could be a couple of mV out either way.
There is random testing on the launch platform via the safety loop sockets which takes very little time at all, I raced in 11 heats last year and got checked 4 times, one of those times they checked everyone in the heat heat and it still only took about a minute. although if anyone would have had a spurious result they would have had to de-tape and get checked across the battery/speed controller connectors, if it failed there (which I don't believe has happened) we could start the race with little delay, but if they pass it does delay things a few minutes as they have to re-tape.