2008 Off road, Lipo

[PaulRotheram]

you cant though.. as the current rule is 7.2v.. and lipo isnt.. so its either one or the other unless the barrier is increased so 7.2 is still allowed.. however i can't see this happening my self as of yet.

[Colinevan]

For me, iv just purchased a trakpower 4900, balancer and new charger dedicated for lipo. Iv purchased this lot specifically for use in my Rb5.

The reason being, i decided a few weeks back to run 2wd and 4wd both on club days. It will give me twice the tracktime, however twice the hassle of another car to get ready. For me the selling point was leave the cells in the car, and just stick them back on charge when needed. No swapping cells over, no equalising, less hassle .

The bonus being, my lipo could be charged weeks in advance and be ready to run without needing re peaking etc. Tbh it was a nightmare trying to run 2 cars as i really had no spare time. If lipo helps its worth the extra outlay in my opinion.

For me personally, less hassle is good, i run brushless for this very reason in both cars, and im now contemplating using a spare sanwa gemin tx rx set just to save swapping the modules over on the Ko and changing the trims etc on model memory. The lipo just compliments the easier maintenance schedule and more time to concentrate on other things.

My aim this year, is to learn to drive more consistently and more importantly to learn how to set a car up (basics only ). Less time with cells more time to learn other things.

Col.

[mark christopher]

Originally Posted by PaulRotheram

you cant though.. as the current rule is 7.2v.. and lipo isnt.. so its either one or the other unless the barrier is increased so 7.2 is still allowed.. however i can't see this happening my self as of yet.

not if the rule is changed to " a max nominal voltage of 7.4 volts" that allows both.
if i turn up at a national and run 5 nimh cells to current weight im legal yes? so as i read it i can run up to 7.2, no rules saying i must only run 7.2

[MarkWesterfield]

the big problem with the lighter weight lipo batteries is that you are reducing the amount of weight on the tires which in turn reduces the size of the contact patch of the tire touching the ground. Suspension settings can not change this, only car weight, downforce (only at high speed) or tire/insert compound changes can change the tire contact patch. Going to an even softer compound tire would not be good if the races were made longer to take advantage of the increase of battery capacity. I feel the best solution would be to leave the existing weight rules in place. Racers could add weight to bring the cars to legal weight for the time being. Car manufacturers could then use the weight savings of lipo to design the car parts stronger and more durable, strong enough to last the longer races that lipo can provide. This would really help bring in new racers with the benefit of longer runtimes and stronger cars.

[DCM]

Originally Posted by mark christopher

where is that info from?
trakpower have at least one lipo thats been charged over 100 time at ten amps and its still not lost any performance, nimh would have done for definate!

All batteries have a cycle life time, it is the nature of the beast. And the harder you use them, the quicker they degrade. Also, the higher the amp rating the higher the cost, so there we go, right away, you can have budget packs, but they just won't have the build to survive.

[sim]

Originally Posted by modelimages

got to get over a couple of problems first, first one is voltage 2 cell lipo is 7.4v bit of an advantage over 7.2v from the nimh so you couldn't really run both types of battery together and the next problem is energy we are barely keeping the speedo's and motors together for 5 minutes using 4200 at 7.2v so adding more volts and runtime equals more heat to get rid of.

and the final point is safety, they do go bang and do so in a big way, both in use and whilst being charged 130 drivers at a national = at least one bang!

i can see it coming but not next year

First, voltage:
NiMH sub-c cells are still referred to "1.2V" batteries because that's their traditional name. If you read the label on matched IB4200 World Championship cells, you'll find many labelled at 1.3V average (discharged at 30 or often 35 amps). I don't see how a six cell pack made out of these cells can be called a 7.2V pack.

2nd, go bang:
Some LiPos do go bang. It's true. I think ultimately there will be a real need for race organisers to sort out which LiPos are safe and which are not (and its probably safe to guess it will be a long and complicated process, involving cloned products, all sorts of certificates and stickers, danger awareness campaigns, and accusations of bribery, corruption and foul play) so that even accounting for user idiocy, the abused packs will just let out the magic smoke instead of exploding.

[DCM]

no, it isn't up to race organisers, it is the umbrella organisation (in the UK, the BRCA) who set construction rules and checks suitability for a cell that has been sent for homologation. Then a race director has a definitive list from which to work from, exactly the same as Sub-C cells.

[joffacn]

In my Helis and Planes I only run Lipos and brushless and have just recently built my first buggy (D4).

The danger with lipos is incorrect charging (Cells Not Balanced), usage (used below 3V/cell) and storage (shorting out, either terminals or internal when cells are damaged).

There is a lot of info in the Aero forums (RCGroups,...)

I vote to keep the weight limit and voltage up to 7.4V nominal.

I am sure over time models will come out to take advantage of the weight distrbution options permitted by lipos.

The Li technology in the new round cells (ABC and others) coming out for power tools seem to be more robust but the V/cell (3.6) is lower than the Li poly gel cells (4.2). These cells are a different size to SubC.

Cheers Jeff

[mark christopher]

it has been said on here that if the weight limit was reduced car set ups would need to change, as cells have increased in weight from say 3300 to 4200's has the set up of cars changed to suit that?

[super__dan]

For me it's the voltage that's the biggest issue. Can they not be made to a nominal 7.2V?

[mark christopher]

nope its how thay are constructed, your seriously saying .2 volt is going to be a noticable advantage on the track?

the main thing is a lipo will hold its voltage over a 5 min run where mimh will drop off, but thats an advantage as it allows all to have good cells

[mark christopher]

DP delete please

[Chrislong]

Originally Posted by mark christopher

nope its how thay are constructed, your seriously saying .2 volt is going to be a noticable advantage on the track?

Y E S

[tc2k]

But isnt a decent matched pack around 1.24v per cell, 6 x 1.24 is over 7.4v.

[mark christopher]

Originally Posted by Chrislong

Y E S

so ur saying chris if i run lipo at 7.4 and you run nimh 7.2 im going to beat you all of a sudden? me thinks not!! u will still woop my ass prob even if u run 5 cell.

the other question, could you use the .2volt with the horse power we have in buggies what would you gain?

[DCM]

could with 4wd, if the cars were to be allowed to go lighter, softer tyres wouldn't rip up and you can, 2wd, no.

[mark christopher]

Originally Posted by DCM

could with 4wd, if the cars were to be allowed to go lighter, softer tyres wouldn't rip up and you can, 2wd, no.

but myself and others are sayijng keep the same weights we have now!

[Chrislong]

Originally Posted by mark christopher

so ur saying chris if i run lipo at 7.4 and you run nimh 7.2 im going to beat you all of a sudden? me thinks not!! u will still woop my ass prob even if u run 5 cell.

the other question, could you use the .2volt with the horse power we have in buggies what would you gain?

Stop trying to ram these bloody things down our throats! Go back to selling double glazing.

7.2v vs 7.4v is clearly different. Regardless of what magic the matchers work on them, the nominal voltages are different, there is a reason.

[vader]

[Chrislong]

Aye, it does feel like a roundabout...