Its not just time at the meeting, its time beforehand too. When racing weekly meetings and trying to charge batterys during the day.

I dont think I will be going Lipo as I dont think it is needed in cars helicopters or planes maybe. As for being stuck in the 80s that is defo me as I have decided to ditch brushless and go back to brushed. Brushless to powerfull for me and my driving has gone backward.

I see no reason not to move to Lipo's once they are 100% idiot-proof, I'm looking forward to using them purely because of the lighter weight. Quicker acceleration/direction change, less wear on things; including tires, whats not to like? They will make the cars handle differently but thats nothing a change in setup won't fix, less pack and softer springs would be all thats needed. Adding weight to a car to make it handle properly is wrong if you ask me, if you're at the weight limit and you are having to add weight to the car either your setup or the cars design isn't right.

The extra voltage is a bit of a problem and would mean it wouldn't really be fair to run Lipo's and NIMH's togeather. Though there's nothing stopping us making the cars a bit of a handful to drive with NIMH's and brushless currently, especially in 2wd.

One battery making an r/c car faster over another battery isn't really an issue. Nimh have this problem now, IB4200's are faster than the old gp3300, and everybody has IB4200's in their pits, so nothing will change with the 7.4 lipo batteries. The fast drivers will still be fast, the slow drivers will still be slow. One big problem I see is that its very easy to permenantly damage a more expensive lipo pack by running it under 3 volts per cell. Lipo cutoff speed controls are not enough of a standard yet.

I think keeping the minimum weight the same, and setting a future date far enough ahead for lipo legalization so everybody has plenty of opportunity to learn, buy, and adapt to lipo is the way to go. Say if the date was July 1st, 2008 for 7.4 volt 6000mah capacity lipo to be legal, I think the switch would go over smooth. Thats a year to buy a charger, batteries, and lipo freindly speedo's. I think a timeframe to a standard is what is needed.

Richard,

Softer springs and less pack will not fix the amount of weight loss. The contact patch of the tire is smaller with less weight. You'll need softer compound tires and inserts to regain the traction as well, softer compound tires will wear faster (the car is still going the same speed), so you'll be right back in the same spot as far as tire wear.

Remember you have less weight to move around... ;)

but that weight is needed for the current tire designs to work correctly.

Er.... certainly in the UK tyre design has not changed as cars have got heavier, and it would be the same for everyone anyway.

G

just to point out im answering questions not looking to arguee............chris/dcm!!:)
there is no discharging/equalizing/charge from flat, time is saved by finish your run, marshal (allow pack to cool) plug in charger and top up, so you can turn car round far quicker.
im lucky and have 4x lipo (which i loan 2 out for trial to anyone.) but in theory i could turn up with 4 packs and run a days racing without taking a charger and have the same performance, dont think i could with pre charged nimh charged the week before.


you can buy seperate voltage cut offs, novak, trakpower,jperkins and others all do em. when 6 volts is reached they cut the radio, i have used trakpowers and for a few seconds it stutters the motor then shuts the speedo down via the reciever link, they are relativly cheap, small and light

howe about chatting with some mates?;)

For me, that needs to be built into the pack not an add-on extra, as the low voltage can cause dire affects on the cell, so for a safety stand point, that needs to be fool proof, plus hard casing, then I think they would be viable as a cell, but until then, there is still a lot of reliance on peoples common sense.

To say that we won't have to equalise lipo's is just stupid. There are two cells in a pack and there are already equalisers on the market. Ensuring both cells are the same will be a performance advantage.

I'm sorry, but if you are running the same tires surely you have the same contact patch, but less pressure. However, as there is less weight to move around you don't need as much pressure.

As batteries have got heavier I have not seen a harder compound released.

FYI

At regional level you can amend the rules to suit under serton sections this being one if you take time to read the rules.

We allowed brushless to run 2 years before they became BRCA legal in our region so people could run with them if they turned up. I for 1 would not stop these battery's being used in the region as long as they do not give a health problem.

The reason for falling numbers at club level is many fold one being and the main one is there is not enough juniors U13/U16 coming into the sport this is the biggest fall in numbers, Dads have other things they wish to do with there time.

If you put a proposal into the BRCA it will be discussed at the AGM, you as a proposer will be able to put your piont of veiw across, how well you sell it is down to you. It will also be discussed at commite before hand.

I know this has been mention before but you will get a fare chance for your proposal.

If you do what most people do:- Nothing then carry on and moaning.

not so
trakpower have a pack thats done over 100 cycles in a car and its still no diferent,

however you do not have to equalize lipo prior to charging you balance lipo and it will become the norm as good lipo chargers have it built in and the add ons balance the pack but its done whilst charging so it does not alter the cool/charge time

what region are you in?

Chilton mid south

i agree with most of above but to me adding the cut off to the pack is not a forward move,
1/ it will increase the cost of each pack
2/ your forcing drivers who have a lipo speedo to buy an additional cut off
3/ to remove pack you now need to also remove the reciever wiring from the pack
4/ its easy ot check a lipo speedo or a voltage cut off is fitted.

5/ all systems can be by passed so your back to common sence.

i have purpesly run a trakpower pack till flat, on my own in an open empty space as i like to experience what i preach where possible, no explosion, no fire, the biggest problem is in fact shorting the cell, which is a hazard to any cell format.
we have to educate and trust racers to act sensibly, thay already have that trust.

typical, wrong end of country, dont get me wrong if it was aimed at me, im not moaning, im happy to use either cell format.

I think it was Neil who said it before, but you won't buy a consumer peice of equipment that was built that didn't protect you and itself from a harmful discharge.

If the system is built in, then it can be used on ANY esc without issue. If them someone is stupid enough to bypass it, then that is there problem, but for the rest of us, it is peace of mind. If you want them more widely used then they HAVE to be user friendly out of the box, not needing this and that to plug in to make them safe for use (and I mean protected from under voltage situations...)

If I was the BRCA, then that is what I would insist as a primary part of the construction rules of the cell. I mean, if we wanted them cheap, we could just keep with the foil gel sacks and a fancy sticker, but that would not puch the cells along the way of acceptance would it.

Balancing/Equalising are pretty much the same thing. Altho it may not take extra time it is still an extra piece of equipment to purchase or a feature to pay for, and you are trying to say that it will not be necessary. Whilst it may not, the likely hood is that if there is an advantage to be gained by doing it, racers will.

We don't necessarily need to equalise nimh's, but the majority do because there is an advantage to be had.

I actually have a lipo cut off in my speedo but I still think from a safety point of view it should be included in the packs themselves, not for racers but for bashers and juniors who tend to run cars out in carparks untill the batterys run flat.

if you want 'safe' (along the lines of hard case etc...) why not go the whole hog and have min-discharge and max-charge cut-off's for the pack.

if you want cheep, just go shrink wrap and solder tabs.

it would be great if manufacturers had some proposed construction rules for LiPo cells, that might help LiPO evolve and become mainstream?

I agree Chris, at the moment, they are going their merry own route, what will happen, is one will become popular and construction rules will stem from them and everyone plays catch-up.

in theory yes, but you would need some heavy elrctronics to do it as a cutr off in the pack and it will have to be able to carry the max current of the pack, as the only way it can stop the pack going flat is cut the main output cables.
this would then reguire a curent to operate which would still draw power when the cell was below 6 volt or it would not come back to life

If the tires were solid with no flex, then there would be no change in contact patch, just pressure as you said. But tires are made of flexible rubber compounds that flex and conform to the track surface, especially during weight transfer while corning, braking or accelerating. less battery weight = less contact patch and less weight to transfer (for an increase in contact patch) = less traction. Ask a tire manufacturer. You will still need just as much pressure for the same given tire for the same given traction conditions to go through a corner at the same speeds. You will end up needing softer tires, trust me, thats why everybody adds the weight back to their car with lead. Another bit of physics...by reducing the weight of the heaviest part of an r/c (the battery) that is located in the lowest part of the car, you effectivly raise the center of gravity of the car. Thats why is not just less damping and softer springs to make the cars handle right. Alot of things change when you reduce the weight of our little precision toys by 200 grams.

The minimum weights allowed for the cars haven't changed, so over the years as the batteries got heavier, the car designers designed lighter chassis to bring the cars to minimum legal weight...tires did not need to be harder because the net weight of the car and batteries were still the same.

but you are also reducing the amount of weight the tire has to 'hold' in the turn.

running the same set of tires I would favour a super light car at pulling lateral G's versus a big fat mama of a car. (even if running hard tires)

one thing I have noticed with regard to LiPo Vs Nimh...

the EB legalise the use of a 'cell' we then make them up as our own packs of batteries etc...

but it seems with LiPo, people have completely forgot about the 'cell' and are just bothered about the 'pack'

with no 'rules' or legality for the 'cell' part of a LiPo pack it could mean a big can of worms? as long as the 'pack' is LiPo and 7.4v is it 'OK'?

this seems to be a(nother) big differance between LiPo and Nimh mentality

I just through I would throw in this curve ball, I have not seen this element of 'LiPo vs Nimh' debate yet so off you go... :rolleyes: :o :p

hmmm good point chris, i supose it would be fair to say you carnt publicly buy a loose lipo cell to make a pack maybe it needs to be a pack dimension? must be only so much you can get into a box

I was thinking more along the line of, you buy IB cell's in a 'pack' via LRP (as VTEC) or Orion/Peak etc... you don't normally buy them from IB.

now I know LiPo packs SHOULD come pre-assembled but I believe it would benefit us all if they were made (by the RC company) from a certain 'type' of LiPo cell. for example a 2500mah 3.7v ***x*** size cell. they would proberbly end up in a 2s2p format inside the 'pack' in the same way that our IB cells end up in a 6s1p format.

in the same way that LRP or Orion buy in from IB and they make up their packs from this.

that way there could be a lipo battery list for the 'cell' type and homologated 'packs' are tested and proven to be made up of these cell types.

it just bring about a more 'standardized' LiPo field. I think thats why people like nimh's, we pretty much 'know' what we are getting. LiPo is so 'new' that you get some many crazy combos of batteries.

how do you mean crazy combo's?

some batteries at 4900mah, 3.7v in 2s1p
some 2500mah 3.7v in 2s2p
possible combo of 1000mah in 2s4p etc...

right now for nimh we pretty much have 6s1p and thats it, only the cell 'technology' which is only approved once a year changes to give us more capacity or voltage.

you don't see us finding some 2500 duracel AA's and using 12 cells to make a 6s2p 5000mah 7.2v pack

are they sold as car packs? got to admit only looked at the main manufacures

if you talking about the 'duracel' thing I just made that up as an example of how we 'could' make a 7.2v nimh 'pack' of cells but the 'rules' that we have (homologated cells of a certain type (subC) mean that it rules out this combo.

meant the combo of lipo

think it needs to be 2 cell in series but then a saddle pack would need to be 2x 2 cell so four cells in total

obviously 2 cells in series to get the voltage.

but the LRP pack has 2x 2500mah cells in parallel too (2s2p)

it is theoretically possible to get 10 500mah lipo cells in paralell and then 2 of those 'sets' in series do make a 2s10p 5000mah 7.4v lipo pack.

see what I mean, the combo's are almost endless.

I like the fact that nimh have a nominated cell 'size' (SubC)

nothing like this exists for LiPo. from what I understand Kokam seem to be like an IB equiv for LiPo, I am pretty sure Orion/Peak use Kokam for their cells.

is there a 'size' chart for LiPo like there is for nimh (AA, C, SubC, AAA and so on)

no idea chris about size chart.

if you want to see charts, then look at
http://www.kokam.com/english/product/battery_main.html

Kokam make the cells for the Orion packs. i have not examined the list in detail to see which cell they use, but as you can see, the range is wide. Polymer cell tooling is far more flexible than for cylinrical cells so the cost for tooling a special size is thousands of dollars rather than hundreds of thousands. I suspect Kokam use two cells or maybe four in the orion packs, depending how thick they can go with their lamination process. Jimmy and I did discuss me taking one of his packs apart for testing but we never got around to it!

I set x/y/z dimension for the cells would be a good start when talking about setting a standard.

Neil

would anyone know how (from waaaaay back in the day) we decided that using SubC size ni-cad and nimh cells was going to be the 'standard' for electric racing?

not just 'how' but maybe 'why' we choose this size too?

Cs is the industry standard for cordless powertool (23dia43 height) and powertools were to only products with cells capable of delivering high enough currents. NiCd cells started at around 1300mAh (When I started at Ever Ready in 1989 we were still making 1300mAh NiCd cells!) and then steadily progressed to 1900mAh, then to 2400mAh. NiMH for powertool started at 2.0Ah in 1997 (our company lauched the first cell with Makita in that year) and are now between 2600mAh and 4200mAh.

Cs is very versatile when making packs because its diameter is 2x its height.. this makes is tessolate very well in packs when you want to make them into cluster packs for drills, saws etc..

This is why RC cars use Cs.. because of Cordless Powertool. The RC car market is an itsy bitsy % on the end of a pin compared with powertool globally..

Personally, i think it went pear shaped around three years ago... when the Chinese started to enter the market. you see up until then, we used the best of the powertool cells (N-1900SCR, N-2400SCR) from the likes of Sanyo and Panasonic. Being japanese the performance was good and the reliability was also good. The chinese have up'd the capacity and voltage but at the expense of reliability.. the japanese are not following the chinese into this niche market because it does not play to their global goals... but it does mean that to be competititve we have to use hand built chinese cells that dont last so long..

dont get me onto batteries.. i have had enough of them now!!! :(

track power are defo two cells as they let me take one apart, orion are too as they only have one balance conector and the two main outputs