Cells for LiFe?

August 28, 2009

Now would be a good time to offload ALL you cells and cell related equipment. Equalisers, Fans, Chargers, Pack Jigs and of course your old cells. You won’t need them again.

This time last year LiPo was not universally “legal” for UK National competition, they still aren’t fully “legal” in Europe but come November it’s a Euro to a Cent that they will be EFRA legal for electric Touring Car. So I’m guessing will cells, but no one will be using them in 2010. They will be as dead as a brushed motor.

After a lingering decline, RIP the Brushed Motors

Remember them? Brushes, skimming, all that tinkering? Slowly but surely Brushless kind of killed all that. It has taken a few years and there were a few voices that confidently predicted the brushed motor would survive in competition. They were the ones with warehouses full of brushes and brushed motors. You can still find brushed motors in use in competition if you look very hard. Provided you have got a supply of armatures and brushes and a lathe then you can still look forward to racing them into the future. Now that the manufacturers have pretty much given up on brushed, the Brushless Speedos are coming on in leaps and bounds. If your speedo has downloadable firmware then you may be able to stay ahead of the pack without having to spend too much. But with the advance of electronics, where anything is possible (with the exception of KERS it seemed prior to the German GP) the competitive life expectancy of a Brushless System is measured in months at the most. Not far off the life expectancy of a competition brushed motor, except than you can’t skim a circuit board once it has been superseded. Once it was realised that the opportunity to endlessly sell Brushless System upgrades was realised, the manufacturers all jumped onboard. Sensored motors are just the icing on the cake. It has taken maybe 3 years to kill the brushed motor.

Sudden Death of Cells!

LiPo only became competition BRCA legal in October 2008 and now, within a racing season, only a handful of drivers are using cells in competition. The most remarkable thing is the take up of LiPo by the majority of club racers in a harsh economic climate. If the weight limit rules in Touring Car were less of an issue I don’t think anyone would be using 5 cell. As it is they won’t have the choice for long. Why? Simple economics. To get a good set of cells, you need a few bad ones and a lot of average ones. Cell matching requires a large market for the average cells to fund the selection process. Typically you need to start with 2000 cells for get a few packs that will satisfy top driver’s requirements. With Joe Racer going down the Lipo route, who is going to buy the hundreds of average packs? The ready to run market will not be interested in the high capacity cells if they can get away with 2400Mah packs. They will be around for a while, but racers gave up on those capacities years ago.

So, like it or not, once the majority of racers go to LiPo if they haven’t already, there is no alternative. LiPo will completely replace Cells very quickly. They can not coexist in competition for commercial reasons. It is only a matter of time. Once EFRA sanctions LiPo for competition high capacity Cells are dead forever.

So have a look in your equipment box and start selling. Museums only have so much space!

Well, that is what I thought in July 2009, it is now early September 2009 and I’m not so sure……..

I am NOT a Lipo

That is the tag line of an advert that has been in the UK model press for a while now. It’s a LiFe, in fact a LiFePo4. That’s Lithium Iron Phosphate. It is being hailed as the new wonder battery. A little heavier than LiPo, more durable, faster charge etc.etc or so the adverts say. The headline knock off is it won’t catch fire. On paper it seems to be a much better bet that LiPo for RC vehicles.  So with LiPo not yet universally legal for Touring Car RC, how long will it be before LiFe is legal? Two, maybe three years?

Maybe not. Despite the fact that LiFe is pretty much unknown in RC, there is growing support within the ranks of EFRA to skip LiPo and propose LiFe for 2010. So what are the reasons?

Voltage LiFe is a nominal 3.3 volts per cell. This would allow a 6.6v pack. The problem with LiPo is that the nominal voltage is 3.7v per cell. Without motor wind limits the only way to impose limits is via voltage. With a 7.4v pack Touring Cars would be just too fast witthout a motor limit, and they are very hard to enforce.

Fear At a time when Nimh cells were exploding left, right and centre and causing serious injury, there was a very vocal lobby claiming that LiPo cells were nothing more than incendiary bombs. Whether this was in any way connected to the huge inventories of Mimh cells, and the significant profit potential of carefully matched cells, I won’t speculate. Suffice it to say that quality Nimh cells are not so abundant and remaining stocks of average Mimh cells have long been donated to the post race raffle. Now that LiPo is “acceptable” the fire stories are still there in the memory.

Durability LiFe cells are being promoted with warranties based on time or cycles. It is fairly easy to measure time, but I’m not sure how you can measure cycles.  These limits are measured in years and 1000 plus cycles.  After the initial sales bonanza, the incremental sales should be a bit thin. I think we can rely on the usual economic forces to ensure that we will be regularly buying a new pack that will be “the last pack you ever buy”.

So what will happen in November?

Will it be LiPo or LiFe or both? There is certainly a case to be made for LiPo based on the numbers of these cells being used today. LiFe seems to be an interesting possibility but there is very little experience. Does it actually matter to the great majority of RC racers? Not directly as EFRA rules only define rules for EFRA Euros, which is what we call modified, the least raced class in the UK. Indirectly it affects us all. Building cars for Nimh, LiPo and LiFe will be a challenge. Making rules to accommodate all types of battery will make the job of the scrutineer even more complicated. Weight limits are the easiest way forward, at least you can measure weight quickly. But how to you determine weights that equalise the performance of a 3.5T BL motor with HiMh, LiPo and LiFe cells? It is going to vary from track to track. Suddenly you need more batteries when you thought you could get by on less. I can’t see LiPo and LiFe living side by side in the rule book. I’ve also seen evidence of some distributors off loading LiPo on ebay. This might be because everyone and his dog has a LiPo brand these days. There are lots of factories in China churning them out by the container load. Or maybe they are thinking LiFe?

What might Life with LiFe be like?

With NiMh you charged at 4-6 amps. Despite recommendations, LiPos are charged at quite a bit more. I’ve seen LiFe batteries that suggest charging up to 15C. With a 4000Mah pack, that is 60 amps! OK, that means the pack will be recharged in less than 5 minutes, provided your PSU and whatever powers it can survive that long. I hear that there are already 50 amp 12v PSUs in the pipeline, That is 600 watts out so hook that up to a Honda Generator and its going to change down a couple of gears! A room full of pit tables could very quickly make the mains go bang. I was at a race this year when a 60 amp mains circuit (serving only a small part of the pits) was taking a dive with some regularity. Maybe we will soon be seeing coin in the slot meters for electricity on your pit table.

Nitro anyone?

Hello world!

August 13, 2009

These are the ramblings of bbkRob aka Rob Nelson, bird watcher, archer, gardner, cook, RC magazine contributer, race timing software developer and timekeeper.  Some or non of these activities will feature in my occasional bloggings.