just so you know at guildford andy kane ran kan opener on A123 batteries and my god there was a massive difference in performance. maybee you would be able to start adding them to your vapourbots. you will have more power and save weight. dont know too much in detail about them but maybee Leo does. there is a thread somewhere dedicated to A123 testing too.
awesome Swan, reading this Im sure its worth for us vapourboteers to put some research in these batteries
and I think its even lovelier how you decided to involve our little section in this, highly supportive
Sure.
A123 systems built a cell based on a chemical compound called Lithium Ion Nano Phosphate (LiFePo4). These cells (I have used them in my real robots and in my vapours already) have certain major advantages over the Nicad and NiMh packs. Since A123 systems were the first to use these cells we have called them A123 cells even though there are other manufacturers out there.
For starters, a Nimh cell is between 60 and 70 grams. So is a A123. A nicad cell is about 85 grams. So where is the advantage? Well a single nimh or nicad cell is 1.2V to 1.4V, so you need 30 to make 36V. A single A123 cell is 3.3V to 3.6V and only needs 10 to make 33-36V. That is the difference between 2.1kg per pack or 700 grams per pack. That is a significant weight loss.
I run Hannibalito 3, my real life feather on 4 cells, so 350 grams of battery.
This does come at a price though, you need to keep the temperature of the cells down, otherwise they degrade very rapidly. That means you shouldnt try to run 2 lem 130s on a single pack, or 2, or 3. As a rule of thumb, the maximum output of these packs is 70A. So if you have a motor thats consumes 300A, divide that number by 70 and you will know how many packs you need in parralel.
In comparison, Nicads over 3000mAh are capable just shy of 100A, nimh 50A maximum. so that makes the division as such:
2 brand X motors draw 500A max at 36V. to power them its would require:
A123 500/70= 7.15 packs rounded off 8 packs.
Nicad 500/100=5 packs
Nimh 500/60=8.33 rounded off 9 packs
In weight that would be:
A123: 8* 700g= 5.6kg
Nicad: 5* 2.55kg = 12.7kg
NiMh: 9 * 1.95kg = 17.55kg
So even though you would need more packs than with NiCads, the packs themselves are much lighter therefore still saving weight. The packs are much smaller too so they are easier to fit. mind you these numbers are a guideline so dont treat them as gospel, in fact they are even on the light side. However this is what i would consider the bare minimum for battery usage.
Added bonus although for vapours not really applicable, you can charge them really fast. as long as the packs are balanced it is no problem shoving a 10A charge per cell in there. Another bonus is that as opposed to LiPo or NiCad there is no danger of fire.
That ok Shane?
(Message edited by leorcc on June 24, 200
i think that just about covers it leo, even i have learnt a bit today.
Yeah, Ive already begun using them in my last few vapourbots. I think this is the way forward for both vapourbots and real robots. Out of interest, would it be worth having a cooling fan next to the cells to keep the temperature down? I think we have all seen the
quote:
Out of interest, would it be worth having a cooling fan next to the cells to keep the temperature down?
Not really. the cardboard like material the housing is made of is not very good at thermal tranfering so any cold air blowing next to it will hardly pick up any heat from the cells. For the little cooling you might get by adding a fan you are almost better off just adding another pack. Making sure the cells do not exceed 65 degrees in the first place is the better option imho.
Do not confuse Lipo with LiFe or A123, those are really 2 different types of batteries and not allowed in anything larger than feathers.
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There€™s also probably some stuff somewhere on the Robowars Forum, as I believe the Aussie feathers are starting to run on them. What you mean starting? A lot of us have been running them 12+ months
Why did I even bother posting...
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