- Sab, 19 Ago 2006 23:05
#285368
OJO que no es oro todo lo que reluce, esas baterias tienen un uso y no son las mas idoneas para aeromodelos, pero son inmejorables para coches elctricos RC o barcos electricos de velocidad RC.
En ningun caso digo que sean malas pero son para lo que son... De hecho ya las hemos probado hace unos meses y estamos en contacto con el faricante para importarlas.
Para que quede un poco mas claro la diferencia entre las diferentes baterias que se utilizan en modelismo aqui va este pequeño articulo que escribi.
Esta en ingles pero en unos dias lo traducire al español.
We have tested A123 cells and Saphion (EMOLI) cells and others, let me explain the diferences betwen them and what is better for what.
Now it is very common to talk about Cs and make a party about them talking about manny Cs and such, but it is a non complete reference at all in order to know the power of a battery. Because it does not have relation with weight.
And weight in a helicopter or plane is a major concern.
In a RC car or Boat this is not so big concern.
Any capacitor is able to discharge over 200C even 1000C but there is no planes or helicopters flying on them, because of the weight of the pack of capacitors will make it impossible...
So the proper way to know the power of a cell/pack is to know the capacity density and the power density. And how much capacity of the nominal capacity are able to discharge under heavy load.
Capacity density makes relation of the capacity versus weight (Wh/Kg)
Power density makes relation from maximum continuous power that a cell/pack give versus weight (W/Kg)
Capacity discharged under heavy load is the percentage of nominal capacity that the cell/pack is able to deliver under heavy load. (Heavy load is considered at 80% of the full power of the cell/pack)
Here is a relation of this numbers for most kind of batteries used in RC (good quality ones)
NiCd: 44Wh/Kg 700W/Kg 85%
Nimh: 66Wh/Kg 700W/Kg 75%
Saphion (LiSph): 83Wh/Kg 900W/Kg 65%
A123: 97Wh/Kg 2400W/Kg 55%
Lipoly: 150Wh/Kg 2600W/Kg 80%
NanoLipo : 200Wh/Kg 2300W/Kg 90%
Li-Ion: 220Wh/Kg 300W/Kg 75%
OK now knowing this numbers is easy to understand and compare.
NiCd and Nimh are now quite obsolete so they will be disappearing soon.
Saphion and A123 cells are very safe and a good compromise between weight and power that is why are used in tools, they are a good option for RC cars, boats and such were weight is not a big issue. Actually A123 Cells can be rockets in RC electric cars or boats, were peak discharge is very important for accelerations, and the medium consum of the car/boat is just a little fraction of the peacks n acelerations.
Lipoly and NanoLipo are the best compromise between capacity and power for planes and helicopters and for now they have no competitor. Lipoly and NanoLipoly packs can be used as well in RC cars or boats with little weight save in relation with Saphion and A123 cells because in order to get very high current peaks the packs have to be quite big.
Li-Ion cells have very good capacity versus weight but power is very low so they are used only to feed electronic systems. (RX Systems, TX, etc…)
Here is a real example about how this affect on flight models:
Imagine a helicopter/plane with a Lipoly 4000mAh 12C pack that weights 400gr. you get form that pack 15 min. flight so the pack will be working at an average rate of 4-5C discharge, that means that you will be getting out of the pack around 85-90% of the nominal capacity and you are not torturing the pack at all so will have a quite long life.
Same helicopter/plane with a A123 cells 2000mAh 30C pack the weight will be around of 450gr.
Theoricaly you will be getting 7,5 minutes, but in this case the pack is working at a rate of 8C so you only will be able to get 75% of the pack so only 6,5 to 7 minutes, as well as you are loading more the pack so the voltage droop is higher so you will have less power available as well it weights more so you need more power to keep it in the air this means more load to the pack so finally you will end with a flight time of only around 5-6 minutes (10-11C discharge)
So with this pack “superpower 30C” pack you get: less power, less flight time, and provably less pack life because you are making it work at higher rates than with the in theory little powered 12C Lipoly pack.
Hope this helps to understand that C is only a little information about a battery and it is very important to check the weight, capacity, etc. and compare.
www.evovelo.com
