gregh
electronics, computers and scratchbuilding
I?ve been a bit apprehensive about using LiPo batteries, hearing some horror stories about them causing fires and reading the blurb about recharging inside fireproof containers etc. But then I realised most laptops and mobile phones use them OK. Also some of my friends have used them for years in trains (and planes).
It appears the fire problem is more acute when they are being charged or discharged at high rates. LiPos have a DIScharge rating referred to as a number of times the capacity, written as say ?20C?. This means they can be discharged at 20 times their capacity rating. So a 2200 mAh battery can supply a load of 44 amps! Model planes use this but we don?t ! You can get them up to 50C !
In trains, we only need to discharge at about 1C (1-3A) and I plan to charge at no more than C/10. Mine will be recharged in the loco.
LiPos need special chargers to ensure they don?t get overcharged and the motor controllers must also have an undervoltage device to turn them off at the min safe voltage. The electronic speed controllers I use from Hobbyking have this feature built in.
The great advantages of LiPos are the long shelf life of the charge and the larger discharge current available. The charging process is very efficient, figures of 99.8% being quoted. (compared to 70% for NiMH).
LiPo?s have a minimum voltage 3.5V/cell, and fully charged about 4.2V/cell, so I bought a 3 cell (referred to as 3S for 3 in series) rated at 2200 mAh from Hobbyking along with a suitable charger, for a grand total cost of 45 AUD delivered.
Battery Link here: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=15311 < Link To http://www.hobbyking.com/...em.asp?idProduct=15311
Charger link here:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=15042 < Link To http://www.hobbyking.com/...em.asp?idProduct=15042
The chargers are amazing little devices for the $30 price, can charge NiMH as well as LiPos with all the safety shutoff features needed for LiPos. (I used a spare 12V plug pack I had as the power source, so no cost there.) They even tell you how many mAh were put into the battery to charge it.
I replaced the ten, NiMH cells in the red Garratt, as I've realised that the greater than 1 amp currents are not good for AA cells I was using (after problems with my 4-8-0).
See this topic?.. http://www.gscalecentral.net/m50500...other 1300 mAh in the cab, I'll get 140 mins.
It appears the fire problem is more acute when they are being charged or discharged at high rates. LiPos have a DIScharge rating referred to as a number of times the capacity, written as say ?20C?. This means they can be discharged at 20 times their capacity rating. So a 2200 mAh battery can supply a load of 44 amps! Model planes use this but we don?t ! You can get them up to 50C !
In trains, we only need to discharge at about 1C (1-3A) and I plan to charge at no more than C/10. Mine will be recharged in the loco.
LiPos need special chargers to ensure they don?t get overcharged and the motor controllers must also have an undervoltage device to turn them off at the min safe voltage. The electronic speed controllers I use from Hobbyking have this feature built in.
The great advantages of LiPos are the long shelf life of the charge and the larger discharge current available. The charging process is very efficient, figures of 99.8% being quoted. (compared to 70% for NiMH).
LiPo?s have a minimum voltage 3.5V/cell, and fully charged about 4.2V/cell, so I bought a 3 cell (referred to as 3S for 3 in series) rated at 2200 mAh from Hobbyking along with a suitable charger, for a grand total cost of 45 AUD delivered.
Battery Link here: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=15311 < Link To http://www.hobbyking.com/...em.asp?idProduct=15311
Charger link here:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=15042 < Link To http://www.hobbyking.com/...em.asp?idProduct=15042
The chargers are amazing little devices for the $30 price, can charge NiMH as well as LiPos with all the safety shutoff features needed for LiPos. (I used a spare 12V plug pack I had as the power source, so no cost there.) They even tell you how many mAh were put into the battery to charge it.
I replaced the ten, NiMH cells in the red Garratt, as I've realised that the greater than 1 amp currents are not good for AA cells I was using (after problems with my 4-8-0).
See this topic?.. http://www.gscalecentral.net/m50500...other 1300 mAh in the cab, I'll get 140 mins.
