monster
100 kW
- Joined
- Jun 17, 2007
- Messages
- 1,411
hi everyone
i have been working on building my own chargers since the only ones i can buy are so unreliable. here is what i have come up with. i have NiMH batteries but i think some of this stuff will work for lead and maybe even lithium?
the 3amp super charger my grandad made. its simply made of a BIG transformer, a variac (variable transformer) and a bridge rectifier. he had them lying around so it was really cheap apparently. the idea is that you increase the volts slowly untill the volts surpass battery voltage. the current depends on the volts drop over the battery (like a resistor). cool thing is, as the battery voltage rises the charge rate slows down so you can charge terminate by battery voltage. it works really well and is about 85% efficient but it gets hot. i filled the container with oil for heat transfer so that i could get 3amp and the oil goes up to 50*C. (40*c at 2amp.) i added a temperature cut off circuit to protect the battery, which i got from maplin for £6. im really pleased with it cos it charges the bike fast at 3amp and is efficient and battery safe. on the negative side high power mains transistors are really heavy so its not a portable option and it would be about £60+ if you had to buy all the bits yourself.
the other picture shows a trickle charger that i have made. it uses a 240 to 110v step down (UK to US) transformer. transformers are expensive but a 45watt only costs £5 so a trickle charger is cheap and charge termination will not be as critical.
i have experimented with various ways of limiting the current and the best i found is the capacitor trick suggested by fechter http://endless-sphere.com/forums/viewtopic.php?t=2495&postdays=0&postorder=asc&start=30
4.7 uF gave 0.1amp at 110v so i think about 10-30uF will give the 0.3amp i want. the capacitors dont heat up that much.
light bulbs also limit current well AKA the 3 dollar battery charger http://www.alpharubicon.com/elect/3dollarbattggn.htm
but you should definatly use a transformer with them or the charger will be very inefficient. with this 45watt trickle charger two 5watt mr11's in series should give 0.4amp. might need three of them when the battery is empty or the voltage will make them blow.
i tried to use the LM317 voltage regulator chips to regulate current and they worked but seemed to just over heat and rupture all the time so ive gone off that idea.
i also have a light weight 28v 14amp switched PSU which i'm gonna play with soon. but it keeps triggering the consumer unit atm so i may have to get another one.
i have been working on building my own chargers since the only ones i can buy are so unreliable. here is what i have come up with. i have NiMH batteries but i think some of this stuff will work for lead and maybe even lithium?
the 3amp super charger my grandad made. its simply made of a BIG transformer, a variac (variable transformer) and a bridge rectifier. he had them lying around so it was really cheap apparently. the idea is that you increase the volts slowly untill the volts surpass battery voltage. the current depends on the volts drop over the battery (like a resistor). cool thing is, as the battery voltage rises the charge rate slows down so you can charge terminate by battery voltage. it works really well and is about 85% efficient but it gets hot. i filled the container with oil for heat transfer so that i could get 3amp and the oil goes up to 50*C. (40*c at 2amp.) i added a temperature cut off circuit to protect the battery, which i got from maplin for £6. im really pleased with it cos it charges the bike fast at 3amp and is efficient and battery safe. on the negative side high power mains transistors are really heavy so its not a portable option and it would be about £60+ if you had to buy all the bits yourself.
the other picture shows a trickle charger that i have made. it uses a 240 to 110v step down (UK to US) transformer. transformers are expensive but a 45watt only costs £5 so a trickle charger is cheap and charge termination will not be as critical.
i have experimented with various ways of limiting the current and the best i found is the capacitor trick suggested by fechter http://endless-sphere.com/forums/viewtopic.php?t=2495&postdays=0&postorder=asc&start=30
4.7 uF gave 0.1amp at 110v so i think about 10-30uF will give the 0.3amp i want. the capacitors dont heat up that much.
light bulbs also limit current well AKA the 3 dollar battery charger http://www.alpharubicon.com/elect/3dollarbattggn.htm
but you should definatly use a transformer with them or the charger will be very inefficient. with this 45watt trickle charger two 5watt mr11's in series should give 0.4amp. might need three of them when the battery is empty or the voltage will make them blow.
i tried to use the LM317 voltage regulator chips to regulate current and they worked but seemed to just over heat and rupture all the time so ive gone off that idea.
i also have a light weight 28v 14amp switched PSU which i'm gonna play with soon. but it keeps triggering the consumer unit atm so i may have to get another one.
