converter 12v to 48v
- Thread starter jesuss
- Start date
liveforphysics
100 TW
You need a switching DC/DC power supply.
Most all DC/DC power supplies can be joined in parallel to provide as much current as you need.
Switching 800amps at 12vdc is going to be making a LOT of waste heat. Is this some sort of alternator charging system? If so, you can always get a custom wind to output the voltage you need right from the source.
Most all DC/DC power supplies can be joined in parallel to provide as much current as you need.
Switching 800amps at 12vdc is going to be making a LOT of waste heat. Is this some sort of alternator charging system? If so, you can always get a custom wind to output the voltage you need right from the source.
TylerDurden
100 GW
You will need a very, very big battery to convert 12V to run a 48V etek. You will loose a lot of power with a boost converter.
100A @48V will require 400A @ 12V assuming 100% efficiency in conversion... conversion is never 100%... in this case it might be 50% or less, if you can even find a converter that handles high currents.
Good luck.
100A @48V will require 400A @ 12V assuming 100% efficiency in conversion... conversion is never 100%... in this case it might be 50% or less, if you can even find a converter that handles high currents.
Good luck.
dogman dan
1 PW
Heh heh, dang big battery. Oops, what used to be the battery is now a puddle.
What you're looking for is a boost converter but I can promise you it is going to be VERY expensive. Also, you'll definitely need either really powerful batteries with moderate capacity or really high capacity. 48 volts at 200 amps translates to 800 amps at 12v, assuming no efficiency loss. Since your efficiency is likely going to be somewhere around 85-95%, it'd probably be closer to 1000 amps drawn from the battery. Not too many packs around here can pack that much punch. 
For normal applications, I'd definitely suggest stringing up a few batteries in series to get the voltage you need. High currents = expensive voltage converters.
For normal applications, I'd definitely suggest stringing up a few batteries in series to get the voltage you need. High currents = expensive voltage converters.
frodus
10 kW
yeah, i agree with everything, but I'll add....
Good luck finding a 200Amp 12V to 48V boost converter with regulated 48V output.
You'd spend much less getting 48V of smaller batteries to fit than you would on converting to 200A at 48V....
Good luck finding a 200Amp 12V to 48V boost converter with regulated 48V output.
You'd spend much less getting 48V of smaller batteries to fit than you would on converting to 200A at 48V....
velowatt
1 W
- Joined
- Apr 6, 2009
- Messages
- 60
There are Thundersky LiFePO4 batteries for sale around USD $1.20 per Amp.h, but they come as cells that deliver around 3.5-4V at capacities up to 160 Ah per unit (at a cost of $176!). That's a lot of watt-hours in a single cell. You may not need a balancing/BMS if using only one cell. You would need to pull that voltage up to 36-48V used in most bike motors. I imagine that losses due to inefficincy, heat and the expense of the converter circuits would negate any advantage in the size/cost of the battery.
Would it be possible to use several smaller boost converters connected in parallel to the battery (each pulling 30-50A) and connecting the outputs in serial to get the desired voltage? I suppose this would still be inefficient, but it might open up the options of batteries to use for ebiking.
I bet you could modify an old PC power supply as an inexpensive charger for such a cell?
Would it be possible to use several smaller boost converters connected in parallel to the battery (each pulling 30-50A) and connecting the outputs in serial to get the desired voltage? I suppose this would still be inefficient, but it might open up the options of batteries to use for ebiking.
I bet you could modify an old PC power supply as an inexpensive charger for such a cell?
Electricdirtbiker
100 mW
- Joined
- Mar 21, 2008
- Messages
- 49
Some other considerations besides the finding such a 12 to 48v booster, is size, cost and weight. The booster will most likely exceed all 3 compared to the motor controller for the motor. Besides heavy battery cables for 800amps you will need a spot to install the booster.
Charging will be very simple and safer voltages.
A single large 12v battery is harder to install than say a string of smaller batteries of same watt hours.
48v systems have their own complexities too, but at the end, their more energy efficent and lighter in weight.
Charging will be very simple and safer voltages.
A single large 12v battery is harder to install than say a string of smaller batteries of same watt hours.
48v systems have their own complexities too, but at the end, their more energy efficent and lighter in weight.
frodus
10 kW
basically,
much cheaper to get 4-12V batteries and go 48V to begin with.....
if you DID get a 12-48V step up, and you need 250A and 48V, thats 12,000Watts....so the 12V side of the DC-DC converter would need to supply 1000A.... very very doubtful that your 12V could even supply that much power. A 12000W converter (if it exists) will be VERY VERY costly, and so will the 1000A peak battery.
much cheaper to get 4-12V batteries and go 48V to begin with.....
if you DID get a 12-48V step up, and you need 250A and 48V, thats 12,000Watts....so the 12V side of the DC-DC converter would need to supply 1000A.... very very doubtful that your 12V could even supply that much power. A 12000W converter (if it exists) will be VERY VERY costly, and so will the 1000A peak battery.
Electricdirtbiker
100 mW
- Joined
- Mar 21, 2008
- Messages
- 49
From a functional advantage of higher voltage systems, my trail bike with an etek motor will be set up for 48v. Its geared for ~45 mph and draws 100-300amps. I'm really not a speed person and 35mph is closer to my top speed. So for more range, I may change the gear ratios (less amps) for ~35mph. There will be also less heat loss (22%) in the cables, batteries, controller and motor. And more torque and zip for hills. I'm using 8 and 6 gauge cables, small crimp lug terminals and Deans connectors.
If I was running 800-1000amps, 1-2 gauge cables, fork lift connectors and truck size terminals. I also use 10, 30amp auto fuses for the batteries. A 800-1000amp fuse will be large and expensive.
In my hobby life time, affordable batteries that can equal gasoline in energy will not happen. And at the end of each e-bike design was the problem of range. So designing a bike that is energy efficent and light weight would make the most of what battery technology we have.
Wes
If I was running 800-1000amps, 1-2 gauge cables, fork lift connectors and truck size terminals. I also use 10, 30amp auto fuses for the batteries. A 800-1000amp fuse will be large and expensive.
In my hobby life time, affordable batteries that can equal gasoline in energy will not happen. And at the end of each e-bike design was the problem of range. So designing a bike that is energy efficent and light weight would make the most of what battery technology we have.
Wes
Drunkskunk
100 GW
what you want to do is possable.
but so is moving a train by pulling it with a self propelled push mower.
possable, but not practicle. not even close.
And unless that 12v battery you have is big, and I mean Uboat storage battery big, you'll melt it fast.
Some of the small solid state DC/DC converters are 85% efficent, but the bigger, higher amperage supplies are closer to 50%, and heavy, costly heat generating monsters. you will spend far more on the conversion than you would on batteries.
but so is moving a train by pulling it with a self propelled push mower.
possable, but not practicle. not even close.
And unless that 12v battery you have is big, and I mean Uboat storage battery big, you'll melt it fast.
Some of the small solid state DC/DC converters are 85% efficent, but the bigger, higher amperage supplies are closer to 50%, and heavy, costly heat generating monsters. you will spend far more on the conversion than you would on batteries.
frodus
10 kW
jesuss said:
200A for how long? How many Ah?
icecube57
10 MW
Drunkskunk said:
You can only do that in a wet dream... My SP push mower can barely pull its self.... But good analogy I gotta remember that one... it should be nominated for ES best quotes.
