Lipo charger questions

If i were to get a charger that can only be used with DC, I would need a power supply?

Could this power supply run at the track without ac? How does it work?


I always use ACDC chargers, and I'm thinking of getting into DC since its portable correct?

[Arct1k]

yes you would need a power supply for home...

At the track you don;t need the power supply you can get 12v from either using your car battery directly with jump leads or make up a cigarette lighter lead...

Or even lug around a 12v car battery

whats so special from having a acdc charger from a dc charger and you needing a ac power supply? I heard people using computer as a power supply, how is this done? any mods to do? If not, i'll probably go with the associated power supply.

Generally ACDC chargers are limited to 50-60W of output power. Which for a lot of batteries is fine. You get power simply by volts * amps. It is this reason why all the high powered expensive chargers are DC only. This allows you to have a much higher amp input, allowing more output power, which is required to charge high voltage, high capacity batteries.

Some people convert unused computer power supplies, there are a few guides floating around on the internet. It involves opening up the psu, messing around with some wires, cutting etc, adding terminals to the 12V lines, blah blah blah. If you don't want to mess around then just get a good PSU. For your charger, try to input as much voltage as you are allowed. If the charger can accept a 24V input then try to aim for that.

[BrianG]

The reason why AC/DC chargers are limited to ~50w is efficiency really. Those have simple linear power supplies in them that put out a set voltage (usually around 12-14v). They could use supplies that put out much higher voltage, but the charger would get VERY hot charging any lower cell counts at high current (and would need a much larger heatsink), be much heavier, and cost substantially more. And, due to size/weight/component cost, currents are limited to around 5A or less.

So, they utilize a switching power supply that converts 12v DC into whatever the charger needs to put out. For 2s, it only needs to put out ~9v. For 6s, it needs to put out ~30v. The idea is to make the internal supply voltage only as high as needed to charge the battery. This minimizes losses (heat).

But why 12v DC input? Why not simply use a switching power supply that converts 120v AC? That answer: versatility. 12v DC is a common car voltage, so this allows you to use them on a car battery. Then, for the house, you can use any type of power supply you want to get 120v to 12v DC. Including a 12vDC AND a 120vAC power supply in a charger would be expensive and wasteful.

To get 12v DC from 120v AC, switching PS units will be far cheaper/lighter than a linear PS at high currents, which is why many use computer power supplies.

Well there you go, learn something new everyday.