Power supply to 306b

[Rotarywing]

Not being too swift to the Electrical part of this Hobby I would like to ask what is the advantage or disadvantage to wiring up 2 2z0 power supplies up to an Icharge 306b. I have it for 12v right now and charge 6s and 3s Batts. If someone explains it to me it will sink in. Thanks

[jbrandt]

Originally Posted by Rotarywing

Not being too swift to the Electrical part of this Hobby I would like to ask what is the advantage or disadvantage to wiring up 2 2z0 power supplies up to an Icharge 306b. I have it for 12v right now and charge 6s and 3s Batts. If someone explains it to me it will sink in. Thanks

Here's how I understand it:

At 12v, the 306B has roughly 500ish watts max power.

12v (~500 watts) is enough power to charge 6 3s batteries in parallel at a little over 2C, but if you want to charge multiple 6s batteries, you'll probably want the 24v supply for the full 1000 watts.

So lets say you have a 500W 12v PS. The charger can handle 500 watts, so that's 500/22.2 (6s) - 22ish amps. So even if you have a 30 amp charger like the 306B, it'll max out at 22 because that's all the power supply can give out.

Now if you have 2 12v 500w supplies for 24v, that will max out the 306B at 1000watts, and open up your charger to its full 30amp charge rate, even for 6s batteries.

I also understand that 24v runs cooler at a given amperage since it's not working as hard, but I only plan to run 12v on my 306B (if my power supplies ever get here!). I only have 3s at this point, but if I do ever expand to 6s, all I need to do is wire up another PS for 24v.

[MS60]

I've run that charger on both 12 and 24V. 24v runs better, faster charges and the charger doesn't get as hot. if you run 12v just keep charging amps down to say 6A, just check it while your charging to make sure the temp is reasonable.

[jbrandt]

Originally Posted by MS60

I've run that charger on both 12 and 24V. 24v runs better, faster charges and the charger doesn't get as hot. if you run 12v just keep charging amps down to say 6A, just check it while your charging to make sure the temp is reasonable.

Really, that low, eh?

That's no better than my 80W charger!

[RedOctobyr]

A main reason for using 24V is for getting additional output power from your charger, as jbrandt said.

Every charger has an input-current limit. Let use the FMA PowerLab PL6, since it works better than the 306B as an example.

It can output up to 40A, 1000W, into 6S. But it has an input current limit of 40A.

Let's assume you're using a single 2Z0 supply, for 12V, 47A, 575W. But the charger can only draw up to 40A. How much power does that provide to the charger?

Power = Volts * Amps
or
P = V * I

So the charger can get 12V * 40A = 480W of input power. Note that this is less than the power supply's theoretical output; the charger cannot pull all 47A from the supply.

If the charger is 90% efficient (a reasonable assumption), that gives you 432W of output power. For charging 6S (25.2V), that's 17A.

Now if you use two supplies in series, for 24V, things change. That same 40A incoming current limit means now you can get 24V * 40A = 960W from the supply. With 90% efficiency, that's 864W of output. Good for 34A into 6S.

To get a certain power output (15A into 6S, whatever), running on a higher input voltage reduces the input current to the charger. Since current flow is what generates heat in wires, etc, this helps keep wires and the charger cooler.

Merely my opinion, but I wouldn't quite agree with MS60's estimate of suggested charging amps if running on 12V.

My little 106B+ (smaller unit, smaller heatsink & fan than a 306B, and much less powerful) has spent a lot of time charging 6S at the ~9.5A it can manage when run on 12V (it can only accept 18V, and my supply is 12V). Its fan runs fast, but the charger has been fine.

I'd say set the charging amps that you want, and the charger should manage its temperature as needed. If you're uncomfortable with how warm the charger gets, then reduce the current. But I wouldn't adopt a really-low current without even trying something higher.

The 306B, in contrast to the PL6, can actually handle 50A of input current. Do be aware that this can overload a 47A power supply; you may want to configure an incoming-current limit in the charger's settings, to avoid having your supply shut itself down. Page 10 of the manual shows you can get about 500W of output power, if providing 12V. IMO, they wouldn't/shouldn't show that if they wanted you to only use, say, 150W of output power.

[Rotarywing]

Thanks guys, got it

[jbrandt]

Originally Posted by RedOctobyr

A main reason for using 24V is for getting additional output power from your charger, as jbrandt said.

Every charger has an input-current limit. Let use the FMA PowerLab PL6, since it works better than the 306B as an example.

It can output up to 40A, 1000W, into 6S. But it has an input current limit of 40A.

Let's assume you're using a single 2Z0 supply, for 12V, 47A, 575W. But the charger can only draw up to 40A. How much power does that provide to the charger?

Power = Volts * Amps
or
P = V * I

So the charger can get 12V * 40A = 480W of input power. Note that this is less than the power supply's theoretical output; the charger cannot pull all 47A from the supply.

If the charger is 90% efficient (a reasonable assumption), that gives you 432W of output power. For charging 6S (25.2V), that's 17A.

Now if you use two supplies in series, for 24V, things change. That same 40A incoming current limit means now you can get 24V * 40A = 960W from the supply. With 90% efficiency, that's 864W of output. Good for 34A into 6S.

To get a certain power output (15A into 6S, whatever), running on a higher input voltage reduces the input current to the charger. Since current flow is what generates heat in wires, etc, this helps keep wires and the charger cooler.

Merely my opinion, but I wouldn't quite agree with MS60's estimate of suggested charging amps if running on 12V.

My little 106B+ (smaller unit, smaller heatsink & fan than a 306B, and much less powerful) has spent a lot of time charging 6S at the ~9.5A it can manage when run on 12V (it can only accept 18V, and my supply is 12V). Its fan runs fast, but the charger has been fine.

I'd say set the charging amps that you want, and the charger should manage its temperature as needed. If you're uncomfortable with how warm the charger gets, then reduce the current. But I wouldn't adopt a really-low current without even trying something higher.

The 306B, in contrast to the PL6, can actually handle 50A of input current. Do be aware that this can overload a 47A power supply; you may want to configure an incoming-current limit in the charger's settings, to avoid having your supply shut itself down. Page 10 of the manual shows you can get about 500W of output power, if providing 12V. IMO, they wouldn't/shouldn't show that if they wanted you to only use, say, 150W of output power.

This was my thought.

These chargers have internal temp controls that will reduce the output or shut it off entirely if it gets too hot.

So far, when charging 3 or 4 3s batteries in parallel at 6amps, the fan on my 306B doesn't even turn on when running 12v. I haven't tried higher amps yet, but if the fan isn't even turning on at 6 amps, I'm not too worried.

[Rotarywing]

I forgot one more question I'm using a 12v fan out of an old computer for inside my charging case and have it wired directly to the power supp. outputs, if I go with 24v can I use this same fan? I'm not sure what to do. It's an 80mm.

[RedOctobyr]

The two easy options:

- Tap into the outputs from the first supply (you can add another set of outputs if needed). The one whose negative/black wire goes to the negative/black of the charger's input. That supply is providing 12V. Use the output from that supply to give 12V to the fan.

- Buy a second, identical 12V fan. Wire the two fans in series (red wire of fan A to black wire of fan B), and connect them to the 24V output. Each fan will actually have a 12V drop across it. This adds noise and cost, but you'd also get more airflow, if you don't want to grab 12V from the first supply.

Or, if buying a fan, look for a single 24V fan in the size you need.

[Rotarywing]

Thanks alot RedO great help.