DPL8 Power Supply question

[skunkworx]

It's not a bad idea to keep it all together since the supplies are so small and light, but you could stack three together and make it a little more compact if that's the best option, then carry the 4th for small 12V chargers. I kind of wish I could do 36V since that would eliminate the 4th supply, but being on two PL-8's I have to feed each its own source. I could probably do both on one set of supplies since they're a tad underrated and I probably would never use all 80A of charge capability, but if I get a 3KW generator I probably will! (that's around 4C charging on two 5000mA 6S packs)

[Retired2011]

I'm planning on using this at home only, where I do 95% of my charging.

I have a little 610 duo in a case that I'll take to the field for an extra flight or two now and then, the supply in that setup is lacking a little so I might replace it with the extra one.

[skunkworx]

Man, that's more like fishing with a nuclear bomb instead of dynamite! Granted, I remeber the days of 50W charging and having to load up 6+ packs just to have even close to a decent day with maybe 10-12 flights. I think I had around four chargers at one point and the time it took just about drove me to quitting altogether (or at least it was a great push towards nitro )

[Retired2011]

I have more batteries than I can fly in a typical day now , if I charge them all up at once.
Sometimes on a weekday there might be only one or two guys out, and I can get a lot of flying in

[Bladecpnitro]

Hey old hippie you have the same power supplies that I have. When you run 3 or 4 how many do you have to do the floating DC ground on?
Dammit I reckon I'm just gonna need to get a 3rd one to get above the buck boost.
Its always one more thing, dammit to hell!

[RedOctobyr]

Based on the 600PB server supplies I use (I don't see why it would necessarily be different for other supplies that also require floating the ground), you float the ground on all but the first supply.

The one that you'd consider as the "12V" supply stays stock, then you float the ground on the "24V", "36V", etc.

If the supply's negative lead is coming from the positive of another supply (if it's "ground" is not 0V), it needs to be floated.

[Bladecpnitro]

Oh I missed that the OP has the Dual PL 8 which has a input max of 48V

I'm wanting a PL 8 which has a max of 32 so I can't use 3 of these supplies. Charging at home maybe my 24V setup will do fine but hey I might not always fly at home and I don't want to get bit by the buck and boost thing later on a generator.

I was looking for a way to regulate my PS down 1V so that the charger stays in buck mode but haven't really found anything. Some of the windmill generators carry high amp Diodes that might drop it like .8V and carry upto 85 Amps.

[Gregor99]

If you are running the 1200FB supplies you can turn the voltage down using a pot inside the unit. Be very careful when doing this.

http://www.rchelination.com/setting-...-power-supply/

[Bladecpnitro]

Originally Posted by Gregor99

If you are running the 1200FB supplies you can turn the voltage down using a pot inside the unit. Be very careful when doing this.

http://www.rchelination.com/setting-...-power-supply/

OK Great! I'll pop the case off and see what I can do. Looks like at the lowest setting I'll end up with is 23.4V.

Just for the sake of knowing is there a way to boost a 24 V power supply up to like 30V without harming the Power Supply or robbing it of its 75 Amp capacity.

I've searched and found all sorts of voltage boosters but stuff in the 24V Range seems to be very expensive.

[Gregor99]

Originally Posted by Bladecpnitro

Just for the sake of knowing is there a way to boost a 24 V power supply up to like 30V without harming the Power Supply or robbing it of its 75 Amp capacity.

The only practical solution is to use a supply with OVP above 14v then turn the supply up to 14v. It'd be 28v, but that should work as long as the supply's can hold the voltage under load. Not many server supplies have this capability. There are some supplies like the Meanwells and eFuel that are adjustable higher than 24v.

There are also DC-DC converters that will increase the incoming voltage to something higher or lower. A high current version will be expensive. Plus it will drop the end to end efficiency another 10%.

Regardless of method if you increase the voltage the available current will go down.

[Retired2011]

I'm still undecided on a charger, haven't bought one yet.

Here is a link with info on raising the voltage on the DPS 1200FB...
http://www.rcgroups.com/forums/showp...postcount=2238

Looks like one could get to ~27V unloaded which should keep it above transition, but I don't know how much they might drop when loaded. Hopefully one of the smart guys can help with that info...Greg?

Edit: apparently Greg was answering at the same time...I guess it's a no go.

I'm pretty sure I'm sticking with a charger that will accept 36V input.

[Gregor99]

I'm not sure about the 1200FB but the 600PB at 27v was not enough to clear the buck boost transitions. The voltage drop under load and it just shifted the transitions from the beginning of the charge cycle to the end. If the supply was very lightly loaded, that might have worked. But where's the fun in that?

Another thing to think about is that two 1200FB will put out ~1800 watts. That's about 2100 watts from the generator. Well above the average 2000 watt generator that is really more like a 1300-1600 watt generator. Drop the voltage down on each to clear the transitions and you have a lighter setup that will still max out most generators.

[Bladecpnitro]

I was able to get my DPs 1200's down to 11.88 and 11.85 V. I'm hoping that will be low enough to keep the charger in what boost mode?

That's like 23.73 V in series. A 6S lipo at 3.8V per cell will be at 22.8 at the beginning of the charger.

I could have gotten 13.03V out of each of these though providing my new Klein Multi Meter is accurate and it seems to be. That was the highest reading I got turning the dial.

[Gregor99]

That should be fine. The resting voltage will be pulled down during the charge cycle, lowering the supply voltage.

[skunkworx]

I've also noticed you get a little bit of loss on your lines coming from your supplies to the charger. Right off the back-plane you'll read say 24V, but it's down a couple 10ths of a volt by the time it gets more than a short distance away.

[Bladecpnitro]

Originally Posted by skunkworx

I've also noticed you get a little bit of loss on your lines coming from your supplies to the charger. Right off the back-plane you'll read say 24V, but it's down a couple 10ths of a volt by the time it gets more than a short distance away.

I guess the longer the wires are there the more voltage you lose then?

[RedOctobyr]

Yes. And the smaller the wire diameter, the larger the drop.

You can look up typical resistances/voltage drops per foot of wire, for different gauges. So you could get a sense of the drop.

But it will of course vary based on current flow, so a slow charge would see less drop.

Sent using Tapatalk.

[HeliSoCal]

Originally Posted by Gregor99

I would just run both channels off three supplies in series. If your generator can deliver the power, you can max both channels out on 6s with just 3 of those supplies. You'd only be pulling 57 to 60 amps from the supplies rated for 75 amps.

So you suggest using 3 supplies in series for say a Honda EU2000i running a DPL8? I'm thinking this might be my next charger and want to make sure my generator could handle it on 36v PS.

[Gregor99]

Originally Posted by HeliSoCal

So you suggest using 3 supplies in series for say a Honda EU2000i running a DPL8? I'm thinking this might be my next charger and want to make sure my generator could handle it on 36v PS.

The Honda EU2000i is a very nice generator. But it will not be able to max out the DPL. For most server supplies you won't be able to max out the power supply setup. Three DPS-600PB supplies will deliver about 1700 watts and will draw about 1950 from AC to do so. The Honda is rated at 1600 continuous. But realistically its going to closer to 1300-1400 watts.

Don't despair. Its still a great setup and will still likely be charging your packs faster than you can fly them.