Meanwell S-350-15's in series

[Ziggurat]

Before I flip the switch...I know others have series connected meanwells, but I'm not an electrical expert so I wanted to make sure my setup is right and can work for these particular models.



They are two S-350-15 meanwells in series. One is the new modified one from epbuddy with a nice power cord and connectors. Both tuned down to 13.5 V, for a total of 27 V to the hyperion EOS 1420i power input. (By the way, ignore the extra wire in the line between them. I repurposed part of a parallel connector, the other bit isn't connected to anything.)

First, the power to the meanwells is in parallel as they are plugged into the same power bar. To my electric-newb mind, I never want to parallel and series connect the same things. But I believe I have heard this is okay for these because they are "isolated"?

Second, do I have to worry about the cases touching? I've heard that issue with people putting computer power supplies together.

Third, on the meanwell website FAQ, they have the following in an answer about series connecting their units:

...we like you to parallel a diode at the output of power supply to prevent possible damage of internal capacitors.

I don't really understand that one. Is it needed (and where exactly), or is reverse current something that just can't come up in this use case?

Much thanks for the confirmations...

 

[ZOMGVTEK]

Even if they were not isolated, it should just not work. It's not like it goes up in flames, it would just be a dead short, which most every switching supply can take momentarily before it shuts down. Most every Meanwell has isolated outputs, so you can series them all you want. Parallel gets a bit more complicated, but series is simple.

Throw them in series, and BAM, they're in series. There's not much to worry about here. I think Meanwell might mean to throw a diode on to protect from reverse voltage, which should not be an issue.

 

[mike662]

I have two S-350-48's in series to provide 82V for my lipos. Your connection looks fine. I have had the cases touching each other and nothing happened, but I too have read that it may not be a good idea for them to touch so I put a piece of foam between them when they're stacked. The diode is probably not required since you will not be hooking up anything with a higher voltage than the meanwell is designed for anyway. When I plugged my lipos into the meanwell, the led lit up and there was a reverse current from the batteries to the meanwell of 0.01A. If you put in a diode, all that will happen is the led won't light up. So I don't think you'll need the diode unless you want to be extra safe.

 

[Kingfish]

Two Meanwell's in series works for me to create a 63V assembly.

However I have had poor luck with putting two in parallel; it ends up with one doing all the work and the other just sucking down power to keep alive, but not to contribute. In my book, parallel is a bust. It is better to spec the proper or desired wattage output from a single unit, then place these devices in series to achieve the desired voltage :wink:

My ½ watt, KF

 

[ZOMGVTEK]

The cases can touch on these, there is absolutely no difference. They should actually already be electrically connected if they share a common earth ground. It would be a SLIGHTLY better idea to intentionally have the cases touch in this case.

The issue is when the supplies do NOT have isolated outputs, the DC and AC grounds generally both go to the chassis. This means if they have a ground wire hooked up, and they both share the same ground, its a dead short across the DC side. But this is not a concern for Meanwells, and its not like its really dangerous or an issue, you would know right away if it was a problem. They should just detect the short/overload and turn off without any harm done.

I like the idea of having a diode on the output, but in practice its generally not worth it, and I do not run one on my Meanwell bulk charger. Try to have the supplies on before you connect a load. It should be OK even if they are off.

 

[sico]

Two Meanwell's in series works for me to create a 63V assembly.

However I have had poor luck with putting two in parallel; it ends up with one doing all the work and the other just sucking down power to keep alive, but not to contribute. In my book, parallel is a bust. It is better to spec the proper or desired wattage output from a single unit, then place these devices in series to achieve the desired voltage :wink:

My ½ watt, KF

+1 I modded my two 27V down to 13V and seriesed them after I investigated the load sharing and wasn't happy. This was even after I'd been very careful to tune the voltages and get all the cable lengths equal and everything.

Simon.

Edit: If you do the current limit mod to about 10A (on both meanwells) or so, the parallel method should work because as soon as the charger draws more than 10 amps it will be forced to share the current load. I haven't tried it, but no reason why it won't work that I can think of.

 

[Ziggurat]

Okay, so I flipped the switch and used the two meanwells in series to charge yesterday. All went well, except ... the amps are not what I was hoping for. I was only getting about 9.2 A charging my 10S pack from 75%, or about 41*9.2 = 380 W.

I figured I should get about 13 A (550 W hyperion / 42 V pack) and set the memory slot for 12 A. In User setup I've set the power supply to 27 V and 20A. Max Lipo charge is 2C, and I have a 10 Ah pack. I've checked all settings several times.

Anyone know what power I should I be able to get from this setup? I know there are some efficiency losses, but I feel I'm not getting the full capabilities.