Recently realized that my solar systems daily output had increased by ~50Wh per day when in storage with no shorepower.It was hard to believe that the parasitic loads or the battery self-discharge had increased by that much as the only change I had made was to install a Meanwell 27V 500W adjustable power supply to charge up my 24V battery bank when on shorepower. I assumed that when it's unplugged from 120VAC the Meanwell would have no load on the batteries, so I hard-wired the DC output through a fuse block to the 24V battery bank.But after pulling the DC fuses in the Meanwell's output, that new 50wh per day load has disappeared. (Someday I'll have to measure its actual current draw with my clamp-on.) Do other PS/charger/converters do this? I don't recall such behaviour with the WFCO or Prog. Dyn. when boondocking, but never really looked at it closely.Anyway, it's not that big an issue as I don't need the Meanwell that much. Usually solar supplies everything we need, so I'll just leave the fuses out until it's needed. But it is unexpected.

With the DC connected, you still get power to run the fan in those converters/chargers that have temperature controlled fans. The unit can be hot enough to need the fan without actually charging anything. Also, (some of) its capacitors stay loaded (might be wrong about that)

rough guess 0.125 ampsbleed down circuit across the output of the meanwell ?why pull the fuses ? the batteries are being maintained .. correct ?expecting a string of bad weather low solar days, that you can Not recover from ?i would think that this is no different than any other charger/converter/power supply, they all have bleed down resistors of some kindwe just never notice a difference in our 12v systems, because it is already there and we don't disconnect the converter from the circuit

My RSP-500-15 has two additional fans which run whenever it remains connected to DC, so I unplug the 45 amp anderson powerpole.After unplugging both AC and then DC, the fans remain on for a second before somethng clicks and they shut off.The overvoltage protection likely consumes some juice. I'll try and remember to bust out the clampmeter and test parasitic load. when hooked to DC, not AC

I wish electrolytic capacitors were 100% efficient but they aren't.DAILY castor oil dose....125 x 24 = 3 amp hours per day.If it -really really- bugs you...

MrWizard wrote:rough guess 0.125 ampsbleed down circuit across the output of the meanwell ?why pull the fuses ? the batteries are being maintained .. correct ?expecting a string of bad weather low solar days, that you can Not recover from ?i would think that this is no different than any other charger/converter/power supply, they all have bleed down resistors of some kindwe just never notice a difference in our 12v systems, because it is already there and we don't disconnect the converter from the circuitThat makes sense, and, yes, there's no problem maintaining the batts. Guess it's not that big a deal, more of an unexpected result, and a habit trying to maintain as a low a parasitic load as possible. The comments about the fans are interesting. The fan on this one does come on at the slightest provocation, but so far I've only heard it come on under 120VAC power. But maybe I've just missed it. The clampon ammeter should help there. And maybe I should check the parasitic loads of a few other devices, like the inverter & WFCO. Thanks for all the replies.

Meanwell PS creates a load? | Good Sam Community

MEXICOWANDERER
Explorer
Jul 16, 2017

http://www.ebay.com/itm/2PCS-6-24V-50A-Toggle-Switch-On-Off-On-High-Quality-50-AMP-Trailer-Truck-RV-CAR-/141814387789?epid=1630317143&hash=item2104cbd44d:g:eAgAAOSw14xWMZIA&vxp=mtr

One to Eat Now, the other one saved for later. Good switches.

AND..........................................................

http://www.ebay.com/itm/2PCS-6-24V-50A-Toggle-Switch-On-Off-On-High-Quality-50-AMP-Trailer-Truck-RV-CAR-/141814387789?epid=1630317143&hash=item2104cbd44d:g:eAgAAOSw14xWMZIA&vxp=mtr

I like the Sure Power separator best. No voltage drop and TOTAL disconnect is, well, it's it's ------ SMART
MEXICOWANDERER
Explorer
Jul 16, 2017
Hmmm, lessee, I ran my (2) 500 amp units for an hour at 32 amperes and the cathode rose to 142F. Free standing copper has a surprising amount of thermal radiation. But yes, a heatsink would be nice. I found a junk finned isolator to be perfect for the job. I pass 100 amperes for hours with such a setup and at the end, the isolator, and the cathode are barely warm. These Schottky units are quite the item.

Brulaz, sir. Make up a bridge bypass AROUND the Schottky unit, with a fifty amp toggle switch.

REMEMBER the rule with rectifier ratings - the ratings are for full amperage conditions at an elevated temperature. A 30-volt rating will survive 30 volts continuously for years if the rectifier P/N junction temperatures are kept mild.

I tested quiescent leakage of my units at forty point zero volts. Nine milliamps at around 26c. This test does not utilize any load. Does not imply the rectifiers will survive at load with 40 volts.

There are 50 volt Schottky plates but forward voltage drop is increased and cost is higher.
Gdetrailer
Explorer III
Jul 16, 2017
MEXICOWANDERER wrote:

http://www.ebay.com/itm/500-Amp-30-V-Schottky-Rectifier-CPT50130-2-Diodes-/282361292454?hash=item41be0b66a6:m:m2LsZQ25r5ZvdtZBdvngYbg

Mount it up high in a bay. The base the cathode is energized. The anodes have 1/4" bolts which allows size perspective.

The 10 amp diodes will fail. Please don't ask why
You need absolute minimum voltage drop across the diode and this baby does it at .17 volt at 40 amps
Mounted with 1/4" couplers. Standoffs on an non-conductive cargo bay surface
The base of this is COPPER and serves as the cathode junction - meaning it has electricity.

The "base" ALSO needs mounted to a heat sink (IE chunk of copper, aluminum or even steel)!!!

Operating high current diodes without providing a way to dissipate heat from the diode junction will soon let the smoke packets out of them (and when that happens you can't put the smoke back in) :E
brulaz
Explorer
Jul 16, 2017
MEXICOWANDERER wrote:

http://www.ebay.com/itm/500-Amp-30-V-Schottky-Rectifier-CPT50130-2-Diodes-/282361292454?hash=item41be0b66a6:m:m2LsZQ25r5ZvdtZBdvngYbg

Mount it up high in a bay. The base the cathode is energized. The anodes have 1/4" bolts which allows size perspective.

The 10 amp diodes will fail. Please don't ask why
You need absolute minimum voltage drop across the diode and this baby does it at .17 volt at 40 amps
Mounted with 1/4" couplers. Standoffs on an non-conductive cargo bay surface
The base of this is COPPER and serves as the cathode junction - meaning it has electricity.

Thanks, that 500A rating is certainly better than the 3x10A rating of the ones I linked to.

But the 30V rating is too low. I equalize the batts at ~32VDC.

How about 3 of:

MBR30100CT 30A 100V Dual High-Voltage Power Schottky Rectifier TO-220

One on each of 3 leads fused at 7.5A?
Quite a bit cheaper too, although there'll be a long shipping time from the Orient.
MEXICOWANDERER
Explorer
Jul 16, 2017

http://www.ebay.com/itm/500-Amp-30-V-Schottky-Rectifier-CPT50130-2-Diodes-/282361292454?hash=item41be0b66a6:m:m2LsZQ25r5ZvdtZBdvngYbg

Mount it up high in a bay. The base the cathode is energized. The anodes have 1/4" bolts which allows size perspective.

The 10 amp diodes will fail. Please don't ask why
You need absolute minimum voltage drop across the diode and this baby does it at .17 volt at 40 amps
Mounted with 1/4" couplers. Standoffs on an non-conductive cargo bay surface
The base of this is COPPER and serves as the cathode junction - meaning it has electricity.
brulaz
Explorer
Jul 16, 2017
OK, a diode would be cheaper than the SurePower Mex mentions (which I guess is just a couple of very hefty diodes arranged to isolate two batteries), or some sort of relay.

In my case, the 16A 24V Meanwell has 3 + outputs which I've separately wired to three 7.5A fuses.

So three 10A rectifier diodes like these, one on each lead?
amazon

Not really necessary I suppose, but if it's cheap and easy enough ...
Gdetrailer
Explorer III
Jul 15, 2017
brulaz wrote:
Recently realized that my solar systems daily output had increased by ~50Wh per day when in storage with no shorepower.

It was hard to believe that the parasitic loads or the battery self-discharge had increased by that much as the only change I had made was to install a Meanwell 27V 500W adjustable power supply to charge up my 24V battery bank when on shorepower. I assumed that when it's unplugged from 120VAC the Meanwell would have no load on the batteries, so I hard-wired the DC output through a fuse block to the 24V battery bank.

But after pulling the DC fuses in the Meanwell's output, that new 50wh per day load has disappeared. (Someday I'll have to measure its actual current draw with my clamp-on.)

Do other PS/charger/converters do this? I don't recall such behaviour with the WFCO or Prog. Dyn. when boondocking, but never really looked at it closely.

Anyway, it's not that big an issue as I don't need the Meanwell that much. Usually solar supplies everything we need, so I'll just leave the fuses out until it's needed. But it is unexpected.

I would consider this to be normal for most any power supply that was never designed or intentioned to have a voltage on the output terminals when the supply is off (IE battery or solar).

To get around that issue, I use a simple diode in series with the power supplies output. This way the power supply output section never gets back fed from the other power sources.

I have used that trick to connect multiple power supplies together in parallel..

Works great when you have power supplies with an adjustable output voltage.. Add diode then adjust the output voltage up to cover the insertion voltage drop of the diode.
brulaz
Explorer
Jul 15, 2017
MrWizard wrote:
rough guess 0.125 amps

bleed down circuit across the output of the meanwell ?

why pull the fuses ? the batteries are being maintained .. correct ?

expecting a string of bad weather low solar days, that you can Not recover from ?
i would think that this is no different than any other charger/converter/power supply, they all have bleed down resistors of some kind

we just never notice a difference in our 12v systems, because it is already there and we don't disconnect the converter from the circuit

That makes sense, and, yes, there's no problem maintaining the batts. Guess it's not that big a deal, more of an unexpected result, and a habit trying to maintain as a low a parasitic load as possible.

The comments about the fans are interesting. The fan on this one does come on at the slightest provocation, but so far I've only heard it come on under 120VAC power. But maybe I've just missed it.

The clampon ammeter should help there. And maybe I should check the parasitic loads of a few other devices, like the inverter & WFCO.

Thanks for all the replies.
MEXICOWANDERER
Explorer
Jul 15, 2017
I wish electrolytic capacitors were 100% efficient but they aren't.

DAILY castor oil dose...

.125 x 24 = 3 amp hours per day.

If it -really really- bugs you...
landyacht318
Explorer
Jul 15, 2017
My RSP-500-15 has two additional fans which run whenever it remains connected to DC, so I unplug the 45 amp anderson powerpole.

After unplugging both AC and then DC, the fans remain on for a second before somethng clicks and they shut off.

The overvoltage protection likely consumes some juice. I'll try and remember to bust out the clampmeter and test parasitic load. when hooked to DC, not AC

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