Power source selector switch

[BradKW]

I have both a 24v and 12v solar system...my 'fridge runs on 12/24/110v.

I want to wire it so I can select which battery bank is supplying power to the fridge, 12v or 24v (110v is wired so only powers from shore power).

I need a switch that lets me select this...I'm sure there's a simple solution, I'm just Googling down the wrong rabbit hole....

 

[blars]

Assuming a common ground, you need a single-pole double throw "SPDT" switch, rated for over the maximum current and voltage expected. For best reliability, get at DC rated switch, but most AC rated ones will last for years if they are not near maximum current. DPDT will work, needed if no common ground. Center connector to the fridge, outer ones to the batteries. Optionally you can get a center-off switch.

 

[Trebor English]

If the fridge is running on 12 volts how long does it need to be off before powering it with 24 volts? Can the voltage be changed back and forth while it is running? If the fridge needs time to switch you could use some kind of a plug in thing (Anderson maybe) where you unplug from one then plug into the other.

 

[John61CT]

Whatever you do don't buy one with "Both" "All" "1+2" or "Combine" anything like that.

Blue Sea makes quality gear, 2-postion plus an off. Don't need the huge amp one, M series should be OK.

 

[John61CT]

This is overkill, you don't need the AFP or the big amps, but it'll get you started

https://www.bluesea.com/products/11001/e-Series_Selector_3_Position_Battery_Switch_with_AFD

 

[BradKW]

Assuming a common ground, you need a single-pole double throw "SPDT" switch, rated for over the maximum current and voltage expected.  For best reliability, get at DC rated switch, but most AC rated ones will last for years if they are not near maximum current.  DPDT will work, needed if no common ground.  Center connector to the fridge, outer ones to the batteries.  Optionally you can get a center-off switch.

"[font=Arial, san-serif]A Single Pole Double Throw (SPDT) switch is a switch that only has a single input and can connect to and switch between 2 outputs. This means it has one input terminal and two output terminals. "[/font]

[font=Arial, san-serif]Would I then be using that in reverse? I'm not really sure how a switch can be directional tbh...[/font]

Manufacturer says fridge can swap input voltages on the fly, and it's fine if it's running off battery when plugged into 110v, it just selects the 110...

 

[John61CT]

Surprised the marine world doesn't seem to have an easy to find lighter-duty example.

Just get that Blue Sea, if you change down the road you can repurpose it as for charge redirection, the AFD allows even a HO alt is protected.

You can even sell it, they're simple and top notch, you and your grandkids never have to worry about it.

 

[John61CT]

If the fridge is running on 12 volts how long does it need to be off before powering it with 24 volts? Can the voltage be changed back and forth while it is running? If the fridge needs time to switch you could use some kind of a plug in thing (Anderson maybe) where you unplug from one then plug into the other.

Yes plugs will work but messy, also good ones not cheap.

"Break before Make" is the feature you're talking about.

The Blue Sea is designed that way, probably best to count to five at "Off" in the middle

 

[Weight]

Brad, switches don't care the direction of flow. OK some may, but they are rare and will be well marked. Just be sure the switch is rated for the voltage, most DC I have found are 32 or 50 volts, I'm sure there are others. The most important is the amp rating. I would use as high a amp rating I could find that fits your location, as that will have the lowest voltage drop.

 

[SternWake]

While I fully understand the desire to be able to swap the fridge to either set of batteries, I have to question whether the option is worth the effort/cost/potential pitfalls.


Did VF say there was no issue switching on the fly between 12 and 24, or Danfoss/Secop?  Are you sure they understood your question?  Was it an actual tech, or a applications/marketing 'engineer' who is trained to read the same manual you can find online which clearly states it can operate on 12 or 24 volts DC?

What I do not like is how the danfoss Electronic control unit manual  say the maximum voltage for a 12v system is 17 volts.  How is it supposed to know when it is switched from one to the other?  If there was no issue, and it could switch on the fly from 12v to 24v, then I do not think there would be this 17 volt warning.  I am no electronics guru, but this raises a red flag to me.

http://files.danfoss.com/TechnicalI...nit_101n0600_12-24vdc_08-2011_dehc100m602.pdf

I imagine there would have to be some sort of stress on the components inside the compressor controller switching like that.  If it works as intended without the magic smoke escaping on the first switching on the fly, They'd likely last the warranty period, no problem, and after that neither VF or danfoss shives a git.  I'll ask my electronics repair contact about the switching stresses on internal components but a response could be days away.

Whenever I remove power to my fridge, I  turn the thermostat dial to off, then unplug my  Anderson powerpoles, or remove the fuse.  Necessary, No, or likely not...... beneficial, I have no idea.  Warm and fuzzies? yea, they are.  When my first fridge, a Norcold failed, it rocked my world in a very bad way.  A cooler and block ice is like the 'back in high school, unprepared for a test, while being naked' type of nightmare.

How often are you likely to switch power sources?

They say the compressor controller is the most likely point of failure.  Have you seen the price of a replacement controller?

http://coastalclimatecontrol.com/in...0v-12v-24v-for-bd35-and-bd50-compressors.html

 

[Trebor English]

In addition to the voltage change don't forget the compressor starting up at zero rpm with full head pressure because it was running on the other voltage mere moments ago.  I would not recommend rapid on - off - on regardless of voltage.  

I have seen several systems that impose a fixed time delay after a power failure both one minute and three minutes.  I have owned systems without a fixed delay that cost me money to fix.  All of that at 240 volt, not 12, but rapid repowering of electric motors under load can be troublesome.

 

[BradKW]

While I fully understand the desire to be able to swap the fridge to either set of batteries, I have to question whether the option is worth the effort/cost/potential pitfalls.


Did VF say there was no issue switching on the fly between 12 and 24, or Danfoss/Secop?  Are you sure they understood your question?  Was it an actual tech, or a applications/marketing 'engineer' who is trained to read the same manual you can find online which clearly states it can operate on 12 or 24 volts DC?

What I do not like is how the danfoss Electronic control unit manual  say the maximum voltage for a 12v system is 17 volts.  How is it supposed to know when it is switched from one to the other?  If there was no issue, and it could switch on the fly from 12v to 24v, then I do not think there would be this 17 volt warning.  I am no electronics guru, but this raises a red flag to me.

http://files.danfoss.com/TechnicalI...nit_101n0600_12-24vdc_08-2011_dehc100m602.pdf

I imagine there would have to be some sort of stress on the components inside the compressor controller switching like that.  If it works as intended without the magic smoke escaping on the first switching on the fly, They'd likely last the warranty period, no problem, and after that neither VF or danfoss shives a git.  I'll ask my electronics repair contact about the switching stresses on internal components but a response could be days away.


How often are you likely to switch power sources?

Thanks, those are solid points that I need to look at more closely. It was Carl at WestyVenture that told me the unit was fine to switch on the fly to 110v shore power, that it would automatically sense the 110v and stop drawing battery. He's not a tech rep, and I did not specifically ask about swapping between 12v to 24v and vice versa.

The fridge will be running default off the 12v bank which is 200 watts solar to (2) T105s ...in general should be adequate, but it's a big fridge and I'm not going to know how my power needs balance out until doing it for a bit. The 12v bank also won't have any alternative charging source, at least not initially.

So while I don't know the frequency I'd want to swap, I don't expect it to be often...only if the 12v bank draws down to low. I think I'll go with the more expensive Blue Seas switch that has an Off setting, so I can swap between 12/24 with as long a pause as I like...maybe 5-10 min. But I want to build the option in now so I don't have to do it later if needed...

 

[John61CT]

I'll go with the more expensive Blue Seas switch that has an Off setting, so I can swap between 12/24 with as long a pause as I like...maybe 5-10 min. But I want to build the option in now so I don't have to do it later if needed...

100% agree on the switch, but no way you'd need to wait long, as long as there is actually zero current between changing, as I said, count to ten or so.

12 vs 24V auto-sensing circuitry is bog standard, as is each nominal range having its own min/max ratings, doesn't mean the device is happy across both ranges like analog without gaps, it is binary one range or the other.

 

[BradKW]

General: Both the AC and the DC power supply can be connected to the electronic unit at the same time. In this case, AC will be preferred power supply source. If the AC power supply is disconnected or drop below 85V AC on a 12V DC supply system, a time delay of 1 min. will be activated before the compressor continues on DC power supply. If AC power supply is re-established there will be no delay in compressor operation.

 

[BradKW]

 doesn't mean the device is happy across both ranges like analog without gaps, it is binary one range or the other.

Think I understand what you're saying, but would appreciate it if you could spell it out a little more...

 

[highdesertranger]

I have no backing on this but I do what stern said. I turn the switch off on my Engel before I unplug it, likewise when I plug it in I make sure the switch is in the off position. I guess it comes from a life around power tools. highdesertranger

 

[John61CT]

Think I understand what you're saying, but would appreciate it if you could spell it out a little more...

As an example, device looks at voltage, if 10<V<18 switches to 12V circuit, to switch to 24V mode, must be 20<V<30.

19V is out of range, won't work.

Solar controllers auto-detect battery bank voltage same way.

Power down, switch one to the other, restart, no problem.

 

[John61CT]

I have no backing on this but I do what stern said. I turn the switch off on my Engel before I unplug it, likewise when I plug it in I make sure the switch is in the off position. I guess it comes from a life around power tools. highdesertranger

I bet the AFD feature - designed to power down the field current on an alternator so you don't dump its load and blow the diodes - could be adapted the same way, but lot of fiddling IMO for nothing.

These switches are ignition safe for petrol fumes etc, no arcing like you get with inserting and removing plugs.

But of course if you want, just mount the switch right next to the fridge power toggle and do it that way.

 

[SternWake]

I'd have no issue switching the danfoss from AC to DC or back to AC, it's designed for that, but I would not switch from 12vDC to 24vDC while the compressor is running.


Brad, are you familiar with Anderson powerpoles?


If I were doing what you desire....
Where the proposed 12/24vDC switch would reside, I'd have one clearly marked 12vDC powerpole and one clearly marked 24vDC powerpole and have them located so the 12 and the 24 cannot be joined together.
powerpoles are rated for 10,000 mating cycles.

http://www.andersonpower.com/_global-assets/downloads/pdf/ds-pp1545.pdf

 

[John61CT]

I would not switch from 12vDC to 24vDC while the compressor is running.

Sorry if I missed where anyone proposed that, certainly not me, I think not even possible with the 3-position Blue Sea switch I thought we were talking about.