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Toggling from one bank to another?

K

kcwright

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Dec 13, 2022
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6
My first post here so be gentle.

The below is installed on a 43' sailboat but could be on an RV.
I have 4 100 watt solar panels wired in series that are connected directly to a solar generator (Bluetti AC200P) that is wired to the AC panel on our boat. We use it for Starlink, ice maker, power laptops/TV and so on. When I want to charge the house bank I flip the switch on the AC panel for the House bank/start bank charger. Obviously not the most efficient way to charge but works. I have a Victron 100 30 MPPT charge controller that came with the panels that I would like to use. The question is, can I run the solar panels into a two way switch. One side going to the charge controller and the other going to the solar generator? That way I could charge the 12V house bank till full then switch it over to the lithium (Bluetti AC200P). If this is posable what kind of switch could I use?

Thanks everyone.
 
Yes, but you need a rated disconnect for the solar placed before the switch.
Unless you can find a two position switch that is rated for the DC solar voltage and amperage. (I don't know that it would be easy to find)
 
Thanks for the response Timse.
So the idea would be to turn it off with somthing like this?

Solar Combiner Box 32A 1000V PV DC Isolator Switch with Solar Connector for Solar Power System RV, Boats, and Off/On-Grid Solar System, IP66 Waterproof : Amazon.ca: Patio, Lawn & Garden

Solar Combiner Box 32A 1000V PV DC Isolator Switch with Solar Connector for Solar Power System RV, Boats, and Off/On-Grid Solar System, IP66 Waterproof : Amazon.ca: Patio, Lawn & Garden
www.amazon.ca
then flip a switch like this to toggle back and forth?
 

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kcwright said:
Thanks for the response Timse.
So the idea would be to turn it off with somthing like this?

Solar Combiner Box 32A 1000V PV DC Isolator Switch with Solar Connector for Solar Power System RV, Boats, and Off/On-Grid Solar System, IP66 Waterproof : Amazon.ca: Patio, Lawn & Garden

Solar Combiner Box 32A 1000V PV DC Isolator Switch with Solar Connector for Solar Power System RV, Boats, and Off/On-Grid Solar System, IP66 Waterproof : Amazon.ca: Patio, Lawn & Garden
www.amazon.ca
then flip a switch like this to toggle back and forth?
Click to expand...
Yes
 
Yes.. the ARC on a DC is whats so hard to extinguish.. You might end up with an appropriate DC interrupt, and a separate DPDT.

google on below.. see how the DC rating is much smaller. google below.. you need to find a breaker with DCV and DCA ratings within your design plus 25%. someone smarter than me should chime in though..

10 Amp, 125 VDC, 240 VAC, 60 VDC, 1 Pole, DIN Rail Mount, Fixed Mount Miniature Circuit Breaker​

 
Can we back up for a second here?

How many watt hours is your house bank and how many watt hours is your combination inverter device?

If A is comparable or larger than B then all you need to do is plug a 100vac battery maintainer into your combination device and hook the DC cables onto your house bank.

Edit- I just re-read your post and it seems you don't run the inverter all the time and that's why you don't want to rely on that. Oops. Carry on :)
 
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So how I understand it the DPDT switch will be used to divert power one way or the other after the PV DC disconnect switch above has been turned to the off position. That sound right?
 
I use these......DPDT. Great for low-voltage DC switching needs.
Down position is pack#1, up position is pack#2, middle position is "off"
Very simple COPPER knife switch.
"Swing" Knife is copper
Base knife receptacle is copper.
Hinge rivets are hardened bronze or brass?
Base is solid plastic block.
Screw-down wire mounts are "enclosed clamp" style copper w/steel screws.
I have two 36V 200Ah batteries.
This a 100A version which serves as my inverter DC-side disconnect.
I use two smaller 32A versions for my panel string DC-disconnects: My panel stings VOC is only 75V though.
I've used toggle switches like those posted above in past: Contacts WILL(!) weld shut when arcs occur for 120VAC designed switches.
The below switch you simply open and close a few times to clean off copper pitting if arcs occur. PS: I"m only running max 80V.....higher voltage DC arc-faults can destroy just about any switch that is not electronically mitigated for arc-fault shutdown.
1671283244526.png
 
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featherlite said:
rated 125VAC. Does it matter that the switch is not rated for DC volts?
Click to expand...
Very much
timselectric said:
That switch is not designed to disconnect DC
Click to expand...
And neither is this:
kcwright said:
en flip a switch like this to toggle back and forth?
https://www.amazon.ca/Baomain-Unive...efix=solar+change+over+switch,aps,108&sr=8-11
Click to expand...
en flip a switch like this to toggle back and forth
?2.PNG
pullin_gs said:
use these......DPDT. Great for low-voltage DC switching needs.
Click to expand...
…and that knife switch is NOT DC rated, either; at wildhat “standard” AC>DC derating that switch is only good for ~1.5A
 
.
kcwright said:
have 4 100 watt solar panels wired in series
Click to expand...
So guessing 85-95VOC
kcwright said:
have a Victron 100 30 MPPT charge controller that came with the panels that I would like to use. The question is, can I run the solar panels into a two way switch. One side going to the charge controller and the other going to the solar generator?
Click to expand...
The blue sea switches are excellent. But they are rated at 48VDC and I’m assuming he’s well in excess of 48V
 
kcwright said:
Thanks for the response Timse.
So the idea would be to turn it off with somthing like this?

Solar Combiner Box 32A 1000V PV DC Isolator Switch with Solar Connector for Solar Power System RV, Boats, and Off/On-Grid Solar System, IP66 Waterproof : Amazon.ca: Patio, Lawn & Garden

Solar Combiner Box 32A 1000V PV DC Isolator Switch with Solar Connector for Solar Power System RV, Boats, and Off/On-Grid Solar System, IP66 Waterproof : Amazon.ca: Patio, Lawn & Garden
www.amazon.ca
then flip a switch like this to toggle back and forth?
Click to expand...
That is the same switch I use at our tiny home. They work flawlessly but in a marine environment, I'd think covering the business side might be a good idea. The one I use is the larger version because my generator and inverter use different types of ground.
 
pullin_gs said:
I use these......DPDT. Great for low-voltage DC switching needs.
Down position is pack#1, up position is pack#2, middle position is "off"
Very simple COPPER knife switch.
"Swing" Knife is copper
Base knife receptacle is copper.
Hinge rivets are hardened bronze or brass?
Base is solid plastic block.
Screw-down wire mounts are "enclosed clamp" style copper w/steel screws.
I have two 36V 200Ah batteries.
This a 100A version which serves as my inverter DC-side disconnect.
I use two smaller 32A versions for my panel string DC-disconnects: My panel stings VOC is only 75V though.
I've used toggle switches like those posted above in past: Contacts WILL(!) weld shut when arcs occur for 120VAC designed switches.
The below switch you simply open and close a few times to clean off copper pitting if arcs occur. PS: I"m only running max 80V.....higher voltage DC arc-faults can destroy just about any switch that is not electronically mitigated for arc-fault shutdown.
View attachment 125068
Click to expand...
I wouldn't use these for any serious AC loads . If they get warm the contact points separate from the knife.
And definitely wouldn't use them for DC.
 
12VoltInstalls said:
And neither is this:
en flip a switch like this to toggle back and forth
?2.PNG
Click to expand...
To be clear, we weren't talking about using it to break DC. Only as a selector, after the DC Disconnect was in the off position.
But I agree that if you were to accidentally switch it while the current was still flowing. It could make for a bad day.
 
12VoltInstalls said:
…and that knife switch is NOT DC rated, either; at wildhat “standard” AC>DC derating that switch is only good for ~1.5A
Click to expand...
Oh, I think it can handle just a tiny bit more than that. :)
I'm using it as a "hot" disconnect on 400Ah 36VDC battery bank to a 3/6KW Inverter. Batteries (two of them) are each fused at 60A. Arching iis minimal at 42V (fully charged).
IMG_0694.jpg
 
Last edited:
pullin_gs said:
using it as a "hot" disconnect on 400Ah 36VDC battery bank to a 3/6KW Inverter
Click to expand...
That’s not a good safety indicator.
Like towing an excavator on a triple axle trailer with an S10 pickup. You might get away with it for a few miles …. And then the crash happens going around a corner when the trailer goes straight and starts driving the pickup.
 
12VoltInstalls said:
That’s not a good safety indicator.
Like towing an excavator on a triple axle trailer with an S10 pickup. You might get away with it for a few miles …. And then the crash happens going around a corner when the trailer goes straight and starts driving the pickup.
Click to expand...
Why? Serious Question.....not being a smart-azz. :)
The switch is rated for 240A max 120x2...each pack gets one leg of DPDT of cutoff switch on hot side of inverter.
I fused inverter inverter-side of switch at 100A.....breakered at 60A on each (there are two) battery-side of switch.
The "open" gap is TWO(!) inches. I'm only putting 36Vdc through it.
The large mass of copper in switch contacts will absorb many joules of "arc energy" during process of switching from on to off.
Arc-flash (which is minimal to begin with at only 36Vdc non-inductive DC load) is self-quenching upon correct use of switch.
Could you please point me to a credible source that explains how this switch rated for 240V @ 240A (or 240V at 120A for only one leg) sustained can not carry 40% load (short-circuit current....sustained maximum current of circuit is only 20% of rated switch load)) of rated amps @ 36Vdc.
Thanks.
P
...
1671375605422.png

This is of interest (Source: IEEE)....please reference arc extinguish distance for DC at vmax (36V nominal Lithium Polymer) of above design.
One could successfully argue that with a very slow knife switch these distances would increase.
However this is not applicable at lower voltages (200V or as little as 80V depending on guidance source).
For 36V, the distance is mostly independent of the separation speed.
As mentioned above the mass of the switch will easily absorb arc energy (unless operator intentionally maintains arc by keeping distance between contacts below 1mm).

1671379509132.png
 
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