rustythorn
hypothetically theoretical
another option if you plan to have continuous 120VAC in your setup is to use some premade items like this on at 35F off at 45F, however, there are various temp range options out there
48VDC Heater mats
- Thread starter Blue Devil
- Start date
So what did you come up with? I saw your post over on the Victron Community site about a relay for warming pads and came back over here to see if you had asked the same question.
I have the exact same issue. Cerbo GX, 48 volt system, 48 volt heating pads that shouldn't pull more than 6 amps (total, not individual). These are not 12 volt pads.
I would like to control the pads from the Cerbo GX, but the pads will pull too many amps for the built-in Cerbo GX relay. An external relay is necessary. I've been poking around on the Mouser.com site for relays but I don't know what the relay specs mean. I assume that I want a relay that is rated for 60 vdc. A NO (normally open) relay is preferred over NC since the pads will be on a lot less than they'll be off. Right? Otherwise, I'm lost.
My existing warming pad system is 12 volt and a 12 volt thermostat is easy to come by. To limit the complexity and number of devices in the 48 volt system, using the Cerbo GX to kick off the warming pads would be sweet.
I have the exact same issue. Cerbo GX, 48 volt system, 48 volt heating pads that shouldn't pull more than 6 amps (total, not individual). These are not 12 volt pads.
I would like to control the pads from the Cerbo GX, but the pads will pull too many amps for the built-in Cerbo GX relay. An external relay is necessary. I've been poking around on the Mouser.com site for relays but I don't know what the relay specs mean. I assume that I want a relay that is rated for 60 vdc. A NO (normally open) relay is preferred over NC since the pads will be on a lot less than they'll be off. Right? Otherwise, I'm lost.
My existing warming pad system is 12 volt and a 12 volt thermostat is easy to come by. To limit the complexity and number of devices in the 48 volt system, using the Cerbo GX to kick off the warming pads would be sweet.
If you have 120v (from the inverter) handy - what about using a 120v Inkbird temperature controller- it has 10a relays (both heat & cool).
Then you are using cheap 120v stuff and if your batteries get low the inverter shuts (everything) down - don’t have to worry about a heater draining the battery during a snowstorm in the winter.
Good Luck
Then you are using cheap 120v stuff and if your batteries get low the inverter shuts (everything) down - don’t have to worry about a heater draining the battery during a snowstorm in the winter.
Good Luck
I saw that 120 vac version. Not sure I want a solution that requires the inverter to be on.
Ron-ski
Solar Enthusiast
I fitted a 48v to 12v convertor, and then used a pair of these.
The 48v to 12v converter fed the two relays on the cerbo with 12v, that then fed back to the control side of the SSR (solid state relay), the SSR then switched 48v to my heater pads, which are actually two 24v truck mirror heater pads in series.
This worked perfectly last winter, although it doesn't get cold here really, heating only came on a few times.
It all got a bit messy, and I currently have it all ripped out as I needed the space to add two more MPPT's.
I'll revisit the heating system once I've finished my solar upgrades.
The 48v to 12v converter fed the two relays on the cerbo with 12v, that then fed back to the control side of the SSR (solid state relay), the SSR then switched 48v to my heater pads, which are actually two 24v truck mirror heater pads in series.
This worked perfectly last winter, although it doesn't get cold here really, heating only came on a few times.
It all got a bit messy, and I currently have it all ripped out as I needed the space to add two more MPPT's.
I'll revisit the heating system once I've finished my solar upgrades.
I fitted a 48v to 12v convertor, and then used a pair of these.
The 48v to 12v converter fed the two relays on the cerbo with 12v, that then fed back to the control side of the SSR (solid state relay), the SSR then switched 48v to my heater pads, which are actually two 24v truck mirror heater pads in series.
This worked perfectly last winter, although it doesn't get cold here really, heating only came on a few times.
It all got a bit messy, and I currently have it all ripped out as I needed the space to add two more MPPT's.
I'll revisit the heating system once I've finished my solar upgrades.
I was warming up to this idea, but then started poking around looking for a relay that supported 48v on both sides.
I found Phoenix Contact Product Number 2966139 at Digikey.com (in stock) with the following specs pulled from their datasheet. Mouser.com carries it also but doesn't have any in stock. This is a DIN rail mounted relay that uses screw terminal. Both are a bonus to me as I'll have a DIN rail and I prefer the screw mount. The four warming pads are rated at 52 volts, .8 amps. Would this work? I should need only one relay, right? Is this a Normally Open or Normally Closed relay? I can't find that on the spec sheet.
Last edited:
Ron-ski
Solar Enthusiast
Its both, and its on the spec sheet:
Terminals 12 & 14 are normally closed, 14 and 11 are normally open, its a change over relay.
The problem I see is it can only handle 20w at 48v and 18w at 60v, if your pads are 0.8A at 52v, then that's 41w
You can see the current it can handle for a given voltage below, ignore 1 thats for AC, 2 is the one you want.
Thank you for the circuit diagram interpretation. It was all greek to me.
So I could make this work with two relays. One relay can't handle all four pads.
So I could make this work with two relays. One relay can't handle all four pads.
Ron-ski
Solar Enthusiast
Yes, two relays would solve the problem although its still very slightly over, if two pads are 0.4 amps, then that's 20.8w at 52v. (Watts = Amps x Volts)
One relay per pad would be perfect.
One relay per pad would be perfect.
Horsefly
Solar Wizard
I haven't been following this thread recently, but I have to say I'm not sure why the solution seems to be getting complicated.
The 48V system I helped spec and install used a single 48V to 12V buck converter (https://www.amazon.com/dkplnt-Converter-Transformer-DC-DC-Non-Isolated/dp/B089FZMN5G), which powered only the 12V thermostat that many folks here use (including @HRTKD, I think?): https://www.amazon.com/LM-YN-Thermostat-Fahrenheit-Temperature/dp/B076Y5BXD9
Then I used the 48V from the system to go through the thermostat relay to power 4 12V 10W heating pads connected in series. I can't find these pads on Amazon now, but they are probably there. These pads in series pull less than 1A @ 48V, so the thermostat relay can handle it directly. I put the four pads on the sides of the two Trophy batteries. This worked great through last winter in the mountains.
The 48V system I helped spec and install used a single 48V to 12V buck converter (https://www.amazon.com/dkplnt-Converter-Transformer-DC-DC-Non-Isolated/dp/B089FZMN5G), which powered only the 12V thermostat that many folks here use (including @HRTKD, I think?): https://www.amazon.com/LM-YN-Thermostat-Fahrenheit-Temperature/dp/B076Y5BXD9
Then I used the 48V from the system to go through the thermostat relay to power 4 12V 10W heating pads connected in series. I can't find these pads on Amazon now, but they are probably there. These pads in series pull less than 1A @ 48V, so the thermostat relay can handle it directly. I put the four pads on the sides of the two Trophy batteries. This worked great through last winter in the mountains.
Yes, I'm using that same thermostat in my existing 12v battery warmer setup. That will likely be Plan B if these relays don't work out. I would like to reduce the number of interfaces and hope to use the Cerbo/Touch 50 for running and programming the warmers.
Ron-ski
Solar Enthusiast
Yes, that shows it wired for normally open.
Looks like those two relays are going to work out just fine. Fitment testing showed that my battery box has enough room for one heating pad on one side of the battery, but not a second one on the other side of the battery. UltraHeat gave me the thumbs up to use just one heating pad on the bottom of each 8s column of the battery. Instead of using four pads, I'll use two, one on each relay.
The DIN rail "holder" that the relay sits in is quite tall.
The DIN rail "holder" that the relay sits in is quite tall.
Old_Skewler
Solar Enthusiast
I am researching into this, I like the idea of (4) 12V heating pads in series connected to my 48V bus bar.
But which Temperature Controller are you using?
I can't seem to find a solution for 48V
Thanks in advance!
Horsefly
Solar Wizard
On a 48V system I put together for a friend, I used a 48V to 12V buck converter, and a 12V thermostat. The relay on the thermostat controlled 48V going to 4 12V heating pads connected in series.
Ron-ski
Solar Enthusiast
@Horsefly was the relay on the thermostat rated for 48v DC?
I'm just in the process of building a new controller relay box, it uses two solid state relays (SSR), which use 12v to switch them, and they are rated up to 60v DV switching. I then use the relays in the Cerbo to power the SSR.
I use two 24v heat pads in series, and have two batteries hence the need for only two relays.
I'm just in the process of building a new controller relay box, it uses two solid state relays (SSR), which use 12v to switch them, and they are rated up to 60v DV switching. I then use the relays in the Cerbo to power the SSR.
I use two 24v heat pads in series, and have two batteries hence the need for only two relays.
Many of these standalone thermostats have a relay that can do AC or DC, just not many amps. So 48v is probably OK, just check the specs.
Similar threads
