Trying to find a 12volt seed Germination mat.

Thread Starter

royboy

Joined Sep 25, 2016
11
I am try to find an heatpad for seed germination but because I have no power in my greenhouse I was thinking of buying a 12v heatpad but nothing was found in a search so it sounds to me that this is impossible am I correct or can it be made.
 

Tonyr1084

Joined Sep 24, 2015
4,711
Solar energy comes to mind.

I made a hot water system for my mother's sink in the back yard. We had a patio where she'd entertain friends. The sink was for rinsing out coffee cups and whatever else, but it was solely cold water. I, being the ever bright engineer, took four eight foot lengths of 3" ABS pipes and laid them on the nearly flat roof of the patio. Southern California rarely got below 32˚F so freezing wasn't a concern. With the addition of some elbows and reducers, I teed off of the cold supply to fill the pipes on the roof. The sun would heat those pipes and the water within. On the down side I piped to the sink's HOT water faucet. She loved it. Even in the evening the water was still quite warm. It was slightly less than 12 gallons, but you didn't use the hot water for showering or bathing.

Use some black pipe to form a solar heat collector then run the pipes beneath your plant bed to warm it. A small water pump and a solar panel to circulate the water will move the heat to the bed.
 

Tonyr1084

Joined Sep 24, 2015
4,711
Wait a minute - - - Aren't green houses solar by nature? Just put a used fish tank upside down over your seed bed. Place it in the sun. That'll get things warmed up. Humid too.
 

Thread Starter

royboy

Joined Sep 25, 2016
11
Wait a minute - - - Aren't green houses solar by nature? Just put a used fish tank upside down over your seed bed. Place it in the sun. That'll get things warmed up. Humid too.
Well they are but I am talking jan/Feb and we don't get much Sun at that time of the year and in lancashire
 

jpanhalt

Joined Jan 18, 2008
9,746
What differential temperature do you need to maintain? That is a pretty large mat. You could get a rough estimate of power needs. I would be worried that your battery will not last long between charges.
 

sparky 1

Joined Nov 3, 2018
261
A 12V soldering iron is a platform to model a control unit. Finding the resistance that works for you.
from a working model a control circuit can be fashioned. A control loop turns unit on and off.
The warming elements usually found on a spool by specific ohms per foot or you might find what you need in an old fridgerator.
The defrost wire. Once the correct length is determined the wire is layed out on a mat and fastened down with layer of silicon.

If you need to get er done quick then remove an automobile seat warming pad and the controller. The usb warmer might be available cheaper.
 

Thread Starter

royboy

Joined Sep 25, 2016
11
What differential temperature do you need to maintain? That is a pretty large mat. You could get a rough estimate of power needs. I would be worried that your battery will not last long between charges.
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Well the temperature wouldn't need to be high as the trays would be in touch with the mat or base so I would think 30deg at the mat and may be less than that if it was thermostatically controlled at that temp would be all I need but I don't know really and I don't know what a 12v battery would last before needing charging. I just wish I had power in the greenhouse. I will try and find out what a mains electric germination mats temperature reaches before it cuts out. Thanks for your interest.
 

jpanhalt

Joined Jan 18, 2008
9,746
How far is the greenhouse from your home? In the US, you can power a detached garage from the house. However, my barn that is 200 feet away, has its own meter. The fixed charge for that barn is about $30/month including all taxes and fees. In the Winter, when I plug in my skid steer (used for plowing snow) , that cost more than doubles. The skid steer block is kept just at freezing.

Current NEC code will have, as I recall, requirements for a detached garage. One issue is grounding.
 

LesJones

Joined Jan 8, 2017
2,667
I have never bough any type of heating element for a propagator. I started by deciding the approximate power rating I estimated would be required to warm the area I wanted. The voltage was decided by what transformers I has available , (Mostly 12 volts or 24 volts.) From that I worked out the resistance required. I then looked at what wire I had and measured its resistance per meter. (I would actually measure the resistance of several meters as the resistance of one meter would be quite low. ) Among the things I have use have been single conductor copper wire and plastic coated iron garden wire. The wire was then just wrapped round hooks at the end of the frame is a zigzag pattern to use up the calculated length. Sometimes I would wrap the length of wire round a sheet of plywood so it was more or less evenly spaced. I think you will find that you need a very large battery. I would estimate you would need at least 100 watts for the size you require. (And that is assuming you have some thermal insulation under the heating element and some kind of enclosure above the plants. (I also live in Lancashire and those estimates are from what I have used in the past.)

Les.
 

MisterBill2

Joined Jan 23, 2018
6,331
I am try to find an heatpad for seed germination but because I have no power in my greenhouse I was thinking of buying a 12v heatpad but nothing was found in a search so it sounds to me that this is impossible am I correct or can it be made.
Heating for much time using a battery is not going to work because the watt-hours in the battery will only power the heating pad for a fairly short time. Consider that a 50 watt heating pad will consume 50 watt hours of power in one hour, and at 12 volts and 20 amp-hours capacity that is 240 watt hours. That is less than 5 hours running from that battery.
So you really need to get a long enough extension cord of adequate current rating.
 

Thread Starter

royboy

Joined Sep 25, 2016
11
Yes this is interesting and thank you for your interest also it is at a reasonable cost I am not sure I will take on board as again I would have to get power to the greenhouse which I am not wanting to do. But thank you.
 

Thread Starter

royboy

Joined Sep 25, 2016
11
Heating for much time using a battery is not going to work because the watt-hours in the battery will only power the heating pad for a fairly short time. Consider that a 50 watt heating pad will consume 50 watt hours of power in one hour, and at 12 volts and 20 amp-hours capacity that is 240 watt hours. That is less than 5 hours running from that battery.
So you really need to get a long enough extension cord of adequate current rating.
I can see what you mean thank you for your interest.
 

MisterBill2

Joined Jan 23, 2018
6,331
I can see what you mean thank you for your interest.
I offer that comment to help avoid a disappointment when reality becomes too clear. Electric heating uses a lot of power and the numbers are often not as obvious as they ought to be. Recharging a battery might be more of an inconvenience than dealing with an extension cord of adequate capability for the selected heater pad, but since I am not familiar with your situation that is purely a guess.
 
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