Running a propagator off a car battery??

[Protea]

I have an electric propagator that i want to use in my greenhouse but we don't have any electricity outside and as we rent the husband isn't keen on drilling through the wall to run a cable through! I was wondering if i could rig it up to a car battery or something (and get a charger for the battery), i have no electrical expertise and neither does Mr Protea but he has electrician friends at work. Is this possible and how would i do it? The propagator runs on probably 12-50 watts, i'd have to check but most props are around this.

Or....does anyone have any other suggestions of how to provide heat?
i want to try some show onions - buying seeedlings rather than seeds - it says in the catalogue that they are delivered in February and require min 50 deg F heat plus bottom heat. I have a paraffin heater but could do with a bit more to raise the temp plus add bottom heat with the prop.

[nick the grief]

Hi Protea,

It wouldn't be worth the hassle I don't think as most propagators are 240 v so you'd have to have an invertor & then you incure losses. You can use your parafin heater quite easily, thats what I did when I frst started & it wasn't a big one it was a coldframe heater type.



What I had was a steel shelf turned upside down with a wooden frame to make a "raised bed" type of thing. put a layer of damp sand in the bottom this will spread the heat more effectivly (but make sure it doesn't dry out) and then you adjust the distance from the chimney to the bottom of the metal sheet to regulat the temperature.

If you use some timber that is about 5" thick I put 2" of sand that gives you a bit of head room to make a cover over the seed trays if you want or you can use individual seed tray covers & dont make the box so deep (about 3")

It will also help keep your greenhouse warmer with the "waste heat" from the parafin lamp.

[Protea]

Thanks Nick!

I was hoping you'd see my post! I have slatted wooden staging - does the shelf have to be metal? I have some large plastic gravel trays that would be the right size but would they melt? (how hot is it going to get?).....or where can i get this metal shelving stuff?

I could put the heater under the staging - thats not a problem, but when it gets really cold it really only keeps the greenhouse above freezing, according to the instructions it needs to be about 10 deg C, maybe i need an additional heater? (Mr Protea won't be happy )

[nick the grief]

No plastic's no good.

1. It would melt
2. Plastic is an insulator & what you need is a conductor of heat

It doesnt need to be a shelf it just so happened I had one I could use at the time. A sheet of steel or Aluminium would be OK & just scre the wooden edging to it. If you can remove some of the slats it would be better just in case they get too hot.

As to size, well the one I used was smaller than the top picture here So I would guess it will still be OK

http://www.base-camp.co.uk/Wick%20st...%20heaters.htm

[Protea]

Ok - thanks, i'll have a look at the buliders merchants/DIY shop for some metal sheeting.

The heater i have is the same as the top one in your link, but my greenhouse is only 6'x6'. i'll show this to hubby tonight - hopefully he'll be up to the job of building something for me

Many thanks

[Snadger]

Hi Protea,

It wouldn't be worth the hassle I don't think as most propagators are 240 v so you'd have to have an invertor & then you incure losses. You can use your parafin heater quite easily, thats what I did when I frst started & it wasn't a big one it was a coldframe heater type.

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What I had was a steel shelf turned upside down with a wooden frame to make a "raised bed" type of thing. put a layer of damp sand in the bottom this will spread the heat more effectivly (but make sure it doesn't dry out) and then you adjust the distance from the chimney to the bottom of the metal sheet to regulat the temperature.

If you use some timber that is about 5" thick I put 2" of sand that gives you a bit of head room to make a cover over the seed trays if you want or you can use individual seed tray covers & dont make the box so deep (about 3")

It will also help keep your greenhouse warmer with the "waste heat" from the parafin lamp.

Hi Nick
Funnily enough...... I was toying with a similar set up after seeing a bench top version advertised in the Kays catalogue (I think? )

The idea of the sand is to turn localised heat into blanket heat and I would imagine it would have to be damp to do that.

I know this may sound complicated, but I can visualise a very thin tank made of thin copper sheet (a flattened out old hot water boiler, cut to size and easily soldered, perhaps) and filled with water. A boss soldered on to one corner to vent it and allow for expansion. Tank could be only 1" X 2'6" X whatever length required. Tank filled with water and used as propagating bench bottom with paraffin heater under.

Plan B would be as you describe, but with micro-bore copper water pipe embedded in to sand in a similar way to a a soil warming cable, ie backwards and forwards across width. Once again would need to be vented to allow for expansion when filled with water

[nick the grief]

Yep thats it Snadger.

Sand it's self isn't particularly good at transfering heat but the water in the sand is and as it never gets to boiling point it should be OK for a week or so, you can always cut a black bin liner up & cover the sand over to keep the moisture in any way - thats what I do with my prop bench.

You'll still have a "hotspot" directly above the heater but it won't be as fierce and it's quite advantageous to have "cooler" spots anyway as you can move cuttings/seeds away from the heat to help harden them off.

Your idea for a "boiler & pipes" is OK but a little OTT for the end result as you can't really regulate the temperature as such & would be relying on a gravity feed, Much simpler to use the sheet of metal & the sand .

I know the one you mean in the kays catalogue, that uses an "asbestos" type pad I think to spread the heat but work the same. I used the described system for 3 or 4 years till I got the new greenhouse & had electric in it and I still think I got better growth with the old system I always thought it may be to do with the CO2 given off by the parafin heater that promoted growth in the cuttings - it may be that I just haven't got the hang of the "new" set-up yet

[nick the grief]

Ok - thanks, i'll have a look at the buliders merchants/DIY shop for some metal sheeting.

The heater i have is the same as the top one in your link, but my greenhouse is only 6'x6'. i'll show this to hubby tonight - hopefully he'll be up to the job of building something for me

Many thanks

That should be OK for a 6x6 greenhouse Protea unless we get to -20 then it may struggle I used one like that to keep my 12x8 frost free the first winter just make sure there are as few draughts as possible ( although a few small gaps will be ok to vent the greenhouse)

As to metal sheeting, try the tip & see if there's an old cooker up there as you could take the door off & use that