No you can not divide the power in watts by 12 (volts.) Inverters waste power in doing their conversion. The rule of thumb is to divide by 10..
I hope you have a very large battery bank. Your 800 W heater is going to draw 80 A. When you figure Peukerts Constant into the equation then that heater will flatten a 110 Ah battery in a little over half an hour.
-- Edited by PeterD on Thursday 16th of May 2013 09:26:28 AM
Scotty01 said
03:00 PM May 16, 2013
This could be a dum question but I am going to ask it anyway. I have a oil filled column heater, 800w I know watt/v = amps but if i want to know what amps this would draw from the batterys not the inverter is there a formula for this or is it say just 800w / 12v? I am sure some smart bugger will have the answer for me.
Baz421 said
04:34 PM May 16, 2013
Agree with Peter,, you will need massive battery capacity for oil filled,,, consider a small electric say 1200 or 1400W.
As a practicle example I draw down our batteries with a good load every now and then and we have a top quality pure sine wave 1000w inverter and when connected to 1000w flood lights (ie the load) it draws between 70-80 amps at 12V from the batteries.
I don't use this inverter for heating etc it is for high loads when out bush for short periods only and the loads I put on the inverter result in about 15A at12V being drawn from the batteries.
Hope this also helps and this confirms Pete's advice on the formula. I know it's hard to believe but it's true.
Scotty01 said
06:52 PM May 16, 2013
Thanks for that guys! Anyone want to buy a small column heater :)
Peter_n_Margaret said
01:57 AM May 17, 2013
Baz421 wrote:
..........,,, consider a small electric say 1200 or 1400W.
??????????
A 1200W electric heater will draw 50% more power than an 800W electric heater.
If he can't run the 800W one he certainly can't run a 1200W one.
Cheers,
Peter
Baz421 said
04:24 PM May 17, 2013
Peter_n_Margaret wrote:
Baz421 wrote:
..........,,, consider a small electric say 1200 or 1400W.
??????????
A 1200W electric heater will draw 50% more power than an 800W electric heater.
If he can't run the 800W one he certainly can't run a 1200W one.
Cheers,
Peter
you missed the point again Peter,,,,, an oil heater runs for hours to heat,,, a small electric heater runs for say 30 min and warms a small van,, therefore draw the current from 12V quickly and then turn inverted off.
As I said I don't use inverter for heating,, but if he has the batteries he can.
PeterD said
06:55 PM May 17, 2013
Baz421 wrote:you missed the point again Peter,,,,, an oil heater runs for hours to heat,,, a small electric heater runs for say 30 min and warms a small van,, therefore draw the current from 12V quickly and then turn inverted off.
The bit "..,,, consider a small electric say 1200 or 1400W" had me puzzled a bit as well.
Firstly, you did not suggest using it for a quick heat only. At any rate 1/2 an hour with a heater would not do much for heating in a van or motorhome. That time would raise the temperature a bit but then it would would decay back the norm in a short time. The cook turns our larger heater off to get me to bed (and put the light off) when she goes to bed. The heat does not last long after the heater is switched off.
Secondly, I demonstrated above that his battery would not last much over 1/2 an hour on his set up. Peukerts Constant results in a non-linear available total discharge availability as you increase the current draw. Your 1400 W heater would contribute a fair bit towards the destruction of the OPs battery if left on for 1/2 an hour. You would probably only get a bit over 1/4 of an hour before it was flat, more than that would be deleterious to the battery.
Thirdly heat is heat, is heat . . . . It does not matter which way you produce it, when you produce heat by running electricity through an element the device is 100% efficient. The difference between a column heater and a blow heater is the area over which you distribute the heat. The discharge area of a fan heater is a very much smaller area than the column heater. That is why the discharge air is much hotter than the surface area of an oil filled column. People have an illusion that the heat produced by a column heater is different from other forms but it is not. Some even think a column heater is cheaper to run, poor disillusioned fools they are.
oldtrack123 said
07:46 PM May 17, 2013
Hi Ditto to ALL of PetertD 's above post !00% correct with the battery 100% correct with both forms of heating Watts [Joules] of heat generated is the same no matter how it is produced .[simple physics] Fan heater are ok for a quick warm up Switch it 'OFF' & the area immediately starts to cool OIL heaters are slower to heat up & store the heat & then release it over a longer time AFTER being switched "OFF"
PeterQ r
Peter_n_Margaret said
12:31 AM May 18, 2013
Baz421 wrote:
you missed the point again Peter,,,,, an oil heater runs for hours to heat,,, a small electric heater runs for say 30 min and warms a small van,, therefore draw the current from 12V quickly and then turn inverted off.
As I said I don't use inverter for heating,, but if he has the batteries he can.
Sorry Baz421, but I did not miss the point at all.
As others have explained, heat is heat. If you require 2kWh of heat energy to warm the van, it will use the same energy from your battery irrespective of what type of electrical resistance heater you use.
Cheers,
Peter
Scotty01 said
02:49 AM May 18, 2013
Didnt expect this to get so involved, I dont really understand a lot of whats been said but thanks anyway. To explain a bit more I run a 1000w inverter and 2X100ah batteries. I decided to give the column heater a run last night and Only had it on for about 15mins and it turned itself off on the thermostat, it had taken the chill off the air in the van but even when it was idle it was still giving of a fair amount of heat. Cut back in after approx 10-15 mins and within an hour the interior of the van was quite warm. Volt meter was showing 12.6 when turned on and after the hour I turned it off meter was reading 12.1 and everything was still working fine. Dont think I would like to run it longer than an hour.
wasn_me said
02:53 PM May 18, 2013
Scotty01 wrote:
Didnt expect this to get so involved, I dont really understand a lot of whats been said but thanks anyway. To explain a bit more I run a 1000w inverter and 2X100ah batteries. I decided to give the column heater a run last night and Only had it on for about 15mins and it turned itself off on the thermostat, it had taken the chill off the air in the van but even when it was idle it was still giving of a fair amount of heat. Cut back in after approx 10-15 mins and within an hour the interior of the van was quite warm. Volt meter was showing 12.6 when turned on and after the hour I turned it off meter was reading 12.1 and everything was still working fine. Dont think I would like to run it longer than an hour.
Hi Scotty01
12.1 volts, you are close to your usable power, 50%, without shortening the life of the batteries. You have used almost 100 amps. You have to put more back into the batteries than you remove, to fully recharge them. (Maybe somebody can quote a figure). This means you would need a big recharging system. As you are using battery & inverter, means 240 volt isn't available, so lots of solar.
I stand to be corrected on my assumptions.
I have a 100ah battery with 130 watt solar panel. I only run lights (LED), radio, TV (2-3hrs / day), bug zapper (10 watt through inverter, when needed), 30 lt waeco in summer. My battery rarely gets below 12.5 volts.
Cheers Pete
Baz421 said
03:22 PM May 18, 2013
Yes Scotty
that was one option I was suggesting,,, get a small electric heater run for 1/2 hour = instant heat,,, takes the chill off the air but also hits the batteries,,,
Baz421 said
03:23 PM May 18, 2013
Peter_n_Margaret wrote:
Baz421 wrote:
you missed the point again Peter,,,,, an oil heater runs for hours to heat,,, a small electric heater runs for say 30 min and warms a small van,, therefore draw the current from 12V quickly and then turn inverted off.
As I said I don't use inverter for heating,, but if he has the batteries he can.
Sorry Baz421, but I did not miss the point at all.
As others have explained, heat is heat. If you require 2kWh of heat energy to warm the van, it will use the same energy from your battery irrespective of what type of electrical resistance heater you use.
Cheers,
Peter
you've still missed the point,,, I was talking about the time the heater was ON,,, not the wattage,, amps use etc etc
Peter_n_Margaret said
10:13 AM May 19, 2013
Baz421 wrote:
you've still missed the point,,, I was talking about the time the heater was ON,,, not the wattage,, amps use etc etc
Just once more.
If you produce EXACTLY the same quantity of heat using a 1200W heater as you do using an 800W heater, the higher amperage draw from the battery will result in more power loss from the battery than if you used the 800W heater.
They will deliver more power if used for light loads than they will if used with heavier loads.
That is simple battery chemistry.
Cheers,
Peter
coolabah1au said
12:08 AM May 20, 2013
Don't have and of those problem just installed a diesel heater with septerate tank put our under the bed cold air inlet on the right side of the bed Hot air left side blowing down to the kitchen ok
No you can not divide the power in watts by 12 (volts.) Inverters waste power in doing their conversion. The rule of thumb is to divide by 10..
I hope you have a very large battery bank. Your 800 W heater is going to draw 80 A. When you figure Peukerts Constant into the equation then that heater will flatten a 110 Ah battery in a little over half an hour.
-- Edited by PeterD on Thursday 16th of May 2013 09:26:28 AM
This could be a dum question but I am going to ask it anyway. I have a oil filled column heater, 800w I know watt/v = amps but if i want to know what amps this would draw from the batterys not the inverter is there a formula for this or is it say just 800w / 12v? I am sure some smart bugger will have the answer for me.
Agree with Peter,, you will need massive battery capacity for oil filled,,, consider a small electric say 1200 or 1400W.
As a practicle example I draw down our batteries with a good load every now and then and we have a top quality pure sine wave 1000w inverter and when connected to 1000w flood lights (ie the load) it draws between 70-80 amps at 12V from the batteries.
I don't use this inverter for heating etc it is for high loads when out bush for short periods only and the loads I put on the inverter result in about 15A at12V being drawn from the batteries.
Hope this also helps and this confirms Pete's advice on the formula. I know it's hard to believe but it's true.
Thanks for that guys! Anyone want to buy a small column heater :)
??????????
A 1200W electric heater will draw 50% more power than an 800W electric heater.
If he can't run the 800W one he certainly can't run a 1200W one.
Cheers,
Peter
you missed the point again Peter,,,,, an oil heater runs for hours to heat,,, a small electric heater runs for say 30 min and warms a small van,, therefore draw the current from 12V quickly and then turn inverted off.
As I said I don't use inverter for heating,, but if he has the batteries he can.
The bit "..,,, consider a small electric say 1200 or 1400W" had me puzzled a bit as well.
Firstly, you did not suggest using it for a quick heat only. At any rate 1/2 an hour with a heater would not do much for heating in a van or motorhome. That time would raise the temperature a bit but then it would would decay back the norm in a short time. The cook turns our larger heater off to get me to bed (and put the light off) when she goes to bed. The heat does not last long after the heater is switched off.
Secondly, I demonstrated above that his battery would not last much over 1/2 an hour on his set up. Peukerts Constant results in a non-linear available total discharge availability as you increase the current draw. Your 1400 W heater would contribute a fair bit towards the destruction of the OPs battery if left on for 1/2 an hour. You would probably only get a bit over 1/4 of an hour before it was flat, more than that would be deleterious to the battery.
Thirdly heat is heat, is heat . . . . It does not matter which way you produce it, when you produce heat by running electricity through an element the device is 100% efficient. The difference between a column heater and a blow heater is the area over which you distribute the heat. The discharge area of a fan heater is a very much smaller area than the column heater. That is why the discharge air is much hotter than the surface area of an oil filled column. People have an illusion that the heat produced by a column heater is different from other forms but it is not. Some even think a column heater is cheaper to run, poor disillusioned fools they are.
Hi
Ditto to ALL of PetertD 's above post
!00% correct with the battery
100% correct with both forms of heating
Watts [Joules] of heat generated is the same no matter how it is produced .[simple physics]
Fan heater are ok for a quick warm up
Switch it 'OFF' & the area immediately starts to cool
OIL heaters are slower to heat up & store the heat & then release it over a longer time AFTER being switched "OFF"
PeterQ
r
Sorry Baz421, but I did not miss the point at all.
As others have explained, heat is heat. If you require 2kWh of heat energy to warm the van, it will use the same energy from your battery irrespective of what type of electrical resistance heater you use.
Cheers,
Peter
Didnt expect this to get so involved, I dont really understand a lot of whats been said but thanks anyway. To explain a bit more I run a 1000w inverter and 2X100ah batteries. I decided to give the column heater a run last night and Only had it on for about 15mins and it turned itself off on the thermostat, it had taken the chill off the air in the van but even when it was idle it was still giving of a fair amount of heat. Cut back in after approx 10-15 mins and within an hour the interior of the van was quite warm. Volt meter was showing 12.6 when turned on and after the hour I turned it off meter was reading 12.1 and everything was still working fine. Dont think I would like to run it longer than an hour.
Hi Scotty01
12.1 volts, you are close to your usable power, 50%, without shortening the life of the batteries. You have used almost 100 amps. You have to put more back into the batteries than you remove, to fully recharge them. (Maybe somebody can quote a figure). This means you would need a big recharging system. As you are using battery & inverter, means 240 volt isn't available, so lots of solar.
I stand to be corrected on my assumptions.
I have a 100ah battery with 130 watt solar panel. I only run lights (LED), radio, TV (2-3hrs / day), bug zapper (10 watt through inverter, when needed), 30 lt waeco in summer. My battery rarely gets below 12.5 volts.
Cheers Pete
Yes Scotty
that was one option I was suggesting,,, get a small electric heater run for 1/2 hour = instant heat,,, takes the chill off the air but also hits the batteries,,,
you've still missed the point,,, I was talking about the time the heater was ON,,, not the wattage,, amps use etc etc
Just once more.
If you produce EXACTLY the same quantity of heat using a 1200W heater as you do using an 800W heater, the higher amperage draw from the battery will result in more power loss from the battery than if you used the 800W heater.
They will deliver more power if used for light loads than they will if used with heavier loads.
That is simple battery chemistry.
Cheers,
Peter
Hot air left side blowing down to the kitchen ok