Brain fade……

[Colin Smith]

Hopefully someone with less tired and more powerful cells can help me with this?

 

I’m trying to work out the potential drain on the battery bank running a 240v AC appliance from the 12v DC/AC inverter. The appliance is rated at 180Watts. It will run for about 20 minutes in the hour. The inverter efficiency is around 88%.

 

I have a spreadsheet, calculator, pen, paper, Budweiser and am now completely confused. Any contributions would be greatly appreciated.

 

Thanks,

 

Colin

[Timleech]

Hopefully someone with less tired and more powerful cells can help me with this?

 

I’m trying to work out the potential drain on the battery bank running a 240v AC appliance from the 12v DC/AC inverter. The appliance is rated at 180Watts. It will run for about 20 minutes in the hour. The inverter efficiency is around 88%.

 

I have a spreadsheet, calculator, pen, paper, Budweiser and am now completely confused. Any contributions would be greatly appreciated.

 

Thanks,

 

Colin

 

180 x 100/88 watts consumed, /12 gives Amps, /3 gives average Amps (or Ah/h if you prefer )

 

I make that 5.68 A or Ah/h, call it 6A average.

 

Tim

[Iain_S]

180 x 100/88 watts consumed, /12 gives Amps, /3 gives average Amps (or Ah/h if you prefer )

 

I make that 5.68 A or Ah/h, call it 6A average.

 

Tim

 

Which, multiplied by 24, gives 136Ah per day. (I got the Amps figure to be 5.6666.... , but as a byproduct of 17A when running, divided by 3 and muliplied by 24)

 

Iain

[NBDensie]

Hopefully someone with less tired and more powerful cells can help me with this?

 

I’m trying to work out the potential drain on the battery bank running a 240v AC appliance from the 12v DC/AC inverter. The appliance is rated at 180Watts. It will run for about 20 minutes in the hour. The inverter efficiency is around 88%.

 

I have a spreadsheet, calculator, pen, paper, Budweiser and am now completely confused. Any contributions would be greatly appreciated.

 

Thanks,

 

Colin

 

(20/60) * (100/88) * (180/12) = 5.68 amp. So if it was running for 24 hours the drain would be 5.68*24=136 amp-hr

[Radiomariner]

Well there you are. My calculating method was different again (88% efficiency calculation at the end), and came up with the same answer as those above. (136 amp-hours per day).Things like "power factor" (AC load), and the fact that the inverter draws some power when there is no load could be considered but are pretty insignificant to the purpose of this calculation.(esp the PF)

 

Edited to add: On second thoughts, it the inverter draws say 2 amps current when without load then that would add a further 32 ampere hours per day. Which could be significant

Edited August 13, 2010 by Radiomariner

[Colin Smith]

Thank you all very much

 

Quite an overhead for 24 hour running!

 

Colin

[Radio-Ga-Ga]

Thank you all very much

 

Quite an overhead for 24 hour running!

 

Colin

 

Could be barking up the wrong tree, and 180W seems a lot for a freezer fridge/freezer that might be used on a boat, but if that's what the calculation is for, it might be more accurate to base your calculation on the makers quoted KWh/year?

[Keeping Up]

That's effectively two-and-a-half batteries-worth (if they're 110Ah batteries) per day

[Colin Smith]

Could be barking up the wrong tree, and 180W seems a lot for a freezer fridge/freezer that might be used on a boat, but if that's what the calculation is for, it might be more accurate to base your calculation on the makers quoted KWh/year?

 

I've actually been looking at a Pressure Jet central heating boiler which is a fantastic bit of kit but......it runs on 240v and is quoted at 180Watt. It's a modulating boiler and when up to temp I would estimate would be drawing power for around an average of 20 minutes in the hour. I've done some calculations based on hot-water only during the summer months with perhaps a couple of hours running in the late evening. In the winter months, it would be more likely to be on for perhaps as much as 8 hours each day and even 12 hours or so when it is sub-zero outside.

 

The unit costs are quite good and the running costs for domestic heating oil very good BUT......there is an overhead in the additional storage tankage required for domestic oil (min 550Ltrs), not a killer but looking at the power consumption when running through an inverter is scary! I could run the genny but then that is using fuel and the power drain over-night would mean more frequent charging of the batteries etc.

 

So, much as this type of boiler has loads of advantages in terms of ease of use, compact size, fuel cost etc I think I'm coming to the conclusion that it wouldn't make sense unless you were in a maina on a shore-power hook-up all winter! - which I won't be.

 

I've now looked at just about every heating option that is available. The decisions/limitations so far are:

 

1. There is space to fit a 'normal' wood burner/bubble oil stove but I don't want one. The design of the interia and layout doesn't lend itself to them and I can't be doing with messing about with the ash etc. I also have some concerns regarding the safety of 'real' woodburning stoves.

2. I've ruled out the Webasto/Mikuni,Eberspachers because....well just read the info on this forum.

3. Don't have a lot of money to spend so the initial cost is a limiting factor.

4. I would like the option of running on domestic oil but able to switch over to diesel should I struggle to find a supplier willing to deliver to the barge in future.

5. I have cupboard space available (700mm x 700mm x 1950mm) so could install the boiler in there or there is some space available under the wheelhouse but the flue could be a problem.

6. I need about 7/8Kw output

 

So I've narrowed the search down to the following:

 

1. Kabola E7 7Kw 'drip-feed' in the cupboard (with a 12v pump)

2. Glembring 8Kw 'drip-feed' fully insulated unit in the cupboard (with a 12v pump)

3. Hurricane 7.3Kw diesel boiler (with a 12v pump)

 

None of these options are inexpensive to buy and there are positives and negatives for each. Just can't make my mind up what the hell to do!!!

 

Any sensible suggestions/recommendations....anyone??

 

Cheers,

 

Colin

[WotEver]

I've actually been looking at a Pressure Jet central heating boiler which is a fantastic bit of kit but......it runs on 240v and is quoted at 180Watt.

Hi Colin,

 

I assume the 180W is the power requirement for the pump? Have you contacted the manufacurers to confirm that figure? It might be a 'worst case' amount and they might be able to give you a lower 'expected' consumption.

 

Just a thought, prior to ruling it out.

 

Tony

[Colin Smith]

Hi Colin,

 

I assume the 180W is the power requirement for the pump? Have you contacted the manufacurers to confirm that figure? It might be a 'worst case' amount and they might be able to give you a lower 'expected' consumption.

 

Just a thought, prior to ruling it out.

 

Tony

 

Hi Tony,

 

Thanks for your input.

 

I have checked and the consumption figure of 180W is for the complete setup - burner, fan and pump. I have also looked at replacing the 240v pump with a 12v pump (a few are available that draw very little power). However, the whole thing (programmer etc) is designed for a 240v pump so it wouldn't work.

 

Regards,

 

Colin

[RobinJ]

I have checked and the consumption figure of 180W is for the complete setup - burner, fan and pump. I have also looked at replacing the 240v pump with a 12v pump (a few are available that draw very little power). However, the whole thing (programmer etc) is designed for a 240v pump so it wouldn't work.

The majority of outputs on central heating stuff are relay contacts, so should be adaptable, at the wrost you may need another relay?

[WotEver]

The majority of outputs on central heating stuff are relay contacts, so should be adaptable, at the wrost you may need another relay?

I bet the first thing that happens to the incoming 240V is a drop-down to 12V for the electronics, too. But who wants to buy a 240V unit and then start modifying it in the hope that it'll all work okay?

 

Tony

[Colin Smith]

I bet the first thing that happens to the incoming 240V is a drop-down to 12V for the electronics, too. But who wants to buy a 240V unit and then start modifying it in the hope that it'll all work okay?

 

Tony

 

I guess someone more skilled in the electrical/electronic side of things could fathom it out but being new kit, there is the question of invalidating the warranty etc.....so back to the drawing board or me and more searching/evaluating until I can come up with a workable solution that isn't going to cost me £3k !!!

 

Cheers,

 

Colin

[Gibbo]

I doubt the central heating controller would know the difference between a 230 volt pump and a 12 volt pump powered from a 230 volt AC to 12 volt DC power supply.

 

That's the easiest method. It involves no mods whatsoever.

 

Or as others have said, the controller output is probably just relay contacts anyway.

 

I'll go have a gander at the specs to see if I can spot anything else.