Inverters

[BAH48]

So a SMPS is more efficient, I still have to return to the rated input of the charger, it's the only way to know the power consumption, that has any validity for me, being accountable for my decisions.

 

[mike killay]

Well something odd is happening in the charger.
My charger says input= 240 volts at 1.8 amps i.e. =432 watts
The output though is 42 volts at 2 amps= 84 watts.
So where does all the missing electricity go?
The charger does not get at all hot.
OR is the input at 240 volts of 1.8 amps a peak figure only and rarely achieved?

 

[trex]

a charger is a step down AC DC converter. These devices are quite efficient in converting voltage and current, that means the energy loss is usually less than 10%, for example you put in 100W , you get out more than 90W. It's like other power transformers, you have V out * I out = efficiency *Vin * I in. In this case, 42V * 1.8A = 0.9 * 230V * 0.33A at the beginning of charging,
the loss (1 - efficiency) is dissipated as heat. When you start charging, more power is connverted, more heat is lost, the charger is warm, at the end of charging, less is converted, less heat, the charger is no longer warm.

 

[oigoi]

I bought a 650w continuous rating inverter to run a 90w fridge, but it wouldn't. The inrush on an inductive motor is such a spike it takes a 1000w inverter to switch it on! Not entirely relevant to lithium battery chargers but it shows how inrush currents need to be taken into consideration when choosing an inverter.

 

[SRS]

Well something odd is happening in the charger.
My charger says input= 240 volts at 1.8 amps i.e. =432 watts
The output though is 42 volts at 2 amps= 84 watts.
So where does all the missing electricity go?
The charger does not get at all hot.
OR is the input at 240 volts of 1.8 amps a peak figure only and rarely achieved?

Mike

A switched mode power supply is very efficient. When you place one on the mains, more often than not a transformer is used to drop the voltage down, the switching electronics do the final control and regulation.

This transformer amongst other things uses electricity. This being so even if no output load is applied.

Rather like running a modern efficient engine without driving anywhere. Its still an efficient engine but sat there using fuel.

The world is full of devices sat on the mains doing nothing but wasting electricity.

In order to answer your question fully regarding actual values, one would need to measure its quiescent ( standing ) current. I'll do it on mine when I get some time.

 

[mike killay]

Thanks SRS.
I have been lent a 300 watt inverter and am presently running my battery down to try it out.
I will use a spare car battery and leave the whole lot out in the garden when I do the test!!!

 

[mike killay]

I flattened the battery of my Tonaro
(10 amp hours, 36 volt.)
I then connected it to the charger, a 300 watt inverter and an 88 amp hour 12 volt battery.
Not having any means of measuring the amperage, I fitted a 15 amp fuse in line from the battery to the inverter.
Over 6 hours, the inverter recharged the 36 volt battery without any problem, nothing smoked, nothing even got warm.
The 12 volt battery went down to what my Ring 16 amp 12 volt charger indicated was 40%.
Obviously, when camping, I either need a powerful solar panel, or to just run the van engine for a few hours.

 

[VictoryV]

Obviously, when camping, I either need a powerful solar panel, or to just run the van engine for a few hours.

Running the van will cost you about 4-5 litres in 8 hours. In "old money" 1 pint of fuel per hour on tickover.

Photo charger link
http://www.halfords.com/motoring/bulbs-wiper-blades-batteries/car-battery-chargers/solar-battery-maintainer-12v-6w

http://www.maplin.co.uk/p/solar-powered-12v-15w-battery-charger-n31cx

 

[mike killay]

Thanks Victory V.
Unfortunately, the Halfords charger will only produce half an amp in strong direct sunlight. Probably next to nothing in cloudy weather.
I usually use the van every day when camping, it has a 150 amp alternator, I don't think I will have to go very far to recover 30+ amp hours at 12 volts.