vehicle charging

[stevieb]

i have recently been looking into the possibility of charging my bike battery whilst on the move in my van.
after some helpfull advice from this site i have worked out that for my 240v 1.8 A charger input the power required is just under 500watts.
so no problem then , just get a 600watt inverter from maplin.
but apparently NO
i have been advised that to charge at this level i need an inverter of nearly double that because inverters don,t give out power in the same way as the ac mains.
the chap who explained this tried his best to explain the reason for this to me but ran out of time
i also believe that devices like laptop chargers as well as bike chargers have other issues when it comes to using an inverter.
can anyone help out here because i want to take my bike on holiday but may not always have access to ac mains.
i should add that i have a large capacity battery in my van and would only be charging whilst the engine is running.
thanks in advance

 

[trex]

the 12V car adapter charger only needs 100W input from your battery. Your cigarette lighter socket is good enough.

 

[smee]

He may have been referring to power factor problems. If I remember the theory (it's been a while), basically, it comes down to the difference between Watts and VA. For an AC circuit, just multiplying Volts by Amps gives you VA but that isn't the whole story. If the load is reactive, the current and voltage can be out of phase, so the effective power transferred is less. This difference is described usually in terms of a power factor.

Let's say the charger has a poor power factor of 0.5 (a good power factor would be 1). So, it requires 1.8x240 which is 432 VA , but if the power factor is 0.5, then you need double that from the inverter - i.e. 864 watts.

btw. It's the same when using the mains to power it, just that the mains has no trouble giving the extra power you need.

 

[Alan Quay]

Trex is right. Your charger is not 240v x 1.8a, it's 42v at 1.8a, giving 76w.

 

[smee]

Trex is right. Your charger is not 240v x 1.8a, it's 42v at 1.8a, giving 76w.

I thought he was talking about using an inverter to generate 240V from his 12V car battery, then powering anormal 240Vac bike battery charger from that.

 

[trex]

even an inverter like this one is good enough:

http://www.ebay.co.uk/itm/like/350766047505

 

[Alan Quay]

I thought he was talking about using an inverter to generate 240V from his 12V car battery, then powering anormal 240Vac bike battery charger from that.

Yes, but all the maths has been based on 240 x 1.8a, which is probably not the case.

The charger will most likely put OUT 1.8a at 42v, giving 76w, so allowing for some losses, you could call it 100w.

 

[stevieb]

thanks for the qiuck replies guys
smee is giving an answer similar to the guy that origonally tried to explain this to me and baffled me with science, also correct that i want to use my existing 240v charger with an inverter
he also refered to the fact that i needed to double the size of the inverter..
also said to be carefull charging some electronic devices with an inverter , which i still don,t understsand.
buying a larger inverter isn,t a problem and i,m happy to just accept this even if i can,t understand the science behind it.
i will take the word of those more knowledgable than myself.
what i don,t want to do is cause any damage to my charger or battery by using an invertor.
thanks

 

[peerjay56]

thanks for the qiuck replies guys
smee is giving an answer similar to the guy that origonally tried to explain this to me and baffled me with science,
he also refered to the fact that i needed to double the size of the inverter..
also said to be carefull charging some electronic devices with an inverter , which i still don,t understsand.
buying a larger inverter isn,t a problem and i,m happy to just accept this even if i can,t understand the science behind it.
i will take the word of those more knowledgable than myself.
what i don,t want to do is cause any damage to my charger or battery by using an invertor.
thanks

Like you I'm no electrician, but I do know that some inverters produce 'dirtier' power than others - lots of spikes in the voltage and power produced. I think you need to ensure that you get a pure sine wave inverter, rather than a square wave one. Also more expensive - if it's a cheap inverter, it's almost certainly not pure sine wave

 

[smee]

thanks for the qiuck replies guys
smee is giving an answer similar to the guy that origonally tried to explain this to me and baffled me with science, also correct that i want to use my existing 240v charger with an inverter
he also refered to the fact that i needed to double the size of the inverter..
also said to be carefull charging some electronic devices with an inverter , which i still don,t understsand.
buying a larger inverter isn,t a problem and i,m happy to just accept this even if i can,t understand the science behind it.
i will take the word of those more knowledgable than myself.
what i don,t want to do is cause any damage to my charger or battery by using an invertor.
thanks

Steve, can you check that your charger really does draw 1.8 amps from the 240v mains power. Others here seem to think that is too much, and that you are reading the low voltage output current. This may be true, for example, my bike charger is only 140 Watts - not the 400 odd that yours would be with the figures you quoted. Look for input Watts or VA rating if the current isn't given on the 240V input side.

What peerjay said about inverters producing "dirty" power is true. However, and my experience was just running a laptop, but it seemed OK on my cheap inverter. It would depend on the charger or power supply's design, and how much filtering/noise tolerance it has.

 

[Deleted member 4366]

Don't waste your time with all that stuff. Get a generator.
http://www.ebay.co.uk/itm/Portable-Super-Silent-Suitcase-Petrol-Generator-0-7KVA/400601921036?_trksid=p2045573.c100033.m2042&_trkparms=aid=111001&algo=REC.SEED&ao=1&asc=20131017132637&meid=6982320937949955067&pid=100033&prg=20131017132637&rk=4&rkt=4&sd=181410688586

 

[stevieb]

the reference to dirty power is also what my college mentioned and this sounds reasonable.
here is what the spec on my charger says
input ; ac 100v-240v~, 1.8A (max) 47-63Hz
output:dc42. ov-2.0A
hope this helps
the generator route is one i did consider and thanks for the link but the idea is to charge stuff whilst on the move and a generator wouldn,t fit the bill
i also checked the small print on the generator link and it is not suitable for sensitive equiptment.
, but thanks for the info anyway

 

[smee]

I'm guessing that the (MAX) after the 1.8A, means that is the current drawn from the lowest voltage - i.e.100v - So it's about 180 watts, and since my 36 volt charger is 140 watts, err, VA, that looks to be in the ballpark. btw. that means you will only need a smaller inverter.

 

[smee]

Don't waste your time with all that stuff. Get a generator.
http://www.ebay.co.uk/itm/Portable-Super-Silent-Suitcase-Petrol-Generator-0-7KVA/400601921036?_trksid=p2045573.c100033.m2042&_trkparms=aid=111001&algo=REC.SEED&ao=1&asc=20131017132637&meid=6982320937949955067&pid=100033&prg=20131017132637&rk=4&rkt=4&sd=181410688586

I know I'm being a bit cheeky to one the old hands here, but...

A petrol driven thingy to charge an electric bike? really?

 

[stevieb]

is this what i i need
maplin 12volt modified sinewave 1000watt invertor
this doesn,t use cigarette lighter but is connected directly to the vehicle battery?

 

[flecc]

I know I'm being a bit cheeky to one the old hands here, but...

A petrol driven thingy to charge an electric bike? really?

Yes really, for all of us! At least 75% of the power from our national grid comes from fossil fuels.

 

[Deleted member 4366]

I know I'm being a bit cheeky to one the old hands here, but...

A petrol driven thingy to charge an electric bike? really?

It's the only sensible way to do it. The van is driven by fossil fuel. What's the difference?

 

[smee]

It's the only sensible way to do it. The van is driven by fossil fuel. What's the difference?

Yeah true

 

[smee]

Yes really, for all of us! At least 75% of the power from our national grid comes from fossil fuels.

Certainly true in Australia - nearly 100% I expect, small amount of hydro. I thought Europe had a lot of nuclear power though, and Europe was big into wind and wave power too?

 

[smee]

is this what i i need
maplin 12volt modified sinewave 1000watt invertor
this doesn,t use cigarette lighter but is connected directly to the vehicle battery?

Well, after the last new info, I expect one half that size will work. Probably even smaller.