# Charging cycle battery using an inverter



## MikeCo (Jan 26, 2008)

Does anyone know what size inverter I need to charge the battery used on the electric bike.
I tried a 300 watt but the red warning light came on.

Mike


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## MikeCo (Jan 26, 2008)

I've done a bit more research now and I'm beginning to wonder if I need the more expensive inverter with the modified sine wave.
Anyone know please?

Mike


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## gaspode (May 9, 2005)

Hi Mike

I would have thought that the 300w inverter should be plenty big enough to charge bike batteries, what does it say is the input current/wattage is on your charger?

The "modified sine wave" inverter is the cheaper version (suitable for most jobs), a "full sine wave" inverter would be the more expensive option. Some chargers don't like modified sine waves but most will cope OK.


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## cronkle (May 1, 2005)

Mike, 
How are you connecting the inverter to the power supply? I get a similar reaction from my inverter if I connect using the cigarette lighter plugs. If I crocodile clip straight to the battery terminals that solves the problem.
Something to do with the resistance/contact areas that those with more knowledge than me would explain much better. 
Alternatively I am probably completely wrong.


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## MikeCo (Jan 26, 2008)

Hi Ken

I've just been in the van and tried it again in a different 12v socket and it seemed to be working as no red light came on the invertor and the battery was charging.
I will try it again tomorrow as we will be loading the van up ready for Spain so I can keep an eye on it for an hour or so.

Thanks 

Mike


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## gaspode (May 9, 2005)

Sounds as if you have too much voltage drop to the previous socket then Mike. Unfortunately manufacturers don't always use sufficiently heavy wiring for accessory sockets, and they make the cable runs too long. This means that under a heavy load the voltage available at the socket is below the nominal 12v. An inverter will often refuse to work under such conditions as it will have a "low voltage" cut-out. As cronkle says, direct connection to the battery will often help when using inverters. In any event, a 300w inverter will consume more than 25 amps under full load, far too much for a normal 12v socket which are usually rated at 10 or 15 amps maximum.


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## MikeCo (Jan 26, 2008)

The first time that I tried it I plugged it into the 12v socket which is above the sink, I then tried the 12v socket in the cupboard which holds the tv bits and pieces and from which the inverter works the TV and Sky box.
It may be that they are different in someway.

Thanks to all

Mike


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## trevorf (May 16, 2005)

Yes, the thickness of the cable and the distance from the leisure battery may be different.
As said before by others, best connect the inverter straight to the leisure battery with short and thick cables.


Trevor


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## weldted (May 1, 2005)

*inverter current*

load of mains appliance say 330 watts

divide by 220 (mains voltage) = 1.5 amps

divide 220 by 12 (battery voltage)= 18.3

number of hours running appliance say 3

18.3 x 3 x 1.5 = 82.35 amps

27.45 amps per hour

based on inverter being 100% efficient in truth 85% is good and no allowance for voltage drop from wiring etc.

Hope this helps.

as battery voltage drops amps will rise


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