Working out inverter capacity for bike-battery charger

Jan 18, 2019
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Will someone check my working out, please ?

I have a Shimano charger that is rated "100-240vac at 2.5amp" input and "40-44vdc 4.4-4amp" output
W=V * amps, 230*2.5=575w
So at a minimum I need a 600w continuous output inverter.
That right?
 

DBK

Jan 9, 2013
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I think the power consumption is around 250W. The 2.5A input will be at 100V and as a check the output will be 40 * 4.4 which is a bit under 200W. Not much power will be lost by the charger (unless it gets very hot in use) so the actual figure is probably between the two figures.

You could probably get away with a good 300W pure sine inverter but 500W might be safer. :)

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Last edited:

hilldweller

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I wouldn't mind betting 300W would be enough on the basis of under 200W output.

600W should eat it. As PJ said, pure sine wave is good policy.
 
OP
Nigel Crompton
Jan 18, 2019
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Would it be worth removing the moulded-on plug and putting a new one on with the outer insulation stripped back so I can use a clamp-meter to measure the actual current draw (at various stages of the charging process) ?

Thinks: Why didn't I think of that earlier ?? :rolleyes:

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pappajohn

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Would it be worth removing the moulded-on plug and putting a new one on with the outer insulation stripped back so I can use a clamp-meter to measure the actual current draw (at various stages of the charging process) ?

Thinks: Why didn't I think of that earlier ?? :rolleyes:
A bit extreme!
 

pappajohn

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You could make a short extension lead using individual wires.
It could also be used for fault finding unusual load faults.
You still really need maybe 50% more capacity to prevent the inverter working hard and the fan constantly running, or overheating if no fan.

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OP
Nigel Crompton
Jan 18, 2019
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Flaw. The battery is fully charged, so I need to do 75km on the bike to discharge it somewhat.
On the back burner for now, then.

Cheers 'n' Beers
 
Sep 23, 2013
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A charger with an input voltage range as wide as that should be ok with a Modified Sine Wave inverter, although it may buzz a bit.

Depends on what else you want to use with the inverter. Pure Sine Wave is more expensive, has slightly higher conversion losses but is more versatile & you can plug anything in without worrying if the inverter will damage it.

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Last edited:

sallylillian

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Oct 29, 2011
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My bike chargers always seem to surge at first switch on. Do they have any significant induction load at startup which could throw a low powered inverter?
 
Apr 22, 2013
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My bike chargers always seem to surge at first switch on. Do they have any significant induction load at startup which could throw a low powered inverter?
My Bosch one doesn't quite the opposite. It hangs around for 10 to 20 seconds measuring the state of the bike battery before starting to charge.
 

sallylillian

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Mine are Bosch, similar about the thinking about it and then a definite surge. Maybe I will get a meter on it next time. It was only a query on my part based on an impression as I am next to my Victron when I plug them in.

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