Battery charging - cost of

[danfoto]

We would like to work out how much it costs us each time we charge our pedelec batteries, and we know that our smart-meter display will show us the answer. However, it's a PITA trying to ensure that we don't use electric for anything else while the battery's on charge, so my question is - what's an alternative method? Is working it out from the charger rating going to give us a reasonably accurate answer, or is the rating on the label perhaps nothing to go by in the real world? Does the charger output vary as the battery fills up, or what?

What's our best way forward - without spending any money?

 

[Neilgtis]

Hi have a look it’s American calculator but should
Work
Neil

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[cyclebuddy]

A back of an envelope way to work it out (crudely)...

If your charger is 42v 2A (typical for a 36v battery), it's 42 x 2 = 84 watts consumed per hour. The consumption tapers down in a linear fashion as the battery nears full, and you also need to bear in mind conversion losses / charger efficiency, so a theoretical 84w may actually be 90w if you measure it.

To keep it really simple, a 10Ah battery / 2Ah charge rate would take 5 hours to fully charge. So take 90w x 5 hours = 450 watts, and if your electricity costs 38p per kwh (1000w), that's about 17p a full charge.

 

[Nealh]

Use an individual plug in power meter between socket and charger.

 

[danfoto]

Use an individual plug in power meter between socket and charger.

Alas, I don't have one. Hence the question ...

 

[Nealh]

£10 each or so on ebay.
Or go to Scotland where the landlady at the tea shop will charge £2 for a battery charge.

 

[PC2017]

38p per kwh

Are we including a portion of the standing charge?

 

[guerney]

Or go to Scotland where the landlady at the tea shop will charge £2 for a battery charge.

@matthewslack got off lightly. It's Scotland, where wire was invented by two Scotsmen arguing over a penny.

 

[danfoto]

Cheers chaps. The Batavus battery is 36v 11Ah, the charger's rated at 4A and we're on 35.64/Kwh, so unless my maths is even worse than I thought, it costs us something in the order of 20p for a more-or-less full charge.

(BTW, @Nealh - believe it or not, £10 or so is a lot of money to us. That's why I specifically asked how to find the answer without spending any )

 

[Nealh]

Over all battery charging has likely gone up 3 or 4 fold as the cost was only 5p or so.

 

[sjpt]

Skip the hours and the charge rate; just guess the overall charging efficiency is 80%.
Your battery is as near 400wh (36v * 11Ah) = 0.4khw as makes no difference,
so will take 0.4 / 0.8 kwh to charge = 0.5kwh,
so 18p at 26p per kwh.

This agrees with cyclebuddy above, just a bit less roundabout,.

 

[Andy-Mat]

We would like to work out how much it costs us each time we charge our pedelec batteries, and we know that our smart-meter display will show us the answer. However, it's a PITA trying to ensure that we don't use electric for anything else while the battery's on charge, so my question is - what's an alternative method? Is working it out from the charger rating going to give us a reasonably accurate answer, or is the rating on the label perhaps nothing to go by in the real world? Does the charger output vary as the battery fills up, or what?

What's our best way forward - without spending any money?

Without spending any money, you can only estimate, as several kind folks have already done for you.
Job done!
regards
Andy
PS. Those power used devices are not expensive (as already pointed out!), and can generally be used for most mains driven drevices.....and will probably be more accurate than estimating, but you will ONLY know if you buy one!

 

[sjpt]

but you will ONLY know if you buy one!

or borrow one.

 

[StuartsProjects]

Are we including a portion of the standing charge?

Why would you ?

 

[lightning]

How ever much it costs, it's a whole lot cheaper than going out in the car

 

[PC2017]

Why would you ?

I suppose - I feel for all those who have decided to turn off their energy, they will still be hit with a bill at the standing charge rate.

 

[georgehenry]

However much it is, if as is often the case I am using my bike to make a short journey to go shopping it is much cheaper than my car!

 

[WheezyRider]

How ever much it costs, it's a whole lot cheaper than going out in the car

Assuming the OP has a car. A big proportion of households don't own one.

 

[WheezyRider]

I am lucky, I can recharge at work for free. When I have to recharge at home I connect the charger to my solar battery and recharge from the sun.

 

[cyclebuddy]

Are we including a portion of the standing charge?

No I didn't, because if you're "connected" you're paying the standing charge anyway even if you use no electricity whatsoever. Prices vary markedly depending on where you are in the country, your supplier, and the tariff you've chosen. I just did a quick search, came up with this current table, and took a middling figure of 38p/kwh as being indicative.