When to charge?

[OriginalBigAl]

I normally charge on cheap overnight tariff. Tomorrow, Sunday, the difference in price between day/night tariff is 2.5 cents/kwh, and I want to put in 30 kwh of juice. The daytime temperature is around 11°C and night time -2°C. Would the subsequent increase in energy heating up the battery and electrics make the night time tariff less economical at night? The tariffs are day 15.5 cents night 13 cents respectively.

 

[JohnV6]

And I thought I was careful with money. I suspect at night as you would need 20% higher losses to make day time pay.

 

[OriginalBigAl]

The money was not really the issue. My car charges at 10.2 kW according to the wallbox and gives a temperature reading (of what I'm not sure). What it does not say is how long it's running for, but gives an input reading of kWh, which differs for different conditions. When cold it takes longer and as you would expect more is wasted as losses. If you get back from a drive and the battery is up to temperature then even if it's daytime in some cases it's just as economical to charge it straight away as opposed to letting it cool down, just to warm it up again and charge on night tariffs, more so if you are just doing a minor top-up.

 

[Everest]

I have an idea, if not too late...

• Put 15kWh in overnight at -2°C.
• Then another 15kWh during the warmth of tomorrow.

Report back tomorrow evening with the results.

& then you'll know for next time

 

[OriginalBigAl]

Do you think I'm made of money????? Oh alright, a bit late for this evening . will do tomorrow.

 

[gazza487]

I have found my SR on a freezing cold night would add around half an hour ish to the finish time in ismart estimated time (single phase 7kW). I assume it’s initially diverting some power to heating the pack up.

What the cut off temp is I really don’t know but that says to me it’s in the 3kWh range “wasted”. Not really wasted as the battery is warm when I went to work so the miles per kWh was higher quicker than usual but as you say dependant on when you are going to use it or if the residual heat is better.

One situation where our stupid high prices in the UK make it simple. 23p day or 7.9p night for me - it’s a no brainer.

 

[Everest]

The money was not really the issue.

Do you think I'm made of money?

Obviously, yes

 

[Everest]

One situation where our stupid high prices in the UK make it simple. 23p free in day (with solar) or 7.9p night for me - it’s a no brainer.

FTFY

 

[gazza487]

FTFY

Afraid not. SEG = 15.1p/kwh. Still makes sense to sell my solar at that price and buy back at night.

 

[Everest]

sadly I don't get paid for export

 

[gazza487]

sadly I don't get paid for export

On the old FIT ? Would be a very different story then

 

[Everest]

No FIT, unfortunately

 

[JohnV6]

Octopus will pay you 15p for export

 

[OriginalBigAl]

After being bullied into this (post #4) here are some results:

Daytime, preheated the battery for 15 min, dropping percentage to 25%. Outside temp 12°C. Charged to 53% using 15.55 kWh, taking 1.5 hrs.

Night time, no preheating. Charged to 80%. Outside temp 0°C. used 17.75 kWh taking 1hr 55min. Most likely, as expected.

I have worked out some interesting figures from this but before subjecting them to peer review I will repeat the experiments in the same and differing formats over the next few weeks .
Just in case no one knows , 64 kWh battery and 11kW charger taking in 10.2 kWh per hour.

 

[siteguru]

(61.7kWh usable)

 

[Bam Bam]

Octopus will pay you 15p for export

Is still only for those with MCS approved installations though?

 

[Everest]

Is still only for those with MCS approved installations though?

There was a trial scheme announced last year where you pay for Octopus to get export approval - not sure what the latest on that is and whether anyone has been successful