I also see Octopus provides an API that can give the Agile tariff's half hour rates 24hours in advance - what would be really interesting (maybe a good challenge if anyone knows how to code?) would be a Home Assistant component that provides these half hour rates. You could then potentially setup an automation that would automatically choose the cheapest time period to charge your car each night..... a bit more of a challenge to setup for sure but I imagine its do-able!
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Best energy tariffs
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I also see Octopus provides an API that can give the Agile tariff's half hour rates 24hours in advance - what would be really interesting (maybe a good challenge if anyone knows how to code?) would be a Home Assistant component that provides these half hour rates. You could then potentially setup an automation that would automatically choose the cheapest time period to charge your car each night..... a bit more of a challenge to setup for sure but I imagine its do-able!
mikemillar
Member
That sounds really clever. The Powerwall 2 gateway is believed to be able to forecast cloud cover a day in advance, presumably integrating met data. I can do than manually, but automating it sounds clever. Coupling that with grid price forecasting sounds mind boggling!
Using the Raspberry Pi as an intelligent appliance control sounds interesting though. But I’m not really a techy, just did some basic programming and control stuff at Uni rather longer ago than I care to remember. I’ve got a Pi that I have used to monitor CH water temperature, but had to find out how to do it by looking on the web. Is there anything about intelligent control for Pi there, @jsteele? I couldn’t find anything on a first look.
Using the Raspberry Pi as an intelligent appliance control sounds interesting though. But I’m not really a techy, just did some basic programming and control stuff at Uni rather longer ago than I care to remember. I’ve got a Pi that I have used to monitor CH water temperature, but had to find out how to do it by looking on the web. Is there anything about intelligent control for Pi there, @jsteele? I couldn’t find anything on a first look.
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Theoretically I agree it’s feasible to take the half hourly charges from the supplier’s API and work out whichnare the half hours to use to have the car charged to the right % by the time one wants to leave.
I think it’ll be more complicated if one is prepared to handle any supplier who will offer the half hourly option, and a little trickier still to calculate the time needed to charge - it depends on factors which include ambient temperature, battery starting temperature, an efficiency curve.... so see things can only be approximated.
A Roadster owner produced a good forecasting algorithm for that battery; no one to my knowledge has yet repeated his painstaking work on the Model S/X battery.
Home Assistant is the system that I use running on my Pi (Home Assistant). It is open source and anyone could add a new 'component' (such as electricity prices from Octopus). This hasn't been done yet for any UK companies yet, but has for a few for US Power Companies. Using the already built in components (e.g Alexa, Philips Hue, Hive and Tesla) automations aren't too difficult to setup - I would by no means consider myself as someone who knows how to code, but still managed to setup a nice range of home automations so far.
Tesla control is already there so as things stand I'm thinking to setup some automations for the Octopus Go tariff, e.g. you could say charge your car when you have the cheap rate between the hours of 00:30 - 04:30, and only keep charging after this if the battery is still below XY%.
@simonog I think you're right, it would be difficult to get things so exact as I was describing in my previous post - there might still be scope to use electricity prices for some clever things, depending on how you use your car e.g. if prices are above x then only charge to 60%, if they are below y then keep charging to 80%.
My only dabble into home automation is with Philips Hue, which is easy to set up via an App. With EV charging I think it's safe to say you will get the lowest price in the dead of night (at least for now, but it will be a LOT different in the future when EV charging becomes mainstream!).
On average I need 3 hours charging per night, which would fit the Go Tariff perfectly, but actually in practice I often need much more than that on some days and much less on others. So I would set it to charge for the full 4 hour off-peak window every night, with a 95% battery target (instead of my current 80%) to provide a buffer to minimise any additional peak rate charging. Not so efficient for the battery, but certainly cheaper to run that way. I will just need to set up a simple automation to switch off the charger at the end of the off-peak period, with a minimum state of charge.
mikemillar
Member
WannabeOwner
Well-Known Member
Actually that's an interesting approach. Working with the Tesla API (to figure out charging rate etc.) is extremely fraught. People (like TeslaFi) have done it, and there is a thread on the main Tesla forum where people post their findings about the API, but documentation is scant, and I reckon its only people like TeslaFi , processing for loads of cars, that actually manage to figure out how it works - and be resourced-up to handle any changes promptly (they are frequent enough, and far reaching enough, to be annoying ... typical Tesla). Personally I'd forget that ... hence I like your idea.
You would need to know the SOC at the start of the night, but you could "scrape" that from the APP, or TeslaFi/other, or even figure out the API enough to just get that information once (a pitfall of the APi is that you get blocked if you make frequent calls, loads of snags like that, but a simple "What's the SOC" request at midnight might be OK ("OK" in the sense of not too much work, little risk of API changes, but you'll still probably have to mess with waking the car up, if asleep, and so on ...)
So .. armed with SOC you could then say "Car charges at 10% per hour" (my approximate guess), its currently at 60% so I can charge for 3 hours now and one hour prior to leaving, and adjust the "3 hours now" according to actual SOC.
Of course the snag is if you get a powercut during the initial 3 hour period (not much you can do about the second one ...). Most of the solutions I have seen work on charging to 80%, using active monitoring, but perhaps you could detect powercuts and resume charge so that the whole "3 hours" was done at the start of Off Peak and then the final 1 hours before departure,a nd avoided the need to interact with the API to achieve that.
I would like a warmer battery before departure in Winter, to shorten the time that the car is on reduced Regen ... but I've stopped shooting for that level of sophistication and just let the thing charge at midnight ... however I do use TeslaFi to schedule "charge to 100% before departure" on days when I am going far afield, which then also has the battery-warming benefit.
Whilst rambling on ... and on ... you could use TeslaFi scheduler to change Max Charge to 80% at midnight, let it charge on E7, and then change Max Charge to 90% an hour before departure (or an hour before the end of Off Peak). That would get you to 80% as soon after Off Peak start as possible, regardless of power cuts, and assuming power available resume charging an hour before departure / end of Off Peak
Some possible risk that resumed charging is slower on exceptionally cold nights when battery cold soaked?
Move to a Passivehouse ... no heating needed, much easier
And a LOT more healthy too (something I didn't previously know). (We also have whole house automation which we put in when rewiring was needed, if you are interested I posted a list of "possibly useless" functions we have configured on our HA in another thread)Similar threads
