Anyone with an EV and a home battery have a method for charging the EV from the grid, but not from the battery? e.g: charge at night cheap, but don't drain the battery. I assume in that scenario you'd just turn the battery off with some form of automation - but what about during the day where I might need to charge the EV from the grid, but I want the discharge the battery into the house for stuff in there (dishwasher, washing machine, heater/AC etc). Is that even possible?
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Did a bit of lurking around Facebook groups (ugh) looking for other people’s experiences and apparently all I need to do is get the electrician to wire up the EV charger before the inverter’s AC output, that way it’s physically impossible for the EV charger to be fed from the battery (unless the battery is exporting to the grid, which if it is, I wouldn’t be charging the EV anyways). At least that’s how I think it works in theory, I could be wrong.
@decryption Yeah that’s pretty much it!
@stephengentle I feel a blog post coming
@decryption I was trying to understand this, but think I worked out what you and Facebook are talking about (without knowing specifics). It seems like the solution is moving effectively where the current measurement is happening.
Depending on exact scenario, this might be possibly solved in software
@xssfox @decryption that's my guess as well, moving it "outside" the inverter's "load" current measurement means it becomes part of the grid from the inverter's PoV.
I am guessing that means you can't use it during a blackout, because the inverter would consider that to be back-powering the grid. Maybe a non-issue.
@projectgus @xssfox yep can’t use it during a blackout, which is fine - I’d rather keep the battery charged for stuff in the house.
@xssfox it kinda can be - I can tell the charger to charge the car, and I can tell the battery not to discharge, but then the house will also pull from the grid. Might be able to configure it so that the battery only discharges an equal amount to what the house is consuming though, hmm. Would require a lot more per circuit metering, as you can’t just measure grid consumption to get the home’s consumption.
@decryption my inverter has a time of use (TOU) mode so I can set it to charge off the grid during a set time. If I just want the car to charge I set the charge point of the house battery to below its current state.
@decryption I have a fronius system, and the components can coordinate to do that. You can power your house from the inverter but pull from the grid for the EV.
@daniel oh interesting- you’ve got the watt pilot charger?
@decryption have you looked into EVCC, if your battery and stuff can be controlled from it I think you might be able to automate that (I don't have a battery though, so I can't be certain)
@lilstevie I use it and really like it - just no sure how I’d be able to tell a battery to say “charge the house but leave the car alone”
@decryption looking at the discharge lock stuff its kind of complicated like you can tell it to not discharge the home battery into the car but it looks like that might also set it so that for the duration of the charge the battery itself won't discharge either
@lilstevie yep exactly - not sure how to tell it “hey this circuit here, leave it alone”
@decryption With Sigenergy, I just set the AC Charger schedule to Fast Charging for the period of cheap power, and PV Surplus Charging the rest of the time.
@theether what about when there’s no sun and no cheap power? I find myself in that situation regularly in winter - does that “no battery boost” setting mean the battery isn’t discharged at all or just not to feed the EV?
@decryption Battery Boost allows you to charge the EV from the home battery, not that I use it that way. My car is generally home during the day, so easy to top it up if there is any sunshine or cheap power.
@decryption I think some bits need to be clever and charge from excess solar, or not from battery.
Mine is dumb, so I just have the car charge timer set to 9am-3pm and hope there’s enough sun. If not, it’s only 10c or something. And then turn the timer off and manually charge at night if I need to squirt some electrons in at about 10km/hr.
@decryption not sure what's possible but maybe the mode you want is charging the home battery from the grid at the same rate your car charges at
@mattrobertson at night/when grid power is cheap, that's probably a good idea - but if it's not cheap, but i still need to charge the car to go somewhere, but want to keep the battery available for other appliances, dunno if that'll work (or even if what I'm thinking of is even possible - maybe I should just charge the EV from the battery - which seems stupid to me)
@decryption doesn’t sound stupid, use what’s free now, charge either battery from the grid when it’s cheap if you need to
@mattrobertson something about charging a battery from a battery feels wrong? maybe it’s what other people do and it’s not a big deal
@decryption @mattrobertson how often have you charged your phone from a power bank though?
@jpm @mattrobertson big phone and big powerbank
@decryption I set the Tesla Powerwall reserve to a high number like 80-90% to force grid charge
@decryption Just to clarify, when you say "off the grid" what do you mean? Do you mean "without using any power supplied by the grid", or do you mean "using power supplied only by by the grid"?
From the context you seem to mean the latter, but "off grid" generally means "disconnected from the grid"...?
@kauer nah not off-grid, from the grid
