Existing solar panels and battery and thinking of getting EV vehicle

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moneymakeover

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Somebody probably had this configuration so here goes

I have an existing solar panel setup 8 panels
5kw inverter I think
With two 5kwh batteries

I'm on a smart plan with electric Ireland which charges me
9 cent between 2 and 4am
Then it's like
20 cent until 8am
And
33 cent from 8 am until 11pm

I charge the batteries nightly between 2am and 4 am and that is enough time for them to charge from the low is 20% to high 90%

My question: if I get a electric car and I want to charge that between 2am and 4am will there be sufficient power from the grid?
 
There will be plenty of power from the grid, but 2 hours isn’t enough to charge any car with a home charger, depending on the car you buy it will have 7kW AC charging (most)or 11kW AC charging (some). If you buy a matching home charger, depending on the car and its battery size it’ll take 6-12 hours to full charge at home. You currently can’t charge 10kw of battery in the window so a 40-80 kw battery in car will take a lot longer.

If you don’t drive much each day you could build up charge daily though.
 
Thanks everyone
I think I might need to switch provider to get bigger window
2am to 4am seems very restrictive

But with low car usage and charging every night I might get away with it
 
moneymakeover said:
if I get a electric car and I want to charge that between 2am and 4am will there be sufficient power from the grid?
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Your house will most likely have a 63A main fuse. It sounds like you’re charging your solar battery at a rate of about 15A. Assuming you don’t have a heatpump then you’ve got say 40-40A capacity spare. A typical home EV charger is 32A.

As others have said, be careful that the EV rate is actually in your interest. My sense is these are a bit of a gimmick, the very low rate aimed at distracting you from noticing how high the rate is at other times of the day. In my case anyway (2 EVs, house battery, heatpump) a basic day/night/peak rate works out cheaper and is far more flexible - no faffing around trying to squeeze everything into a 2-4 hour window, you have all night. Time your house battery to only be used from 5pm and you’ll never pay be peak rate.

In terms of getting an EV charged in various time windows, if you consider that most EVs use about 20kWh to do 100km of driving and a home charger will add 7kWh in an hour, then you can add 35km for each hour you charge. 2 hours charging per night should give you far far more range than the average person drives. But to my earlier point, we find it much more convenient to be able to plug in just once or twice a week and use the full night to charge up.
 
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Yes that whole business of timing the battery discharge is a major headache
I got a second battery to last be through the day which works most of the time

If i only use the battery from 5pm there is a risk it won't all be used though?

And in summer time I'll be getting units at 9 cent
And selling them back to the grid at 20 cent?
 
By the way, in my inverter settings
Self use mode
I have amps set at 75 amps (up from the default 50 amps)
Now that's split across two batteries wired in parallel, giving maybe 37.5 amps each
If that setting is even used?
 
moneymakeover said:
If i only use the battery from 5pm there is a risk it won't all be used though?
Click to expand...
True, you’d probably need to tweak it based on your typical usage. Maybe 3pm or 4pm is better for you. You could also force discharge from 5pm (instead of self use) so it is exported to the grid, this will definitely empty the battery in a couple of hours.

On your question about the self use current setting on the inverter, that’s referring to 50A at the battery voltage (48V) not mains voltage. It’s only 10A once the inverter converts it to the 230V the house uses. So yes by changing it to 75A it will allow the battery discharge at a faster rate which would be used if you had say a kettle and oven running at the same time. It’s set to 50A because discharging the battery slower increases it’s longevity, though realistically you’d only be going over 50A very occasionally without something like a heatpump or EV charging.
 
Zenith63 said:
In my case anyway (2 EVs, house battery, heatpump) a basic day/night/peak rate works out cheaper and is far more flexible - no faffing around trying to squeeze everything into a 2-4 hour window, you have all night.
Click to expand...
I’ve got 2xEV with short city commutes, 15kWh battery and a good chunk of solar PV, and I moved to Pinergy with 3 hours at 6c, the rest of the day at ~40c, and export at 25c. I moved to them in September and using up the full battery by 7-9pm these evenings makes me very nervous! It should work out more cost-effective over a full year but I do miss the old 11pm-8am rate at times, for sure!
 
moneymakeover said:
My question: if I get a electric car and I want to charge that between 2am and 4am will there be sufficient power from the grid?
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You cannot assume that there will. It depends what the supply is like where you live.

Generally in most of the country the grid will supply all the power you need, however there are areas where the power supply will not provide 6kW no matter what set up you have.
 
I'm still concerned about what I'll actually get at 2am

Thinking out loud with 7kw charger, for two hours each night, and I think Electric Ireland is a good deal compared to the others I'd be getting 14kwh
Which would give me maybe 70km of driving which is fine, on balance.

But if I'm also
  • Charging 10kwh solar batteries
  • Running tumble dryer for 2 hours
  • Heating the immersion for 2 hours

Will the grid give me the amps? I think it will
Geography-wise I'm living in Dublin
 
Your import capacity is 12kw

Car charges at 7kw per hour

Battery charges at 5kw oer hour

Therefore 2 hours is ideal to charge both

14kw charged into your car each night would give you about 90kms whoch should ve enough for most people. If charging that each night but not driving some days youll quickly find that youve a good % on your car most of the time

Just run your other appliance on the bight rate rathen that 2 hr ev window. Still a decent tariff.

Have you got a HP?
 
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ArthurMcB said:
14kw charged into your car each night would give you about 90kms whoch should ve enough for most people. If charging that each night but not driving some days youll quickly find that youve a good % on your car most of the time
Click to expand...

As a matter of interest would a prolonged period of only partially charging/discharging an EV battery have any adverse implications on the lifetime, the capacity or the effectiveness of the battery? Presumably it would it mean that while some of the cells are constantly being drained and recharged some others would remain completely static for long periods. I assume that the active cells will lose capacity sooner than the static ones, (although perhaps the management software is sophisticated enough to share the load across the entire battery).
 
Marsupial said:
As a matter of interest would a prolonged period of only partially charging/discharging an EV battery have any adverse implications on the lifetime, the capacity or the effectiveness of the battery?
Click to expand...
The opposite, this is actually better for these types of batteries. Keeping the battery near 0% or 100% is bad for the battery, as are full charges because they create a lot of heat. There’s not much in it for modern EV batteries, but it’s certainly not bad for them to do small top ups rather than lots of 0->100%.

All cells charge together by the way.
 
ArthurMcB said:
Have you got a HP?
Click to expand...
What's a HP?
High power charger?
I don't even have a EV
Just considering the options and if they won't all work together that's a reason to postpone
We have a good system going where we use the tumble dryer at 2am
The immersion is heated
And the batteries are charged

One thing I don't get is why the electricity providers penalize during peak hours?
I mean why can't they encourage nighttime use without adding a penalty?
 
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