Solar EV charging

[Djs63]

Does “trickle” charging an EV from excess solar generated PV cause problems to car battery?

We have a Solax system with batteries and a Solax EV charger and it charges the cars a little bit when the house and domestic battery have no demand. This week with sun some of the day it managed 8, 10 & 12 kWh per day with the domestic battery at 100 % and sometimes the washer or dishwasher working.

[SimonSays]

No issues to the battery, but there are a couple of things to be aware of;

• Most cars won't accept a charge below 1.4kW (6A), so you need to have that amount "available"/"spare".
• Some cars will go to sleep and refuse further charge when they see an intermittent charge. For example, a cloud goes over, the "spare" generation goes below 1.4kW, charge stops, car goes to sleep and won't accept any more charge. My e-Golf does this on the stop/start nature of Octopus Intelligent Go. I don't think it's alone in this; some VW id cars have this issue too.

[Ken]

Simon,
I have heard that problem before but maybe its the Octopus link. The car cutting off being a signal to Octopus that you have finished.
I have charged my E-Golf with my Zappi charger set on surplus (to the 6A). The charger has stopped but resumes when the surplus gets to more than 6A again.

My further observations are that charging like this at low Amps is inefficient. With TOU tariffs and export paying 15p kwh then it is better to maximise the TOU tariff and export all your PV etc.

[Stinsy]

Does “trickle” charging an EV from excess solar generated PV cause problems to car battery?

We have a Solax system with batteries and a Solax EV charger and it charges the cars a little bit when the house and domestic battery have no demand. This week with sun some of the day it managed 8, 10 & 12 kWh per day with the domestic battery at 100 % and sometimes the washer or dishwasher working.

The first point to make is that charging your car on solar is nolonger worthwhile. You can export the solar at 15p/kWh and charge your car on 7p/kWh.

What "problems to car battery" are you imagining? There is no mechanism for trickle charging to harm a battery. In fact charging the battery slowly is much better for it. On the other hand, charging at 6A (the slowest the spec will allow), isn't particularly efficient, the charger (inside that car) uses the same energy to run its control system, throw the contactors, etc. as it would charging at 7.4 or 11kW. Additionally, many cars don't like the on-off-on-off charging and will refuse to charge if this on-off cycle happens too many times in a given timeframe.