Charging an EV in an overly consumerist world

DIY
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1

I’m an old-school rural solar dweller, since 1994, surviving on minimal equipment. The new challenge is trying to charge an EV, without doing a $60k solar install, to divert power to a car.

The problems are:

Mppt breaks the power every 10 minutes to do pointless optimisation, so a large 48v buffer battery is required.

EV charging equipment is reticent to decrease output at any time, despite clouds and mppt variance.

EV manufacturers won’t make cars with a simple DC solar panel input, and component designers won’t build something that’s like a solar inverter that just plugs into a car charge socket.

DC safety standards stop DIYers working above 60V, and electricians are reluctant to do any work.

Installers, no matter how experienced, make systematic errors, like setting absorption time too low, or setting lifepo4 charge too low for top balancing, or setting battery shunts wrong. The systems are so over-complicated that the installer and electrician will leave the customer with problems and password wifi obsolescence.

I was talking with a ex neighbour who had created a solar powered pottery kiln consuming probably 5kw. He had also settled on using pwm regulators, because mppt often mucks around for 5 minutes. (I don’t know who writes the algorithms, but they obviously get paid for 0.01% on-paper efficiency gains, rather than just working.)

So, it does seem like the cheapest EV charger is to carefully select a PV array under 100V and put the output into $50 pwm, to a 48v lead acid battery array, and use that to power a 48V inverter, which will supply 240V at 10A to the car. The main control system is to cut off when the battery voltage drops, and resume when sufficient light appears to be on the panels. Probably using 3 photo detectors around the solar array. The other method would be to test the output of the inverter and check whether the battery voltage sags, without involving the car charger.

The idea is to design a charge system that costs less than the fuel or car. Ideas?

If I don’t reply, it’s because this forum is unfathomable, and I can’t find this post again.

4

The problem is that there’s no proper electrical training. On top of that, distances are enormous.

Both make it difficult to find training that deserves the name. You have to do some searching. Andy’s Offgrid Garage is a good information site.

You can use PWM controllers with lead-acid batteries, but they’re not suitable for lithium batteries.

Your system needs to be properly matched in terms of power, and the controls also need to be coordinated with one another.

Get yourself a Pro account and look through the information available there; then a few things will become clearer!

Half-baked information only leads to frustration