Regulated Solar Charging

[MadTechNutter]

You might consider just building your own EVSE, e.g, from: https://www.openevse.com/ Then you can set the amperage to whatever you please.

Absolutely is now the plan
but I decided to design it myself with a self programmed PIC micro and build it inside the J1772 plug that just has a long cable that goes straight into the 230V of my inverter or house mains.

I will update, after the plug arrives that I ordered for a reasonable price here http://evbitz.uk/EVBitz.uk/Type_1_Plug.html and can get on with it.

Still a lot of planing. I am now thinking of using the house connection that I already made from the battery inverter and using an automatic transfer switch to switch it to the J1772 plug in the day and to the house power points in the night that are on a grid connected solar inverter in the day but is too weak for the car and the house together.
Apart from saving a lot of wire (panels and battery and inverter are in the back of the house, PHEV in the front) I have the RCD breaker from the house connection and wouldn't need to worry about any GFCI circuitry(basically the same thing) in the EVSE which would make things messy if I want to fit it all in the plug. Still a bit in deep thought there.
Open for any ideas or requests

[MadTechNutter]

Here is my self designed charger that fits my requirements but couldn't get the guts to fit inside the plug, the extra box is fine.
It has a 20 meter cable to reach the back of the house with my off grid system.
It tells my car to use only 5.3A, at least that is what my clamp meter shows.
...and of all things I found an outdoor RCD safety adaptor still new and originally packed for $10 just last Sunday at the local flea market

I have not made the charge current adjustable although that would only be a few lines of code.
At this stage I don't need to adjust it as 5.3A is awesome because my current grid-tied solar system can handle that without using any grid power.
5.3A x 240V = 1272W
Anybody who actually checks their solar system knows that a 1.5kW system never puts out more than 1.3kW in the real world.

My off-grid inverter also runs more efficient on that current too, so when some clouds pass by the off-grid house battery won't get to heavily loaded so I don't see any need for a feedback regulated system right now.
This might change in summer when I have the 12 dedicated solar panels up and running, which I am about to install on the roof soon.

It has a simple one button timer function instead that can be set and reset while it is charging. So if I see clouds coming I can set it to terminate charge between 1-4 hours or cancel that at any time without disrupting the charge.

One strange thing I noticed in the 3 days I am using my slow charger is that I am getting 3-4km more REAL driving range.
Absolutely same distances down to the 100m, same time driving, same traffic, I always watch exactly my econometer when I drive uphill and regen with the same paddle setting downhill.
This does not show on the dog, same 29Ah SoH, which I am now calling the bullshit meter because that is based on some software calculations as I see no true evidence of any measured capacity here.

Despite those extra kms I have never managed to complete the charge because the charge is ...errr.. slow and doesn't complete by the time for my second trip.
The two trips I do on weekdays are a bit less than 6 hours apart.
When charge is completed with the original charger the guesso-meter shows 45km but I come home with 1-2km left.
Incomplete slow charge showing 42km and I come home after the second trip(which is in the morning) with 5km left.
The car stands overnight half empty.

Tomorrow I will be able to do the complete slow charge but I won't be driving my two exact weekday trips so I will have to monitor this a bit longer to find out what is going on here.
At least I am not charging daily up to 100%, that was my intention.

I am happy to supply more details of my charger if required for the technical minded

[MadTechNutter]

One strange thing I noticed in the 3 days I am using my slow charger is that I am getting 3-4km more REAL driving range.
Absolutely same distances down to the 100m, same time driving, same traffic, I always watch exactly my econometer when I drive uphill and regen with the same paddle setting downhill.
This does not show on the dog, same 29Ah SoH, which I am now calling the bullshit meter because that is based on some software calculations as I see no true evidence of any measured capacity here.

Despite those extra kms I have never managed to complete the charge because the charge is ...errr.. slow and doesn't complete by the time for my second trip.
The two trips I do on weekdays are a bit less than 6 hours apart.
When charge is completed with the original charger the guesso-meter shows 45km but I come home with 1-2km left.
Incomplete slow charge showing 42km and I come home after the second trip(which is in the morning) with 5km left.
The car stands overnight half empty.

Tomorrow I will be able to do the complete slow charge but I won't be driving my two exact weekday trips so I will have to monitor this a bit longer to find out what is going on here.
At least I am not charging daily up to 100%, that was my intention.

Here the result of an attempted 'full' charge using my slow charger.
I got now 9.3kWh available on a battery hat has only 8.7kWh capacity and was charged to only 97.9%.
So I wasn't imagining things.
Battery is definitely not over charged, the 4.095V for a 97.9% SoC looks correct.
Please tell me what going on here?

[MadTechNutter]

I stand by my opinion that the SoH indicator on the Dog is calculated bullshit(from the BMU) but the displayed energy going into the battery while charging is true.
So this energy must be going somewhere.

I have a theory(just an idea) that by taking almost twice as long to charge that individual cells are getting balanced better. The weakest cells are given more time to absorb the charge without the earlier termination from a standard charge when they hit 4.1V.
This slow charging may have physical/chemical consequences like a possible reduction of their internal resistance although I have not heard of any in regards to Li-Ion

This is however common with other batteries, like NiMH where I have recovered many batteries almost from the dead with a very slow charge.


Edit: ...or the Dog is showing rubbish, I just swapped the kWh displays to Ah and the SoC is now only 28.5Ah and SoH 29Ah
Guess it is a bug.

[trevortron]

Following this thread, as I am very interested in reducing the charging rate.
Firstly I'd like to charge during the day while my PV's are generating - but I only have 1.5KW (1100 real watts!) grid-tie (we're not allowed any more than this due to the energy provider's influence on government) so if I could reduce the charging rate it would hopefully be covered by the panels.
Secondly if doing so will prolong the life of the batteries it would be well worth doing on the overnight charge when there's no rush.

[michael8554]

If you have a Type 1 plug I believe you can limit the current drawn by altering a resistor in the plug:

1500 Ω resistor – 13A cable
680 Ω resistor – 20A cable
220 Ω resistor – 32A cable
100 Ω resistor – 63A cable

This seems to be a non-linear relationship, so you will have to draw a graph to determine what resistance you need - or carry out some clever maths !