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makatron asked

Off-grid solar powered EV charger

Dear people

I am preparing project for my master degree, and my subject is off-grid solar powered electric vehicle charger. I need your help to check my calculations. I am bulding 9kWh solar system which will aproximetly produce 54.23kW daily. This calculation is done with average daily sun hours 6.3h with Victron solar panel mono 360W (working with 85% of their max). I need to install 28 panells 7 in series and 4 in parallel directions. Each panell is producing 1.9kW daily. 28 panell produce 8.56 KW per hour. Can I put my system to work on 48V, if solar pannel max. power V is 38.4V ? and my batteries are working on 25.6V ? Second question is choosing right charge controller. SmartSolar MPPT charge controller 250/100 can handle 100A and 250V. If I connect my 28 panells in way that I described (7 in series and 4 in parallel) how many charge controllers I need to handle all this power from solar panells ?(With my calculations that system require 2 * 250/100 MPPT charge controllers). And my DC load is going for Level 2 EV charging with 7.7kWh and rest DC current for Lithium Iron Phosphate batteries charging through quattro hybrid inverter/charger. Thank you very much.

Kind regards

battery chargingSolar Panelvoltagecharge controller compatibility
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4 Answers
JohnC avatar image
JohnC answered ·

Hi M. Random offerings..

* With that much pv, go 48V. The cost of mppt cc's & wires will double @ 24V.

* Delve deeper to panel stringing (we may just differ in the definition here). Your 250/ mppt is good for 250Voc in a single series string. Those 360W Victron panels are rated 47.4Voc plus temp co-eff, so likely over 50V in cold weather. So max 4x per series string.. and the mppt's will drive any standard Vbat you choose.

* With 7x of those strings available, say 4x of them into a 250/100, and 3x into a 250/85 would cover it.

* Given you're likely interested in data, the Smartsolar units are good, but a fully-fledged GX box and VRM graphs are better. With a quattro & Li batts in the system, that really reaches 'essential' status.

But keep asking as you need. Good luck with your Masters..


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JohnC avatar image
JohnC answered ·

The EasySolar boxes are convenient, and suited for some applications. But I think your needs go beyond that. They are made up of individual parts just brought together, but for you I'd recommend a 'custom' mix. Perhaps the best approach there is to talk to a Victron dealer:

https://www.victronenergy.com/where-to-buy

VRM means 'Victron Remote Management', and it's a gem. This a bunch of links to get a feel for it:

https://www.victronenergy.com/live/vrm_portal:start

Only one GX box (of several varieties available) will be needed in a single installation. Let's say a CCGX with a screen:

https://www.victronenergy.com/panel-systems-remote-monitoring/color-control


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makatron avatar image makatron commented ·

You are right, after some calculations I think that best solutions is to take other charge controllers with much more power. https://solar.schneider-electric.com/product/conext-mppt-80-600/ this one is great and it can handle 15 panels in series and 3 in parallel connection. Thank you again for your useful response .

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klim8skeptic avatar image klim8skeptic ♦ makatron commented ·

15 x 72 cell panels in series is about 750Voc @ 0c.

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JohnC avatar image JohnC ♦ makatron commented ·

I'm sure those Schneiders are handy devices, but the Victron 250/100's are more powerful, just differing in panel wiring needs. You really need to speak to a dealer to explain/design this fully, just grabbing data sheet figures to rough-out your system will likely disappoint.

Please take care..

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makatron avatar image makatron JohnC ♦ commented ·

Dear John, thank you again for your answer. After all this advices I decided to continue with Victron 250/100 charge contr. I managed to change PV wiring and now I need 4 charge controllers. Is it possible to connect all of them in one Victron quattro 15 kVA inverter charger ?

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ripper avatar image
ripper answered ·

You have not stated the type of EV or the amount of energy they need delivering. Cars by inefficient slowcharge via wall plug 230V need up to 3600W. A 3000 VA unit will not be enough as it is only rated to 2400W and derating. A bigger more efficient charger that can deliver 54kWh during daylight hours on AC will be 3 phase. Or you need lots of batteries for night time hours. Fast DC charging doesnt need AC equipment and a scooter can be charged by a 375 48 Phoenix but will not take 54 kWh in a day...

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makatron avatar image makatron commented ·

Dear ripper, I wrote that i need 7.2 kWh DC, but I meant AC power. I need for my EV charger power of 7.2kWh/240V/30A AC which is LEvel 2 . During the day panells must produce 7.2kWh/240V/30A of power, and also charge batteries with DC simultaneously. With all this loads, i changed some units and I calculated that i need 36* 360W solar panels, 3 schneider electric xantrex 80 600 charge controllers which can handle all that power from solar arrays. Thank you for your response.

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russ avatar image russ commented ·

Ripper is correct, you are mixing up units and therefore see confusing results.

Work backwards. Here is a simple version of how I would go about this.

Your EV charger needs to supply 7.2kw (=240v x 30A)

That means either 3 x 3000 kva or 2x5000kva inverters.

In order to supply that, you will need a certain number of batteries to supply the current. At that level only 48v makes any sense.

Lets say 1000ah.of battery at 48v, =48kwh of storage. So your array at 54kwh output per day will happily charge your battery in a day. (lithium don't like really deep discharge so in practice your 48kwh of storage is probably only 35 at best, so probably need 60kwh installed. Or use a different chemistry, eg redflow zinc bromine)

What charge controllers you need I can't help with.

Now, as to how many cars 48kwh would charge, a typical EV has a capacity of 25-60kwh. So you may get 1 or 2 vehicles per day., in about 7 hours.

If you provide only a Lower rate charge point, delivering the same charge over say 15 hours, you could get by with a single inverter, but everything else will stay the same.



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makatron avatar image
makatron answered ·

Thank you very much for your great assistance, if I understand you well, you are recommending me EasySolar-II 48/3000/35-32 MPPT 250/70 GX box with integrated mppt solar charger and hibrid inverter/charger all in one ? and what about VRM graphs (voltage regulator module ) ? If that is right name for VRM shortcut :)

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pierresmits avatar image pierresmits commented ·
I suspect VRM stands for Victron Remote Management.
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