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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

charging batterySolar 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:

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

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

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You are right, after some calculations I think that best solutions is to take other charge controllers with much more power. this one is great and it can handle 15 panels in series and 3 in parallel connection. Thank you again for your useful response .

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

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..

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 ?

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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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.

You are mixing up kWh and kW. Makes it difficult to follow.

If you are set on Xantrex a solar charger, why do you ask for Victron equipment?

So far your batteries (non specified) are being charged, no electricity going out (wallbox or vehicles charged with 48V, which would be unusual) though.

7.2kWh is likely kW, 240V means 2 phase in America or single in Europe/somewhere else? 30A is a lot and cannot be provided by one tiny Victron something 3000...

Even with the biggest array you will not get your demanded power on a bad day. The wallboxes need to be adjustable or dumped altogether depending on availability

I am not mixing kWh, EVoCharge EVSE which I am going to use can charge electric vehicle up to 7.2kWh with 30 Ah. There are 3 Levels of EV charging , level 1 up to 3 kWh AC,Level 2 op to 7.6kWh AC and Level 3 Fast DC charging up to 56kWh DC.If you read my other posts here you could see that I am not looking for 1 charge controller which can handle this amount of power. I am looking for how many charge controllers I need to connect together to work simultaneously and be effective. After reading peoples posts I saw that maybe best solutions is to find another charge controller which can handle more voltage and current from solar panels. My batteries for this project are going to be 25.6 Volt 200Ah lithium Iron Phosphate smart batteries. Place in Montenegro where this solar charger will be placed is going to be used for tourist who are coming with EV in summertime. In this time of period we have approximately 10 hours of sun daily, 5.6kW/m2/day of daily solar irradiance, and cloudy days less that 5 for a month. Now after all additional informations could you please help me to choose right charge controller :)

I cannot, although you don't see it, it is getting worse. In the first post you are also confusing kWp with kWh and kW, in the last post there is a wrong Ah. No offense, but if you want to build something like that, you should be getting these things right.

I consider the battery to be chosen poorly. At 7.2 kW discharge it is driven outside recommended specs by about 50%.. It then lasts for about half an hour or about 10 percent charge of say a Renault Zoe 41 kWh. I am not certain a Zoe will actually charge at 7.2 kW this was just as a guide how far this battery gets you.

It also restricts you to 24V when it has been established that 48V is really the way to go with this amount of energy demand.

The battery takes up to 400A of charge (again driven outside of recommended charge by 4 times this time around). Plus roughly 300A for the charger. There you have the amount of charge controllers. Now you need to think about shading and the likes, so more or less individual units might be neccessary. Everything depends on everything.

Your Evocharger is an american product, looks to me as if it were 2 phase 240V. Actually didnt care to look further into it if you dont want to provide these vital details yourself. I have no idea how to provide that either way.

Good luck on your endeavours.

Batteries can be weirder in series to raise their voltage on 48V. Evocharger can operate on 240 V and 50Hz which is the frequency of AC electricity in my country. As I know in America they use 120V and 60Hz AC electricity. I am sorry for bodering you, but as I can see from your posts you are not here to help me, just to interfere my posts...

"I can see from your posts you are not here to help me, just to interfere my posts..."

Some advice for you. You need all the help you are given.

What you are trying to achieve is not ordinary, and extremely expensive. Your future could hinge on the outcome your efforts.

Please do the basic math.

Wouldn't you like to disclose all the gear that you have planned? Ever more is popping up. Which makes it viable or very much not.

Then please look up "240V 120V split phase" on google or something and make me feel you understood the third time around, what I am trying to tell you or how you are getting around my concern.

At 48V I am not an expert on LiFePo, from what I have seen in Spec sheets there is severe restrictions, I read 80A, over halfing the output in comparison to 24V, when using one of these serial connecting devices, for whatever they are.

Better had proof me wrong or a have a plan to meet your energy demands, genius.

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 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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