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# 12 / 24 or 48v to 400V Boost Converter to charge electric car from solar panels

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#### tantric

##### New Member
hi guys, goes as follows...

i have 4 x 150watt solar panels (600watts) each of 16v and 8,41 Ampere max (those at best conditions, but i can expect 400/500watts)

and i need a circuit (at least 90% efficiency) to charge the 16kW battery of my electric car with the solar panels,
the battery is 330v @ 50Ah with 400v charging voltage, i only need 400v @ 1Amp or 1.5 Amp at the output (400 / 500 Watt)
(50Ah / 1A = 50 Hours needed to charge from completely empty to full)

i found this schematic that will boost 12v to 400v, but the IRF450 only can handle with 15Amps,
so im thinking in using 2 sets of 2 panels in series, and those 2 sets then connected in parallel to have around 24/32v 15Ampere input

what modification do i need to do to this circuit so it can provide stable 400 v at the output,
independent of the load and independent of input voltage (since the panels vary voltage from 12 to 16 depending on the current amps demand)

i suppose i need a voltage divider from the output diode to the 555 chip, but not sure where to connect it

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I assume you mean that the battery is 16 kWh.

If you're going to make a boost converter, buy a dedicated boost converter IC, rather than using a 555. You could put all the panels in series, which would make the voltage conversion easier.

Why do you need at least 90% efficiency? You will struggle to get that high and the input power is free. You could just have another panel or two. Also, you will get a good efficiency improvement with an MPPT circuit (maximum power point tracking) because the power from the solar cells will vary with sunlight intensity and temperature. There are circuits that will maximise the charging rate, but they are complicated.

There are many issues with charging an electric car. I guess you must be charging a plug-in hybrid, as 16 kWh is too small for a purely electric vehicle.

All purely electric vehicles (Nissan Leaf, Teslas, Jaguar iPace etc) and, I assume, the plug-in hybrids, need 12 V to be applied to the high voltage battery to get the contactors to turn on before charging can take place. You will need to get the car's systems to turn the contactors on, or bypass them completely, for charging to happen. Bypassing the systems may lead to the car's electronics misunderstanding the state of charge of the battery. A 330 V battery has many cells in series and you would want to make sure that the cell balancing is running when you are charging.

The 400 V systems on cars are completely isolated from the 12 V systems. The negative of the 12 V system is connected to the car body, while the 400 V system is entirely isolated, in the same way that your phone or laptop charge is isolated from the mains. You can't go connecting 12 V panels to the 400 V systems as there is the possibility of the solar panels being at 400 V compared to the car's body. So you will need an isolated converter to remove that danger.

I'm trying to work out what you are attempting to achieve with this. Gasoline has an energy density of around 132 MJ/usgallon. If the engine charges the battery with an efficiency of 20%, that comes to 26.5 MJ of electricity per US gallon, or about 7.5 kWh. So you would use around 2 gallons of gasoline to charge the battery, but probably less if you were driving, as regenerative braking will charge it as well. So that is a \$6 saving in 2 days of charging, or more like 4 days as the sun only shines half the time. It is hard to see how you will get a useful payback time.

hi diver, much grateful for your reply, the car is a purely electric Mitshubishi Imiev with 16kWh battery for feeding the motor, and a extra 12v battery for car systems, can you suggest a "a dedicated boost converter ic" that can handle this amount of power?

i guess the balancing circuit is included inside the battery...

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... the traction battery of a Mitsubishi i-MiEV (initial registration: February 2014), shown in Figure 4a. It contains 10 Modules of eight cells and two modules with four cells, which leads to a total amount of 88 prismatic cells, all connected serially using screwed contacts. On top of each of the modules, a PCB is mounted, which-among other things-contains an LTC6802G-2. This IC is designed to monitor up to 12 lithium-ion cells, which are connected in series. The same PCB design is used for the module versions with four and eight cells. When used with four cells, the PCB is not fully populated, as four of eight available channels are not needed. The eight-cell modules use a second PCB to connect the second half of the module to the four remaining channels. The PCB on top of the modules is called the Cell Management Unit (CMU) in the official service manual for the car [30]. In addition to voltage measurement, each PCB contains three temperature sensors, which are connected to a controller located next to the Linear Technology BMS ...

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My Pure Sine wave inverter generates an internal DC voltage of 400V from a 12V input before it PWM's the 400V to an AC Sine wave .... Seems it is doing all of the hard work already, just reverse engineer something along those lines. Just a thought

EDIT: Or better yet, just get a couple of cheap inverters and rectify the AC output

The car has a mains input that works at 120 V. I guess that it will normally be limited to about 15 A at 120 V, but it can run at 16 A or 32 A at 240 Vac. I don't know the details but there has to be some way that the charging equipment can tell the car how much current it is allowed to take.

I suggest you look into that, and see if the charging current can be adjusted so that it is always a bit less than the solar cells can provide.

hi beau, how is that? any inverter outputs only 220Volts... can you explain better??

This project is more complicated than you think. You need a MPPT controller. If you solar cells can out put 400watts and you only use 300 watts that is a shame. But if you try to pull 420 watts the cell will collapse and stop giving power. A MPPT controller will find the maximum power point every second and adjust to get the most power available. Using a "dumb" 555 will not work well.
12 / 24 or 48v
It is better to use 48V.
edited to fix spelling

Last edited:
My Pure Sine wave inverter generates an internal DC voltage of 400V from a 12V input before it PWM's the 400V to an AC Sine wave .... Seems it is doing all of the hard work already, just reverse engineer something along those lines. Just a thought

EDIT: Or better yet, just get a couple of cheap inverters and rectify the AC output

any inverter outputs only 220Volts... can you explain better?? how can i achieve 400 volts?

This project is more complicated than you think. You need a MPT controller. If you solar cells can out put 400watts and you only use 300 watts that is a shame. But if you try to pull 420 watts the cell will collapse and stop giving power. A MPT controller will find the maximum power point every second and adjust to get the most power available. Using a "dumb" 555 will not work well.

It is better to use 48V.

okey i can use 48v, where to get an MPT controller that will do this?

A 230 Vac sine wave has a peak voltage of 325 V. So rectifying the mains supply will give around 330 V. A lot of inverters have an output called "modified sine wave". They contain an intermediate DC supply at around 400 V, or the inverter output can be rectified to get back to 400 V.

A 230 Vac sine wave has a peak voltage of 325 V. So rectifying the mains supply will give around 330 V. A lot of inverters have an output called "modified sine wave". They contain an intermediate DC supply at around 400 V, or the inverter output can be rectified to get back to 400 V.

i have a 300watt inverter, how can i find the intermediate DC supply of around 400 volt inside the inverter?

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