# Arduino PWM 235VDC Hybrid Battery Charger Using Mosfet?

#### Garch2020

Joined Sep 12, 2020
4
Hi,

I am looking to build a charger for my Prius Gen.3. Hybrid Battery.

The nominal voltage is circa 235VDC, which can peak at 250VDC. The charging / discharging current will be no more than 1.5A

I want to use an Arduino Uno to modulate mosfet(s) using the controller via PWM to charge the main hybrid battery.

I've looked around for example circuits but most off-the-shelf kits will not handle the voltage and power demands.

The closest I have come across is attached in a PNG below.

Any ideas or recommendations?

Thanks,

Alan.

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#### schmitt trigger

Joined Jul 12, 2010
510
Although the gate of the first mosfet is protected, for the second and third mosfets they are not protected against a voltage which may exceed the maximum Vgs rating.

That, and the complete lack of protections, like over temperature, fuses, reverse voltage, etc.

#### ronsimpson

Joined Oct 7, 2019
2,524
First most internet schematics do not work.
Next what is the voltage on the capacitor bank? If the input is 240V and the capacitors are at 12V the difference in voltage is 228 volts. Now we have 1A * 228V = 228 watts of heat lost. Q2,3,4 will need a large heat sink.

Is the battery really 200 to 300 volts? I just looked at the price? My used car cost that much. LOL
I would not use a home-made battery charger on a battery that costs a week's wages.

#### Garch2020

Joined Sep 12, 2020
4
First most internet schematics do not work.
Next what is the voltage on the capacitor bank? If the input is 240V and the capacitors are at 12V the difference in voltage is 228 volts. Now we have 1A * 228V = 228 watts of heat lost. Q2,3,4 will need a large heat sink.
View attachment 217018
Is the battery really 200 to 300 volts? I just looked at the price? My used car cost that much. LOL
I would not use a home-made battery charger on a battery that costs a week's wages.

Hi yes, 235VDC nominal, circa 20KW power output. A big best of a battery assembly. New main-dealer assemblies can cost $3000 -$5000 including installation. Boy, you are on a great wage

#### Garch2020

Joined Sep 12, 2020
4
Although the gate of the first mosfet is protected, for the second and third mosfets they are not protected against a voltage which may exceed the maximum Vgs rating.

That, and the complete lack of protections, like over temperature, fuses, reverse voltage, etc.
That's a fair point. Fuses etc I would include, the over-temp I would monitor using the Arduino. Also would include an opto- isolator between the Arduino and the MOSFET / Driver.

#### ronsimpson

Joined Oct 7, 2019
2,524
235VDC nominal
Input is 240Vac which is rectified & filtered to get 300Vdc, unregulated with ripple and the output is 235V.
That is 65V and 1A = 65 watts. I think we should use PWM to get the power loss down to 6 watts.

I think the power should be isolated to keep the car from shocking you.

New main-dealer assemblies can cost $3000 -$5000 including installation. Boy, you are on a great wage
I see them on line for $1500 in a box/not installed. Some are$900 more or less. I don't get big wages now.

#### Garch2020

Joined Sep 12, 2020
4
That is true. Toyota would then charge you another \$1500 to remove and reinstall. It's quite a job getting them out then back in again. Then if the replacement cells are not balanced there is a chance the battery ECU will reject them and report a hybrid drive fault. This assumes that you don't electrocute yourself if attempted at home. There are quite strict protocols to these battery assemblies to avoid injury or even death. And if you accidentally short them out, at 235v and 20KW, maybe up to 100KW if shorted which could result in some pretty fireworks and an earlier than expected visit to the afterlife . Also, the other side of the inverter-converter unit you are looking closer to 900V-AC. There are cheaper options, but they come with trade-offs.

#### MisterBill2

Joined Jan 23, 2018
13,746
For a charger delivering 1.5 amps from a fairly constant voltage you could simply have a transformer with a few taps. And since it is a mains powered system you will need to have isolation no matter what. There is some fully charged terminal voltage specification that should be available to know, and then it is a simple matter to cut off the charging when that voltage is reached. But since most vehicle battery packs are rated at a few KVA , charging at 1.5 amps is going to take a long time to recharge. So I suggest doing some math and discovering how long the charging will take at 1.5 amps.