this path is not as bad as it seems, as once the DC-battery is full, the mppt --> inverter-AC at 93-95% efficientsolar DC -> mppt -> battery DC -> inverter AC -> onboard AC charger -> HV battery DC
this path is not as bad as it seems, as once the DC-battery is full, the mppt --> inverter-AC at 93-95% efficientsolar DC -> mppt -> battery DC -> inverter AC -> onboard AC charger -> HV battery DC
AC charging would not be possible while driving, since the EV's onboard systems don't allow that (try putting your EV into Drive while it's plugged in...).I seriously need to add solar panels to a van/truck sized electric vehicle.
Does anyone here have the expertise, or can recommend a professional or company that could actual pull this off?
I can handle the physical mounting and wiring of panels.
What I really need help with is engineering the electronics to integrate with the existing EV.
I would have ~ 6 kW of solar - possible configurations:
- one string of 1016 V, 5.9 A
- two strings of 508 V, 5.9 A
The electric vehicles I am looking at have 525V, 400V, or 320V batteries.
So a MPPT that can handle those high battery voltages would be required.
Or, a DC to AC to DC conversion .
And, of course, I want the solution to be as efficient and convenient as possible.
- Direct DC charging would be more efficient that AC conversion.
- Charging while driving is ideal. Other suboptimal possibilities include charging a buffer battery then charging the main battery while stopped.
How can this be done?
- Direct to battery/BMS? A max of 6 kW should not be a big strain on the batteries compared to the normal draw of the motor, and influx from regenerative braking and high power charging.
- Via the existing charger? Could the existing charger be made to accept the fluctuating solar input?
I really appreciate any tips to help me realize this!
Thanks!
I only wish I could build my own vehicle from scratch, but sadly this is beyond what I could reasonably achieve legally.it's been done many times . It depends on your budget of course and design boundaries. How many panels are the 6kw ? a simplest and probably most dangerous is a simple block diode, no control, no smart, nada; just need the PV voltage to be higher than the EV pack. But don't do it
World Solar Challenge - Wikipedia
en.wikipedia.org
There is no reason for them to include a MPPT to support a significantly larger solar panel than whatever engineering performance art meme inspired them to include a solar panel on the car. And the MPPT for the type of panel that fits on the car may not have an operating range (voltage or current) that you care for.Whichever company does that first, I will be buying their car.
Well the ipandee might not cut it but you get the idea.Thanks to Tesla and ipandee it’s possible to build one. https://tesla-cdn.thron.com/static/UMDJDV_North_American_DC_Charging_Connector_Datasheet_HTKQS6.pdf?xseo=&response-content-disposition=inline;filename="North-American-DC-Charging-Connector-Datasheet.pdf"
You need enough panels to supply 500v at 200-400 amps.
Then you need a charge controller from ipandee thanks Mike G for restarting the high voltage revolution. https://www.ipandee.com/large-mppt-solar-charge-controller/
And voila! DC fast charging for your vehicle when the sun shines. Add a high voltage battery bank and another charge controller and you can charge at night theoretically. Good luck!
It might be easier to start with a hybrid solar inverter designed for HVDC batteries and figure out how spoof its communications to work with a car.Well the ipandee might not cut it but you get the idea.
OK, let's try to answer your questions, but first, have a look at this video:Thanks @meetyg!
For me, I am past the "if/why" to do this. I am doing this out of necessity, not to save money – this vehicle will be my off-grid home and I will not have access to grid power nor fossil fuels. So, I have to get this done one way or another.
In the worst case, I know I can achieve this with a buffer battery and charge the main battery via inverter while the vehicle is stopped. But this hacky solution makes me cringe.
One of the "off the shelf" trucks I am considering does have wide open access to battery packs, BMS and high voltage cables.
And if I do a Tesla swap or other conversion, I would have access to them too, although this likely will be a more costly solution that with an "off the shelf" EV.
I would get a professional to connect the proper gauge wires safely to the high voltage lines.
This part seems doable.
The part that I am struggling with is understanding how the existing EV electronics behave.
This doesn't seem to be common knowledge and this is why I am reaching out here for help.
Does anyone know exactly how the EV electronics behave?
Here is my speculation.
Consider the following state of the vehicle...
A) The EV is off and NOT connected to a charger.
There are no heavy currents (motor, regen, charger) in or out of the battery in this state.
Could an MPPT be connected directly to the battery or BMS in this state?
An MPPT normally handles the various charge cycles of the battery at the different levels of charge and will slow down when battery is near full and not overcharge.
Is the BMS still on and operating? If not, would it have to be switched on somehow (even though the rest of the vehicle is off) so that it could so it job of balancing and safety monitoring? Or, could the MPPT charge the battery safely without the BMS?
I noticed that the BMS has two set of cables. One set is the plus and minus high-voltage lines connected directly to the battery and a bundle which I assume is sensing and control signals between the BMS and all battery modules. The other set is two high voltage lines to the motor controller. I see another three phase lines between the motor control and the motor itself.
Would the MPPT be connected directly to the batteries or to the other side of the BMS?
B) The EV is off and charging from shore power.
Being able to charge from solar and from shore power at the same time is not a critical requirement for me, but just for completeness let's consider this state.
The charging connector would getting a AC or DC charging station.
Obviously the BMS will be on and doing its job of balancing and monitoring safety (current and temperature are within limits).
The built-in charge controller may have an expectation of the current level expected. For level 3 DC charging the power level probably is negotiated and could be changed dynamically.
Does the charge controller adjust its behaviour based on information from the BMS?
The MPPT would be adding a relatively smaller but potentially fluctuating amount of current.
I suspect that the built-in charge controller would monitor the shore power and shutdown if parameters were outside expected range, but the built-in charge controller probably won't be aware of any extra current going into the battery from the MPPT.
The BMS will see the sum of the currents from the built-in charge controller and the MPPT.
Would the extra unexpected current from the MPPT possibly trip some safety limit?
C) The EV is on and possibly being driven.
The BMS would be broadcasting safe operational limits (over CAN bus), specifically the maximum amount of current in and out of the battery.
Other control systems would be expected to respect these limits. For example, the acceleration rate of the vehicle may be limited, or the power recaptured by regenerative braking may be capped.
If the BMS would detect that the safe operational limits were being exceeded what would it do?
What would happen in this scenario?
- BMS says max current into the battery is X.
- Regen braking obeys and caps the current it produces to X during strong braking.
- MPPT is adding an extra current of Y.
- BMS detects a current of X + Y into the battery. Y is relatively small but still, it could trip a limit.
It would be nice to be able to charge while driving. Can it be done safely?
Any insight into this would be appreciated.
Thanks!
depends on the car, the BMW i3 has it's safety contactor box external of the battery.Unless you pry open the HV battery pack (not easy and not recommended) , and get a direct connection to the BMS (before the contactors), you won't have access to the HV battery.
"Communication" is a interesting description for a simple 1khz PWM signal which originates from EVSE. During AC charging the car does not talk to the EVSE on the J1772 Standard. There is no negotiation, nothing it's one-way aside of the car closing a contact when you plug in.There is some communication going on between the OBC and the EVSE: Mainly negotiating the maximum charging current allowed by all factors: EVSE max charging capability, the CCS cable's max charging rating etc...
But again, the OBC controls the charging process and rate (up to the maximum negotiated).
Maybe you can hack one of the DC platforms. Dcbel would probably be able to go straight from panels to CCS. Or hide the AC conversion from you, heh.
this is the single reason why we don't have Vehicle to Grid - V2X.Although there are losses, it's a much simpler and safer solution than going directly to the HV battery. Another plus is that you won't be violating your EV's warranty. Most EVs have an 8 year HV battery warranty, which is very important.
Yeah, I didn't want to go into too much detail.depends on the car, the BMW i3 has it's safety contactor box external of the battery.
"Communication" is a interesting description for a simple 1khz PWM signal which originates from EVSE. During AC charging the car does not talk to the EVSE on the J1772 Standard. There is no negotiation, nothing it's one-way aside of the car closing a contact when you plug in.
The EVSE modifies a PWM signal to "tell" the car how fast it can charge. That cars OBC ramps up the charge until it matches that highest current (or below if the OBC doesn't have the capability)
In essence - a AC EVSE is nothing more the a fancy extension cord which tells the car it's maximum amps.
But as you state DC is different. That is two way communication. There is also a second contactor - which enables power to DC charge port.
While AC charging only turns on the battery contactor - DC turns on the second.
I recommend looking at the J1772 whitepapers and the documentation about the charging standard. It's a lot of reading but it tells you how DC charging and Vehicle to X over the port are working.
DC charging and discharging is decent simple in terms of the J1772 standard. But the cars Firmware must allow it. If they never had anticipated that the battery voltage goes down while DC is connected - some wizard programmer might have set a out of bounds condition and triggers an error.
Which specific whitepapers? If I randomly picked a J1772 documentation or whitepaper, I doubt it would say much about CCS and V2X because that is highly tangential.I recommend looking at the J1772 whitepapers and the documentation about the charging standard. It's a lot of reading but it tells you how DC charging and Vehicle to X over the port are working.