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Discussion Starter · #1 ·
I have not come up with much info on being able to charge batteries without an onboard charger. In light of my space challenges is there something I can setup in my garage to charge batteries and not have those components in the car? I am leaning to a DC motor setup.
 

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DC motor, meaning 200V or so?
You could have an externally accessible connector (say an Anderson SB175) and just plug that into the charger. The BMS would have to be able to communicate as well, so maybe a high power connector and one for signals.
A J1772 port might actually make sense, because it's got 32A or so of current capacity and a few extra lines for carrying signals.

You'd probably want a set of contactors or relays so that the plug is not usually energized else it would be a shock hazard, especially in the rain.

Any charger that can handle the battery voltage would work.
 

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That's a good range, it also keeps charging currents lower for the same power.
How about a CCS plug and socket? That's fairly safe, and you could figure out some circuitry to fire the contactors when you've put the plug in.
AliExpress plug
AliExpress link
Rated for 150A and 700V, pleasantly overkill.

A pair of Leaf contactors would be sensible, they're available on eBay for cheap:
eBay link
(seller calls them 'contractors', I've bought 3 sets so far).
 

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Hi
I started off using an external charger - a really basic "bad boy" charger
When I went to the Volt cells I bought a second hand BRUSA charger

With that charger I installed it in the car

The only issue with an external charger is that it will require a couple of contactors to keep it safe
AND you will need a "pre-charge" system
If you couple the battery to your charger there will be a current surge as it "fills" the capacitors on the charger
The solution is to connect with a resistor in series - and then short out the resistor with a contactor once the voltages have equalised
I use an old kettle element as my "resistor"

I have set the BRUSA to a low current - so that I can plug in to any old random shed when I'm out playing
This does mean a full charge of my 14 kwh battery is about 7 hours
 

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Right -- can't believe I forgot about precharge!
Leaf contactor setup includes a small precharge relay and resistor.
 

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The good news...
Fundamentally, the functionality that you are looking for is exactly what every production EV with fast DC charging has... minus the onboard charger which isn't used for DC charging (it converts AC at the utility voltage to DC regulated to the desired battery voltage, and that will be done by the off-board DC charger). You don't even need it to be particularly fast.

The bad news:
There are multiple fast DC charging standards. Of course you wouldn't want to try any of Tesla's Supercharger standards without a Tesla car, but there's also CHAdeMO (possible to implement DIY, but falling out of favour), and CCS (difficult to implement DIY). While fast chargers are commercially available from many suppliers, they are rarely installed in homes so there is a lack of reasonably priced and readily available choices... and you would probably have to adapt something from a production EV for the part in the car.

The initially suggested idea of just using a common on-board charger, but placed offboard and connected with any connector capable of safely handling the current and voltage, is probably the easiest, although it would tie you to using only your specific hardware instead of public charging stations. If you use a standard connector but don't implement all of the proper signalling, you would be able to plug into a charging station using that connector but it won't turn on.

The only certified production battery-electric aircraft - from Pipistrel - has the same situation... they don't want to carry the weight and bulk of an on-board charger, and always return to the same base so they can have a dedicated charger there. They used some proprietary connector at first, and are now using (on the type-certified Velis Electro) a connector and standard specific to aircraft (SAE AS6968, from SAE committee AE-7D), so clearly there is not a single easy solution that everyone will agree on for a race car.

Formula E cars might be a good example, but they use some sort of custom plug and system from Enel X, and are likely changing it anyway as they introduce in-race charging (which will be very high rate, such as 600 kW, versus the current 80 kW between-race charging).
 

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Discussion Starter · #9 ·
@brian_ I am following and I will not need to charge away from my garage. Car is trailered and maybe 20 min of actual run time half of wqhich is 10 mph driving in paddock and grid then 6 to 10 min of hard running between 3000 and 5000 rpm with my custom gearing.
 

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If you want to try the aviation standard mentioned above, the SAE AS6968 connection is described in the Electro.Aero RAPID Charger CR030-01KV-A1 manual. This is a DC-only, 150 V to 1,000 V, 30 kW, 100 A max charger, powered from a 304-485 V 45-65 Hz AC three-phase source.

Based on the caption of the connector in this manual, the connector itself appears to be an existing standard - GB/T 20234.3-2015 - which appears to be is readily available, and has limits of 150 A and 750 V. It is intended for use with CAN for control, and seems to be part of a Chinese standard for DC-only charging.

This charger manufacturer provides a nice overview of worldwide charging connector standards, which explains that this is the DC (only) charging connection for China, which also has its own AC (only) charging connection. Most connector overviews don't include these GB/T connections.

While this GB/T DC-only system for China and aviation may be a close match to the race car situation, I don't see a clear advantage to it over more common automotive DC charging standards (and just not using the AC side if it is a combo type).
 

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@brian_ I am following and I will not need to charge away from my garage. Car is trailered and maybe 20 min of actual run time half of wqhich is 10 mph driving in paddock and grid then 6 to 10 min of hard running between 3000 and 5000 rpm with my custom gearing.
If you ever want to run an event out of your home area, and to be able to run on more than one day, you might want to make your garage-based charger moveable, if not conveniently portable. Use a plug-in AC connection with one of the NEMA standard connectors that you might be able to find (or adapt to) in another garage, and you can pack it with your tools.
 

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The answer is yes!

Simple. Put the charger on the bench or in a rack in you garage plug it in the wall.
Connect the output of the charger to you battery then turn it on.

A charger just converts AC to DC and controls the power output. Most of them are even pre-programmed for a certain battery chemistry.
 

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Simple. Put the charger on the bench or in a rack in you garage plug it in the wall.
Connect the output of the charger to you battery then turn it on.
Most of the detailed concerns are over that connection, such as avoiding open and exposed live high-voltage contacts.

It is true that with a dedicated charger and a car that is only plugged into that charger, most of the control and management concerns that are addressed by sophisticated charging connection protocols are minimized.
 

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No more concern than plugging into an EVSE. Just need a connector on the car with a cable on the charger or the other way around.
 

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No more concern than plugging into an EVSE. Just need a connector on the car with a cable on the charger or the other way around.
Because that's what it is... and to be the same you need to do all the protective work of the standard EVSE systems. It's not just a connector.
 

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Because that's what it is... and to be the same you need to do all the protective work of the standard EVSE systems. It's not just a connector.
Not so! For example the TCCH chargers some call elfin. They have either a CAN interface or an enable function. All that is needed is to connect the car battery to the charger and enable it or start the can messages. The charger does the rest. There is no need to complicate things for a bench too setup.
 

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Not so! For example the TCCH chargers some call elfin. They have either a CAN interface or an enable function. All that is needed is to connect the car battery to the charger and enable it or start the can messages. The charger does the rest. There is no need to complicate things for a bench too setup.
Protective work meaning plug detection, removal detection, battery isolation, etc. These are important.
Hence the contactors on the power lines, and BMS signaling over the CP/PE lines, along with the use of resistors and diodes to be sure the plug is connected before charging starts.
 

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Discussion Starter · #18 ·
Thanks for above. Yes I would make sure it is wired properly and safely. I dont think I would need "fast charging" as the car is only used 1 day a week so plenty of time to charge the day or evening before race day.
 

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Protective work meaning plug detection, removal detection, battery isolation, etc. These are important.
Hence the contactors on the power lines, and BMS signaling over the CP/PE lines, along with the use of resistors and diodes to be sure the plug is connected before charging starts.
The only thing in that list that might be needed is plug detection so you don’t drive away while plugged in. The rest is already in the charger.
 

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The only thing in that list that might be needed is plug detection so you don’t drive away while plugged in. The rest is already in the charger.
OP is using lithium batteries - BMS is necessary.
If battery voltage is going to be present on a plug accessible from the outside, it needs to have a disconnect between plug and pack to prevent killing people. That physically cannot be in the charger if the charger is outside the vehicle.
Charger also needs removal detection/shutoff to prevent nasty arcs.
 
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