Planning 1994 Honda Acty conversion!

Acty DCty said:

Anyone got any ideas for how we can load our motor to do out-of-vehicle testing? We'd rather not run it without a load, but we're not sure how to apply one artificially.

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The classic approach is simply a brake: mount a hub in a carrier, complete with a car's brake, and connect it to the motor with an axle shaft. A load cell in the carrier mounting would let you measure torque. That won't let you run at significant load for very long before the brake overheats, but it could serve the purpose. The term "brake horsepower" comes from the use of this sort of device - a type of dynamometer - to measure engine power output. More sophisticated brake systems have cooling systems, and use hydrodynamic brakes (like a car's automatic transmission torque converter) instead of a mechanical friction brake.

The better approach, but presumably way too much expense and work for basic testing, is to couple the test motor to a generator with its own controller, so you can vary the load (and use the generated power to partially recharge the battery used for testing). This is how good dynamometers work now.

In any dynamometer there can be a flywheel, usually huge, to simulate the inertia of the car which is going to be driven. The inertia is considered in the calculation of how much torque and power that the is producing... some chassis dynamometers (the ones on which as car sits, with its drive tires rotating big rollers) really only have a flywheel, and are used only to simulate acceleration runs.

We have been having a whole lot of trouble talking with our HL200200 controller (documentation here). What we have set up: Direct serial cable connection with the controller. We have confirmed that all pins are connected correctly. The switch is set to UART communication. We have been trying to send it bytes over serial, through both Python's serial module and CuteCom. We send bytes to the controller, but all we can get back is whatever we sent to it. Screenshot attached.

We aren't sure what we're doing wrong. Any ideas?

blackterminal said:

When you buy a J1772 interface kit from EV West or other sources it specifies you must earth to the car body so I think the answer to your question is yes.

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The answer to the question is not his recklessly concluding yes, but NO.

A charger earths to the chassis of the car for mains (your 120VAC/240VAC etc power source) shock hazard protection. A mains fault (short to chassis or reversed polarity power plug, for example) in the car and you leaning on it in the rain will trip the breaker or GFCI (if it's a small current leak that is large enough to stop your heart but not trip the breaker) if the chassis is grounded....with no mains grounding to the chassis of the car means the GFCI could be blind to your electrocution.

The charger itself, however, is supposed to be electrically isolated, by its design (you can buy nonisolated supplies, which are temptingly cheaper...don't do it) from the HV pack and traction circuit.

To be clear...the AC side of the charger's ground (from the incoming power cable) is chassis grounded, the DC side is not.

This is not something you guess, but you validate and verify as something called "due diligence" because not doing so and listening to us idiots on a forum can be lethal.

So you DO NOT connect either HV DC battery, or its isolated DC charger, polarity to the chassis. NO.

Update: we seem to be basically done building the drive circuit. Next, we're going to start taking gas parts out of the car.

Videos here with details:

• Setting up relays & interlocks
• Building a DIY engine hoist
• Programming the controller
• Setting up the onboard charger
• Testing the SepEx field
• Testing the DC-DC converter
• Messing around under the dash

Also, thanks for your feedback on the grounding issue. We also consulted a few electricial engineers & everyone seems to be on the same page (do not ground drive circuit to chassis). We incorporated this information into one of our videos. Our videos are aimed at the "I've never done this before" audience, so context like this is useful.