Enginer Indicator Problems (and Solution)

A good thing about Prius PHEV conversions in general is that they mostly don't change the appearance of the car, except for an outlet on the bumper and a switch on the dash. However, this can also be a problem, because you don't know when something isn't working.

The Enginer system has two "indicator" problems:

1. You can't tell when it's charging and when it's done, without opening the bottom hatch (which may require unloading cargo).
2. The "low battery" indicator can't be seen in daylight.

I attempted to solve these two problems, with partial success:

The charger has a light that turns red when charging, and green when charged (or when the battery pack is disconnected). My preference was to move this light to the power connector on the bumper, but this was not practical. Instead, I found that it was very easy to get access to the reverse light in the tail light assembly, without even removing the cover.

My first step was to get access to the charger:

Once the charger was removed, I opened the side panel and removed the existing light:

I installed a jack in the hole where the light was. I used nylon washers because the 48v battery pack is not grounded to the case.

Here's the charger with the new socket:

I bought a 2-color LED and soldered it to the end of the cable that is plugged into the jack seen above:

Here's the only small modification made to the stock Prius. I cut a notch in the left reverse light socket to allow the wires to the LED to pass through:


The result: Here are pictures taken at dusk of the pack charging and charged:


The light looks much better than it does in these pictures. I can look out my front window and see the Prius parked in the driveway about 30 feet away. After dusk the light is very visible. This tells me several things at a glance: I can see if the cord is powered even when the car is locked. If the light turns green immediately when plugged in, then the pack is disconnected for some reason, such as a bad connection, the BMS under-voltage circuit triggered, or the 100A circuit breaker tripped. Since we have a time-of-use electric meter, my charging cord is plugged into a timer so the car doesn't charge until after 6pm. This light tells me that the timer is working.

The 2nd Enginer "indicator" problem is the dim "battery low" light. In an attempt to solve that problem, I removed the DC-DC converter and looked at the circuit where the red indicator light plugs in with the 6P6C socket. Limited tracing showed that the red LED on the dash was connected directly in parallel with the red LED on the DC-DC converter. When two LEDs are connected in parallel with a common current-limiting resistor like this, the current through each LED will be reduced by 1/2, reducing the brightness also by 1/2. So as a quick fix, I removed the LED in the DC-DC converter:


Unfortunately, I couldn't test this on the bench, so I put it all back together and used the car normally. The red light is brighter now, but it's still not bright enough to see in daylight. I'm going to have to ask Jack about a better solution, perhaps a lower resistor or a transistor driver circuit. The way the converter is constructed, it's very hard to get inside to modify it.

 

That's what I understand as well. Often the light will stay on for a few minutes, then (when the pack recovers?) it will turn off and the system will charge the battery again for a few minutes. It would be nice to know when this happens, for example if the PHEV battery goes low, I probably want to switch out of EV mode unless I'm close to my destination.

That's a great idea! I'll consider doing something like that.

As I posted in this thread, the BMS circuit is designed by the installer, 3ProngPower. They use a BMS module from Australia.

 

Yes, I charge overnight. I plug it in when I get home and leave it plugged in until I drive again.

No, the BMS does not normally disconnect the battery pack, unless the voltage on a cell is extremely high or low.

The BMS low voltage cutoff is to prevent a cell from being damaged by total discharge. It is a backup in case the automatic low-battery shutdown in the DC-DC converter fails.

The BMS high voltage cutoff is a safety to prevent a cell from being overcharged to the point of exploding. It is a backup in case the automatic charge-complete shutdown in the charger fails.

If the DC-DC converter and charger are working properly, then the BMS will leave the relays energized at all times, and the battery pack will always be connected.

The normal operation of the BMS module is to draw current and dissipate excess charge energy when one cell is finished charging before the other cells in the pack. When all cells have finished charging, the charger itself will stop charging and turn the "charged" light green. According to Enginer, the charger is made by the same company that makes the cells, and is designed to charge unattended.