2nd Gen Prius PHEV Conversion (Enginer plug-in lithium ion battery kit)

[ericbecky]

Daox,
Good stuff. The circuit looks good and your testing seems to show so far that it's working as you wanted. I look forward to hearing more.

The charging process is definitely the biggest hurdle for most people who have the current Enginer PHEV kits. Even if they wanted to, most people are not able to watch over the charging process to the degree currently necessary.

[Daox]

This weekend was an EV build day for our local EV club. I went and shared what I was doing with the Prius and got some help with modifying the VOX circuit. We were able to remove the on delay that the circuit had built into it. However, we could not get the VOX circuit to trigger well off of the balancer alarm. It was much more sensitive to us just talking in the room. We figured that the circuit was more sensitive to lower frequencies than the higher frequency of the beeper. At this point, the option was to try and find a high pass filter that only allows higher frequencies through, or to dump the VOX all together. In the end, we decided to dump the VOX.

So, as a few here have suggested, we open up a balancer and looked at the signal going to the beeper. It should be usable, but I'm going to have to reprogram the arduino for this new situation. The beeper acts a bit oddly. Nothing that can't be programmed around though.

Also, since the last post, I have only used the kit once. The pack voltage seemed to drop down a fair amount, and I plugged it in when I got home to recharge. The charger's green light immediately went on. So... something isn't right, because I know my pack is not fully charged.

[Daox]

Last night I got time to work on the car. It still would not charge, so I turned up the charger's shutoff voltage. Previous to this when it was working, the charger was turning off right around 56.3V. After turning up the shutoff voltage, the charger did start charging The pack voltage stayed around 54.7V for quite some time before finally increasing. I finally disconnected it before retiring for the night. It was then at 55.7V and had pulled ~2.5 kWh. During this time I got no alarms and the batteries stayed pretty well balanced. Unfortunately, I won't be able to use the car today as I am not carpooling with the wife. Tomorrow will be the first day with the pack on in a while.

[NeilBlanchard]

Hi Tim,

It is curious to me that this kit takes this sort of tweaking in order to charge. Have you seen an improvement if the FE after installing the kit?

[Daox]

Yeah, the charging right now basically sucks and is a pain in the butt. Enginer is supposedly coming out with a new balancer that controls the charger and dc to dc in early February. I'm hoping this fixes things.

There is definitely a sizable increase in FE while using the kit. I haven't really been able to do much testing due to me and my wife driving the car all the time. However, I did take my first long trip (over 400 miles) this weekend with it. I filled up before leaving and turned the kit on. By the time the kit ran out, after about 55 miles, I was @ 56 mpg. After that, the mileage dropped down and I ended with a 48 mpg tank over 300 or so miles. I filled up for half of the return trip (mostly 60 mph cruise control driving), and the tank is right now at ~43 mpg. This is roughly what I have been getting lately (mid 40s) with the Prius in winter. So, it appears that the kit is giving me roughly a 20% boost while its on.

[ericbecky]

All of us with the current kits have to carefully monitor the charging process.

Sometime in the next month, the new kits sold will come with cells that have an overcharge protection circuit inside the battery module.

[Daox]

Ah, so its not a new balancer, its just internal circuitry inside the battery? Is there any undercharge protection?

[ericbecky]

Hmmm not sure. I'll find out and let you know.

[ericbecky]

Confirmed with Enginer that the battery itself cannot have over discharge protection because of the sag effect with which the voltage will drop as the current increases.

[Daox]

Yeah, thats what I was thought. Thanks Eric.