Enginer PHEV automatic over/under voltage protection

Yesterday, I purchased two celllogs. I plan on installing these with the arduino to control the disconnects via the celllog's various alarms. Should be pretty easy and will automate the whole system.

 

They are using tiny capacity batteries compared to us. Their packs are normally a couple of Ah at most, where ours are 39Ah. Good to know though, and something to watch for over time.

 

Could you post a link to the mod? Obviously, this is the ideal setup for us.

 

Excellent, and its even very easy to do. Great.

I should have my celllogs this week. Unfortuantely, I don't have a 15A SSR yet. So, I won't have the charging disconnect working right away. Also, the arduino code will need some tweaking to work correctly with the celllogs. This will be no problem though.

 

The celllogs have arrived. They are very small which is kind of nice. The bad thing? They don't come with wiring harnesses for the batteries! I was under the impression that they did. The upside is that it seems like they'll plug right into the DB8 balancer connector. If they can't, it looks like a standard circuit board female header will plug into the connector. What did you guys use?





Here is the kit contents. You see it comes with a CD. It contains software for data logging which is pretty nice.




Here is a close up of the actual unit. You can see the two ports on the side...




One is the USB to connect to a computer, and the other is the very handy alarm port that I'll be using to trigger the arduino automatic disconnect. In the celllog setup, you can set the port to normally open, or normally closed, so it'll be really easy to program the arduino to read this signal.

 

Well, I'm back from vacation, and ready to finish this thing up! Today I took the time to reprogram the arduino for use with the celllogs. Using the celllogs really simplified the code. Basically, it waits for an alarm. When the alarm goes off, it will send a signal to disconnect the 110V power to the charger.

I originally had it setup so it would reconnect the power after 1 hour. But, since I believe that balancing at the bottom is probably a superior solution, I have taken this out of the program. Once the celllog alarms out, the charging will stop. If you want to keep charging, you'll have to unplug the cord, and plug it back in. This resets the arduino and start things over again. So, as soon as the alarm goes off it'll stop again.

I'm still working out how I want to do the 12V disconnect to the dc to dc converter. I'd like to keep this as simple as possible, and I still have the problem of two 12V inputs to the arduino. I need to find a way to power the arduino consistently, yet also allow for a way to reset it. I don't see this as a problem, just something I haven't figured out yet.

Also, I still don't have a solid state relay for the 110V power. I'll be picking that up this weekend. With that I'll get the automatic charging disconnect working which IMO is the more major part. Shortly after that, I'll hopefully get the automatic dc to dc converter disconnect setup and working.

 

You pretty much have it. When plugged in for charging, the arduino will be powered by a wall wart power supply. However, when on the road, the arduino will be powered by the 12V power going to the phev's dc to dc converter via the 'ready wire' on the Prius. By doing things this way, it will allow the arduino to reset via unplugging the cord, or by switching the phev kit on and off. If I simply powered it off the car's 12V, number one it would be on constantly (not a big problem, but it is a small constant drain). Number two, I'd have to add a switch or some timeout to tell the arduino to turn the relays back on to connect the pack again. It will just be easier to use if there are two separate power supplies.

The problem with this is what if the car is on and pack is turned on, but it is also plugged in to charge? Now, this could easily be avoided by just never doing this, but chances are someone will eventually do it and blamo, friend arduino. So, I think you're right and I can just diode the power supplies so I never have a problem.

 

Bleh, I just overcharged last night. I plugged in and forgot about it. A few hours later I went out and the pack was 57.7V, both balancer alarms were going off, and I'm sure some of the cells were very high. Its really time to get this thing running.

So, this weekend I finally collected the components for the PHEV disconnect. I got my solid state relay as well as a 5V power supply with some tab connectors which will be very easy to use. These both came from a friend of mine who runs a salvage company. Pics of the components and install to come tonight unless something comes up.

 

As I said, I have an update on this project. I got it wired up enough to test out and see that its working. I'll definitely need to get it all tidied up for use in the car. I also think I need to use some optical isolators to prevent any pack shorting between the two celllogs. For now, I'll probably just hook up one celllog to the arduino. I'm pretty sure I know which bank alarms out first. Anyway, instead of typing, I shot a video. If anything is unclear just ask.

edit: when I say maximum pack voltage I really just mean any alarm the celllog.

 

Three weeks go by very quickly. Tonight I got the additional circuit board all soldered up. It basically houses the opto isolators so no electrical connections are made where they're not supposed to be. So, there isn't much on it, still took a couple hours to make. It is nice and compact though.

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