Traction battery discharger shut off.

The cutoff voltages are 134 V, 84 V and 17 V respectively for each of the successive charge/discharges.

To answer your question, no.

But it might be fun to try and built an Arduino (or Raspberry Pi) WiFi enabled circuit that monitored the voltage and sent an alarm to your phone. Who knows, maybe it could also be programmed to shut off the discharger.

 

Interesting. Would be good if they could have communicated that with the installed customer base. Wasn't aware HA had changed its guidance on the cutoff voltages.

 

If you wanted automatic shutoff capability, you should have gotten the Intelligent Discharger.

That works well and is what you are looking for.

That’s what I have and it’s worth the extra in my opinion .

 

It’s always a time value of money equation .

With 2 kids and weekend commitments, not to mention work week commitments, downtime and automation are key.

Having others co-own also reduces cost.

 

Just poked around the HA website and couldn't locate the above posted voltages, was there a link you could share ?

 

I just had a look and found the info in the Light Bulb Discharger User Guide. It does indeed show a change in the termination voltages. The highlighted column is for Gen 2 and 3 Prius:


They changed from 0.1 V per cell, 0.5 V per cell and 0.8 V per cell to 0.5 V per cell, 0.6 V per cell and 0.8 V. This is good, because the second and third discharges should be quicker (and safer) than the initial recommendation.

I notice the automatic discharger is still currently advertised with the original discharge termination voltages.

 

Those are basicly the discharge voltages I used and stopped at 82 volts. I always thought the 17 volt discharge was too deep and would incur too much heat. Looks like my supposition was correct.

I did mine differently I never re-charged between Discharges. Just hit the voltage level and changed the light bulbs till it hit 82 volts and never went lower than that. Then full charge at the end. Worked great 2 years later battery Excellent.

I would recommend if the battery has not thrown any codes yet like mine don’t discharge it try just charging it first for 30 straight hours. The battery really likes that and may sufficiently wake the battery up. Does no harm And may work very good. Worse case is if that don’t get it then you can discharge it.
I do a 25 hour charge every 6 months. 30 hours is better. The battery really likes those full balance charges. Have only discharged it once.

 

As to the original question, I've toyed with the idea of reinventing that wheel just to see if I could do it. It requires too much recision to just use diodes or relays. It would take some sort of solid state amplifier circuit with solid state relays, but I've not investigated.

Something like this could be used as a basis.
Relay Switch Circuit and Relay Switching Circuit
But it would require circuitry to latch it, since once the discharge load is removed from the traction battery, the battery voltage will bounce back up and recommence the discharge.

 

Just add a powersupply of the intended voltages with a series diode?

So if you want to discharge to 134V, make a 134V powersupply that can (easily) feed the lightbulb or whatever load you have to empty the batteries and wire this, with a series diode, into the battery pack. The pack will discharge up to 134V and then the external powersupply will start to light the bulb (or feed power to the load) so the pack won't discharge any further.

Not fully automated, but a fairly simple way to discharge to a specific voltage and stop there. You will still need to manually check if it has reached the end voltage, but it won't discharge too far.

I am building my own charger (very simple version but with a CC option) and but found and will pick up a professional powersupply next week (CC/CV or even constant power (CP?) up to 500mA and 1000V (!)). I may try my own idea soon...

 

Sure..... everybody can build themselves a 134 volt power supply. Load regulated to .338.

 

That's the point, it doesn't have to be regulated to 0.338A. As long as it can supply enough current it doesn't matter if it is 0.5A capable or 10A capable. It will only start contributing once the battery voltage drops below your intended voltagelimit.

Calculating example: 60W lightbulb + 60W lightbulb in series (120V bulbs) are used to discharge the Prius battery. Load is about 0.5A at 240V battery voltage but drops down to about 0.28A at 134V.

Now find a 60W 2x45V transformer, put the windings in series, rectify them and buffer them with an appropriate capacitor and you'll have a 125-130V DC voltage. Now add the diode and feed this into the battery. It can also be a 100W or a 500W transformer, just as long as it can supply (0.28x130xsqrt2=) 52W, which it needs to do once it is supplying all the power for the two 60W lamps at 130V.

The battery will now never discharge lower than about 130V.

Obviously I am assuming a decent amount of understanding of electronics, but I certainly hope someone attempting this already has that in the first place.

Obviously having a Variac will greatly help with setting the 'helpervoltage' correctly. And if you do happen to have such a thing, never, NEVER use this without an extra transformer to galvanically seperate your output from the mains.




But it was just an idea that is easily doable if you have some transformers and capacitors lying around. Which I am sure only a few of us do.

 

I think that can work. Clever.

 

The whole reason, as I understand it, for doing the discharge in three stages is that the cells could be so far out of balance that you could reverse a cell long before hitting that final or even second discharge voltage. So, on an initial discharge, I would not rely on an 80V safety cutoff.