Hi! I just got my first EV (toyota proace) and i am wondering about the DC charging possibilities.

Has anyone tried to directly plug Lifepo4 batteries in series into the DC charging port of the vehicle? As long as you match voltage and maximum amps i think it could work, but it feels like a dangerous thing to do.
It is a shame they dont give you the possibility of increasing the battery size with your own lifepo4 cells.

You will need a DC to DC charger with the correct voltage range to connect two different battery systems.

I would not try any direct connection without the appropriate middleman.

There’s a lot of “handshaking” for DC charging to happen between the car and the charger.

Not quite as simple as “jump starting”

Danger Will Robinson , Danger!!!!!

The rapid DC chargers are so expensive they are not for home use. I've seen some Level 3 chargers for sale, but usually no prices are listed and when its shown way out of my range.

Unless you really know what you're doing I would not try it. I’d prefer you not build this in your garage if you knew what you were doing and were my neighbor.

Its a bit more than just a DC to DC converter.

In early days of the Prius, there were expansion packs that were discharge only. They recharged on home 120v/240v overnight. You don't want to charge a lifepo4 from 0% to 90% in 30 minutes.

Well i dont want to be in the 'up in smoke' section again so i wont do anything stupid.
Does anybody has come out with an ingenious way to increase the range with diy batteries?

Aridom82 said:

Well i dont want to be in the 'up in smoke' section again so i wont do anything stupid.
Does anybody has come out with an ingenious way to increase the range with diy batteries?

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The only thing I've seen a few people do is put a couple of server rack batteries in the trunk, hook 'em up to an inverter, and then charge with the EVSE (level 1 or 2) as if it was plugged into a wall outlet. It's not ideal but it does work. But you can't charge while driving. The EV must be parked.

Edit: I forgot to add that this was done on a Prius Prime (plug in hybrid) that has a charging port. The regular Prius is only a hybrid and does not have a charging port.

Level 3 charging is about 400v. The high voltage growatt battery is 400v. You have the pieces to level 3 charge an ev. Now you need to build the communications for level 3 charging.

I think the max discharge rate on the growatt is 1/2 c, so it would take 2 hours or charging to transfer the power.

Weight is also a problem. 5kwh of power is 100#. Most cars have about 1000# of carring capacity. Also a lot of mass behind you that can crush forward in an accident.

Aridom82 said:

Has anyone tried to directly plug Lifepo4 batteries in series into the DC charging port of the vehicle?

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Prius hackers were doing this 15-20 years ago, turning 2004 and later Prius hybrids into plug-in hybrids. The car had no charge port, so they hacked directly into the HV system to access the battery. This guy also hacked into the HV system to send power from rooftop solar panels directly in the HV battery without an inverter.

To go through the DC charging port you'd need a circuit board and software that speaks the CCS protocols. You have to send the correct signals so the car will close the contactors and so forth. I imagine some hacker projects do that, probably for solar more than range extenders, but that's what I'd look for as a starting point. It sounds like you want this to work while driving, which is an additional complication since I'm sure EVs have interlocks to make sure the port is disabled while driving.

I don't expect to see commercial products for any of this -- too limited of a market.

So it looks like a Proace has a 400v nominal system, 108s3p li ion. I dont know what it actually limits discharge to but if it were to allow it to drop to 3v/cell that would be 324v on the low end.

Anything that rectifies from or inverts to 220-240v ac has a ~330-370v DC bus you could tap into and feed to your battery. It would not fully charge the battery but it would 'offset' the drain by however much wattage you were putting in.

So ostensibly you could simply get some external battery in 12, 24, 48v etc, buy a 220v inverter, tap into its DC bus, and hook that to your battery. The problem is you'd have to DIY the current limiting aspect of it as an inverter or a power supply etc isn't current limited on the input to the bus (except by a fuse maybe), but is limited by how it draws off the bus for its output. So if you had an actual ~400v dc power supply it would current limit itself, but if you just tap into the high voltage DC bus of some cheap device you have to handle current limiting some other way.

SO what im saying is my ideas are bad.

Also you shouldn't do this at all unless you're competent (which in most cases means TRAINED) to work safely around high voltages and utilize proper protective equipment.

Doggydogworld said:

Prius hackers were doing this 15-20 years ago, turning 2004 and later Prius hybrids into plug-in hybrids. The car had no charge port, so they hacked directly into the HV system to access the battery.

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And every single one of the outfits offering commercial products went belly-up due to poor longevity. I personally have a system taken from a Gen2.

DIYrich said:

In early days of the Prius, there were expansion packs that were discharge only. They recharged on home 120v/240v overnight. You don't want to charge a lifepo4 from 0% to 90% in 30 minutes.

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sunshine_eggo said:

And every single one of the outfits offering commercial products went belly-up due to poor longevity. I personally have a system taken from a Gen2.

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these died because they're anti corporate. line can't go up with things like this!

gotbeans said:

these died because they're anti corporate. line can't go up with things like this!

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Huh? They were slapped together hunks of shit. Even at a $1000/kWh premium, they still couldn't survive.