Lithium-ion 12v Battery Replacement

[ME_Andy]

Originally Posted by redpoint5

any capacity rating

Voltage*Ah (given in the user manual)

From 10 minutes of googling, $1/Wh seems like a good, competitive price for LiFePO4 starter batteries.

[hayden55]

Chiming in have you considered rigging up an adquate bms and an electric blanket to mimick the stock battery on the ioniq? Lithiums aren't ever supposed to charge below freezing so you would have to design a circuit to turn off charging until battery temps above 32F or maybe even warm it to optimal temp around 60-70F then shut off your blanket, and the charging and discharging should keep it warm. Then at that point just have a thermal switch turn on and off a fan.
Also,
18650 batteries used are also a much much better option. Life cycles are so long, second life 18650 usually have like 95% life left.
It would also weigh like 3-5 pounds to it wouldnt take much to heat and cool.
I bought some LG1 3350mAh cells for a m12 milwaukee heated jacket. 1 pound. 12.6V charged at 10.05Ah (9 celll pack) has the same capacity as more than three of the oem m12 batteries. They pack a punch for their size.

[redpoint5]

My plan was to buy 2 lithium-ion batteries. The supercap would live under the hood and provide the cranking juice. The lithium-ion battery would stay in the glove box or somewhere accessible but out of way of the driver. I'd start off with a charged battery; something like 15v so the alternator stays off. By the time the alternator needs to come on, the cabin would already be warm from running the heater.

After parking the car, leave the battery connected. The next time I go to drive the car, I swap the battery with a freshly charged one (and warmed from being indoors). The supercap maintains voltage during the swap so I don't lose memory settings. The whole cycle repeats again, with me taking the previous battery with me to charge while the car sits parked.

No messing with battery heaters. Balance charging done on a proper charger every time I park the car at home.

[hayden55]

Originally Posted by redpoint5

My plan was to buy 2 lithium-ion batteries. The supercap would live under the hood and provide the cranking juice. The lithium-ion battery would stay in the glove box or somewhere accessible but out of way of the driver. I'd start off with a charged battery; something like 15v so the alternator stays off. By the time the alternator needs to come on, the cabin would already be warm from running the heater.

After parking the car, leave the battery connected. The next time I go to drive the car, I swap the battery with a freshly charged one (and warmed from being indoors). The supercap maintains voltage during the swap so I don't lose memory settings. The whole cycle repeats again, with me taking the previous battery with me to charge while the car sits parked.

No messing with battery heaters. Balance charging done on a proper charger every time I park the car at home.

I guess you already have this stuff? What car is this going in?
Also whats the point of buying two batteries to leave one out in the cold? When you disconnect to replace the battery you will still be resetting your vehicles computers.

[redpoint5]

Originally Posted by hayden55

I guess you already have this stuff? What car is this going in?

I have the supercap built, 1 battery (for proof of concept), 10 gauge copper wire, and a 300A breaker. The breaker might be rated a little too high, but I wanted to give myself the option of starting the vehicle using the battery if I wanted to, while still giving some protection against a short. I figure shorting a lithium-ion battery has fire potential, and with the battery living in the cabin, some precaution should be made. I might throw in a power resistor to limit current and then put a lower rated breaker or fuse for added safety. I'm not even sure if the 5Ah battery can supply 300A and trip the breaker. That's somewhere around 4,500 watts before the thing trips, assuming no voltage sag.

The test mule will be my Acura TSX.

I'll probably start a new thread if I get serious about this project, include some photos, a build description, and some data about various electrical draws that impact how long I can operate the car in "virtual alternator delete" mode.

Don't hold your breath; I have to find out where to live in a couple months, which might include buying a house. Lots of projects on my table, and I'm among the worst with time management (which is why I'm on here and not doing something useful).

[teoman]

Very good idea that i hope to implement one day.

What connector will you use for your battery packs? A server rack type connection, or something like in scifi movies where they replace “power cells” on space ships would be fun to investigate where you just push the batteries in to the slot and lock it in place.

[redpoint5]

I have Anderson Powerpole, XT-60, and bullet connectors. Haven't decided yet, but I'll probably go low-tech with some Velcro to mount the battery. I'd like maximum versatility to use the battery for other purposes. I'm leaning toward XT-60 since you can't screw up the polarity, and it's quick to connect/disconnect.

[hayden55]

Also if you wire two connectors in series you never have to completely disconnect your voltage from your system when you swap batteries. Whats your specs on your caps and planned battery setup? It seems like a lithium ion battery built with cells with enough capacity for a car would be able to discharge the 400A needed to start your car instead and be lighter.

[redpoint5]

You mean to say 2 connectors wired in parallel to maintain voltage...

That's a great idea.

I had bought a kit from Ebay a while back that includes balance LEDs for Maxwell 350F caps. The caps are rated at 2.7v, which in series (6s), and assuming good balance, means I'm safe up to about 16v.



Maybe the supercap is unnecessary. My Lipo pack is 5Ah, and rated at 60C discharge, so I should be good to briefly crank on it. I think I measured my car at 200A to crank it.

Here's an old video I made showing proof of concept of something similar using LiFePO4 and the same supercaps. It's not meant as a virtual alternator delete though, and just runs at standard voltage.

https://www.youtube.com/watch?v=LX_o3hl2Dv4

[hayden55]

I was going to say just use a Lead acid battery for the winter... But then I saw you lived in Oregon and thats like 10 months out of the year lol