How come nobody has attempted to replace their car battery yet?

[Pierre]

That's about it. The car's electrical system is built around a lead acid battery. If you stick a lithium battery in there everything goes out the window. Assuming the alternator survives the encounter the car is still going to treat the lifepo4 is as if it's a lead acid battery. That means extended high voltage charging and then being sat at higher than what is commonly considered dangerous for a lifepo4 to be at, 13.8V float charge. If you want to knock the cycle count of a lifepo4 to hell sticking it inside a hot engine bay and holding it at elevated voltages for extended periods is exactly what you want to do.

Further , if you have a stuck starter solenoid or defective starter motor , you will destroy a LiFe battery in milliseconds.

 

[GXMnow]

Yeah, they won't take a high current draw more than a few milliseconds.

 

[Hedges]

If BMS disconnects battery while alternator is running, voltage spike will kill alternator. Would need a voltage clamp circuit to make that work, like TVS/MOV around 17V and a capacitor.

Now about cranking amps, I do have a portable jump-starter containing lithium. Maybe that is for a more reasonable cranking current and can't do 1000CCA or even 600CCA.

Stick with AGM for cranking, which can produce high currents and accept high charge currents. Maybe have some form of lithium house battery for accessories, charged from electrical system and able to recharge AGM battery if it gets drained.

 

[Michael S]

You can use capacitors and a small lithium for a starter battery.

Is it possible?

Build a portable solar box with 105 a h Deka battery while the box also is equipped with positive and negative battery post. Just received my 100 amp hour battleborn and I want to put that in the Box in place of my AGM Deka oh, I guess the question is will I be able to use the battery terminal...

diysolarforum.com

Edited

 

[snoobler]

Could it have its own DC-DC converter?

If BMS disconnects battery while alternator is running, voltage spike will kill alternator. Would need a voltage clamp circuit to make that work, like TVS/MOV around 17V and a capacitor.

Now about cranking amps, I do have a portable jump-starter containing lithium. Maybe that is for a more reasonable cranking current and can't do 1000CCA or even 600CCA.

Every portable Lithium jump pack I've had is not LFP. The voltage typically works out to 3S NMC or equivalent. They also swell like a sumbitch when they fail... splitting the whole case apart.

 

[toms]

Some people talk, some people do.

I’ll wait another 5 years or so until i give further details of my setup - it’s only been in the car for 2 years so far.

 

[gnubie]

You can use capacitors and a small lithium for a starter battery.

https://diysolarforum.com/threads/is-it-possible.12589/post-141036.

I'm not sure, but I think the forum is trying to tell us something when it comes to using lifepo4 in the engine bay to start the motor*.



*the thread posed the question but all the information in the thread including the youtube clip was about hooking up capacitors to a standard but undersized lead acid battery, remove the trailing . from the link to see the thread

 

[Michael S]

I think I fixed the link

 

[gnubie]

Some people talk, some people do.

I’ll wait another 5 years or so until i give further details of my setup - it’s only been in the car for 2 years so far.

Do let us know how your lifepo4 cells stood up with the car's charging strategy and temperatures in the engine bay. If nothing else it will give a good indication of just how well an alleged 'drop in' lifepo4 battery will cope.

 

[Hedges]

Could it have its own DC-DC converter?


Every portable Lithium jump pack I've had is not LFP. The voltage typically works out to 3S NMC or equivalent. They also swell like a sumbitch when they fail... splitting the whole case apart.

Although I am a complete newbie regarding lithium (other than my prior work as an aerospace engineer, where I dealt a little bit with those things being carried in confined crew quarters and then launched into space), I knew enough to be afraid ... very afraid.

So I didn't consider a power pack to put under the seat of my wife's car without making sure it was of an intrinsically safe chemistry.

Which this appears to be:

450 Peak Amp Portable Lithium Ion Jump Starter and Power Pack

Amazing deals on this 450A Jump Starter And Li-Ion Power Pack at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

What do you think?

 

[toms]

Do let us know how your lifepo4 cells stood up with the car's charging strategy and temperatures in the engine bay. If nothing else it will give a good indication of just how well an alleged 'drop in' lifepo4 battery will cope.

Only the Maxwell Supercap is under the engine bay.
The LiFePO4 is located in the cabin and has blocking diodes so that it can only supply current, it is charged via a DC-DC converter.

 

[gnubie]

OK, then that's a different approach to what was being proposed here. I have no doubt that will work so long as the supercaps can take the heat, and being maxwell they probably can.