Lithium-ion 12v Battery Replacement

[hayden55]

I more or less mean it doesn't have a 12v starter pulling 200A

[redpoint5]

Originally Posted by Tahoe_Hybrid

you so crazy to use #10 with a 300amp breaker
or you just wanted a incandescent bulb under the hood?

you need at lest 4/0 wire for 300amp breaker (short run) longer runs will need 350 gauge wire(350 is a industrial sized wire)

trying to start a fire?

What thread did you get that quote from? It isn't this thread.

As I said, the breaker is probably rated to high. It wasn't meant to protect against drawing too much power, it was meant to protect against a short.

Originally Posted by hayden55

Probably just too big. It will never ever even get close. The Prius hardly uses the 12v system.

The attempt was to start an Acura on 10 gauge, which would draw close to that amount if it could.

[Ecky]

I've started my engine on 10 gauge, but it's definitely much better with 2 gauge. I can't recall if my breaker is 120 or 150 amps, but I haven't tripped it yet starting my car.

[Tahoe_Hybrid]

Originally Posted by redpoint5

What thread did you get that quote from? It isn't this thread.

As I said, the breaker is probably rated to high. It wasn't meant to protect against drawing too much power, it was meant to protect against a short.



The attempt was to start an Acura on 10 gauge, which would draw close to that amount if it could.

#25


if it's for a second or two a peak power it might be fine 300amp breaker is incorrect for a normal load on #10 it offers no protection


a starter is connected via relay directly to the battery for 300 amps or so they most likely use #4 wire

most car MEGA fuses are 100 to 200amps rated short to ground

[teoman]

Ok, i got a bunch of capa. One maxwell module with smaller caps and balance LED’s from member TexasCotton. They were charged to 16.5V when I received them :S

I also got 20 2.7V 3000F cells.

Need to get to work.

[hayden55]

Originally Posted by redpoint5

What thread did you get that quote from? It isn't this thread.

As I said, the breaker is probably rated to high. It wasn't meant to protect against drawing too much power, it was meant to protect against a short.



The attempt was to start an Acura on 10 gauge, which would draw close to that amount if it could.

Oops my bad. Getting mixed up.

[redpoint5]

Originally Posted by hayden55

Oops my bad. Getting mixed up.

Nope, it was my bad. Post #25 is where the quote came from. I had done a search in this thread for certain keywords and it didn't come up, so I figured it came from a different thread.

I should probably just jump off the supercap and place a lower rated breaker in there, along with thicker wire. Maybe I'll just double up the 10 gauge.

[Tahoe_Hybrid]

Originally Posted by redpoint5

I've discussed replacing the 12v lead acid battery with LiFePO4 before since the voltages (in 4s configuration) and chemistry lend itself to direct replacement. However, the downside is the inability to charge when temperatures are below freezing, higher cost, and lower energy density when compared with other lithium-ion chemistries.

This thread by Luno got me to wondering if Lithium-ion batteries could directly replace a lead acid. It may be safe to charge these batteries without a BMS considering a 4s pack is well below full charge at the standard ~14v alternator output.

Has anyone experimented with an unmanaged (no BMS) lithium-ion 12v battery replacement? What are the potential issues with this? Would LiPoly be better for any particular reason?

There are 5 Ah batteries available for $30 online that would be a fairly cheap way to experiment with.

https://hobbyking.com/en_us/turnigy-...se-pack-1.html

Even if there is no way to get around needing a BMS, it should be a fairly simple matter to combine a Lithium-ion battery, BMS, current limiting resistor, and supercap into a 12v battery replacement that should last a long time and provide quick starts in any weather.

at this point a car battery size is not much more with lithium I see them with 1.733KWh =138AH for 465$ and you can get a 90AH for 150$* AGM type cells

* new from Walmart AGM H8 battery with 5 years warranty

465$ will buy you 270ah of lead acid AGM battery..

lead acid is catching up it's just a matter of time

[Tahoe_Hybrid]

Originally Posted by redpoint5

Nope, it was my bad. Post #25 is where the quote came from. I had done a search in this thread for certain keywords and it didn't come up, so I figured it came from a different thread.

I should probably just jump off the supercap and place a lower rated breaker in there, along with thicker wire. Maybe I'll just double up the 10 gauge.

i would still not do this single cable is the way to go mixing used and new cables, the electrons will still prefer to use the new cable over the old cable . the new cable will have less resistance then the old cable (i.e heat cycles and corrosion if it's visible or not)

you will be back to square one

this is what i would buy it's SAE J1127 grade cable
made in USA

eBay item number:302318840814


i do plan on getting capacitors soon but i'll use 0/1 with a MEGA Fuse 150 amps

[redpoint5]

It would be the same cable, just more of it.