Lightweight lithium battery for car

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flat tire   10 kW

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Lightweight lithium battery for car

Post by flat tire » Jun 22 2018 8:59pm

Engine is a BMW N55. It takes under 150 amps to start. Was thinking of going with the 40152S cell in a 4S1P config with aluminum busbars and cable since aluminum has better conductivity to weight ratio than copper. That means due to the density of aluminum the physical size of the conductors is bigger but overall weight is lower for a given conductivity. No longer using aluminum since it cold creeps and has issues with connectors. Just copper. The threaded cell is chosen for ease of permanent assembly into a high current system. This is replacing a heavy stock automotive battery. The cells burst 150 amps and with the 15Ah a no additional cells in parallel should be necessary to avoid running low. Also my car has some stupid "advanced" charging system with a fused and sensored cable that would be nice to eliminate. I may be able to code this thing out thru software and.

Questions:

--Anyone have a good experience buying the 40152S cell anywhere? I have a source at batteryspace but they are expensive.
--Anyone recommend another cell?
Last edited by flat tire on Jun 23 2018 11:40am, edited 1 time in total.

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Re: Lightweight lithium battery for car

Post by cheapcookie » Jun 23 2018 4:52am

you can find them pretty easily in the us, although they are better alternatives, especially from the automotive industry.
They are known as Headway cells, are from China.

The LTO thread is pretty interesting, much better power density than Liion, probably better than these as well.

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Re: Lightweight lithium battery for car

Post by flat tire » Jun 23 2018 10:45am

cheapcookie wrote:
Jun 23 2018 4:52am
you can find them pretty easily in the us, although they are better alternatives, especially from the automotive industry.
They are known as Headway cells, are from China.

The LTO thread is pretty interesting, much better power density than Liion, probably better than these as well.
What alternatives would you recommend? I have found the 40152S marked as headway but it's very cheap.

My understanding of LTO is it doesn't support the discharge rates necessary to start a car using a small battery. I want this battery to be as small and lightweight as practical.

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flippy   10 kW

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Re: Lightweight lithium battery for car

Post by flippy » Jun 23 2018 3:50pm

dont, those headway cells are crap. no way they still work after 6 months in a 1P setup.

better: https://www.ev-power.eu/LiFeYPO4-batter ... .html#tab2

this has the grunt to actually get the motor turning. the current while cranking might be 100~150A but the initial inrush current is usually around 300~400A. that will kill those poor headway's in just a few months.
i have used this battery for 3 years in a heavy 3.2L V6 (alfa) and now it's cranking a transit engine.

if you have a N54/N55 you need to focus on all the other crap that also pulls on the battery. no way that a single headway is going to keep that stuff running and still start that lump of metal. you need something more beefy. 60Ah like i linked above is what you would need and not have the car die because you left the radio on for 15 minutes.
dont forget that the ECU craps out at 9V.

just fyi: i installed this battery 5 years ago or so in a S55 (the M3 engine) and it is kinda on the lower limit to feel comfortable.
Lithium beats liquid dinosaurs.

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Re: Lightweight lithium battery for car

Post by flat tire » Jun 27 2018 6:23pm

flippy wrote:
Jun 23 2018 3:50pm
dont, those headway cells are crap. no way they still work after 6 months in a 1P setup.

better: https://www.ev-power.eu/LiFeYPO4-batter ... .html#tab2

this has the grunt to actually get the motor turning. the current while cranking might be 100~150A but the initial inrush current is usually around 300~400A. that will kill those poor headway's in just a few months.
i have used this battery for 3 years in a heavy 3.2L V6 (alfa) and now it's cranking a transit engine.

if you have a N54/N55 you need to focus on all the other crap that also pulls on the battery. no way that a single headway is going to keep that stuff running and still start that lump of metal. you need something more beefy. 60Ah like i linked above is what you would need and not have the car die because you left the radio on for 15 minutes.
dont forget that the ECU craps out at 9V.

just fyi: i installed this battery 5 years ago or so in a S55 (the M3 engine) and it is kinda on the lower limit to feel comfortable.
Do you have any actual experience with the headway cells? I ran and started a 4 cyl on 6Ah shorai with less discharge rating for over a year with no jumpstarts. Anyway, demand is supplied by the alternator while the car is actually running, the battery just makes up spikes if there's heavy demand. So if these cells aren't too overburdened by starting the car it should be no problem.

Anyway I bought the headways, they're in the mail, and we'll see what happens.

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Re: Lightweight lithium battery for car

Post by flippy » Jun 27 2018 11:53pm

yes, i have tested them on my V6 for the same reason as you. they work fine one some ecobox 4 banger engine but getting a 6 pot up to speed and deal with the massive load the electronics in that beemer has makes their life a LOT harder. i basically killed 4 of those headway's in under 6 monts. that 60Ah thundersky/winston battery is sill in perfect condition afer 4~5 years now.

also leaving it for a weekeind alone without a charger on the battery and you can push it home.
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Re: Lightweight lithium battery for car

Post by bigmoose » Jun 28 2018 7:33am

I think you should take a look at the classic A123 LiFePO4 pouch cells. IIRC they are spec'ed to around 300 amp peak discharge.
reference http://www.a123systems.com/automotive/products/cells/
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Re: Lightweight lithium battery for car

Post by flat tire » Jun 28 2018 11:21am

We'll see what happens with the headway. My car isn't running a lot of electronics and has negligible current drain powered down and locked up. The headlights are HID with low current draw. I will have to measure the running current but it's well within what the alternator can supply. I'm losing weight to the tune of <3000 lbs with no driver, so replacing a gigantic lead acid with a still pretty big lithium is unappealing. That's why I want this to be as lightweight as possible. Jumping the car via lipo and running purely on generator would be better, but I dunno if the alternator is designed for that. I've driven cars without a battery before with no damage but not longterm.
bigmoose wrote:
Jun 28 2018 7:33am
I think you should take a look at the classic A123 LiFePO4 pouch cells. IIRC they are spec'ed to around 300 amp peak discharge.
reference http://www.a123systems.com/automotive/products/cells/
Uh, thanks but where can they be purchased???

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Re: Lightweight lithium battery for car

Post by flat tire » Jul 09 2018 4:30am

OK, I assembled the cells with aluminum bus bars wrapped it in tape and bolted some temporary lead terminals onto the + and - bars.

It does start and run the car. Voltage sags down into the 6v range although cranking is fast. I've been monitoring the charging system before installing this battery and the car likes to charge around 40 amps, sometimes 60 or more. The car has a shunt on the negative terminal and monitors all this.

I'll probably continue to run these cells as is as long as they crank the car smoothly.

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flippy   10 kW

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Re: Lightweight lithium battery for car

Post by flippy » Jul 09 2018 4:39am

you know they only have a 5A charge rating and a 30A hard charging limit? :roll:
Lithium beats liquid dinosaurs.

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Re: Lightweight lithium battery for car

Post by flat tire » Jul 09 2018 5:49pm

Turns out most of what I thought was charge current was actually being routed to other systems thru the power block on the + terminal. Anyway, the battery is working great and should soon find a new home under the passenger seat. That will let me eliminate several feet of heavy cable. Also, with the battery fully charged the sag on startup is about the same as the old lead acid. No hesitation at all.

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Re: Lightweight lithium battery for car

Post by Punx0r » Jul 10 2018 5:49am

Just for reference, the minimum voltage you'd expect to see on a healthy lead-acid starter battery during cranking is 9-10V.

You're right, most of the charging current from the alternator is bypassing the battery and powering the car's electrics. It's only the current to recharge the battery after cranking (or using accessories without the engine running), but you'd need an ammeter between the battery and the car's wiring to measure this, although you could get a good approximation based on the internal resistance of the battery and the alternator output voltage.

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Re: Lightweight lithium battery for car

Post by parabellum » Jul 11 2018 3:48pm

flat tire wrote:
Jul 09 2018 5:49pm
Turns out most of what I thought was charge current was actually being routed to other systems thru the power block on the + terminal.
The problem will be if you have almost discharged battery for some reason. After start, generator will try to push in all Amps it can generate. You can end up with a very sad battery under your passenger. :D

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Re: Lightweight lithium battery for car

Post by DVDRW » Jul 13 2018 1:53am

How you implement LVC for car battery? Latching solenoid exist?

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Re: Lightweight lithium battery for car

Post by flat tire » Jul 22 2018 11:57pm

Still running this battery, no issues.
DVDRW wrote:
Jul 13 2018 1:53am
How you implement LVC for car battery? Latching solenoid exist?
What do you mean?

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Re: Lightweight lithium battery for car

Post by flippy » Jul 23 2018 12:32am

how do you prevent the battery from going under 2.5V?
Lithium beats liquid dinosaurs.

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Re: Lightweight lithium battery for car

Post by flat tire » Jul 23 2018 2:12pm

flippy wrote:
Jul 23 2018 12:32am
how do you prevent the battery from going under 2.5V?
No need whatsoever. Aside from sag under load when starting, the only chance for that is if I leave the car sit. The alternator charges it continuously while the engine is running. Right now I drive the car every day. If I don't I will either disconnect the battery or put it on a charger.

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