# Start a car with IMR cells?



## Art (Oct 29, 2011)

Hi,
sorry if this is in the wrong place , but I was here thinking , and there is probably a easy answer , if it is possible to use a cluster of 18650 IMR cells to start a car?

I was reading the post below and I see each cell is able to do safe at least 15AMPs. But the problem is that my understandings in eletronics is not the best so...

Imagine a car that uses a 50amp battery , how many , if possible , 18650 IMR cells will it be needed to do the same work?
And if it is able to start the car , can it be used after that ? Be charged with the car charger etc?

Once again , sorry if its in the wrong place or this is a really stupid idea 

Regards,


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## flashflood (Oct 29, 2011)

Art said:


> Hi,
> sorry if this is in the wrong place , but I was here thinking , and there is probably a easy answer , if it is possible to use a cluster of 18650 IMR cells to start a car?
> 
> I was reading the post below and I see each cell is able to do safe at least 15AMPs. But the problem is that my understandings in eletronics is not the best so...
> ...



Starting a typical car takes 500-1000 amps at 12 volts nominal, sagging to not less than 7V. If you put four cells in series that would get you 15V nominal at the same current, say 15A. Now multiply by 50 cells to get 750 amps. That's a total of 200 cells. All safety issues aside, it seems impractical. Better to carry a purpose-built spare starter battery in the trunk.


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## mvyrmnd (Oct 29, 2011)

I've never seen it done with IMR's but there's a company making LiFePO4 dropin replacement packs for cars. Their name escapes me at the moment


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## Art (Oct 29, 2011)

The current battery im using to start my track car is only 40ah 330AMP cracking power and it starts fine , my idea would be to get something able to do enough power to start the car. It only needs 2 to 4 seconds.
If I use series of 4 packs of 18650 and imagine that in the best case it would do 30amps 3 pack of 4 cells would have more less 100amps... lets imagine it is enough to start the car what problems could I have with the cell pack?
Risk of explosion on start? Will it be able to charge with the engine alternator? Or would it have too much power?

I know this seems stupid , there are a lot of specific car battery packs , race ones with 5kg having 600amps cranking power , but this is something that is on my mind for a long time and I will probably end up testing it so help would be nice so I dont kill my self or the car


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## mvyrmnd (Oct 29, 2011)

You could easily build a pack powerful enough to crank the engine and not destroy itself in the process, but without some sort of charge controller I doubt they would take kindly to being charged from the alternator.

I think at a minimum you'd need a 4S 10P pack.


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## DFiorentino (Oct 29, 2011)

flashflood said:


> Starting a typical car takes 500-1000 amps at 12 volts nominal, sagging to not less than 7V..



It my experience, those numbers are pretty extreme. Maybe more common in larger diesel engine, perhaps. I'd say in the average passenger car, 70A-500A, varying with engine size, displacement, age and technology. Common among residential car shops are 200A capable jump boxes. As for voltage, there are several motors that will "operate" below 9.6V, but the current draw at that point tends to be ridiculously high to be effective.

-DF


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## sunny_nites (Oct 29, 2011)

I did a quick search on Amazon and found the battery in the link below. Looks to have the specs you are after:

http://www.amazon.com/dp/B005730960/?tag=cpf0b6-20

Good luck!!


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## shadowjk (Oct 29, 2011)

People on youtube start their cars with 4 A123 cells. (Obviously they don't leave them connected once car has started)


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## Kestrel (Oct 29, 2011)

A few years ago CPF'er _mdocod_ posted a video here where he jump-starts his dead car after charging it for 2 minutes or so. He used a relatively small number of A123's IIRC.

I think it would be pretty cool to keep a Mag D hotwire in your car and to be able to connect it as needed to cars for jump-starts.


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## BVH (Oct 29, 2011)

As DF mentioned above, 200 Amps and a little more is about what the typical starter motor draws for stock gasoline engined cars. This goes back to my 1980's and 1990's mechanic days and reflects starters in V-8's. In today's 4's and 6's, its significantly less than 200 Amps. The initial "strike" will be somewhat more but only for a micro second.


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## mattheww50 (Oct 29, 2011)

I believe the big hazard in using Li batteries to start a car is the maximum safe discharge current on most of the Li re-chargeable batteries is a small multiple of capacity. I.E. it isn't safe to draw more than about 6-9 amps from a 3ah Li battery. By contrast most Lead Acid cells and NiCd's are capable of provididing a much larger mutlipe. This allow a 50Ah battery to delivery 500 amps for few seconds to start a car. DC resistance of most starter motors is a tiny fraction of 1 ohm, however the current draw falls very rapidly as the motor spins up due to the generation of 'back emf'. The faster the starter motor turns, the less current it draws. Maximum current draw on a DC motor is at zero rpm.

Today's car starters draw a lot less curent than was typical 20 years ago because the typical engine displacement has fallen quite dramatically. It takes a whole lot less energy to turn over a 2 liter 4 cylinder engine than it took to turn over a 5.7 lliter V8. Things like electronic ignition and fuel injection has made most engines start within a second or two.

However there is nothing that prevents you from charging the car battery at 6-9 amps for a few minutes to get enough charge to be able to start the engine. As I pointed out, most engines today start very quickly compared to 20-30 years ago, so you don't need a lot of amp hours in the battery to be able to start the engine these days.


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## DFiorentino (Oct 29, 2011)

mattheww50 said:


> I believe the big hazard in using Li batteries to start a car is the maximum safe discharge current on most of the Li re-chargeable batteries is a small multiple of capacity. I.E. it isn't safe to draw more than about 6-9 amps from a 3ah Li battery.



You're thinking of LiCo chemistry. OP is speaking of IMR LiMn chemistry. Both mammals, but different animals...

-DF


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## alpg88 (Oct 29, 2011)

Art said:


> Imagine a car that uses a 50amp battery , how many , if possible , 18650 IMR cells will it be needed to do the same work?
> And if it is able to start the car , can it be used after that ? Be charged with the car charger etc?
> 
> ,


i don't see why it can't be done, with enough cells, and proper chaging, it sure can be done, tesla roadster runs on almost thousand 18650.


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## VegasF6 (Oct 29, 2011)

mvyrmnd said:


> I've never seen it done with IMR's but there's a company making LiFePO4 dropin replacement packs for cars. Their name escapes me at the moment


Shorai and Turn Tech are probably the two most common. There are some others too. My limited experience is they are aimed more towards small motorcycles and rzrs, ranges, atvs etc.


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## hellokitty[hk] (Oct 29, 2011)

I've actually seen it done with a lipo. If I remember, it was 4s ~3000mah battery rated at 40c.


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## xul (Oct 29, 2011)

Locked rotor current for a '94 Honda Civic starter motor is 400 A and the applied voltage at this point is 4V. Steady state current might be 200A.


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## fivemega (Oct 29, 2011)

*In most of cases when you need a jump start, weak battery provides lots of current but still is not enough to start the engine. So boosting it with 15~20 Amps will be just enogh to start. 4 Serial IMR 26500 will easily do the job.
All mentioned electrical currents may varry widely by ambient temperature. Lead acid battery looses current capability in lower temperature. A cold engine has lot more mechanical resistance to turn over and same starter will needs more current to start the engine compare to when engine is warm.
If an engine needs to spin fast enough for 1 or 2 seconds with voltage of 10 volts or higher, then Start a car with IMR cells is absolutely possible but after starting the engine, IMR cells must be quickly disconnect from car battery to avoid high current charging by alternator.*


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## xul (Oct 29, 2011)

BTW, you can use one of the motor cables as a shunt if you know the wire length and diameter, and therefore the resistance per foot. 
E.g., 3' of awg #2 copper will have a 117 mV across it for 250A through it.


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## vestureofblood (Oct 29, 2011)

If I recall correctly CPF member Mdocod used a pack of Emoli cells to start a car. Pretty sure he made a vid several years back.


EDIT: Here ya go.

http://www.youtube.com/watch?v=PCtE0lP1lcE


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## jasonck08 (Oct 29, 2011)

flashflood said:


> Starting a typical car takes 500-1000 amps at 12 volts nominal, sagging to not less than 7V. If you put four cells in series that would get you 15V nominal at the same current, say 15A. Now multiply by 50 cells to get 750 amps. That's a total of 200 cells. All safety issues aside, it seems impractical. Better to carry a purpose-built spare starter battery in the trunk.



Naw, it doesn't take anywhere near 500-1000A to jumpstart a normal car. Take a look at this video on youtube: http://www.youtube.com/watch?v=qcvmvrmTMMk

Jumpstarted a car with a dead battery with 4x A123 26650's. Those cells can handle pulses of 100C, but not anywhere near 500-1000A.


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## flashflood (Oct 29, 2011)

jasonck08 said:


> Naw, it doesn't take anywhere near 500-1000A to jumpstart a normal car. Take a look at this video on youtube: http://www.youtube.com/watch?v=qcvmvrmTMMk
> 
> Jumpstarted a car with a dead battery with 4x A123 26650's. Those cells can handle pulses of 100C, but not anywhere near 500-1000A.



The video is misleading. The "dead" car battery is still providing most of the power.


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## flashflood (Oct 29, 2011)

vestureofblood said:


> If I recall correctly CPF member Mdocod used a pack of Emoli cells to start a car. Pretty sure he made a vid several years back.
> 
> 
> EDIT: Here ya go.
> ...



Cool -- but notice that it only worked when he waited several minutes. What he's doing in effect is using the car battery as a giant capacitor, and using the Emoli cells to charge it. A few minutes of charge time, providing a few seconds of discharge time, hence ~50x fewer cells than in the computation above. I could see this being quite useful in practice, assuming the car battery isn't so damaged that it can't hold a charge, but it's a different question. The original question was, could you start a car with *only* 18650 cells, and in that case you really would need ~200 cells to get the required ~5000W instantaneous power.


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## Foxx510 (Oct 29, 2011)

Not entirely what the op was talking about, but here are some Li car cranking batteries http://ev-power.com.au/webstore/index.php/12v-lifepo4-batteries/12v-lifepo4-batteries.html


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## mvyrmnd (Oct 29, 2011)

Foxx510 said:


> Not entirely what the op was talking about, but here are some Li car cranking batteries http://ev-power.com.au/webstore/index.php/12v-lifepo4-batteries/12v-lifepo4-batteries.html



That's the ones I was talking about!

Thanks Foxx!


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## Art (Oct 30, 2011)

Well , thanks for all the input.

My idea was that since the IMR cell can handle so much discharge current they would be up to the job.
I always have some 18650 on my car so having a set of just in case would be nice. I would only need to fabricate a holder for 4 cells and try.
Dont think it will work on my daily car because its a diesel , but my track car is a 328i and it seems to start with any kind of battery when everything is ok (fuel pump , spark plugs..) so will try and test with only 4 cells with a not fully dead bat and with a dead on.
8 cells and above it really doesnt interest me , there are a lot of small batteries on sale able to do that properly.


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## flashflood (Oct 30, 2011)

Art said:


> Well , thanks for all the input.
> 
> My idea was that since the IMR cell can handle so much discharge current they would be up to the job.
> I always have some 18650 on my car so having a set of just in case would be nice. I would only need to fabricate a holder for 4 cells and try.
> ...



Just be careful, CPF comrade. Car batteries are insanely powerful and are full of lead and sulfuric acid, and lithium is an extremely reactive alkali metal. You could really get hurt if there's a mismatch in voltage, excessive charge or discharge rates, etc that causes one or the other to blow.


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## jasonck08 (Oct 30, 2011)

flashflood said:


> The video is misleading. The "dead" car battery is still providing most of the power.



Incorrect according to the guy who recorded the video on youtube. In one of his youtube comments he posted this.



Doctorbass said:


> no..﻿ it's not a booster.. The Oem car battery is 11 years old and is pretty dead. it is more like a load than a battery.. so the pack i built is also putting some current to the dead battery and to the starter. I also tried to discunnect the OEM 12V battery ad the little pack work better WITHOUT the car 12V battery.



AFAIK a SLA battery that is in the 11v range in -20C weather is practically useless. The A123 pack was not only slowly charging the dead SLA, but also delivered current to start the starter motor.

Looking online it appears that a honda Civic (for example), uses a 1.4KW starter motor, which is about 120A @ 12v. So I don't believe a 4 cylinder car needs anywhere near the 500-1000A you stated they need. 120A would be an acceptable Pulse current for these A123 26650's.


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## lightliker (Oct 30, 2011)

Art said:


> The current battery im using to start my track car is only 40ah 330AMP cracking power and it starts fine , my idea would be to get something able to do enough power to start the car. It only needs 2 to 4 seconds.
> If I use series of 4 packs of 18650 and imagine that in the best case it would do 30amps 3 pack of 4 cells would have more less 100amps... lets imagine it is enough to start the car what problems could I have with the cell pack?
> Risk of explosion on start? Will it be able to charge with the engine alternator? Or would it have too much power?
> 
> I know this seems stupid , there are a lot of specific car battery packs , race ones with 5kg having 600amps cranking power , but this is something that is on my mind for a long time and I will probably end up testing it so help would be nice so I dont kill my self or the car



How do you recharge all this cells when used one time??
Could take you many many days with only one or two chargers:sick2:


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## Art (Oct 30, 2011)

jasonck08 said:


> Incorrect according to the guy who recorded the video on youtube. In one of his youtube comments he posted this.
> 
> 
> 
> ...



In the specs of my car its also 1.4KW... so 120A is not that much.
Still there is not much interest in using a lot of this cells... if 8 wont do it or a max of 9 in 3 series , then there is no point... maybe only just for the fun lol


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## realista (Dec 17, 2014)

hi all, i am REALLY interested in this thing.
i thought to buy 3 IMR batteries with high discharge rate but then i found this freak samsung battery:
*samsung inr18650-25r*
500mAh
20A max continues discharge
100A max for 1 second
50A max for 5 seconds

It is very powerful, not? a fully charged SLA battery , i read it's about 12,6v. that's prefectly 3 fully 4,2v batteries. If i buy a 3x18650 battery holder and solder to the wires 2 crocodile clips i think which there are lots of probability to start the car engine, because the "dead" SLA battery in 90% of instances it's not really dead but just below 12v and it need a LITTLE HELP.

i searched for other kinds high drain 18650 or 26650 but most of the times they provide "only" 20/30, max 50A. But maybe these are CONTINUES DISCHARGES and also they are able to provide up to 100A for 1second. But after all this *samsung inr18650-25r only cost about 5 EURO, really cheap.*


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## StorminMatt (Dec 17, 2014)

One issue with using IMR batteries for automotive applications is voltage incompatibility. Four IMR batteries in series gives you 16.8V unloaded and freshly charged, or 14.8V nominal - FAR too high for an automotive electrical system. Three IMR in series would give you 12.6V unloaded and freshly charged. When state of charge drops to 75%, you would have 12V even. And that's assuming no load. If you were trying to start the car or run any other significant load, voltage would certainly be lower than 12V. That's why nobody makes IMR automotive batteries. LiFePO4, on the other hand, works FAR better. Four in series makes for 12.8V nominal, or 14.4V fully charged - perfect for a lead acid replacement.


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## realista (Dec 17, 2014)

i understand what you say, but i remember you that a full charged SLA battery is at about 12,6v .... and this is WITHOUT LOAD. 
so.. i don't understand because 3x 4,2v =12,6v batteries are not equal to a SLA one. I think also SLA under load goes below 12,6v. 
About 4x lifepo4 are you sure 14,4v is a SAFE voltage....not too high?

in alternative to all, i found this <--LINK A123 ANR26650M1A 3.2V 2300mAh lifepo4, rated 70A continuous discarge and *PULSE for 10 **sec** at 120A* 
DATA SHEET <-- link
The only 1 problem is that does not exist a 4x26650 battery box container.... and i should biuld one myself . somethink like this but for 26650 
184


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## StorminMatt (Dec 17, 2014)

A fully charged LiFePO4 cell is at 3.6V. Four in series will be 14.4V. This is EXACTLY the same voltage as an automotive electrical system with the engine running and a fully charged battery. And this would overcharge IMR. As for the voltage of a lead acid battery, typically fully charged is around 12.5V and fully discharged is at 11.5V. At 11.5V, each IMR battery in a three cell pack will be at over 3.8V, or around 40-50% charge. That's quite a bit of capacity below that voltage which can't be used. All of this begs me to ask a simple question: why would you want tomuse IMR over LiFePO4 as an automotive battery in the first place? And this doesn't even start to get into the longevity advantages of LiFePO4 vs IMR.


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## inetdog (Dec 17, 2014)

I think the original interest was in a momentary use jump start pack, so the whole issue of alternator charging and long term connection goes sway.
There are commercial Li chemistry batteries for motorcycles and ATVs mainly that are true drop in replacements for FLA. But too expensive unless the weight and size benefits make a big difference to you.

PS: Many of the jump start packs work best by leaving them in parallel with main battery for s few minutes to put s quick shallow charge on it so that both batteries supply starter current together.


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## StorminMatt (Dec 17, 2014)

inetdog said:


> There are commercial Li chemistry batteries for motorcycles and ATVs mainly that are true drop in replacements for FLA. But too expensive unless the weight and size benefits make a big difference to you.



I actually priced some of these batteries sometime back. And they are more reasonable than you might think. Although theybare pricier than FLA, they are actually quite comparable to AGM. And they have more advantages over FLA (or even AGM) than size and weight. They also have a longer cycle life. They won't sulfate. So you don't have to worry about fried batteries on boats and ATVs that aren't used for months in a row. And you'll never have to worry about nasty, corroded connectors.

Also, for applications like off-grid solar and other applications that involve deep cycle use, LiFePO4 can be drawn down to a greater depth of discharge than lead acid (while better maintaining voltage), allowing a smaller LiFePO4 battery to do the work of a much larger lead acid battery.


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## tripplec (Dec 17, 2014)

Already been done. I find it hard to believe though personally. 

"NOCO GENIUS BOOST"

http://www.geniuschargers.com/Boost/


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## Gauss163 (Dec 17, 2014)

*LiPo jump starters are a dime a dozen nowadays*



tripplec said:


> Already been done. I find it hard to believe though personally. "NOCO GENIUS BOOST" http://www.geniuschargers.com/Boost/



It seems that nowadays every Chinese manufacturer is making a version of these RC LiPo's repurposed as Jump Starter Powerbanks. You can find many models on eBay starting for around $50. If you're patient you can win them on auction much cheaper, e.g. I paid $13 for a popular model (vs. $180 for a weaker model from AutoZone). Like most Chinese batteries, their capacities are usually fraudulantly inflated, sometimee highly so. Mine claims to be 180000mAh (67Wh) but my tests yield only 47Wh.


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## wingnutLP (Jan 15, 2015)

*Re: LiPo jump starters are a dime a dozen nowadays*

My track car has a lithium battery in to start it dropped from 9kg top 1kg. 

http://www.racingbatteries.co.uk/in...ing-batteries/product/3-rbf400-racing-battery

an 8kg weight saving for £249 is a lot cheaper than buying fancy carbon fibre parts  

It struggles a bit when it gets close to freezing outside but otherwise is fine.

Jump starting from IMR cells would be cool


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## sickopsycho (Jan 14, 2016)

I realize this post has pretty much gone the way of the dinosaurs... but I've just seen my first booster pack in action and I want to build one now. It was one of these... http://www.autozone.com/test-scan-a...ortable-power-source-jump-starter/533208_0_0/ basically it looked like it could hold about 6 18650s in what must be a serial parallel configuration. That would make sense to get the voltage and amperage required to boost a dead car battery. I agree with a lot of the previous posts, I don't know that this thing would work to start a car without another battery in it- but thats not what its for. Its built to boost a battery whose volatage has dropped below the required amount needed to start the car. In a modern car- a minimum voltage of actually around 9.6V is required while the starter is turning the engine in order to fire the plugs. This is why a lot of times an engine will turn over really slow- but won't fire. The plugs aren't getting enough juice to bridge the gap and therefor without spark, theres no fire. Using one of these packs to simply provide an additional boost of voltage and amperage would seem to do the trick. The one I saw was the one listed above... and the battery in question wouldnt even turn the motor over- once connected, the engine turned over with gusto as if a brand new battery had been installed! I was amazed and want to build my own now. Being able to keep your cell phone charged is a nice side feature. Anyone here have any experience? The only experience I have with these batteries is in my e-cig and I can attest to the fact that they can take some abuse for short periods of time and not fail. Looking forward to hearing back-


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