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Old 01-22-2020, 04:52 PM   #421 (permalink)
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You switched from cordless drills to mobile phones and lost me.

If no phones are involved then yes. Your setup should word if I have understood it correctly i.e.

Have charging cradles at home to charge the 16v batteries. And install identical cradles wired in parallel to the lead acid battery. So you bring your batteries and plug them in to your car and off you go.

Should work but I see a tiny problem. As the batteries have a higher voltage than lead acid, they will constantly waste energy over charging your lead acid battery. Swapping the lead acid with capacitors would solve this issue.

Is your intention to go alternatorless or over volt the system so the alternator is effectively disabled.

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Old 01-31-2020, 01:09 PM   #422 (permalink)
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Quote:
Originally Posted by teoman View Post
You switched from cordless drills to mobile phones and lost me.

If no phones are involved then yes. Your setup should word if I have understood it correctly i.e.

Have charging cradles at home to charge the 16v batteries. And install identical cradles wired in parallel to the lead acid battery. So you bring your batteries and plug them in to your car and off you go.

Should work but I see a tiny problem. As the batteries have a higher voltage than lead acid, they will constantly waste energy over charging your lead acid battery. Swapping the lead acid with capacitors would solve this issue.

Is your intention to go alternatorless or over volt the system so the alternator is effectively disabled.
I'll clarify. Using the 18650, high discharge cells commonly found in cordless drills but charging them in the discreet, form factor, 18650 mobile phone powerbank. An Example of which, attached Below.

The Intention is to go alternatorless and recycle the conventional lead acid, as it's 10 years old anyway and won't make it thru another winter.

The car should start without supercapacitors, as it's only a 1 liter geo metro and these 18650 batteries/cells are rated for high discharge, used in high torque drills, VTC5A.

I've used this same setup in an airsoft gun, with 2 of these in series(A 2s, 7.4V) lasting the entire day of play.
So after finding the performance adequate in an environment that places similar demands on these specific 18650s, its with this data point, that stacking the cradles up to make 16V, should not just work the car for a while but last at least a few years.

The only concern is balance charging. 8 cells at a time is pretty good, though preferably it would be all of those in the autostart-4s4p,cradle block, all 16 cells. I could see about connecting the battery charging circuits of the attached,below, if they start drifting from one another?
power bank 8*18650 case $4

Last edited by Thorium-Synfuel; 01-31-2020 at 01:27 PM..
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Old 02-01-2020, 09:03 AM   #423 (permalink)
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I see where you are going, do you have soemthing like an imax charger? Or means of measuring the capacity of each cell. After that you plug the capacities in to a website (jhurgia on youtube recommended it) and it tells you which pack goes in which parallel cluster.

I have a BMS that has a bluetooth interface so you can connect your phone to. Have not been able to test it yet. I also recommend a bms if lots of cells of unknown capacity are involved, especially if you intend on running them from max to min.


Also if you get that box, check its voltages. Some of them over or under read.

8 cells, if each of the required 2 amps and you wanted to usb charge them, you would need a 16A usb port.

In which case I doubt that the charging circuit is up to it. If it charges at 2A the it will take more that 8 hours to charge.
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Old 02-02-2020, 09:07 AM   #424 (permalink)
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The powerbank charger outputs 5V and as the cells get near to charge, stops at 4.1V. So a little low but acceptable for long term longevity.

My airsoft buddy has an iMax charger and you're right, once the lipo-automotive pack proves like it can handle an hour of driving at night. Then adding the tiny bms wires, would keep everything at the same voltage and capacity as the pack ages.

Though right now, before going for it, it's wise to do some cursory maths to determine if it will fulfill the needs of the car.

Do we have any data on Watt-hours of draw a typical small car like the metro draws over an hour journey, with head lights on?

I'm guessing the lights are 20A. Though what is the draw per hour, to provide thousands/millions of sparks?

Strangely not something my search engine skills can uncover.

The best, as ever resource is the founders of the site, looking at his estimate of 530 watts, though conservatively you can read 700 W from the list, under dark, cold and raining conditions.

That's W/V =A. Which in this case is 700/14V = 50 A on rounding. For one hour of night driving in the rain with the hair dryers on throughout. You conservatively need a battery with 50 A.h capacity for an hour of worst case driving. With each 4 in series under a 13 amp load(a draw more than within the continuous run time of Sony VTC5A cells, in fact the higher 3Ah capacity samsung 30Q starts becoming more appealing in this continuous drain role, than the higher cold cranking amp rated, Sony cells in this calculation)

A 4s4p lipo pack, with each cell at the VTC5A, nominal capacity of 2.5A.h. That means with 4 in parallel, the capacity is 10 A.h.(12 A.h with the samsung cells)

So that comes out to be 12 to 15 mins of run time . Not the needed 60 mins of run time.

For complete alternator deletion, a 4s16p pack is needed. Is this accurate?


That thing will be as large as a typical lead acid battery and cost near 150 dollars easily in batteries/cells alone, with 64 cells.

Still, might get away with close to half that size, a 12 parallel pack, instead of the 16, as realistically Ireland doesn't have the assumed monsoon weather. Though good to know 16 would just do and no more.

Anyone recommend a non Iron phosphate, Li-ion recreational vehicle, battery in the 50 Ah range?

On looking on amazon, for "12V lithium" which are all Iron phosphate based, as far as I can tell, this DIY route, actually starts looking pretty decent price wise.

Darin's metro mpg page on alternator optional in his Firefly

Last edited by Thorium-Synfuel; 02-02-2020 at 12:03 PM..
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Old 02-02-2020, 09:38 AM   #425 (permalink)
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From memory... a small gasoline car draws about 6A @ 13V. That is 78W.

Lights are 50W each.

Your cells are 3.6V 2Ah -> 7.2 Wh each. (Probably)


With 1 cell and a boost converter. You can run your car for 7.2Wh/78W = 0.09h = 5 mins(roughly). (Assuming the batt can deliver 24A for 5 minutes, and that the boost converter is %100 efficient)

That is how I do the calculations. Obviously a single cell does not have the amps to run your car.

To run for an hour, you would need 12 cells.
1 hour car consumes 78Wh

78/7.2 = 10.8 cells.

But you want something divisible by 4 in order not to need a boost or buck converter. So 12 cells for 1 hour and no lights or blower or radio.

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Old 02-02-2020, 09:48 AM   #426 (permalink)
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You can get more light output with HID’s, 35W and LED’s draw a bit less with a bit less light output.
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Old 02-02-2020, 11:06 AM   #427 (permalink)
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Quote:
Originally Posted by teoman View Post
From memory... a small gasoline car draws about 6A @ 13V. That is 78W.

Lights are 50W each.

Your cells are 3.6V 2Ah -> 7.2 Wh each. (Probably)


With 1 cell and a boost converter. You can run your car for 7.2Wh/78W = 0.09h = 5 mins(roughly). (Assuming the batt can deliver 24A for 5 minutes, and that the boost converter is %100 efficient)

That is how I do the calculations. Obviously a single cell does not have the amps to run your car.

To run for an hour, you would need 12 cells.
1 hour car consumes 78Wh

78/7.2 = 10.8 cells.

But you want something divisible by 4 in order not to need a boost or buck converter. So 12 cells for 1 hour and no lights or blower or radio.
That's interesting our estimates came out similar, though why do you assume a buck-boost converter when 4 in seriesthe (4s) in the 4s4p, gives 14.8V easy. (Really it is 16.4V when fully charged, though like lead acid, the nominal voltage is given, ~12V or 14V for lithium )

Can you check my added maths above, in my last post, as I edited the post before seeing you had just replied.

It's a strange thing that 14 V li-ion batteries for RV usage, aren't commonplace, can't seem to find them to compare prices with, while sure it is a little more volatile of chemistry than the lithium iron phosphate that everyone is selling in the RV role, but at exorbitant prices for a 50 A.h battery...but we have the former chemistry, in our laptops and they run just fine. Don't discharge all the way(iron phosphate's advantage) and longevity is close enough between Li-ion and Lithium iron phosphate, to not really matter. Especially in this role.
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Old 02-02-2020, 11:51 AM   #428 (permalink)
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Buck or boost converter assumption is to exactly match the desired voltages...
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Old 02-02-2020, 12:08 PM   #429 (permalink)
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Quote:
Originally Posted by teoman View Post
Buck or boost converter assumption is to exactly match the desired voltages...

Is this actually required?

Interesting question, you don't hear often, what voltage is too high for these old non-CPU heavy, cars?

The 4 in series pack will effectively be dead at 12 V. (3V each) it's nominally 14.8V(3.7V each) and when charged, at 16.4 V(4.1 V each)
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Old 02-02-2020, 12:55 PM   #430 (permalink)
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Oh dear,

If you have a single 3.6 or 3.7 V cell then yes, it is mandatory. If not i.e. you have a 4s configuration, I do not think so.

I do not know the exact voltage at which the electronics will barf out the magic smoke. I only have some unreliable bits of information.

At the auto industrial zone a guy one sait you ar good up to 16V.

Some racing guys run a higher voltage battery to speed up the fuel pump and get faster injector response.



+ on a VW forum a guy was having battery problems. Turned out to be that the charging circuit hat failed and was pumping out 22V. The car was acting funny but did not suffer major damage.

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