16V LiFePo4 drag racing battery project

[Doctorbass]

Couples of drag racing guys contacted me about making 16V battery for them after they watched couples of my youtube videos.

I know they already exist.. some made of A123 cells some with RC lifepo4 cells... etc...

For those who already know them, My question is : do you know if there is any LVC protectin inside?. I mean a battery thatc an give 50A per cylinder will need like 4-500A during the start of the engine.. so it must have a contactor or something else? to prevent the battery from overdischarging?

Also.. are these guys use an alternator?.. if so i guess they need to tune it to 18.5V for for cahrging the battery fully?

After some calculations these guys said they would need to power everything in the drag car for around 25 minutes.. for an entire drag racing day... they often dont use any alternator and preffer recahrging the battery with an external charger. Wich is good and easyer for me to build. The entire system including head light, motor fan and fuel pump and ECU require max 50A..



So 50A during 25 minutes is 20Ah.

So building a battery of 23Ah would be the minimum.

23Ah of A123 cells is 10p cells.

To make 16V i would use 5s cells wich is 3.3 x 5 = 16.5V nominal wich is perfect for their needs and probably 18V full cahrge at 3.6V per cell

So a battery made of 5s10p is 50 cells and each cell weight 70g so the entire cells in the battery would weight 3.5kg for 370Wh

The max continuous current woudl be 70A x 10 = 700A and the burst current would be 1430A for 10 sec wich would be able to fry many starter!

So.. for the LVC cut.. i guess that maybe an EV200 tyco contactor combined with a little BMS circuit that control the contactor LVC thru a transistor and 5 shunt to balance the cells would be ok...

Doc

 

[liveforphysics]

Holy overthinking it batman.
20Ah of A123 M1 cells would be heavier than the little lead acid drag racing batteries.

It's a drag car. It needs to operate for 5mins at a time, at the most.

It doesn't need LVC, it would always be better to ruin a battery than botch a run from LVC cutting out.

If it's a fast drag car, I will have no alternator.

We've been using 3 of 4Ah 45-90C nano-tech packs in parallel in a number of different drag cars now from monster high compression big block chevy power to a 1,300hp turbo civic.

That's 12Ah. The voltage drops like half a volt when starting the massive high compression 560ci BBC engine.

The biggest thing you need to figure out is if they use an electrical or mechanical fuel pump. If they run mechanical, then you will likely be fine witha single 4Ah Nano-tech pack (or two in parallel if it's an extremely large high compression engine). If they run an electrical fuel pump, ask what they are running and how many. The 1,300hp civic runs 3 monster fuel pumps that each pull 35-40amps, and ignition setup draws 22amps at max RPM.



Things you do NOT want on a drag car:

BMS- It's just more needless points to fail
Charger- It can be charged in the pits with an RC charger there is plenty of time.
LVC- If the battery were to ever cut-out under power for any reason, it could cost not only the engine, but the drivers life and/or the event.
HVC- Needless complexity.
Fancy connectors - Things that disconnect are another failure point to get ripped off, fall off, or melt.

Things you do want on a drag battery:

Feather light. Use as high of C-rate cells as you can find.
Steel or aluminum straps to mount it that meet the NHRA rules requirement for battery mounting (it's stupid but it's the rules)
0awg cables.
Big nasty bolt-on ring terminals.

 

[Doctorbass]

Holy overthinking it batman.
20Ah of A123 M1 cells would be heavier than the little lead acid drag racing batteries.

It's a drag car. It needs to operate for 5mins at a time, at the most.

It doesn't need LVC, it would always be better to ruin a battery than botch a run from LVC cutting out.

If it's a fast drag car, I will have no alternator.

We've been using 3 of 4Ah 45-90C nano-tech packs in parallel in a number of different drag cars now from monster high compression big block chevy power to a 1,300hp turbo civic.

That's 12Ah. The voltage drops like half a volt when starting the massive high compression 560ci BBC engine.

The biggest thing you need to figure out is if they use an electrical or mechanical fuel pump. If they run mechanical, then you will likely be fine witha single 4Ah Nano-tech pack (or two in parallel if it's an extremely large high compression engine). If they run an electrical fuel pump, ask what they are running and how many. The 1,300hp civic runs 3 monster fuel pumps that each pull 35-40amps, and ignition setup draws 22amps at max RPM.



Things you do NOT want on a drag car:

BMS- It's just more needless points to fail
Charger- It can be charged in the pits with an RC charger there is plenty of time.
LVC- If the battery were to ever cut-out under power for any reason, it could cost not only the engine, but the drivers life and/or the event.
HVC- Needless complexity.
Fancy connectors - Things that disconnect are another failure point to get ripped off, fall off, or melt.

Things you do want on a drag battery:

Feather light. Use as high of C-rate cells as you can find.
Steel or aluminum straps to mount it that meet the NHRA rules requirement for battery mounting (it's stupid but it's the rules)
0awg cables.
Big nasty bolt-on ring terminals.

Big thanks for your advices Luke, I knew you woudl probably coe here and comment about that since you are a big fan of racing stuff

Since people that will use this battery are not the lithium expert, i think that A123 cells would be the best trade off because they are safer.

Using lipo would probably save weight but they are LiPo and they can catch fire if overdischarged or overcharged as you know.. and without any protection, leaving such battery like that in their hand without my presence would garanty to have a fire event and burn the hole car one day or another wich is not goo too.

A123 26650 can deliver 60C and are safe.. this is i think the best trade off for safety and power.

i agree that 20Ah might be too much for the weight, but i must see with these guys if they want to charge the battery between each run or if they want to keep it for the entire day without touching it...

Doc

 

[Red_Liner740]

Race bikes that run total drain system (the stator and windinds are removed) run 4s2p A123 cells and they last them about 30min, enough for a sprint race.

other guys run the 4s2p or even 4s1p as a battery replacement.