Batteries

[BMH]

Hello everyone,

I am currently looking at batteries for our next car. We are using a R6 engine with a PE ECU. The battery on our last car was around 11 lbs which is excessive in my opinion. So I am looking for something around 4-6 lbs. I am not really sure about how to determine what requirements we need in a battery. Could someone offer some tips on determining what your requirements are for a battery?

I would like to go with the YUASA YTZ7S battery due to its 4.6 lb weight (Specs: Capacity 6AH, CCA 130), however, I want to make sure that it is suitable for our car.

Thanks in advance for your (helpful) comments.

[mrrc]

i would strongly recommend getting a battery of the same amp-hour rating that the r6 motorcycle had. i say this because the rectifier and starter motor will be somewhat matched to that size of battery. (by size i mean Ah rating)

If you go smaller, try to have your team watch the voltage level closely, as the battery voltage level will affect how the car starts. we used the PE ECU and you can compensate for the battery voltage, but that takes extra time to dial in. if the battery is low on juice, the spark plugs won't work normally and you might end up getting a residue on the spark plugs, they can be cleaned to a questionable extent, but we don't like using plugs after they have been exposed to that.

If you are responsible for the electrical functionality of the race car you will probably hate yourself if you run out of juice due to excessive starting/stalling while testing, as this may prompt you to take the plugs out and change/clean them, as well as recharge the battery using a 1-2A motorcycle charger.

6AH is pretty low, if you have the money and testing time it might be worth the weight savings but your main challenge will be keeping that battery charged.

[Mumpitz]

Do a little energy calculation, now put your hand on the toasty rectifier/regulator after a hard run, and think about depending on the charging system to do MORE work.
That being said I think there are lighter batteries out there.
hint (mower batteries)

[TMichaels]

A lot of teams at FSG last year and this year have switched to 4,6Ah LiFePo-Batteries weighing around 600g, delivering more current (~200A) during cranking.
See a comparison between lead acid and LiFePo motorcycle batteries here:
http: / /shop. strato.de /WebRoot/Store13 /Shops/61333079/ MediaGallery/Lastdiagramm-A123vsPB_700.gif

4,6Ah is usually enough as the cyclic efficiency of LiFePos is much better than lead acid. Some teams run with 2,3Ah at comp, weighing 300g.
The price is around 150,00 Euros => 210,00$
LiFePos do not require any changes on your rectifier/voltage regulator setup.

Regards,

Tobias

[Hub]

We use the stock battery for our engine (Hornet 2008) and it's a YTZ7S. During the first tests and event our engine never work fine at idle so after a lot of re-start our battery run low but it's natural. After a better map tuning we never had problem to start the engine. We always start on the internal battery and never charge it during comp, we only control the voltage.

But for cbr engine the battery is bigger. Probably due to a higher compression Ratio. Check if it's the same for r6.

[Demon Of Speed]

If you have the money I recommend looking at Braille's selection of Lithium batteries.

[EHog]

Braille B106 is what we have run for years. Works great, and very affordable for a 6lb battery.

[TMichaels]

The price of the Braille Lithium batteries is ridiculous.
I'm still waiting for my post to be approved. You can get LiFePos with 4.6Ah for around 150 Euros / 210 USD. You don't have to change anything on your rectifier / voltage regulator setup and they weigh about 600gr.
A lot of the teams at FSG2009 and 2010 were using them already.
There is a webshop selling them in Germany especially for motorcycle racing teams, Formula Student and people who just want to get rid of the lead acid battery weight. But I don't know if they ship outside Germany.

EDIT: My post finally showed up above. Just remove the spaces in the link address to see the diagramm.

Regards,

Tobias

[RANeff]

Where are you finding LiFePo's for $200?

I looked at some last year that were a (crazy) 800 USD. We went with a lithium battery that is 5 lbs for ~$240. Starts the engine great, and will crank it for quite a while if you have engine starting troubles.

[TMichaels]

Hi,
it is a german shop, but Google's translation does the job at least well enough to get the basic information:
http://translate.google.de/tra...s/4s2p_A123_Block_V2 (http://translate.google.de/translate?js=n&prev=_t&hl=de&ie=UTF-8&layout=2&eotf=1&sl=de&tl=en&u=http://shop.strato.de/epages/61333079.sf/de_DE/%3FObjectPath%3D/Shops/61333079/Products/4s2p_A123_Block_V2)

They work pretty well.

Regards,

Tobias

[wagemd]

We've been using the Odyssey PC310 for a few years now and its done better than any other lead acid we've used. They are a bit pricy (~150) but they are fully sealed and gel based.

That 1 lb Braille looks extremely tempting though...

[ucar]

The batteries recommeded by Tobias are used in aeromodelism, so you will probably find them in many dedicated shops.

We are using them this year, as they suppose a great weight saving compared to lead batteries.

A plus of LiFePo batteries against standard LiPo or Li-Ion batteries is that they don't become dangerous when they fully discharge.

[DMuusers]

+1 to Tobias.

We've been using LiFePo's since 2009 (at least). Great batteries and they're incredibly light. I recommend them to any team.

[Macros]

We use A123 cells found in Dewalt 36v batteries in a 4s4p arrangement. Current weight is around 1.5kg.

[Nicky]

I know that this post has been closed since a year. Just wanted to get your opinion on these batteries. We tested them in by placing them only in discharge mode (High amperage diode(250Amp)). Thus utilised only in start-up.

They were balanced before use. But they started puffing up. Having looked at the videos of these kabooming on Youtube http://fsae.com/groupee_common/emoticons/icon_eek.gif , we switched to the faithful Lead Acids at the event.

I read teams using 6Ah lithiums, some even 3Ah(with a jump starting battery).

http://www.hobbyking.com/hobby...5_50C_Lipo_Pack.html (http://www.hobbyking.com/hobbyking/store/__11940__Turnigy_nano_tech_6000mah_4S_25_50C_Lipo_ Pack.html)

http://www.hobbyking.com/hobby....asp?idProduct=14074 (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14074)

These aren't as expensive as the Braille's or the others(I'm not advertising for these). This is what we procured cos I figured we could do some cheap testing with these before investing in something more expensive. Haven't been able to figure out why they puffed up. From what I know, lithium's can take quite a beating while discharging, but charging is where they're ultra sensitive(which we didn't do onboardhttp://fsae.com/groupee_common/emoticons/icon_mad.gif). They were like grenades who's pins were removed waiting to go sky high.

How long do teams spend in making their own BMS? Is it better to get them off shelf than spend time on them? Have teams had lithiums puffing up? http://fsae.com/groupee_common/emoticons/icon_confused.gif Any info on the above would be helpful.

[BMH]

It looks like the batteries you linked to are LiPo batteries which from my understanding, are more prone to exploding compared to LiFePo4 batteries. If you are still planning on building your own battery pack, I would get the LiFePo4 A123 cells that come in some of the Dewalt drill batteries. If you search online, you can find out which Dewalt battery pack to get.

We were going to pursue building our own battery pack, however, I think we are just going to purchase a LiFePo4 battery either from Shorai or Ballistic. Prices for either are between $100-150 depending on size.

[TMichaels]

How the cells behave during discharge and charege depends mainly on their chemistry and their construction.

There is no general rule like: "You can do to them whatever you want during discharge, but have to be careful while charging".

Additionally make sure that the used cells are specified to source the needed currents, otherwise they will keep puffing, even if a safe cell-chemistry is used.
The first pack which you have linked is specified for 25C at 6000mAh capacity. That means you may draw 150A from them. The burst rating is 300A without defining the burst length, could be ms.
Therefore I suggest to stick with the continous rating which is at least too low to drive a 4-cylinder starter motor for some seconds (When I did measurements at an Suzuki GSX-R600 K4 it needed between 150A and 250A). It may work somehow, but you will quickly destroy the cell.
The second pack that you linked meets the requirement. However, for this price I would assume good quality control. The given values could have been taken in the lab and the real cells usually differ from that values, especially in this price range.

Go with LiFePO4-based cells from a well known manufacturer like A123. You would not need to change anything in your car's wiring harness or generator. Just plug it in instead of the lead acid battery used before (assuming that you buy a pack with the same voltage level). There is also no BMS needed in this application (for LiFePO4-based cells).

I strongly suggest to not buy any lithium-based batteries from shady sources just for saving some money. Your health is worth the extra money spent for high-quality cells.

Regards,

Tobias

[Nicky]

Thank you BMH and Tobias. Makes more sense to go for the A123 batteries than buy from an RC dealer.

PS: The burst rating for these is 10sec. Cheers! http://fsae.com/groupee_common/emoticons/icon_smile.gif

[ZAMR]

I ditto what Tobias said about going with A123.

Sometimes it's not enough to specify the battery chemistry to know how the battery will operate. LiFePO4 is a very low power cathode, relatively speaking, for a Li-ion battery. Cathode particle size has a lot to do with power density and safety, and you'll notice A123 has a patented nanoscale material. Other manufacturers may have slightly larger (or much larger) particle sizes and extra care must be taken with them (also they can't charge or discharge as rapidly, so extra amps get turned into heat and... you know).

LiFePO4 is a bad material for this application, performance-wise, but it is the only safe one, and only if it comes in nano sizes.

[TMichaels]

Getting very low particle sizes actually was the key to make LiFePO4 usable/competitive for real world applications.

I would not say that it is a bad material, it just has to be treated different and if a slightly lower energy density is accepted, which is acceptable for the added safety in my opinion, these are quite good cells.

Additionally, talking about FSE, you save some BMS complexity and some accumulator container weight using LiFePO4 cells which compensates for the higher weight. Having seen some other cell chemistries burning, I personally would always go for LiFePO4, to be honest.

Regards,

Tobias

[ZAMR]

Tobias,

I suppose I withdraw my statement about it being "bad." I meant bad relative to other chemistries in the Li-ion family like those based on NMC or Mn-Ni, but only in terms of performance. Safety is of course of utmost importance so iron-phosphate is good for fsae.

Theoretically you should have much better mass properties using one of the alternative chemistries (higher gravimetric and volumetric energy density means less weight, more packaging and far less rotational inertia). But that would require an expert/professional BMS. I think what you said about safety is spot-on.

Since I am a battery chemistry guy, and I know very little about BMS design, and even less about FSE teams, how many teams do you estimate run with LiFePO4? How many run alternatives?

Thanks,

[Thrainer]

It's interesting to see Modellbau Fuchs offering these LiFe packs especially for bikes/FSAE. Our team was in contact with him in January 2008 and he didn't see a market for such packs. We then got battery packs from Akkuservice Untermain (also with A123 cells), which could offer welded taps with more cross section (for high currents).

In 2008 and 2009, we were using 4s2p of these for our GSXR600 powered cars without any problems. We used 4s1p (only 2.3 Ah, 280 g) on the engine test bench and measured 50-60 A during cranking (ignition disconnected), while the cell voltage of the charged pack dropped to 2.5 V.
I was also using the same LiFe packs in my 125 ccm scooter for three years.

ZAMR, our electric cars use LiPo cells with >160 Wh/kg. Lots of other teams were also using LiPo in the last two years.

Regards
Thomas
AMZ - ETH Zurich

[Brian Barnhill]

For what it's worth, these are the batteries WPI has been using for the past couple years (the 5.0Ah version.) I also use them on a couple A-mod cars and on my Ducat 748 and have never had any issues with them. Car started great during the driver change at the endurance for WPI last year too. At $125 the price isn't too bad either and they come in ~1.9 lbs

http://www.turntechbattery.com...20Battery/Order.html (http://www.turntechbattery.com/TurnTech%20Battery/Order.html)

[TMichaels]

I have mentioned it several times and will do it again:
Lithium-Polymer or LiPo refers to a type of cell construction, nothing more. It only tells that the electrolyte is not liquid, it does not say anything about the used electrode materials.
For example LiFePO4 based cells may also be built as LiPo-cells.
BTW: The wikipedia articles about this also do not tell the whole story about LiPo-cells.

With respect to batteries and their energy density:
It is always important to refer to the system energy density, not the cell energy density, especially at FSE with the specific requirements for cell chemistries which are not LiFePO4.
The lower requirements for the interstack barriers and the complexity of the BMS may compensate for the lower cell energy density of LiFePO4 based cells.
I have never done the math, but I am sure that it makes a difference to look at the system energy density instead of the cell energy density.

Regards,

Tobias

[theTTshark]

Does anyone know if the Braille Li batteries need all of the protection or are they LiFePO4s?

[Dunk Mckay]

Hey all, from what I've read above LiPo may not be the way to go. We've used LiFePo4 with a Yammy R6 for a couple of years, but our packs have been through the wars and have now been deemed unfit for use.

We've been kindly offered some LiPo's from an RC company and after some investigation and discussion with their tech guys we're looking at one of these: http://www.overlander.co.uk/li...-30c-supersport.html (http://www.overlander.co.uk/lipo-batteries-6100mah-4s-14-8v-30c-supersport.html)

Unfortunately no-one on our team has got much experience with the electronics side of things (very high turn over team), so I'm turning to everyone here for some advice. Would this sort of thing work plug and play? The voltage may be a little high (13.5V would be better I believe), so that may need some regulating, but we're a little clueless on that front I'm ashamed to say. Anything else that would change using these escapes us completely, so we'd appreciate some advice or a push (preferable a big fat shove) in the right direction.

[jlangholzj]

Originally posted by Dunk Mckay:
Hey all, from what I've read above LiPo may not be the way to go. We've used LiFePo4 with a Yammy R6 for a couple of years, but our packs have been through the wars and have now been deemed unfit for use.

We've been kindly offered some LiPo's from an RC company and after some investigation and discussion with their tech guys we're looking at one of these: http://www.overlander.co.uk/li...-30c-supersport.html (http://www.overlander.co.uk/lipo-batteries-6100mah-4s-14-8v-30c-supersport.html)

Unfortunately no-one on our team has got much experience with the electronics side of things (very high turn over team), so I'm turning to everyone here for some advice. Would this sort of thing work plug and play? The voltage may be a little high (13.5V would be better I believe), so that may need some regulating, but we're a little clueless on that front I'm ashamed to say. Anything else that would change using these escapes us completely, so we'd appreciate some advice or a push (preferable a big fat shove) in the right direction.

Dunk, you're gonna need a few of those suckers to provide the cranking amps you need to get the Rr running. The 6100mAh derives from the fact that you've got 6.1A of current available to you at the rated voltage for an hour.

Also due to the rather...er....explosive nature of LiPo's you'll need some circuitry to protect them and you for that matter from exploding. This includes the charging circuitry as well as some monitoring circuitry.

Outside of that, I'm afraid I'm rather dumb on the subject. Out of curiosity, why change from the LiFePo? We run a 12-cell from ballistic and they've been working great for us over the last few years.

[MCoach]

Dunk, this thread may be over a year old since the last post, but I'll play nice. http://fsae.com/groupee_common/emoticons/icon_smile.gif

With it being a lithium polymer battery and not a LiFe-Po, it becomes a lot more volatile... they run the risk of bursting in the flames if they are shorted or punctured. Thermal runaway is not a pretty way to go out for these guys. They even run the risk of just blowing up during normal operation with nothing more than maybe a hint of smoke. They energy density may be higher, but I don't believe it is worth the risk. Examples of this can be seen in airline safety videos about the dangers of laptops on board and in airports:

Airport Safet Video on lipo batteries (http://www.youtube.com/watch?v=vS6KA_Si-m8)

The RC guys are also warn about these cells:
http://www.youtube.com/watch?v=MBmnP6YEBKU

And a few examples of what happens when they do go (with various degrees of stupidity) :

Puncturing a lipo (PG-13) (http://www.youtube.com/watch?v=tatq8KcaGY0) (Pg-13)


Overcharging a lipo (http://www.youtube.com/watch?v=ixIOEPnsgbI)

[short circuit] (less dramatic than it can be) (http://www.youtube.com/watch?v=u_okpawae2E)


and to link the warning listed at the bottom of the page you linked:

lipo safety warning (http://www.overlander.co.uk/fullymax_warning_sheet_li_poly.pdf)


So, to restate Tobias, I would not use anything other than a LiFe-Po with the current chemistry of cells available.
Background: I did some work for a start up company on battery pack build up, wiring, cell selection, test driving, chemistry and safety documentation, and data logging.
To give a push in the right direction I'll give a bit more information of what to look for.


Batteries for small applications such as these, without modifications needed to the electrical system should meet these requirements:

--12.5 - 14.8V battery pack cell voltage. This way it will be able to be charged by the stock charging system

--Ah rating will vary depending on your electrical load (anything drawing power) and will vary from 2.3Ah for a very lightly loaded system with a high reliability starting system to 14Ah for a race fuel only (100 octane/E85/100+), high compression, low reliability starting system, high electrical draw components, and a high resistance pathway.

--Look for a high continuous C rating. This takes the capacity of the battery, multiplies it by the C value and gives you the rate that it can be discharged at safely. So for the battery you linked, it has a continuous rate of 30C. 6.1Ah X 30 = 183A that can be used safely. The burst duration is also important, especially for starting. Same here, 50C is listed. 6.1Ah X 50 = 305A that can be used safely for only the duration listed. The cell will also have a charging C value, which dictates how fast you can charge it as well.

--Packaging is a smaller concern, because of how small the overall package typically is. These are not like typical car batteries so they can pretty much be put where ever they fit.

--Buying a pack with balance ports and a balance charger (or can get one seperately) is recommended as they will help prolong the life of the cells. Make sure to balance the pack regularly to lower the risk of under-volting one of the cells and losing it permanatly. Make sure to match the chemistry as well, as using the improper automatic chargers will kill them.
Lead acid chargers and jump starters can be used on LiFe-Po packs, but don't don't exceed the charging rates of the cells.

--Under-volting the cells is one of the best ways to kill them quickly.

TL;DR: Don't buy lipo batteries for FSAE.

Hope I listed enough information to satisfy. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Crispy]

2013 FSAE Rules:
IC4.4.4 Battery packs based on Lithium Chemistry other than Lithium Iron Phosphate (LiFePO4):
a. must be commercially manufactured items
b. must have over voltage, under voltage, short circuit and over temperature cell protection
c. must be separated from the driver by a firewall


I could be interpreting this wrong, but I don't believe you are allowed to make your own LiPo batteries for combustion cars.

[TMichaels]

Chris,
you are right. You are not allowed to build your own LiPo packs from single cells.