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Aragorn
10-21-2007, 02:27 AM
Tell me that can i battery other than lead acid battery which is more compact and light weight?
Can i use laptop battery?

Aragorn
10-21-2007, 02:27 AM
Tell me that can i battery other than lead acid battery which is more compact and light weight?
Can i use laptop battery?

ad
10-21-2007, 03:37 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Aragorn:
Tell me that can i battery other than lead acid battery which is more compact and light weight?
Can i use laptop battery? </div></BLOCKQUOTE>

Two AA's should do it.

Aragorn
10-21-2007, 06:46 AM
wat is dis "two AA`s"?
can you please explain in detail

Brian S
10-21-2007, 02:47 PM
Some things to think about:

What voltage does your ECU require to run?
What voltage is a laptop battery?
How much current does your starter draw?
How much current can a laptop battery supply?
How much capacity do you need for your car to run through endurance, including at least 2 starts (1 for each driver)

The battery on our car is 12V 14Ah, and can source 500 amps for 5 seconds, the battery from my laptop is 11.4V 48000mAh.

Aragorn
10-23-2007, 01:12 PM
I think wat matter mainly for battery is how much is ur starter current? I don`t know dis for my engine. we are using HONDA CBR 600. Could u plz tell that if i use a lithum battery it would be compatible for it or not, in respect of current and energy it can delivered.
Aragon

Brian S
10-23-2007, 04:11 PM
I'm all for helping people out, but there is a difference between helping and doing it for you. This is a engineering design competition, so do some engineering.

You are asking the right questions, but now you need to find the answers, and not by posting them here. This forum is more for discussion than 'tell me what to do' Get some data, some up with a conclusion, then post the data and your ideas to get other people's input.

A starting place for this information is the manual and/or data sheet for the items in question. From personal experience I know that the starter current can be hard to find, but you can get an idea of how big it is by looking at some of the other components in the starter circuit for the stock bike, or if you have one and the right meter you can measure it.

VFR750R
10-23-2007, 05:17 PM
you could buy some inexpensive fuses of various sizes and try them until you find the smallest one that doesn't blow...there's your starter current +- a resonable percentage of error. I'd imagine the factory fuse box has a starter fuse, the starter probably pulls 70-80% of that?

Scott Borg
10-28-2007, 02:59 PM
FYI, Most OEM setups don't use a fuse between the battery and the starter. As mentioned by others, you should be able to get an idea of the current requirement from looking at the size of the wire. If you're lucky, your starter relay might be labeled an amperage rating.

You can also take some measurements using a clamp-on ammeter from Sears, which is a very handy tool to have around. I think mine cost less than $100. Make sure you get one that can measure DC amps, the cheaper ones measure AC amps only.

-s-

TMichaels
10-31-2007, 01:14 PM
The current startermotors of four cylinder motorcycle engines require between 80 and 100 Amps depending on the temperature of the engine. 10mm² wires did the job well in our last car.

B Lewis @ PE Engine Management
10-31-2007, 10:12 PM
Just something to mention while you guys are on the topic of batteries and starters....it's very important to keep the starter wires as short as possible and at least as big as the stock bike wiring. Also, don't make the mistake of removing the starter solenoid. I have personnaly seen just the addition of the solenoid and subsequent reduction in wire between the battery and starter increase the cranking speed by about 125 RPM on the same battery. During a re-start for the endurance, this may be the difference between getting it started and not.

screwdriver
11-24-2007, 05:35 AM
Here's a few tips on that matter:
<UL TYPE=SQUARE>
<LI> If a component is faulty, you've had it. Check if everything works before you install it. (Be on the lookout for factory recalls for the stock parts, you use)
<LI> Make shure you get the right current-regulator for you battery type (e.g LiPo packs need special regulators; gel-batteries may require special regulators, but will not be harmed by regular ones).
<LI> Make shure your alternator can provide enough power to supply all the electrics on board and charge the battery.
<LI> Your battery voltage should under no circumstances drop while the engine is running, if it does, take your electrical systems back to the drawing board. (Exceptions are of course, when you turn stuff on and off)
<LI> If possible, build an experimental cable-harness on a table to be able to draw exact conclusions on power consumption before integrating into the car.
<LI> When using semi-conductors, ie Power-MOSFETs to operate your consumers, make sure, they are nice and cool. If not they'll just turn everything on.
<LI> Don't solder outside of cases
<LI> Use proper connectors (no soldering contacts, crimping-contacts is what you want & make sure they are at least splash-proof)
[/list]

Faults along these lines cut our effective testing time down significantly before the German event. A current regulator from a faulty batch lead to our DNF in the Endurance four laps before finishing in the end.


List updated, thanks TMichaels

TMichaels
11-25-2007, 03:34 AM
I disagree in two points. The first: Your battery voltage should under no circumstances drop while the engine is running, if it does, take your electrical systems back to the drawing board.

The voltage does vary with the RPM and therefore it may drop. It may also drop, if a bigger consumer starts its work like a big radiator fan, because the inner resistance of the battery and generator remain the same, but the current rises-&gt;lower voltage.

The second: Make sure you get the right current-regulator for you battery type (e.g gel-battery or LiPo packs need special regulators).

Gel-batteries do not need special voltage(!) regulators.

Another point, to be added to your list:
Use sealed connectors!

screwdriver
11-25-2007, 06:38 AM
Thanks for the hints.

What I meant by that dropping voltage is, if you can observe a trend. We tried a different Regulator and we could observe the voltage dropping over the course of a test-stint. Starting at something like 13V with a fresh charge in the battery, it dropped to somewhere under 11V at the end of a stint. It was obvious that the regulator wasn't suited for our application.

Rickertsen2
12-26-2007, 11:24 AM
If you want to know the starting current, use a current shunt to measure it. Its a meter that uses a very low resistance calibrated mteal plate that you put in series with the load. It measures the voltage drop across the plate. They are not expensive.

Chuckster
01-02-2008, 06:25 AM
I believe the original question was:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">battery other than lead acid battery which is more compact and light weight? </div></BLOCKQUOTE>


NiMH, NiCad are possible alternatives. The other posts thus far on starter and voltage requirements should help you proceed with an evaluation.

Basically, one must make sure that the internal impedance (resistance) of the battery or assembly of battery cells is low enough to allow large starter currents to be drawn without undue voltage drop. Vdrop=IR where R is internal resistance and I is the starter current.

IMHO, it is pretty hard to beat sealed lead acid in terms of cost vs. performance-but since you are looking to pare every unnecessary gram off of the vehicle; this is a credible design exercise.

BryanH
02-18-2008, 07:24 PM
http://www.ev-power.com.au/-Lithium-Ion-Batteries-for-Electric-.html

The nearly flat discharge curve of a Li-On means that a 6ah Li-On is as useful as a 12Ah PB battery. I would build up a 16V version for fsae.
Cheers

Frank
02-22-2008, 07:39 PM
I would strongly disagree.

The cold cranking amps /unit weight is what you need, and lead acid batteries are hard to beat.

Most motorcycle lead acid batteries, including the odysee are AGM or absorbant/advanced glass mat lead acid batteries.

BryanH
02-25-2008, 04:57 PM
Ancient technology Frank.
I can cold start an auto Getz easily with 2 Flightpower Lithium Polymer 2.5Ah in parallel, (Max burst current of 140A,constant 70A)
Weight? 384grams! Actual current draw was 132A
If your 600cc 4cyl drew 50A on crank,those same batteries would crank it at constant rpm for over 5 minutes because at least 90% of the 5Ah is supplied before the full load voltage drops below 9V.

LiPo cells are 4.2V per cell, but are rated under load at 3.7V . They have a reduced life if discharged below 3V and will explode if charged at &gt;4.25V so voltage management needs to be incorporated into the vehicle, but the technology to use LiPo is available.

Frank
03-07-2008, 11:23 PM
"I can cold start an auto Getz easily with 2 Flightpower Lithium Polymer 2.5Ah in parallel"

"those same batteries would crank it at constant rpm for over 5 minutes"

got a video of either of these claims?

I'd be gobsmacked if two of those batteries could achieve both feats (assuming spark plugs in the engine)

IMO 5Ah at 7.4V for SAE isn't much power, I'd reckon you'd need 1kg of these in a 4Cyl. How much is 1kg of them? AUS1000 US900?

OK, its better than equivilent power from a AGM battery that weighs 3kg and costs $95

JaredC
04-01-2008, 06:49 AM
I'd have to check the specifics here Frank, but off the top of my head the LiPo we acquired last year was a 5Ah 14.8V. It weighed in around 400-500g, around $300AUD shipped.

I don't really know where those 5Ah/7.4V figures came from, but they're not correct. I think you'll find the packs Bryan is talking about are (and I'll take a stab at the numbers here) 4S2P. That's 4 cells in series and 2 lots of them in parallel, which gives 14.8V under load and a total capacity of 2.5Ah. Then, if you take 2 of those packs and put them in parallel, you stay at 14.8V but now have 5Ah of capacity.

On paper, the max currents (ours was 20C=100A max, higher pulse/burst) could easily start an FSAE car and based on the assumptions Bryan has made, (5Ah, 50A, 90% available capacity), I get a cranking time of 324 seconds.

We tried to get a lithium battery going last year, but ultimately, we weren't confident enough with the charging/balancing circuits so we kept it off the car. It can and does work though. Did you see UWAM's lithium battery?

Lithium batteries aren't for everyone though - you'll need to have an elec eng develop a charging/balancing/monitoring system and babysit it, but for under $200 you can lose 2.5kgs and have something nifty to talk about at design.

Oh, and there is also the minor detail of the pretty violent explosions if you get it wrong.

Kirby
04-02-2008, 02:10 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JaredC:
Oh, and there is also the minor detail of the pretty violent explosions if you get it wrong. </div></BLOCKQUOTE>

Unless you use the LiFePo4 batteries linked to by Bryan. They are more stable...trade off in weight/capacity tho.

http://www.youtube.com/watch?v=A9ayuFBDrSg

JaredC
04-02-2008, 06:39 PM
Not sure about the current draw of those ones. IMO you'd want 20C on a 5Ah to be safe.