Battery

[B Lewis @ PE Engine Management]

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]

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.

[edit]
List updated, thanks TMichaels
[/edit]

[TMichaels]

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]

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]

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]

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]

http://www.ev-power.com.au/-Lithium-...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]

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]

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]

"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