Battery

M

Mike Munson

New member
This may have been covered before but I couldn't find it in the archives.
I will be running without an alternator and have an Electromotive, fuel pump and Cool suit(in the south).
Would an Optima blue top (regular and deep cycle) work or should I go with a deep cycle only?
TIA
 
I think you need to measure the current draw and do some math.

IMO, though, I hate running a total loss race car that can only do one session. Forget to charge it just once and you get to use a tow rope. Ask me how I know this.....

I'd also bet that there could be more power gained by having a steady fuel pressure and ignition voltage than lost driving a little bitty alternator.

YMMV
 
Had a switch for the alternator on my last race car, and it made no difference in times with it on or off. Gm had some back in the 80's that were no bigger than a oil filter.
 
I think the biggest improvement is putting a bigger pulley on the alternator. It might not fully charge at idle but thats ok.

With a small alternator you can then use a smaller battery. Cheapest small battery that you can pick up anywhere, lawn tractor battery. If needed can find a replacement anywhere. They are sold in 3 diffrent ratings all the same size.

Summit sells big alluminum alternator pulleys, of course it might not fit and will have to be modified.
 
Or, if you need to add balast, run 2 batteries and no alternator. That's what I did in the Lotus.

Ran the Miata last year with a yellow top - had electromotive, data acquisition and cameras running off it no problem. Hit it with the charger after every other session. Plan to do the same this year.
 
Mike we dont run an alt. and run a 700amp batt (no name brand 26lbs ) no problems just charge between sessions. You shoud get a session with no problems and will be able to get about 3-4 starts befor it runs out of juice. If we make it to Nashville come by and look at our setup, we also have a remote so we can jumper off to save on the first start.
We are looking for more weight loss so far the BRAILLE batteries look good the B2317 should work and only weighs 17lbs. With the new weight reductions we are scrambling to find 50lbs to take off so any weight you can pull off front of car cannot be bad.
 
I've run a Optima Red Top for several years with all you mention plus electronic dash and 2 fuel pumps. I go all weekend with out charging or worring about multi starts. I've even run one or two sessions without charging from the previous weekend whe i forgot to but don't recomend it.
 
Due to the length of our races I never run a charging system. Horsepower to charge aside, just spinning the alternator & belts & tensioners at 7K+ consumes a couple of horsepower. In H Prod, that's too significant to ignore. Plus, with the alternator & all the brackets etc, you save 10 to 12 lbs off the front of the car.

There is a second side to this coin however... reduced voltage in the system. Without a charging system the voltage is going to be about 12.0V (and dropping). With a charging system, you're about 14.0V+. This will affect the efficiency of the ignition system. It will show-up as being harder to start and being "mixture sensitive".

With marginal voltage, you make peak power at a given A/F ratio, but if you go a couple of tenths rich, performance begins to fall off. With ample voltage, you can be off by a full point rich and hardly notice it. Real handy with IR sidedrafts.

The solution? Get a "Total Discharge Controller". We use the Race Energy Total discharge controler. (http://www.raceenergy.net) You can set the voltage to anything you want (up to about 16.5 or 17 volts) and it holds that voltage until the battery is totally dead, at which time all kinds of buzzers go off.

I have no connection with these guys, but I'm a big fan.
 
I've also seen audio guys in the past use an 8V and a 6V battery to get 14V off the charger. they did that due to the same types of reasons- some amplifiers have unregulated power supplies and make more power at 14V than they do at 12V.
something else to consider, but it seems simpler to use the stabilizer thingy mentioned above vs. doing the dual battery and having to make a custom 16V charger to work on it.
 
Here is some information on the HP used by the alternator. Most V-belts are 94% to 97% efficient depending on the tension and alignment of the belt. Alternators are only 50-60% efficient.

Amps x Volts = Watts
Watts / 745.7 (one HP) = Electrical HP Produced by the Alternator
HP x 55% Efficiency Loss = HP Loss (55% was used - 50% for Alternator and 5% for V-Belt)
HP + HP Loss = Total HP Used

So compute your electrical amp load and then you can compute the horse power used to drive the alternator.

Example:
20A x 14.5V = 290 Watts
290 Watts / 745.7 = 0.39 HP
0.39 HP x 55% = 0.22 HP
0.39 + 0.22 = 0.61 HP Total

Sample AMP Loads
Ignition Only - 6 amp (MSD 6AL)
- 12 amp (Electromotive XDI - 4 cylinder)
EFI - 15 amps (Electromotive TEC3r - 4 cylinder)
Fuel Pump - 7 amp Low Pressure
- 10 to 12 amps High Pressure
Data Logger - 1 to 2 amps
 
Ron...

No big deal but your math is wrong.
0.39 HP x 55% = 0.22 HP
Click to expand...

You should be dividing by .55 (55%). In the example, your input energy is less than your output energy... In short you're "creating" energy. Neat trick if you could... alas you can't.

Should be 0.39HP/.55=0.71HP. In other words it takes 0.71HP of mechanical energy to produce 0.39HP of electrical energy when the process is 55% efficient.
 
Thanks guys, for everyone's input. I should have been more descriptive in my situation. I am installing a dry sump system so I will have no room to keep the alternator on the front of the engine. I suppose I could drive it off the driveshaft if I find the need to use it.
Thanks again, I value everyone's opinion.
 
9.1.5.k.3. The generator or alternator is unrestricted. If a generator or
altenator is used it must be mounted in the same general
location as stock.

pg 478
sorry
 
Mark Meller":e9qpmlmh said:
Ron...

No big deal but your math is wrong.
0.39 HP x 55% = 0.22 HP
Click to expand...

You should be dividing by .55 (55%). In the example, your input energy is less than your output energy... In short you're "creating" energy. Neat trick if you could... alas you can't.

Should be 0.39HP/.55=0.71HP. In other words it takes 0.71HP of mechanical energy to produce 0.39HP of electrical energy when the process is 55% efficient.
Click to expand...

Mark,

You are correct. I was thinking of is upside down and backwards. I wanted to post an answer before double checking the math. I was worried that I got the efficiency rating correct. Trying to do too many things at one time I guess.

I think it may be better to break out the alternator efficiency from the v-belt loss since the v-belt loss is before the input to the alternator loss.

So what do you think of this corrected formula?

Amps x Volts = Watts
Watts / 745.7 (one HP) = Electrical HP Produced by the Alternator
Electrical HP/ Alternator Efficiency (50-60%) = Mechanical HP input into Alternator
Mechanical HP input into Alternator/ V-belt efficiency rating (95-98%) = Crank HP required to product electrical

Example:
20A x 14.5V = 290 Watts
290 Watts / 745.7 = 0.39 HP
0.39 HP/50% = 0.78 HP
0.78 HP/95% = 0.82 Crank HP to produce 20A at 14.5 Volts.

30A x 14.5V = 435 Watts
435 Watts / 745.7 = 0.58 HP
0.58 HP/50% = 1.16 HP
1.16 HP/95% = 1.22 Crank HP to produce 30A at 14.5 Volts.

With a full loss system can any one give us the loss of HP over the length of a National race?

As a side note, you can find more efficient alternators by looking at permanent magnet alternators. These are used on some motorcycles, newer hybrid style cars and in wind/hydro energy. Also turning the alternator at the correct RPM to match your required electrical load has a major effect on the efficiency of the alternator.

Reference Info
The 50-60% efficiency rating for the alternators is referenced from "Horst Bauer Bosch Automotive Handbook 4th Edition Robert Bosch"
The 95-98% efficiency rating for the V-Belt drive comes from Gates Belts FAQ - http://www.gates.com/facts/documents/Gf000188.pdf
 
If the last hp mattered, I'd lose #40 and go to a driving school or 4!

My version is a #8 Subaru Justy alt and a Odyssey #13 battery. Gotta drive the water pump,
so there's the belt anyway (and good point, Ron, a cogged belt is a lot less lossy than a vee- something to do later)

The little ND alt is almost indestructable, and tiny. Big pulley, charges only above 2k.

'course, if there's no room, moot point, eh? I'd recommend the Odyssey batteries- mine's been tough, and I haven't been nice to it.
(started the tow rig all weekend once just fine)

t
 
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