I figured that I would dump some of my electronics knowledge upon you
. Along with some tests I conducted on a car. This was done at a temp of around 20F to -15F. Yes its cold here, -28 wind chill today, it was a joy walking to class on campus...
Note : These are my TEST results, they may not apply to you, if you try this and damage your viehicle, or yourself, not my fault. If you try one and kill your battery, still not my fault, but no biggie, just charge it.
First I will say this, working with car batteries results in current pulls as great as
600-800 Amps (Starting). A Direct short of the battery can dump excess of
1000 Amps. If you drop a wrench onto it, short the terminals, it will most likely get stuck, welded and burn...dont do that.
Now I will say this, it takes only 50-70 Milliamps across the heart to KILL you, thats 0.0070 Amps! Although getting that across the heart while working on a car is unlikely, it will still hurt, a lot.
Heres what I will explain :
-What the markings on your battery mean
-Some general electrical terms
-How long your battery will last in different situations (ie left headlights on)
-How much current your car uses when starting...
I'll start off with some info about your battery.
Heres the general info you need to know;
CURRENT refers to a
TRAVELING amount of
electricity, Aka AMPS not how much energy a battery can store. Therefore, when one says "amps" they "should" be refering to current travel, not capacity but generally, we just say amps. An Amp/hr is different, it is a measure of a sustained AMP draw over time, usually an hour. Thus if a battery has 2 Amp/hr capacity, it can sustain a draw of 2 Amps for 1 hour, but could easily put out 4 Amps for example. Heres my point for all this ranting : A batteries CCA rating is NOT how much "is in" the battery it is how much current the battery is capable of delivering. I saw someone make a runtime calculation based on this once. He thought a 1000 CCA battery had 1000 Amp/hr in it and calculated that he could run something for days and days when infact, it would be closer to 1/10 that value. A 1000 Amp/hr battery would weigh Over a THOUSAND lbs...an yes huge batteries exist. Like THIS. Dont think this...the definitions are below...
Car Batteries are rated 2 main ways, CCA (Cold-Cranking Amps) and RC (Reserve Capacity).
CCA : is defined as follows (simple terms) : How many amps your battery can put out a 0 degrees F for 30 seconds until the voltage falls too much.
RC : How many minutes your battery will last under a sustained 25 Amp/hr draw. Again until voltage drops too much. This can be considered capacity.
To determine the capacity of your battery do the following. Divide your RC by 60 to get hours, then multiply by 25. Ex 100 min : 100/60 = 1.6 * 25 = 41 so this battery has 41 Amp/hr capacity.
There are also two main battery types :
Starting and
Trolling(Deep Cycle).
Starting batteries are not meant to be completely discharged while Deep Cycles are fine with it. Deep cycles also usually contain more energy than a starting battery of similar size, but cannot deliver as much current.
TESTS
-Parasitic Drain (Draw from battery with car off, key out, all lights off)
-Cold Start (10 Sec.) Temp -15F.
-Radio Drain (How long can you really listen to your radio?)
-Marker-Light Drain (Turn signals, corner lights)
-Dome-light drain (Accidently Leave it on?, find out if you need to worry)
-Headlight Drain (What happens if you leave them on?)
Ok, now the goodies.
Here are the test battery specs
Brand : Durlast Gold
CCA : 600
RC : 100 min
CA : 800
RESULTS:
Parasitic Drain : 0.140 Amps or 140 Milliamps(MA)
This is how much current your car draws from your battery just sitting in the garage.
Based on this result your car will sit for approximatly
12.38 Days before it needs charged.
Dome Light Drain : .900 to 1.0 Amps
This is how much power your dome light draws, along with the parasitic drain.
Based on this result, you car battery will stay charged for
43Hr or 1.8 Days.
I would say overnight is OK, if your battery is similar to the test subject. No more than 24Hr.
Radio Drain (Talk-show volume) : Steady 1.5 Amps.
Want to listen to your radio with your car off? No problem.
Note this is with OEM and
NO SUBS.
Based on this result, your car battery will last
27Hrs or 1.15 Days.
So if you want to listen to your radio, even if its loud while waiting for someone/something, go for it.
Marker Light Drain (Turn Signals, Tail Lights) : 3.5 to 4.00 Amps
Based on this result, your car battery will last 11Hrs.
Headlight Drain (W/o Fog) : 19.80 Amps
Based on this result, your car battery will last
2.1Hrs.
With fog lights : 22 Amps
Based on this result, your car battery will last
1.8Hrs.
So, short term, you can leave them on, but this will really kill your battery, fast. Note that for most cars this also includes tail lights, marker lights ect.
I would say not more than
1 Hour if you want to be sure your car will start.
Note I could not do brights as well, due to hardware limitations, but lets hope you dont park your car with all the lights on....
Starting Your Car Drain (10sec, simulated 600 Amp draw) : 600+ Amps
It is interesting however that when all said and done, you will only drain your battery by 1.6 Amps which is suprising, so theoretically, you can get a lot of starts out of your car. But it doesnt work perfectly, like the math. In the real world you have to consider resitance, heat-loss and stress. So several starts should be fine.
Hope you enjoyed this random information!
Go ahead and spend extra $15 for better battery i know i wish i did on tacoma.
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