Question for Electronics guru's

[greenpastures]

Electonics is not my field. Want to calculate how long certain batteries will last in 2 torches. Is it Ohms law?

Torch 1 has 4 AA batteries rated 1.2V and 1700mAh (milliamp hours). Globe is 2.5V / 0.25A. Torch 2 has 4 batteries with same specs as above, but globe is 4.8V / 0.75A.

Anyone know the formula to caclulate the hours for each torch?

[spock]

Here is my guess.
V=IxR so the specs of the bulb give I=10 ohms
I think voltages in series add, so you you have 4.8v supply.
Using ohms law again: current through bulb =480mA
Since you battery will supply 1700ma for an hr but your torch is only running a current of 480 mA then my guess is the hrs is 1700/480 which is 3.5hrs.
You can do the next one.
Now please tell me what you think of VRE

What happened to your fishing post?
I liked it.
You might know that what you mentioned is what the buddhists call this Dharma - seeing things for what thay really are.
So much of our day (if not all) is filled with mental activity. And since we are creatures of habit, when there is no reason to think, the mind tries to continue anyway, hence the mad monkey mind.
Spaces are ment to be there, what would music be like without any rests, working all day with out "smoko", being glued to the screen sharetrading day and night, etc.
I bet a few people have wound up in a sticky position upon market close on friday, and it is on their mind for the whole weekend even though they have a plan what action to take come monday. This has the potential to ruin what could be a great weekend. Don't feed the monster - just watch it, it will eventually go away.
How many opportunites to learn and to truely experience the present moment have we missed by being wrapped up in our own mental constructs, whether they be true or not.
With regards to fishing, I have observed how people lose the joy of the simple experience by becomming unsatisfied so that they are not happy untill thay are reeling in a marlin.
I can get no... na na na... na na na na.

Happy fishing
cheers:)

[Phaedrus]

GP,
Spock is on the right track, but has overlooked the fact that in torch 1, the batteries are in two serial pairs, linked in parallel. This means that the total configuration has a capacity of 3400 mah. With a 250 ma bulb, this gives 13.6 hours.
With torch 2, all batteries are in series, so the overall capacity is 1700 mah. With the 750 ma bulb this gives a life of 2.27 hours. (Half the capacity, three times the load, but six times the light)
Keep in mind that these figures are theoretical only - by and large, the lower the consumption, the higher the total mah you can expect from any given battery. In this case that means the 13.6 figure may be pessimistic, the 2.27 hour figure optimistic. It also varies according to whether the torch is run non-stop until flat, or is used only intermittently - in which case longer total times could be expected.

[greenpastures]

Thanks guys, I'll do some calcs latter. BTW, one of the torches has a solar panel on it to charge the bateries during the day, all inside a water proof case. It's batteries are 2 batteries X 2 slots in serial. Torch 2 has 4 batteries X 1 seperate slots for each. Re VRE Spock, I'll post something latter. Have a few things to do ATM.

[spock]

Don't bother GP.
I think I've found out all I need to know to stay away from it. Not for me.

Cheers

[whatsup]

All that I know about batteries in torches lasting a long time ,is this ,If one wants to save a battery s life when not using the torch ,take a battery out of the torch turn it around replace same and keep it like that when stored then, when you want to use the torch turn it the proper way around and presto your torch has plenty of power in it ,as if not if left unturned the torch shorts through the switch ever so slowly and no power when you want to use it, hell that was long winded!!!

[greenpastures]

re VRE, don't know much about it but can share some stats. According to my data analysis (pre-emtive early alert as often is the case by a number of weeks, sometimes more), support stepped in week ending 9 April and has continued and broken moving average resistance. Thats the big picture. Smaller picture for the past 2 weeks or so supports the bigger picture at this time. Average daily liquidity about $150,000, traded 0.26 of that last Friday (have not done analysis since then). Despite the support, my system does not pick up on stocks until technicals satisfy a list of criteria. Only then do the fundementals triggers kick in. At this time, VRE needs a little more volume but technically is at a long term low and in that sense, a trigger for consideration. Market cap a low $31m. Volume criterai was not satisfied on Friday, but on Thursday did approach a noticable ratio to the average.

[Falcon]

spock is correct.
torch 1 has a bulb rated at .625w and torch 2 rated at 3.6w. Because your feeding torch 1 higher voltage it will light much brighter and use more power (watts) and last only 1.24hrs longer than torch 2. If you fed it just 2 batteries (2.4v) it would last about 7hrs although not as powerful. Torch 2 @ 4.8v will last about 2.26 hrs.

[spock]

Thanks falcon, you make me want to find out for sure now. Perhaps when I get a round tuit.
Watsup - how can current flow through a switch that is turned off, there is normally air between the contacts. The open switch acts as a capacitor with the dielectric of air? Is this some bizzare quirk of nature, like divining for water?
I guess that when the switch is turned off current will still flow through the batteries, electrons will be sucked from one side of the circuit and deposited near the cathode then current will stop, very shortly after ward. nevertheless, I will try it, eventhough it appears to defy logic.
Thanyou greenpastures, I sold before your reply , a few noteworty points you have mentioned.

Chairs Hall.

[Phaedrus]

Falcon, you, too, have got it wrong. Your wattage calculations for the bulbs are are correct, but there is no need to use watts at all to calculate the answers. The bulbs are rated in amps (milliamps) and the batteries are rated in milliAmpHours, so mAh divided by ma = hours. Simple.
When you go on to say "Because your feeding torch 1 higher voltage....." you have really lost the plot. Torch 1 is running at 2.4 volts - exactly half the 4.8 voltage of torch 2. Because it has 4 batteries, two series sets, linked in parallel, the battery capacity is doubled to 3400 mAh. Since the we know the bulb is rated at 250ma, the batteries will last 3400/250 hours = 13.6 hours. (More accurately, the actual power consumption will be 240 ma, since we are running the bulb at 2.4 volts rather than the nominal 2.5 volts it is rated at. This gives 3400/240 = 14.16 hours.)
With torch 2, since all four batteries are linked in series to give a total of 4.8 volts, the total capacity here remains at 1700 mAh. Now, we know that the bulb in this case uses 750 ma at 4.8 volts, so the torch will run 1700/750 hours = 2.27 hours.
Try looking at it this way. The two torches have the same 4 batteries, thus the same overall capacity, regardless of how they are configured. Torch 2 has a bulb about 6 times as powerful as torch 1, so it will give a lot more light, but will use about 6 times the power of torch 1. Therefore torch 1 will last about 6 times as long as torch 2.
14.16 hours versus 2.27 hours.

[greenpastures]

Havn't played with calculations much (doing stock market quarterly housekeeping), but on the basis of what was written above, my calculation is:

Torch 1: (1700 mHa X 4 batteries) / 250 milliamps / 2 = 13.6 hours. [2.4V globe /1.2V batteries = 2]. Actually, this torch has a globe rated .3A and 2.4V so it would be 11.33 hours. Torch 2: (1700mHa X 4 batteries) / 750 / 4 = 2.26 hours. [4.8V globe / 1.2V batteries = 4]. Looks like Phaedrus calcs were the simplest.

Don't know @ what rate the solar panels (10 panels, each 20mm X 20mm) charges the batteries (assuming full sunlight) because specs provided with torch were not specific. To test, will discharge batteries fully and leave torch in full sun for 1 day, then let the torch run at night until flat. Subsequently repeat exercise in full sun for 2 days and compare results.

[whatsup]

Spock Yep at first I thaught like you but after always finding my torch batteries flat when I needed them I thaught how could this be happening so I decided that somehow the torch was shorting by itself so I then Did as I have recorded above I suggest that you try this ,get 2 identical torches, leave 1 as I have suggested and the other leave together , leave for several weeks then check, in my experience the one which has its batteries "turned" will have good power when reassembled but the other will be very weak or no power at all.

[Risk]

batteries are pretty cheap.

the day I have to calculate how long my batteries will last, is probably the day to give up on sharetrading.

If you need extra batteries, send me an email and I'll send you a box.

:-)