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i figure at least a half dozen of you could throw me an accurate guestimate faster than I could figure out how to do the math myself.
i would like to take a basic car battery, hook up an inverter to it and let my crew use it to recharge their cellphones during the Oregon Country Fair, but I would like to have some idea how many charges it would likely last in case I need to add extra batteries or a solar trickle charger.
...might also want to run a string or two of LED's for a few hours at night too
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Oregon
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Re: another batter question: one average car battery = how many typical cellphone recharges?
Fri, June 26, 2009 - 7:53 AMA car battery is inappropriate for this app, being engineered to maintain a pretty steady voltage, rather than the extreme discharge demanded by inverters & other power draws. Your car battery may or may not last the week before being ready for the scrap merchant.
The minimum setup for your requirement is either a 12V marine battery, designed to fire up an putboard motor, or a pair of 6V golf cart batteries cabled together to produce 12V. Both of these options are designed to withstand a constant cycle of deep discharge and recharge. These are available used/reconditioned from many battery shops for cheap. Get a warantee.
A small trickle charging PV panel putting out 15 watts could be a reliable charging device. You can get away with the whole deal for less than $250.
An 85% efficient inverter can be left out of the loop by recharging the phones by way of 12V car type cellphone chargers drawing direct from the batteries.
Other better option is to simply get some unit-specific cigar lighter plug-in phone chargers at the dollar store and recharge off any of several vehicles, being sure to use vehicles that will be driven home at the end of the day so no one vehicle has its battery pulled down too flat. -
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Re: another batter question: one average car battery = how many typical cellphone recharges?
Fri, June 26, 2009 - 10:09 AM
yikes, what a goofy typo in my title line ...shouldn't post when tired
deep cycle --check
i was thinking of an inverter because not everyone on the crew drives or has car chargers for their phones. As well, our booth (and most of the Fair) is more of a "walk in " affair ...cars aren't allowed once it's open.
for a solar charger, how bad would my buyer's regret be if I did the harbor freight special? (www.harborfreight.com/cpi/cta...item.taf ) -
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Re: another batter question: one average car battery = how many typical cellphone recharges?
Fri, June 26, 2009 - 6:21 PMYou can buy a cigarette lighter adaptor to have a regular plug in phone charger work off a car. They cost about 20 bucks at Walmart. (Yuck) I'm sure you can find them elsewhere though. I charged my phone off my car for a week or two when my puppy ate my regular phone charger.
~smiles~
Queenly
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Re: another batter question: one average car battery = how many typical cellphone recharges?
Sat, June 27, 2009 - 12:14 AMPrice of Harbor Freight's 15W unit is very reasonable. I'd get a pair to start, and at least 12V worth of storage battery.
There's no real arithmetic to this because there are so many unforseen variabes. Best bet is to add on panels and add on baterries as required, if required.
Once the free sun power is available, people will want to run PCs off it, or tailgate blenders, or charge camera batteries, etcetera. And when you have a whole crew doing their cellphones off it then usage may be more than you've counted on at first.
PV panels are a good investment. There are always many uses year-round for the system. -
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Re: another batter question: one average car battery = how many typical cellphone recharges?
Sat, June 27, 2009 - 11:11 AMYeah I definitely see an issue with folk leaching power... The harbor freight ones for the price are viable. You may want to consider 2 deep cycles with that wired with an isolator between em... That always keeps one topped off for emergency. If it is a convenience thing one will be fine but i would be nazi about who is allowed and what application.
looking at my charger it appears it only pulls .15 amps... you could easily run 3or 4 at a time with little wattage issue.
As braggi noted the big puller is the inverter. You lose a significant amount in conversion. If you can get people to make sure they have a car charger you save a ton of power in translation. Inverters can be bought with a 25 watt max for 20 some odd bucks at truck stops and the like. this would give you one port for AC.. If they didn't bring an car charger then they just have to wait.
JSin -
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other cheap option
Mon, June 29, 2009 - 12:42 PMfind a battery supply shop (scroll to bottom for extra bit of info on this)
get a BIG ASS USED TRUCK BATTERY LIKE I GET - $40 - (used is actually reconditioned, more often than not actually more or less new battery from a wrecked vehicle, or one that was returned new for being wrong size, at least that's what they say at my battery place, and from what i've gotten , they seem to be that way, more or less new ( my truck had some roubles and was eating batteries so i got to but a few of them)
HOW MANY CHARGES?= well geez ok that's a bit of math
3.7 volts for a cellphone battery, anywhere from 700 to 2450 mAh
big battery has approx 14 volts (yes on a 12 volt battery its output is usually about 14 if in good shape)
800-1000 amps available
poached info>>>>>You need to multiply the amp-hours by battery voltage. That will give you watt-hours. Divide by 1000 for kWh.
To go the other way, multiply kWh by 1000 to get Wh, divide by voltage to get Ah.<<<<<<<
we're dealing with milli watts rather than kilo here so you're so far looking at a few charges, my low estimate is around 10 completely dead phones restored to full power
i might keep looking, that's as far as i feel like going with the math right now, but the morte accurate calculation is out there is you seek it out
FURTHER *********************
yes, a deep cycle battery is a better long term solution IF you plan on doing this fairly often BUT a deep cycle battery is NOT CHEAp, a new one will be well over $100 if any good at all.....
a fully charged used battery from a large truck (don't get a little import car battery, one way to get a big ass one is to say it is for a diesel truck ( mine is 83 f 350 6.9l diesel for example you could use)
will cost around $40.
if fully drained, it wont be of much use but it can be taken in for recycling ( usually worth $1)
and you'll be done with it for $40 instead of having to recharge and store this huge deep cycle battery you wont use again for a long time and it will probably go bad on your shelf
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