# Simple battery calculation **URL:** \ **Category:** Factual Questions\ **Created:** [February 28, 2011, 3:58pm UTC](https://boards.straightdope.com/t/simple-battery-calculation/572930 "2011-02-28T15:58:24Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![djinteractive](https://avatars.discourse-cdn.com/v4/letter/d/b4bc9f/32.png) [@djinteractive](https://boards.straightdope.com/u/djinteractive)\ **Post date:** [March 1, 2011, 8:29pm UTC](https://boards.straightdope.com/t/simple-battery-calculation/572930/21 "2011-03-01T20:29:07Z")
> [@beowulff](#): > > The 1600MAH battery in your second link will run the lights for around 15 minutes (probably a lot less, actually, but that’s what the calculations show). The 7.2AH battery will run them for around an hour. Don’t wire them in series - wire them in parallel, otherwise you will need 4 of the batteries above. As a former Radio Shack worker I have had to help with some projects like this myself. Probably one of the best battery options would be a slim camcorder battery such as this [http://www.radioshack.com/product/index.jsp?productId=3132836](http://www.radioshack.com/product/index.jsp?productId=3132836) (yes camcorders used to be that HUGE :eek:) They are reasonably light weight (as they were meant to have to be held on to) and have reasonable power (this one @ 2.3 AH would give 10-13 minutes good power and slowly dim for the remainder of it’s life around 20 minutes). Although the one shown is a web purchase only you may want to check out a Radio Shack or, if they still exist in your area, a camera/camcorder store which would likely still carry some on hand. IMHO this would be the best choice without going to a less power hungry lamp (RS I know carries both LEDs and other incandescent bulbs (as well as battery holders if you wanted to do the AA option perhaps with lithium batteries) which would cut the power cost down. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [March 1, 2011, 9:02pm UTC](https://boards.straightdope.com/t/simple-battery-calculation/572930/22 "2011-03-01T21:02:53Z")
> [@Gary\_T](#): > > get two 6V [lantern batteries](http://site.unbeatablesale.com/img071/azrdurmn908.gif). I’m a little leery of lantern batteries these days. A lantern battery is supposed to contain four F cells hooked up in series (an F cell is like a C cell only longer). Unfortunately, it has become common for the manufacturers to put four C cells with spacers in them. You have the extra weight and bulk of a lantern battery with reduced battery capacity. You can get plastic battery holders at Radio Shack that you can use to string C cells together in a way that would be less bulky than a lantern battery. The real problem with this though is that C cells aren’t really designed to put out that much current. If the OP insists on using those high current lamps, then that is going to demand a fairly large and bulky battery. If you use too small of a battery, the battery could end up overheating due to the excessive current. Worst case, the battery could explode. It won’t exactly be a grenade level explosion, but exploding pieces of battery and hot battery goo aren’t exactly comfortable on your skin. Lantern batteries also aren’t designed for that level of current. A lantern battery is typically designed for a load that is a fraction of an amp. Four of these lights is going to be over 6 amps. Either get lamps that draw less current, or get used to the idea that you are going to need a pretty hefty battery pack. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [March 1, 2011, 9:36pm UTC](https://boards.straightdope.com/t/simple-battery-calculation/572930/23 "2011-03-01T21:36:00Z")
> [@engineer\_comp\_geek](#): > > Lantern batteries also aren’t designed for that level of current. In that case, I withdraw the suggestion. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [March 2, 2011, 1:41am UTC](https://boards.straightdope.com/t/simple-battery-calculation/572930/24 "2011-03-02T01:41:00Z")
If it \*must \*be halogen, I’m thinking NiCad or lithium is the way to go. Much better to use LEDs… ---
**Author:** ![illuminati](https://avatars.discourse-cdn.com/v4/letter/i/e47774/32.png) [@illuminati](https://boards.straightdope.com/u/illuminati)\ **Post date:** [March 2, 2011, 12:41pm UTC](https://boards.straightdope.com/t/simple-battery-calculation/572930/25 "2011-03-02T12:41:00Z")
Just incase anyones interested a similar costume to the one Im making is here: [http://www.instructables.com/id/Building-Optimus-Prime/](http://www.instructables.com/id/Building-Optimus-Prime/) You can make out the lights on the top of the chest but there is a closer view here: > **[Optimus Prime Costume](https://www.instructables.com/Building-Optimus-Prime/)** > > Optimus Prime Costume: When first beginning my search for the most AWESOME Halloween costume ever created, I first wanted to pick something I've always loved... this lead to my childhood amore for Transformers which eventually became my Magnus Opus... The lights I have are ideal in terms of the look Im going for, they dont have to work but it would be really cool if they did. I have found some cheap LED alternatives here: [http://cgi.ebay.co.uk/1-GU10-LED-21-48-60-78-energy-saving-bulb-warm-day-cool\_W0QQitemZ180483809199QQcategoryZ109067QQcmdZViewItemQQ\_trksidZp5197.m7QQ\_trkparmsZalgo%3DLVI%26itu%3DUCI%26otn%3D2%26po%3DLVI%26ps%3D63%26clkid%3D7451577228173774006](http://cgi.ebay.co.uk/1-GU10-LED-21-48-60-78-energy-saving-bulb-warm-day-cool_W0QQitemZ180483809199QQcategoryZ109067QQcmdZViewItemQQ_trksidZp5197.m7QQ_trkparmsZalgo%3DLVI%26itu%3DUCI%26otn%3D2%26po%3DLVI%26ps%3D63%26clkid%3D7451577228173774006) any ideas if they are any good and if so what sort of power source they would need? Once again thank you all ---
**Author:** ![cantara](https://avatars.discourse-cdn.com/v4/letter/c/6f9a4e/32.png) [@cantara](https://boards.straightdope.com/u/cantara)\ **Post date:** [March 2, 2011, 5:19pm UTC](https://boards.straightdope.com/t/simple-battery-calculation/572930/26 "2011-03-02T17:19:29Z")
I would probably try getting some [cheap LED flashlights]([http://www.dealextreme.com/p/stylish-14-led-15000mcd-white-light-flashlight-with-rubber-handle-color-assorted-3-aaa-39466#open](http://www.dealextreme.com/p/stylish-14-led-15000mcd-white-light-flashlight-with-rubber-handle-color-assorted-3-aaa-39466#open) full view) and pull the head off and wire them to a single switch. The one I linked to takes 3 AAA batteries and will last for a long time. Others I have seen like this are very bright. I think I’ve seen them at dollar stores. If you mount the reflectors on the top of the chest and run wires into the chest of the costume, you could wire a single switch to light them at the same time. For that matter, you could wire them in pairs and have high/low beams. ETA…which I now see the Instructables used flashlights… ---
**Author:** ![illuminati](https://avatars.discourse-cdn.com/v4/letter/i/e47774/32.png) [@illuminati](https://boards.straightdope.com/u/illuminati)\ **Post date:** [March 4, 2011, 10:13am UTC](https://boards.straightdope.com/t/simple-battery-calculation/572930/27 "2011-03-04T10:13:33Z")
> [@cantara](#): > > I would probably try getting some [cheap LED flashlights]([http://www.dealextreme.com/p/stylish-14-led-15000mcd-white-light-flashlight-with-rubber-handle-color-assorted-3-aaa-39466#open](http://www.dealextreme.com/p/stylish-14-led-15000mcd-white-light-flashlight-with-rubber-handle-color-assorted-3-aaa-39466#open) full view) and pull the head off and wire them to a single switch. The one I linked to takes 3 AAA batteries and will last for a long time. Others I have seen like this are very bright. I think I’ve seen them at dollar stores. > > If you mount the reflectors on the top of the chest and run wires into the chest of the costume, you could wire a single switch to light them at the same time. For that matter, you could wire them in pairs and have high/low beams. > ETA…which I now see the Instructables used flashlights… So it looks like this is the way forward. Getting me some LED Flashlights which I will butcher into something more practical. Am I right in thinking as each of these needs 3 x AAA batteries I will need 12 x AAA batteries when wiring these in parallel? Thanks once to everyone who has taken the time to explain this to me. Never could get to grips with electronics etc ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 4, 2011, 1:50pm UTC](https://boards.straightdope.com/t/simple-battery-calculation/572930/28 "2011-03-04T13:50:09Z")
[quote=“illuminati, post:27, topic:572930”] Am I right in thinking as each of these needs 3 x AAA batteries I will need 12 x AAA batteries when wiring these in parallel?/QUOTE] if you wired the 4 LEDs in parallel you will need the voltage of 3 AAA batteries. you could wire sets of 3 AAA batteries in parallel for longer use time. plus and minus on the batteries can only be connected one way with LED flashlights. you need to pay attention and keep the same as the flashlights. easiest would be to use 4 separate flashlights as in the instructables and switch individually (keep them unchanged) or to keep the flash lights whole and modify by wiring all to one switch. [Previous page](https://boards.straightdope.com/t/simple-battery-calculation/572930.md?page=1)