Battery Powering Prop-1 and some LED's

[gadget-evilusions]

I have in the past used an 8 x AA battery pack to power a prop-1 and some leds on a haunted house actor. It appears that after a while the voltage drops off.

My goal is to have 12v as long as possible, longest life without having to change batteries all the time. Would it be better to take two 9v batteries, connect in series, and use a regulating circuit to take the 18v down to 12v? or stick with the 8 AAs?

I think 9v batteries don't have as much milli amp hours capacity, but I don't want to under power my device once the AAs start dropping down in voltage.

I am looking at these tech sheets for battery specs. http://data.energizer.com/PDFs/522.pdf and http://data.energizer.com/PDFs/E91.pdf

[JonnyMac]

Think of battery size like a gas tank: the bigger they are -- physically, that is -- the more energy they can hold.  A 9V battery is just six 1.5v cells stacked up in a case, hence there's a bit of pressure (voltage = electrical pressure), but not a lot of capacity.

You're better off using a group of six or eight C or D cells, or get a gell cell like this:
-- http://www.allelectronics.com/make-a-store/item/GC-123/12V-1.3AH-SEALED-LEAD-ACID-BATTERY/1.html

Note that this battery has about the same footprint as the Prop-1.

[JackMan]

A rechargeable battery pack would be another option. I use NiMh (Nickel Metal Hydride) and LiPo (Lithium Polymer) packs in my R/C planes which would work quite well for a Prop-1 with LED's. The LiPo packs are very small for the amount of mAh's they provide but you do need a charger specifically made for LiPo's. LiPo packs come in different cell counts, you would need a three cell pack for 12 volts. Two 5-cell NiMh packs in series would also give you 12 volts. Check Tower Hobbies.com (or any major R/C retailer) for the different choices, you want the higher capacity packs (mAh). Don't go with the rechargeable batteries you can buy at any store, they don't even come close to holding a charge like the packs made for R/C.

[gadget-evilusions]

That battery pack looks good for what I am doing. How does 1.2 AH translate to hours at 50ma draw? Is it straight up math or is there some complicated formula for figuring hours etc?

Is this the charger I would use? http://www.allelectronics.com/make-a-store/item/BC-100/12V-1A-CHARGER-FOR-LEAD-ACID-BATTERIES/1.html

[JonnyMac]

I'm sure there's a wonk somewhere that can provide a more complicated estimation but for non-critical applications like this we can keep it straightforward.  1.2AH is 1200 mA for an hour, or 120mA for 10 hours, or 60mA for 20 hours.  You need to account for the current draw for the Prop-1 (20 mA) plus any loads that are running.

That charger you indicate seems to be valid; you may want to give the guys at All all phone call to confirm.

[gadget-evilusions]

I shot them an email to ask.

I thought that was the basic idea of mah and load. Thanks Jon.

[gadget-evilusions]

Just wanted to say thank you, that battery from all electronics works perfectly for what I am trying to do. Total with battery and charger was only $20. Now I am going to order some more of the batteries. Definetly alot cheaper than buying a butt load of AAs.