Power source for standalone marquee light box

[Franco B]

I'm looking to make a standalone, single light box to display a marquee near my cabs. It's not really going to be possible to run it from the mains so I'm thinking of powering it with  battery.

With that in mind I'm thinking of using one of GGGs [NovaMatrix] LED marquee lights as it should provide a decent light output and I will be able to run it from a 12v battery. The product page says it draws 400ma.

I'm thinking some kind of rechargeable cell would be a good idea. Searching on ebay for 12v rechargeable battery' yields a lot of results but I'm not really sure what I'm looking for in terms of battery type/composition/technology.

Does anyone have any pointers?

[MonMotha]

12V SLA/gel-cell lead acids are easy to come by in relatively small formfactors and are quite forgiving.  Chargers are cheap and easy to get.  Batteries Plus and similar sell them at reasonable (but not Internet) prices with no shipping, and they guarantee that they're "fresh", which you aren't going to get from an Internet supplier.  Fry's Electronics has them, too, if you have those in your area, but theirs sit on the shelf for years sometimes.

You could also just stack 10 AA Ni-MH batteries together in series (buy a holder) and charge them using a standard Ni-MH charger.

You can work out how long it'll last by taking the battery rating in mA*hr and dividing by 400mA.  If the battery is rated in A*hr, multiply by 1000 to get mA*hr (e.g. a 2A*hr battery is a 2000mA*hr battery).  If you're putting multiple batteries in series, you use the lowest rated.  For multiple identical batteries in parallel, use the sum of the ratings.  Don't put different batteries in parallel.

You might ask Randy if those things actually need 12V.  If they just have a dropping resistor, a minor modification may let you run it off of e.g. 6V and waste less power.

[Franco B]

Cheers buddy, there is some great info there 

I do have a good Ni-Mh charger, that might be the most cost effective route to take. Would I not need 8 1.5v AA cells for 12v rather than 10?

I'll shoot Randy a PM and see what he says, that's a great idea about finding out the actual power requirements of the array!

Thanks again 

[MonMotha]

Nickle chemistry rechargeable are only 1.2V per cell instead of 1.5V, so you'd need 10 to get 12V even at full charge.  On the upside, they don't drop like alkalines do as they discharge (there's a very sharp drop-off right as they become fully depleted, rather than a gradual drop like alkaline), so you shouldn't see as much dimming as SoC changes like you would with non-rechargables.

[GregD]

 I would use Led strip lighting and an 8.4 volt rc car battery.

[MonMotha]

I'm loathe to recommend Li-Poly RC car batteries for hobbyist-hacked setups.  Most of those things can easily source 150A or more, which can be very dangerous if you accidentally short them, and most of them seem to lack effective safeties for cost reasons and the fact that the "rated" draw is pretty close to the short-circuit current.  They're not particularly cheap, either.

Nickle and lead-acid batteries are much more forgiving.

Otherwise, yeah, they'll work, and the energy density is very good compared to Ni-MH or lead-acid.  Similar to my comments above, you may be able to modify those fixtures you've selected for 7.4V nominal operation.

[Franco B]

Thanks MonMotha, that's the advice I was looking for. Thank you.

[CandyCabJapan008]

Thanks MonMotha, that's the advice I was looking for. Thank you.

Hey Franco I got a quick question for you do you think you can make me a Marquee holder for a Sega Blast City
like this guy has but better




watch it at around :30 I never seen that before

[mgb]

Other alternatives can be a 12 volt 4ah battery as is used for backup of home security systems or don't bother battery charging and use a small 12 volt plug in wall wart and just get a thin wire to it

[pinballjim]

Good lord, people, way to overthink this.

Get a cheap string of white christmas LED lights that run off 2 AA batteries.

Done.