5-6V battery for portable laser?

[norty303]

Ok, so I know this may be better off asked 'over there', but I don't frequent there much, and I'm sure someone over here can help.

I've been asked to explore making a blue laser with a single beam for a piece of costume. I have a donor module with A140, with a FM2 for drive, which I'm going to start experimenting with expansion optics to get it within MPE. USing the FM2 means I can adjust the power output to balance for that sweet spot between beam tightness (or lack of it!) and raw power. Hopefuly, with that level of expansion, the divergence will be pretty good.

But I need to power it, and so need a reasonably long life cell that gives 5-6V roughly. Don't want too much more than that, as it'll just need to be sunk away as heat.

Also, can we avoid the safety discussion - its been dealt with and considered, and advise given.

[tribble]

A pair of LiFePo4 cells will give you 2* ~3.2v = 6.4V nominally, rechargeable, and good energy density.

A pair of LiPo's will give you 2 * (3.2 - 4.2) = 6.4 - 8.4v nominally, rechargeable, and good energy density.

Both require a "special" charger which is becoming more and more common.

If you go for a pair of CR123A cells, or other non-rechargeable lithium chemistry, you can get 2* 3V = 6V, but a use-and-toss approach.

5x garden-variety NiMh is 4 * ~1.2V = 6V and rechargeable, but depending on the cell you may get voltage sag halfway through the capacity and drop below your required minimum voltage. Super cheap though, and less prone to fires if overcharged. 4 AA-style battery holders are super common as well, but you'd have to splice in a single-AA holder for the 5th. This could be your ticket.

6V dry cell lantern battery? No idea how much capacity these have, though, and are bulky and heavy.

Good luck.

[mixedgas]

If the laser is low duty cycle, consider Sealed Lead Acid, common, cheap, and decent amp-hours. Chargers wildly available.

An amp-hour is exactly that, a one amp hour battery can provide one amp at nearly rated voltage for one hour, one half amp for two hours etc.
Usually I assume a battery is really capable of 65% of its rated amp-hours...

In reality its not that linear, but the amp-hour or mA-hour rating is a good guide.


Keep in mind the Battery should be fused, and some of the Lithiums do not take kindly to being over-discharged. I'd consider adapting a pack already made for model aircraft or hand tools that has the safety board for Li and Metal Hydride batteries. Some of the individual cells have internal safety boards as well. I had good luck hacking DeWalt packs about three years ago. Usually hand tool batteries just need an enable loopback on the connector.

This is one time the Other Place can really shine.
Steve

[norty303]

Sorry, I should've mentioned I'm an RC flyer so I'm familiar with liPo and NiMh cells. I had thought about a 2s lipo but a bit high on voltage. 5x NiMh cells seems a bit high on the voltage but the Eneloop ones have amazing capacity, but it's a bit bulkier than I'd like. Certainly an option, particularly if I put it on a decent umbilical.