Thinking of driving 3 XP-G's ( 3 on a star board) parallel config to run off a Shark Buck with dimmer off of 4-AA (6 VDC) limiting each led to 650 -700 ma. Any thing else to consider? Is that too much current off the batteries like 2A ? Also what is the max safe amperage the rechargeable and alkaline AA can dish out ? Trying to build a lamp (not flashlight) with only a tri-star and 4 AA.
XP-G trio on star run off of 4-AA
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Paul_in_Maryland
Flashlight Enthusiast
What kind of AA cells will deliver 1.5V per cell under load?
4 AA NiMH cells under load will deliver 4.8V.
4 AA lithium cells under load will deliver 6.8V.
4 AA alkaline cells under load will deliver about 4.4V.
The only AAs that will deliver 1.5 or 1.6V under load are the newish nickel-zinc (NiZn) rechargeables. Are these what you plan to use?
4 AA NiMH cells under load will deliver 4.8V.
4 AA lithium cells under load will deliver 6.8V.
4 AA alkaline cells under load will deliver about 4.4V.
The only AAs that will deliver 1.5 or 1.6V under load are the newish nickel-zinc (NiZn) rechargeables. Are these what you plan to use?
Thanks Paul, what I intend to use is to have the option to use the basic AA alkalines 1.5v or the rechargeable NiMh types rated at 1.2A. I just was concerned about the batteries getting hot or something else to consider under load. I really am designing and building a on-camera video light that must have the smallest possible size with 900 lumens or more with a dimmer. It must be powered by easy to get and disposable AA's. The run time at full output must not be less than an hour.Perhaps wiring them in series with a boost driver like the Fatman will do nicely if it is more efficient than a Buck (leds in parallel). I estimate that the battery draw will be around 2 to 2.5A and that the led amperage at or around 1A. Am I being too optimistic in run times? Thanks
Paul_in_Maryland
Flashlight Enthusiast
Wow, 2.5A from alkalines is probably not doable. If it is, it's not safe.
Given your need for high current in a small package, I would eliminate alkalines from your list of options. If operating cost is secondary, 1.8V lithium AAs would be a sound choice. Even if you want the freedom to switch-hit between rechargeable AAs and primaries, make lithiums your primary cells. You can find them now in any drugstore.
As for your rechargeable AAs, the default choice would be Sanyo Eneloop NiMH: they'll deliver high current without voltage sag. But if it's 6 volts you want from 4 cells, you sound like a perfect candidate for the new "green" 1.6V nickel-zinc rechargeale AA cells. Like Eneloops, they hold their voltage nicely under high loads. Their main drawback is that they require a special charger, they aren't safe to leave in the charger overnight, and that they have only about 75 percent as much amp-hours as Eneloops.
Given your need for high current in a small package, I would eliminate alkalines from your list of options. If operating cost is secondary, 1.8V lithium AAs would be a sound choice. Even if you want the freedom to switch-hit between rechargeable AAs and primaries, make lithiums your primary cells. You can find them now in any drugstore.
As for your rechargeable AAs, the default choice would be Sanyo Eneloop NiMH: they'll deliver high current without voltage sag. But if it's 6 volts you want from 4 cells, you sound like a perfect candidate for the new "green" 1.6V nickel-zinc rechargeale AA cells. Like Eneloops, they hold their voltage nicely under high loads. Their main drawback is that they require a special charger, they aren't safe to leave in the charger overnight, and that they have only about 75 percent as much amp-hours as Eneloops.
Hi Paul, I guess the alkalines are out of the question. Safety is my prime concern. The Eneloops, are they the same type as regular off the shelf rechargeable 1.2V NiMh ? I will most likely be using a boost driver, so voltage can vary a bit from 6V up or down. Those LiIthium AA's are out of the question because of price.I guess the only option for now is AA NiMh rechargeables.How safe are they at 2.5A? I would get only those that are recommended safe at that amperage.
PhantomPhoton
Flashlight Enthusiast
No, eneloop cells are not the same as common off the shelf NiMh cells. Head over to the battery and electronics section and read up. And yes eneloop cells handle 2.5A easily. I've run them at over 6A.
Paul_in_Maryland
Flashlight Enthusiast
Someone else will have to answer about Eneloops' safety at 2.5A; that would be about 1.5C, at that discharge rate. I can tell you that they do NOT come in any capacity but 1900/2000 mAH; sorry.
If you head on over to Batteryjunction.com, you'll find AA NiMH cells called High-Discharge Titanium Power Max. They can be discharged safety at 18 amps!
If you head on over to Batteryjunction.com, you'll find AA NiMH cells called High-Discharge Titanium Power Max. They can be discharged safety at 18 amps!
