minershop - Fluorescent Minerals from Greenland and the World

battery-pack2.jpgBattery Packs

Portable battery operated lamps allow for long hours spent in the field searching for fluorescent minerals. Most lamp manufacturers sell sealed lead-acid (SLA) batteries to power their lamp.  But those batteries have a lot of disadvantages.  Two newer technology battery packs listed below are suitable replacements for an old-technology SLA battery.  

You can build your own pack or purchase off-the-shelf packs.  Several vendors sell LiFE packs, but I have not found any who sell a pack based on Super NiMH, so instructions to build your own are included.

What does 2000MAH or 7AH mean?

Perhaps a little discussions about "mAh" is in order; "Milliamp hours" is what it stands for – a 2,000mAh battery would put out 2,000ma (2,000 milliamps – or 2 amps) for one hour before draining. Often, lead/acid batteries will simplify things for you and just list them as 7AH (7 amp hours – 1 amp for seven hours, or 7 amps for one hour). The average portable UV lamp on the market today uses a little less than 1 amp per hour.  Therefore, a 7AH (7,000mAh) battery will run the lamp for 7 hours before becoming fully discharged.

Battery packs can be purchased with a range of amp hours.  The more amperage a battery has, the heavier and larger (and more expensive).  I prefer packs in the 2AH to 4AH range.


Lithium iron phosphate battery packs offer high power and long shelf life in a small, lightweight package.  Unlike their cousins (LiPo) they are much safer and do not have the same risk of fire and explosion.  Unlike lead/acid they keep putting out the maximum voltage until the very end of their discharge cycle - giving you maximum brightness for the entire battery life (a lead/acid battery discharges linearly over time.  Towards the end of its discharge cycle the lamp may still be lit, but it is powered at perhaps less than 50% brightness).

Read more about LiFE...


Sealed Lead Acid

This type of battery has been the standard for many years.  It works, but for my tastes is simply a poor choice for a portable light.  They are heavy and bulky - I'd rather carry rocks than a 7lb battery.  They are unreliable - often an SLA battery will go dead just sitting on the shelf over the winter.  These batteries have a very poor shelf life.  Additionally, they are limited in recharge cycles, sometimes as low as 200 cycles.

I do not recommend this battery.  If you bought one it will probably work for a few years but eventually you will need to replace it.  Please consider one of the newer technologies listed here.  No further information is provided.



NiMH is an established technology and NiMH packs are lighter and more reliable than the older NiCD (nicad) packs or SLA batteries.  NiMH packs don't have memory problems that NiCD packs were plagued with, have higher recharge cycles, and produce maximum voltage until the end of their recharge cycle.  They do have a severe shelf life problem and can go bad if left discharged, or stored for many months.

I do not recommend this technology for new battery packs.  No further information is provided.

Super NiMH (Eneloop)

Eneloop brand batteries offer all the advantages of NiMH (high power, lightweight, small) without the major disadvantage of high shelf discharge.  For those not wanting to deal with lithium batteries, this is an excellent alternative.  But nobody (that I have found so far) makes a 12v battery pack from these so you'll have to brew your own.

Read more about Super NiMH...


Build vs. Buy

For only a slight premium you can purchase a pre-built LiFE battery pack from several vendors.  I would not attempt to build a LiFE pack unless you really know what you're doing, and you have a good reason to attempt it.  NiMH packs, on the other hand, are rather simple to build.  If you're handy with a soldering iron/gun and can follow some simple DIY instructions you'll have your pack up and running in no time.

Read more about building a battery pack....


Battery Monitor

The absolute most important thing you can do to insure long life from your batteries is to not discharge them below their ratings.  A very simple battery monitor circuit allows you to tell when your voltage is dropping below 12 volts - time to change batteries.  

Read more about battery monitors....

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