Tuesday, November 14, 2017

Batteries, Small NiMH Rechargeable

Humans are not designed to live without light at night, we must have it to survive in today’s world of crime and violence. A Preppers best friend for lighting and communications in an extended grid-down situation are rechargeable batteries to keep these needed devices going.

Some of us have small generators to run lights and refrigeration, even heat for the home during a short term grid down. But long term, when your gas is gone and gas stations are closed, the only thing left is your own solar system. A 200 watt system can run small portable 12v refrigerators (Dometic), and recharge all your batteries for lighting and communications. This size of system is inexpensive and easily be made portable.

All my critical battery powered flashlights lights and radios are powered with “AA” rechargeable batteries. I only choose “AA” size because it makes battery stocking easy as this one size powers all my critical devices.

Like all prepping items, they need periodic review and maintenance (such as recharging) even if not used. NiMH (nickel–metal hydride) type batteries will self-discharge when not in use. The self-discharge amount varies with new technologies, from 10% to 50% with most only 20%. So once a year, and for me that is the beginning of hurricane season. I recharge (top-off) all my NiMH batteries so they are ready to do their job with full power.

When purchasing new NiMH, try to buy the same manufacturer brand and the ones with the largest mA (milliamp hours) or stored power (amps). Today that’s generally the 2300mA or 2500mA size.

What is ‘mA’ (milliamp hour)?
It’s a unit of electric current equal to one thousandth (1000) of an ampere. The SI base unit for electric current is the ampere. One ampere, is equal to 1000 milliamps, or 1 amps.
A 2500 mA battery equals 2.5 amps of stored power.
A 1500 mA battery equals 1.5 amps of stored power.

I use two types of chargers, a fast recharger and the other is a smart recharger.

The fast recharger;
is just that, fast. It can recharge for “AA” batteries in as little as 15 minutes!

The smart recharger;
has a ‘conditioning’ charge. After a number of battery uses, the NiMH can develop a ‘memory’ or it thinks it is fully recharged but it’s not. The battery will tell the charger it’s full and the charger then stops the recharge cycle. The smart charger has a special conditioning charge function, user selected, will automatically discharge the battery completely, then recharge the battery to 100% of its’ rated (milliamps) capacity. Note that this conditioning charge is far slower than the fast recharger.

Below are the two chargers I use and recommend.

Important Note:
Every NiMH battery will have its’ mA capacity printed on the side. DO NOT MIX mA capacities either in the charger or in the device they’re used in. Why? Because the batteries have a chip (computer) in each one. This chip talks to the charger and lets the charger know when it is full and doesn’t need any more recharging. The typical charger has a four bay or battery capacity. If you put into the charger three, 2500 mA and one 1500 mA battery, the lower mA battery will be recharged first but, what happens is when the 1500 mA talks to the charger and says it’s full the charger will shut-off the cycle. What happens to the three 2500 mA batteries? They will only be charged to 1500 mA. Only charge the same mA batteries at the same time be it 1, 2, 3 or 4 of the same mA batteries.

Quick NiMH battery Facts:
Charge cycles: Up to 700 times
Charge retention: Lasts up to 12 months

The CCRANE Quick Charger (Smart Charger)

CCRANE showing charger compartment. Will charge one or up to four at a time of “AAA”, “AA”, “C” or “D” size batteries. Either NiMH or NiCad batteries.

Energizer Quick Charger (15 minute charge cycle)

Shown is a 2500 mA battery label. All rechargeable batteries will be labeled with their mA capacity. I also date each battery when purchased for overall age reference.

Both chargers, come with a 110v wall plug/cord and a 12v plug/cord for charging off your power port in your car or solar system if you have one. If 110v grid is down you can recharge your batteries from your car battery.


  1. Mike,
    You would be surprised how many people don't think about batteries, and having lights for when the SHTF. Great post!

  2. We have several small battery packs for our cell phones, and tablets. recharge by a USB port. My youngest daughter just wore hers out. She never seems to let her phone fully charge. But its an Apple. I have two i bought at Walmart of around $10.00 I can get two recharges for my cell. I can also use on my small tablet. We have some rechargeable AA and AAA batteries

  3. Very timely post (even though I missed it's appearance by a week!). I'm really frustrated with having to buy batteries. They have gotten so expensive! I especially like that the one you show has a 12-volt plug. We're not off grid, but having a solar panel is certainly handy for recharging batteries!

    1. Rechargeable battery technology has come a long, long way in the last 10 years. Their biggest problem in the early days was 'self-discharging'. That is now all but gone as the new batteries hold a charge for 12+ months, so this now makes the rechargeable's a strong candidate for replacement of standard alkaline batteries, especially with the ability to be recharged 500-700 times.

  4. I just got a new weather radio, and the little brochure that came with it said "do not use with rechargeable batteries." Any idea why that would be?

  5. I have no idea why they would say that. May want to call or e-mail the manufacturer to clarify.

    I checked the manual of my new CCrane radio that uses “AA” batteries and NiCads are fine to use but not Lithium.

    My instruction manual says:
    “Battery Power Level Indicator doesn’t show full charge when using rechargeable batteries: Rechargeable batteries will not show a full charge on your radio display. The CCrane Skywave is calibrated to read the charge of your alkaline batteries, which is 1.5 volts at full charge. Rechargeable batteries, however, are fully charged at just 1.25.volts, so your radio will show a partial charge even if the rechargeable batteries have been fully charged”. It also states: “DO NOT USE LITHIUM BATTERIES”. They gave no reason as to why.

    So, I went to a Lithium Battery charging web site to see if they had any information about it. They did.

    “Lithium ion charge / discharge basics
    Charging lithium ion batteries is very different to charging Ni-Cads or NiMH batteries.
    Charging lithium ion batteries is voltage sensitive rather than current based. Charging lithium ion batteries is more akin to charging lead acid batteries.
    Differences are found in that the lithium ion batteries have a higher voltage per cell. They also require much tighter voltage tolerance on detecting full charge and once fully charged they do not allow or require to be trickle or float charged. It is particularly important to be able to detect the full charge state accurately because lithium ion batteries do not tolerate overcharging.
    Most consumer orientated lithium ion batteries charge to a voltage of 4.2 volts per cell and this has a tolerance of around ± 50 mV per cell. Charging beyond this causes stress to the cell and results in oxidation that reduces service life and capacity. It can also cause safety issues as well.”


    I also found that Lithium Battery voltage can vary greatly, in “AA” for example, it can be between 1.75 and 3.5 volts. Several lithium batteries in series could create some serious high voltage. This higher voltage could damage the electronic device. Need to read the label carefully.

    My CCrane radio can also charge NiMH batteries while in the radio. Based on the statement above, the Lithium battery needs a special charge rate and voltage to recharge them. A fire can result if using a Ni-Cad charger to charge Lithium batteries. So probably that’s the reason for the caution.

  6. Great article! Thanks for the info.

  7. Great article but I wasn't able to find C. Crane's Quick Charger on the internet today 11/30/17. Just FYI.

    1. My charger is about 8-9 years old. They may have discontinued the model and have another one available. Go to C Cranes web site and check their catalog.