This is the first in a series of “solution” articles based on the need to recharge devices via solar power. I hope you find these articles of value when solving prepping needs that you might have. I hope that you find this article informative enough that you don’t get sucked into overpriced retail solution packages that sound and look pretty but are hardly the best choice…or even a good choice.
So, let’s get started by defining the need…
“The ability to recharge four AA batteries at a time using solar power.”
Seems simple enough, yes? Well, on the surface it sounds simple but as you well know there is always more to a problem/solution than what first appears. Let’s talk about a couple of those issues:
- What kind of AA batteries are involved, Ni-CD and/or Ni-MH?
- What is the mAh (milli-amp hour) rating of the batteries?
- Are they high quality batteries such as Tenergy?
- How many hours of sun will be available each hour of the day for charging purposes?
- Will this be a man-portable field operation or fix-location operation?
Lets take the solution options in order…
Please never use rechargeable batteries other than Tenergy, Eneloop, or Duracell. Any other brands pretty much suck. Generally speaking use the highest rated mAh battery you can find and afford. The higher the mAh rating the longer the battery will last; technically speaking mAh rating implies the “capacity” of the battery which infers the length of “run time” of a battery.
It is my personal experience that I have seen little to no difference in battery performance whether NiCD or NiMH batteries. But, you must know what type of battery you are using to ensure that the charger you choose is designed to charge that type of battery.
I personally use Tenergy AA & AAA batteries for my emergency preparedness requirements.
Type of Batteries –
NiCD batteries are Nickel-Cadmium. Cadmium is used in the battery and it is a toxic heavy metal. Please dispose of them properly if you use this kind of battery. The benefit of this type of battery is it won’t self-discharge as fast as a NiMH battery. NiCD batteries can also handle a higher charge rate than a NiMH battery. If your device requires a heavy or high load of amperage then the NiCD is the right choice. Most people will use a device such as a camera, flashlight, or weapons optical…a NiCD battery is probably not your best choice for those devices. Depending on your two-way radio, this type of battery may be the right choice.
NiMH batteries are Nickel-Metal Hydride. NiMH batteries will self-discharge faster than a NiCD battery. They will also take a higher charge rate than a NiCD battery. Yes, that means they will charge faster. MiMH will not handle a high amperage load as well as a NiCD battery. A NiMH battery is more suited for long duration usage where there isn’t a high amp load required. Such usage would be something similar to a camera, flashlight, or weapons optical.
The reason why it is important to know the difference is to ensure you are using the right battery for your device to get the best performance. Another significant reason to know which battery you are using is the battery charger. A few older generation battery chargers can’t sense the difference between a NiMH or NiCD battery. And since they can’t sense the difference they won’t properly charge the battery. An example of an older generation battery charger that isn’t suited for NiCD batteries is a Goalzero Guide 10 charger…it can’t properly charge NiCD batteries.
Battery “Memory” –
Do rechargeable batteries have “memory” which affects their performance and ability to be recharged? Technically neither the NiCD or NiMH rechargeable batteries have “memory” issues. However, both types of batteries are affected by the “voltage depletion effect”. Simplifying the whole memory thing is this, both battery types benefit from being fully discharged occasionally, then fully charged immediately afterwards. You want a battery charger that can discharge the battery then immediately fully charge the battery. Battery chargers like the Goalzero Guide 10 or Sunjack unit do not have the ability to perform the battery “discharge” and then immediately fully recharge the battery.
Warning/Note: The Goalzero Guide 10 doesn’t have the ability to properly charge NiCD batteries. The company recommends that the charger not be used for NiCD batteries. The Guide 10 unit can not sense a NiCD battery if it is inserted into the unit. Battery damage may occur should you attempt to charge a NiCD battery in a Goalzero Guide 10 charger.
Lastly, how many batteries are you going to be needing to charge? Our example is four.
Hours of Sun Available –
The sun generates rays that reach the earth. Harvesting those rays and converting them into electricity is the key. The fewer number of hours the sun is available, the higher the harvesting capacity the solar panel system needs to have. If you have 12 hours of sun per day that is efficiently reaching your solar panels that is great. But, if you only have 6 hours, then you need at least twice the harvesting capacity in your panels.
But, before you worry about that you have to know that total power needed to properly charge a single AA battery. This is only for “rough calculation” purposes, there is an entire science behind the scenes that we won’t go into. So generally speaking figure 1 – 3 hours of sun per battery at 7watts. We have to charge four batteries. If we are going to charge them all at once we need a 4-slot charger connected to a 28w solar panel system working for 2 – 3 hours. That is all under ideal/optimum conditions. There are many factors that can reduce the efficiency of the charging rate. An option would be a 14w system charging for 4 – 6 hours of sunshine time, potenitally up to 8 hours if charging NiMH batteries. A 7w system would need 8 – 12 hours minimum, maybe much more. Remember, perfect conditions rarely exist.
However, you may also only have partially discharged batteries that only need partial charging. But, occasionally you may want to “condition” your batteries to extend their life and improve their charge delivery efficiency. So you have to allow for the discharge process, then charging them fully back to maximum. Some folks would call this, “clearing the memory.”
I don’t recommend any solar charging panels less than 14w. Anything less than 14w doesn’t allow for anything other than ideal conditions. I like the Sunkingdom solar panel system, a 19w system. The unit can handle two battery chargers at once if needed. The unit’s built in SmartTechnology (IQ) can vary the power delivered to the USB ports to maximize the battery charger efficiency.
As a basis of comparison: The Sunkingdom solar panel unit is nearly three times more wattage than the Goalzero Nomad 7 unit. And the Sunkingdom’s full price is 33% less expensive than the Goalzero unit. And last I looked Amazon had the Sunkingdom on sale making it half the price of the Goalzero unit. More than twice as powerful at half the price…a no brainer.
I will hold off on a “fixed-loaction” option for a day or two. For now you have some great options for portable solar power units and AA & AAA battery chargers.
Solar Panel Unit Comparison Chart –
Battery Charger –
If you are only using NiMH batteries then the Sunjack unit is a great choice. If you are going to use, or potentially use NiMH & NiCD batteries then go with the PortaPow unit. The PortaPow unit also gives you the discharge/recharge clearing capability (memory affect). If you are going to go with a NiMH or a Lion battery (a.k.a. Li-Ion, LIB, Lithium-Ion) then you need the XTAR unit.
Note: The Goalzero battery charger (Guide 10) is a 1st generation battery charger that is not capable of properly charging NiCD batteries and has no auto-shutdown capability. That, coupled with a poor warranty and extremely high price I would not buy the Goalzero Guide 10 battery charger. The Sunjack is a more advanced battery charger at 1/3 the price of a Goalzero.
Solar Power Panel Unit –
I really like the Aukey BP-P4 21watt unit. It has a power sensing/sharing 2-USB port delivery system allowing you to run two battery charger units at the same time. It has the highest “efficiency” rating on its panels and protects its controller unit really well. On top of everything else it has the best warranty of all the units tested.
Note: The Goalzero Nomad 7 unit is an “old technology” unit. It has only 1/3 the wattage rating of the Aukey unit while costing 40% more. The warranty on the Goalzero unit is also only 6months vs. 2 years on the Aukey unit.
Bottom line & Ultimate Combo –
Hook up the Aukey BP-P4 solar panel unit to two PortPow battery chargers and you are good to go! Yeah, charging up to 8 AA or AAA batteries at a time, keeping those batteries properly conditioned, and not spending a bundle of money doing it.
Note #1: I never stop testing. If I find a better solar unit or a better battery charger unit for charging AA & AA batteries I will get that info posted.
Note #2: If you purchase either the Aukey or PortaPow items by clicking on the Amazon icon above I will make a small commission on the sale. Any and all the money I make through any potential commission will go right back into testing emergency preparedness equipment for reviews that are posted on this website.
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