A while back I purchased this Tenergy Universal Smart Battery Charger as my primary battery charger. I did so for two main reasons: it has the capability to plug directly into a car’s auxiliary outlet using a provided DC plug and it can charge all manner of rechargeable batteries, from the common AAA- and AA-cells to C- and D-cell batteries and even 9-volt batteries as well. Though I currently do not have any rechargeable batteries besides AAA- and AA-cells, I do eventually intend to purchase several D-cell and maybe even some 9-volt rechargeable batteries in the near future.
My first impression after unpacking was that the unit was BIG or, at least, bigger than I had anticipated; in fact, it is two or three times the physical size of my previous battery charger. I’m not sure what I was honestly expecting because it does need to fit up to four D-cell batteries so it has to be much larger. Anyway, it’s now a permanent fixture on my countertop. 😉
Obviously, the first thing I wanted to do was to test it out. As I only had one battery that needed to be charged I had to scrounge up another one to test the unit because, unbeknownst to me, you need to charge batteries in pairs. Normally this isn’t a problem but there are some devices I own that use an odd number of batteries (my recent headlamp purchase that uses 3 AAA-cell batteries comes to mind) so this could be a slight annoyance at times. Since the initial test I’ve used it a handful of times without any trouble and quickly adjusted my “charging behavior” to charge pairs so it’s no big deal to me any longer.
A much larger annoyance is that the unit expects batteries to be the same capacity. As I have and use at least three or four different rechargeable batteries at any one time, this is a problem for me. While I usually use the same batteries in any one device, that’s not always the case such as with the batteries that end up in my kids’ Wii remotes. As such, if you use an assortment of batteries like I do then this is a huge detractor. If not, then no need to worry… just note this for the future.
Like I mentioned in the beginning, a major reason for buying this unit is that it can plug directly into a vehicle’s auxiliary outlet (or my small solar setup with a female DC adapter connected). So, assuming I can keep the car running, am on the move, or can use my solar system, then I can easily recharge batteries without any loss or need for an inverter. This ability isn’t critical but it more versatile than only having a wall plug, which means I have more options open to me should I need them.
How about charge time? Well, it all depends on what’s being charged (AAA, D, 9-volt, etc) as well as the battery capacity. I’ve found that a typical rechargeable AA-cell battery that I use takes about two hours to charge. This is actually quite a bit slower than my previous charger but it’s my understanding that a slower charge is supposed to be to better for battery life. That said, there is such a thing as way too slow of a charging time and having to wait several hours to charge a pair of AA-cell batteries is likely too long to wait. So, no more than a few hours seems to be the recommendation for a typical AA-cell battery (note that something like a D-cell battery will take a lot longer because it has a much larger capacity).
Overall, if I had to purchase this charger again I probably would not do so for the simple reason that it’s not as “smart” as I would like it to be. While I like the fact that it can connect directly to a DC adapter and I like that it can charge D-cell and even 9-volt batteries, I really don’t like the fact that requires me to always charge the same size batteries in pairs. Though I can deal with the requirement I just don’t like it. Of course, there are benefits to Tenergy Universal Smart Battery Charger that could make it useful as an good emergency charger but as my primary, I think I’ll eventually find something better.