Tenergy TN294 4-Bay 9V Li-ion Battery Charger + 4pcs 9V 600mAh Li-ion Rechargeable Battery

I purchased Tynergy Rechargeable Batteries in most types, but another brand charger that qualified use for specific battery types. I could not get it to charge the 9-volt batteries at all or to hold the charge on the other batteries. I decided to return the other brand and order Tenergy Chargers to use with their brand. They charged immediately and are holding the charge. One step closer to surviving successfully a power interruption.

With a Taylor guitar Expression preamp, tried NIMH rechargeables, which apparently often charge to more than 9v, which caused preamp distortion. A question to Taylor confirmed this - over 9v will cause distortion. A question to Tenergy confirmed that their Li-ion batteries will always charge to slightly less than 9v, and, these work great - no distortion and last about as long as a regular 9v battery. The product itself - the recharger and the batteries, seem high quality.

I'm a big fan of these 9V batteries. I'm an electrical engineer and I like to have some cheap multimeters that I can just leave active to keep track of how tests are going. Leaving meters on for days on end kills batteries pretty fast, so I bought a set of these so that I can just swap batteries out, recharge them, and keep going. So far I've put a few cycles on these and they're doing just fine. I even bought a set for myself to use at home. The charger runs off a 12V, 500mA DC jack with a 5.5x2.1mm center positive connector, which is super common and easy to replace if needed.They do self-discharge in storage, faster than an alkaline or non-rechargeable lithium battery. You can still use them for applications like smoke detector or alarm clock backup batteries, you'll just need to do battery maintenance more often than with a traditional 9V battery. The other thing to be aware of is that they take like 9 or 10 hours to fully charge when they're completely dead. Not a big deal, but be sure to leave time for it.

I purchased this Tenergy charger with four 9 volt Li-on batteries. I had previously purchased another more expensive brand, packaged set, with USB charger from a different supplier. I wrote a favorable review and failed to thoroughly test each battery under load with a Fluke multi-meter. I will not make that mistake again, AND I have updated the review on the more expensive brand AND charger to reflect the defects I found. Upon arrival, these Tenergy 9 volt Li-on batteries measured as follows: (3) batteries approx. 7.8 VDC, and (1) measuring approx. 2.8 VDC. Naturally, I suspected the battery reading at 2.8 VDC. However, after charging, all (4) batteries tested normal at approx. 8.4 VDC and held a charge without dropping more than a couple millivolts over four days. All batteries preformed very well under load tests, and in actual service in my wife's "tens unit". Where as previous batteries had to be recharged after four hours service, the Tenergy batteries last two days at high output. Great Stuff! Also, I highly recommend purchasing a dedicated charging unit with a transformer power based power supply like the Tenergy package. I have found chargers made to use a USB port to charge the batteries insufficient and unpredictable to say the least.

Mom uses a TENS and has for 20 years off &on. Her batteries were only lasting about 4-6 hours, and had single outlet chargers, so we had to take up 6-8 outlets, had no "charged indicators," so probably overcharged, This is fast, will not over-charge, an indicates when it is charged -- and all using only one outlet! I love this , and have saved me time and outlet space.

I use my tens unit daily and the expense of replacing batteries is crazy so I purchased rechargeable batteries instead . My first three charging docks never charged batteries at all. I finally saw this unit and decided this would be my last shot and I can’t say enough it works great and charges batteries quickly ! Would definitely recommend

I'm quite happy with this so far. If these work as well as the AA and AAA counterparts, then I expect to be fully satisfied.Personally, I wish 9 Volt batteries had become the default battery for our devices. The 9 Volt battery is much less prone to leaking. I've about given up on normal AA and AAA alkaline batteries, especially those made by the copper top company. /end rant

Well let's just say how can you go wrong! All my tenergy products work very well. Batteries and chargers