Tenergy Centura 9V and TN141 mini review - Page 1
Forum section: electronics / general

author: Rick Law
author_rank: Super Contributor
timestamp: March 17, 2013, 11:43:32 pm
content: Mini-Review for the Tenergy Centura 9V and TN141 (2-bay) chargerSince a good number ofDMM uses 9V battery, I am sure I am not alone in thinking of using a recharge battery. I have two main reasons to choose a recharge: (1) When data logging, I want to make sure that the battery goes the distance. Inserting fresh primary battery each time is costly. (2) Corrosion - on a few occasions, I forgot to turn off the equipment. A half dozen times or so, even “quality batteries” like Duracell leaked on me and make a mess inside the equipment. With NiMH, I may “drove it negative” and damaged the battery, but I have yet to have one of them leak on me when I left the equipment on for weeks.Selection for 9v LSD (low self-discharge) NiMH is limited. With some apprehension I selected the Tenergy Centura. I read in a review someone complained that his Centuradoes not fit his guitar. So, with apprehension, I ordered a couple of Centura 9V and the TN141 charger. Below is a mini-review of the batteries and the charger.The Centura 9V LSD BatteryPrefix:First, let me address the“does it fit”aspect. Yes, it fits the UT61E but it is a squeeze. The Centura is a 7-cell battery verses the typical 6-cell 9V battery. Consequently, it needs more space for the extra cell. It gets the extra space by making thebody taller and the power-connecter buttons a bit shorter. The total height is exactly the same as other 9V batteries. From theattached photo, you see that the body is about 1.5mm taller and the buttons are shorter by an equal amount. The UT61E compartment has a separation between the buttons and the battery body, but the body-side of the compartment has enough room to squeeze in the extra 1.5mm, and the shorter buttons still stick out enough for a good electrical contact. It fits the snap-on power connectors just fine, so if that is what you DMM/equipment uses, you have no worry here.About the battery:The Centura 9V LSD nominal spec is 8.4V, 200mAH when discharged at 40mA to 7V with a claimed “over 1000 charge cycle” life span. Tenergy website did not post any numbers for charge-retaining over time, but I have seen sellers’ web posting at 12 months - 85%, and I have read reviews on it retaining merely in the 65% range in 12 months.This mini-review does not contain any charge retention test.Both batteries from the two-pack appear fairly well constructed with one exception: the clear plastic covering were not shrunk as far as it should. You can see some spots where the plastic wrapping has slack wrinkles. Apart from this small detail, the batteries look and feel very well constructed. They look solid and well made. (They are made in China)Unlike many 9V recharge batteries with 6 cells, the Centura is a 7-cell NiMH. So it delivers 8.4V nominal instead of 7.6V for the 6-cell batteries. They claim that with 8.4V nominal, it can deliver more useful power as more power can be delivered before the cut-off voltage for whatever it is powering.The Tests:I did the same tests on both batteries each with 5 discharge (and charge) cycles. First theinitial fast dischargewith the batteries as received (without topping up), then I didtwo “fast and slow” cyclesof firstfast dischargethen recharge and do aslow discharge. That is 5 discharges for each battery. The batteries were discharged to just below 7V and then recharged for the next run.The fast discharge was done at just over 1/3C (~60-80mA) with a119ohm dumb resistor. The slow discharge was done at around 1/10C (~20mA) with a440ohm dumb resistor. Since the load is a dumb resistor, the current varied with the voltage.Battery 11. Fast Initial: 134mAH (1115mWH), Duration=1:552. Fast Discharge: 203mAH (1735mWH), Duration =2:493. Slow Discharge: 214mAH (1855mWH), Duration=10:524. Fast Discharge: 210mAH (1806mWH), Duration=2:555. Slow Discharge: 215mAH (1884mWH), Duration=10:48Battery 21. Fast Initial: 140mAH (1159mWH), Duration=2:012. Fast Discharge: 204mAH (1735mWH), Duration =2:523. Slow Discharge: 208mAH (1803mWH), Duration=10:524. Fast Discharge: 203mAH (1726mWH), Duration=2:515. Slow Discharge: 215mAH (1877mWH), Duration=10:48Thedischarge curves are attached.As the number shows, both batteriesarrived with about 70% full. After the first full charge, they meet and slightly exceeded the spec (spec is 200mAH at 1/5C – even at 1/3C, the numbers are 203 and 204mAH). When discharged at 1/10C, it is well above 200mAH at 210mAH and 215mAH.The Centura(s) perform to spec and exceeded it (slightly). They claim that with 8.4V nominal, it can deliver more useful power. My tests show at 1/10C discharge,94%-96% of the energy were delivered before it dropped below 8V(seeattached graph). I did not do a complete graph for the higher 1/3C discharge. I did the calculation for one of the four 1/3C discharge:92%of the energy was delivered before it drops below 8V.Thus far, I am pleased with the batteries. The UT61E drains at around 5mA. Now I know if I top up the battery, I can have a 40 hour run. This is much less than the 400-500mAH typical primary cell delivers; but when a battery is already in use, I can never be sure how much of that 500mAH is actually there and fresh battery every run is expensive.The draw back:Discharging a rechargeable battery to well below 1V per cell is not a good idea. It will damage the battery in the long run. The UT-61E low battery warning is around 5V. Given the low drain (5mA) of the UT61E, I am not sure how quickly it will drop the battery from 7V to 5V. So the battery may beheld at below 1V per cell for a lengthy period of timewaiting for the low battery warning to come on. I cannot test this without potentially damaging the battery. With an enclosed battery compartment as the 61E is, checking the battery voltage is inconvenient.The TN141 chargerThe charger is very small with a flip out plug. It measures merely 85mm by 65mm wide chopped-off-oval shape and about 25mm high. It is a 2-bay charger at 100mA charge rate. The two bays are independent each delivering 100mA. The termination method is “negative-delta-V” with a 5 hrs safety timer. It has reverse polarity detection, short circuit, and bad battery detection.Each bay is equipped with a multi-color LED.REDmeans charging,GREENmeans done charging. When it detects reverse polarity, short circuit, or bad-battery, it will blink RED. I have seen it onAMBERand I am not sure what it means (more on this later).Testing the charger:The charging is uneventful and worked well. With it being so uneventful, I decided to charge a full battery. The RED turn GREEN in a few minutes reassuring me that the NDV termination is working properly.Pulsing charge:In fact, the charger exceeded expectation. At the low price of under $10 including shipping, I was expecting a dumb-smart linear charger. It actually is a pulse-charger. Itpulses at 250mA once every 2 seconds(or so) averaging 100mA. Once fully charged, the pulse drops to about once every10 secondsto maintain the charge. I have not left the battery on it long enough to say if there is cut off time.Gone milli-volt or Driven Negative:To test how it behaves with a marginal cell, I use 6AA to simulate a 9V battery. I have a 4 AA cells that “gone milli-volt” each sitting at under 100mV; another 2 AA cells that were driven negative. I set them up in a series to simulate a single typical 6-cell 9V battery. Together, the pack measures at about 200mV.The TN141 started with a3mAsteady current. After it got the pack up to around 6V, it switched over to pulse the 3mA.At around 8V, it switched over to normal charging of 250mA pulse every two seconds. I did not expect the pack to fully charge with a single run as the capacity well exceeded 500mAH. The safety timer would stopped the first charge run at around 500mAH (5 hours). But during the testing, it was restarted a number of times to test the voltage. The pack eventually charge fully.When a 6-cell/7-cell battery gone negative, there is not much point in trying to revive a battery. With one or two cells sitting negative, the battery probably can’t hold much charge or deliver much punch. The cell is likely too damaged to use. But this test shown one can easily jump-start the battery from negative to milli-volt and the TN141 will take it the rest of the way. Once it is fully charged, one can then tests the battery to see if it is worth keeping.LED on AMBER:I noticed during one of my test cycles, my battery#2 shown an amber/orange light upon completion just prior to dinner. Since dinner was waiting, I could not do much checking aside from measuring the voltage which was at a typical voltage for a full (or almost full) battery straight off the charger. After dinner, I used the battery a bit and it all seemed normal. I recharged it and the LED was GREEN.During that AMBER cycle, I was also doing something else and used an extra wall-wart. The TN141 was sitting directly on that wall-wart and that wart was running fairly hot. I am not sure that was affecting the charger. In any event, I have not been able to reproduce the AMBER light.Conclusion:So far, I am happy with the Centura(s) and the charger. Unlike many other Chinese made batteries with exaggerated claims, the Centura’s actually exceeded spec. The charger worked fast and worked well. I will monitor these for long-term performance and update if anything interesting happens.

author: saturation
author_rank: Super Contributor
timestamp: March 20, 2013, 09:17:08 pm
content: Thanks for the great data. I have reviews of the Tenergy Centura 9V in the archives; I've been using them for ~> 2 years, and recently bought a box of 10 to replace due for replacement primary 9V.I do not have as hard data as yours for the long term discharge rate, but the rate is logarithmic and the slope is near 0 in about 4 months. Compared to standard NiMH with near 1-3%/day self discharge, they are spent in 3 months, and will give a low bat warning in about 6 weeks.Tenergy Centura 9V are a definite. There are few makers of 9V LSD [ eneloop does not have 9v AFAIK], the other reputable maker is Maha and they cost >2x more each but are rated for 250mAH or 230mAH.Beside T&M gear, I use one in a water alarm, and a primary battery lasts 4 years. So far, 1 yr on the alarm and all is well. I anticipate changing in every 2 years, regardless.

author: mariush
author_rank: Super Contributor
timestamp: March 20, 2013, 09:43:28 pm
content: Nice writeup and review.Otherwise, it's a bit funny how you're testing with the UT61E...Martin tested the battery consumption and the meter was working fine way below the battery low voltage indicatorhttps://www.youtube.com/watch?feature=player_detailpage&v=P_h27mRCH6s&list=PLB46F445E454CD696#t=1064sIf it doesn't jump automatically, go to 17:47As you can see it actually uses around 2.3mA with jumps to about 3.7-4.5mA when reading resistances and it went down to 2v before drifting.

author: Rick Law
author_rank: Super Contributor
timestamp: March 20, 2013, 10:02:20 pm
content: Quote from: mariush on March 20, 2013, 09:43:28 pmThanks - I benefited much from other's sharing their experience. So I must return the favor by share my experience with others.Quote from: mariush on March 20, 2013, 09:43:28 pmRegarding the “testing it on the UT is a bit funny” part, I agree. The UT61E works down to such low voltage that makes the DMM itself an almost perfect NiMH killer. It will drain the last drop of charge (almost the last drop?), which may drive the battery to below 1V permanently.The question is how fast does it drops from 7V to 5V (low-battery indicator on) with the Centura in the UT61E (drawing merely 2-5mA). If it goes quickly, it should be fine for the battery. If it takes a while, it won’t be healthy for the Centura.While my batteries are new, I will baby them a bit and not intentionally put them in danger just to test the duration of the 7V to 5V drop @2mA.Rick

author: Rick Law
author_rank: Super Contributor
timestamp: March 20, 2013, 10:10:20 pm
content: Quote from: saturation on March 20, 2013, 09:17:08 pmArgh... Too bad my search did not find your review! Knowing someone complained that the Centura 9V doesn't fit his guitar, I ordered the batteries with a good bit of apprehension. Good that it worked out.I should go look for it now. I may learn something.ThanksRick

author: mariush
author_rank: Super Contributor
timestamp: March 20, 2013, 11:07:33 pm
content: Quote from: Rick Law on March 20, 2013, 10:02:20 pmIt shouldn't be that to glue a small pcb inside the meter which would monitor the battery using an adc or an opamp or something and disconnect the battery through some method.Even if going hardcore the microcontroller route, it would only need to poll the battery once every 10-20 minutes and then go in deep sleep so we're talking about a few uA of constant power consumption (both mcu and its ldo).

author: saturation
author_rank: Super Contributor
timestamp: March 21, 2013, 04:33:03 pm
content: The posts I made were fairly brief but without charts or graphs; I think your review is now the definitive one with data.One thing few discuss about NiMH chemistry is the actual calendar life of a battery apart from the cycle life.I have AA going past 7 years at 50-60% of its virgin mAh but none of them were charged properly, a key is charging mustneverrun 'hot,' <<< 45oC, I use typically <= 38-40oC. The Tenergy 9V charger does keep to the temperature limits.Cells I use with the improved charging method shown ~ no deterioration in mAh since 5/2010; I use the Maha C9000 charger; these cells are Ultralast, eneloop and Tenergy Centura brands. Further the 7 year old batteries have minimal reduction in their 50-60% mAH given the improved charging scheme.OTAH, when I obtained the Maha's competitor charger, a La Crosse, it included a new set of AAx4 and AAAx4 NiMH cells 'free of charge'. Some of these cells have lost > 30% of their mAH in 3 years used as often as the other cells; reconditioning them did not restore their full Ah.For best results, mAH must be based on the IEEE protocol, prior to the Maha C9000, doing your own IEEE protocol was very tedious. Note, Maha is standardized only for 1.25V cells.Other potential advantage of these LSD Centura, is they could last >>> 7 years. Calendar life very likely depends on the quality of construction. Another is that after over 20 years of use with the standard design [and assuming quality made cells], I've never had a NiMH cell leak.Quote from: Rick Law on March 20, 2013, 10:10:20 pm

author: Rick Law
author_rank: Super Contributor
timestamp: March 29, 2013, 01:40:48 am
content: Additional information update – how long does it take for the UT61E to take the Tenergy from 7V to low battery warning.I was concerned about the UT-61E's low battery warning being at 5.6V which means the NiMH battery may be sitting at low voltage (below 7V) for a long time. It exposes the battery to "going negative" or "going milli-volt" damaging the battery. So, I did not test how long it will actually take from 7V to 5.6V as I wanted to avoid possible damage to my new battery.My Tenergy Centura 9V ran down to 8.15V. From my prior tests, I know over 90% of the energy was discharged already. I thought: "Ah, what the hack, I will see how long it takes to go all the way down to low battery warning."Well, I did the test. It took less than 1 hour on light use for it to drop from 8.16V to 5.6V triggering the low-battery warning. That is good. This "drop like a rock" prevents the battery from staying low for a long time – thus reducing the risk of possible damage.The discharge graph is attached. Note that there was a very quick drop from 6.9V to 5.9V. I suspect one of the 7 cells just cut out and gone milli-volt. That drop is not a meter misread or a clock misread. I used time-lapse photo since the UT-61E cannot measure its own battery. With time-lapse photo, I have the luxury of review. I reviewed and rechecked the time-lapse photos at least 3 times to ensure the both the clock and the readings were right and a sudden 1V drop did occur.Assuming no cell dropped out and gone milli-volt and the Voltage-Drop continued on theprojected decline slope, it would have taken around two hours to go from 8V to 5.6V. Such short discharge time (even if distributed over a long calendar time) should not (I hope) cause too much damage to the battery.With possibly 1 of 7 cell dropped, I recharge the battery to about 9V (not full). Now I will check to see if the voltage hold or that cell is damaged…Rick