Rechargeable "Crown" repeatedly overlooked in the muska. And in each there is some kind of ambush. Accordingly, I continued searching for the “ideal”, and it seems I did find it, although it was not without drawbacks.
Actually, I bought several Akums. Verified znter, review of which has already been, and more than once, well, and the "dark horse" from the title.
The selection criteria are simple: USB charging, higher capacity, smaller self-discharge. Ideally, these should be two banks connected in series with a charge / discharge / protection controller and a step-up charge. Such a constructive gives continuous advantages in the case of application in the tester: a complete absence of interference, long-term operation without recharging and a regular display of the battery discharge symbol.
When is a battery with an overpaying obviously worse? But for example a smoke detector. In the case of this Akum - the detector will begin to squeak when discharging. In the case of a crown with a boom, it will quietly fall asleep when it turns off.
About the need for a battery in principle. Even after I used auto shut-off in ut61e - it still drops the batteries noticeably faster than for example my68. In this case, the usual crown was enough for a year, alkaline for a couple of months longer, so I put simple ones - this is more reasonable, because a multiple increase in the cost gives an extremely insignificant increase in working time. And in ut61e, there is usually enough for three or four months, up to six months (up to a year in alkaline), while I use it less. At the same time, the service life somehow differs quite strongly from battery to battery, although I buy them the same in the same place. The cost of simple batteries is 0.5 dollars for us, an alkaline is about 1.5, that is, this crown will pay off in a couple of years and there will be no need to keep mountains of batteries in case you need to go somewhere suddenly.
I will begin nevertheless with ZNter. Actually, there is nothing to add to the previous reviews.
Output voltage and no-load current:
Just like everyone else. The only thing I can say in addition to the previous reviews is that I checked the batteries on iMax and they showed amazingly accurate capacity, something like 485 with 500 mAh declared
Well, go to the "main dish". I did not photograph that the battery was delivered in a cardboard box with dimensions slightly larger than a matchbox - 7x4x2cm.
The voltage on arrival (and Akum drove to me EXACTLY for a month and unknowingly how much was still in stock at the seller) - 7.35V.
That is, Akum does not have any significant self-discharge that damn pleases.
When you click on the button - should sort of likelight up several LEDs depending on the state of charge. Alas, it is not. That is, I do not know how it was conceived, of course, but in fact they are all three burning, the first one is brighter, then dimmer, then dimmer. When Akum has sat down completely - the third LED does not light up, the second one is completely dim. When charging (by the way, it eats 180mA from the power supply) is similarly lit, there is no indication of the end of charging.
And this, in fact, the only minusReviewed device. Moreover, I consider the lack of indication of the end of charge to be an extremely important minus, because if the charge can be recognized by voltage, and few people will pull the battery from the tester, for example, to find out how it is there, then it is extremely important to find out if it has charged. Well, either put on the night for sure.
Banks 701937, capacity not specified. They are connected in series, three wires go to the board.
from the "large" we are present:
XR3403D 1.2MHZ ， 14V Step-up DC / DC Converter datashit
S8205A dual N-channel power mosfet 20V 6A RDS (ON) <37.5mΩ @ VGS = 2.5V datashit, or here
CGTJ lithium protection controller 2S suspected s8252 datashit. Overview of the protection board on a very similar chip and the circuit design in general. According to the datasheet, it has a current consumption of up to 8µA
Next, I put the battery to discharge a homemade load current of 100mA. Do not look at the voltage, the battery is connected with thin wires, even at this current there is a significant voltage drop on them.
I did not check the maximum current, but the 0.5A, which were initially installed on the load, did not impress the battery at all - I calmly gave it to them.
The battery is disconnected by the voltage protection board.5.6B (2.8 per bank), which I consider to be quite correct. As you can see, the capacity is noticeably less than declared (420 vs. 550 mAh), BUT! The competitors have even less! According to the AlexPoroshin reviews, the Znter has a capacity of about 350, and an okcell has a total capacity of 260mAh when measured at the output terminals. At the same time, with the “impulse” mode of operation, when the multimeter is switched on not in the morning or for the whole day, but in the process of operation for 5-10 minutes, and with a lower current consumption (100mA, what kind of multimeter eats) - probably will show even more
And while in the surveyed battery there are no converters on the output! Naked lithium, with a pair of dongles.
This is what the oscilloscope sees on a dead and slightly recharged battery:
Nicherta, he does not see there, which is logical - it is stupid two banks of lithium.
Let's sum up. The concept of IMHO is very correct - there is no extra electronics, which degrades the efficiency of the system and adds consumption to idle time and interference to the output.
And in the pros, though not very honest with us,higher capacity than competitors, lack of notorious interferences and ripples, lack of self-discharge, correct indication of battery discharge by standard multimeter tools (well, or where they will stick it).
But not without a spoon of tar. First of all, this is of course an indication. I don’t know - maybe this is a feature of my specimen, but I don’t think so. In this implementation, this indicator is completely useless. The second minus is charging. There is not used, as we see, the special microchip of the charge controller, only the boost converter and the protection chip, which does not control the charging process. Of course, I understand that, in principle, it is enough to set the output voltage of the converter accurately (and here after the end of the charge on Akum exactly 8.4V, so in this regard everything is not bad) and limit the current with a resistor, but I would like to see, for example, the balancing -No two consecutive banks. But alas. Another relative disadvantage is a slightly lower voltage than the battery. Sometimes it is critical, sometimes not. The same UT61e at a voltage of 6.5V battery icon has not yet lit.
In general, I am extremely pleased, for I found in principlewhat I was looking for - precisely in terms of concept. The capacity is lower than stated, but higher than that of competitors, but "clean output" and the lack of self-discharge. Which I tried to check by disconnecting from the battery the negative wire. ut61e showed something like 0.06 uA (hundredths of a MICROamper), which I consider to be a tip, not a self-discharge. By the way, something tells me that you can charge such a battery from the side of the connector, and not just via USB. But here I am not 100% sure.
For prices and all that. I chose this seller because at that time he had the lowest price, including delivery to Belarus. This is important because far from everyone sends lithium to us, plus the cost of shipping can be higher than to Russia. So where to buy - look for yourself.
In general, the battery initially did not produce the mosta pleasant impression - well, because the charge indicator was such that it would not have been better at all, and along the way, I liked it very, very much. More precisely, in my opinion, the advantages exceeded the drawbacks. Probably, I will take more. In the same smoke detectors here - why not?