I have some (cheap/old?) batteries that I need charged. The problem is, the chargers I have keep charging them until they get overcharged and lose their capacity. I already ruined 4 1800mAh-batteries this way, and after inserting new batteries it seems to do the same thing to them.

However, this is a pretty advanced (used) charger, LaCrosse BC-900. I wanted to try out Maha MX-9000, but I saw bad reviews of it on the internet (temperature sensing does not work, batteries leak when charged even more easily than on the BC-900). I bought a $37 Chinese charger that charges via voltage cutoffs: that seems to work fine; however, I cannot test the capacity of the batteries. I looked into getting a Hitec charger (X1 AC Plus seems like a decent one), but there you have to set cut-off voltages yourself: there is no "battery full" detection.

Obviously I am missing something. Are there no chargers on the market that can, at least, do DeltaT "battery full" detection? That's the main thing I need for my batteries, and I already spent quite a bit of money without results.

EDIT: I ended up trying both Maha and LaCrosse charger; the following is a review for those who might read this thread in the future.

Bottom line: the LaCrosse is hands down the better charger for >1000mAh-batteries if you do not know what you're doing. On the other hand, if you are willing to sit there and monitor the batteries, then the Maha offers more versatility. I read several reviews comparing the charger, but they all seemed biased one way or another (e.g. a person whose batteries leaked by Maha obviously was biased toward LaCrosse). I thought I would do a fair comparison of both, to help me know which to use when.

So first, there are the purely cosmetical differences:

  • When inserting batteries into the LaCrosse, you have to set the charging amperage (up to 3 clicks), and also whether you want it to charge, discharge, cycle, or multicycle. So 5 clicks is generally enough to set the process going. On the other hand, using the Maha you have to start with the default setting, and scroll until you find the setting you want, click enter, for the charge mode, charge amperage, and discharge amperage. Then you have to repeat this for every battery, since Maha not only does not remember the previously used settings, but it does not even remember the setting used for the previous battery. This means over 50 clicks are usually required to start the process going.
  • Also, the Maha has this bright LED which cannot be turned off, and illuminated the whole room so bright I cannot sleep at night (since its charging takes more than a day). Wonder how much electricity it takes. But of course it can be covered.
  • The Maha detects internal resistance before charging. It does not show it to you, but says "HIGH" if the battery should not be charged. According to the manual, this only happens when the battery is not rechargeable or it has too high a voltage: something that you can see on the LaCrosse by yourself anyways.
  • Finally, the Maha displays the charging capacity for modes other than "Charge". While this capacity does not get stored (so you have to be there when it finishes charging to see this capacity), at least you get to have an idea of how efficient charging is, and also approximately in how long it will finish. (note: charging capacity is 14-20% higher than the discharging capacity).

When deciding whether I want to get Maha or LaCrosse, I read the reviews which stated that Maha's "delta T detection for termination of charging" does not work. This one person wrote that Maha charged his batteries so much that they leaked. For this reason I decided to stick with the LaCrosse; but when the former did not work out, I decided to give the latter a try. I would say his review is not far from the truth. I inserted my batteries into Maha and went to church. After coming back, it said charged. Then I decided to switch slots to see if I got the same capacity charging them in reverse slots (i.e. if the slots are balanced). But, the Maha showed me both batteries were over 2.2 V (!)(exact voltage depending on the battery), and then showed "HIGH", i.e., the voltage is too high for it to do anything to the batteries. OK, Maha, but why in the world would you charge them to that voltage in the first place? Isn't there like a voltage cutoff? Apparently it was waiting for the negative Delta T or Delta V, and it just didn't happen because the batteries are Chinese quality. The manual says that if this detection is incorrect, the "discharge" mode does not do resistance detection, and so I can discharge the battery therewith first, and then run my charge-discharge-charge cycle. No thanks, Maha: I think I will leave these batteries for the next charger I'll test.

On the other hand, the Maha has this functionality called break-in mode. This mode was designed for making the batteries with slightly higher capacity remember only a certain amount of it, to make sure all batteries would get about the same (albeit lower) capacity, to prevent reverse charging when inserting many batteries in series. However, the way it specifies it does it is, apply a current equal to 0.1C for 16 hours (and more). Since battery capacity can be chosen from 500mA and higher (in 100mA increments), effectively what this means is, you can get to choose the charging amperage in *10*mA-increments, starting at 50mA-- if you are willing to sit there and wait for it to hit your desired voltage. (which in and of itself is pretty annoying, since it takes several clicks [read: physical access to it, no more using the socket under the bed] and about 40 sec of waiting to see the voltage, since every time you click it restarts at MAh, and Volts is last.) But, if you have low-capacity batteries (say 500mAh or lower) and have an idea of the cutoff voltage, then this is worth it: since this is in stark contrast to the LaCrosse, where no matter how hard you try-- you cannot charge it slower than 200mA.

So those were the highlights; now, I will compare its charging capabilities one at a time:

  • Charge/discharge: Maha gives the option to charge from 200mA to 2000mA, in 100-mA increments. LaCrosse only gives the choices 200mA, 500mA, and 100mA (a few more choices depending on the model). The other limitation in LaCrosse is, the discharge rate has to be half the charge rate, and you have to set the maximum rate that will be used within 7 seconds or so of inserting the batteries.
  • On the other hand, Maha displays the capacity, amperage, time, and volts in 2-second increments, and moves from battery to battery. So if you would like to monitor just the volts, that is not possible; also, staying just on one battery is not possible. You can click a button to choose which battery you would like to see, but you have to wait until it displays the number you want (e.g. voltage); also, after displaying that number it cycles on to the next battery, and you have to click thrice to choose your battery again. The maha displays all 4 batteris' status, and you can choose which number to see and to stay on.
  • Cycle: The LaCrosse cycles Charge/Discharge until the battery stops gaining capacity (which would vary from battery to battery); the Maha cycles a set number of cycles. Also, Maha's "top-off charge of 100mA", which sounds like a great idea for almost-charged batteries, and the reason I thought it would do better than the LaCrosse, does not seem to turn on. I've monitored my batteries for about an hour before they finished charging, in 5-minute intervals: and I have not seen the charge switch to 100mA even once. You would think it's time to top off if the charge hasn't went up for an hour... Maybe for really-fast charging modes this turns on at some point. On the other hand, Maha lets the batteries rest an hour between discharge and charge, which tends to be better on the batteries. In particular, without the 1-hour break the low-capacity batteries tend to lose about 4% charge each cycle; this does not happen with the Maha. After finishing cycling, on the LaCrosse you see only the last capacity; on the Maha you can see all of them. It is a little unfortunate that the Maha displays this only at the end-- it would be nice to know the capacity is going down so I should stop cycling, before finishing all the cycles.
  • \$\begingroup\$ The way I understand this guideline is, "recommendations for specific products" means I give a product and ask for recommendations of it, kinda like asking for reviews. Asking this type of information would become obsolete quickly because there exist many good products, places to buy them would change, and stackexchange does not wish to keep a review for every product out there. \$\endgroup\$
    – Alex
    Jul 14 '14 at 15:34
  • 1
    \$\begingroup\$ What I am doing is, asking for any good charger. This information is NOT "rarely useful to others", and will NOT become obsolete quickly, since new chargers tend to come out no more often than once per several years per company. In particular, I searched a long time for this information (upwards of 16 hours), and had to resort to asking this question on stackexchange. \$\endgroup\$
    – Alex
    Jul 14 '14 at 15:34

I've had good luck with Maha chargers. The key things you want are pulse charging and a separate charge circuit for each battery. Cheaper chargers only measure the charge on 1 of 4 or 1 of 2 batteries, and unless they are all have exactly the same capacity and charge level, you either under or over-charge some of the cells in a group.

Most of Maha's chargers do both of those things, but read the descriptions. If you're in the US, you can order Maha chargers from Thomas Distributing.

As I recall, their website includes a detailed description of each model that they sell.

  • \$\begingroup\$ Thank you for this information. As far as I am aware, all the chargers I tried have pulse charging, and have separate circuitry for each battery (in fact display the voltage of each battery). \$\endgroup\$
    – Alex
    Jul 14 '14 at 15:30
  • \$\begingroup\$ As I mentioned, Maha was the charger that I was getting ready to try next. The thing that stopped me was, some people posted that their "delta T monitoring for ending charging" (only present in MX-9000) failed to work because the sensor was too narrow to get the battery temperature accurately. Do you know for sure that the MX-9000 stops charging once the battery, say, overheats? Without displaying the battery temperature, there's no way for me to know for sure that it checks it. Maybe the charger the person claimed was leaking his (cheap) batteries was just defective? \$\endgroup\$
    – Alex
    Jul 14 '14 at 15:33
  • \$\begingroup\$ @Alex, For a healthy battery, measuring the battery voltage between charging pulses is a perfectly adequate way to avoid over-charging. My older Maha charger does not have a temperature sensor, and I've never melted a battery in it. I tend to by either Maha or Eneloop batteries though, not cheap off-brand cells. My guess is that the posters reporting melted batteries had defective cells, and that for some reason the battery did not make good thermal contact with the charger. \$\endgroup\$
    – Duncan C
    Jul 16 '14 at 21:15

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