Xtar XP4 charger gets warm?

[ohaya]

Hi,

I just received one of these today, and have it charging 3 Eneloop AAs, and I noticed that both the charger and the batteries are kind of hot. Not too hot to hold, but pretty warm. This is running of the power wall wart that it came with.

I had the current set to 0.5 amps earlier, and have just set it back to 0.25 amps, but was wondering if this is normal?

Thanks,
Jim

[Chloe]

Do you have a temperature probe? You can compare at least to the other chargers here . Many chargers seem to get ‘warm-hot’.

[ohaya]

@Chloe

Do you have a temperature probe? You can compare at least to the other chargers here . Many chargers seem to get ‘warm-hot’.

Hi,

No I don’t think that I have one of those. Would a regular thermometer (like the ones used to measure body temp) work?

Also, BTW, the XP4 doesn’t seem to charge a 16340 fully :(. It gets to about 4.11V, then says it’s done (now moved to my old Jetbeam i4).

[zelee]

ohaya is XP4 can really fit 4 x26650 at once?

[Chloe]

@ohaya

No I don’t think that I have one of those. Would a regular thermometer (like the ones used to measure body temp) work?

It might work, although I’d check the range first. Some can have a smaller range of operation than food probes.

[ohaya]

@zelee

ohaya is XP4 can really fit 4 x26650 at once?

I don’t think so. Two at a time seems ok:

Is it suppose to be able to do that?

[ohaya]

Another question: As mentioned, earlier, I had 3 Eneloops charging. Two of them finished awhile ago (like several hours), and I measured voltage about 1.39V+. The 3rd one was still charging, so I pulled it off the charger a few minutes ago and it’s measure 1.459V.

Reading the XP4 specs, it says cut-off voltage for Nimh is suppose to be 1.40+/-0.05V, so is this XP4 working ok?

[Chloe]

You can try putting the 3rd cell back in after cycling the power, see how long it takes to terminate just to be sure.

[ohaya]

@Chloe

You can try putting the 3rd cell back in after cycling the power, see how long it takes to terminate just to be sure.

Hi,

I PM’ed madecov, and he pointed me to a discussion over on the “other” forum, and comments by HKJ, among others. That thread linked to testing that HKJ did on the XP1, which apparently follows the same pattern. From what I can tell, with both the XP4, and XP1, the recommendation was to charge Eneloop AAs at the 0.5A rate, rather than the 0.25A rate. Apparently the XP1 and XP4 both have difficulty determining the end of charge, because they use dV/dT or something like that.

EDIT: From this comment on Amazon re. the BC-700, apparently even it (and others) have problems terminating when low current (yes, I’m now thinking about getting a separate Nicd/Nimh, since I’m using more Eneloop AAs since I got a new 3xAA headlight, and use it a lot):

http://www.amazon.com/What-batteries-recharge-Will-charger/forum/Fx2KDV1D4P0MCOF/Tx5U1CR5W0315N/1/ref=cm_cd_ql_tlc_al?\_encoding=UTF8&asin=B000RSOV50

Those 2300mAh batteries should charge up just fine in the BC-700. You should set the charging current to 500mA or 700mA (to avoid potentail charge termination problem at 200mA).

[tatasal]

For AA and AAA Nimh cells, Maha, the maker of the C9000, recommends a minimum of .33C to a maximum of 1C charging rates.
So an Eneloop 1900mah cell, .33C x 1900 = 627ma. The .25A rate is good for AAA cells.

I have always followed these rates in my C9000 and true enough, the heating comes only on the last portion of the charging, signalling the topping out of the charge.

[ohaya]

@tatasal

For AA and AAA Nimh cells, Maha, the maker of the C9000, recommends a minimum of .33C to a maximum of 1C charging rates.
So an Eneloop 1900mah cell, .33C x 1900 = 627ma. The .25A rate is good for AAA cells.

I have always followed these rates in my C9000 and true enough, the heating comes only on the last portion of the charging, signalling the topping out of the charge.

tatasal,

Thanks for that info. As mentioned, I haven’t used Nimh much, and up until now, have mostly been throwing the Eneloops into the Sanyo charger that they came with (in the Costco pack) and just leaving them there until the light changed (which seemed to take overnight usually), so this Nimh stuff is kind of new to me :)…

[Chloe]

I have not encountered this termination problem using my Shan charger, for AA it charges at 530mA minimum.

If the XP4 has problem detecting termination voltage, then it will be up to detecting temperature to stop charging, or timer (provided it has temperature sensor or internal timer).

P.S. This is a good read to understand so-called intelligent chargers:

BU-203: Nickel-based Batteries

[Bergtjie]

Personally , multi chargers are a jack of all trades master of none, except for decent hobby chargers.
I don’t use my i4 for NiMh due to termination issues, and have dedicated NiMh chargers.
I always charge my AAA eneloops at 500mA and AA at 700 mA, they can get a little warm depending on battery age during the termination stage.

[ohaya]

Still learning - as I said, I don’t use Nimh much.

I have a (Coast) 3xAAA headlamp that I’ve used for quite awhile, but on that, I was using a AAA Li-ion with 2 dummy AAAs.

Then, recently, I got a 3xAA headlamp, and since then, having been using Eneloop AAs a lot more. I’d been charging those in either the Sanyo 4-bay charger that came with earlier, then started using my Jetbeam i4, which was faster than the Sanyo charger.

Then, as I said, I just go the XP4, and figured I’d move to that, since it’s newer :)… So now, I’m setting it to 0.5 amps, and it’s ok.

I’ve been looking at 4-bay Nimh chargers like the La Crosse and Maha, but even now, I don’t use Nimh enough to justify a dedicated Nimh charger, so for now, it’ll probably be the XP4 (although I think it’d be cool to have one of those with the displays :laughing:…

[photon1k]

@ohaya

@tatasal

For AA and AAA Nimh cells, Maha, the maker of the C9000, recommends a minimum of .33C to a maximum of 1C charging rates.
So an Eneloop 1900mah cell, .33C x 1900 = 627ma. The .25A rate is good for AAA cells.

I have always followed these rates in my C9000 and true enough, the heating comes only on the last portion of the charging, signalling the topping out of the charge.

tatasal,

Thanks for that info. As mentioned, I haven’t used Nimh much, and up until now, have mostly been throwing the Eneloops into the Sanyo charger that they came with (in the Costco pack) and just leaving them there until the light changed (which seemed to take overnight usually), so this Nimh stuff is kind of new to me :)…

For chargers using -dV for termination detection, it isn’t the increase in heat, but rather the small drop in voltage (-dV) that comes with it, which signals the termination point. The heat increase is much less when charging at low rates (less than .3C) and the drop in voltage is much smaller, making it harder for the electronics to detect. That’s why Maha/Powerex recomends .3C or higher charge rates. I use a minimum of .5C because older cells with higher IR need a higher charge rate to produce a more easily detected -dV.
It is normal for NiMh cells to get warm/hot when being charged, which is just the opposite of Li-ion cells.

[tatasal]

Nimh chemistry cell naturally exhibit a sudden heating up and a small drop in voltage when fully-charged. The C9000 uses a combination of negative delta V, zero delta V, peak voltage, time and temperature to determing end-of-charge.

I use a .5C charging rate and .25C discharging rate.

[Chloe]

@photon1k

It is normal for NiMh cells to get warm/hot when being charged, which is just the opposite of Li-ion cells.

It is not good for Ni-MH to get too hot during charging. Warm is acceptable as they do warm up during charge. This is one of the reasons I wanted members to contribute charger temperature readings. Some Ni-MH chargers will cook your cells and ultimately damage them.

From Batttery University:

Charger manufacturers use 50°C (122°F) as temperature cut-off. Although any prolonged temperature above 45°C (113°F) is harmful to the battery, a brief overshoot is acceptable as long as the battery temperature will drop quickly when the “ready” light appears.

[photon1k]

@Chloe

@photon1k

It is normal for NiMh cells to get warm/hot when being charged, which is just the opposite of Li-ion cells.

It is not good for Ni-MH to get too hot during charging. Warm is acceptable as they do warm up during charge. This is one of the reasons I wanted members to contribute charger temperature readings. Some Ni-MH chargers will cook your cells and ultimately damage them.

From Batttery University:

Charger manufacturers use 50°C (122°F) as temperature cut-off. Although any prolonged temperature above 45°C (113°F) is harmful to the battery, a brief overshoot is acceptable as long as the battery temperature will drop quickly when the “ready” light appears.

I didn’t say it was good, I said it was normal. In fact I think it is unavoidable if they are well used or simply older. Just like I develop wrinkles around my eyes (and elsewhere) as I get older.

To quote your source:

Note that some nickel-based batteries heat up during charge and this is in part due to high internal resistance. Such a battery may be warm to the touch even though it is only partially charged.

I have some older NiMh cells with more than 200 cycles on them. They’ve always been charged on good chargers, at .5C or less. But they have seen heavy use in flashguns and some are getting towards the high side of warm when they reach termination. Some of those will not terminate reliably when charged at a .4C rate and have noticeably less capacity. When they won’t terminate at .5C I will probably dispose of them.

[Chloe]

I have some older cells like that too, and they get really hot charging them in dumb charger (none of my other chargers want to charge them). But they don’t hold charge for very long and have diminished capacity.