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Old Apr 28, 2003, 5:40 PM   #11
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Any charger putting so much energy into a component so small as an AAA in such a short time might be viewed with some curiosity - how does it differentiate between AAA's and AA's?

Thermal sensing for full charge should be the regarded as the back stop last resort, since it is difficult to get consistent good thermal bonding between any battery case and sensor. This is why proprietary battery packs have the temperature sensor and a third wire 'built in'. Alternatively, if they are relying on an air temperature sensor, which I have seen, leave the lid open on the box and your batts and possibly you get fried unless the safety timer cuts in.

Any battery which is so hot to handle will be at an even higher temperature at the core - and that is worrying. Batteries usually carry a 'do not incinerate' warning. I think we can guess what might happen!

However, in Steve's defence, he is not responsible for carrying out product safety testing - I would have thought you had agencies for that in US and it's the manufacturers who satisfy 'fit for purpose' tests - not Steve. Also Steve publishes the manufacturers specs and claims, but it is unreasonable for him to test every claim and some things must be taken in good faith until shown otherwise.

In UK a valid complaint to a trading standards agency, can get a product banned or recalled for modification at cost to the manufacturer. Didn't one of your car models explode when hit from behind due to bad positioning of the fuel tank, and weren't there some makes of tyres with a similar bad safety record?

Steve has now added a further comment to his review. Even so, I'm not sure I'd want to leave one of these things plugged in while I was away from my house, it seems it's not like an air freshener!

Has any complaint been made to the product manufacturer and a reply received? Bit unfair to not allow the option for comment. If the product really is dangerous, other purchasers need to know. Pity they made such frequent references to AAA's. But then I guess many other chargers have the spring loaded sliding contacts as well.
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Old Apr 28, 2003, 6:22 PM   #12
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>>Any charger putting so much energy into a component so small as an AAA in such a short time might be viewed with some curiosity - how does it differentiate between AAA's and AA's?

It does not. However when you read the advertising, it would make you think that it has some magic technology to prevent creation of heat.

>>Thermal sensing for full charge should be the regarded as the back stop last resort....

I fully agree. The heat has to penetrate following layers:
- air gap between a battery and charger housing
- material of the charger housing
- air gap between the charger housing and the sensor

Obviously this is not going to provide much of a protection.

>>Has any complaint been made to the product manufacturer and a reply received?

I discussed this several times with the distributor. The response was that so far there was no complain and that the product is advertised based on the manufacturer data. The distributor however agreed that the charging current is little bit high. Also the distributor removed references to the statement that the charger stops discharging when the battery reaches 1V (The charger does not have 4 independent discharge circuits.).

>>But then I guess many other chargers have the spring loaded sliding contacts as well.

Yes, but due to a different length AA versus AAA a good charge design should have independent bays for AA and AAA batteries. This design allows to reduce a charging current for AAA batteries.
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Old Apr 28, 2003, 6:36 PM   #13
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Regardless of what was said I have to mention that it is the best charger for AA batteries considering following:

- price
- performance with AA batteries
- it is compact
- can be used worldwide (96-240V, 50-60 Hz).

It only needs to mention that it is not recommended for a daily charging of AAAs.
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Old Apr 28, 2003, 6:45 PM   #14
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Forgot to mention that the charger has "guarantee of satisfaction for the lifetime of the product"!
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Old Apr 29, 2003, 2:39 AM   #15
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I won't be satisfied if my house burns down, whilst the charger is plugged in full of AAA's! Still I supposed they'd refund the price I paid.
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Old Apr 29, 2003, 8:03 AM   #16
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That is not my personal experience yet.

I do not have any way to accurately measure a temperature of batteries. Also I am not an expert in areas of fire and
safety so I can't address your concern.

The only thing I am concern about is the high current shortening lifespan of AAA batteries. That is the area I am familiar with.

I wouldn't charge any NiCd AAA. Also I would not charge any low capacity AAA batteries. These batteries are for slow charging only and get really hot. And never believe statements like "cool charging technology". There is no such a technology yet.

You should always look at the parameters of rechargeable batteries published by the manufacturer. Some batteries even specify the charging current on the battery itself.
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Old Apr 29, 2003, 8:45 AM   #17
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Perhaps we should just drop the whole charger and batts in a bucket of transformer oil for an hour or two on a timer! Since it's not the current that's the problem, it's getting rid of the excess heat. The problem is using temperature as an end of charge determining factor, on batteries with insufficient surface area to dissipate heat. Actually, if this was the case I'd expect AAA's to cut off sooner - so it must be ambient air temp sensing then? 'spect they're sold for use mainly in the cold North! If temp doesn't play much part, why not fit a 5 volt CPU fan?

I once used a 10 watt resistor dropped in a teapot full of distilled water, as a speaker load for a 100 watt Hi-Fi amp, and for power supply testing.
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Old Apr 29, 2003, 2:36 PM   #18
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Most fast micropressor driven charger detect completion of charge by a slight drop in voltage (-DeltaV). The more expensive ones have an independent circuit for each cell, and the thermal shut-down is only there as a last resource to prevent a customer from suing when their house go up in flame. :lol: :lol: :lol:

I don't think the problem is just restricted to AAAs, for example: the Rayovac charger is a super-fast under an hour charger, and it too can tear the decorative plastic covering from regular AA NiMh if theses cells are not designed to be fast charged (ie can not take the heat). I have a few Kodak cells that are now just bare metal, but still work, while other brands of AAs are doing just fine and toasty! :P

People realize this, I'm sure since there's so many other slower and cooler chargers on the market... and well recommended by other posts already.
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Old Apr 29, 2003, 5:01 PM   #19
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It's a fact of life that rechargeables do get hot when recharging (or discharging quickly). Although mine is an open air charger, even if it had a lid I wouldn't close it while charging (only when storing the charger).

Many chargers have two sets of contacts, one for AA and the other for AAA due to the different current requirements (even my cheap Panasonic 5hour charger has this). If your charger uses the same contacts for both, then it's not a good one.

I have no qualms about charging both AA and AAA in my charger (although not at the same time). I keep an eye on my charger when recharging (especially when I'm recharging my PDAs since the batteries they use are not removable).

It's also a fact that batteries wear out and can cause problems when recharging...the battery pack for my cordless drill went bad (I assume one of the batteries shorted out after many years of use) causing the fuse inside the charger to blow because the battery was drawing too much current from the charger.

Battery chargers are devices where you SHOULD READ ALL the safety instructions, and don't just pop the batteries in and plug it in without thinking. My cordless drill charger gets very hot because it is a one hour charger (9.6v at 1.5A, the fuse in it is 5A), and even states on it to let the charger rest 15 minutes between charging batteries.
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