15min / 1hour battery chargers - how??

[Marcos]

Are they safe? How can they do the same job as those overnight chargers in so little time? Any downsides? limited compatibility?

im tallking about AA/AAA battery chargers

[SiM]

apparently batteries charged with these 15 minute chargers have a lower expected life than if slow charged

[peterb]

AFIK they use a pulse width modulation type of charging which is controlled by the some measurement nf the battery - I think some have a temperature sensor to make sure the battery doesn't overheat. Basically short duration pulses of a relatively large current.

Do a google search using something like Rapid charging of NiMh batteries.

This is one link that search found

Frequently Asked Questions about NiMH Battery Chargers, AA and AAA

[stevie lee]

the batteries get VERY hot and if they are damaged in any way they will explode/leak badly due to the extra strain put on them... and only compatible batteries can be used safely, but these cost a lot more than normal rechargeables..

i have seen a few of those chargers with fans attached.. the shop i saw them at don't sell them anymore though.. so no link.

[Marcos]

are the 1 hour chargers also quite bad?

i assume its the 15min ones that are most dangerous/pushing the limits

[Bugbait]

and only compatible batteries can be used safely, but these cost a lot more than normal rechargeables..

Any decent rechargeable battery should be compatible with quick/fast chargers. Yes, you will wear them out faster but they're so cheap these days is it really a concern?

[kmac]

Its the heat that causes the issue (reduced life of battery). I have a 2hr and a 15 min charger, the latter with fan. With my 15min charger you can only use NiMH batteries not the NiCd types

[stevie lee]

it just depends on the batteries that you are charging mAh wise how much of a charging hit they can take, higher mAh's can take bigger hits. check the output of the charger before puttiung a battery in... the 1 hour chargers are safer though.

the condition of the batteries you are charging plays a large role in it aswell, the age of battery and how many times its been charged before.. the chemicals inside degrade over time, even when you are not using them..

normal AA and AAA bateries last up to 1000 charges before a full charge only lasts for around 5 minutes or so.. these fast charge ones i think only last around 200 times..

if you can get a 1 hour charger and batteries cheap they try them out and see..

only other thing is that some chargers charge the battery up to around 85%, then do a trickle charge to fill the rest up, this is because the last 15% is the hardest to charge and if it charges too fast then theres a high risk of damage.. so even if the green fully charged light comes on, it doesn't mean the batteries charged.

i think these fast charge chargers just do a continuous output untill the onboard sensors tell it that that batteries at the right voltage..
the energizers have a 'charge control' this either means it does a set output for a set time and you can only use a certain mAh battery, or there are sensors that check and adjust the charge time accordingly... can't find anything on web to check this, only way to find out is buying one and using amp meter..

1hour chargers (energizer ones) put out the following AA- 2.5 Amps AAA - 1.0 Amps,
normal chargers - AA - 0.36 Amps AAA - 0.15 Amps
15 minute chargers - AA - 7.5 Amps AAA - 2.8 Amps




this is at the limit of my battery knowledge now.. most of what i know is based on car/mobility scooter batteries and chargers, some is relevant and some isn't..

peterb's link explains it in more detail..

[Marcos]

hmmm, thats a lot of info, thanks

im gonna stick with my 12hr charger until it breaks, then will go for a good 1hr charger