First time charging

[Electronman]

Hello,

Why several kinds of batteries do need to be hold on the charger for hours (more than 8 hours) for the first time of use??
Is that due to memory effect which exists just for NiCd cells?

 

[jimlovell777]

Is that due to memory effect which exists just for NiCd cells?

I've purchased products that have other battery chemistries and they still said to charge for more than eight hours. I don't know the real answer but I kind of always assumed it was just to ensure that some anxious consumer didn't jump the gun and ruin the batteries immediately. Tell people to charge something for 15 hours and even if they get impatient at 10 hours the device got it's first full charge. Tall someone to charge something for 8 hours and let them pull it at 4 then you have a battery that never reaches full potential. I'd like to know the real answer so if anyone knows it kindly step forward.

 

[Electronman]

No idea?

Is this true that just Nicd batteries suffer this problem?

 

[kchriste]

It is probably more relevant for battery packs than single cells. NIMH batteries will self discharge over time. Some cells in a pack will self discharge faster than others meaning that some cells will be completely dead and some at say 50% capacity. That means, that if you first charge them using a fast charger, some cells could be over charged before the charger shuts off due to peak detection of the deadest cells. Or the opposite could occur with some cells only being partially charged due to peak detection of the 50% charged cells.. A slow 16hr (0.1C) equalization charge allows safe over charge of the partially dead cells while allowing the other fully dead ones to charge 100%.

 

[birdman0_o]

Why is it that we are told to empty completely then charge Li+ batteries to full during the first use. I see now why with NIMH, but what about single cell Li+ ?

 

[audioguru]

A lithium cell should never be discharged below 3V. A circuit that uses a lithium battery has parts to disconnect the load when the voltage drops to 3V.

 

[Boncuk]

When batteries are manufactured they will not be fully charged to guarantee a certain time on stock.

Lead-acid batteries are manufactured dry for (almost) unlimited stock life. When taking them into service sulfuric acid is added. The battery won't be charged at all that moment.

It has to be "formed" and charged initially for several hours (manufacturers normally recommend 12 to 14 hours) not to exceed a moderate charging current of 1/10th of the capacity.

Since nobody knows for how long the battery was on stock before purchase manufacturers recommend an initial charge cycle before first use.

An NiMh battery is charged to 3.2V initially (at the manufacturer's) and the final charge voltage is 3.6V. Adding the missing voltage the battery has gained full capacity.

Charging a few cycles real slowly (at reduced charging current) the battery lives longer.

I usually achieved 1,000 charge cycles using NiCad batteries. Having enough battery packs at hand you can give the battery the necessary time to charge slowly and use a spare pack during that time.

Electricity is fast - Chemistry is not (usually).

Boncuk