Best practice for maintaining my NiCd Recharable Battery (18V 1.7Ah)?

[bs9999]

I have 4 related questions but before i get to them please read the details first:

I recently purchased the Worx 18V WG150 Grass Trimmer. This trimmer came with 2 recharable batteries (each battery is: 18v 1.7Ah NiCd). The trimmer included a battery charger with a feature to automatically prevent these batteries from overcharging (it monitors heat). The trimmer only uses 1 battery to operate.

My 4 questions:

1. Both batteries have not been charged yet (they are fresh out of the box). Because i want to only use 1 battery can i just pack the 2nd battery away in storage (completely discharged) for maybe a year (or more) and when i need it i can just dust it off, fully charge it, and get going?
Additional Details

2. To best maintain my battery, i was thinking i should FULLY charge it (from a completely discharged state) on the day i need it (charging takes 1 hour when battery is completely discharged), and then use the trimmer until the battery has been completely depleted (a complete cycle). And then store the battery, now entirely discharged, until i need it again maybe a month or more from that point. Is that an acceptable plan, realizing that the battery will be stored totally discharged for long periods?

3. If i fully charge it then how long can i keep the battery in this charged state before i must discharge it? Are there any consequences to keeping it fully charged for long periods besides a potential 10-20% self-discharge occurring? (i.e., will the battery become damaged?)

4. Is it best to keep the battery entirely discharged when storing it for long periods? How long can i keep it stored in a discharged state before i must fully charge it again, if necessary? Does the battery become damaged by being entirely discharged for long periods?

Thank you.

 

[MikeHalloran]

1. NiCds typically arrive dead because they self- discharge, not because it's a desirable storage condition for them.

2. I suggest you charge both batteries before storing the unit. On the day you need it, plug one into the charger and one into the trimmer, and start trimming. If the trimming battery hasn't discharged too badly, the other one should come up to charge while you are working.

3. I wouldn't deep cycle a NiCd until it told me to do so, e.g. by losing capacity.

4. Charged is better than discharged for storage.

Ideal service for a NiCd is heavy use to deep discharge followed immediately by charging. Example: Starting a helicopter. The batteries they can carry generally have enough energy stored to bring the rotor and engine up to lightoff speed, once, maybe twice.

Worst possible service for a NiCd is floating forever, e.g. in a burglar alarm that's hardly ever triggered, but which charges the batteries continuously.

The NiCds in my PDA are doing nicely, after >5 years, because I only plug it into the charger when it clearly needs a charge.




Mike Halloran
Pembroke Pines, FL, USA

 

[sreid]

I agree with all that Mike H says. NiCads have two nasty features.

1) Fully discharged cells can "Reverse Polarity." Special charging is required to get them out of this condition otherwise they will be distroyed.

2) NiCads have a "Charge Memory." If recharged from a partial discharge, they will not accept as many amp hours as a heavily discharged cell will.