Advice wanted on new Ni-Cads

[ike]

My cordless drill died yesterday. The batteries were 6 years old and I think the charger cooked itself trying to charge a completely dead battery - so I can't complain. Anyway, I bought a new drill Hitachi DS14DVF3 (inc. 3 Ni-Cads). The dealer advised me to run a new NiCad completely flat ("tape the trigger down if you have to") for the first 3 or 4 charges. This he said will properly condition the battery for a long and useful life. Only when I read the destructions, they advise NOT to fully exhaust a battery before recharging, as well as not to recharge a just-depleted battery until it has cooled off, as this affects the 'battery chemistry'.

The bloke at PHM Plant Services should know his stuff - PHM are specialists selling and repairing Hitachi and other industrial quality power tools for many years. So how come Hitachi say different - who is right?

PS. I was given a tip to use the second battery only if really necessary for continuous working, but more importantly to keep the 3rd battery virgin until the first one dies. Then your cordless drill can keeping working for a lot longer - 10 years maybe on all 3 batteries. That sounded like a great idea to me so I thought I'd share that with you.

cheers,

Ike

 

[mailee]

I have a Makita driver of 9.6 volt and it came with two batteries around ten to fifteen years ago.....I am still using the same batteries! All I have ever done is run them down until they won't turn the spindle any more and then charged them each in turn. Now watch my luck having said that they will fail tomorrow. :lol: Oh and by the way, they are the old Ni Cad type cells. :wink:

 

[Woody Alan]

Ike

You were misinformed and yet advised partially correctly. Do the first charge as advised by Hitachi, when using for the first few times you probably won't get full capacity (although it's recognised makita use high quality cells) . When discharging you will soon know when the power has tailed off and you can then hold the trigger until the motor virtually stops running. DO NOT tape it up this is foolhardy because if you then leave it accidentally you will depress the cell voltages to zero, this is not ideal for a couple of reasons one being that all cells are not equal and if one is zero when adjacent ones have voltage it's "possible" for the cell to be reversed in polarity. When you have discharged the drill ideally let the pack "rest for 3-4 mins to let the voltage rise naturally within the cells they can be recognised by the charger more readily then. The voltage rise can be noticed by pullin gthe trigger again after a while and it will appear as if the batteries are slighly rejuvinated. Charge fully and repeat.
In all cases follow Hitachi's instructions over anything I have said. As to the third battery sometimes cells can deteriorate when stored but usually NimH cells are worse for this. I think the answer to that is it's your call, after all if you only have one tool you'll always have one pack ready charged why have two? perhaps store in a dry cupboard indoors. If you charge before it is neccessary the cells are possibly not formed correctly this is again how the crystals are built during the charge process. When slow charging small crystals are built this gives more capcity because it's more efficient but sometimes when high current is required back the cell can't deliver" The pack when new has small crystal structure when you fast charge it you are creating large crystals if you keep interupting this cycle it's possible to get the crystals "muddled" for the want of a description. This can be recovered from by repeated slow discharge/cycles to reform back to a "new" like state before going back to a fast charge cycle. If packs were cycled on a slow charger discharger from time to time they would last longer but this is a consumer market.

Cheers Alan

 

[ike]

Thanks Alan,

That's very helpful.

cheers,

Ike