batteries 1

[powercam]

hi need to know if any utilities out there are using ni-cad batteries for substations that are 110kv and above. just to get a number ...i need to order batteries for all our subs but i am worried as to wheter this is tried and tested before, as i dont want to get caught out with problems later. thanks people.

 

[busbar]

Might review IEEE Standard 1115-2000 … Sizing Nickel-Cadmium Batteries for Stationary Applications Decription

 

[mc5w]

You also need to watch what kind of chargers that you have. Lead acid batteries of the the industrial type need 14 to 15 volts to reach full charge. Automotive batteries need about 1/2 volt more because they have more sulfuric acid for cold weather and about 16 volts at the 60 hour charge rate.

Nickel cadmium batteries need more like 16.5 volts at the 100 hour rate to reach full charge and nickel iron batteries need more like 17.5 volts at the 50 hour rate. Nickel iron has more self discharge which requires a constant trickle charge but they can take a LOT of abuse. If you have a rural substation that has frequent blackouts nickel iron might be your best choice. Nickel iron batteries were at one time an export restricted product because of how well they work in diesel electric submarines.

Batteries is general and sealed lead acid, any nickel cadmium, and any nickel iron battery in particular can take a week at the trickle charge rate to reach full charge. This is because the maximum rate without generating hydrogen and oxygen gas is proportional to the amount of UNCHARGED capacity left. In the case of a forklift truck battery you can get it all the way up to full charge in 8 hours because you can tolerate gassing during the last 2 hours. In the case of diesel electric submarines the nickel iron batteries could only be charged to 50% maybe 66% of ultimate capacity in 8 hours because gassing could not be tolerated. If the captain was willing to trickle charge the batteries for 3 days then he could get a 99% or 100% charge.

Your substation may have a similar gassing issue that dictates that you will only be able to charge up the battery to 66% in 8 hours and then trickle charge for a week to get full capacity.

The reason why nickel cadmium batteries have a poor reputation is that a lot of chargers do not charge them up enough. Same can be said about nickel iron batteries. Nickel cadmium and nickel iron batteries can occasionally grow metal dendrites that will short out a cell. To fix this you need to blast charge the cell using a BFC (Big expletive Capacitor) in the amount of several tens of thousands of microfarads and charged up to say 36 volts before blasting a 6 volt or 12 volt battery.

Mike Cole, mc5w@earthlink.net