Valve-regulated Ni-Cad cells 1

[ScottyUK]

I'm familiar with the conventional vented Ni-Cad cell for stationary industrial applications and have been using them on and off for a long time. A couple of well-respected names - SAFT and Hoppecke - are offering a valve-regulated variant of established cell designs. I'm curious if anyone has any operational experience with this type of cell. Both manufacturers are claiming long intervals between electrolyte top-ups, 14 years and 20 years respectively, and that's attractive from a maintenance perspective. I wonder what are the problems with this type of cell?

I have an unhappy history with VRLA blocs and wouldn't install them given the choice but the Ni-Cad design seems significantly different: the construction appears similar to a conventional flooded cell, other than the venting arrangement. I'm trying not to let my prejudice against VRLA taint my opinion regarding valve-regulated Ni-Cads.

Data for the types I'm considering: SAFT Uptimax and Hoppecke FNC-VR.


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If we learn from our mistakes I'm getting a great education!

 

[stevenal]

Scotty,

Checking the electrolyte level is just one of the eight recommended quarterly checks recommended by IEEE 1106. Cutting that number to seven doesn't save a lot of maintenance.

 

[ScottyUK]

Hi Stevenal,

Agreed, but at least electrolyte checks are visual whereas topping up is intrusive. The fewer times the cell is opened up to the outside world the better. There is bound to be a downside to this design, and I'm just not quite sure where it is.


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If we learn from our mistakes I'm getting a great education!

 

[raithrovers1]

Scotty
I have expeience with UPS installations that use the Alcad Vantage cell which is also valve regulated Ni-Cad.
I work mainly in the offshore oil and gas sector where space is always a premium. Sealed lead acids are the most common battery out here because there is no need for a seperate battery room due to minimal gas release. As you have stated already, the reliabilty of VRLA is questionable.
Therefore this newer Ni-Cad design is becoming more popular as the manufacturer states that there is also minimal gas release from theses cells. Also they are charged at a single level float voltage and do require boost charging. This is accomplished by oversizing the battery to allow for the 80% capacity rule at a single rate charge.
Relating to one particular installation - I have not seen any cells needing topped up yet and the electrolyte level has not dropped much over 8 years. No cells have failed a discharge test yet either. The UPS has not suffered any failures during black outs.
On the flip side this battery had to be replaced after the first two years as there was a manufacturing defect that allowed dust to settle in the plastic seam welds during manufacturing. Over time the electrolyte seaped through the gaps caused by the dust and tracked to earth. Warranty covered it.
I am a fan of these cells as they are basically Ni-Cads without some of the hassles. Less sulphation - less cleaning, single level charge rate, less gassing and less failures than VRLA. All in all no negatives - yet!

UPS engineer

http://www.powerups.co.uk

 

[RRaghunath]

raithrovers1,
Glad to hear about your experience.
I too feel that VRNiCd is the way to go - to minimise maintenance and maximise the reliability of UPS. But, couldn't find much feedback till date.
Appreciate.