DC Charger for Generator black start

[HamidEle]

I am purchasing a 2.5MW generator recently. Vendor indicates that they the Lead acid battery charger will come with their package. But the client insists on using Ni-Cad Battery since it is their standard. I wonder if there would be any issue if we use NiCad Battery in place of lead acid type. Any inputs would be highly appreciated.

 

[MikeHalloran]

NiCds are ideally suited to stuff like starting helicopters, where they are required to spin up the engine and the rotors to starting speed before the ignition is actually switched on. They are usually sized so they can do it exactly twice, and then you are stuck looking for another power source.

I.e., they thrive on use and abuse, so be sure to be very rigorous about scheduling and conducting generator startups.

NiCd battery assemblies are usually sized so that a decent lead-acid charger of the same nominal voltage won't kill them. Some of the fancier industrial chargers will have a switch or other adjustment for battery chemistry. Check that the charger you are being offered is documented to work ok with NiCds.




Mike Halloran
Pembroke Pines, FL, USA

 

[ScottyUK]

NiCad is a good choice if you can afford it. Make sure it is a type designed for short duration heavy discharge - most manufacturers offer two or three variants optimised for different discharge profiles.

 

[HamidEle]

Thank you guys for the responses. The client doesn't seem to care about money. If Nicad can do a better job, definitely we can go with that.

 

[ScottyUK]

Look for brands such as Alcad, SAFT, Hoppecke to name a few of the better ones.

Flooded cells will have a long life, and some of the newer designs use recombination to minimise gassing and electrolyte loss. Get a purpose-designed charger, a lead-acid charger will shorten the life of expensive cells.

 

[wayne440]

...Vendor indicates that they the Lead acid battery charger will come with their package...

Buying a 2.5MW set is not like buying a 2.5KW set, the buyer should be able to specify a ni-cad battery and charger if desired with no issue. I would be sorely tempted to explain to the (prospective) vendor that a suitable ni-cad charger will come with the set if they want the sale. Of course, I am not used to having all kinds of money to throw around.

 

[raithrovers1]

Just be aware that the VRLA charger will be designed to charge 12 cells (nominal 24V with a float charge voltage of approximately 27.2VDC). A Ni-cad battery will more than likely have 20 cells which will need to be float charged at 28.4 - 29VDC. It may also need to be able to boost charge the battery at 33VDC depending on the make of Ni-Cad battery you buy. Most of the new Ni-cad cells can be used in float operation without ever having to boost charge. They are usually overrated to accomplish this. This must be checked before you buy a VRLA charger for use with Ni-Cads.

UPS Service Manager

http://www.nolanpower.com

 

[powerjunx]

go for Ni-Cad..


"..the more, the merrier" Genghis Khan