Use of deep cycle lead acid battery for standby application 1

[BK32]

I have a question regarding the suitability of deep cycle lead acid batteries for use in a standby power application.

Recently, a contractor has replaced a NiCad (vented sintered plate construction) 80Ah, 24Vdc battery bank (made up of 20 cells) , with 2 off Supercharge 12V, 80Ah (Model No: D50Z) deep cycle batteries connected in series.

The application is to provide a transitional source of power to a public address system on a ship in the event the main source of power is lost. The battery supply is required to maintain the 24VDC supply to the system for 30 minutes. This system is pretty critical for damage control operations on the ship and therefore needs a highly reliable battery supply.

As per normal standby applications, the batteries are normally in a float charge state until such time as the mains power is lost (which is not often).

I know that SLI type batteries would be completely incorrect for this type of application, but I am not sure about whether the deep cycle batteries are suitable for this application either. From initial investigations, I cannot find anything that explicitly rules this out. However, I do notice in a number of reference texts that they continue to distinguish between stationary lead acid batteries (used for stanby applications) and deep cycle lead acid batteries (nominally designed for traction, vehicle power applications).

Can anyone provide some advice on the suitability of these deep cycle batteries for this application? Are there any obvious drawbacks? Any special considerations that should be addressed that would enable deep cycle batteries to be used?

Thanks in advance for any assistance that you can provide.

 

[ScottyUK]

The vented NiCad was a far better technical solution in terms of longevity, reliability, temperature tolerance, and so on. The lead-acid type has the advantage of being cheap and requiring less maintenance. In fact the latter point is debatable, but since the thing is unmaintainable you might consider it to be 'maintenance-proof' rather than 'maintenance-free'.

 

[MikeHalloran]

Don't you have to change (or adjust) the float charger when changing battery chemistry?


Mike Halloran
Pembroke Pines, FL, USA

 

[racookpe1978]

That depends on how your charger is (1) designed and how that battery charger works

Does it have a charge regulator, voltage monitor, battery condition monitor, temperature and density and acid level monitor (of the battery fluid), non-spill/non-leak/non-evaporative caps on the battery, etc.)

Does it regulate the charge current, the charge voltage only, neither (just runs), and the needed periodic lead-acid battery maintenance charges (equalizer, trickle charge, etc.)

Lead-acid batteries are tricky to maintain. Acids are dangerous, the hydrogen explosive, the fluid control messy, etc. And, physically, they can tip and spill - particularly if in an earthquake or seismic zone that exaggerates the need for power outage protection.

The extra expense of a simpler, easier-to-care battery can be well worth it.

 

[ScottyUK]

"Lead-acid batteries are tricky to maintain."

Sealed lead acid batteries are impossible to maintain.

 

[stevenal]

Chemistry aside, it seems to me the intended use, aboard ship, precludes the use of a "stationary" battery. I think you will find mobile or marine batteries will better survive the motion of a rolling ship.

 

[itsmoked]

Any deep cycle battery with do the job for you. The job is very tame as they go. Of course as mentioned your charger should be the correct one for the task. It should also be a quality multi-stage charger.

As for stationary verses deep cycle, I don't believe there is a valid difference, it's just semantics. Both are "deep cycle". I'm amazed that you only need 30 minutes of backup time for a ship's PA. Wow. I'd expect a couple of hours at the least.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[stevenal]

stationary battery: A storage battery designed for service in a
permanent location. See also: battery.

marine electric apparatus Electric: apparatus designed especially
for use on shipboard to withstand the conditions peculiar
to such application.

 

[mikekilroy]

well put itsmoked; I agree: Any deep cycle battery WILL do the job for you

Obviously BK32 you need to verify the contractor replaced the nicad charger with multistage lead acid charger, since nicads require constant current charging and lead acid require constant voltage charging, and for good life also require multistage to keep sulphur build up on plates down.

Mighty big PA system! 80ah*24v= 1920watt-hours. With Peukart effect, 0.5 hour life would likely be around 2500 watt PA system! If it IS this big, then you may have a problem getting 30 minutes life with this chemistry! The nicads could do it, but lead acid may not. Nice design would be to design it for about 1/10c rate so my guess is it is a 200 watt PA for a good 5+ hours life? I would be interested to know if it has ever been tested to see how long it WOULD work and what size amplifier it really is....

http://www.KilroyWasHere<dot>com