UPS Battery Type for Elevated Room Temperatures

[haze10]

Need to specify batteries for a warehouse location, winter temp of 55F and summer temp of 95F, for a UPS application. Reluctant to use convential lead calcium because prior experience in this environment resulted in short service life.

Any recommendations for chemistry, construction, or manufacturer.

thanks

 

[MiketheEngineer]

I would call the battery mfgs - they should know best..

 

[haze10]

Have you tried that yourself. First they tell you to call your local salesman, who knows nothing. Then they find some number for a person who only has voice mail and never returns calls. I gave up on them, and came here. Now you're telling me to go back to them?

 

[rbulsara]

haze10,
This attitude will not get you much mileage here. Like it or not, Mike's advice is sound. There are more than one mfrs.

Although you may get lucky and some will answer to your liking. Stay tuned.

Rafiq Bulsara

http://www.srengineersct.com

 

[Warpspeed]

The important thing with this is the charging voltage needs to be temperature compensated. At elevated temperatures the charging voltage must be reduced to reduce gassing during charging, otherwise the electrolyte will require constant topping up.

I might suggest that a reduced service life is probably due to lack of maintenance by the user, especially checking and topping up the electrolyte. If these are sealed gell cells, you are doomed.

I would still prefer flooded lead acid cells, the Ah capacity increases with temperature, but the charging voltage absolutely must be reduced.
Something like fork lift batteries would be my choice.

Try to find a properly temperature compensated battery charger with a temperature sensor that can be attached direct to the battery case, it is the electrolyte temperature that is important, not ambient.
I believe this may be the solution to your problem.

From memory, the required compensation is -3mV per cell per degree Celsius.
As your UPS probably has a fairly high voltage battery, the change in charging voltage with temperature can be significant.

If charging rate is quite high, electrolyte temperature is even more important than ambient.

One last thought.
Automotive batteries work in ambient under hood temperatures of around 85C, and at very high charging currents, and they work just fine. So it is possible.

 

[sibeen]

Put the batteries in a separate IP enclosure and attach a heat exchanger or small aircon to the enclosure.

It something I've done on numerous occasions where the ambient temperatures were going to kill off the batteries in quick time.

 

[ScottyUK]

Flooded NiCad is the most tolerant (among the common battery types) of high (or low) temperatures. It is also the most expensive. You will likely have to implement a more frequent maintenance programme to keep electrolyte levels up because the higher temperature will result in higher losses. Warpspeed's comment on a temperature-compensated charger is right on the money.


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

 

[sibeen]

Whilst flooded NiCad are a great battery in terms of longevity the costs involved can be rather exorbitant, at least in Australia.

Australia no longer has any facilities for disposal of these batteries and the last lot I had to get rid of, quite a few years ago, had to be shipped to New Zealand. The client wasn't exactly a happy camper when told the cost of disposal was nearly as much as he was paying for the new set of sealed lead acid.

 

[Warpspeed]

Flooded nicads are premium batteries at a premium price, usually only affordable by "government funded" projects.

In a previous incarnation (a long long time ago) I was battery applications engineer at Saft Nife in Australia.

Despite the enthusiasm of our battery sales staff, many customers had to be revived and treated for nervous shock, after receiving an initial quotation for a large bank of flooded nicads.

 

[haze10]

In this case I don't think the total cost would be too high as the bank won't be that big. I only need about 10 minutes of UPS runtime, 25KW UPS.

What about NMH, nickel metal hydride, batteries. I've read that they are being built in stationary class, look like regular lead acid. NiHM is supposed to be heat tolerant.

The other thing is lead acid but with different chemistry or design. I thought I read that lead calcium batteries could be had with different plate thicknesses, and the thicker plates were more forgiving in terms of longevity.

The other thing is lead selenium instead of lead calcium. They are supposed to be more heat tolerant.

Its hard to tell from the manufacturer's literature. They will claim something like "operating range 45-115F..." but any battery will 'operate' at those temperature, I need to know if the life expectancy is going to be reduced.

I appreciate all the input so far.

 

[Warpspeed]

Thirty dc Kw for ten minutes is still quite a lot of power.

Battery Ah capacity is always rated at the standard ten hour discharge rate, as the discharge rate increases, the achievable Ah capacity falls off quite dramatically.

The problem being, that not all batteries are suitable for such a very high discharge rate. One of the reasons I suggested fork lift batteries is that they are internally very rugged and capable of this type of short term discharge, and you buy them as individual cells.

I would not worry so much about battery chemistry, as the extreme discharge characteristics you will be demanding.
As stated earlier, I believe money spent on a good quality temperature compensated battery charger will go a very long way to prolonging battery life.

When you initially size your batteries, allow plenty of excess capacity, because achievable capacity to the end point voltage will gradually fall off with time.
If you design it only for ten minutes holdup time, it won't take long to drop to nine minutes, then eight minutes....

 

[ScottyUK]

We've just bought about 40 tonnes of flooded NiCads and they certainly weren't cheap. We're a plant where ultra-high availability and longevity is worth the premium, but I acknowledge that many places have different cost/benefit criteria.

Disposal of NiCads is more costly than lead-acid: one of our contractors will remove lead-acid types at no cost to us, while NiCads attract a premium.


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

 

[itsmoked]

haze; Your "high temp" is pretty feeble. Going with some alternative to the 'tried and true', can extract a lot of money and time from you and your company.

95 is nothing to LA batteries - if - you do as suggested and control the charging to the actual battery temperature.

You'd probably be better off using LA with a compensated charger and Hydro caps than breaking new ground in battery applications. That is unless your business is in UPSs, or your application actually sees 130~140F.

Keith Cress
kcress -

http://www.flaminsystems.com