Caring, Feeding and Enhancing UPS Battery Systems?

cdn-programmer asks: "I've got a couple UPS's that are now about 5 years old. They are MGE EL4 units - rated at about 450VA /280W. These originally came with a battery rated for 2x6V - 7.2Ah I've found an inexpensive replacement battery: SBS60 rated at over 50Ah and I've done a little mod so the unit 'fit' together. I've also done as much reading as I can on float currents and ripple currents and so forth basically covering the care and feeding of your UPS battery system. People can find some good information in the SBS web site and the specific data sheets are here. Look under the SBS section for the manuals. If people find alternative batteries there seems to be some excellent tech specs here. Having read these it seems to me that there should be no reason that I cannot 'redesign' the UPS to give it a significantly increased power reserve. The load is the same... the only difference is that a larger battery is used so this means that the recharge times will potentially be much much longer. So what? We are not interested in cycling the battery. Indeed the power here is quite stable and we get very few outages per year."

"Now - the SBS people have been very professional and have provided good technical engineering data. I haven't been able to find much data on the MGE EL4 and I wonder if this cheap little UPS has the proper smarts to take good care of my new battery? If it does not - then why not and what models/manufacturers should we be considering?

For instance, what is the ripple characteristics of the EL4 and how can I measure it? Since the SBS60 is HUGE in comparison to the original batteries (Panasonics - 7.2Ah - 2x6V) is ripple even something to worry about?

Does the EL4 charging system 'cycle' in a harmful way? I tested the float voltage levels and found that they varied from 13.89 to 13.42 over the course of a day. But this battery has only been hooked up for a day so maybe its stabilizing. The nominal float should be 2.27 per cell according to SBS so that works out to 13.62 for the battery.

Does the EL4 have a temperature sensor? This is something else that the charging system should do according to the SBS people because optimal float voltage varies with temperature.

Finally, I'm interested in doing a load test to determine how healthy by batteries are. I'm thinking that a very simple test can be a couple lamps - say 100 watt - that can be plugged into the UPS. Since I've never done anything like this before the thoughts in my mind are that all I would need to do is take a voltage reading say every 5 minutes over the next few hours and if I can find the proper curves this should yield enough data to determine the life expectancy of my battery.

If anyone has actually done tests like this it would be wonderful if they could tell us how to do this."

Comments

Re:Larger batteries = more charging current/voltag

[RobKow]

A clarification:

A proper "universal" charger design (which I wouldn't expect to see in a UPS that doesn't accept add-on batteries) would charge properly, but more slowly.

Re:A couple of problems...

[amorsen]

Do not believe the +/- 5% they talk about. Once you put a switching powersupply into the equation, you can easily measure double or half the real number.

oh yeah

[pair-a-noyd]

one other thing.

Take an OLD PC case and fill it with whatever size batteries you want, wire them in parallel and run the cables into your UPS. Wire the external battery pack into the UPS in parallel.
The voltage must remain the same but you get more amp hours this way. You can also use batteries that are physically larger that normally won't fit inside the UPS.
You can get LOTS of run time this way, hours and hours of run time..

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