RE: Having 2 Batteries For A Battery Backups System Work Better Than One?

Hello. I have a question. Regarding Battery Backup UPS systems, having a dual or 2 batteries incorporated into the unit better than having just one battery? Yes, both batteries are functional and operational; the second battery is not passively resting in the battery compartment. They are usually 12 volts each.

Under typical conditions, regardless of the wattage needed; would the runtime (running due to loss of power) be increased or not? ...but how? Is this significant increased in runtime or not? It is truly worth having a second LEAD battery backup in your unit?

Please reply.

Thank you!

 

Off the top of my head . . . in a nut shell - yes. Having two 12 volt batteries connected in parallel (both negatives together/both positives together) will increase the reserve power, or "run-time", of a UPS. You have doubled the "capacity" of the system, but the voltage remains at 12 volts.

However, unless your UPS circuitry is designed for that configuration, there is a possiblilty the system won't recharge properly after being drained. May be other issues as well - but not being an expert on UPS systems, I can't say for sure.

Two 12 volt batteries connected in series (negative-positive/negative-positive) will of course double the voltage to 24 volts, and that would have a really nasty effect on a 12 volt circuit.

 

. . . Got to thinking about it, and felt I ought to provide a visual of what I mean by series and parallel connections (must be a bit of the training officer surviving in me, lol).

Here is a quick (albeit poor) drawing of both methods - sorry, pressed for time and not at my own PC - this is a paint construction.

 

Be advised: the sole purpose of a battery backup is to allow your system to perform an orderly shutdown upon power loss. We (U.S. Army) invented the first UPS Bypass switches to power teletype machines in case of nuclear attack, to allow them to send out one last message to the world.

The modern units have incorporated noise and spike filtering and conditioning, but the basics remain the same. UPS units are not designed to run for extended periods: they are for supplying enough short term power to save ongoing work and to properly close the operating system.

IMO, slaving battery units together is a bad idea.

@Spad: good drawing!

 

If you want longer battery time, get a laptop, notebook, or netbook computer. They're designed to run a long time on battery.

 

Agreed with Caliban. I had bought a 1000VA UPS which was good for a half hour as my power ATT only went out for 5 or 10 min' at a time. Now the power only sometimes switches lines which is just long enough to shut a 'puter down. Hey, I live in the sticks.

 

@montecarlo1987: apologize for hijacking your thread - Spad pretty much answered your questions. If your unit is designed for two batteries, then by all means, it would seem logical to use two batteries.

Sorry about the soapbox - UPS units are a peeve of mine, mainly because they're so often misunderstood, and because retailers hype them to unsuspecting users for the wrong reasons.

 

Exactly right - people expect too much out of a UPS. I have my PC's on a UPS to allow them to shut down during a power outage, and to protect them from voltage spikes (and dips) . . . not to outlast a power failure. Unless you are running a heart/lung machine or some other vital device, that is all they should be used for.

Is that the one about putting your head between your knees and kissing your A** goodbye? :-D

 

Thank you for your replies.

 

You got it.