Can I parallel connect batteries to a UPS not designed for extra batteries

I am not an expert, but you might get a race condition between them. Meaning one lower battery will take from the other. But it should work.

Paralleling the batteries should *RUN* the critter fine, and extend your runnable time, but don't bet on the beast being able to keep all the batteries (however many that might end up being) properly topped off. I highly doubt that the charge circuitry is set up to handle keeping a proper charge on batteries instead the single that it was most likely designed around.

Some UPS devices are in fact intended to charge multiple batteries, but this is mostly a function of the higher end or professional types. Check the back of your particular model and see if there is a large amperage DC plug there. If so, use the limits that the manufacturer recommends. If not, then what you have been told is true- they will certainly RUN from multiple parallel batteries and greatly extend your running time, but they will in all likelihood be unable to keep extra batteries charged.

Cheers!

Chip Shults My robotics, space and CGI web page -

Unless it melts due to lack of cooling.

If it's just a relatively simple constant current- constant voltage supply, then it will, without any problem, it'll just take a lot longer to come up to charged. As batteries are charged over several hours, there probably won't be any thermal issues on adding more.

If it's 'smart', then it may have a timer which cuts off charge, or the software may be unhappy with the change.

In article , snipped-for-privacy@doglover.com mentioned...

You can parallel batteries if you use a rectifier diode between the battery and the load. These very high current diodes are available at RV stores, where they are used to parallel the battery to get more 'juice' in RVs and trailers. I believe they are Schottky diodes for low voltage drop.

Hmmm. The answers to my question are surprising in that I hadn't thought about the charge cycle, just the discharge cycle. My concern would be that one of the batteries with a higher terminal voltage would discharge into another battery with lower terminal voltage. This would probably mean that I'd have to have some sort of equalizing circuit that prevented this. A diode as one poster pointed out would suffice however I think it would also block the charging circuit.

supply,

That's what I think also. I may end up getting a longer running time while on batteries but the recovery time of the UPS would be correspondingly extended. However, at some point in time, all cells would be charged to their capacity.

The UPS is smart in that I can monitor the various aspects of its operation from a controlling computer -- its terminal voltage, boost, buck, temperature, frequency and so on. There must be enough intellegence in the control circuitry to handle charging as well.