3 UPSes from a Single Battery

[KeepItSimpleStupid]

I was trying to find something and I came up with this: Catalogue - Battery Isolation Diode - Jindra Energy Conversions - (Version JPG) - 1 3 total.

That's for 240 Amps which would be good for 12 * 240 Watts (12 Amps * 240 volts). It's the right kind of device. Might be a overkill.

 

[FPLenin]

I live in Venezuela, It might be hard to find such an specific part - brand...any general part name - capacity?

 

[KeepItSimpleStupid]

Basically P = V * I. Your inverter VA goes in for P. 12 is V and you get the value of I when sized for the inverter.

Schotkey (however it's spelled) has the lowest forward voltage drop. Reverse voltage should be greater than 18 V. Amperage has to gigger than your inverter VA divided by 12.

Battery isolator diodes would be a common term.

You can also size the diodes to the load on the inverter. Alternator diodes come to mind. They should be available in 30, 60, 90 amp or higher. They can be hard to mount. Some pressed and they would need a heatsink. Even the 3 phase bridge might work depending on how the anode (+) faces. The anodes would go to the UPS's and the cathodes to the big battery.
You can use an ohmmeter or diode checker to figure out the polarity. They would be less than ideal because of the voltage drop and mounting difficulty, but will illustrate proof of concept.

Basically, with the diodes, none of the UPS can charge the battery.

Audio instal places, recreational vehicle places and junk yards are possibilities.

 

[tcmtech]

I think this is being over analyzed. Given that all three UPS units are being powered off of a battery that has a combined capacity of equal to to greater amp hour capacity than their original battery's combined amp hour rates would dictate that the three combined charging systems should still work together to handle the larger battery.

Also being that UPS units have some level of automatic battery monitoring and charge control they should still regulate themselves properly regarding the charging just the same.

If it was me I would just try running them together to see if they behave properly before I ever spent any time or money concerning myself with what if scenarios until they actually prove that they are an actual issue that needs dealing with.

I have several old UPS units that I have converted to use external deep cycle battery's that are using battery's much larger than their original internal ones where and they all seem to have no issues with charging other than they just take proportionally longer to do it.

 

[Sceadwian]

Your assumption that the three charging systems will work together is the problem TCM, many modern charging systems rely on the battery itself as a feedback element, it's no longer just the battery and the charger, it's three chargers and the battery and how one charger is going to effect the other is unpredictable until tried, if all three of these UPS's simply provide a stupid basic float charge to the lead acid pack then everything will be okay. If any one of those chargers uses an intelligent charging system of any kind something is going to go wrong, and one or all three of the UPS charging circuits (and possibly inverter circuits along with it) will fry.

 

[KeepItSimpleStupid]

Bigger battery, 1 UPS isn't a problem just decreased charging time. 1 Battery and 3 UPS's could be.

That's why I'm recommending 3 isolating diodes. One diode can be used just to see if the UPS's hiccup and complain if they can't charge.

So, you place a diode in series with the standard battery for testing and run the UPS in the various modes including on battery for a while. Do it for all 3.

 

[Sceadwian]

The diode method is probably safest. Leave the largest VA rated UPS as the non diode isolated UPS it logically should have a better charger, but make sure you disconnect the speakers from the other two, they'll probably beep every few minutes for the rest of their lives with a battery fault indication.

 

[KeepItSimpleStupid]

Didn't think out letting one charger charge the battery. Good one.

 

[Sceadwian]

I'm responding fast and not thinking things all the way through, much like all of our posts KISS =) As an amalgam, I think we might get it. This is what we're all here for in one place =)