Mailing List Archive

On Tuesday, 13 September 2022 06:47:21 BST Thomas Mueller wrote:
> from Laurence Perkins:
> > Some of the higher-end UPS models do have diagnostic modes for simulating
> > various events to make sure the connected systems behave as desired. A
> > very few of the consumer-grade ones do as well. But how to do it is
> > model specific, so you'll have to dig up the documentation.
> >
> > Commercial-grade units also often have a DC port on the back so you can
> > plug in larger battery banks and/or hotswap battery banks during extended
> > outages.
> >
> > If you want an arbitrarily large battery bank, just get a decent power
> > inverter heavy enough to run your load and a battery float charger that
> > can push enough amps to keep up, then put as big a stack of batteries as
> > you like between the two. The nicer inverters will even warn you when
> > the batteries get low.
> >
> > You can often get used batteries from the local automotive shop for just
> > the core charge. Just because it can't provide 600 amps to start a car
> > any more doesn't mean it can't provide 60 to run your computers.
> > Obviously they'll require more regular maintenance, but it's hard to beat
> > the price.
> >
> > LMP
>
> How would you physically connect the automotive battery to the computer, and
> would you need the shell of the old UPS?

Yes, you need the *contents* of the UPS shell. It contains the rectifier to be
able to recharge the battery/batteries and the inverter to be able to feed the
PC from the batteries.

I've also used a car battery out of an old Mini to keep equipment running
during prolonged power outages. I connected it in parallel to the UPS
battery. After the power returned, almost two days later, I disconnected it
and recharged it with a car battery charger, which could take the higher
amperage. Trickle-charging should be OK via the UPS.


> I have an old Tripp-Lite UPS, batteries are dead and no longer rechargeable.

Why don't you replace them? They are not particularly expensive, although I
have not looked at UPS battery prices lately.


> Would you connect only the computer, or would you connect the monitor as
> well? Would you connect networking equipment?
>
> Tom

I connect modem, router, PC and monitor, so that whatever operation is taking
place it can be completed, applications running ended and the PC shutdown
manually. If the PC is running unattended when the power interruption
happens, eventually the upssched will shutdown the PC.

>> If you want an arbitrarily large battery bank, just get a decent power
>> inverter heavy enough to run your load and a battery float charger that can push enough amps to keep up, then put as big a stack of batteries as you like between the two. The nicer inverters will even warn you when the batteries get low.
>
>> You can often get used batteries from the local automotive shop for
>> just the core charge. Just because it can't provide 600 amps to start a car any more doesn't mean it can't provide 60 to run your computers. Obviously they'll require more regular maintenance, but it's hard to beat the price.
>
>> LMP
>
>How would you physically connect the automotive battery to the computer, and would you need the shell of the old UPS?
>
>I have an old Tripp-Lite UPS, batteries are dead and no longer rechargeable.
>
>Would you connect only the computer, or would you connect the monitor as well? Would you connect networking equipment?
>
>Tom
>
>

If your old UPS had sufficient capacity, you can usually just open it up (make sure it's unplugged and turned off first, obviously) and replace the battery with one of the same size. Often there's an access panel for doing exactly that.

Otherwise, you'll need to extend the battery leads out through the side of the case to whatever battery bank you're using. Keeping the case would definitely be recommended since there will be high voltage in the system when it's in operation. Also the new battery bank will need to be the same chemistry and voltage as the original. Usually it's lead-acid and multiples of 12 volts, (hence why old automotive batteries can work, but will require test and service after every power outage because they're designed for high output, not deep discharge) but do double check.

What you connect to it depends on what you figure needs battery backup and how many amps the inverter in the UPS can supply without overheating.

Note that messing too much with the internals of a power inverter can cause fire or electrocution if done improperly, so make sure you research how it all works before modifying anything.

LMP