You can keep batteries at their float potential with a regulated power
supply, but it won't really "charge" them. The point is that to keep
batteries in their best condition, you really should do a bulk charge
after a discharge event. The power supply solution won't do that.
A UPS has a separate connection for the load and the batteries so that
it can discriminate between current going to the batteries versus
current going to the load. A power supply can not do that.
Also, many UPSes will have a low voltage disconnect (LVD). This is a bit
of a philosophical issue, as some people will rather run the batteries
down to avoid any downtime. My opinion is that if your battery array is
large enough, you should never hit LVD. Stuff happens though, and
batteries are usually the most expensive component of a backup system.
bp
<part15sbs{at}gmail{dot}com>
On 3/9/2016 11:38 AM, Mathew Howard wrote:
Is there really any advantage to using something like an AD-155B with
a UPS function over just connecting the batteries in parallel with the
load to a normal DC power supply and setting the voltage properly? It
seems like there would be less parts to fail and it'd be easier to add
redundancy if the batteries were just connected in parallel.
On Wed, Mar 9, 2016 at 12:52 PM, Chuck McCown <[email protected]
<mailto:[email protected]>> wrote:
A pair of power supplies that are capable of pulling the load and
charging the battery.
For example, if you needed 200 watts for your 24 volt loads, you
need 8.3 amps. Round that up to 10 amps.
Then you have to decide how long you want this thing to last
without commercial power. I would think 24 hours is a minimum.
So 10 amps x 24 hours is 240 amp hours of battery.
It is always a safe figure to charge a battery at .1C or 10% of
its capacity or less. That would be 24 amps to charge the batts
after a power outage, plus 10 for load = 34 amps of power supply.
You could get by with 20 amps, just will take a bit longer to charge.
Lots of 20 amp 28VDC power supplies out there.
Rule of thumb double your load power or more to size the charger.
*From:* SmarterBroadband <mailto:[email protected]>
*Sent:* Wednesday, March 09, 2016 11:45 AM
*To:* [email protected] <mailto:[email protected]>
*Subject:* [AFMUG] Small DC Site
What are people using to power small DC sites. Option 1 up to 150
- 200 Watts, option 2 up to 300 – 400 Watts. I’m looking for a DC
UPS that can charge attached batteries. Need to have 24 and 48 volt.
