A charge controller will do float 99% (and more) of the time if there
are no (or few) discharge cycles. The AC charge controllers we've been
using do a pretty short duration bulk charge, and for most (nearly 100%)
of the time, they are in float mode. We also don't oversize the
controller. It might take a day or two to recharge the batteries after
an AC outage, but they don't have the capacity to overdo it.
bp
<part15sbs{at}gmail{dot}com>
On 3/9/2016 3:11 PM, Forrest Christian (List Account) wrote:
That's not 100% correct...
What isn't known very well is that there are lead acid batteries which
are designed for 'standby' or 'flat' use, and lead acid batteries
which are designed for 'cyclic' use. (And of course some hybrids out
there which can do both at least somewhat).
'Standby' would be the method you'd use at most AC power sites. The
battery rarely gets cycled, and you're mainly concerned with service
life in years. In this application the best (and manufacturer
recommended) method of charging the batteries is to apply a constant
voltage across the battery with a current limited to about 0.1C. For
an 80Ah battery, this means a 8 amp charge limit.
Cyclic use is where you expect to discharge and recharge the battery
regularly, like at a solar or other off-grid site. For these, you
really want to do a multi-stage charger mainly to fully top off the
battery.
Using the wrong charge method for your application *will* shorten your
battery life.
Just for an example:
The following is an example of a small standby multipurpose battery
datasheet: http://www.brooksequipment.com/files/ps-1270.pdf If you
note in the datasheet, it indicates for standby use, you should float
it. It also explains how to charge in cyclic applications as
well. But if you look at the life characteristics, you're going to
destroy this battery if you cycle it a lot... Even a 30% daily
discharge will result in a lifetime of around 3 years or less,
depending on your choice of when to retire the battery.
On Wed, Mar 9, 2016 at 12:52 PM, Bill Prince <[email protected]
<mailto:[email protected]>> wrote:
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.
--
*Forrest Christian* /CEO//, PacketFlux Technologies, Inc./
Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602
[email protected] <mailto:[email protected]> |
http://www.packetflux.com <http://www.packetflux.com/>
<http://www.linkedin.com/in/fwchristian>
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