Solar Energy Charger Question

[RealInfo]

Hi all

How battery chargers for solar photo voltaic based system work ?

I ask this because the voltage that comes from the photo voltatic paltes
varies according to sun light srength day/mid day evening
and night ...

So how this fact is treated for the charger design that has to deal with
changing input volatge to it ?
what is the common answer to this ?

any component that does this job ?

Thanks
EC

 

[Dave Platt]

Hi all

How battery chargers for solar photo voltaic based system work ?

I ask this because the voltage that comes from the photo voltatic paltes
varies according to sun light srength day/mid day evening
and night ...

So how this fact is treated for the charger design that has to deal with
changing input volatge to it ?
what is the common answer to this ?

any component that does this job ?

There are several ways of going about it.

One thing to remember is that the voltage delivered by a solar panel
varies greatly depending in the amount of current it's delivering.
Panels for charging of 12-volt batteries usually have an "open
circuit" voltage output of 15-18 volts. However, this voltage drops
quite a lot when you're drawing current approaching the panel's
maximum output... if you short-circuit the panel's output leads, you
end up with essentially 0 volts output, and a maximum amount of
current flowing through the panel and the short (and all of the power
thereby turning into heat and IR in the panel and wiring).

Small, simple solar "trickle chargers" have a low maximum current
output. Chargers of this sort often have no voltage regulation at
all... they're simply connected to the battery through an
anti-reversal diode (and some even omit the diode!). The idea here is
that the battery's terminal voltage (which rises as the battery
charges) never actually rises all that high... the panel's current
output is low enough that it just counteracts the battery's charging
loss and self-discharge, without overcharging the battery enough to
cause it to start electrolyzing away its precious bodily fluids.

Lower-cost chargers with larger panels (ones which deliver enough
current to actually recharge the battery in reasonable time, and thus
possibly capable of overcharging the battery) tend to use some form of
linear voltage regulator. They may use a "series" regulator (perhaps
something like an LM317), which sits between the panel and the battery
and limits the current flow through the regulator so that the battery
terminal voltage doesn't rise too high. Some use a "shunt" regulator
(something like a large zener diode) which sits in parallel with the
battery, "clamping" the voltage and dissipating any excess power from
the panel as heat. The shunt regulator generates more waste heat when
the battery is fully charged (or disconnected), but has little or no
waste when the battery is low and is actively being charged by the
panel. The series regulator is the other way around... it generates
relatively little heat when the battery is not being charged, but can
waste a good deal of power during active charging (depending on its
design).

The most sophisticated charge controllers I've seen are "switching"
regulators, which can accept a wide range of panel voltages and
deliver a well-regulated voltage to the battery with relatively little
power loss in the regulator itself. These regulators can even
transform down the power delivered by the panel, to a lower voltage at
a higher current, thus leading to greater charging efficiency than
you'd get if you use a linear regulator or let the panel limit itself
under heavy load. These switching controllers are the sort that
you'll usually seen used in large "off the grid" solar panel
applications.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[RealInfo]

Thanks
EC

"Dave Platt" <dplatt@radagast.org> ëúá áäĺăňä:a4cl86-djo.ln1@radagast.org...

Hi all

How battery chargers for solar photo voltaic based system work ?

I ask this because the voltage that comes from the photo voltatic paltes
varies according to sun light srength day/mid day evening
and night ...

So how this fact is treated for the charger design that has to deal with
changing input volatge to it ?
what is the common answer to this ?

any component that does this job ?

There are several ways of going about it.

One thing to remember is that the voltage delivered by a solar panel
varies greatly depending in the amount of current it's delivering.
Panels for charging of 12-volt batteries usually have an "open
circuit" voltage output of 15-18 volts. However, this voltage drops
quite a lot when you're drawing current approaching the panel's
maximum output... if you short-circuit the panel's output leads, you
end up with essentially 0 volts output, and a maximum amount of
current flowing through the panel and the short (and all of the power
thereby turning into heat and IR in the panel and wiring).

Small, simple solar "trickle chargers" have a low maximum current
output. Chargers of this sort often have no voltage regulation at
all... they're simply connected to the battery through an
anti-reversal diode (and some even omit the diode!). The idea here is
that the battery's terminal voltage (which rises as the battery
charges) never actually rises all that high... the panel's current
output is low enough that it just counteracts the battery's charging
loss and self-discharge, without overcharging the battery enough to
cause it to start electrolyzing away its precious bodily fluids.

Lower-cost chargers with larger panels (ones which deliver enough
current to actually recharge the battery in reasonable time, and thus
possibly capable of overcharging the battery) tend to use some form of
linear voltage regulator. They may use a "series" regulator (perhaps
something like an LM317), which sits between the panel and the battery
and limits the current flow through the regulator so that the battery
terminal voltage doesn't rise too high. Some use a "shunt" regulator
(something like a large zener diode) which sits in parallel with the
battery, "clamping" the voltage and dissipating any excess power from
the panel as heat. The shunt regulator generates more waste heat when
the battery is fully charged (or disconnected), but has little or no
waste when the battery is low and is actively being charged by the
panel. The series regulator is the other way around... it generates
relatively little heat when the battery is not being charged, but can
waste a good deal of power during active charging (depending on its
design).

The most sophisticated charge controllers I've seen are "switching"
regulators, which can accept a wide range of panel voltages and
deliver a well-regulated voltage to the battery with relatively little
power loss in the regulator itself. These regulators can even
transform down the power delivered by the panel, to a lower voltage at
a higher current, thus leading to greater charging efficiency than
you'd get if you use a linear regulator or let the panel limit itself
under heavy load. These switching controllers are the sort that
you'll usually seen used in large "off the grid" solar panel
applications.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!