Fw: (ET) Solar charging, part 2

["Herb Crary" <jhcrary earthlink net>]

Seems to me that a simple solution might be to put a delay circuit in to 
set
a delay between the times the charger is disconnected and can be
reconnecteed.

Herb

----- Original Message -----
From: "harry landis" <hlandis hotmail com>
To: <elec-trak cosmos phy tufts edu>
Sent: Tuesday, April 22, 2003 7:22 PM
Subject: Re: (ET) Solar charging, part 2


>
>
>
> That was the assumption. I just picked the number as an illustration. My
> controller won't work if there is a significant load on the battery while
it
> is trying to charge it.
>
> Harry Landis
>
> From: "Christopher Zach" <czach computer org>
> To: "harry landis" <hlandis hotmail com>, <elec-trak cosmos phy tufts 
> edu>
> Subject: Re: (ET) Solar charging, part 2
> Date: Tue, 22 Apr 2003 22:02:59 -0400
>
> Why is there a 1 amp load on the pack constantly?
>
> Chris
>
> ----- Original Message -----
> From: "harry landis" <hlandis hotmail com>
> To: <elec-trak cosmos phy tufts edu>
> Sent: Tuesday, April 22, 2003 9:52 PM
> Subject: RE: (ET) Solar charging, part 2
>
>
>  >
>  >
>  >
>  > Say there is a constant 1 amp load on the battery pack while the 
> panels
> are
>  > trying to charge it. Say the panels can put out 5 amps. Say the
batteries
>  > are fully charged. As soon as the controller turns off the panels, the
>  > battery voltage will fall a little below the quiescent voltage of 38
> volts,
>  > so the controller reconnects the panels for 5 minutes. Now the battery
is
>  > being charged at 4 amps net. This will repeat as long as the panels 
> can
> put
>  > out power. So the panels will be connected essentially continuously,
and
> so
>  > the batteries will get overcharged.
>  >
>  > My controller expects to be looking at the resting voltage of the 
> pack.
> If
>  > it is looking at some other voltage, like the resting voltage minus
some
>  > voltage drop due to current being drawn, it will not be able to do its
> job
>  > correctly.
>  > The current draw is a few milliamps.
>  >
>  > Harry Landis
>  >
>  >
>  >
>  > From: "Humphrey, Timothy" <HumphreyT neads ang af mil>
>  > To: "'elec-trak cosmos phy tufts edu '"
<elec-trak cosmos phy tufts edu>
>  > Subject: RE: (ET) Solar charging, part 2
>  > Date: Tue, 22 Apr 2003 21:19:57 -0000
>  >
>  > I know it's your charger, you built it so you should know how it 
> works.
> But,
>  > I'll have to disagree that it will over charge an in use battery.
>  >
>  > If the battery is being drawn from, I agree it's voltage will be low
and
> as
>  > such your control will either stay on or keep turning on. But, if that
is
>  > happening, then it is not charging the battery. It is merely causing
the
>  > charger or solar panels to share the load with the battery. As soon as
> the
>  > load is removed the controller will start to function as required. You
> can't
>  > charge a discharging battery.
>  >
>  > One question I have about using it on solar panels though, is how much
> power
>  > does the controller consume itself? If it turns on at night, what kind
of
>  > drain will it present to the battery. It gets it's operating power 
> from
> the
>  > battery, right? I know it could probably run itself for a decade or 
> two
> on
>  > the ET's pack, but should those using solar panels consider a dimlight
>  > disconnect, in order to keep what they just put in?
>  >
>  > Oh, and by the way, you'll be receiving my order for one soon.
>  >
>  > Stay Charged!
>  >
>  > Hump
>  >
>  >
>  >
>  > -----Original Message-----
>  > From: harry landis
>  > To: elec-trak cosmos phy tufts edu
>  > Sent: 4/22/03 4:29 PM
>  > Subject: Re: (ET) Solar charging, part 2
>  >
>  >
>  > I think my controller would work fine with a DC solid state relay
>  > instead of
>  > the AC one. As it happens, I have some DC SSRs available. So if anyone
>  > wants
>  > a controller with a DC SSR (30 amps, I think) just ask. Same price 
> ($40
>  > including shipping). Note: this control scheme won't work on a normal
>  > solar
>  > installation. It only works in applications like the ET where there is
>  > essentially no power drain on the batteries while charging. If there 
> is
>  > significant current being taken from the batteries, the battery 
> voltage
>  > is
>  > no longer the rest voltage, but is lower due to the drain. So the
>  > controller
>  > thinks the battery is always low, and ends up overcharging it.
>  >
>  > Harry Landis
>  >
>  >
>  >
>  >
>  >
>  > From: Jeremy Gagliardi com
>  > To: elec-trak cosmos phy tufts edu
>  > Subject: Re: (ET) Solar charging, part 2
>  > Date: Tue, 22 Apr 2003 16:04:28 -0400 (EDT)
>  >
>  > On Tue, 22 Apr 2003 16:00:07 -0400, "SteveS" wrote:
>  >   > Yes, at the relatively low currents that we are talking about (5A
or
>  > so),
>  >   > there are inexpensive controllers one could make or buy. Now, 
> where
>  > do we
>  >   > buy cheap (err, inexpensive) solar panels?
>  >   > SteveS
>  >   > E12Ss
>  >   > E20
>  >
>  > Okay, now the next question is who can build one (Harry Landis, are 
> you
>  > up
>  > to
>  > the task)?  I haven't dabbled in electronics since I took a required
>  > course
>  > in
>  > college for my CompSci degree.  That was 11 years ago, and I don't
>  > remember
>  > a
>  > lick of it.  Although, if someone drew up a schematic, I might be able
>  > to
>  > follow
>  > it.
>  >
>  > --
>  > Jeremy
>  > E20
>  >
>  >   > > This makes me wonder if it would be simpler to build a simple DC
>  >   > controller,
>  >   > > similar to the Landis model.  The Landis Controller is a solid
>  > state AC
>  >   > relay
>  >   > > with a simple DC monitor (when batteries go below 38V it turns 
> on
>  > the
>  > AC
>  >   > relay
>  >   > > to the charger).  Can't a similar controller be built that
monitors
>  > the
>  >   > > batteries in the same exact way, but opens up a DC relay from 
> the
>  > solar
>  >   > panels?
>  >   > > The Landis Controller is only about $40.
>  >
>  >
>  >
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