Re: (ET) Solar charging, part 2

["Christopher Zach" <czach computer org>]

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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