Subject: Re: DBAm: Solar Panels and Charging when on Land Line
All modern charging devices can be connected together without the need to
connect through a diode because they will already have rectifying diodes or
are diodes themselves and can't back feed. The device that is charging at
the highest voltage will deliver the most current up to its limit and that
voltage will depend on the regulator of the device. A wind generator and
solar cells could be put through the same regulator up to the total current
rating as this is a simpler device. The alternator regulator only needs to
be a standard type and only needs an add on regulator if the voltage is too
low and no higher alternative regulator is available, it does not need a
float charge function. The shore charger will usually have added functions
like bulk and float charging which is necessary if on standby.
The windgenerator and solar cells will produce a low current but this can be
for a long time and can add up and is free. An alternator or charger will
produce high currents and charge quickly and maintain a fully charge battery
but have a running cost. The problem is deciding whether and how to use the
free power which is not usually enough for all daily needs. A consideration
is the fact that if using the batteries there is an inherent loss that needs
to be balanced against the free gain.
To ensure maximum use of free power it would probably make sense to only use
the shore power when really needed such as when the batteries were getting
too low or when using a high load same as when away from shore and would use
the generator. Using a time switch or manually might be the only way for
this.
Batteries can be recharged at any state and the belief that they have to be
discharged fully first probably comes from an unfortunately worded website
that says batteries should be recharged when a certain percentage is
reached, only meaning don't discharge beyond that! Sulphating, e.g.
hardening of the sulphate preventing a full reversal of the chemical charge
process only occurs if the battery is left in a discharge condition for any
time and has nothing to do with when the battery is recharged. Frequent
recharging is therefore better and solar or wind power is ideal for this
within the capacity.
Terry.
>I cannot help feeling that there is more to it than that. I would not go
>the
> diode route due to the voltage drop through the diodes. To a certain
> extent,
> most charging devices output more when the batteries are low (I will
> probably be corrected by the techies here!). On that basis, whenever we
> take
> anything out of the batteries, the Phoenix Multipluses go into bulk charge
> and then absorption, thus bringing the batteries back to full charge very
> quickly. Most of the time, the Mulitpluses are on float which would mean
> that whilst you could have output from the solar panels "taking first
> choice" the batteries would be full anyway.
>
> I am not aware of being able to turn the Multiplus charger element off.
> The
> options are everything on, charger only or everything off.
>
> I wonder if a simple solution would be to put the shore line through a
> simple time switch so that it was only on during the night, with an
> override
> if a heavy load was anticipated. An immersion heater timer would carry a
> 13A
> load and have an override.
>
> David Heath
> Mirage
>
> -----Original Message-----
> From:
dbamain-bounces@...
> [mailto:
dbamain-bounces@...] On Behalf Of Terry McMahon
> Sent: 30 June 2008 00:24
> To:
DBAMAIN@...
> Subject: Re: DBAm: Solar Panels and Charging when on Land Line
>
> Ian, there is a simple answer to keep the current isolated from each of
> the
> various sources. There is a diode isolater which will perform this
> function. You can get them with 2 or 3 inputs and one output. This
> way the current sources will not buck each other. Also, when I had the
> solar panels, wind generator, and gen set and alternators all charging my
> batteries, I had regulators on the output of my alternators, solar panels
> and wind generator so that when any of these sense full battery charge
> they
> will shut down.
>
> Regards
> Terry McMahon
>
> Ian Petchey wrote:
>
>>David,
>>
>>We installed 2 x 130w solar panels 6 weeks ago.
>>They charge the batteries even when plugged into shore power, and our
>>Victron multi is 'charging'. I have seen through our battery monitor
>>(for
>>example) +1amp input into batteries. The solar controller saying 5 amp
>>input. When I disconnect the solar panels I get -4amp for a short
>>period, before the Victron charger kicks in and puts a few amps
>>in...... This when the batteries are fully charged.
>>
>>Whether the Victron is super intelligent to know another charge takes
>>priority, or whether our solar panel controller Steca 15a does the
>>trick I do not know...... But it works.
>>
>>For info I am averaging around 1Kwh per day from the two 130w panels
>>(Kyocera). Worst days around 250wh, best 1.3kwh.
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