[TenTec] Help with gel cell battery and solar charging system....

[Ken Brown]

Hi John,

     I recommend Home Power Magazine. If you can find someone who 
subscribes, who would let you borrow a bunch of issues, or a library 
that has it, you can learn plenty about these kinds of systems. Even 
without subscribing you can get a lot of information on their web site. 
You can also get a package deal including past issues on CD if you 
subscribe. There is lots and lots of information there.

     If you intend to run your radio directly from the batteries, not 
using an inverter and 120 VAC, then you probably want a 12 VDC battery 
system. You would probably use 12 V photovoltaic panels. A MPPT ( 
maximum power point tracking) charge controller between the photovoltaic 
panels and the battery will possibly be a source of RF noise, since they 
are switched mode voltage converters that can get some charge current 
into your batteries, even when the voltage coming out of the PV panels 
is lower than the battery voltage. Since these charge controllers are 
voltage conversion devices, your PV panels may not have to be a 12 volt 
system to use a 12 volt battery. You can also use DC to DC voltage 
conversion from the battery to the radio, another possible noise source, 
but also another possible way to have higher current at the load with a 
higher voltage lower current capacity battery.

      By using a 12 volt battery system, you could operate the radio 
directly off the battery, with no switched mode voltage conversions 
running at night when the sun is down. A nominal 12 volt battery system 
will drop below 12.6 volts output when there is still a lot of available 
energy left in it.  Low voltage cutouts to protect the battery from 
excessive discharge are typically a bit under 12 volts for a nominally 
12 volt battery system. But will the Orion II still be working at that 
voltage? You need to find out what DC voltage the Orion II really needs 
to work properly. A six cell battery system may not actually provide 
that voltage for very long. You may need a DC to DC converter between 
the battery and the load anyway, in which case you may want to consider 
a higher voltage battery. 24 volt and 48 volt systems are pretty common 
these days. 12 volt systems getting less and less common anymore when 
inverting to 120 VAC. By using higher voltage PV arrays and batteries, 
you can use smaller wire. Twelve volt systems these days seem to be only 
use for very small systems with only one or two PV panels in the array.

     The simplest system for you would probably be one or more 12 Volt 
PV panels, a charge controller and a 12 volt battery of the necessary 
Ampere Hour capacity, which depends on your usage. You may also want 
another way to charge the batteries when you get a lot of cloudy weather.

     QST had an article about 12 VDC to 120 VAC inverters recently, 
which was the best description of the difference between 'True sine 
wave" inverters and modified square wave inverters (which the inverter 
manufacturers marketing departments call "modified sine wave") I have 
seen. The renewable energy folks at Home Power Magazine and other 
information sources often only discuss that difference in terms of what 
devices you can power, and not so much discussion about the generation 
of RF noise.

     If you have a safe place to keep your battery, which includes 
venting and a way to contain any possible electrolyte spillage, then I 
would go with a liquid electrolyte lead acid battery. Plain liquid 
electrolyte batteries are a bit more tolerant to accidental abuse than 
gel cells, and for the same capacity they are usually cheaper. If you 
overcharge or charge at too high a rate you may evaporate some 
electrolyte. With a liquid cell you can replace it by adding some 
distilled water. With a sealed gel cell battery, if you vent any water 
vapor from the gel electrolyte, it is gone forever, and the battery will 
never be the same.

Ken N6KB

John Frazier wrote:
> Hi folks....
>
> Looking for someone who has experience with choosing a gel cell battery and solar charging system for running home station (Orion II).
>
> Please email me at....   fraz1 at bellsouth.net
>
> 73 John W4II
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