[Elecraft] Battery back-up system for multiple rigs

[N2TK, Tony]

Fred,
Where can I find the info on the system AD6CW has suggested?
Tnx
N2TK, Tony

-----Original Message-----
From: Fred Townsend [mailto:fptownsend at earthlink.net] 
Sent: Thursday, January 22, 2015 9:28 PM
To: don at w3fpr.com; 'N2TK, Tony'; elecraft at mailman.qth.net
Subject: RE: [Elecraft] Battery back-up system for multiple rigs

Don and Tony:
Diodes will get the job done but notice the heat sinks on them. They waste a
lot of energy as heat. I also read you have a single charger. I hear no
mention of fusing. Fusing is a good idea but must be done very carefully.
All of these issues are complicated by the placement of the diodes. 

There are specifically designed 'smart' systems out there to do exactly the
job of safely sharing and charging batteries similar to the systems Jim,
AD6CW has suggested. If you lack experience in this area I highly recommend
to you check them out. They offer smart systems that will safely shut things
down using FETs to share and control. The FETs have much, much lower losses
so in this case the ones with diodes and big beefy heat sinks are not your
friend. The also feature both over voltage and under voltage alarms. This
saved me when a power supply regulator shorted. 

73,
Fred, AE6QL

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Don
Wilhelm
Sent: Thursday, January 22, 2015 4:21 PM
To: N2TK, Tony; elecraft at mailman.qth.net
Subject: Re: [Elecraft] Battery back-up system for multiple rigs

Tony,

There is no problem connecting batteries in parallel *if* (and only if) they
are the same capacity, manufacturer and age.

If the batteries are not identical, isolate them with diodes so one does not
draw current from another battery.  You will suffer the diode voltage drop
in the output voltage.  The diodes must be capable of carrying the full
maximum current load for all the rigs that will be operating at the same
time.

73,
Don W3FPR

On 1/22/2015 2:47 PM, N2TK, Tony wrote:
> Looking for some advice. Trying to help out a friend who is setting up 
> an emergency communications system for the Hams in their condo group.
>
> They have several marine batteries they want to tie in parallel so 
> they
can
> run multiple rigs,  K3's plus UHF/VHF for extended periods. They have 
> a charger for the batteries. They use the 12V off the batteries to a 
> distribution box for the 12V equipment.
>
>   
>
> Questions:
>
> -          What is the best way to isolate the equipment from the
batteries
> if something happened to the battery (ies).
>
> -          Is there a way to isolate the batteries from each other if
> something happened to one battery so it didn't draw down the other 
> batteries?
>
> -          Am I missing anything else that should be done for safety of
the
> equipment, batteries and the operators?
>
>   
>
> Tnx
>
> N2TK, Tony
>
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