[Elecraft] Battery Charging with DC Power Supply

[dave]

A voltage as low as 12.anything will result in a sulfated battery. The 
lowest float voltage I am aware of is 13.02 (2.17 VPC) on the 
Rolls/Surrette batteries. All other manufacturers (that I am aware of) 
recommend something closer to 13.5 or so. Don't listen to me or anyone 
else on here - check the manufacturer's recommendations!!

Yes, if you run your power supply at 13.5 or 13.4 to do a float charge 
a battery you will likely lose a little maximum power out. But there 
should be no harm to the rig. Instead of getting 100w out you may get 
only 90 or so. But this is only about 0.5 dB and undetectable on the 
RX end. A small price to pay for having continuous backup power, or so 
it seems to me - YMMV. I think most rigs have an adjustment for the 
power out - if you can find it!

Remember what you are trying to do is keep the battery fully charged 
without cooking the water out nor damaging the plates. If you watch 
the water consumption you can tell if the float voltage is too high. 
If you have to add water more than about once a year the voltage is 
too high. I try to keep the float voltage about 13.5 or 13.6 and add 
water only every couple of years to the ones here.

A voltage too low is much harder to detect. The only sign is loss of 
capacity in the battery due to sulfation. The only valid test I know 
of is to do a load test. So it is better to err a bit on the high side 
and watch the water consumption then to sulfate the battery.

Re: the Jetstream switching supplies. A friend brought one by and we 
took a look at it with the spectrum analyzer. That one was a horrible 
noise producer. Lots of spurs well up into the VHF frequencies.


73 de dave
ab9ca/4




WILLIS COOKE wrote:
> Be careful.  There is a voltage that is safe for trickle charging a
> battery, but it is not the same voltage that is optimum for
> powering a transceiver.  Most if not all transceivers are built for
> optimum operation at about 13.8 volts which is also the optimum
> charging voltage for a short term charge of your car battery.  They
> also work well at 12 volts or a little less so that you can use a
> car battery when you are not running the engine.  Most of us keep
> our power supply adjusted to about 13.8V which is a good voltage
> for battery charging, but not so good for continuous charge.  You
> will ruin a battery if you keep the voltage that high for long
> periods.  I don't have the battery specs on hand at the moment but
> something like 12.3 to 12.5V would be a good continuous voltage.
> Also, you have the challenge of connecting at least two large wires
> to the output terminals of the charger which is difficult on some
> chargers.  The Astron supply that I have has some nice large bolts
> for connectors, but others have binding posts that are more
> difficult.
> 
> A better solution is to have a separate power supply output for the
> battery charger and a variable charge circuit to restore the charge
> after use then reduce the charging voltage for maintenance.  Such a
> supply is made by JetStream, Model JTPS35BCM and probably others.
> I am in the process of installing one in my shack at the moment.
> It is reasonably priced and seems a good idea,  I will let you know
> later how well it works.
> 
> Willis 'Cookie' Cooke K5EWJ
> 
> 
> --- On Mon, 6/8/09, Wes Stewart <n7ws at yahoo.com> wrote:
> 
>> From: Wes Stewart <n7ws at yahoo.com> Subject: Re: [Elecraft]
>> Battery Charging with DC Power Supply To:
>> Elecraft at mailman.qth.net Date: Monday, June 8, 2009, 7:40 AM 
>> Finally, a voice of reason.
>> 
> 
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