[aprssig] Re: Charge controllers

Dale Blanchard wa7ixk at earthlink.net
Fri Apr 29 21:27:10 EDT 2005

On one of our sites we use a big swichting supply for the radios.
We have 3 banks of batteries seperate for each system so only one dies 
at a time.
Back up power comes thru a big schottky diode from each bank.
The batteries are charged and floated with a smart charger on each bank.
Completly isolated from the main power source and each other.
Motorola used to float the older lead acid wet cell at 13.6 volt so you 
only had to add water
every 3 months. The newer lead calcium can use 13.8V. with very little 
water loss.
With AGM/SLA 13.6 to 13.8v float works till the battery dies .

On my home station I use a 3 amp computer supply set to float at 13.8 V 
a Panasonic AGM battery. I run my 100 w hf rig and my vhf and uhf radios
from one 20 ah battery. Quit using my Motorola switching supplies

Stephen H. Smith wrote:

> ad6nh at arrl.net wrote:
>> Well, speaking of charge controllers (I think we were speaking of 
>> them here a few days ago), does anyone have a source for a simple 
>> charge controller that I can use between an Astron P/S and a 
>> battery?  I'm looking for an affordable backup power option - the 
>> West Mountain Radio PwrGate is nice, but it's a bit pricey.  Many of 
>> the charge controllers I'm finding on Google are of the variety for 
>> solar panel charging, and are very expensive.  This is for a 
>> digipeater site that is subject to power outages and needs battery 
>> backup.  The idea was to have the Astron go through the charge 
>> controller to the battery, and the digi hooks direct to the battery.  
>> Thanks!
> As long as the power supply is well regulated, you don't need a charge 
> controller at all.   Use a good digital voltmeter to set the supply 
> output at about 13.2 volts and connect both the battery and the load 
> directly across the supply.  At 13.2 volts, the battery terminal 
> voltage will rise to exactly match the supply voltage when the battery 
> reaches full charge.  With the supply and battery terminal voltages 
> equal, the battery will stop drawing current and can be floated 
> indefinitely.      You DO want some sort of maximum current limiting 
> in the supply, so that when the AC power comes on after the battery 
> has been partially discharged, you don't get an infinite inrush 
> current that will overheat the supply or blow a fuse.  Further, you 
> may want a low-voltage disconnect controller to prevent the batteries 
> from discharging during a power outage  to such a low voltage that 
> they get permanently damaged.
> You really only need charge controllers when the charging source can 
> potentially produce a voltage well above the battery voltage (such as 
> a solar panel or simple transformer/rectifier battery charger) that 
> can continue to force high current into the battery, even after it has 
> reached full charge.   That is, if the charge voltage is high enough 
> that the battery voltage can never rise to match it, the voltage 
> difference will cause a large current to flow into the batteries 
> indefinitely.
> This floating of batteries directly across the load with a 
> WELL-REGULATED precisely-set power supply is done all the time in 
> telecomm sites.

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