Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Auto battery transfer questions  (Read 5289 times)
K8WTF
Member

Posts: 12




Ignore
« on: November 04, 2011, 02:13:55 PM »

Hello all -

I'm setting up a basic emergency power system consisting of 2x 38Ah AGM batteries and a Battery Tender.  The piece I am working on currently is how to transfer from my power supply to the battery bank. I will be feeding my HF and VHF radios, although in an emergency I would likely just use VHF.  Either way, about 22 amp max draw on my HF radio during transmit and about 12 on VHF.

My two initial thoughts are -

1) Use a high amperage SPDT switch.  Simple.  Effective.

2) Build a relay-controlled transfer switch that would automatically switch the load over to battery when the power supply stops producing 12vdc.

Both are pretty simple to set up, but my concerns around #2 are the duty cycle of the relays and how my equipment would handle an instantaneous drop and then re-application of power, where the resulting voltage will probably be a volt or more lower after the cutover.

Because of the above I'm leaning towards #1, but I'm curious how others have handled keeping the two systems separate. 
Logged
W8JX
Member

Posts: 5492




Ignore
« Reply #1 on: November 04, 2011, 03:17:26 PM »

Both are pretty simple to set up, but my concerns around #2 are the duty cycle of the relays and how my equipment would handle an instantaneous drop and then re-application of power, where the resulting voltage will probably be a volt or more lower after the cutover.

Relay duty cycle is not a issue at all and as far as change over there is a real easy fix for this too. Simply use about a 100,000uf or better electrolytic capacitor in parallel with radio feed after change over relay. It will easily power rig during change over and you will never miss a beat.
Logged

--------------------------------------
Entered using a  WiFi Win 8.1 RT tablet or a Android tablet using 4G/LTE or WiFi.
LA9XSA
Member

Posts: 376




Ignore
« Reply #2 on: November 04, 2011, 04:28:50 PM »

You could also use diodes. A diode package, heat sink and a current limiting resistor would make something similar to the old "PWRgate" design (the one without the three-stage battery charger), which would both float-charge the battery and change over in case the battery or PSU fails.
Logged
KG4RUL
Member

Posts: 2688


WWW

Ignore
« Reply #3 on: November 05, 2011, 12:29:35 PM »

ISOpwr - Auxiliary Battery Isolator
#58401-1044

$79.95

   
  • Isolates and charges a 12 Volt auxiliary battery to run mobile radio and other 12 Volt portable equipment.
  • Ideal for mobile radio command stations for ARES, RACES, FEMA, and for a VHF/UHF Contest Rovers, moderately powered ham equipment, a re-charging station for electric model airplanes, boats and cars, and for RV's and campers.
  • ISOpwr turns ON when the power supply is ON and providing over 13.5 volts.
  • ISOpwr turns OFF when the power supply is OFF or providing below 12.7 volts.
  • All solid state. FET switch. No relays. Handles up to 40 amperes. Input fuse 40 A.
  • Works safely with all types of 12-volt lead-acid batteries, Flooded Lead Acid, Gelled & AGM.
  • May be used without a battery to automatically turn a radio on whenever the power supply is turned ON. The radio will turn off with a small delay after the power supply is turned OFF.

I did a little editing to the description to describe how it can be used with an AC power supply (nominal 13.8VDC) instead of the car alternator/battery.

Dimensions: 4" x 5" x 1.5"

http://www.westmountainradio.com/product_info.php?products_id=iso_pwr
Logged
K9KJM
Member

Posts: 2416




Ignore
« Reply #4 on: November 05, 2011, 10:03:51 PM »

Many years ago I made the switch to battery power and have not looked back or regretted it in any way.

I use the KISS formula.   Keep it simple........

I run my entire ham shack including radios, Scanners, LED lights, etc ( And a few local repeaters at remote locations too) DIRECTLY from a 12 volt DEEP CYCLE marine type battery.  (The SLA/AGM type batteries are better, But cost more)

The "secret" to making it work is to have a good fully automatic type charger on the battery. One that shuts right off when the battery is fully charged.  I use 10 amp Schumacher, Around 39 bucks when on sale.
(The battery tender type trickle charger is not the correct way to do it)
Use heavy wire from the battery with a fuse right near the battery, I keep the battery in a plastic marine battery box right indoors.    There is no "outgas" from batteries in this type use UNLESS there has been a commercial power failure and when the power comes back on the battery goes into a fast type charge.  During such conditions if they ever happen, Do provide good ventilation for the battery and dont have any sparks near it.

Under normal operating conditions, The charger is keeping the battery well above the nominal 12 volts, And radios work just fine.   If a commercial power failure happens, My radios work fine with any reasonable T/R duty cycle for at least 8 or so hours, Plenty of time for me to get a generator started before the battery drops down to a voltage lower than the radios want to see.

I sold my Astron power supply many years ago.    Why have both types at all?

JX's plan: Simply use about a 100,000uf or better electrolytic capacitor in parallel with radio feed after change over relay. It will easily power rig during change over and you will never miss a beat.
Is a good one to add also.
« Last Edit: November 05, 2011, 10:07:48 PM by K9KJM » Logged
K8WTF
Member

Posts: 12




Ignore
« Reply #5 on: November 06, 2011, 07:00:04 PM »

I think I am going with the relay and capacitor option.  My father found a heavy duty relay with a 120vac coil in his junk box, so all I need to find is a decent sized capacitor to put in parallel in-between the switch and my fuse block.

I also like the idea of running full-time off of batteries, but my intent for now is to keep the system isolated and the batteries maintained.  Ultimately I want to put up some solar panels to run the shack.

If I was starting over I would probably just buy a PWRGate, but, I just haven't had good luck with anything relating to powerpoles.

Thank you everyone for your ideas.
Logged
K8WTF
Member

Posts: 12




Ignore
« Reply #6 on: November 06, 2011, 07:07:23 PM »

KJM - Out of curiousity, how many amphours of capacity do you have in your battery bank?  I assume the charger you use handles "fighting" the load?
Logged
K9KJM
Member

Posts: 2416




Ignore
« Reply #7 on: November 08, 2011, 10:04:13 PM »

KJM - Out of curiousity, how many amphours of capacity do you have in your battery bank?  I assume the charger you use handles "fighting" the load?

I learned years ago to simply use a single battery.   So I do not have a "bank" of multiple batteries.
Trying to run two or more batteries of the same voltage in parallel eventually results in the weaker battery pulling the others down.......   On paper, With matched batteries, Operating batteries in parallel works fine.  Out here in the real world with old mismatched batteries, Not so much.

A single marine type deep cycle battery (About the same physical size as the typical auto battery) powers my entire hamshack for more than 8 hours with any reasonable T/R duty cycle. The actual amp hour capacity of the battery depends on just what the local farm and fleet store happens to have on sale when I need one.....    Which on average is about once every 6 or so years.

IF more amperage were needed than a single battery could supply, I would go with a larger battery, Or better yet, A pair of 6 volt deep cycle batteries wired in series (Golf cart type batteries)

Yes, The 10 amp automatic type charger almost handles the entire load during transmit (Total draw of all stuff in the hamshack even at high power only comes to around 15 or so amps)  So with even a 50% T/R duty cycle, The battery never gets drawn down.
Logged
W8JX
Member

Posts: 5492




Ignore
« Reply #8 on: November 09, 2011, 06:31:27 AM »

I learned years ago to simply use a single battery.   So I do not have a "bank" of multiple batteries. Trying to run two or more batteries of the same voltage in parallel eventually results in the weaker battery pulling the others down.......   On paper, With matched batteries, Operating batteries in parallel works fine.  Out here in the real world with old mismatched batteries, Not so much.

I have not found this to be case. In nearly 25 years of using dual batteries in trucks/SUV's for ham radio and snow plow equipment. I have never had a problem but one time and that was when one battery had a cell go bad and drained other one to 10.8 volts too. This was kinda my fault too in that vehicle was sitting for over a month and while I normally would isolate them (ie so I can run stationary HF mobile and not worry about killing main battery) in this particular vehicle when sitting for a long period of time I did not this time. Batteries are rarely matching in brand or size and I have never bought two at once.

One must remember that a battery IS NOT like a glass of water in that you will not get same amount of energy regardless of rate of "emptying" it. In the real world you will see more total run time with 2 or more batteries in parallel than you will using same batteries one at a time. Under heavy discharge rates the difference is even more pronounced. 
Logged

--------------------------------------
Entered using a  WiFi Win 8.1 RT tablet or a Android tablet using 4G/LTE or WiFi.
K7RBW
Member

Posts: 386




Ignore
« Reply #9 on: November 10, 2011, 08:21:24 AM »

Yes, The 10 amp automatic type charger almost handles the entire load during transmit (Total draw of all stuff in the hamshack even at high power only comes to around 15 or so amps)  So with even a 50% T/R duty cycle, The battery never gets drawn down.

...the caveat to this option is to pick the right battery charger. I've had some that are clean and others that have a lot of AC ripple coming out of them. The AC ripple doesn't bother the battery, but it can make for an annoying hum on the radio.
Logged
K8WTF
Member

Posts: 12




Ignore
« Reply #10 on: November 12, 2011, 05:24:21 PM »

Trying to run two or more batteries of the same voltage in parallel eventually results in the weaker battery pulling the others down.......   On paper, With matched batteries, Operating batteries in parallel works fine.  Out here in the real world with old mismatched batteries, Not so much.

The two I ended up with are a "almost brand new" set and have always been tied together, so I'm not too worried about that.

For now I've gone with a simple toggle switch rated for 50 amps to switch between batteries and my power supply.  I've been running on battery all day with minimal voltage drop, so I think ultimately my plan is to operate off of battery full time with a good non-noisy charger.  The one I'm using now, albeit only 1.25 amps (A "Battery Tender Plus") I picked up specifically because of good reviews here at eHam. 
Logged
KB1GMX
Member

Posts: 718




Ignore
« Reply #11 on: November 13, 2011, 10:41:31 AM »

I went a slightly different route.  Solar panel to keep the battery up was initially 20W and a charger top it off.  Later added more solar (50W panel) and didn't need the charger as I was at the C10 rate and then some.  System has a charge controller to prevent over charge.  Batteries were a pair of wet 38Ah lead batteries with venting out doors(battery box with 1" tube through the wall and a mini fan) . Since then thy have been replaced with a lucky find of pristine set of 150AH wet NiCds and I've added another 80W of solar (150W total).  That setup runs the radios save for one high power VHF amp that wants 48V (looking for a 13.5V to 48V 600W supply). 

The 38ah wet batteries are kept now in the three season room with a VW 3W panel each to keep
them good for odd uses like field day as they are fairly portable.   Those panels are cheap and good enough to keep things like the lawn tractor good when it sits.

That setup runs the VHF radios, UHF radio, and HF radios, one ITX computer(logging and psk31)
plus basic lights and an optional 200W inverter for the odd line powered need, like soldering.


Allison
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!