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Old 06-24-2008, 08:35 AM   #1
Richard Stouffer
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Default Parallel Battery to Power Supply for Current Reserve

Iím trying to figure out how to set up a battery as a reserve power source for my dedicated power supply for my amplifier. The power supply is an Astron RS-70M rated at 57 amps continuous/90 amps peak. It is driving an SG-500 SmartPowerCube amp. The amp trips when the draw exceeds the available current and a reset requires cycling the power switch. It doesnít happen very often, but it certainly would create problems in a remote set up.
Using a battery for the reserve seemed to make the most sense as it provides an emergency power supply so I have purchased a 108 AHr, deep cycle, AGM battery. I was planning to charge the battery with the power supply. The power supply manufacturer, however, said that I would need to place a blocking diode between the power supply and the battery to protect the power supply in the event of a power failure.
Any of you guys familiar with such a set up?

Thanks,
Richard- WU5K
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Old 06-25-2008, 07:00 AM   #2
wa8yxm
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I have done it a few times myself, There are several issues that come to mind however
First: the blocking diode will cause a slight voltage drop from the power supply to the radio, this can usually be adjusted out however. Second the battery has a "Voltage range" use of a single voltage converter (power supply) is NOT recommended. To properly charge and maintain the battery you need at the least a 2-stage. or 3 or 4 stage charger Thus the single stage (Single voltage) power supply you have is not a good choice in this configuration.

The stages of charging are: 1: Bulk, In this stage you limit current to no more than 30% of the battery's 20 hour amp hour capacity IE, if it is a 90 amp hour battery 27 amps.

2: Absorption: IN this stage the battery limits current however we limit voltage, Usually to something around 14.2 or 14.4 depending on the type of battery (Check with you battery maker for specifics for your battery)

3: Float, In this stage we limit voltage, battery float voltage is normally around 13.4-13.6

3: Equalizaiton.. We do not NORMALLY do this with an AGM.. This is a controlled overcharge, both current and voltage are limited, consult your battery maker's spec sheets for you battery should you need to use this charging mode.

So, who do we do this.....

Well.. With flooded wet cells I suggest a Progressive Dynamics 9200 series, in your case since the rig trips the breaker on a 52 amp supply I'd suggest a 9260 or 9280 but you have AGM type batteries and the PD's are not programmed for AGMs

Xantrex makes some programmable types however I don't know the models for stand alone converters. (I use a prosine 2.0 on my AGMs but it not only charges them, very nicely, it discharges them too.. VERY QUICKLY if I happen to be microvaving lunch )

OH, one last comment.. The difference between a 2 stage and a 3 stage charger/converter is that stage 1 and 2 are combined.. Many converter/chargers limit both current and voltage in the 1st stage with the converter limiting current in stage one and voltage in stage 2, but the limits are identical in both stages.. This is a 2-stage charger
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Old 06-25-2008, 09:03 AM   #3
Richard Stouffer
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Wow! I'm glad I asked. I'll do some research and see what I need to do, but I'm really glad I didn't try anything without the advice of an expert.

Thanks tons,
Richard- WU5K
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Old 06-26-2008, 06:20 AM   #4
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I should add, When I did it I basically used the battery as the PRIMARY source and floated it on a charger. As I said it worked, However I found the battery did not last as long as I had expected (And those big blocks of lead are expensive)

Today, thanks to the research I did into my RV.. I know why. A single voltage charger can not properly maintain a battery

One option might be to set the power supply at the FLOAT voltage of the battery (Allowing for the blocking diode of course) and use a "Battery Minder" (Around 20-100 dollars) to provide the absorption charge on the battery... I think this should work so long as the radio is not turned on 24 x 7
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Old 06-26-2008, 10:45 AM   #5
Richard Stouffer
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Thanks John, useful information.
Right now I’m sorting through several issues regarding RFI, antenna repair and power supply for the rig. I’m learning a lot and I guess that is what it’s all about. Ignorance is not only bliss; it also keeps me very busy. The downside can be pretty expensive though.
The decision I need to make right now is the rating for the charger for the backup. I don’t want to buy more charger than I need. I don’t expect to be drawing on the battery reserve for more than very brief peaks of a couple of seconds to, at most, a minute and then only 20 amps. I’m hoping that a 10 amp would meet my needs. What’s do you think.
73’s
Richard- WU5K
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Old 06-27-2008, 07:11 AM   #6
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I would go with a 1-2 amp battery tender as the battery charger.. These devices are fairly fantastic and when operating they won't make much difference

But when not operating they will .... Very slowly.... Top off the battery
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Old 06-27-2008, 09:35 AM   #7
Richard Stouffer
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Thanks again John.

See you on the Montana LLC thread at the other place.

73's
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Old 07-11-2008, 08:36 PM   #8
Manual Garcia O'Kely
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Apparently my system does not work then: I've got a bridge rectifier that has two power supplies feeding into it - RS-7 and RS-50, that go into a 100 amp/hour AGM deep cycle battery. The RS-7 is adjusted so that after the voltage drop in the diodes the battery floats at 13.8 volts, the RS-50 is set for 13.8 so only is used when the battery voltage drops a bit and it keeps up the supply when I'm using the transmitter a great deal [on average operation where I'm receiving 99% of the time, I just have the RS-7 on]. This keeps the battery up enough for power failures and transmitting. I leave the RS-50 off most of the time as it's just not needed - 5 amps keeps all the radios warm and the battery topped off.

OK, it's not hi-tech, but my Elmer has been doing this for a long time with no problems. It's also a nice quiet system.

To each their own though.
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Old 07-12-2008, 07:46 AM   #9
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That will work.. However battery life, and in fact is kind of how I've done it in the past

It's not as good as a proper 3-stage charger though.

You would do better to replace your two converters with a single 3-stage such as (Since you are using AGM, a Xantrex XDAC
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Old 07-12-2008, 08:21 AM   #10
Richard Stouffer
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I beginning to think that the three stage charger is going to be a much better approach than the power supply. I've been running the Xantrex three stage charger into a 100 AH AGM battery with very, very good results. I'll put that set-up to a more rigorous test next week when my SteppIR vertical returns from the factory where it was being repaired. but until then, this set-up seems to be working very well driving my 500 watt solid state amp.
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Old 07-13-2008, 06:02 AM   #11
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Oh yes.. Of course my primary sation is a 100 watt Kenwood TS-2000 (Well, sometimes it's only a 20 watt if I'm doing PSK) with computer and a few other goodies hooked up

It runs off 232 amp hours worth of U-220's with a 3-stage charger (Progressive Dynamics PD 9180 w/wizard) Been doing it since 2006 when I got it save for one 24 hour stretch last year (Field Day) I really like that set up.

IN the old days I ran a 2-mtr rig off a floating battery but had a few issues since it was not a 3-stage charger. The battery life was not nearly as good as today.
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