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Author Topic: using multiple batteries  (Read 1883 times)
K4IDK
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« on: July 09, 2017, 12:25:57 PM »

I'm using a PWRGate and Rig Runner on my station.  I have 3 AGM batteries, all the same make, capacity and the same age.  I've been keeping them all charged by switching them around, plugging in one for awhile then another and on and on.

Will they charge just fine if I connect them all 3 in parallel?  It would be less hassle than plugging and unplugging every day or two 
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KC4ZGP
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« Reply #1 on: July 09, 2017, 01:48:31 PM »


Sure why not. They'll just take longer to each get a full charge.

Kraus
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W8JX
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« Reply #2 on: July 09, 2017, 07:11:54 PM »

When you parallel them hook positive feed to positive terminal on a battery on one end or string/buss tie and the negative lead to a battery on other end of string. Hooked up this way they will all see same discharge and charge potential.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
K5LXP
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« Reply #3 on: July 10, 2017, 07:22:35 PM »

Here's an image of what 'JX is referring to:

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KC8HXO
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« Reply #4 on: August 10, 2017, 05:14:35 PM »

As they age, one will naturally begin to  have a higher internal resistance, and it will become the weak link in the chain......less able to take a charge from the same input charging voltage, and less able to give back potential when needed. That being said, it may take years to notice one is weaker than the rest. Your current system enables you to "keep an eye" on performance individually.  Be sure to note the "resting" (Overnite, with no load, and no charge) voltage of your bank. Keep a log of it. Do it once a month or so. A change in that resting voltage is a quick trigger that you have an upcoming issue. (Assuming battery temperature will always be about the same). I used to use one of the little digital volt meters that uses only 2 wires from Adafruit. Left it on all the time.
I would parallel them, but monitor them if you do.

Regards,
Greg, KC8HXO
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W6EM
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« Reply #5 on: August 25, 2017, 01:27:09 PM »

As they age, one will naturally begin to  have a higher internal resistance, and it will become the weak link in the chain......less able to take a charge from the same input charging voltage, and less able to give back potential when needed. That being said, it may take years to notice one is weaker than the rest. Your current system enables you to "keep an eye" on performance individually.  Be sure to note the "resting" (Overnite, with no load, and no charge) voltage of your bank. Keep a log of it. Do it once a month or so. A change in that resting voltage is a quick trigger that you have an upcoming issue. (Assuming battery temperature will always be about the same). I used to use one of the little digital volt meters that uses only 2 wires from Adafruit. Left it on all the time.
I would parallel them, but monitor them if you do.

Regards,
Greg, KC8HXO
Paralleling lead acid batteries can lead to problems if they are not "equalized" periodically.  Your diode-isolated power gate, or even the "low loss" one with an internal UC3906 controller won't do that at the 14V to 14.4V DC input to the Power Gate from your power supply.  There isn't a lot of drop in the "low loss" version, since it uses MOSFET switches and not diodes.

The battery cells need to have about 2.5V each or 15V overall applied periodically so as to equalize the cell specific gravities.  The process is really an overcharge.  And, it is done to remove sulfation from the lead plates.  You can do, but need to remove the batteries from your power gate and equipment due to the higher than desirable voltage needed to do it.

If you don't do this, individual cells will vary in terms of internal resistance and lead to premature loss of capacity.

Automotive systems sort of do that with the initial 14.5V or so applied to batteries right after start up.  But, of course, Power Gate never does that.  It just applies what amounts to float voltage, or slightly higher as you don't want to apply too much voltage to your equipment from normal DC power supply power.

You also need to check electrolyte levels and add water if needed if the cells are vented.

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W6EM
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« Reply #6 on: August 26, 2017, 07:26:34 AM »

One or two more cautionary comments.  Be careful with sealed lead acid batteries regarding equalizing charge.  Excessive gassing can pop the vents and in doing so, lose electrolyte....and have no way to add more water to replace what might be lost.  One of the problems with SLA batteries.  Best to use a precisely-controlled charger based on something like the UC3906, which will limit the time that an overcharge is applied automatically.

And, if you do need to add water in a vented cell battery, it should be distilled so as to not add any salts to the electrolyte.

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