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Author Topic: Battery Questions  (Read 12264 times)
KB3THX
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Posts: 12




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« on: March 05, 2012, 12:09:03 PM »

I have two large (~ 100 Ahr), deep cycle batteries, one of which I am currently using for backup power for my base station (IC-7000).  My current setup uses a Super PWRgate PG40S to connect the battery, my 12V plug-in power source and the radio.  I have a couple of questions.

First, has anyone used this unit with parallel batteries?  It is my understanding that my operating time will more than double by using 2 batteries in parallel, but not sure whether they can be charged as a single unit (e.g. what if charging requirements were out of synch)?

While I am working on the calculations for operating time based on advice throughout this forum, I'd still like a way to monitor real-time battery operating life.  Would something like this battery bug be appropriate?

http://www.powerwerx.com/digital-meters/argus-BB-DCM12-150-battery-bug-deep-cycle-battery-monitor.html

Other suggestions for monitoring battery status welcomed ;-)

Thanks!

Scott KB3THX
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W8JX
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Posts: 5755




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« Reply #1 on: March 05, 2012, 01:15:16 PM »

It is my understanding that my operating time will more than double by using 2 batteries in parallel, but not sure whether they can be charged as a single unit (e.g. what if charging requirements were out of synch)?

The reason you will get more than twice the run time is because batteries become more efficient under a lighter load. So if you have say a 20 amp load you will recover more power from both batteries in parallel with each seeing a 10 amp load than running each battery down separately under a 20 amp load. A 100 amp hr battery is usually rated at a 20 hr discharge rate.  This works out to a 5 amp load. If you increase this to 10 amps you will get a bit less and at 20 amps even less yet.

As far as charging I would not worry one bit about it. They have been doing it for many many years on diesel P/U's farm equipment, construction equipment etc. I have been running dual batteries in SUV's/ P/U's for over 20 years and only problem I even had in all that time was once a cell when bad in one battery and discharge the good battery too over time to 10.5 volts. Bought a new battery to replace one with bad cell and was back in business.
« Last Edit: March 05, 2012, 04:32:17 PM by W8JX » Logged

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K5LXP
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« Reply #2 on: March 05, 2012, 04:37:42 PM »

Similar thread, similar responses.

http://www.eham.net/ehamforum/smf/index.php?topic=72368.0

Mark K5LXP
Albuquerque, NM
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KB3THX
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Posts: 12




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« Reply #3 on: March 05, 2012, 05:13:38 PM »

Yes - I read that thread before posting, but still was unsure regarding methods of monitoring battery life.  The cheapo digi- voltage meters did not seem to be the best solution...

Thanks,

Scott KB3THX

Similar thread, similar responses.

http://www.eham.net/ehamforum/smf/index.php?topic=72368.0

Mark K5LXP
Albuquerque, NM
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W8JX
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Posts: 5755




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« Reply #4 on: March 05, 2012, 05:23:12 PM »

Yes - I read that thread before posting, but still was unsure regarding methods of monitoring battery life.  The cheapo digi- voltage meters did not seem to be the best solution...

What are you looking for here? Battery life ie charge status or battery life expectancy?
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KB3THX
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« Reply #5 on: March 05, 2012, 05:26:06 PM »

Sorry to be unclear.  I want to know when I am approaching minimum operating voltage for my radio, as well as charge status when recharging.

Thanks,

Scott

Yes - I read that thread before posting, but still was unsure regarding methods of monitoring battery life.  The cheapo digi- voltage meters did not seem to be the best solution...

What are you looking for here? Battery life ie charge status or battery life expectancy?
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W8JX
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Posts: 5755




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« Reply #6 on: March 05, 2012, 05:46:06 PM »

Minimum voltage kinda depends on radio but most should operate down to 11 volts with a possible loss of some output. I have used a few Kenwood TS-140 mobile/portable for 20 years and they make full power down to 12 volts and still do a good job on 11 volts. I suggest you do some tests as you run it down and monitor radio performance. You will not hurt it. I do recommend that you recharge at 11.0 volts though for longer battery charge cycle life.
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KB3THX
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Posts: 12




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« Reply #7 on: March 05, 2012, 06:11:18 PM »

Got it - thanks.  But I'm still not sure how to monitor the current voltage - that's why I was thinking about buying the "battery bug" I referenced in my first post (or something similar).

73,

Scott - KB3THX

Minimum voltage kinda depends on radio but most should operate down to 11 volts with a possible loss of some output. I have used a few Kenwood TS-140 mobile/portable for 20 years and they make full power down to 12 volts and still do a good job on 11 volts. I suggest you do some tests as you run it down and monitor radio performance. You will not hurt it. I do recommend that you recharge at 11.0 volts though for longer battery charge cycle life.
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W8JX
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« Reply #8 on: March 05, 2012, 07:59:40 PM »

How about something like this

Click Here
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K5LXP
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« Reply #9 on: March 06, 2012, 05:59:07 AM »

Got it - thanks.  But I'm still not sure how to monitor the current voltage

If all you want to know is the exact voltage at any given instant, a digital or analog meter will work just fine.  There are digital meters that will draw their power from the monitored point, so you don't have to deal with batteries or a separate supply.  Of course, analog meters will do the same.  Then it's up to you to interpret what the value means at that moment. 

I use gel cells a lot for portable operating and find a large analog expanded scale voltmeter tells me everything I need to know at a glance.  This is something you can make out of just about any meter movement.  It's terminated in a powerpole so all I have to do is plug it in anywhere in the supply line.  For extra credit you can use a dual meter as mentioned in the linked thread which will tell you SOC and power as well.


Mark K5LXP
Albuquerque, NM
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KC2MMI
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Posts: 620




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« Reply #10 on: March 13, 2012, 04:18:39 PM »

Scott-
 Lead acid batteries of all types are sensitive to how deeply you cycle them. The exact numbers vary an awful lot from one maker to another, but it your batteries are rated for, 500 cycles at 50% discharge cycle, they may also berated for 1000 cycles at 30%, or 100 cycles ar 80%.

 So you get more "power" in terms of watts stored and reclaimed over the life of the battery, when you don't discharge it as deeply. If you have two batteries and you discharge each of them to 50% before recharging, you could instead have the two batteries in parallel and only discharge them to 25%, using the same amount of power before a recharge, but cycling the batteries only half as much and probably doubling the life you woudl get from them.

 So paralleling the batteries into one battery bank has some real benefits to your wallet.

If you do so, ideally the batteries would be identical from the same lot. (Or, two 6v batteries or 6 2-volt cells, combined in one bank.) In reality as long as the batteries are 'close', same type, similar condition, you'll usually be OK. You might want to keep an eye on them, check the electrolyte in wet cells, use a voltmeter to test in sealed batteries, to confirm that they are actually doing OK together.


 Or, simply switch batteries more often, i.e. so you don't discharge either one very much. Swap well before you have to. A proper charge regimen, with float charging and equalization (for wet cells) will make a huge difference as well.
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KK4GMU
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« Reply #11 on: March 22, 2012, 10:15:01 PM »

I just got a 12 volt outlet attached to my 48 volt golf cart battery system via a 48 to 12 volt  voltage reducer.  The reducer is 20 amp continuous.

The 48 volts is provided by 6, 8 volt  deep cycle Trojan batteries.  I'm guessing I could get some considerable run time on my 5 watt HT with this setup.

And somewhat less run time if I need to get out with the 50 watts of my mobile unit, but not sure how long.

 Any observations?
« Last Edit: March 22, 2012, 10:18:33 PM by KK4GMU » Logged
W8JX
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Posts: 5755




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« Reply #12 on: March 23, 2012, 02:48:48 AM »

I just got a 12 volt outlet attached to my 48 volt golf cart battery system via a 48 to 12 volt  voltage reducer.  The reducer is 20 amp continuous.

The 48 volts is provided by 6, 8 volt  deep cycle Trojan batteries.  I'm guessing I could get some considerable run time on my 5 watt HT with this setup.

And somewhat less run time if I need to get out with the 50 watts of my mobile unit, but not sure how long.

 Any observations?

How much run time a 50 watt mobile would have would really depend more on how much you drive cart than run rig. Your batteries store around 12 KW hrs or so which should give you about 5 days of continuous key down time on a 50 watts mobile if you do not drive cart. On receive only about 6 or 7 weeks give or take. Yes these numbers are kinda extreme but then so is the size of your battery pack.
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KA1MDA
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« Reply #13 on: April 09, 2012, 12:47:31 PM »

If you're interested in monitoring battery capacity, a volt meter is virtually useless. You need to cumulatively measure actual charge/discharge current through a shunt.

A device from Bogart Engineering called the Trimetric does exactly that, and can be found at the following link:
http://www.bogartengineering.com/products/TriMetric

I've been usng a Trimetric TM-2020 for years to monitor the charge status of my emergency power backup system, and have found it to be extrmely accurate and useful. Link to my emergency power system is below:
http://www.ka1mda.org/ham/homebrew/ups/index.htm

Tom, KA1MDA
www.ka1mda.org
« Last Edit: April 09, 2012, 08:32:07 PM by KA1MDA » Logged
KC2MMI
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Posts: 620




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« Reply #14 on: April 12, 2012, 03:48:21 PM »

The Victron BMS is one of the least expensive ones that can display both voltage AND accumulated wattage in/out of the battery bank.

http://shop.pkys.com/victronenergybmv600precisionbatterymonitor.aspx?gclid=CK-Qwa2wsK8CFREr7AodV2MXGQ

If you really want to measure capacity, that's the way to go.

However, most battery manufacturers these days will tell you that a simple digital voltmeter is good enough IF you use it intelligently. This means an accurate calibrated meter, typically 1/2% or better accuracy and known to be in calibration, since tenths of a volt count.

A fully charged battery depending on chemistry will show 12.6-12.7 volts after resting overnight from a full charge. There are short-term distortions in the measured voltage immediately after charging and during heavy discharging, but a "resting" battery or one that has been in light use CAN be accurately measured with just an accurate voltmeter. Every 1/10th of a volt that it goes down from 12.6-12.7 accurately rerpesents 1/10th of the useful charge capacity.

Since most deep cycle batteries get their best life when cycled only 30% or so, that means you want to recharge the battery when it shows 12.3 volts during rest or light use. Not my opinion, you cna confirm that with any battery maker.
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