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12 Volt Field Charger Power Source

Old 03-31-2008, 03:21 PM
  #1  
goofeyfoot
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Default 12 Volt Field Charger Power Source

Hello again:

I got three 12 volt batteries sealed lead acid batteries that are between 4000 and 4500 MaHs each. These are the little square batteries that typically power those emergency light boxes you see in offices and public buildings.

I wired all three of the batteries parallel.

I want to use this power source to run a Triton charger in the field.

The Triton charger has a Pb setting on it, so I was also going to use the Triton to charge the power source at home.

My question is what would be a good current to charge the 12 volt power source at? I heard that you can't charge at too high a rate but I don't know how to compute it.

Thanks for your help.

Michael

My
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Old 03-31-2008, 04:42 PM
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Sir Raleigh
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Charging LAB's is a little more complicated than it would appear, so, rather than trying to explain it here, go to the Charging the lead-acid battery site and you'll find all the information you need.
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Old 03-31-2008, 05:06 PM
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goofeyfoot
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Sir Walter:

OK I looked at the article but I really don't know how to apply it to my situation.

The guy in the article quotes some "per cell" voltages.

Well if I have three square batteries is that "three cells" or rather does each square battery contain multiple cells? The batteries just look like one box but maybe there are individual "cells" inside(?)

Thanks for your input.

Michael

PS: Here is a picture of the kind of square battery I'm talking about. [media]http://www.batterywholesale.com/battery-store/battimg/UB1250.jpg[/media]
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Old 03-31-2008, 07:26 PM
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Sir Raleigh
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LAB's come in cells of 2 volts each, so a 12 volt battery will have 6 cells (count the little covers where you put water in your car battery, there'll be 6 of them for a 12 volt battery, or 3 for a 6 volt battery). So, just take the 'per-cell' voltage in the chart and multiply by 6 and you'll get the correct voltage for a 12 volt battery.

As the article starts out, "The charge algorithm for lead-acid batteries is similar to lithium-ion", so you can use the same principle in determining what total voltage to use during charging but use only 10% to 30% of the current the battery is rated for. The only difference is there is no way to balance a LAB like you can Lipos.

Just set your charger for the voltage you want, around 2.4 volts/cell or 14.4 volts total, and the current you want, usually between 0.5 - 1.5 Amps (500 - 1500 mA) in your case, and charge it for about
12-16 hours but not longer than 48 hours

After full charge, remove the battery from the charger. If float charge is needed for operational readiness, lower the charge voltage to about 13.50V (2.25V/cell). The float charge can be applied for an unlimited time.
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Old 03-31-2008, 07:39 PM
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everydayflyer
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Add up total capacity of battreries in parallel.
Example two ea. 4000 mAh (4Ah ) plus one 4400 mAh (4.4Ah) wopuld be 12.4Ah. divide by 10= 1.24A charge rate with Triton set to 12V Pb. 1.2A will be the closest you can set triton.
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Old 03-31-2008, 07:47 PM
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Sir Raleigh
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Thanks everydayflyer, I forgot he had more than one battery...
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Old 04-01-2008, 02:23 AM
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goofeyfoot
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Thanks again guys. I am posting your responses in my garage in a place of honor over the charger.

Sir Raleigh, some nice weather we've been having in Raleigh eh? Three straight days of rain. So much for flying.

Best regards.

Michael
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Old 04-01-2008, 02:28 AM
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Sir Raleigh
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Originally Posted by goofeyfoot View Post
...

Sir Raleigh, some nice weather we've been having in Raleigh eh? Three straight days of rain. So much for flying.

Best regards.

Michael
Yeah, blast it...!!! Looks like it's going to hang around for another week, at least.

Are you in Raleigh?
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Old 04-01-2008, 08:40 PM
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MASTER MARINER
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Default simple power source....Use your car

My car has a power source near the tailgate. I rigged a cigarette lighter plug with the positive enclosed with the open end of the cup holding a strip of copper and the + wire going through the bottom of the plastic cup. The negative is soldered to another strip of copper. Now I just use the alligator clips from my charger (s) and I don't need to take a battery to the flying field.
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Old 04-02-2008, 01:11 AM
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everydayflyer
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I have a power connection right at the rear of my Blazer also. 250Ah worth

http://www.wattflyer.com/forums/atta...0&d=1196023433
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