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Old 04-21-2008, 03:24 PM   #1
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More electrical: House Batteries- Shore Power 12.98 volts ?

Ok so while my systems are separated (the Separator is out) I've had my house batteries on shore power. It's been over 5 days now and they read 12.98/12.97 on the Blue Sky panel while on shore power.

Haven't unplugged, haven't done anything else. Only the CO and propane sensors are on. The Xantrex is running all the time (charging, the invertor is off). I've got it set to powershare at 15a, but of course nothing is plugged in.

My house system is 2 4D AGMs, one is <1 year old and one is original (2005) supposedly tested when the other was installed.

What am I looking for? What/how do I test?
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Old 04-21-2008, 04:16 PM   #2
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I assume you are asking how to test the batteries. The easiest way is to find a auto parts store or place like budget batteries that have a tester. Most of the time these places will test a battery for free.

Otherwise what I would do would be to disconnect the charger and the connection between the two bateries and let them sit for several hours. Then with a multi-meter check the voltage of the two batteries which should be just under 13V. If the battery is under 12 volts you will need to replace it. Then next I would connect one battery to the electrical system and put it under a moderate load. Turn on the fridge. Then test the voltage again. If it drops significantly, more then a couple of tenths, then the battery is dead and will need to be replaced.

I hope this helps.
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Old 04-21-2008, 05:12 PM   #3
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Yes, how, and also if I need to test the batteries. It seems like something is wrong, but I wanted some validation before I go crawling around on the garage floor disconnecting this and that.

I'll be going with the home test as the batteries are neither one easy to reach. If one or both seems bad I'll drag them to Autozone or an RV place to have them re-tested.
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Old 04-21-2008, 06:15 PM   #4
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To answer the question of whether you have a problem you will probably need to look at the literature for the Xantrex inverter/charger. 12.98 volts is about right for the resting voltage of a fully charged lead acid battery. I don't know anything about this type of charger so I can't say what voltage you should be seeing with the charger hooked up and the batteries at full charge. Maybe someone who has one of these will post what voltage they have at full charge.
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Old 04-21-2008, 06:49 PM   #5
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Don't have too much to add to what John and Dana noted, as I have a different charger. That said, here's what my charger does:

If the voltage is low when I plug it in, it charges it to something like 14.3 or 14.4V, and holds it there until the current into the battery hits some low number. Then it holds the batteries at a float of 13.6V.

From my understanding, this is about right for a charger that doesn't have temperature compensation. Perhaps either you have temp compensation and it's adjusting the float voltage, or the float voltage has been set lower manually.

Let's wait and see what others with the same charger model have to say...
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Old 04-21-2008, 11:28 PM   #6
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I found this on the web and thought it might help. At the very least there is tons of good information on batteries and battery care here.

http://www.windsun.com/Batteries/Batter ... 20Charging

Battery Charging

Battery charging takes place in 3 basic stages: Bulk, Absorption, and Float.

Bulk Charge - The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no "correct" voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.

Absorption Charge: The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts.

Float Charge: The 3rd stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging. PWM, or "pulse width modulation" accomplishes the same thing. In PWM, the controller or charger senses tiny voltage drops in the battery and sends very short charging cycles (pulses) to the battery. This may occur several hundred times per minute. It is called "pulse width" because the width of the pulses may vary from a few microseconds to several seconds. Note that for long term float service, such as backup power systems that are seldom discharged, the float voltage should be around 13.02 to 13.20 volts.

Chargers: Most garage and consumer (automotive) type battery chargers are bulk charge only, and have little (if any) voltage regulation. They are fine for a quick boost to low batteries, but not to leave on for long periods. Among the regulated chargers, there are the voltage regulated ones, such as Iota Engineering and Todd, which keep a constant regulated voltage on the batteries. If these are set to the correct voltages for your batteries, they will keep the batteries charged without damage. These are sometimes called "taper charge" - as if that is a selling point. What taper charge really means is that as the battery gets charged up, the voltage goes up, so the amps out of the charger goes down. They charge OK, but a charger rated at 20 amps may only be supplying 5 amps when the batteries are 80% charged. To get around this, Statpower (and maybe others?) have come out with "smart", or multi-stage chargers. These use a variable voltage to keep the charging amps much more constant for faster charging.
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Old 04-23-2008, 04:42 PM   #7
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I have a 2 year old lifeline 4-D that has never been brought down below 11.2v sitting on the floor in my garage. The last time I put a charge to it was about 2 months ago. I just checked the voltage at 12.77 and a cheap % gauge showed it's at 96%. To really test your battery you should break the buss and test each with a carbon pile tester. Good luck
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Old 04-24-2008, 09:18 PM   #8
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Jage for your information, I charged my old AGM 4-D battery up (with a 12A charger) and it took about 5 min to reach full charge. After 20 min with the charger off it read 13.17v (a float charge voltage). After a day w/o any charge it fell back to 12.77v. SMB did say the battery checked OK for a 2 year old AGM battery.
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Old 05-19-2008, 09:11 PM   #9
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Well I was going to take the battery out and had the transmission jack all in place and everything, then I looked over and saw the ground... I decided to take some of my own advice and took it apart- it was a badly layered set of corroded contacts, with the battery negative the most corroded. I cleaned everything and drilled out the copper to reassemble with a really thick grade 8 bolt, torqued it down with the copper against the frame.

I decided to leave the battery in and see how the new ground affects things. I need to get some dielectric grease or something- the ground terminals were mis-sized and that lead to a lot of space for corrosion.
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