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hallamore
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# Posted: 5 Nov 2010 09:57pm
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For those of you who understand this better than me, can you explain why my batteries during the day will read upto 13.7 v but at night time it reads 13.1. Tonight when I came back in from hunting, I haven't had my solar system on all day (inverter is even turned off). I have a C-35 Xantrax charge controller so I know I am not 'bleeding' power back out to the array but I don't understand when I am not using the solar system in the day today it read 13.7 as it was charging and tonight (system off all day) it read 13.1. Why the loss of power? Should it have read tonight also 13.7?
Thanks for your help
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MikeOnBike
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# Posted: 5 Nov 2010 10:28pm
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I think what you are seeing is a charging voltage of 13.7v during the day when your solar panels are charging your batteries. At night the 13.1v reflects the actual battery voltage.
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MtnDon
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# Posted: 5 Nov 2010 10:59pm
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What Mike says is correct.
When the system was indicating 13.7 volts do you know what state the charger was in; bulk or float charge? 13.7 may be low for bulk rate but a tad high for float.
In order for a 12 volt wet cell battery to charge it must have at least 13.8 volts input. Trojan battery recommends 14.8 for their 12 volt batteries on bulk charge and 13.2 for float. The higher voltage will charge more quickly and more fully.
But more on those numbers. What type of battery, flooded lead acid like a golf cart battery or an AGM or? Battery type influences recommended charge rates. Also what was the battery temperature? Batteries are rated at 77 F. As the temperature falls their capacity also falls, as will voltages. Do you have a battery temperature sensor with that C35?
In any event once the batteries have been at rest for 3 or more hours (no charge or discharge at all) a fully charged battery should be at approx. 12.7 volts.
Voltage readings are only an approximate gauge. Hydrometer readings with an adjustment for temperature is the best and most accurate method. Hydrometer readings also permit comparing cell to cell reading which can offer insight to battery health.
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hallamore
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# Posted: 5 Nov 2010 11:33pm
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MtnDon, You are always helpful. What I didn't know until I read up about you is that you live in the Jemez Mountains. I used to have a cabin in Area 3 just north of downtown Jemez Springs. That is the most beautiful place in the world. As for your questions, The C35 is in bulk until 14.4v. The battery bank consists of 8 225 AH golf cart batteries wired in series and parallel. I just purchased the C35 and hooked it up last week and yes we purchased the battery temp gague. I have a very small array that consists right now of 7 15 watt panels that put out about 60 watts. Tomorrow I am adding a Sharp 123 Watt panel wired in parallel to give me additional power input from the array. Oh yeah, the battery bank is in my garage in my cabin....getting back to Jemez Springs; we sold our place there and moved to wonderful Iowa and now buillt an off grid place up here...take a look - www.timberhilloutfitters.com
Thanks again.
Hallamore
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MtnDon
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# Posted: 6 Nov 2010 12:17am
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You are right. The Jemez is a very wonderful place, hard to compare or beat. We are further along towards Los Alamos, directly south of Redondo Peak 5 or 6 miles.
Because you have the temp sensor you could safely boost the bulk voltage a little, like the 14.8 Trojan specs. If the battery gets too warm the unit will taper down the charging.
I run our 24 volt system up to 29.8 volts in bulk/absorb and 27.6 on float with golf cart type batteries.
Do you have a large deer population. We get both deer and elk crisscrossing our property most of the year.
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hallamore
Member
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# Posted: 6 Nov 2010 12:29am
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I really miss the hot springs! The valla Caldera is so beautiful. Yeah, we have a huge deer population here in southern iowa. Iowa is the center of the whitetail deer hunting world. All the corn and soy makes them grow huge up here. But to me nothing beats elk hunting. I shot a huge bull up near San Gergario Resivour just east of Cuba New Mexico 6 years ago. I will be back and live in the Jemez mountains some day.
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