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Small Cabin Forum / Off-Grid Living / Starting battery test
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groingo
Member
# Posted: 21 May 2014 13:02 - Edited by: groingo
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Put new Crown 235 (yes Crown not Trojan....long story) ...voltage showed 13.42 so let set overnight and they were 12.76...I figure there may be a shakedown of a few days before readings stabilize I hope.

Also replaced my new but never used Harbor Freight 200 watt inverter which went bonkers with only a 15 watt load the lights kept flashing off and on, and when they decide to stay on all my lights were humming (never done before) and my internt phone would simply not work but when I picked up the reciever it had heavy static....so I got a Schumacher 400 watter digital and it works as it should with one nice bonus, at the low wattage I am using the fan stays off, use over 100 watts and it turns on....so far so good.
Will be taking battery measurements three times a day, hoping for the best.

creeky
Member
# Posted: 21 May 2014 16:54
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crown rules. led lights like a good pure sine waveform.

groingo
Member
# Posted: 21 May 2014 19:40 - Edited by: groingo
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How high do you charge your batteries and how low do you let the voltage go till you recharge?

MtnDon
Member
# Posted: 21 May 2014 23:30
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IIRC, I have the CC set to go into absorb once the voltage hits 29.6 (14.8 in terms of a 12 VDC system). All charging is via the Outback FM60 except for the rare multi day cloudy spell when the generator will be fired up, or if I elect to run the generator just because it hasn't run in a month or so.

We seldom go below 24.6 (12.3 in a 12 VDC system).

groingo
Member
# Posted: 22 May 2014 09:31
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Don, again you nailed it, between 12.3 and 12.6 is where I put my minimum which is at 50% discharge which is what the battery maker recomends for best life and performance.....confirmation of this from real world users like yourself makes my task that much easier.

MtnDon
Member
# Posted: 22 May 2014 10:53
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...12.3 and 12.6 is where I put my minimum which is at 50% ...


??? At 12.3 volts it's more like 30% discharge or 70% charged, according to common charts and tables such as
http://www.solar-electric.com/deep-cycle-battery-faq.html

http://www.chargingchargers.com/tutorials/charging.html

groingo
Member
# Posted: 22 May 2014 11:58
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Gotcha, we were both going to the same site (solar electric) 50% was 12.06 and 70% was 12.32 so technically we're both on the same page...this is good.

creeky
Member
# Posted: 22 May 2014 16:43
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12.7 is full charge for a 12v system.

I let my Morningstar decide what voltage to charge at. After putting in or "programming" the baseline Crown recommended charging values. The number is temp sensitive. I'm down to 14.9 on my absorb charge. I imagine mtndon is a little warmer than me.

Batteries are so weird tho. If you have a load on your batteries that will push the voltage down, but it won't reflect the actual state of charge. Run the microwave at fully charged and you'll see 12.4. Or even less. Wait two hours for your batteries to come back and you might see 12.67. So basically all but fully charged.

In the winter in the morning after running the kettle, coffee grinder, blender etc I might see 12. But I'm not 50% discharged. It's just the heavy 700 to 1500 watt loads driving the batteries down. And is it my imagination or are colder batteries a bit more sensitive to loads?

Of course summer it's the hazy lazy days. Even under load the battery minimums i'm seeing are 12.3. This morning my batteries were at 13.1 with 80 watts coming from the panels... that was with the Internet and lights and fridge. I was 13.4 even after running the smoothie maker. That's cloudy skies too. Gosh I luv summer.

I need some help, what other gizmos can I use for my summer solar system stress test.

MtnDon
Member
# Posted: 22 May 2014 19:40
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Anytime there is enough sun to make power from any PV panels in the connected system voltage values are pretty much meaningless as the CC must be putting out more voltage than what the batteries basic level is. Which is why I pay only cursory attention the the voltage. Voltage indicates whether or not the system is functioning more or less as it should be when the sun shines. If I really want to know some truths I use the hydrometer. Sometime this summer I will get the Flexnet DC hooked in and then I'll have some numbers that will be more meaningful.

groingo
Member
# Posted: 22 May 2014 22:16 - Edited by: groingo
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Found out lots of good info today, charged battery for seven hours to verify load on generator and it came in right on target keeping just under the 25% level for the generator which gives optimum fuel use, 7 hours and it used 3/4 of a quart, had two hours fuel left.

Started charging battery with 12.55 morning, checked at noon was 13.44 and at 4:30 charger showed full battery read 13.47 which after an hour dropped to
12.57 but according to Crown this is at 98% charge so it looks nornal and will also allow me to knock even more off charge times in future.

Batteries, definitely not a precise science to be sure.

First this tells me the charger reduced output and second it told me I may be able to reduce run time by up to 4.5 hours, will see in a few days.

Of course any results have to be done on a curve so I am going to figure 25%
below what it actually comes out till I get more information and spot any patterns but at this point it is looking good.

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