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Old 07-01-2017, 06:55 PM   #21
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Did you mount your panels transversely or longitudinally?

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Old 07-01-2017, 11:34 PM   #22
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Did you mount your panels transversely or longitudinally?
I don't think it matters, but I mounted mine longitudinally (I think), mainly because I was limited by the width of the bus(92'ish). And the panels are a 22in wide.

Pic below
[IMG] Here we are, hopefully you can see it
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Old 07-02-2017, 09:23 AM   #23
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I have posted a couple of times trying to generate interest in this idea. No takers yet.

The folks that live in SoCal, AZ & FL have great buys at their fingertips. Those of us "up North" don't have near the deal.

I can buy 2 x 285 watt panels for $208. The shipping is another $160. I can get 10 x 285 watt panels for $1040 and shipping is $260.

So $184 per panel vs $130 per panel. BIG difference.
Sounds like a 'high class problem' because both of those prices are cheap considering them twelve months ago. I will be interested but not in your time frame. If you can afford he batteries 6 or 8 of those panels would put you off grid. With an option to power your house if needed.
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Old 07-02-2017, 09:48 AM   #24
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Sounds like a 'high class problem' because both of those prices are cheap considering them twelve months ago. I will be interested but not in your time frame. If you can afford he batteries 6 or 8 of those panels would put you off grid. With an option to power your house if needed.
I would love to cover the roof with solar but I cannot afford the battery bank to go with them.
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Old 07-02-2017, 03:30 PM   #25
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Thanks, Taolik. My kit should arrive sometime on Friday. The "fun" part now is to purchase 3 new batteries.
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Old 07-02-2017, 05:53 PM   #26
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Just a note if anyone wants to get really technical about solar then visit the cruising sailboat forums. Those guys are really 'off grid' and tend to know what there talking about.
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Old 07-02-2017, 07:22 PM   #27
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I found my 4 T605(More or less same as T105)batteries out of a broken forklift behind a chinese grocery store. They aren't perfect, but they have done me real solid for freebee batteries. If you keep your eyes peeled for the right kinda junk, maybe it'll help you guys get some cheap house batteries. Or clutter a bunch of junk.
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Old 07-02-2017, 07:33 PM   #28
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I need batteries for the bus - all three of mine are DEAD.
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Old 07-04-2017, 05:13 PM   #29
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The solar panels arrive tomorrow!
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Old 07-04-2017, 08:34 PM   #30
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Hmmmm...any idea what killed three batteries?
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Old 07-04-2017, 11:19 PM   #31
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Hmmmm...any idea what killed three batteries?
Pretty much only one thing can do that... Discharge. Anything below 50% on a lead acid battery will damage them. They can also freeze if they are discharged. Lead acid batteries will self discharge over time especially in hot climates. From what I have heard the small 'maintainer' solar panels are quite effective and cheap. Much cheaper than three batteries anyway...
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Old 07-04-2017, 11:22 PM   #32
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if you use AGM batteries, you can run them down close to zero, correct? what I do wonder though is will an AGM battery freeze if its dead?
-Christopher
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Old 07-05-2017, 07:13 AM   #33
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So just looked this up and yes it recommends for AGM less than 50% discharge for longer life but also states “discharging less than 80% will kill the battery’s” Battery Maintenance | Trojan Battery Company . there is another technology (that is too pricy for me) which is LiFePo4 that will go to zero and is very light and somewhat safe compared to lithium. For my money right now I would go Trojan T105 and run them to 50% or deeper (buy less batteries, run them deeper and change them more often) = (buy more batteries discharge less and keep them longer). Either way the prices of the new battery technology is coming down it is just a waiting game till it is within (my) budget. Currently 200ah of 12v LiFePo4 batteries are about 1500usd but its dropping… LiFePO4 Prismatic Battery: 12.8V 100Ah (1.28 KWh, 10C Rate) - UN38.3 Passed (3.2Vx4 DGR)
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Old 07-05-2017, 07:29 AM   #34
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how on a lead acid or an AGM do you accurately determine the state of charge? is it applying a certain percentage of the battery rated load and reading the voltage? or is it related to standing voltage?

for instance when my inverter shuts down due to low battery voltage, my batteries are at ??? percent state of charge.. obviouslt many factors involved.. such as voltagew drop in wires from bats to inverter, the accuracy of the inverter's shut down protection circuitry etc.. but id like to somehow get an idea that my inverter shut down and my batteries were at some state...

-Christopher
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Old 07-05-2017, 07:41 AM   #35
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The very short answer is: measure all the electrons going into and out of the battery bank. The Trimetric (Bogart Engineering) and Victron BMV-700 are examples of this. Both require a large shunt on the negative cable so the flow of electrons can be monitored. I'm not smart enough to attempt to explain all the logic that is applied but once you get them setup, they are pretty accurate.

Voltage of an at-rest battery (meaning no power going in or out for the last 24 hours or so) is reasonably accurate. Sadly, our batteries are never at rest so voltage is a very poor indicator of SOC (state of charge). Specific gravity is accurate (as far as I am aware) but that requires a lot more work than most of us want first thing in the morning when deciding whether or not there is sufficient power to brew a pot of coffee.

Lithium is probably out of scope for this thread but I can report that I am very pleased with my bank. While I do not have an unlimited supply of power, I am amazed at what I do have available given the incredibly small size/weight. However; it is fairly complex and requires much more than just dropping a few cells in and hooking up the cables.
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Old 07-05-2017, 08:50 AM   #36
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Quote:
Originally Posted by cadillackid View Post
how on a lead acid or an AGM do you accurately determine the state of charge? is it applying a certain percentage of the battery rated load and reading the voltage? or is it related to standing voltage?

for instance when my inverter shuts down due to low battery voltage, my batteries are at ??? percent state of charge.. obviouslt many factors involved.. such as voltagew drop in wires from bats to inverter, the accuracy of the inverter's shut down protection circuitry etc.. but id like to somehow get an idea that my inverter shut down and my batteries were at some state...

-Christopher
One other factor to consider when having a significant voltage drop under load is the battery's chemical process. Deep cycle batteries can provide long, sustained draw, but aren't good at fast discharges. They have fewer and thicker plates than, say, a starter battery so have less surface area. That reduction in surface area against the acid means they can't provide the high amperage that starter batteries can.
If you try to run a high-draw device off of an inverter plugged into an undersized battery bank then you'll see the voltage drop rapidly. Then if the battery sits for a minute the voltage will go up again.

State of charge is difficult to determine. If the battery in question has been idle for a couple hours then you can reliably check the voltage to get SoC. Otherwise you'll need to measure amps-in and amps-out (as previously mentioned) to know where you stand. This method will lose accuracy over time as the battery ages. The most reliable method is to check the electrolyte (on flooded lead acid batteries), but that's a bit messy I only do that a couple times a year to check on the battery health.
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Old 07-05-2017, 04:13 PM   #37
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Actually looking at this battery and given that its 12v and it can be discharged to almost 100% the prices are starting to look reasonable. Also if space and weight are an issue then even more so. I tend not to be an early adopter so if one of you guys could just go ahead and drop a few grand on a few hundred Ah worth of these that would be great (office space). Then report back I think we would all be very grateful… also would like to point out that I generally know just enough to be dangerous…

LiFePO4 Prismatic Battery: 12.8V 100Ah (1.28 KWh, 10C Rate) - UN38.3 Passed (3.2Vx4 DGR)

this is $615 and four T105 would be almost getting there. I have no idea on the quality of the product.
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Old 07-05-2017, 04:14 PM   #38
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and another one...

LiFePO4 Prismatic Battery: 12.8V 200Ah (2560Wh, 10C Rate) - UN38.3 Passed (3.2Vx4 DGR)

but you would be better off with 2 x 100Ah... $615 v $1470...
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Old 07-05-2017, 04:22 PM   #39
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so if one of you guys could just go ahead and drop a few grand on a few hundred Ah worth of these that would be great (office space). Then report back I think we would all be very grateful…
Already did it - see the link in my signature.
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Old 07-05-2017, 06:20 PM   #40
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Already did it - see the link in my signature.
That's awesome only read the battery part so far but it sounds kind of like what I want to do. But my rig will start of yellow. So streight to the point, how much has the price dropped since you purchased? I'm also happy to see you seem to have the same brand I was looking at.

I posted earlier about storing enough solar power to heat at night and it became unpractical. How do you manage...?
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