battery storage temp and question on monitoring discharge

Started by AdironDoc, December 05, 2010, 08:02:20 PM

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AdironDoc

I just bought 6 inexpensive Energizer GC6 batteries at Sams and was wondering how best to care for them until they are used. They will be put in use at the camp 10wks from now. Should they be brought inside and stored at room temp? Shall I begin to add a load and  cycle them or is it ok to leave them fully charged for the next 10wks?

I'm planning a depth of discharge to around 30%. I know voltage meters are an inaccurate way of measuring remaining charge. Amp/hour meters are good, but how can they be used while my wind and/or are charging the array while I'm using them? Is there an optimal way to know how much battery has been used?

Lastly, what size cables should connect the batteries in the array? Do they make precut lengths with the clamps ready?

Doc


MountainDon

Make sure the batteries are fully charged and let them sit. That's all. They will not freeze when fully charged, at least not at any temps you are going to experience. They self discharge a little so a light float charge would halp that, but so will giving them a slow boost from an auto battery charger every 3 - 4 weeks.

Voltage is not too bad a guide when the batteries are sitting with no active charge or discharge. It gets difficult to use voltage as a guide when power is going in and out within 3 - 4 hours of taking a reading.  Specific gravity with a real float type hydrometer is always best. That allows checking of individual cells which the voltage does not do. But they are new so likely no bother right now.

With the Outback FM60 and the Mate remote I can monitor the daily charge that goes into the batteries, max and min voltages, etc. I used to look at that several times a day. Now I have a quick peek once in a while, like maybe in the morning and that's it.

Just because something has been done and has not failed, doesn't mean it is good design.


MountainDon

cables to array.

Most PV modules use either MC3 or MC4 connectors for the power connection. There will be a male and a female, one positive and the other negative. The panels may be connected serially. To parallel connect PV modules a combiner box is required, or make something if you can. What one does may depend on whether or not there will be an electrical inspection/inspector.

MC4 are the current NEC code compliant type, MC3 are older. MC4 have locking tabs and MC3 do not.  Cords are available in assorted lengths with a female on one end and a male on the other.



I believe most of these pre made cords come in 10 gauge. Whether or not 10 gauge is sufficient will depend on the distance from panel to combiner and/or charge controller and how much maximum amperage will be carried.

Parts and tools for making your own cords are also available. High temperature rating wire is required, as well as being UV resistant.

http://www.affordable-solar.com/mc4-cable-8-10.awg.htm#
Just because something has been done and has not failed, doesn't mean it is good design.

AdironDoc

Quote from: MountainDon on December 06, 2010, 02:52:02 PM
cables to array.

Most PV modules use either MC3 or MC4 connectors for the power connection. There will be a male and a female, one positive and the other negative. The panels may be connected serially. To parallel connect PV modules a combiner box is required, or make something if you can. What one does may depend on whether or not there will be an electrical inspection/inspector.

MC4 are the current NEC code compliant type, MC3 are older. MC4 have locking tabs and MC3 do not.  Cords are available in assorted lengths with a female on one end and a male on the other.



Thanks, Don. You're just a little ahead of me as I haven't bought my panels yet. This will come in handy later, however. I was actually wondering about the fat cables that jump between battery terminals in an array. I've got some new batts, (6 and counting), and will make a 12V array. What does one use battery to battery?

I believe most of these pre made cords come in 10 gauge. Whether or not 10 gauge is sufficient will depend on the distance from panel to combiner and/or charge controller and how much maximum amperage will be carried.

Parts and tools for making your own cords are also available. High temperature rating wire is required, as well as being UV resistant.

http://www.affordable-solar.com/mc4-cable-8-10.awg.htm#


MountainDon

Ah! When I see "array", I think PV. When I see "bunch of batteries" I think of a battery bank, not an array.  d*

Cable size depends on maximum charge or discharge.  You can't go wrong with getting bigger than you need.

That said, 2/0 cable is frequently used for battery interconnect cable.  

You can make your own; AZ Wind-Sun has reasonable prices on welding cable and solarseller.com a good selection of cable ends. . Note welding cable and auto battery cable is not NEC approved.

Or use bar copper. Storm Copper has ampacity charts and an online store.



That's 2/0 cable.
Just because something has been done and has not failed, doesn't mean it is good design.


AdironDoc

Forgive a newbie. An array to me is any group of like objects arranged in a nifty pattern. :D

Love the copper bars. Awesome! thanks for the links, Don  [cool]

MountainDon

I should have noted, that is just me more than likely. Sometimes I don't look/read deep/carefully enough.


Since I took that photo I have also sprayed the terminal connections with a red lacquer sealant or corrosion inhibitor.
Just because something has been done and has not failed, doesn't mean it is good design.

firefox

Bruce & Robbie
MVPA 23824

MountainDon

#8
Quote from: firefox on December 07, 2010, 03:51:59 AM
Any idea why welding cable is not approved?
Bruce

Most likely only because most of the brands been not submitted for testing, and the money that costs not paid. It's the manufacturer, or whoever wants to sell something, that has to submit and pay for an item to be tested by an approved UL testing lab. So we have no real idea if that welding cable insulation could qualify. There is at least one approved brand; I saw a listing for fine stranded approved cable someplace once. Very pricey compared to the run of the mill stuff.

Normal crimp connectors used with fine strand wire like welding cable can fail under some conditions so there are special crimp connectors made for welding cable.

Same for auto battery cables. They already have a large market with the auto industry. Why spend money for an approval for what would be a very small sales amount relatively speaking?

Just because something has been done and has not failed, doesn't mean it is good design.


MountainDon

I used welding cable but there was no inspection. But then a guy we know with an off grid system near our cabin also used welding cable and he passed inspection. Inspectors do have some discretion if they want to use it.
Just because something has been done and has not failed, doesn't mean it is good design.

AdironDoc

I liked your wiring when I saw it Don. After reading this interesting piece on different ways to wire and which is best, I liked it even more.

http://www.smartgauge.co.uk/batt_con.html

MountainDon

 :D

I also theorize that if the connecting cables or straps are very much over-sized for the typical current flow then unequal lengths become less and less important, even irrelevant.
Just because something has been done and has not failed, doesn't mean it is good design.

firefox

Thanks Don! That makes sense to me, re certification.
I have always used welding cable with anything to do with batteries
and high ampacities. But then I always tend to over engineer things and go with thicker cable. Of course it costs more, but in this case that may not be true.

I came across this while looking for something:
www.usbr.gov/power/data/fist/fist3_3/vol3-3.pdf

It is a relatively short note and is in mostly laymans terms.
The devil is in the details, and it covers the details of making good
connections. Don't skim though, there are some subtle differences.
This was intended for the bigger switching stations, but the info
applies down to the small stuff as well.
Bruce
Bruce & Robbie
MVPA 23824