Temperature limits

[Tiny Metal Tube]

Well, it's finally time to start planning my electrical system in more detail than just watts and amp hours.

Are there any temperature limits on deep cycle batteries, solar panels, or any related electrical system stuff?  I see vans in the deep cold and in the blazing heat and want to be sure.  

I also know batteries will have trouble holding a charge when it gets cold... But is it safe when they're in -20F winters and 120F summers?   (Assume I'll have sealed AGM batteries)

Of course I'll have heat and ventilation, but I won't always be in the van.

Thanks.

 

[John61CT]

For lead, poor performance in the deep cold is dealt with by grossly oversizing AH capacity compared to what you'd need in only-warm conditions.

Heat is bad for longevity, but other than keeping away from engines and other active sources, we live with it.

Temperature compensation for voltage is a Good Thing.

 

[tx2sturgis]

I also know batteries will have trouble holding a charge when it gets cold... But is it safe when they're in -20F winters and 120F summers?   (Assume I'll have sealed AGM batteries)

Batteries tend to self-discharge more when it's hot then than when it's cold. They don't have trouble holding a charge when it's cold, but they are less able to deliver higher levels of current as it gets cold....remember, it's a chemical reaction taking place in the battery.

So yes, if the batteries are exposed to -20f then you can expect a drop in the ability to deliver, and accept, lots of amps.

 

[Trebor English]

You don't say what batteries you are going to use.  The trojanbattery.com data sheet for the T105 golf cart battery says operating temperature range is:  

-4°F to 113°F (-20°C to +45°C). At temperatures below 32°F (0°C) maintain a state of charge greater than 60%.  

Since the -20 to +120 range you want to accomodate is beyond the range of the standard, the real Trojan T105, make sure that whatever battery you buy has a temperature range that meets your requirement.  Look through all the specifications for small print saying not to charge at over 45 degrees C or something like that.  Beyond the upper limit of temperature don't expect many happy years of service.  Heat kills batteries.

 

[Tiny Metal Tube]

I haven't decided yet, but I've been looking at the Odyssey PC1800-FT.  Saw someone mention it on YouTube and it seems like a pretty solid battery.  A couple of these and I should be good to go through a few days of bad weather.

https://www.amazon.com/dp/B00M1X3BSW

I didn't know the different batteries had different tolerances; but -4 to 113 seems like a decent starting point. Obviously I'll try to keep the batteries around 60-70 whenever possible, since that's where I like to be too.  

I don't mind replacing these after 5-10 years (though if it's sooner I might go with something cheaper!).  Any other major considerations with temperature?

 

[frater secessus]

Panels like it cold. They are rated at about 0 degrees ambient; higher temps than that causes cell temp to rise and Vmp to fall (all else being equal).
Calculator: http://digivation.com.au/solar/tempderate.php

 

[John61CT]

I haven't decided yet, but I've been looking at the Odyssey PC1800-FT.  Saw someone mention it on YouTube and it seems like a pretty solid battery.  A couple of these and I should be good to go through a few days of bad weather.

https://www.amazon.com/dp/B00M1X3BSW

I didn't know the different batteries had different tolerances; but -4 to 113 seems like a decent starting point. Obviously I'll try to keep the batteries around 60-70 whenever possible, since that's where I like to be too.  

I don't mind replacing these after 5-10 years (though if it's sooner I might go with something cheaper!).  Any other major considerations with temperature?

Odyssey in general makes excellent AGMs, the fact they claim "dual use" is almost uniquely accurate.

But are you sure you need AGM? Flooded is cheaper and lasts longer, so $ per AH per year overall costs will be much lower.

But if you do go for the Odyssey, a standard automotive size like G31 may make things easier

Check out PC2150S

And find a local source, paying shipping costs for lead is nuts.

 

[Tiny Metal Tube]

^ Yeah, either AGM or I've been thinking about LiFePO4... But $1000 for 100Ah is pure insanity.  The batteries will be in the cargo bay with me and I don't want to have to cut more holes (venting) than necessary. Also floodeds have to be upright and we don't exactly drive on the best roads.  Call me paranoid.

That PC2150S looks pretty sweet (400 cycles at 80% discharge!). $405 for 100Ah is still pretty high but I'm sure it's worth it given it has a 4.5 star rating on Amazon. Thanks.

The PC1800-FT still provides better bang-per-buck though. $130 more and double the Ah.

 

[highdesertranger]

remember 400 cycles is just over a year if you cycle everyday. also you will get less if cycled more then 80%. highdesertranger

 

[Canine]

If you discharge it to 50% and charge it fully nearly every day, it will last longer. If you discharge to only 30% and charge it nearly every day, it will last even longer. While I can't speak specifically to this battery, not discharging so deep makes a huge difference.

 

[John61CT]

Enersys/Odyssey just gives that 80% DoD vs cycles spec for marketing purposes.

Doesn't mean their products aren't top-notch, and yes, don't regularly go below 50% if possible, 4-6 year lifetimes are to be expected if cared for well.

However there are variations between their lines, the G31 is known good from hundreds of references over the years by experts I trust.

I'll let you do the research between the two.

Tip: the one that weighs more oz/AH will last longer.

All that said, the Deka FLAs are the better value choice, unless you literally have to install your batts sideways, or you're happy to pay lots more $/AH/yr for a very little inconvenience.

BTW the specs to properly care for AGM are much narrower, more demanding, may require also buying more high-end infrastructure equipment, FLA is both more robust and gives a lot more leeway for stock charge sources.

 

[Tiny Metal Tube]

Yeah don't worry folks, I'll try to keep the batteries over 60%.

 

[tx2sturgis]

Batteries are a lot like tires:

If your vehicle is rarely driven, the tires will last a long time...measured in years. But 40,000 miles of use over a year, or over 5 years, is the same.

Batteries will certainly last longer if you don't use them much. 

But is that why we buy them? To not use?

If you pull them down to 50% (using 1/2) every day for 1 year, that's the same 'use' as a battery pulled down to 75% (using 1/4) everyday for 2 years. 

Of course this is a gross oversimplification, but them's the facts. 

But the warranty, prorated as most are when bought locally, favors the person who churns thru the battery's life in a much shorter time. 

Not saying you should deliberately abuse them, and gentle use will certainly extend the life, but don't be afraid to cycle them if that's what you need to do. 

(oh this will bring them out of the woodwork...just watch!)

 

[Canine]

tx2sturgis, that is so interesting. Have never thought about it like that. I just checked out one Fullriver, 12 volt, 140 a/h battery and it actually has a bit more lifetime amps being discharged to 90% discharge than to a 10% discharge. It's roughly the same throughout the life cycle like you stated. I want to disagree with you, but the math for at least this one battery proved you right. Very interesting.

 

[Weight]

Tires are not safe after about 5 or 6 years, even if not used.
LiFePo battery chemistry can not be charged below freezing.
Lead chemistries benefit greatly with a temperature compensated charger. One with a probe on the battery.

 

[tx2sturgis]

Tires are not safe after about 5 or 6 years, even if not used. 

And most batteries also have a certain date so that after that amount of time, 2 years, 4 years, whatever, the manufacturer is telling you that you are on your own.

Borrowed time.

But you can use the heck out of those batteries in the alloted time and still probably be in good standing if the battery shows low capacity within the warranty. 

Instead of mileage-based tread life warranty, IF tires had a prorated warranty based on time only, we might see some being replaced for free many times in the 3 (or how ever many) year warranty because an owner put many tens of thousands of miles on in the alloted time. 

Batteries just don't have an amperage based 'odometer' so we are stuck with all the warranties based on number of months in service.

 

[John61CT]

The lifetime#cycles curve vs DoD are shaped differently for different chemistries, manufacturers and even lines within one mfg.

50% is just a guideline, most batts lifetimes are greatly shortened once you start *regularly* going much lower.

It is very useful as a general comparison benchmark, but unfortunately the gap between lab conditions and results IRL widens once you go below the top tier. IOW cheaper vendors lie like crazy so definitely don't pull those down too far.

Unless you're working warrantee swaps.

Personally with trusted top makers and proper care, warrantee issues are usually non-existent except an occasional defective cell out of a large bank.

Yes if you are aware what you're doing and want to save weight, don't mind replacing every 2-3 years rather than 6-10, feel free to get a smaller bank and draw down to 80% DoD.

But that's maybe 2% of users that clued in, the vast majority of deep-cycling users completely abusing their batts, ignorance heedless or just not caring is maybe 90%, and even if it's arbitrary tge 50% guideline can help them reduce their costs $/AH/yr.

Of course members of this forum tend to be educated, more in the top 10%, present company excepted

 

[tx2sturgis]

Yep...hey I'm not recommending abuse or regularly depleting a battery, just making an observation. The warranties tend to favor the person who can't make good batteries last awhile. 

BTW, those giant lead-acid flooded wet cells at the local land-line based phone company central offices can last for 30-50 years....because they are very rarely cycled....they remain at float voltage, in cool temperatures, for decades.

 

[John61CT]

Yes, UPS / standby use case, actually a different design from deep cycling.

Most too heavy even in 2V cells for mobile use.

But excellent value for off-grid cabin, if you come across the auctions, their scheduled EOL is many years before they actually start failing.

Just make sure to find out the weight before bidding, some can't be moved without a forklift.

BTW forklift batteries are also fantastic, talk about true deep cycling! Not for starting fuel ones, the all-electric forklifts. Try to pickup the charging station to match as well, but need a powerful mains circuit, 50A I guess.

 

[tx2sturgis]

Yeah the charging stations for electric forklift batteries are not something you will normally be able to power from solar....usually 220v, or sometimes 440v 3 phase. 

I know a guy who powers his off-grid home with locomotive batteries....but this is way off-topic and I'm as guilty as anyone of thread drift.

I hear a hammer being lifted as we speak.