Battery Time: Few questions

[BradKW]

Solar install is coming up on to-do list and I've been putting off battery decision long enough. It appears there is a place in Miami that I can drive to and save some big shipping costs, and their prices look to be good:  http://www.atlanticbattery.com/category_v3.aspx?categoryID=79

I sent email inquiry, but I have had exactly 0% success getting ANY response from any solar-related company via their email link. I will call and see how availability works or if things need to be ordered from somewhere else. I'm leaning heavily towards getting four L16H-AC, which are 6v 435Ah for around $300/ea.

I would appreciate any feedback on that, as Trojan has so many prefixes and suffixes and product use descriptions that when combined with trying to shop price combined with avoiding shipping, I keep getting a bit overwhelmed. I want to avoid a habit I have in situations like that, where I say "F-it, I'll take THAT one".

I recall reading something once that there was a way to get out of core charges for new solar setups...? Or perhaps I dreamed it, hard to say.

Four of those would give me 870Ah with 960 watts in panels. But since I'd really only have 435Ah usable to 50%, would getting 6 batteries with total of 1300Ah be ok?

I'm looking at a window AC unit, 5000btu, that is listed as 4.5 amps. http://www.homedepot.com/p/5-000-BT...r-with-Follow-Me-LCD-Remote-Control/205167134

Please refresh my memory as to what 4.5 amps at 110v translates into runtime from my 12v batteries...I guess assuming that it ran constantly.

Your help is, as always, much appreciated    

 

[SternWake]

Peukert's law could be the uranium nail in the coffin.

 
4.5 amps x 110v is  495 watts.
495 watts + 20% more for inverter inefficiency= 594 watts

594 watts ~12.2v= 48.68 amps.  i use 12.2v as an average even though initially it would be 12.7 or so, and near the end 11.6 under that load.

48.68 amps on 870 Ah of batteries still has Peukert eating a good portion of the total available capacity.

https://en.wikipedia.org/wiki/Peukert's_law


According to this peukert calculator, and estimating peukert coefficient of 1.15, which is likely generous to those trojan L16's, that 870Ah of batteries is down to only 485AH total

http://www.csgnetwork.com/batterylifecalc.html

485/2  =242.5 AH to provide at that discharge rate before 50% is reached.

242/48.68 amps is 4.97 hours

So assuming battery temp of 77F at night with no solar recharging, you could power that window shaker for 5 hours flat out before hitting 50% , assuming of course the batteries are healthy and fully charged at the beginning of the discharge cycle and appropriate thickness cabling goes between batteries and to Inverter and the windowshaker AC  is the Only load on the batteries too.

The actual duty cycle of the window shaker, the actual peukert coefficient of the batteries, and the actual efficiency of the inverter at that load are all influencing variables. Also keep in mind the peukert number will increase as the batteries age, meaning you will have even less total capacity.

You will not be able to have too much solar trying to run a window shaker 24/7.  The insulation you add is very important in this instance.  More battery powering the load means Peukert robs less overall capacity.

Getting back upto 100% will be an issue as you will be taking a large percentage of that solar wattage to power the window shaker.

Not getting upto 100% regularly, and not being able to perform EQ charges every 30 cycles will have those batteries lose capacity at a much higher than acceptable rate.

With such large heavy batteries, good luck getting them to waive core charge fees, as that is hundreds of pounds of Lead.

I think this rather massive power requirements  fall much better into the realm of Lifepo4's as they have almost no capacity robbing peukert factor, and do not require the 100% recharge As often as possible and you can safely use 80% of their capacity meaning you need less total capacity than a similar lead acid battery bank.

I'll defer to Blars on Lifepo4

 

[BradKW]

Thanks SW, 4-5 hours full out seems pretty good, so maybe I'll roll the dice on a total of 6 batteries with hope of not needing generator for most part.

And with all the insulation I'll have, my hope is that AC will only need to run at 50% greatly extending the duration. It seems possible anyway.

LiPO4 would be wonderful, but it's just too expensive still. $1800 will get me 1300Ah (650Ah usable) in lead acid, while similar capacity would be over $5,000 in LiPO4 I believe.

 

[jimindenver]

Those are huge batteries, Good thing you have a box truck with a lift gate.

 

[Mobilesport]

Thanks SW, 4-5 hours full out seems pretty good, so maybe I'll roll the dice on a total of 6 batteries with hope of not needing generator for most part.

And with all the insulation I'll have, my hope is that AC will only need to run at 50% greatly extending the duration. It seems possible anyway.

LiPO4 would be wonderful, but it's just too expensive still. $1800 will get me 1300Ah (650Ah usable) in lead acid, while similar capacity would be over $5,000 in LiPO4 I believe.

I think you'll find yourself running the 5000 btu constantly on hot/humid days , you'll probably have to sit right in front of it too , move away from it even 3 feet and you'll be sweating.

 

[SternWake]

Those are huge batteries, Good thing you have a box truck with a lift gate.

Yeah, when those things are at absorption voltage offgassing..

The occasional application of a high amp charging source for some bulk charging in the coolest part of the morning can do wonders.

I mention the temperature as I have found my average battery temperature to be significantly hotter than Ambient temperatures, always, as it is Always charging or discharging, never just resting.  High amp charging when ambient temps are hot and battery is still hot from working hard all night, well, 120F is the limit on battery temperature, and I think it might be all too easy to get them this hot in your usage and current location.

latest battery temp observation:
I plugged in a while ago at about 75% charged, battery was 74.5f, ambient was 71f
40 initial amps tapered to under 30a in less than 10 minutes on a single 90Ah Northstar AGM with 23Ah removed from it.

Now about 2 hours in, battery is 85.5f accepting 5.1 amps at 14.4v Ambient temp in van is 71.  Below van where battery is is 69.5f.

That's an 11 degree  battery temperature rise in less than 2 hours!

My AH counter/ battery monitor is Now wrong, saying only 2Ah from full.  It is likely closer to 4.5Ah from full and will take 2 more hours minimum,  held at 14.4v, to get there.

Keep in mind trojan 'recommends' a charging source which can provide 10 to 13% of the total Ah bank capacity and one which seeks a 14.8v absorption voltage at 77f.

Rolls Surrette recommends upto a 18% rate for off grid solar so that the peak sunlight hours have a chance to get the batteries near as possible to a true 100%.


A Very good read:

http://rollsbattery.com/uploads/pdfs/documents/user_manuals/Rolls_Battery_Manual.pdf



So 1000Ah of battery should get a 100 to 130 amp charger if one is going to plug in or run a generator to recharge.

Its a lot of battery to chronically undercharge and have die prematurely.  How prematurely depends on how well you can recharge them, while not regularly overdischarging them below 50%.

The 80 to 100% range is gonna take 4 hours and longer once the batteries get beat up a bit.
Getting to 80% can be done quickly with a high amp charging source.

How much solar can you fit?

Do these newer window shakers drip their condensed water over the condenser fins to assist heat removal from them?

I wonder if one can give a window shaker some spit and polish and increase their efficiency a bit.  Unneeded when one can plug in and enrich the power company, but on battery power, the gains could, perhaps, be significant.

Anyone looked into this?

 

[Spaceman Spiff]

The only thing I can add is: If this is your first experience with running off batteries, I would get the cheapest GC2 batteries I could find.  I remember reading when I was researching my system that your first set of batteries are 'learner' batteries and will probabily die a premature death.

IMO get FLA (not AGM) as you will want to monitor their condition often by taking specific gravity measurements.  And with the number of batteries you are using a vented battery box is advisable.

 -- Spiff

 

[jimindenver]

There is some wisdom to this thought process even if it may sound as someone may be trying to talk down to you. My first big battery was a 8-D starting battery that would likely still be here were I using it in the same fashion as I do the Lifelines. Instead I beat the hell out of it running test, pushing the limits and getting my push the button education. How long could the solar hold it up running the microwave, how many hours could it run a 100w bulb, how many days before we had to recharge and of course the air conditioner. It could run the microwave by itself for a short run but couldn't start the A/C without the solar. Trying that was just too much after two years of torture, it was a cheap education at $70. By the time I replaced it I knew much more of what I needed/ wanted, what the different types did for me and I also knew I had no need to push it anymore. The expensive bank lives a coddled life lightly cycled and always charged. Their power will be there when it's needed.

The 8-D starting batteries are well under $200 at the likes of Auto Zone. They are thinner plates and will puke up the power if needed. Three will run my little A/C over night and not be at 50%. Three of them would have also stood up to the abuse much better and even done well enough now with the light cycling. 325 Ah is still a lot of usable power.

Inexpensive 6v's would be a better cheap solution and last longer and take abuse better. Cheap AGM telco batteries have been popular but while they are AGM, they are not the same as a Lifeline or other top of the line AGM. They can't take what ever you throw at them.

Lots of options to discuss

 

[SternWake]

The Trojan  L16 plate thickness is significantly more than the t-105 and it should, all factors being equal, outcycle the venerable T-105.

A living on  battery power  newb does not have to become a battery murderer.  It really is all about not overdischarging the battery, and proper recharging, and proper recharging consists mostly of achieving the proper absorption voltage, and holding that voltage for the proper amount of time, as often as possible.  Figuring out the proper absorption voltage for the temperature requires effort and measuring tools, and how long to hold it requires a hydrometer and an Ammeter to figure it out, and these values will change as the battery ages.

With AGMS there is the initial charge rate to consider as well as some simply require huge charge currents when discharged to 50%.  If these high amp AGMS do not get the high amps when depleted to the 50% level, they will not have their full available capacity to give but still 'appear' to be fully charged.

Running an AC on battery power is a huge undertaking, requiring that large battery bank, but equal thought must go into being able to achieve the 100% recharge, while still needing to power the AC.

If one was able to turn off the AC and let the 900 watts of  solar do its thing for a day or 2 to reach that 100%  battery state of charge level it would be rather simple, but recharging the batteries to full while still requiring the solar to power the AC, well that is the deal breaker.  Another 600+ watts of solar would be needed for this not to be a factor.

The Trojan  L16 is a mighty lead acid battery, but it still needs to get to 100% every so often, you can't just cycle these from 50 to 80% day after day. After 14 cycles of doing this they would not be able to run the AC for more than 1.5 hours without dropping to 50% or well below, and recharging them at this point would likely 4 to 8 hours at absorption voltage, and then an Equalization charge applied for at least 2 hours after that.

Assuming a 100% duty cycle on the AC, compared to a 50% one has huge ramifications on battery capacity required, as well as recharging capacity required.  Very good Insulation and an AC designed for efficiency rather than power company enrichment can have huge effects on capacity and recharge requirements required to lessen the AC's duty cycle as much as possible.

Other electrical loads on the batteries have not been discussed either.  Laptop's and 12v compressor fridge's electrical consumption can be significant too.

I hope this does not come off as being talked down to.  My goal/ intentions here are to help people from murdering Lead acid batteries prematurely, and doing this requires more than just enough battery capacity to run the intended loads for 24 hours.  There are a LOT of considerations in the designing stage to take into account to have a chance of achieving even half the claimed cycle life of the batteries, which is determined in a lab with the exact proper recharging after each discharge cycle.

In actual use, most people are lucky to achieve 1/5th the number of the lab rated cycle life.  Those achieving more than half the claimed lab cycle life are doing pretty darn well.

Those claiming to achieve the full claimed cycle life in actual  heavy duty deep cycle service, are smoking crack.

 

[BradKW]

Thanks, good info...I was tempting myself to think going generator-free might actually be an option if I went with 6 batteries, but I think I'll start with 4 and a 2000i Honda. For the most part, it's not like an AC would have to run 24/7...I do work 40+ a week, so giving time for 100% charge won't be a problem.

As for starting with cheap batteries, I'm not necessarily opposed to the idea, but I just don't see any options that will even get me close to doing what I want without still spending a good amount.

Nothing came across as "talking down" to me, but I have a pretty thick skin, so perhaps I just didn't notice

I actually decided awhile ago that once I start on electrical assembly, wire sizes, fuses, connections, battery monitoring, etc, that I was going to offer Sternwake a consulting fee via PayPal so maybe he'll talk to me on the phone. For some reason when it comes to electrical stuff, I really have a hard time retaining what I've learned reading about it. That should change once I actually start applying it hands-on. But anyway, give some thought to your consulting fees

 

[jimindenver]

Here is something else to consider. Are you going to use the batteries today? The warranty starts running out as soon as you buy them if new. Not to mention I see a number of ads on CL for batteries that were bought for a project that never happened. My Lifelines came unused from just such a project. He paid over two grand and sold them for $600 just to store them for years. I can understand a one time thing like a good used deal but new batteries will always be there.

I can say that I have not ruined a pair of jeans testing the AGM's yet.

 

[BradKW]

Here is something else to consider. Are you going to use the batteries today? The warranty starts running out as soon as you buy them if new. Not to mention I see a number of ads on CL for batteries that were bought for a project that never happened. My Lifelines came unused from just such a project. He paid over two grand and sold them for $600 just to store them for years. I can understand a one time thing like a good used deal but new batteries will always be there.

I can say that I have not ruined a pair of jeans testing the AGM's yet.

I envy the CL listings of major metro areas...the Keys get about squat on a regular basis, and Miami (heck, even Largo) listings are just too far away to pursue items that aren't a "sure thing".


While I don't necessarily "need" the batteries now, I would like to have them so I can start experimenting, and given their size and weight, I need to figure out how and where to put them for a balanced and convenient build. At 18" high, I'm even considering a recessed floor mounting. Unfortunately, I'm just not the CAD "design then build" guy...I'm much more the build, design, build some more, re-design, etc ...guy. Probably has a lot to do with why I struggle with electric...it is inherently opposite how I approach problems.

What model AC do you have again? I remember you posting it and saying how efficient it was a while back...

I'm sure that not ruining your jeans must make some sorta sense in some context, but I guess I missed it...    

 

[Optimistic Paranoid]

I'm sure that not ruining your jeans must make some sorta sense in some context, but I guess I missed it...    

It only takes a few drops of spilled battery acid to eat a hole in your jeans.  I learned that the hard way back when I was selling auto parts.  The batteries came in dry and we used to have to fill them with acid from 5 gallon containers . . .

 

[jimindenver]

Brad

John is right, one drop of acid and instant hole. You will get use to it because the way you check those FLA batteries is with a hydrometer. Pop the caps, check the water and stick the hydrometer in to each hole and suck out some acid to check the specific gravity. It is more accurate than a voltage meter and will tell you if one cell is running lower than the rest.

This is the window shaker I use. The 50-65w it will save you will not mater while running off of your solar, but it will when running off of battery.

http://www.ajmadison.com/cgi-bin/ajmadison/FFRE0533Q1.html?brand_store=1

 

[AngryVanMan]

Brad, this is a spreadsheet from a member's website, GaryGary, that you can use to estimate the heat load of your cube.  It'll give you an idea of what kind of duty cycle and run time you might expect with your A/C.  It's just an adaptation of standard HVAC formulas for buildings - but it should get you in the ballpark.

Heat Loss Calculator Spreadsheet (Build A Green RV)

This sheet was designed for heating applications, so the BTU/hr comes up as a negative number if you put in temperatures for cooling, but from what I can tell just dropping the negative sign will get you usable results.  One thing to note is this does not model solar heat gain in any way, so things like radiant heat absorbed through windows, darker paints, etc will not be included in the estimate.  For a white van with few windows, the accuracy should still be pretty good.

 

[BradKW]

http://www.ajmadison.com/cgi-bin/ajmadison/FFRE0533Q1.html?brand_store=1

Appears that model was DC'ed, but replacement model seems to have the same great efficiency... 12.2 EER is nice. Just ordered one: https://www.amazon.com/gp/product/B01B4XUUDI/ref=ox_sc_mini_detail?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Thanks!

 

[jimindenver]

Nice Find! The replacement is even more efficient than the original. I can't wait to see what the tag says when you get yours.

 

[jimindenver]

I couldn't take it, I had to find the specs on the new model. It's rated at 410w, that's lower than the old model on low.

 

[NeedAnEscape]

I couldn't take it, I had to find the specs on the new model. It's rated at 410w, that's lower than the old model on low.

Any idea what the start up current is?

 

[flying kurbmaster]

what about those salt water batteries? they sound pretty impressive. ( Aquion)