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ook so i have a question ive read most of the post on the subject aboout lithium batteries being a pain to use with solar if your not knowledgeable , mostly all i have read is about cells with or without bms and ,keeping the cell voltage even so they dont fail from over or under voltage , you make it sound hard to keep the voltage in the cells balanced, because even if you balance them (which i heard you can do before connecting a bms by running them parrallel and letting them sit 24 hours idk if its true)that over time the voltage will be uneven because no cell is 100% the same? For the record im a noob with solar and lithium..also can i use drop in replacements for sla that are lithium? or will the same problem arise? i know technically they are still just cells with a bms...allso i gather i cant use a standard charger like midnight solar clasic? btw im looking to run my fridge and some led lights off a lithium bank nothing big ..powered by solar and wind ..was planning on using midnight solar classic to do it ....PLEASE dont be over critical to me.. but help would be appreciated
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When using LFP cells (don't even try to use other lithium mixes) you have to work in the middle of the battery capacity range, to avoid the "dangerous" area of over or under voltageing one cell in the pack. So if you need a 100Ah you have to buy a 130Ah battery, to be able to work in the "safe space".
BMS systems claim to be able to manage the imbalances, but often need a special charger the BMS can control. This is all pretty tough for well versed system owners, and for a starter system, unless the installer gives you a turnkey system and a 15 year warranty, I would not touch LFP at this date.
The Classic can be programmed to do many things, but YOU have to know the how and why you chose a particular group of settings for it,
Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-ListerComment
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oh i know a bit about lithium and i would use any thing other than lithium phosphate if i did use lithium ...i see you use nickel iron batteries i heard some of those have a 80% depth of charge cost a pretty penny though have you been using it long ? im really trying to find something better than lead acid ..i think its crazy i can buy a 400ah fla or sla and only be able to actually use 200 of it or so..
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Lithium Iron Phosphate (LFP) batteries are not that hard to use, but you can't just connect them together and then set and forget unless you buy something like a Tesla battery.
As you have said it is important to get the battery balanced before you commission it. The best way to do this is to connect the cells in parallel and use a charger to charge them to 3.6V then let the charge current taper off to nearly zero.
It is important to get the charge settings right. This is possible with the Solar Classic.
The batteries will only go out of balance very slowly, it happens over months and years. You can either check and rebalance the battery yourself, or you can buy equipment that will automatically do it for you.
As a bare minimum I would recommend installing some sort of individual cell monitoring. This could be as simple as a Cellog8, or something more complex. You should also have an accurate multimeter to measure the individual battery cell voltages. I use a Uni-T UT61E
As you have said the critical thing with LFP batteries is to not let the any individual cell voltage go outside the safe operating range of 3.6V-2.8V. The Cellog8 can be programmed to give you an audible alarm if any of the individual battery cells goes out of the safe operating range. If you want better protection you can buy extra equipment that will disconnect the battery if this occurs.
If what I have said has not been too scary you might want to look further into this.
Before you go any further you will have to work out your daily power requirements in kWh, and your peak power use in kW. Another important factor is whether or not you want to use a generator.
Have you had much experience with electronics in the past?
Simon
Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller
Off-Grid LFP(LiFePO4) system since April 2013Comment
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Relax and take a deep breath, and relax.Let's talk about why Lithium Batteries are not used in solar systems today. Yes there are a few, but they are rare experimenters. The question is why are not people using them in Solar? Simple answer economics.Both short term and long term economics do not work out.
To compare apples to apples or Pb to LFP we must apply rule #75 which states for every 100 wh of Pb takes 75 wh of LFP to be equal usable capacity. So if we wanted to use 1 Kwh per day of usable energy we would buy either a 5 Kwh Pb battery of 4 Kwh LFP battery. Both gives us 1 Kwh per day, or 3 Kwh usable before recharge.
OK here is the deal breaker. The Pb battery will cost you $800 to $1000 and last about 5 to 7 years. A Chi-Com LFP will cost you $2000 and you would be extremely lucky for it to last 5 years.The market is not stupid, they buy the Pb battery.
As for a BMS. any commercial solution requires a BMS for the simple fact the public knows nothing. Thus manufactures must limit liability losses and include a BMS. Without a BMS is an open and shut law suit for anyone who wants to suit them. Lots of fire with lithium batteries and cases are extremely easy to win because everyone knows Lithium Batteries explode.
Last edited by Sunking; 07-27-2016, 11:10 AM.MSEE, PEComment
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They usually only explode when improperly charged, discharged, or damaged. I've got about 20 lithium-ion batteries in my house for use with projects and I even use them to jump start my car. Everyone of us with a smartphone holds a Li-Ion battery up to their face daily. Only one that has ever caught fire on me was one that I shot a hole through to see just how bad it was. Even then, it took a nail being shoved through the hole in the cell for it to actually catch fire.
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I have dozens of LiPo batteries for my RC planes without any of them going up in flames but there is always a chance something goes wrong while they are charging or discharging.
Have you seen any of those new hover boards ignite lately? I am sure they have Li batteries of some kind.Comment
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Yeah those are riddled with problems anyway. One, it requires quite a bit of instantaneous power to keep someone upright who is leaning way above the center of gravity for the device, the batteries that are small enough to fit in those probably aren't rated for that much current. Also, those things get abused quite often from falls and other stuff damaging them. Lastly, most people have cheap crap Chinese no name "hoverboards" which are poorly designed and only cost like $200. They probably went with cheap batteries and cheap speed controllers that have a tendency to short out.
On a side note, what type of planes do you have? I have a few super cubs, I love em! I even bought the floats so I could land and take off from the water.
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You are correct about those hover boards being cheap Chinese crap.
The 4 electric are; a Zephyr II made by Ritewing, a SkySurfer V 2, a small Cub (really an indoor model) and a Bumblebee 450 quad copter. I also have a Tower Hobbie Nitro Trainer that has seen better days. I haven't flown much lately but hope to get up again when the weather cools off this fall.Comment
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so i found a company i was thinking about using...heres the link to the battery i was looking at... http://www.lithiumion-batteries.com/...on-battery.php ......... any input would be much appreciated some one suggested to me the other day just buying the cells and bms then i could put digital monitors and fuses on each one on top of that ..but i dont see why this pack wouldnt work for me..? also i do know a good bit about electronics but im not a expertComment
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not sure what a pb is...and i do know a bit about electronics ,btw or electric drilll batteries not multi cell? i have tons of them and never have a problem wasnt sure if they were any way my buddy suggested putting together my own cells buying a bms and putting digital monitors on each cell and adding fuses on top of what the bms uses ...but i was considering a prebuilt i wana post the link so i can get some input on it http://www.lithiumion-batteries.com/...on-battery.php any input would be appreciated ...Comment
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pb is short for Lead.
As for that lithium ion battery. lets take a look at what it says it can do and how much it will cost to generate power.
So it is a 48v 100 Ah battery. That calculates to a 4.8kWh at 100% SOC. The claim is 3000 to 5000 cycles of 100%. So lets say 4000 cycles which would come to 4000 x 4.8kWh = 19200kWh. The price (excluding installation or any other materials) is $5000. So $5000/ 19200kWh = $0.26/kWh. Not bad for CA or Hawaii but way too much for just about the rest of the US.
And the true cost is more than the advertised $5000 due to needing a charger and installation. Also if you get less than 100% discharge or less than 4000 cycles the cost goes up per kWh.
IMO it is not a financially smart investment.Comment
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> im not familiar with what Pb is?
Pb is the chemical abbreviation for Lead. H2SO4 is Sulfuric acid. So a lead acid battery would be Pb H2SO4 and abbreviated to Pb for simplicity
Simple is key here. You have a lot of energy stored in batteries. Lot's of $$ in a well engineered charge controller. then you take a couple dozen DIY balance boards, string them together and call it a BMS and sell it to neophytes. Problem is, the balance boards and all their wires are just more stuff waiting to go wrong, with uncertain failure modes.
Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-ListerComment
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It was sarcasm to make a point that for consumer products with respect to Li batteries will always have some sort of BMS.
Currently in my position I have over 200 Lithium battery's in various forms. 150 or so for RC planes. dozen or so in cell phones and cyber toys. 30 large format cells installed in a racing golf cart Another 8 large format in my ham shack on solar. and a new set for the golf cart waiting to go in.
MSEE, PEComment
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