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gcrank1
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# Posted: 28 Jan 2022 03:39pm - Edited by: gcrank1
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Just around Christmas I was given an opportunity to trial a 50ah LFP. My capacity tests proved it a full 50 available between the 'knees'; I was impressed. Impressed enough that I went the extra and opted in for the 100ah version today.
Wow, only about 30#, thats like a little garden tractor battery, physically the size of a grp 27 lead acid bat. Easy to transfer back & forth to re-charge at home if I didnt have solar at the cabin.
Comes with a pair of Anderson Connector 8ga. leads, Nice Stuff! 8ga will carry 40a, well more load than we use.
At 100ah it will equal 200ah of fla taken to 50% dod or 300ah fla taken to 33% dod (just price out 200-300ah of good quality fla). I understand that lfp will last longer with less than 100 dod also but can still live far longer than fla even if taken 'deep' repeatedly and/or regularly. And lfp will not be harmed if you dont re-charge right away or not keep fully charged; that will kill fla.
More amps ate readily available under load than fla and way faster re-charge, that is, higher C and D rates.
Yeah, its pricey. With our current inflation it, and any other battery chemistry, is likely to be higher this next season anyway and who knows about the 'supply chain issues'; ie, buy now before the money becomes more worthless or stuff isnt available? That rational worked for me.
Hooked up the 1kW inverter, it runs the upright vac just fine  That is something my marine 'deep cycle' wouldnt do.
Im committed now, lol
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Steve_S
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# Posted: 29 Jan 2022 06:27am
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hehehe Welcome to the Light Side !
The IP for LiFePO4 is up in March or April. Factories are going up outside of China and some are in pre-production already. LFP production is also being coupled with other Lithium Cells production facilities.
New Chemistries are also coming out (in production now), so legacy chemistry costs should go down a bit.
I have a large LFP Bank (1190AH/ 30.4kWh) because I need a large reserve (7 days from 0% to 100%). I have discharged the whole enchilada to 2.600V per cell or 0% SOC (we don't do DOD) which cutoff inverter. Then charged by Genset through the Inverter/Charger @ 75A for 8 hours which gives me 5 Days of charge while also providing passthrough power to Cabin during charge.
With my old FLA Bank (428AH@20 Gross / 214AH useable), if charging from 50% DOD to 100% took 12 Hours but only gave me "barely" 2-1/2 days in frugal mode.
The lead cost me 3K +/- in 2015 - now retired !
My LFP was done over time so the costing is weird as I also did experiments & testing with different gear, so it's different for me.
Prebuilt LFP Packs are becoming more common, the quality is going up while prices are coming down. Take a look at SOK Brand for a Good Example.
Also Power Wall & Power Blocks have exploded onto the market as most big companies that make All-In-One Systems are bringing them out like mad to go with the gear. Well Priced and very respectable specs.
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rpe
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# Posted: 29 Jan 2022 08:00am
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Anyone else find the TLA's alone are a barrier to entry for this technology?
(TLA = Three Letter Acronym  )
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Steve_S
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# Posted: 29 Jan 2022 08:53am
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Hahaha, Life is nothing but a pile of Alphabet Soup !
It is a lot like the early Computer days when folks were befuddled with CPU, DRAM, EDO, HDD & FDD etc...
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mj1angier
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# Posted: 29 Jan 2022 09:20am
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I just checked. The last one I got is $150 less than when I got it in Aug. !!
https://www.amazon.com/Rechargeable-Perfectly-Batteries-Maintenance-Free-4000-7000/dp /B08S6WNCM8/ref=sr_1_4?crid=33YWYAVHOWIJJ&keywords=24v%2Blifepo4%2Bbattery&qid=164346 5903&sprefix=24v%2B%2Blifepo4%2Bbattery%2Caps%2C171&sr=8-4&th=1
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gcrank1
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# Posted: 29 Jan 2022 11:52am - Edited by: gcrank1
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The diysolarforum.com site has a listing of the Alpha-Code  , even visitors can view it.
Basics are:
FLA, flooded lead acid, that traditional pop-top bats and sealed tops, what we are are used to in cars. This includes 'marine' deep cycle/rv/leisure and golf-cart bats. Those are the 'legacy chemistries' Steve mentioned.
LFP, LiFePO4, the current hot battery for diy elec 'storage'. Safe, power dense, light-weight, no off-gassing and on & on.
SOC, state of charge; a measure of battery capacity from the top voltage; ie, use 20% from a 100% full bat and your soc is 80%.
DOD, depth of discharge; a measure of how much you take out; ie, a 20% dod takes you to 80% capacity.
BTK, between the knees, the discharge if graphed for the lfp bats is pretty flat, but at either end is a sharp change up/down. Those are the 'knees'. As long as you keep that bat anywhere btk's youre good.
And sooo much more.....
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gcrank1
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# Posted: 29 Jan 2022 12:12pm - Edited by: gcrank1
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With my '612w' of array I probably really only get an av of 400ish w. At 3-3.5 hrs/day thats 1200-1400w/day.
My 2 old 'marine' bats might still give me 140ah gross/70ah net (910w)
This new lfp an easy 80, even 100ah (1300w).
So my bank for our modest use is up to 2200ish w usable from a full charge. My solar has proven to do 50-100ah (650-1300w) depending upon the day (my 'day' ends by 1pm, tall thick pines to the west).
Our usage is within that, and keeping heavy use to solar hours recharges the bank and we also run off the solar thus leaving the bank mostly for evening.
This is to say our needs and system pretty much balances out on a heavy use 24hrs but really gives us 2 good days, maybe 3 now, of autonomy. We also have the 2k inv/gen and an ac charger if needed.
The LFP will be no maintenance compared to FLA and I can safely use it inside, like on our rare visits this winter (solar is shut down), easy to transport in, hook up the 300w inverter and we are running on 120vac.
In the two years we have been using this place with no elec grid con, which would have been about $40/mo after the initial $3k'ish to hook up, our 'savings' just on the monthly billing have been about the same as the cost of our bought new gen and this LFP battery. I nursed the old bats that came with the place and acquired the 2 'marine' bats for free so I had no bat expenses until now.
I like this way of calculatin! Guess I could say my new buy in is already amortized down
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groingo
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# Posted: 29 Jan 2022 12:52pm - Edited by: groingo
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The best thing I like about Lithium batteries is they charge much faster floodeds, you can draw them down a lot without hurting them, go months without worrying about if they held the charge and my BACK loves the light weight as well as ZERO fumes to deal with, I paid $799.00 for my 100 Ah Battleborn a year ago and whenever I have any question the guys at BB have been great so I feel even with decling prices the PHONE SUPPORT is worth the price....Lithium battery GOOD!
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gcrank1
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# Posted: 29 Jan 2022 05:23pm - Edited by: gcrank1
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My solar is discon right now but no worries. The 'plan' is to hook up the lfp in cabin asap with the inverter and 'just live' like we want to, monitoring the 'unit' and taking notes. When it hits the low above the knee I'll stop. If we need to we can run the gen.
Once it shows me what it does in real life going deep I'll bring it home to charge on the Meanwell power supply to time the re-charge (est only 3-4 hrs).
With that as my baseline I will know what to expect while I do some remodeling of the solar system, eventually getting the 2 marine bats in parallel to just idle along and eventually tuning the scc for the lfp profile (its at AGM settings, no equalize, I think mostly I need to bring the dc voltage down a smidge).
Ive noted some users are running lfp with fla successfully, the lfp charges and discharges first (lower internal resistance) which effectively leaves the fla 'in reserve' while the lfp gets down to 12.8ish v (the fully charged voltage of fla) and they back up the lfp.
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paulz
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# Posted: 29 Jan 2022 06:40pm
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Quoting: groingo The best thing I like about Lithium batteries is they charge much faster floodeds, you can draw them down a lot without hurting them, go months without worrying about if they held the charge and my BACK loves the light weight as well as ZERO fumes to deal with,
And no corrosion.
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rpe
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# Posted: 29 Jan 2022 11:13pm
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Quoting: gcrank1 The diysolarforum.com site has a listing of the Alpha-Code , even visitors can view it. Basics are:
Thanks! Back to post #1 for me with the enigma code in hand!
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gcrank1
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# Posted: 30 Jan 2022 02:21pm
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Ran the porta-fridge, 4.8ish amps, on the new bat last night for 10.5 hrs. The onboard voltmeter went from 13.3 to 13.1 (both resting v), .2 volt drop with 50amps pulled out of a 100ah battery. If that holds true another -.2 would take it to 12.9 which is still nowhere near too low on lfp.
Looks like this may be the whole hog 100ah usable 'between the knees' so no need to limit usage to only 80% except to maybe maximize the number of cycles above 2000ish. Since 2000 is likely well more than we will do in the next ten years it very well may not matter.
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travellerw
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# Posted: 30 Jan 2022 04:03pm
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LFP is a game changer for sure. We lived 3 years on FLA and 2 years on LFP. Our FLA bank was 600ah and our LFP bank was 400AH.
We got an extra 100 usable AH at 1/2 the weight and no worries about venting.
On really good solar days we used to cook on our induction HOB, heat water for showers, use our washing machine, and charge all our stuff. Didn't care if the batts got back to %100.. Didn't matter.
The only real downsides are that they are more complex (BMS required) and can be damaged much easier. Also you need to forget everything you know about FLA. If you treat a LFP like an FLA, I guarantee a quick death.
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gcrank1
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# Posted: 30 Jan 2022 05:01pm - Edited by: gcrank1
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Can you be more specific about that caveat 'dont treat lfp like fla'?
Being used to not going deeper than 50% soc, and my target was not below 70% Im already used to watching the low end. And I think the inverter lvd will trip out the inv before the lfp bms lvd anyway so I should be safe there?
The middle is just use the amps/watts.
I dont have to recharge asap after use like fla or watch the water levels and/or SG or equalize.
They will easily take a .5C or D., Im under that both ways.
The 'be careful' I sense is mostly dont go beyond the 3.65v per cell, and Steve S has said 14.0 for a charger setting will top out at 90-95% full charge, about at the knee, and never get into danger.
Am I missing something?
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Steve_S
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# Posted: 30 Jan 2022 07:40pm
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check pages 12,13 of attached PDF.
SOC Tables & Charging info.
If you have a 12V and have the inverter set to cutoff @ 11.0V (2.750Vpc), once the inverter cuts off, the cells will recover a bit. Now even if the BMS Low Volt Disconnect is set to 2.500 and the inverter gets to 10.0V and the BMS disconnects, that will drop the inverter obviously. The cells will again recover a bit and the BMS (if it's not "off") will reconnect to receive charge.
Different BMS' do have different behaviours and of course a variety of capabilities & functions. They are pretty tough unless you do something wrong.
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gcrank1
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# Posted: 30 Jan 2022 08:53pm - Edited by: gcrank1
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Thanx, Steve, that is a great ref to have on this thread! Im glad you caught this thread, wanted to bounce it off you.
I will charge the 12v lfp at home on the Meanwell 40a set at 14.0v.
As for the cabin,
My old Blue Sky 50 mppt is set at no eq, 14.6 B/13.8 A for charging agm's (10ish yrs old, not bad).
600w gross array, 6 panels 2s/3p @ 24v feeds it but I lose my sun pretty much at 1pm. The array is about 40* x south east to the catch the early to noon sun; figure I really only get 3 hrs on a good day.
Brings me to my question, with only 3ish hrs solar do you think the bulk back a smidge to 14.4 would be ok?
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travellerw
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# Posted: 30 Jan 2022 09:09pm - Edited by: travellerw
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Quoting: gcrank1 Can you be more specific about that caveat 'dont treat lfp like fla'?
Mainly not getting back to %100 SOC. Not only is it not required, avoiding it produces the longest life. If you can live between about %30-%90 SOC the cells will probably outlive the item they are powering.
But its more than that. You wanna watch the temps (both high and low). Keep the batts from getting too hot or cold. FLA batts are much more tolerant to this, I have seen many LFPs that were puffed from overheating.
Ensure your solar controllers are fully programmable (not just a "lithium" setting). Use the recommended settings by the battery manufacture (not the controller manufacturer). ENSURE NO EQUALIZATION SETTINGS...
Settings for battery monitor (like the BMV-700) are a little bit of black magic. LFP have such low impedance and high efficiency getting those settings right can take a bunch of trial and error. Google T1Terry and you should find some good posts that give you a starting point.
I also never trusted a MOSFET based BMS (which is pretty much all the built in ones). MOSFETS fail dead short almost always. This leads to the BMS being unable to disconnect in a HVC or LVC event. So I always used a battery monitor that could trip a mechanical device (a solenoid or Blueseas electrical relay) as a backup.
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gcrank1
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# Posted: 30 Jan 2022 10:31pm - Edited by: gcrank1
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Thanx Trav
I intend to not crowd the bms on either end, know well that 'tripping switches' wears em out 1 trip at a time.
Being a monitor and analysis guy helps
We wont leave the lfp in cabin or on solar in freeze season, though it would winter over not in use anyway unhooked from all in/out puts.
Summer heat can be hot for a while here though shade and air flow is easily achieved. Hmmm, wonder about an ice chest with a couple of cooling bottles?
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Steve_S
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# Posted: 31 Jan 2022 06:01am
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LFP Temp Info: (Standard LiFePO4)
Charging Temperature 0℃~55℃ (32F/131F)
Discharging Temperature -20℃~55℃ (-7.6F/131F)
LFP Charging at different temps takes different C-Rates, please see attached Table.
Going over 14.0V (3.500Vpc) is gaining you nothing. Goto 14.0V, allow saturation to where Bulk/Boost cuts off between 7-10A and goes to Float. to allow for topping off.
On BMS'. I started LFP Life with a crap assed dumb BMS in pack one (PreBuilt by ShunBin a disaster) so on rebuilding that and building more packs, I went to Chargery BMS with Relays and now with Solid State Contactors. I went this way to handle 300A Loads and to use some of the features like Passive Balancing. REF: http://chargery.com/BMS8T.asp
Passive Balancing on anything over 100AH is "pointless" Active Balancing is the only way to go with balancing. So I added QNBBM-8S Active Balancers on top. REF: https://deligreen.en.alibaba.com/product/60766503653-806516208/8S_battery_equalizer_b alancer_bms_for_batteries_electronic_accessories_products.html?spm=a2700.shop_plgr.41 413.26.18aa586259a5b1
AFTER ALL THAT - 5 Production Packs and 2 Utility packs, it is ALL Being replaced ! (btw, this is a LOT of Cash, $500USD each pack + S&H)
I am replacing each setup with --
JK-BMS [24S 2A 150A BT] with BlueTooth Part Number: B2A24S15P $143.29 USD
REF Product Link: https://www.aliexpress.com/item/1005003104573871.html
YES, MOSFET Based and our EE's have dissected them to discover High-Quality components (IC's & FETS) which are well overrated for their needs.
Now think on this a sec folks... Look at what I am dumping and what I am replacing it with and this is NOT chump Change for me and my wee monthly disability stipend. I would not do it unless I had the knowledge & faith in it. The WHOLE SECTOR has leaped forward and evolved and thanks to the Membership (DIYSolar) we know what to get & what to avoid...
BTW: Way Back when I was considering Lithium, Creeky was doing those Volt & Bolt batteries and I was seriously considering it and he told me about his RedWings BMS or was it the other odd name, they turned out to be the Chargery's. Long Story short I got redirected away from EV Batteries to LFP (safer, cheaper & new) but decided to stick with Chargery. I rewrote their manuals/docs to English them and worked with Jason (Lead Dev) to improve the firmware, add cold temp controls and to develop the DCC Solid State Smart Contactors with precharge etc built in.
Hopefully this is helpful to you GCrank
LFP Charge Rate at Temps table
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travellerw
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# Posted: 31 Jan 2022 10:03am
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Quoting: gcrank1 Hmmm, wonder about an ice chest with a couple of cooling bottles?
I should have been a little more clear. They aren't that sensitive. However, many people think that since they don't need venting they can stick them in a sealed box and then pull like 100A out of them regularly.
They may not vent gas, but they NEED airflow. Most of the time just passive venting of the battery box is enough (sides and top). However, if you are really working them heavily (like 100A-120A sustained draws for 20 min), and often then some active cooling (like a fan) is a good idea.
I'm also not a big fan of many of the solutions sold on Amazon. I have been watching teardowns on Youtube and most of them are just prismatic cells in a sealed plastic box with electronics double side taped to the top and sides of the cells. The cells are usually not clamped or compressed and just held in the box with more double sided tape. They are probably fine for our light cabin use (hell I can't see drawing more than 20A ever). I wouldn't trust them for something like a boat where high draws like the windlass are regular.
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gcrank1
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# Posted: 31 Jan 2022 10:20am - Edited by: gcrank1
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Your comments and insights are always welcome and appreciated Steve.
Since we have no real 'solar' sub-forum here, and by extension 'batteries and more', etc. comprehensive threads packed with solid content are priceless.
Of course we can go to diysolarforum.com for deeep diving into it all. It makes me feel in over my head quickly, though.
This fora being 'Small Cabin' many of us are on tiny to small solar, and Im focused more on the KISS engineering side of things. I had followed small scale solar since the early-mid '80s and thought I wasnt too ignorant. LOL! Well, a guy doesnt know what he doesnt know..... This past two years has been enlightening.
I 'inherited' this hacked together system with the cabin buy so Ive been trying to maximize it to its capability and re-tune our expectations and needs. Perhaps not the best approach, maybe handicapped?, but it is my real 'starter system' rather than an experimental and experiential toy. And thus far I havent 'killed my 1st set of batteries' as the oft-repeated warning goes. Knock on the lfp plastic case.....
Two things I learned in the 1st year were that in est. for the size of a system many 1)over-est how much solar-elec production 'x system' will produce and (way) 2)under est their needs/requirements. All that results in making something 1/2 the size they should have.
Practical application then is to make your best est., then double it. In terms of performance you will be less likely to be disappointed.
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gcrank1
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# Posted: 31 Jan 2022 10:33am
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Good points Trav; your experience and insights are always great too.
Im not intending (but who does?) to go more than 20a, finalized wiring should be 12ga. Romex to support that on outlets, 14ga on lighting circuits of the 15a capability, even though I will likely not exceed 10a anywhere. But who knows what my wife, or the next owners might assume?
Without the heavy cycling of the lfp, and not been planning on boxing it all up anyway, I should be good then.
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Steve_S
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# Posted: 31 Jan 2022 01:02pm - Edited by: Steve_S
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My place is wired to our Electrical Code, inspected & signed off, similar to yours in the US.
Standard Light & Wall plugs are serviced by 14/2 and less than 10 devices per 15A Breakered circuit. Device = plug, switch or light fixture.
Kitchen plugs are 12/2 each on 20A Breaker & T Plugs.
Could have used 15A Split Plugs with 14/3 but I hate those.
Bathroom is 15A Breakered GFI with 14/2.
Powerhouse/pumphouse 15A Breakered 14/2 which is for Pump (SoftStart Grundfos SQ5) and the light in the building.
PLEASE note that there are many prebuilt batteries out there and it IS a bit of a Wild West. Some really bad, some so-so and all the way up to OMG Wow this is awesome. For GOOD look at SOK Batteries as one example of very well done. These are ALL Sealed without Venting or anything (this is current realtime info). All my battery boxes are closed and no venting, see below...
REF: https://www.us.sokbattery.com/products
These are with the Chargery BMS which is external to case, this is previous setup which I am changing the BMS and removing the QNBBM's.
BUT my system is built to handle 250A off Battery and the Inverter handles 4000W to 12,000W with surge handling. During the Thrash Testing I pulled 200A Loads and running charge up to 250A (big bank so) to find system performance edges and never had an iota of issues on either the DC or AC Side and never tripped a breaker.
PS: I have over 5500 messages on DIYS since it pretty much started... Ahhhh the Good Ol Days ! Most of it is technical and a few guides & manuals as well that were needed and for which I honestly got sick or repeating to noobs constantly, it does get tiresome after a while. Especially the stubborn ones who are fixated on ancient knowledge and won't keep up no matter what. I am quite picky about what/who I answer now over there.
Having issues posting Images from my pages...
Link to my "About my System" pages @ DIYS. Presently out of date as a major update is IN Process. https://diysolarforum.com/threads/my-diy-off-grid-cabin-setup-in-ontario-canada-24vdc -120vac.1484/
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travellerw
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# Posted: 1 Feb 2022 05:56pm
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My experience is all on boats, which is quite different from other systems. I learned a ton building and living full time on our system, but also learned a ton more consulting to other boats. Boats are crazy hostile environments to all the systems, especially in the tropics. Boats move constantly and hit temperatures well over 50c in storage areas.
%75 of the LFP installations were prismatic cells (Winston, CALB or others), with some form of BMS. I worked on everything from homebrew to off-the-shelf BMS solutions (many no longer in business). The other %25 of installations were dominated by BattleBorn or Relion, with a handful of smaller names. Victron, Mastervolt and Midnite were the most common electronics, with Victron being #1.
Its a whole different design philosophy with boats. You shy away from any combined devices (i.e. MPPT controllers combined with inverters). This is to avoid a single point of failure. BMSs with backup disconnects. Solar arrays configured in banks and separated to their own MPPT controller. Separate inverters and battery chargers.. ect ect.. This way a single failure can only take down part of your system and you can continue to "limp". You may have to "limp" for weeks or months as replacements can be very hard to get in far away places. Sometime you have to wait for an acquaintance flying in from Canada, USA, UK, France and have them carry the part in luggage (customs is always fun)! LFP cells are an absolute nightmare to try and ship down there due to their classifications (no carrying those in luggage).
Anyway.. I actually blogged our entire system build and details. Its quite dated as it would be 5-6 years old now and better stuff is out there. However, if anyone is interested I can post a link.
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gcrank1
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# Posted: 1 Feb 2022 08:04pm
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I would think that the marine type and size systems could work well for a lot of small cabin or cottages, just wouldnt need all the marine quality perhaps.
Why dont you start a thread on it geared to this audience, I'll sure follow it
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paulz
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# Posted: 1 Feb 2022 09:07pm - Edited by: paulz
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Travellerw, were you thinking about life in the tropics while your truck was stuck in the snow last weekend?
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travellerw
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# Posted: 2 Feb 2022 10:03am
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Quoting: paulz Travellerw, were you thinking about life in the tropics while your truck was stuck in the snow last weekend?
Sigh.. I think about it everyday.. But I can't change it, so making adventures up here!
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