LA versus lithium battery sizing

What's the current consensus on battery sizing? I have about a 10KW/day load. Currently on 24v but moving to 48v. I currently use
It's has positive plate growth and one cell that doesn't look too good. It's about 9 years old.
Pricing seems to still point to forklift batteries, but if I read correctly lithium may blur the math due to DoD. But what are people doing with regard to DOD on forklifts and lithium batteries? I've been charging at about 60-70% remaining, but have heard of some people bringing forklift batts down to 20% and others who charge at 80%.
.
I was looking at maybe getting 4 of these
which is 938 ah and about $7000.
Is there a lithium alternative that even comes close to the price?
also, how does the max output of lithium work with big startup loads like AC units?
thx
Comments
I hooked mine up to the solar electric system and let it go, charged every day.
Yes they say not to do 'short charging' with the battery not drawn down a good bit. I choose to believe that has to do with the intended purpose as a 'forklift battery', not wanting people to 'hot charge' between shifts. Since solar is a much more gradual charge, in general. I just ignore that bit...
To explain this one needs to consider that in order to achieve a reasonable cycle count with LA, the DOD needs to be kept shallow, therefore a larger initial capacity is required to compensate, for example a 1000 Ah bank is really a 300 Ah, so it's either pay up front or deep discharge and replace frequently this article will help explain https://www.powertechsystems.eu/home/tech-corner/lithium-ion-vs-lead-acid-cost-analysis/. Note the link is using 50% DOD for LA, 100% for LFP to achieve a direct comparison, using lower DOD in both chemistries would have different results but in the end the results would still favor LFP.
https://www.fortresspower.com/how-to-calculate-the-energy-cost-of-different-battery-chemistries/
Also read the attached pdf, there are many comparisons which can be found which come to similar conclusions, so yes the upfront cost is higher but all things considered its lower.
Looking at your consumption of 360 Ah at 24V according to the Classic, assuming that is charging ~20% of that would be losses due to inefficiencies so 288 Ah would be more accurate. Using 300 Ah as a baseline my personal opinion it would be best to have double that for LFP to allow for bad weather and to significantly increase cycle life expectancy. With 600 Ah that would have a nominal capacity of 14.4 kW, my cost for a DIY bank using 24 grade A CALB 200Ah cells would be $ 3,240 (2020 price) excluding shipping, a BMS will cost anywhere between $60 and $200 depending on features required. (A 48V bank would be 300 Ah same cost)
Building a DIY bank is really simple contrary to popular belief, LFP is far superior in every aspect except in temperatures near or below freezing, they are around 98% efficient, charging is extremely fast without a long absorption making generator charging highly efficient and no maintenance or corrosive emissions.
One additional piece of information omitted is, lead acid has a recycling value, I recovered 20% scrap value on initial cost, this may vary depending on location.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Trojan shows DoD/cycle life in some of their documentation. 1900 [email protected]% vs [email protected]% and the curve is flattening (ratio is similar with different product lines). LI does offer more cycles overall. Except, for solar applications, 8000 cycles is 21 years. I'll wager that with daily solar cycling, the battery isn't going to last long enough to make that useful. If you're cycling multiple times per day, sure.
You can get 225Ah x 12V x 1200 cycles (3 years at 50% daily, but much more based on real world reports) FLA for <$400 (Trojan T-105, assuming no core trade-in). Or you can buy a similar capacity Li for $2100 which might last thrice as long. Prices from our sponsors. I just picked a baseline. Scale it up as much as you want, the balance doesn't really change much.
Most comparisons ignore the cost of money. Take that 80% savings of FLA vs Li, invest it (long term inflation adjusted SP500 averages 7%/year), and you'll have enough return to buy a new set every 3 years.
I've tried to use conservative figures, feel free to be more conservative. But it's hard to make a case for Li without extenuating circumstances. Lithium are fine if the requirements for size and weight are important (e.g. vehicles), I can't see much reason to pay the premium otherwise.
I really do not price check alot because I use what is appropriate for the design. On the back of a bar napkin I would write 3 dollars for LI, 2 dollars for AGM, and 1 dollar for flooded.
http://members.sti.net/offgridsolar/
E-mail [email protected]
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Probably the reason you would never have clients also. Please do not quote me anymore!
http://members.sti.net/offgridsolar/
E-mail [email protected]
Just asking a simple question promts a judgmental insulting retort?
Don't judge me by making suggestions I don't know what I'm talking about, you only offered part of a story, so naturally I would not know the whole story, hense the question.
Secondly I don't need clients and certainly wouldn't use a forum to promote myself if I did.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
I am helping JT here not to make a stupid mistake.
http://members.sti.net/offgridsolar/
E-mail [email protected]
They are killed in large power systems when they are comprised of small batteries and the minimum number of batts is not there.
They are charged based on Soc not volts in large systems. XWP is built for this and the gateway can get data from a well designed LFP battery BMS.
If you have insurance on your home, you could lose in a claim if your LFP battery does not have listings. Insurance agents have seen the YouTube of battery fires, even though most of that is NMC lithium. Old flooded/AGM technology gets grandfathered in. LFP does not! You should inquire with your insurance company!
http://members.sti.net/offgridsolar/
E-mail [email protected]
Conversely there are those who don't require the added expense associated with the research and development but rather source equipment based on requirements, it's a personal decision. If one is unwilling, or lacks the ability to construct a DIY system, then perhaps relying on a proven system is a better solution. This doesn't necessarily mean one is inherently better than another if all safeguardsare considered, however I digress.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
|| 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-Lister ,
The BMS monitors individual cell voltages disconnecting charging to the battery as a whole when an individual cells voltage reaches i maximum threshold, cell balance occurs at fully charged state where current flow is almost or at zero. Depending upon the BMS used, this may result in disconnect of the load as well as charging, as in the case of a single port BMS, a dual port type has the ability to individually disconnect one or the other depending on state of charge when the first cell reaches maximum or minimum thresholds.
Since the typical charging profiles used don't venture anywhere near the fully charged state this is generally a non issue but remains there as a safeguard should something go wrong with an individual cell. Programming the load to shut down well above the minimum cell voltage threshold prevents overdischarge, this is important to those using a non programmable inverter which typically have a fixed value tailored to lead acid, which is far too low for lithium, in such cases an auxillary voltage sensing method would be required to shed the load.
Many such concerns about lithium steer users to abandon the choice, once studied however, it becomes clear that these concerns have solutions. Having others do the research and development possibly with a UL listing for insurance purposes along with a warranty, comes at a premium, so perhaps a DIY bank isn't for everyone considering the chemistry.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
To me at this price point it's worth the risk. Downsides-no warantee, literally comes on a slow boat from China-1-2 months, upside cheaper than lead acid, much less maintenance, no damage from partial recharges, ie less gen run time. I'm gonna test the waters with a 272ah 24v bank in my rv first, if it performs well, I'm converting everything.
What's the plan when the battery disconnects ? Does your charge controller become unloaded and float up to your PV array Voc ?
I see no thermal sensors, air gaps and no thermal separators in the pack, everything is all cuddled together, with the cells in the middle, likely 5 degrees warmer than the outer.
|| 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-Lister ,
You make a valid point concerning the alligator clips. They are actually temporary and will soon be replaced. As for the rest, you should know that when you make comments like this, people that have actually built and managed a DIY LFP bank know immediately that you have never built and managed one yourself. And no matter how well read you are, that still makes you an arm chair critic.
Imagine me, living in Florida, telling you what it's like to live in California, even though I've never been there, just listened to what people say, and read about it in a book. You want people to take you seriously about this matter? Make the investment, build the battery, and get some experience. You know what I'm saying is true.
Making this statement is really burdensome to me because I have the utmost respect for you due to your knowledge and long years experience in the field of solar power, not to mention you living off grid. In fact, I have learned a quite lot from your posts over the last 5 or 6 years and I thank you for that.
Rick
I do not like the 4 or 5 times I have been hired to guess what started the fire. Not fun work and none of them were my clients.
http://members.sti.net/offgridsolar/
E-mail [email protected]
Even with NiFe, I log & monitor volts and temps daily. At some point one of the cells is bound to go south and i want all the notice I can get about it.
|| 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-Lister ,
Having ill informed misleading comments constantly being made is frustrating to those who have actual hands experience and are attempting to share information with others who are in the beginning stage. When contemplating LFP I was discouraged at first but discovered through extensive study, along with personal dialog of existing users, that my concerns were easily overcome.
There are those who would rather build a DIY system rather than paying double for a manufactured battery system and or want the challenge of doing so. Even a DIY system could be approved to comply for insurance purposes if inspected by a listed UL preferred partner, if required.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Not sure what exactly you're looking for in term of criteria other than 200A but perhaps they have something to fit your needs, or not, but it's worth inquiring with manufacturers, here is a link http://www.lws-pcm.com/en/produce.asp?Page=6 inquire in the contact us menu, I have no affiliation with the company, just a satisfied customer.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
My guess is that there are others that do the separate charge / discharge disconnect on the same common port. It looks like the newer Chargery BMS (with the solid state relay disconnect rather than the contactor) SSR has separate inputs for the charge and discharge controls from the main BMS, and the documentation sounds like it controls them separately. I.e., the charge can be disabled while the discharge is enabled, or vice versa.
-Bill