Battery charging
Plucka
Registered Users Posts: 130 ✭✭
Comments
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Plucka...what are the charging specs for the battery that you want to charge? That will tell you how many volts you can use. There are AC chargers as well as PV charge controllers made specifically for 12 volt lithium batteries. Lithium batteries have a unique charge regimen vs LA.Off-Grid in Terlingua, TX
5,000 watt array - 14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048NA+, Mini PDP, MPPT 80-600, SCP. 390ah LiFeP04 battery bank - 3 Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries -
My understanding is absorb voltage should be adjustable (for the lithium chemistry and cell configuration used) as should absorb time (typically very short for lithium vs L.A. gel/agm/flooded). A L.A. preset probably isn't ideal.Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter -
Are the settings you are referring to basic selections in a basic controller?
Details of the battery are important, such as if it has a built-in BMS or if it a DIY system.1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS
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. -
Hi everyone Is there a way to connect 6-6volt batteries and maintain 24 v.
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Is the 6-6 v batteries a good idea or not?
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I have an LDSolar 12/24 mppt charger that gives a choice of the 3 battery types and supplier says okay for lithium. but he is shut today.Yes it has a commercial BMS> .This is just too difficult for a 75 year old.Found something.Battery type --sel ---gel-------fld Boost 14.4 14.2 14.6 Float 13.8 13.8 13.8 The rest of the figures are the same for all 3 batteries and the default is Sel
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I don't see how you connect 6 x 6v batteries in a 24v bank. 4 x 6v = 24v bank. 8 x 6v = 2 parallel strings of 24v each. 6 doesn't work for 24v.Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter -
Generally speaking a BMS is designed to protect the battery from overcharge, over discharge and various other parameters which may differ depending om naked or model. The maximum charging voltage for a 12V nominal lifepo4 battery is typically 14.4V or 3.600 volts per cell, or cell block, the 12V will have 4 in series.
For the purpose of off grid, often a lower voltage is utilized to prevent charging to 100%, the intention is to extend lifespan by preventing the cells from stress near the fully charged state. Usually a voltage of ~3.450 to 3.500V per cell (VPC ) is used or 13.8V to 14V for a 12V battery, this is not an issue because the capacity above 3.450 VPC represents a tiny fraction of the overall capacity.
Lithium batteries do not charge like lead acid, there is no absorption stage where current drops as the battery nears full capacity, they accept all available current until terminal voltage is reached. Should there be no way of regulation the voltage would runaway, damaging the cells, this is where the BMS steps in to drop the current as the voltage nears the target value to very low values, otherwise the voltage would climb too fast.
There are differing schools of thought regarding float voltage, or the use of float at all, in applications such as electric vehicles there would be little need for float since the self discharge is negligible. Off grid solar use is different because there generally are loads which would deplete capacity over the course of the day if all charging were terminated, meaning there would be less capacity overnight.
The best values from the ones listed would be the lowest available 14.2V, the unknown however is what determines the transition to float, with more advanced charge controllers this can be programmed, since it appears the LD Solar has no specific lithium setting it may not be compatible, so I would not recommend using something without specific charging algorithms for lifepo4. The manufacturer may claim it will work for the application, but the only way I could see this being the case is if the voltage is set to 14.4V, the BMS terminates charging and the algorithm transitions to float based on current drop, way too much guessing.
The best I can suggest is get a controller that is programmable, lithium batteries need more specific settings than flooded, sealed or gel, this is my opinion, others may differ.1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS
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. -
Plucka, If you are going to invest in lithium do buy a controller with specific lithium settings, any thing else will probably destroy the lithium batteries and you will be burning money...2 Classic 150, 2 Kid, 5 arrays 7.5 kw total 2ea. 2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200, 2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100, 2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
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- The regulator is only suitable for lead acid batteries: OPEN,AGM, GEL
- It is not suited for nickel metal hydride, lithium ions or other batteries Just found this new instruction on their web site.
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Estragon I realize 4x6=24v but can't you hook 4 in series and 2 in parallel?
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DJJ said:Estragon I realize 4x6=24v but can't you hook 4 in series and 2 in parallel?
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.
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DJJ,
I you mean build two series strings of 4x6 batteries for 24 volts, then connecting those 2 strings together in parallel (for 2x more AH capacity) for a total of 8x 6 volt batteries in series/parallel--Yes you can.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
DJJ said:Estragon I realize 4x6=24v but can't you hook 4 in series and 2 in parallel?
You could parallel first, then put the paralleled batteries in series, but then 1/2 of the string is 1/2 capacity vs the other 1/2, so the smaller capacity will be drawn down to a lower relative SOC than the larger. Both the large and small will fail early from under/overcharging. Also bad.
In other words, for 24v you need 4 or 8 x 6v batteries. 6 doesn't work.Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter -
Any word on your battery bank wiring?
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.
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Estragon said:DJJ said:Estragon I realize 4x6=24v but can't you hook 4 in series and 2 in parallel?
You could parallel first, then put the paralleled batteries in series, but then 1/2 of the string is 1/2 capacity vs the other 1/2, so the smaller capacity will be drawn down to a lower relative SOC than the larger. Both the large and small will fail early from under/overcharging. Also bad.
In other words, for 24v you need 4 or 8 x 6v batteries. 6 doesn't work. -
People do have a 24 volt (for example) battery bank, then try to take 12 volts off of 1/2 the battery bank.Don't do it.You end up with 1/2 the bank under charged (where the 12 volts is tapped off), and the other 1/2 over charged.It just does not work well.BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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Thank you for the info, my apologies if it takes me a bit to wrap my head around some of these concepts. I work in an instrumentation/process control/SCADA field and am only a couple years into my career so by no means an expert and have much to learn about electrical systems. I built this little system one piece at a time for that purpose so advice is appreciated.Question-So i cant afford to go out and buy a whole new set of batteries now, so what is my best bet for using these 12 volt batteries? using just 8 of them? I looked em up and they are Duracell Ultra 12v high rate AGM SLA batteries (82ah) my panels are 2x 270wt Renogy (poly) and i have two 100 watt 12v renogy poly panels. As I mentioned a outback flex 60 amp controller and 3000 watt aims inverter. all in an enclosure w breakers and such.. basically what is the best way to set this up for my equip to get the most from it?
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SDCacti,
After I finish this post, I am going to split your discussion into its own thread... It is easier to understand/follow your needs and address them, rather than mixing with the Original Poster (OP) and his questions.
With solar, it works best if you have some "fixed thing" to design around... Generally, the idea is to measure/understand your loads, and then define the battery bank... Then design the solar array to a) charge at 5% to 13% or so rate of charge, and b) to keep up with your loads and hours of sun per day.
However, in this case... You have the battery bank, so we figure out how much energy the bank can produce, and then design the solar array to do 1) and 2).
The first past is just a simple back of the envelope/paper design process. Don't care about "exact hardware" and such until we have the basics down. Once we have a paper design, we can then size/pick/price the hardware that will support your needs.
The neat thing about the paper design is that if something does not meet your needs, it is very quick to reconfigure... Like you start with 8x AGM batteries. If the system does not meet your needs, we adjust (more/fewer/different batteries/etc.). Then we figure out the rest of the system hardware. This is all trying to design and build a "balanced" system (right size battery bank, right size inverter, right size array, etc.).
Battery bank. 8x AGM 12 volt @ 82 AH batteries for a 24 volt battery bank. Note, that will be 2x batteries in series (2x12v= 24 volts) and 4x parallel strings (4x82ah=328 AH). Note--I am not a big fan of paralleling a bunch of small batteries in parallel--I like larger AH rated batteries and fewer parallel strings... 1-2 is probably ideal, and I would try to avoid going over ~3 parallel strings (more wring, more costs, more connections/batteries/cells to fail). But--You have what you have.
All these calculations are starting from a rule of thumb design for a full time off grid system... Anything you have questions about , please ask. Any assumptions/guesses I made that are wrong or different--please change.
Generally suggest 2 days and 50% maximum discharge for battery bank usage (full time off grid/best overall performance)--For emergency and weekend RV/Cabin, using 1 day of storage and 50% max discharge can work.- 24 volts * 328 AH battery bank * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge = 1,673 Watt*Hours per day (2 days of "no-sun")
- 328 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 618 Watt array minimum
- 328 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 1,235 Watt array nominal
- 328 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,606 Watt array "cost effective" maximum
I have no idea where you are at--Let's assume somewhere in Southern California. Fixed array facing south.
http://www.solarelectricityhandbook.com/solar-irradiance.htmlSan Bernardino
Measured in kWh/m2/day onto a solar panel set at a 56° angle:
Average Solar Insolation figures
(For best year-round performance)
In So Cal, there is a lot of sun even in the winter... December is 4.55 hours "average" sun--So if we use that number, you may have to run a genset/conserve power during bad weather in winter:Jan Feb Mar Apr May Jun 4.64
5.02
6.28
6.73
6.70
6.65
Jul Aug Sep Oct Nov Dec 6.43
6.42
6.25
5.77
5.07
4.55
- 1,673 Watt*Hours from battery bank * 1/0.52 off grid AC system efficiency * 1/4.55 hours (Dec) sun = 707 Watt array minimum for "December" break even power
For your system, I would normally recommend 250 to 500 Watt inverter per 100 AH of 24 volt battery bank:- 328 AH * 250 W / 100 AH = 820 Watt AC inverter "nominal"
- 328 AH * 500 W / 100 AH = 1,640 Watt AC inverter "on the large side"
- 1,606 Watt array * 6.65 hours of sun * 0.52 off grid system eff = 5,554 Watt*Hours per day
- 5,554 WH per day - 1,673 WH overnight battery power = 3,881 WH for "day time" loads
The above "brackets" your system based on the present battery bank... And down the road, you could for example, replace the12x AGM batteries with 4 or 8 6 volt @ ~200 AH "golf cart" batteries in series parallel configuration (4x 6 volts = 24 volts; 1 string or 2x parallel strings) and the rest of the system (solar panels, charge controller, AC inverter) would all be the same.
Looking at the above... What works/does not work for you (location, cost of solar panels, more/less battery power than you need, emergency vs "off grid" living, etc.).
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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