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Sean, you said you were getting lithium titanate. they are very expensive, but are claimed to have a long life 50 years.
the LiFePO4 batteries are relatively cheap if one does diy with a bms
and have a 3000 to 5000 cycle lifespan an then will maybe have 80 percent capacity. 5000/365=13.69 years for LiFePO4 chemistry.
in 13 years the battery storage chemistry may have an even better chemistry. i was hoping for the salt water battery that was once talked about.
lead acid is old school --- lead weights for sure.
I think I kinda convinced him otherwise after running some math...LTO is a great, safe technology. But if you put dollar signs next to capacity, he could get over 8 times the capacity with LiFePo4...for the same cost. Or replace a same-sized LiFePo4 bank 8 times for the same cost as the same sized LTO bank. Just simply not economical yet 😉.
yes i bought 64 272Ah Lishen cells delivered to me for an average of $92.50 per cell in South Dakota. i have 2 2P8S batteries up and cycling so 272Ah X 16cells x3.2V per cell = 13,926.4 watt hour potential capacity and they are said to do 285Ah or more per cell. right now i think the LIFePO4 is the best way to go Bang for the buck! in 13 years - a new improved technology will likely arrive for even better lifespans. also the LiFePO4 is not dead after 5000 cycles it just may have reduced storage capacity say 80 percent.. as long as they arer treated right. (dont freeze them and charge while frozen - that will damage them). i have mine in a insulated off-grid solar power shed that is heated by one incandescent light bulb and it was still a balmy 57 degrees Fahrenheit when it was 25 below zero last week.
cheers all 😎
Boy did you get a steal of a deal on those cells...and you have 64 of 'em?? Goodness gracious, it's about time you got a real inverter to go with those cells 😉
I spent roughly $1,200 on my LiFePo4 bank plus several days of work putting some 700 32650 cells together...I have right about 12kwh of capacity, which works out to $100/kwh.
16 Lishens cost basically $1,500 and provide 14kwh capacity = $107/kwh. Boy you did really good! Are these new cells?
If you're starting out with a mega system like that (i.e. 55kwh), I would STRONGLY recommend you consider running 48v (16S)...in the end, it will cost you a lot less. You get double the wattage out of an MPPT with 48v over 24v, meaning that you need half as many MPPTs for the same solar array.
I started out at 48v after I sat down and did some math...finding that the $600 Morningstar Tristar MPPT could only do 1.5kw at 24v, but it could do 3kw at 48v (due to the 60A limit). I was set on a 3kw system, so that meant that if I went for a 24v battery, I'd have to buy 2 MPPTs...at $1,200. Not to mention needing to buy (more expensive) heavier gauge wire. That's why I went 48v.
The only "minus" for 48v is that finding properly rated DC breakers gets a bit harder. And if you want to run things directly off of DC, there's not much out there for 48v.
Any more cells where those came from??
Re: DC Breakers
Standard Square D single and double pole QO breakers up to 70 amps are rated for 48 VDC, and their large frame molded case breakers like the LF and LA are rated at 250 VDC. Lots of companies are happy to slap a DC label on something and jack up the price, but if you dig down in the literature, a lot of the standard hardware store AC stuff has been tested at DC voltages.
Re: DC Breakers
Good call. Might want to coat the breaker terminals with Vaseline (or whatever the proper product is)...don't want corrosion in your breaker panel. Or anything DC for that matter. I've coated all DC connections with Vaseline on my system, and there isn't a dime's worth of corrosion to be found. Maybe that's just for lead-acid batteries...I dunno, I guess I might have overdesigned that one!
For cooler areas of the US one thing I can add to this is to save some cash on LTO if that is reason you wanted it like me. I use some AGM batteries for a combo setup with LifePo4. This a belt and suspender type approach but if you need to warm up the LiFePo4 and the BMS shut it off you have a way to run a 100 Watt heating pad. That is my work around so I can use the LiFePo4 batteries in the winter. This is also very helpful when it comes time to start up the generator and charge them up fast even if you keep it warm inside they charge way slower when colder acting like old school lead acid taking many hours. I like to cycle my generator on for as short of a time as possible. So I used the timer cord from a 12V heating blanket and swapped in a 12V silicone heating pad under the battery kick that on about an hour before charging.
I am working on an automation process for this but, worked like a charm this last winter flipping the switches manually.
3 hours ago, AquaticsLive said:This a belt and suspender type approach but if you need to warm up the LiFePo4 and the BMS shut it off you have a way to run a 100 Watt heating pad. That is my work around so I can use the LiFePo4 batteries in the winter.
My way of handling this? Put a 120v waterbed heater underneath the batteries, and use a cheap eBay temperature controller connected to a properly rated DC SSR...and have the temperature controller basically connect the waterbed heater across the solar panels. Add some software to shut the Morningstar Tristar MPPT off if the batteries are too cold, and...well...!
Of course, for charging via a generator, your way is a lot better.
My way of handling this? Put a 120v waterbed heater underneath the batteries, and use a cheap eBay temperature controller connected to a properly rated DC SSR...and have the temperature controller basically connect the waterbed heater across the solar panels. Add some software to shut the Morningstar Tristar MPPT off if the batteries are too cold, and...well...!
Ahh that just gave me an idea. I am using the EPever charge controllers with RS485 so think I may just use a set of the load terminals from it to run the heater. I have it setup using the RS485 commands display the solar information so easy to turn the load on and off via commands too. I just need to get busy writing the code, not using those terminals for anything so might as well use them to add some smarts to my manual process.
Have you found a way to shut off the Epever MPPTs via RS-485? I didn't see anything of that nature in the rather generic EPEver '485 document.
Have you found a way to shut off the Epever MPPTs via RS-485? I didn't see anything of that nature in the rather generic EPEver '485 document.
The load is controlled via the coil commands, but the charging there aren't any documents that I have found either. I have a Shallco magnetic contact relay for the charging disconnect. Awesome contractors if your looking for something that has zero power wasted.
The EPever load command is something like this though using the C++ libraries I am using ESP boards for all of this since they are so cheap.
#include <ModbusMaster.h>
ModbusMaster node;
node.begin(1, Serial);
void LoadOn(){
result = node.writeSingleCoil(0x0006, 1); //On
Serial.println(result);
}
void LoadOff(){
result = node.writeSingleCoil(0x0006, 0); //Off
Serial.println(result);
}
Epever's modbus commands - http://www.solar-elektro.cz/data/dokumenty/1733_modbus_protocol.pdf
I looked into it a while ago and couldn't find any way to turn the charger off. As far as I can see the only way to stop current flowing is to reduce the charger's target voltage to be lower than the present battery voltage.