I see compressing the batteries between large boards. I wonder if it would help to put some small holes in the boards and perhaps very thin separators between the batteries with slits as well and/or with copper to draw out the heat to keep them cool during use/charging. Maybe CPU type vertical heat-sinks with dual sides for pressure.
Would trying to reduce temps of batteries with cooling per cell extend their life?
From that table, it looks like a fan would greatly increase AMP capacity of at least the bus-bars by 15a. Keeping batteries cooler could only help that also.
I think that you should find a cool spot for the batteries (mine will be in an underground concrete cellar : 15-20°C), I've seen a guy from Australia that was having some hard time with temperatures in his shed. In this kind of case there are solutions, for example what we call in my country "puit provençal ou puit canadien", a ground coupled heat exchanger.I see compressing the batteries between large boards. I wonder if it would help to put some small holes in the boards and perhaps very thin separators between the batteries with slits as well and/or with copper to draw out the heat to keep them cool during use/charging. Maybe CPU type vertical heat-sinks with dual sides for pressure.
Would trying to reduce temps of batteries with cooling per cell extend their life?
I have a similar situation and I will use a temperature sensor so the battery won't charge or discharge if the temperature is too high.This needs to be mounted in my garage which doesn't have A/C and we get outside temps up to 105 in the summer. I'll never be charging at that time however. Is discharging ok during higher temps?
It was found that the temperature combination for charging at +30 °C and discharging at -5 °C led to the highest rate of degradation. On the other hand, the cycling in a temperature range from -20 °C to 15 °C (with various combinations of temperatures of charge and discharge), led to a much lower degradation. Additionally, when the temperature of charge is 15 °C, it was found that the degradation rate is nondependent on the temperature of discharge.
This last paragraph is interestingHere's a study about LifePo4 charge/discharge effects from temp.. but the study was from -40c to 20c !! warmer is better.
Fig. 3. Profiles of tapering current vs. constant-voltage charging time...
Download scientific diagram | Profiles of tapering current vs. constant-voltage charging time at 20, 0, −20 and −40 • C, respectively. from publication: Effects of temperature on charge/discharge behaviors of LiFePO4 cathode for Li-ion batteries | Low temperature performance of LiFePO4 cathode...www.researchgate.net
The Effect of Charging and Discharging Lithium Iron Phosphate-graphite Cells at Different Temperatures on Degradation
The effect of charging and discharging lithium iron phosphate-graphite cells at different temperatures on their degradation is evaluated systematically. The degradation of the cells is assessed by using 10 charging and discharging temperature permutations ...www.ncbi.nlm.nih.gov
It depends on how much current you plan to draw.What awg are you using for your 16cells pack...?
Awg 4....2....? let's say for 3m of cable.
Yea I know, I was curious of what people use and which rate will they use their pack (16s).It depends on how much current you plan to draw.
If you are going to run 1C charge/discharge on a pretty constant basis, its a different answer than if we're talking maybe 0.5C maximum.
I think your math is slightly off. Mine may be a bit on the conservative side but the formula I use is:Yea I know, I was curious of what people use and which rate will they use their pack (16s).
I plan on 0.5C, my inverter is 5kw only and perhaps 1kw on my dc circuit ( connected to the batteries directly) that's a total of 120A max. I was planning on AWG 2.
I think the Riden makes some sense for people who will only use it a few times. If you buy the DC-DC portion of the Riden and a separate meanwell AC-DC PSU one or both components can be repurposed in some way.Hooo what cheap charger can you guys use ...? I will only use it once.... A Riden..? This one could perhaps be off use later...
It's not off, you misread, the 1000w are on the dc circuit ( no inverter) only 5000w are on the ac 220v circuit. (I got 2 circuits in my project, one ac 220v, one dc 48v ( lights, water pump, phone/ pc chargers)I think your math is slightly off. Mine may be a bit on the conservative side but the formula I use is:
[Total Watts] / [Inverter Efficiency] / [Low Voltage Disconnect Voltage]
So for example..
[5000W+1000W] / [0.85] / [48V] = 147A maximum
I think the Riden makes some sense for people who will only use it a few times. If you buy the DC-DC portion of the Riden and a separate meanwell AC-DC PSU one or both components can be repurposed in some way.
Its not low as a generic, conservative ballpark estimate. Many/most people on this forum are using cheap off-brand inverters with efficiencies in the 80's. My approach is to always default to conservative assumptions if I don't know the details.And the 0.85 efficiency is pretty low...
I did consider that but I assumed you would be using a DC-DC converter (48v to 12v). A wrong assumption it seems.It's not off, you misread, the 1000w are on the dc circuit ( no inverter) only 5000w are on the ac 220v circuit. (I got 2 circuits in my project, one ac 220v, one dc 48v ( lights, water pump, phone/ pc chargers)
The 1000w are a large estimation on what I will use on this circuit.Its not low as a generic, conservative ballpark estimate. Many/most people on this forum are using cheap off-brand inverters with efficiencies in the 80's. My approach is to always default to conservative assumptions if I don't know the details.
But yes, if you are using a quality inverter, and they publish an efficiency curve, use that value instead (I would still subtract maybe 5% to be conservative).
Calculate how you will, my broad point is you should account for inefficiency
I did consider that but I assumed you would be using a DC-DC converter (48v to 12v). A wrong assumption it seems.
But even assuming 100% efficiency for DC and 91% for AC
[5000W / 0.91] + 1000W] / 48V = 135A
But regardless of whether we take your calculation or mine, 2AWG seems like it would be reasonable (considering both Ampacity and Voltage drop). 1 or 0 seem reasonable as well.
105*C rated 2 AWG wire (ampacity: 210A at 30*C, 178A at 50*C).
I highly suggest that you look at the electrodacus SBMS0 + DSSR20 w/ Diversion (either to purchase for your system or for ideas on how to implement direct connecting PV to resistive heaters. This pair of products is designed to do what you want to do. I am not sure if it is compatible with your inverter or system though.Did you heard on someone having done a "switcher" based on arduino..? I would like to connect directly some of my PV to my water heater ( I plan on using 3 resistive elements in there, with 3 different power and resistance that match my panels)... Arduino will calculate which resistive elements to switch on/off and it will also reconnect pv to the inverter in case power is needed ( energy going out of the batteries).
I know Dacian, we both got a lot of discussion about is dmppt and how it was kind of unusable for other people then him, system was not flexible to satisfy different situations.I highly suggest that you look at the electrodacus SBMS0 + DSSR20 w/ Diversion (either to purchase for your system or for ideas on how to implement direct connecting PV to resistive heaters. This pair of products is designed to do what you want to do. I am not sure if it is compatible with your inverter or system though.
Well I am excited to see how your arduino based system developsI know Dacian, we both got a lot of discussion about is dmppt and how it was kind of unusable for other people then him, system was not flexible to satisfy different situations.
The dssr is better but sbms only take 8 cells.
In a way my system, on paper, look like the dssr but just not as pro cause I plan on using dssr and Arduino to pilot them, I'm in computer science and not electronic.
I got some ideas but I do not want to reinvent the wheel if someone already did half the job...?Well I am excited to see how your arduino based system develops