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    Panel and Wiring Setup for 40' Catamaran

    If you can avoid it, you shouldn't mix different panels on the same controller. Especially if they are very different. I would use 3 controllers. I would put the 2 165W panels on one controller, and 2 380W panels on each of the other 2. I would likely connect the panels in series. The panels are...
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    What is my correct SOC? BMS ok?

    You need a complete cycle or 3 for the BMS to read accurately. So, you need to accomplish that before looking for any other issues. Small voltage differences can be caused by voltage drop (use larger wires to reduce that) or poor connections.
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    Building the sickest ® VAWT ever. Brilliant minds unite please!!

    You cannot get more energy out of the alternator than you put into it. So, while you might be able to build an alternator that produces more power at 60RPM, the amount of wind energy you put into the alternator to get a given wattage will be about the same. You will just need to reach that...
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    18000lbs yacht elec inboard system

    For propulsion, you definitely want to build a battery from cells, not use premade drop ins. You also should look at a BMS system like the REC-BMS instead of a simple FET based BMS. You *could* meet the requirements with FET based systems, but for propulsion I just wouldn't do it. Have you...
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    New battery/inverter-charger/solar setup questions for a sailboat

    You really need to sketch out how you want to wire this up, as there are several ways that will work well, and other ways that will not work well. So, sketch your ideas and most them. I also recommend working up an energy budget. I have enough solar to run a fridge, a freezer, watch a couple...
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    Charging options for boat Lithium house bank and AGM engine bank

    Sorry about my negligence. I was responding to the post directly above mine, you are right I should have quoted it. We agree. This a common approach I support. A common trend though, is that someone gets an idea "LFP is awesome, let's get rid of all the LA batteries and make them all LFP."...
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    Charging options for boat Lithium house bank and AGM engine bank

    Well, first, the question was about replacing an AGM starting battery with a 100Ah drop in, not building a bank capable of starting an engine. Even so, using 12 280Ah cells, plus a BMS capable of 750-1000A, is a really expensive alternative to a $150 AGM. Yes, it will work, though. But holy cow...
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    Cat Owner - Too Many Batteries? Plz Brainstorm With Me

    The first thing you need to do is calculate how much power that A/C unit will use. How many hours will you use it? Then you can size your solar and battery. If you want to run it 24/7, you will probably need 2000Ah of battery, and about 5000W of solar. If you only need it 8 hours per day, then...
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    What Can I personally do to help against climate change?

    There are various sites that will help you estimate you carbon footprint and give you some ideas how to reduce it. I was a little (not a lot) surprised when I did mine a while back. I live on a sailboat. I walk to work. It has been more than 6 months since I bought any petroleum fuel (lpg for...
  10. W

    LIFePo4 UPS and BMS

    The BMS will disconnect charging, without disconnecting discharge. So power will always be available. I expect that could work. An interesting project, but probably more complicated than you expect. The APC (at least the ones I have been responsible for) monitors the battery voltage to...
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    Charging options for boat Lithium house bank and AGM engine bank

    LiFePO4 is not a good battery for starting, for a variety of reasons. Starting is high current, but low discharge. In other words, you may need a 750CCA staring battery, but it only needs to be about 25Ah. Starting batteries basically sit fully charged until you need them, and that will shorten...
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    Electrodacus vs Overkill/JBD BMS

    Need more information about the application. Voltage/current requirements, solar, etc. Despite the horror stories, most of them are just stories. FETs are very reliable and used in almost every electronic device made. I have not looked at the Electrodacus circuit diagram, but it absolutely uses...
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    Victron/Amazon shipping

    That box is pretty torn up, but consider that the box's purpose is to protect what is in it. A damaged box isn't by itself a reason to return an item. If the item doesn't work, the box could be a clue to why, but otherwise it simply did it's job.
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    What's the formula to calculate Columbic efficiency for LFP cell / battery pack both for chg and dchg?

    12 Months is a long time. For that you would also need to account for self discharge, which is non-zero even for Lithium, and will vary from cell to cell, and vary over time. Accurate is subjective. I would consider an SOC meter accurate if it will go a week and still be within 3%. Many(most?)...
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    I know using multiple power supplies is safe, but what if??????

    The original question was if multiple power supplies could be used to charge a battery if they were different amperages. :unsure:
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    I know using multiple power supplies is safe, but what if??????

    Ooooo. I might pick one of those up!
  17. W

    I know using multiple power supplies is safe, but what if??????

    He was going to use cheap 10A voltage boosters, hoping for a total of around 80A. Which *might* work with 1200W. But I highly advise against it.
  18. W

    I know using multiple power supplies is safe, but what if??????

    8 12V rails, each supporting 30A would be 2880W. The math doesn't add up. The only way that power supply can be 1200W is if the 12V outputs share a supply. They can not all be 30A. Simple math. It *might* be possible to get 10A from all of them like you propose, but don't count on it. Lifepo4...
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    What's the formula to calculate Columbic efficiency for LFP cell / battery pack both for chg and dchg?

    Yes, for LFP you can ignore temperatures affect on eff. Many also ignore eff and Peurkert, although that will cause a measurable(but small) inaccuracy with the meter. Most meters will resync to 100% after a full charge. So if it reaches full charge everyday, and gets off by <5% during the day...
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    Gas-Powered Lawn Equipment Will Soon Be Banned In Cali, a broad category that includes generators.

    I am not sure about 2020, but certainly 19 years ago, and I suspect in 2020, there was no shortage of generation. It was caused by legal/political/contractual issues with buying power and importing it from other states. The power was there to be delivered, but California couldn't buy it...
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    Gas-Powered Lawn Equipment Will Soon Be Banned In Cali, a broad category that includes generators.

    The law seems to only apply to spark ignition engines. You could still use a diesel powered ride on mower. Or any mower with greater than 25hp, which if you have several acers you should consider. Actually, you should consider getting rid of your lawn, California is in a drought. FWIW, my family...
  22. W

    What's the formula to calculate Columbic efficiency for LFP cell / battery pack both for chg and dchg?

    It means that as temperature changes, the efficiency of the battery does not change. With other chemistries (lead acid) as the temperature gets warmer the battery is less efficient. Efficiency would be given at a certain temperature (ex 95% @ 70 degrees) and the temp compensation (ex 0.4) would...
  23. W

    Ammeters and diodes

    You are correct, of course. (embarrassed)
  24. W

    I know using multiple power supplies is safe, but what if??????

    I will ask again separately in case it got lost. What is the wattage of the supply?
  25. W

    I know using multiple power supplies is safe, but what if??????

    Some others have used ATX power supplies. I don't recommend it, but it seems to work. As to your configuration, I would be very surprised if you can get 80A out of the power supply. Does the PS have a total Wattage rating? What I expect is that individually any single rail can supply 30A, but...
  26. W

    Question on charging LiFePO4 to 90% SOC with a charger in an RV

    Full charge is ~3.4V per cell. Charging at a higher voltage will get you to a full charge a little bit faster, but after you stop charging and let the battery rest for 24 hours, it will settle to 3.4V. If you charge at 3.4V, you will fully charge the battery, but as you get close to 3.4V per...
  27. W

    Question on charging LiFePO4 to 90% SOC with a charger in an RV

    Short answer, get a different charger. Longer answer, a charger with a custom setting will allow you to set the bulk voltage lower, to what will be about 90%, which is probably about 13.6V. You would then set absorb or float to something lower than that (maybe 12.8) so charging will stop. As...
  28. W

    I know using multiple power supplies is safe, but what if??????

    He is describing a different situation, not one in which you are charging batteries, but one where you are using multiple supplies to supply a constant voltage to a load. In the case where you have multiple supplies and each one on its own is large enough to support the entire load, then they...
  29. W

    What's the formula to calculate Columbic efficiency for LFP cell / battery pack both for chg and dchg?

    It is *NOT* non-existent. It is around 1.03-1.05 It is often ignored, but it is still there, and some Lifepo4 manufactures will provide a number to program into a meter. Note this spec sheet from Lithionics. Charge eff. 98%, Temp comp 0%, Peurkert 1.05...
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    I know using multiple power supplies is safe, but what if??????

    It's fine. They don't even need to be the exact same voltage. It is quite common (yes I have done it often) to charge from an AC charger, an MPPT solar charger, and an alternator, all at the same time. All different amperage and voltages. What happens is that once connected together all the...
  31. W

    What's the formula to calculate Columbic efficiency for LFP cell / battery pack both for chg and dchg?

    <snip> There are 3 commonly used factors in Coloumb counting. Efficiency, Temperature compensation, and Peukert exponent. Temperature compensation is by how much efficiency changes with temperature, and Peukert how much capacity changes with rate of discharge. At higher rates of discharge, the...
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    Ammeters and diodes

    If you cannot separate the load and charge, and need to use diodes it gets much more complicated. As stated before, you need an amplifier before the diode to overcome the forward voltage drop of the diode, then after the diode you need a resistor network to calibrate the meter for the increased...
  33. W

    Ammeters and diodes

    Ok, excuse my notepad scribbles. This is the first drawing, simply by separating the load and charge as suggested is very easy and works without diodes.
  34. W

    Will Prowse CALLED OUT by Andy's Garage !

    I have to declare alcohol abuse. It is much more desirable to sacrifice green beans than a beer.
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