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Thread: Selecting a solar lithium battery

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    Selecting a solar lithium battery

    It seems once again, no apples with apples comparisons, only apples with oranges and pears with grapes.

    What are the key factor to consider.

    The battery capacity in amp/hr and KWh

    Cycle life @ the C rating.

    The normal and max charge/discharge current.

    The type of cells being used in the battery.

    The communication with the inverter.

    How many you can connect in parallel.

    Working temperature.

    The warranty.

    Very very important, the support and availability.

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    The C rating of the battery, which is better?

    Hubble

    New Li-ion Prismatic Cells

    3000 Cycles @ 100% DOD, Above 6000 cycles @ 50% DOD

    New Li-ion Prismatic Cells

    Or

    Sunsynk

    LiFePO4,Lithium Iron Phosphate

    6000 Cycles @ 80% DOD / 25C / 0.5C, 60% EOL

    So if you increase the Sunsynk to 1C then it would only offer 300 cycles, it would be the same specs?

    I am trying to understand which would be a better buy, they are both the same price, Hubble a little more expensive.

    If it were the support, the company I am dealing with for the Sunsynk would be my choice.

    It seems they both have the same cells, the communication is better between the Sunsynk inverter and the Sunsynk battery and I hear if I use the Sunsynk battery with the Sunsynk inverter there could be a better warranty period on both products.

    DO you have any other suggestions or comments with regards to selecting a battery for the Sunsynk inverter.

    Some say the Deye and Sunsynk are the same inverter out the same factory, unfortunately I will only be able to comment on that once I have the inverter and battery setup on my work bench.

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    The next question -

    3000 Cycles @ 100% DOD, Above 6000 cycles @ 50% DOD

    6000 Cycles @ 80% DOD / 25C / 0.5C, 60% EOL

    Lets try get an apples for apples comparison @ 25degreesC :

    If both batteries had 3000 cycles @ 100 % DOD, what would be the C rating of the Sunsynk battery?

    IF both batteries had 6000 cycles A 80% DOD what would be the C rating of the Hubble battery?

    If both batteries had 6000 cycles @ 100% DOD what would the EOL % value be?


    What makes the one battery better than the other, taking into consideration that we are going to be installing Sunsynk inverters for our customers.

    The shape of the cells, hubble indicates the use of prismatic cells? I would need to find out the shape of the Sunsynk cell, I would think by now they are also using prismatic cells.

    The capacity of the individual cells? Could the Hubble battery be using a higher amp/hr cell or more cells to give it a 1C rating and +/- 16 year design life?

    Would that indicate that the Sunsynk has a 30 year design life @ 6000 cycles?

    The communication between the inverter and the battery and the software for the monitoring?

    The make of the cells, Hubble indicate they using BYD ? I somewhere that Sunsynk are using a rebranded BYD battery, I would need to verify this statement.

    Just so many questions. I am glad I am at that point where people cant baffle me with all the bullshyte I hear or read. So many experts in this field, trying to find that person who has a little more knowledge than the general ramble, can prove to be a challenge.







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    Very difficult to compare batteries, as each supplier cherry picks the specifications they wish to hand to customers.

    The 'C' rating refers to the charge value/capacity for reliable battery life.
    Charging Lithium at 1C, will require careful monitoring of cell temperature, and reducing current(C) as the temperature rises.
    Un-monitored battery temperature would recommend a below 0.5C
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za

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    Been doing more research into batteries today.

    I still cannot find what makes one 5 kwh lithium battery better than another brand.

    It seems that all batteries are capable of 1C, it just cuts the life span in half.

    So if a battery offers 1C capabilities, you will notice it only has a 3000 cycle life span.

    So the battery offering 0.5C will have a 6000 cycle life span.

    Prismatic cells are not a selling point, like BYD cells used by most reputable brands to build their batteries using prismatic cells.

    I am at the point were I believe it boils down to the compatibility of the battery to the inverter. Using a Sunsynk battery with a Sunsynk inverter just makes more sense. I am sure the Sunsynk is rebranded battery spec'd to work with the inverter.

    There is a R2000 difference and something else to consider is the delivery cost and courier fees if the battery fails. It starts adding up. Where you source these products could make or break the sale.

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    Looking at the spec sheet of the Sunsynk battery, it has a normal charge/discharge rate of 50 amps and a max charge discharge rate of 100 amps. How often would you require your battery to charge or discharge your battery at the max 100 amps? As mentioned then we have the temperature to consider, the quickest way to kill any battery is heat.

    Something else to consider, it's gona give you less than 1 hour of backup, so I would say a really badly spec'd system would require a 1C battery.

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    How do companies determine the C rating of their batteries.

    The capacity of each cell?

    The physical size of the cell?

    The number of cells in the battery?

    The BMS firmware?

    Maybe the 1 C battery has cooling fans and the 0.5C battery not?

    If the battery is rated at 100 amp/hr battery, using prismatic cells and the same type of cells (BYD).

    What am I missing?

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    Batteries usually do not have any fans, so battery assembly probably plays a role in the temperature build up with in the pack during charging/discharging.
    Majority of battery packs are made up of the 18650 single cell.
    They come in a variety of ampere capacity.
    By placing many in parallel, will give the battery ampere capacity in Amps. Then by placing a number of these packs in series, will give you the voltage of the battery pack. The BMS is then wired to each bank of parallel packs to ensure that the pack gets the correct current to match the full pack.
    The Tesla battery packs have water ways between the cells, which are kept at a constant temperature with a cooling liquid, and hence the reason they can be quickly charged as the individual cells are cooled down.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za

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    How do you achieve 1C rating, by using more cells in parallel and derating the battery to as lower kwh rating or installing systems like heat sinks or a radiator systems ?

    Are prismatic cells made up of 18650 cells?

    I heard something interesting on the weekend, if you are selling lithium batteries and using "seconds" would you be required to advertise that your batteries are sold as "used " or could you still sell them as newly built or some other lingo to dodge the fact that your cells are not 1 st generation or off the production line ?

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    Diamond Member Justloadit's Avatar
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    Quote Originally Posted by Isetech View Post
    How do you achieve 1C rating, by using more cells in parallel and derating the battery to as lower kwh rating or installing systems like heat sinks or a radiator systems ?
    the 1C refers to the battery capacity. Adding more cells in parallel basically increases the value in amperes of the battery capacity. Using the terminology of 'C' makes the statement universal to any battery, where you would multiply the 'C' by the battery capacity in Amperes

    Quote Originally Posted by Isetech View Post
    Are prismatic cells made up of 18650 cells?
    Not necessarily.
    A prismatic lithium battery, features a cell that has been encased in either aluminum or steel, mainly for the purposes of increased stability.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za

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