February 10, 20233 yr 4 hours ago, deonholt said: Both are new. I moved from a 24V to a 48V inverter. Supplier doesn't have same brand in stock of the 24V system. Both are lead acid & both 180ah. I understand this means means you are adding 2 new 12V batteries (to provide 24V) in series with 2 older 12V batteries (providing the original 24V) to get a 48V battery pack. How old are the original batteries that provided the 24V system? As with any lead acid battery it isn't recommended to add to the pack when the batteries are more than X months old - X is 6 months or a year depending on who you talk to.
February 10, 20233 yr 3 minutes ago, TaliaB said: I agree with P1000. Contrary to what many think, the BMS does not change the charge or discharge current, it really is just an on-off switch; if you have a charging source that can push hundreds of Amps into the battery the BMS will sense this, and switch the battery off when the upper safe limit is reached! You are talking about the protection feature of the BMS, yes it does, that is one of the benefits, and its called Over current protection. It will cut off in the case where you draw too much from the battery or in case where there is a fault in a battery causing it to demand more than the rated charge current. Your inverter will never supply more than what has been demanded and your BMS or let me say, your battery will demand what it has been set for. It will never demand more than that, under normal conditions. Other wise my battery bank would have been toasted three years ago
February 10, 20233 yr Example here ... Battery BMS limits charge current to 20A and discharging current to 100A. You have com between inverter & BMS here. If you disconnect the com cable, battery will still only charge at max 20A or discharge at max 100A. Really, you should try
February 10, 20233 yr Guys can we please look at what the OP said. He is talking of lead acid and no lead acid has a BMS fitted as far as I know??????
February 10, 20233 yr Due to the problem with BMS comms between Axpert and Pylontech I ran a test on a Pylontech US2000C battery. I was concerned about over charging as the RS485 BMS reports the maximum charge current to the inverter and the inverter progressively reduces its maximum charge current setting automatically based on the values coming from the BMS. My concern was that setting USE for battery type, and then voltage, it would not be sufficient and that the batteries would continue to charge. The result was that as the battery approached 100% it automatically reduced the charge rate without any intervention. My conclusion was that the USE settings are fine and overcharging will not happen. Edited February 10, 20233 yr by Acuario
February 10, 20233 yr On 2023/02/09 at 12:16 PM, deonholt said: I forgot to mention: The question is with regards to lead-acid batteries. It has the same 180AH rating, both 12V & both lead-acid. Can I use them together in series? @deonholtstated his question quite clearly and now we have a discussion on different chemistry. Maybe start a new thread to discuss the theory of mixed Lithium batteries as the direction of this thread is now outside the scope of the OP's query.
February 10, 20233 yr 1 hour ago, zsde said: @deonholtstated his question quite clearly and now we have a discussion on different chemistry. Maybe start a new thread to discuss the theory of mixed Lithium batteries as the direction of this thread is now outside the scope of the OP's query. It seems memories are fading quite quick on what a lead acid battery is. 🤔🤔
February 10, 20233 yr 3 hours ago, Scorp007 said: Guys can we please look at what the OP said. He is talking of lead acid and no lead acid has a BMS fitted as far as I know?????? However, it is important to note that the batteries should be of the same type (i.e. lead acid, lithium-ion, etc.) and that they should be charged and discharged at the same rate to ensure proper performance His question is not only about lead acid. If you read through the chain you will see that the lead acid part has been answered. In any case, the OP hasn't complained about a chat on BMS
February 13, 20233 yr Author On 2023/02/10 at 3:01 PM, Acuario said: I understand this means means you are adding 2 new 12V batteries (to provide 24V) in series with 2 older 12V batteries (providing the original 24V) to get a 48V battery pack. How old are the original batteries that provided the 24V system? As with any lead acid battery it isn't recommended to add to the pack when the batteries are more than X months old - X is 6 months or a year depending on who you talk to. 2 months.
February 14, 20233 yr 21 hours ago, deonholt said: 2 months. Then they should be ok as they are nearly new, it's unlikely you'll notice anything unless the old(er) batteries have been seriously abused.
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