I have a scenario of connecting three batteries together. Two are 12V 80 AH and one is 12V 150AH . All are C20. I wish to make it a 24V system of 150AH by connecting the two 80AHs in parallel which will be connected in serial to the 150AH. All are more than five year old so reduction of age is not a problem. I am worried about technical issues like reverse charging. Many sites says that it should not be made as it will lead to fire, explossion, etc. But I think since there is only a difference of 10AH it will work. What is your views ? BTW, the batteries will be charged from a 24V 1040W solar panel. Thanks in advance

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    \$\begingroup\$ Always use the same batteries. Do not mix them. \$\endgroup\$ – Atizs Apr 3 at 11:33
  • \$\begingroup\$ So two main problems. The two in parallel could have different potentials so the higher will attempt to charge the lower, High currents will flow between batteries causing a fire, explosion. Higher capacity in series may cause lower capacity to be used up first. So, please don't! \$\endgroup\$ – StainlessSteelRat Apr 3 at 13:18
  • \$\begingroup\$ I am a newbie, so forgive me if my idea found to be silly. I understand that batteries in parallel should hane same voltage and that are in series mustl have same capacity. So I presume that the two 80 AH ones will maintain their voltage. When combined, they will become one 160AH 12V battery. It is to this battery I connecting the 150AH in series. So my understanding is that the difference in capacity is only 10 AH. (6,6%). This small difference is serious enough to cause fire / explosion or any accident as indicated ? \$\endgroup\$ – Raju VK Apr 3 at 15:24

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