I have a lead acid battery setup which has 3x12V 12Ah batteries connected in series resulting in 36V 12Ah output. I also have 3 LIPO batteries (1x11.1V 3300mAh, 1x11.1V 3000mAh and 1x12.6V 4500mAh). Is it possible to connect them together as below to attain 16Ah output current of the setup?

If not, is it possible to connect 4500mAh battery to connect with one of the Lead acid battery in parallel to increase the output current of the setup?

Multiple Batteries connected together

  • \$\begingroup\$ 16 Ah is not an output current. Apart from that it’s theoretically possible but definitely not recommended due to charging and balancing issues. \$\endgroup\$ – winny Aug 24 '19 at 10:26
  • \$\begingroup\$ What would be the output current? Is there any better way to connect them together such that it increases the overall Amperes of the setup? \$\endgroup\$ – azad.parinda Aug 24 '19 at 11:03
  • \$\begingroup\$ YOUR LIPO BATTERIES ARE all 3.7V cells. | 3.7V is the average voltage. 4.2V is the abs max voltage at full charge. 3 x 3.7 = 11.1 . 3 x 4.2 = 12.6. | DIFFERENT PEOPLE HAVE WRITTEN THE SPECS. | \$\endgroup\$ – Russell McMahon Aug 24 '19 at 12:54
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    \$\begingroup\$ TELL US WHAT YOU ARE TRYING TO ACHIEVE AND WHY - NIT how YOU WISH TO DO IT. | Ah is current CAPACITY not current. You need bttery specs to know allowed current. Adding 25% to current capacity may not make much difference. | What? Why ? What what what ? :-) \$\endgroup\$ – Russell McMahon Aug 24 '19 at 12:57
  • \$\begingroup\$ Zero if you don’t load it. Plenty of current if you short it. Anywhere in between for your application. \$\endgroup\$ – winny Aug 24 '19 at 13:50

It is possible, but strongly not recommended unless you really understand the risks, and you would not be getting the total amount of charge out of either battery chemistry,

The lead acid battery has a charge range of about 10.8V flat to 13.2V full, depleting the battery over this range is what is required to extract its rated amp hours (at a discharge rate that is specified on the battery),

The lithium battery will be a string of 3 batteries, generally with a maximum of 4.05V each, or about 12.15V maximum (the 11.1V ones are just marked to the "nominal" voltage, they would be the same), the lithium batteries would have a charge range of about 8.1V flat to 12.1V full,

This means that for the lead acid as you cannot charge it higher than the 12.1V of the lithium you loose about half of there capacity, equally below about 10.8V, the lithium batteries are doing all the work, as the lead acid's equivalent series resistance begins to skyrocket

If you still wish to go ahead with this, and seriously, never in a situation that may charge it, first make sure all the batteries are as close in voltage as possible before connecting them, e.g. the last decimal place on your multimeter, as any difference in voltage when you connect them in parrellel will result in current flowing, which if too high may damage the lithium batteries, Current = Voltage / Resistance, and when you have nice thick wire between them, half a volt difference may be hundreds of amps,

Next up, discharging, your 3300mAh lipo's will start discharging faster than your 4600mAh lipo, this can be dangerous, much safer would be with matched capacities, or some kind of balancer to make sure the 4600 never gets pulled to a higher voltage as the other 2 drop off towards empty,

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  • \$\begingroup\$ Would it make any difference if I charge the lead acid pack and LIPO pack separately while discharging them collectively? \$\endgroup\$ – azad.parinda Aug 24 '19 at 11:02
  • \$\begingroup\$ You can do that, the same issue with the mismatched capacities apply for the discharge, but if you split each lithium and recharge it seperatly, not in a series string (unless it has a balancer for every cell), you will be OK, \$\endgroup\$ – Reroute Aug 24 '19 at 11:06
  • \$\begingroup\$ Would it improve the overall current capacity of the setup (i.e. >12Ah)? Would the difference in voltage between the Lead acid and LIPO pack when connected in parallel a serious issue? \$\endgroup\$ – azad.parinda Aug 24 '19 at 11:35
  • \$\begingroup\$ Capacity wise it would reduce your usable capacity, you go from 36V 12Ah for the lead acid to 36V ~5.6Ah for the lead acid, + 36V ~3.3Ah for the lithium, so you end up loosing about 3Ah in total, As for difference in voltage, yes a problem, very big problem, lets say you have a half volt difference, that may be 100+ amps as it equalises, which in turn becomes 3.6KW+ across your batteries for as long as it takes, things will get hot, and lithium batteries may explode under these conditions \$\endgroup\$ – Reroute Aug 24 '19 at 11:39

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