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I have added an electric motor kit to a recumbent trike. I'm using SLA batteries with a lithium ion 36v controller. Therefore the controller cuts out before the batteries are dead. I'm using 3 each 12v 10Ah batteries in series. I have added a 6v 5Ah in series for a 42 Volt battery. Now the system dies after 6 to 7 miles, compared to 17+ miles before. Would adding another 6v 5Ah battery in parallel to the other 6v 5Ah battery making a 6v 10Ah work? 12v 10Ah + 12v 10Ah + 12v 10Ah + 6v 10Ah in series = 42v 10Ah battery.

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Yes - all batteries in a series-connected bank must have the same Ampere-hour rating, as all batteries are supplying the same current, regardless of their voltage.

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  • \$\begingroup\$ Thank you, I will add 2nd 6v 5Ah battery in parallel to 1st 6v. \$\endgroup\$ – A A Nov 25 '14 at 14:06
  • \$\begingroup\$ @AA You may have already completely destroyed the first 6V 5 Ah battery by discharging in series with higher capacity cells. While you are experimenting like this, make sure you carry a fire extinguisher and be prepared to rapidly exit the trike. Use adequate fuses to avoid catastrophe. Please note that when you parallel larger batteries like this, they may equalize by having very large currents flow from the higher voltage cell to the lower voltage cell. If you can put them in parallel at a time when their voltages are fairly close, this should minimize the effect. \$\endgroup\$ – mkeith Nov 25 '14 at 16:37

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