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I was wondering if it's possible to avoid buying a $400 48V 15Ah battery with an output of 54.6V and 2A, and instead make one by joining multiple 3.7V 5Ah batteries in series and or in parallel? Is a conversion like this even possible with the batteries I have? If not, what batteries would I need?

(The desired voltage and amperage don't have to be exact.)

Thank you for any help or advice you can offer.

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closed as off-topic by Chris Stratton, Dmitry Grigoryev, winny, Maple, Lior Bilia Aug 25 '18 at 18:48

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Chris Stratton, Dmitry Grigoryev, winny, Maple, Lior Bilia
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    \$\begingroup\$ Also the $400 battery is made with joined batteries. \$\endgroup\$ – Marko Buršič Aug 23 '18 at 16:02
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    \$\begingroup\$ yes, but you might actually spend more money if you DIY and use 75+ decent cells. \$\endgroup\$ – dandavis Aug 23 '18 at 16:03
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    \$\begingroup\$ You would need a minimum of 39 of the 3.7 V 5 Ah batteries to do this. Are they less than $10 each? \$\endgroup\$ – Matt Aug 23 '18 at 16:04
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    \$\begingroup\$ A former coworker has been attempting this. He bought a battery spot welder to connect the batteries together in strings, otherwise I don't think putting strings of batteries in a holder makes for very good connections over the distance of a string. \$\endgroup\$ – CrossRoads Aug 23 '18 at 16:10
  • \$\begingroup\$ @Matt, The batteries I had in mind are 10 for $11.16 on aliexpress, so the over all cost would be about $40. If I used 39 of the batteries, would I create groups of three cells joined in parallel and then join 13 of those groups in series? \$\endgroup\$ – johnnyb1970 Aug 23 '18 at 18:05
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I was wondering if it's possible to avoid buying a $400 48V 15Ah battery with an output of 54.6V and 2A, and instead make one by joining multiple 3.7V 5Ah batteries in series and or in parallel?

Yes, this is definitely possible, but lithium ion batteries used in series arrangements require extra provisions for safety, including cell matching, where cells are tested in large quantity and binned for their properties, and only used with other brand new cells with matching properties. This can allow for the simplest charger arrangements. Individual cell monitoring and galvanic isolation can be used as well.

Is a conversion like this even possible with the batteries I have? If not, what batteries would I need?

If you have brand new cells you can test them to see how well matched they are. If you don't have a sufficient quantity you may wish to order the full number to avoid matching problems with your existing ones, or look for "13s3p batteries" on the google to find pre matched and connected sets for diy purposes. If you do decide to build your own, be sure to use a charger and battery protection that suit the purpose, and don't neglect the option of refurbishing an existing battery pack, as the value of a well engineered, safe, lightweight plastic casing can be substantial.

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