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Combining NiCd Battery Packs

By 03/02/2013 June 4th, 2020 Battery Expert Q&A

The Question:

Just sorting out my radio gear for my Pica 1/5 scale Mustang and discovered that I have two 600 mAh packs but not a 1200mAh pack like I want. Anyway I found some extra Y connectors and viola, a light went off. Why not connect the two 600mAh packs in parallel with the Y and get a 1200mAh pack?

At the same time I could be doubling my reliability, unless of course something happens to one of the packs that drags the other down to nothing.

Anyway it seems like a good idea, and if its such a good idea how come I’ve never heard of anyone else doing it? Is there a gottcha that I’m overlooking here?

Red Scholefield replies:

No problem with running the two packs in parallel, but you must charge each one separately. This technique is frequently used by a number of people flying expensive airplanes and wanting the added reliability of dual power systems.

You would be better off from the reliability standpoint if you ran separate switch harnesses all the way from each battery to the receiver. Just plug the other switch harness into any unused channel of the receiver. This will allow you to check each battery separately prior to flight. Switch one on and check, then switch it off and the other on and check, then switch both on and fly. Sort of like the old mag checks on big airplanes. This also has the added advantage of allowing you access to both batteries for individual charging.

Disclaimer: Some feel that one pack will discharge into the other pack. This is better discussed between those that do not understand battery technology and therefore will not be addressed by the author of this post unless the query is to better understand why one battery will not charge another when both start at the same state of charge. The subject is not negotiable.