Originally Posted by Rick Hohwart

You do not need a specific lead for these batteries. The one you listed is similar to one that we sell so the design is not a problem unless there is something wrong with the solder connections of the lead. But if you have successfully charged other batteries with this lead, it is likely not the problem.

One thing we see from time to time with leads like this is connections that have not been soldered, but have been shrinked and the shrink wrap holds it all together. It may work intermittently this way so check it out.

If you are getting a pack reading of 7.4 you are fine.

Does the battery charge if you use a non-balancing charge mode? And do the batteries work in a vehicle? If so there may be a bad connection to the battery balance port which would allow the battery to work correctly but not allow if to balance due to the dead balance port.