Lectro SMDA drawing current when off

[Ed Denton]

This is an odd one. I’ve discovered that when I put new AA batteries (eneloop pro) in my Lectro SMDA transmitters the night before a shoot, when I power on the transmitter the next day the batteries are are low voltage or dead completely. It seems as though the transmitters are drawing current when completely off. Could this be shorting or something. I can’t imagine how else the battery power is being consumed. 

[Matthew Steel]

We had some SMa (which, I believe, is electrically identical to SMDa except for the dual batteries) for a while and it was my experience that the batteries did run down after being in the transmitter a while.  But never so much as to make a noticeable difference just overnight.

 

Any chance you always use the same set of batteries and one is bad?  Depending on the way the dual battery setup is implemented internally it could be possible for a bad battery to slowly drain the other - but not fast enough to notice under normal use.

 

As a point of reference, our SMa transmitters would go about 1.5 hours on an alkaline and about 4.25 hours on a lithium.  With dual batteries you should be getting in the neighborhood of double that if both batteries are contributing.

[LarryF]

On 10/2/2018 at 4:22 AM, Ed Denton said:

This is an odd one. I’ve discovered that when I put new AA batteries (eneloop pro) in my Lectro SMDA transmitters the night before a shoot, when I power on the transmitter the next day the batteries are are low voltage or dead completely. It seems as though the transmitters are drawing current when completely off. Could this be shorting or something. I can’t imagine how else the battery power is being consumed. 

Hi Ed,

Put one battery only in the SMDA with the battery door open and the SMDA off. With a digital Volt meter (DVM) set on current, place one lead on the negative terminal of the battery and the other DVM lead on the SMDA case. This will tell you if there is an abnormal current drain. There is a small leakage current of a few mA's to enable the power on function but that won't run a battery down for weeks. I assume you have a DVM; they are so cheap anymore that they are an essential tool in your kit. Remember to never connect a current meter directly across a battery or other voltage source; much smoke and frustration will ensue. Also switch the meter back to normal voltage operation before you put it away. I know this personally from several sparky incidents. The negative terminal to case hookup above places the current meter safely in series with the battery to read its drain.

Best Regards,

Larry Fisher

 

[jpb2]

16 minutes ago, LarryF said:

 

Put one battery only in the SMDA with the battery door open and the SMDA off. With a digital Volt meter (DVM) set on current, place one lead on the negative terminal of the battery and the other DVM lead on the SMDA case. This will tell you if there is an abnormal current drain. 

Perfect idea Larry, I only worry that with one battery There might be a "low power-off" mode that the unit might slip into. Creating a batt rig and putting the meter in-line would be a next step.

[LarryF]

2 hours ago, jpb2 said:

Perfect idea Larry, I only worry that with one battery There might be a "low power-off" mode that the unit might slip into. Creating a batt rig and putting the meter in-line would be a next step.

There is no low power off mode for one battery. The SMDA is perfectly happy with one battery; it just acts like an over sized SM single battery unit. Same boards and firmware exactly.

In sum, it is a valid test.

Best Regards,

Larry Fisher

[Ed Denton]

Thanks Larry, I will try out what you suggested and test my batteries to see if one is bad. Will report back my findings