Ham radio causing battery to cut out?

I have an Ampere Time 200AH battery that I was using to power a ham radio station. Over the course of a weekend event (field day), the battery cut out 3 times. By cut out I mean the terminal voltage went to zero. Applying a charging voltage for a few seconds restored the battery to operation. I'm wondering if RF is causing the BMS to activate one of it's protection circuits. I was operating on 20 meters at the time. The cells performed well, they were still at 76% after the weekend. Has anyone else experienced this or have any thoughts?

I was in two-way communications (Police, Fire, commercial, industrial) for over 40 years. Most electronic equipment is not RFI hardened. I've seen equipment do some weird things when the microphone is keyed, like a farm tractor that went into crab-walk mode.

Manufactures could fix this with about a dollars worth of capacitors and ferrite beads on the wiring into a device, but they go for least cost. So yes, I would say the RF was messing with the BMS causing it to shut down. You could try a ferrite bead (large size!) on each of the power wires as close to the battery as possible.

Bipolar devices are more susceptible to RF than MOS devices. Thankfully most equipment now uses mostly MOS devices inside.

Did it happen in transmit? Have you tried a large electrolytic capacitor on the terminals of the battery? large current surges can cause the BMS to trip. Aluminum foil taped to the battery or metal container could be an option if RF is an issue.

Sounds like you went over the current limit on the BMS and it shut down.

Does the BMS log any reason for the cut-outs?

Try ferries on the battery cables and ceramic 0.1 uF capacitor across the battery.
What power levels are you transmitting at? Tie the battery negative to a ground rod.
Keep the battery away from the transmitter. Fit the battery into a metal enclosure.

WN8HCV said:

I have an Ampere Time 200AH battery that I was using to power a ham radio station. Over the course of a weekend event (field day), the battery cut out 3 times. By cut out I mean the terminal voltage went to zero. Applying a charging voltage for a few seconds restored the battery to operation. I'm wondering if RF is causing the BMS to activate one of it's protection circuits. I was operating on 20 meters at the time. The cells performed well, they were still at 76% after the weekend. Has anyone else experienced this or have any thoughts?

Click to expand...

I'm a Ham.

How many radios using it and how much transmit power from each radio?

Distance between the antenna and the battery?

Was 20 meters the only band you were on? Have you worked other bands without problems?

How old are the radios?

Only one radio, Icom 706, 100 watts on CW, 30 and 40 meters, only happened on 20. Steady-state current 22 amps. Dipole antenna at 38' directly above RV. Thanks for all the suggestions, I will try some of them next time out.

Did some checking, That battery has a 100 amp BMS so I doubt you came close with the IC-706. It could be RF getting in to the BMS. Quick way to test is to transmit in to a load and see if the problem goes away.

Wind 10 turns of both + and - battery cables through FT240-31 ferrite toroid placed close to battery terminals. That should prevent RF energy from getting into BMS of your battery.

Clip on ferrites provided with power cables, etc. installed on the power leads as close to the battery as possible will help immensely.

I've been fighting RFI for 50 years, and those things are a Godsend. Easy to use and effective. And often they're free, since so many folks don't use them.

I assume you're using coax. If you are, use some there too. Keeping the feed lines from radiating will help, assuming you're more than a few feet from the antenna.