6400 Max Supply Voltage

Delbert McCord

My 6400 runs in my barn where of my Battery band for my solar power setup. Here in Michigan is gets cold and when its cold the panels are more efficient. I am wondering what the max voltage I can feed into the Flex 6400. I have read on a post someone said 15 volts. When the Charge Controller sees a good sunny day and the bank is changed it goes into equalizing mode which takes the voltage way up (today is was 15.87 when I turned off the panel). When I set up this system years ago I had ICOM's and I asked them and they said 13.8 + - 15% so that gave me a max voltage of 15.87 which is why I turned off the single panel what was charging at the time. 

I have 115 volts out here if I need it and I could connect a Switching power supply to just the Flex but I really would rather be using the free power I worked so hard to build. 

What would happen if the voltage gets to high? Will the rig just turn off or will it hurt the 6400? 

Thank you for any information people can send my way.
Delbert McCord K8OCN

Bill -VA3WTB

Does a Flex have over voltage protection?  Really good question.

Greg N8GD

You should be safe at 15.87 VDC.  The 6400 Hardware Manual lists the input voltage the same as your Icom: 13.8 VDC +/- 15%, which gives the 15.87 VDC maximum figure for the 6400.  After the voltage drop through the supply cable and the lossy power poles, you'll certainly be under the 15.87 VDC figure.

Steve K9ZW

Kind of wondering why the direct feed? Do only some PVA setups use batteries? Appreciated your information that the effectiveness improves at low temps. Hadn’t known that. Would doing a slight drop-down by transformer and then running the say max 12vdc through a “booster regulator” like TGE used to build give you a steady supply voltage? While TGE is closed, the Nov 2004 QST article has build information http://www.repeater-builder.com/backup-power/pdfs/the-n8xjk-boost-regulator.pdf and a West Mountain Radio does an updated N8XJK Boost Regulator as a commerical product. Expect there are others, and one place to check would be for marine use. 73 Steve K9ZW Blog: http://k9zw.wordpress.com

Ha Gei

I would go for a overvoltage protection device. There are quite a few ideas to find. Switching off via a MOSFET at more than 15 Volts.  You can also go for a shunted Zener diode circuit cutting off at 15 Volts. If the flex draws 25 Amps at TX , at 16 Volts you have 25 Watts ,and even at 18 Volt, 75 Watts should be okay for a cooled 50Watts zener. 

Delbert McCord

Thank everyone for all the great suggestions. 

What I have done for now is went into the house and took the Jetstream 35 amp switching power supply out of line (not being used any more, I only go down there to do backups) . Connected the Flex and the AT-Auto tuner to it and while I was connecting it up I saw the terminals for the backup 12 volts that it has. I forgot I did at one time have a sealed battery down there in case we loose power. We are out in the country and when we first purchased this house 30+ years ago loosing power was a regular thing. I connected the power from the battery bank to the terminals on the power supply for backup up battery and now I am all set. I put the plug for the power supply handy to where I site at this computer and all I need to do is unplug it and I am running on the battery bank. 

I have a nice digital meter here so its easy to monitor the voltage as long as I am here, so if I am here I just unplug it but I am enjoying the remote operation so much I think I want to leave the rig on sometimes when I am gone. I checked into our local 80 meter net last night on the way to drop my Granddaughter off at a basketball game last night. That was cool! After I had the heat issue with the 6300 I have always only turned the rig on for the net and turned it off afterword so not to wear out the new fans. The 6400 I had on for  a few hours (6) and I touched it and it was a little warm but not bad at all so I am thinking I can try leaving it on more. 

I am thinking that I do not want to leave it this way, so I have been doing some price shopping and I can replace my sine wave inverter that I originally purchased for 550$ with one for only 125$ (man the prices have came down in 10 years) I think the way I will go is to convert my battery bank to 24 volts, I can re wire my panels easy enough and I found a 40 amp (I will only use it to 20 amps I like to have a lot of head room) so I will feed the power to the shack/reloading room at 24 volts and then regulate it down to the 12 volts I need. This will be less loss in the panels (will feel into the charge controller at 70 volts instead of 35) and then any voltage drop in the 50 feet from the battery bank to the shack will not be a problem. I ran 2 runs for each + and - of # 4 wire in here but still there is a voltage drop to the point that I picked up a MFJ Super Battery Booster and if I am going to be transmitting I just turn it on and it keeps a solid 13.8 volts at the Rig Runner power **** I use to fuse and connect all the equipment including lighting, even charges my iPhone and powers my hearing aid Bluetooth transmitter and my little Raspberry Pie computer. 

Well this plan with having the power supply connected to the battery bank is not going to work I will need to switch it manually, as I am typing here I just saw the Flex flashing RED that means the voltage is to high. Sure enough it was back to 15.85 (1:07 pm in Michigan) so I just reached up and pulled the connectors off the RigRunner so its 100% power supply. So I need to get some equipment ordered and get this done. I have been thinking about converting to 24 volts for some time. When I move to our cabin in hopeful 4 years I will have to rewire it all I was hoping to wait until then. 

I just remembered I have a ICOM 5100 out there just above the shooting bench I will have to get it a regulator as well. 

Thanks again for all the Great suggestions.

Del McCord K8OCN