Battery Charger - FM radio interference

[bjmansfield]

I recently installed a Xantrex Truecharge20+ battery charger.  Everything works great except that when the battery charger is on, it generates a lot of static in the FM radio.  Any ideas or suggestions on eliminating the static interference??

[Pat]

I have the same problem with the TV  look forward to responce.  But it is a great charger installed mine last year and my batteries have never been better.

[Roc]

Hello Jack, how's that shaft seal been??

Can't help you with your particular situation, but I have a similar problem with my Acugage tank monitor.  When I press the button to give me a reading on one of the tanks, the FM gets static.  As soon as I let go of the button, it's fine. When playing a CD, there is no problem.  Maybe there is some similarity with the reason this happens and an Electrical Engineer on this site could point us in the right direction. I've tried hooking up a noise suppressor on the positive and then on the negative wire, but that didn't help.  I tried the suppressor on both the radio and the Acugage.  Also called Acugage and they couldn't give me a solution. :confused:

Roc-

[rirvine]

These are very difficult problems to solve.

RF generated by the switching regulator in the charger causes the problem.  Since the charger is not a consumer product, it does not have to pass the same FCC certification as something you would put in your house â€" hence can interfere with other stuff.   The RF can get to the FM radio one of two ways â€" conductive through either the AC/DC power system or transmitted through the air.  To sort these outs use a test with a FM radio that does not use any boat power.  If it still happen, then the problem is transmitted.  If it does not, the problem is conductive.

Possible solutions:  

If it is conductive, you need to stop the RF for getting to the radio through the DC power or DC ground using inductors around these cables.  You can buy kits from auto parts stores that may work or take some off some old computer cables.

If it transmitted, you have a much larger problem as you have to stop the RF from getting into the air either from the units or from the cable that connect to the unit.  For the units, make sure the case is grounded. If that does not work, place the unit in a separate grounded metal case with as few holes as possible.  For the cables, using inductors on them close to the units could solve the problem.

Sorry there is no quick fix

.

[bjmansfield]

Roc:
Good to hear from you. Hope all is well and your PSS problem has remained fixed.  
The shaft seal problem is fixed (I think).  To make a long story shorter, I replaced the front motor mounts (haven't gotten to the rear ones yet)and aligned the prop shaft for the  umpteenth time.  While aligning the shaft I noticed the top nut on the aft/port motor mount had worked itself up about 1/4 inch so I tightened it back down.  The shaft seal hasnt done the chatter bit since.  I suspect that under certain conditons, the motor was torqueing up on that motor mount and causing the seal to chatter??  Whatever the case, it appears to be fixed.
Jack--

[bjmansfield]

Ray:
Thanks for the response re: the interference.  Somehow I knew there was no easy solution to this.  I will take a battery powered FM down and see if I can determine the source of the interference and go from there.  It's only a problem when I'm in the slip so I may well ignore it and perhaps it will go away !!
thanks again,
Jack

[rdavison]

A general comment on the RF interference you're experiencing - It's mostly radiated and there's no easy way to reduce it except perhaps to box the charger up in a metal box.  I say perhaps because even then you will need to bypass each lead where it leaves the box and then put ferrite chokes on the leads as well.  Then you need to worry about cooling...

Even if you quiet down your own charger, you'll find that loads of rf garbage is radiating from other boats and being conducted in on your power cord.  Turning off your power switch at the boat or dock will usually not help as the ground line is usually carrying as much noise as the hot line.  Unplugging your power cord at the dock end can make a difference - does for me.

The use of switching regulators in chargers has just about stopped me (and others) from using ham radio at any dock across the hf spectrum from 1.8 to 30 Mhz.  To check into regional marine ham nets, I have to be anchored well away from a marina.

It's a shame that manufacturers were able to get away with saving money by using a loophole in the law to transfer the problem to their customers - of course chargers are less expensive as a result.

Randy Davison  k7voe