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Author Topic: RFI from battery charger  (Read 8377 times)
W0TLP
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Posts: 83




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« on: February 05, 2012, 08:57:22 PM »

I have 6 40Ah batteries to run my shack, which is a single all-band, all-mode radio, a couple of scanners and an LED strip.

The batteries are AGM. I charge them with a CTEK 3300 smartcharger http://smartercharger.com/battery-chargers/#CTEK%20Multi%20US%203300, which I chose because it charges at over 14.7 volts (per the battery manufacturer's suggestion).

Of course, the charger puts off some fairly serious RFI on the low bands. It is bad enough when I am just charging the batteries but if I try to run the rig off the batteries while the charger is plugged in to AC it's way worse.

This noise is most prevalent from 3 MHZ to about 12 MHZ on AM, a little less on SSB. For the ham bands I use, it makes 40 meters almost unusable, 80 meters usable while putting up with the noise.

I have put some ferrite cores on the DC line to the radio and on the AC line of the charger, but I don't notice a reduction in the noise.

I don't see any indication that this charger is FCC Part 15 compliant.

Any suggestions that don't involve getting a different charger?

I am running the shack on a power supply now, which works fine, but I'd love to run it on the batteries.


Thanks

Teak
W0TLP

P.S. This is not related to my previous RFI question involving the low-pass filter and 10 meters. That issue was while I was running on the power supply.
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WB4BYQ
Member

Posts: 179




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« Reply #1 on: February 06, 2012, 06:13:35 AM »

you may have to try a filter much like this one to filter the rfi from the ac line.

http://www.w0qe.com/RF_Interference/grow_light_electronic_ballasts.html

or a battery charge such as this one, i have two and no rfi.

http://a-aengineering.com/5ACatalogPage.pdf


richard
wb4byq
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WX7G
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Posts: 6136




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« Reply #2 on: February 06, 2012, 06:39:30 AM »

I would recommend an off-the-shelf AC EMI filter both for safety and effectiveness. If you want a model number I'll provide one.

On the DC side you can roll your own filter. The asymmetry of the batteries and radio are such that differential-mode to common-mode conversion after the common-mode choke could render the common-mode choke ineffective. If so differential-mode filtering followed by common-mode filtering is the way to go. I can provide a schematic or an off-the-shelf EMI filter.

I would not expect a battery charger to employ much, if any, filtering at the DC output since it is not needed for charging a battery.

Or for simplicity at higher cost order an MFJ-1142 filter for the DC side and an MJF-1163 for the AC side.
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W0TLP
Member

Posts: 83




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« Reply #3 on: February 06, 2012, 08:55:37 AM »

Thanks, guys. This helps.

I think I'll put this charger on eBay for the BMW motorcyclists. I got it at a BMW store -- dang near became a motorcyclist that day!  Grin

I may take Richard's suggestion for the charger. It's more money than I wanted to spend but probably worth it.

My long-term preference is to run it all on solar, but that project is a little farther away.

Teak
W0TLP
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K1DA
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Posts: 514




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« Reply #4 on: February 12, 2012, 08:18:17 AM »

I've been riding a BMW since 1982. 
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VE3FAX
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Posts: 7




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« Reply #5 on: November 09, 2012, 03:48:58 AM »

WARNING! The CTEK chargers (CT3300) are horrible RFI offenders!! I have the same problem. Bought one ($80.00) new specifically for use in the radio room to charge my back-up battery.

Using a protable SW radio outside in the backyard one day, I found the whole Short-Wave band bombed by digital hash!!  If didn't occure to me at first that it was MY charger, as I was more that 300 feet away from the house...WRONG..It was the charger. IT even spews hash when turned off and plugged in.

RFI comes from the AC power cord AND the 12VDC cord. I have tried various toroids to no avail. I have posted the problem to a CTEK tech, and will report what they say. T casing is plastic, so that doesnt help with leakage.

too bad..these are a three stage chager and have a good reputation otherwise. But the thought of just ONE of these float charging a battery all year in a neighbours house gives me the chills...an effective radio black-out generator! 

G
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K4TNT
Member

Posts: 2




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« Reply #6 on: November 09, 2012, 04:13:29 AM »

These multi-stage "smart chargers" are chronic RFI producers.

For more than a year I suffered with RFI noise on 40M all the way through 15M.  The signature included noise bursts about 4KHz wide spaced every 65KHz, classic signs of a switching power supply.  I knew it wasn't coming from my house and eventually I got around to DF'ing it with a portable SWL receiver. 

The problem turned out to be a Guest model 2611 "smart charger" on a nearby neighbor's boat.  Because he used it to keep the batteries charged in 'float mode' the charger was powered up 24 hours a day, 7 days a week.

Many of these chargers - including this one, are approved under FCC Part 15A - for use in commercial / industrial environments only.  Here's what the Guest user manual has to say about that approval:

"FCC Class A EMC Notice

This equipment has been tested and found to comply with the limits for a Class A digital device,
pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection
against harmful interference when the equipment is operated in a commercial environment. This
equipment generates, uses and can radiate radio frequency energy and, if not installed and used in
accordance with the instructions, may cause harmful interference to radio communications.

Operation of this equipment in a residential area is likely to case harmful interference in which case
the user will be required to correct the interference at his own expense."


Fortunately I have a great relationship with this guy, and together we worked on a couple of solutions including putting a commercial EMI filter on the AC line (45db rejection at 1-30MHz)... with no significant change observed.  The noise is still radiating from the power line.

Temporarily we've put a 24-hour timer on the charger so that it only is powered up from midnight to 6:00 AM, so at least the interference doesn't occur during my operating hours.  The long term solution we settled on is to replace the charger with a Part 15 Class B charger such as the Xantrex Truecharge2

http://www.xantrex.com/power-products/battery-chargers/truecharge-2.aspx

Hopefully this will solve the problem.... we'll see.
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WB4BYQ
Member

Posts: 179




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« Reply #7 on: November 09, 2012, 11:06:15 AM »

Had the same problem with a neighbor boat charger for is 3 on board deep cycle batteries.  The RFI goes round the filter
thru the ground wire.  had to use a common mode choke from ft-240 type 31 material.

there are emi filters with the ground wire choked,  have seen standard emi filters with the green wire ground with ferrite
chokes on them.

richard
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LA9XNA
Member

Posts: 109




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« Reply #8 on: November 17, 2012, 02:29:43 AM »

Keep avay form the CETIC brand of chargers in ham use.
A few years back I used to work for a radio shop.
At that time we had a line of repeaters markedet for the fish farms.
The repeaters where equiped with a 60Ah battery and a cetic 4A charger.
After installing 4-5 repeaters our customers came back complaining a mout short range and alot of noise on the audio.
Then we dis some investigations and found strong birdlies all over including a few khz form our RX frequency.
The remedy where to go for a linar charger.
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K4TNT
Member

Posts: 2




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« Reply #9 on: November 20, 2012, 04:43:12 AM »

The long term solution we settled on is to replace the charger with a Part 15 Class B charger such as the Xantrex Truecharge2....Hopefully this will solve the problem.... we'll see.

Success!  The new charger took care of the problem.  Even without any EMI filtering on the input or DC leads the charger is quiet.  You can hear a bit of hash with an AM / SWL portable receiver when right at the charger, but it drops off rapidly and is not heard from more than a few feet away.
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K1DA
Member

Posts: 514




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« Reply #10 on: December 04, 2012, 09:55:10 AM »

  Why not buy a 12 analog supply and crank up the regulator to qbout 14.2.  That ought to keep the battery happy and not make a lot of noise.
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