This old marine battery charger creates a hum in a VHF radio broadcast

Thread Starter

sdowney717

Joined Jul 18, 2012
648
My old charger is very reliable, but when its on, and you talk on the marine VHF, any channel, it creates a backround hum and it sounds like the typical 60cycle type sound. You dont hear that in an FM radio, and you dont hear it in Marine ship to ship VHF radio when hearing other people, its just when your broadcasting AFAIK. I can hear it in the radio when I press the PTT microphone also. Maybe does that becuase the vhf broadcast draws more amps from the charger and charger boosts the output current.

If I turn it off, then no hum in the radio, nice and clear.

I have the schematic and some pictures, can anyone help me create a filter that would help?
I discovered the problem when doing the SeaTOw radio check on channel 26, they play back your voice and the hum is terrible.
convertordiagram2.png

The album has some more info on parts numbers and real life pictures of this thing.
https://photos.app.goo.gl/Ppq7Dm9CbFBMrkZu8
 

dendad

Joined Feb 20, 2016
3,564
Do you have the radio connected directly to the battery, or is it just to the wiring loom?
A battery in reasonable condition is a fairly good filter. But you can buy super caps used for care stereo filters too, and that may help.
 

Thread Starter

sdowney717

Joined Jul 18, 2012
648
Its you typical boat wiring system. All three banks of batteries are charged by the charger.
Charger output wires go to common busses for banks 1 and 2, not direct to the batteries, bank 3 goes to the battery for the generator.

Radio negative is on the main negative buss, positive is on a second positive buss, not the main buss.

Its an 8 gauge wire on the outputs from charger, thats hard to wrap around a ring. Maybe if its a big ring?

Would putting filter electrolytic capacitors on the output wires of say 1000uf do anything? I also have a lot of 3300uf 25 vdc capacitors I can use.
 
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dendad

Joined Feb 20, 2016
3,564
What if you put caps on the ammeter wire to ground (look at schamatic) before those 3 diode isolators.for the three battery banks?
That may not work. The SCR could stay on. It will need the voltage to return to zero to shut it off.

Just a thought, can you connect your radio to one of the other batteries to see if it is a battery that is a bit low?
Also, I would recommend connecting the radio power leads directly to the battery, through an extra isolator switch and fuse.
 

Thread Starter

sdowney717

Joined Jul 18, 2012
648
Batteries are all up and good too.
The radio is connected to the house bank of 2 12v marine deepcycle batteries which are 2 yrs old.
 

Thread Starter

sdowney717

Joined Jul 18, 2012
648
I have thought of something that would work I think, run radio off a PC power supply. Issue is AC availability. I do have a gen and I do have an inverter. But it adds a layer of possible failures. I do have several older AT style, not ATX, they use an actual hard on - off switch. Radio may use 5 to 8 amps of 12v dc current. Dont recall if those supplies can deliver that I think they can, they are 200 to 250 watt supplies.

I could also add a DPDT switch to select the power sources.
 

drc_567

Joined Dec 29, 2008
855
Just a guess ... something to check out.
... A current of several amps crossing any kind of gap can create an arc with resultant VHF interference. If the circuit breaker next to the battery bank has not been cycled very many times maybe there is some kind of residue build-up on the contact surfaces resulting in a partial gap when it is closed. So try spraying electronic contact cleaner into that circuit breaker and switching it a few times.
... I had a side-walk sale amateur radio transmitter that completely blocked out the broadcast TV transmission each time the transmit button was pushed. It turned out that there was a big crack in the transmit circuit board trace just before the connector to the roof antenna, and it made a visible spark. The interference was wide-band and completely prevented any TV watching.
 

Thread Starter

sdowney717

Joined Jul 18, 2012
648
I am going to play around with caps I have, if that wont work, I will play around with PC power supply.
I use a PC on the boat, ATX style with a PSU. Could tap into the 12dc output. And easy to do.
And I could use a DPDT relay, so that if PC is on, PSU is on and power to relay is on, then power to radio is on. When computer power goes off, power reverts to boat batteries.

Honestly I wonder how many boaters have to go through all that. A new charger, big bucks, might solve the issue. But I am cheap. My old charger-converter, I see no filtering in the output whatsoever.

My ATX PC runs off an old Minuteman backup PS. I disabled the beeper as it is just wired to mains with no internal battery. And I added an internal fan to help cool it as its more of continuous use now.
 

Thread Starter

sdowney717

Joined Jul 18, 2012
648
How often do you talk on marine VHF radio while still moored to docks and plugged into AC mains?
I agree, youd think so.
Excoept there is this. I have a generator on the boat.
I start that up, and the battery charger charges, so anytime my gen runs, I would have the problem.

Now I can turn off the charger, but who wants to do that off then on all the time, then, if I forget to turn it on, when I leave boat in slip, the batteries will run down.
I have to make sure captains seat is up, then open a panel and flip the charger switch on and off. Knowing me I would forget.
 

Thread Starter

sdowney717

Joined Jul 18, 2012
648
At the boat tried this.
I put up to three 3300uf electrolytic caps in series so 1100 uf, (tried just one and two also ) across the positive and negative main buss that feeds radio power, not any improvement.

I did notice when engine runs, the ignition power turns off the charger on those 2 input sense wires (ignition shutdown look at schematic) and that original noise goes away to be replaced by spark ignition noise (something else), but original noise goes away.

I was wondering this, how to sense when radio PTT microphone is pressed, then put 12 vdc on a sense wire, which would turn off the charger output. Radio draws 3 or 4 amps when broadcasting and maybe 0.5 amp when listening, so if a circuit could be designed, would fix the problem.

I also think this charger is pulsing DC current into the batteries, its not smooth DC output, so I wonder if any filtering could even work.

Any ideas about all that?
 

Thread Starter

sdowney717

Joined Jul 18, 2012
648
Then there is this idea, current thresholds can be set, mentions the 3 buttons.

BUT, is the documentation such that it can be figured out, mentions mode setting says nothing much on how to set it up!
Anyone know?

Ok, reading another description gives this info.
It is still OBTUSELY described, imo. Maybe can be deciphered.

Function Description:
P-11: When the measured current is greater than I1, the relay is closed; when the measured current is less than I1 again, the relay is disconnected.
P-12: When the measured current is greater than I1, the relay pulls in; always keeps the pull-in until the board is powered off.
P-21: When the measured current is greater than I2, the relay is closed; when the measured current is less than I1, the relay is disconnected.
P-22: When the measured current is greater than I2, the relay pulls in; always keeps sucking until the board is powered off.
P-31: When the measured is less than I1, the relay is closed; when the current is greater than I2, the relay is disconnected.
P-32: When the measured current is less than I1, the relay pulls in; always keeps the pull-in until the board is powered off.
P-41: When the measured current is between I1 and I2, the relay is closed, and the relay is disconnected in other cases;
P-42: When the measured current is between I1 and I2, the relay pulls in; always keeps the pull-in until the board is powered off.
P-51: When the measured current is less than I1 or greater than I2, the relay is closed, and the relay is disconnected in other cases;
P-52: When the measured current is less than I1 or greater than I2, the relay pulls in; always keeps the pull-in until the board is powered off.

Setting instructions:
Power on to display the measured current; (if the measured current is suspended, the number of digital jitters is normal)
Pressing the first time K1 takes more than 1 second to be effective, preventing false triggering. Screen display: P 11: K2 adjustment mode, K3 adjustment function
Pressing the second K1, the screen flashes: 0.05 means the value of threshold I1 is 0.05A; K2 sets I1 plus, K3 sets I1 minus
Pressing K1 for the third time, the screen flashes: 0.10 indicates that the value of threshold I2 is 0.1A; K2 sets I2 plus, K3 sets I2 minus
Pressing the fourth K1, the screen displays the measured current; indicating that it enters the standby state;
Long press K2 or K3 in standby mode to fine tune the measured current error

https://www.aliexpress.com/item/4000028650601.html?spm=a2g0o.productlist.0.0.725d4d2cPT9KBz&algo_pvid=5a01c4b0-16ab-4b6a-b29b-4de2f4e0fa53&algo_expid=5a01c4b0-16ab-4b6a-b29b-4de2f4e0fa53-32&btsid=75677b17-6db6-4d26-afc6-7ec386406341&ws_ab_test=searchweb0_0,searchweb201602_4,searchweb201603_52


 

Thread Starter

sdowney717

Joined Jul 18, 2012
648
Posting second set of instructions which might be clearer.
Anyhow its cheap.

This module can detect DC current in the range of 0-10A, the accuracy is 0.01A.

Features:
Detecting range: DC 0~10A; accuracy: 0.01A(10mA).
Detect the current to control the relay then control the circuit on/off.
Set delay time to prevent output shock so as to protect the circuit.
With error calibration function.
Can turn off the LED display to reduce power consumption.

Functions Description:
P-1: Over-current Detection: when the detecting current<I1(low limit setting), the relay closes; >I2(high limit setting), the relay opens.
P-2: Under-current Detection: when the detecting current>I2, the relay closes; <I1, the relay opens.
P-3: Close in the Range: when the detecting current is between I1 and I2, the relay closes; relay opens in other situation.
P-4: Open in the Range: when the detecting current is between I1 and I2, the relay opens; relay closes in other situation.
P-5: Error Calibration and Delay Time Setting: the relay would not operate.

Buttons Description:
K1: Modes Selection;
K2: "+"
K3: "-"
Long press K1 for 2s into modes selection; short press K1 to select function and K2 to enter the mode.

Note:
After power on, the LED digits would pulse if the detecting current terminal is none.

Specifications:
Voltage: DC 12V
Detecting Range: DC 0~10A
Accuracy: 0.01A(10mA)
Standby Current: Approx. 20mA
Display: LED Digital Display
Item Size: 65 * 40 * 18mm
Package Weight: 29g / 1.04oz

Package List:
1 * DC Current Detection Module
 

dendad

Joined Feb 20, 2016
3,564
I know I've asked it before, but have you tried running separate fairly heavy power cables directly from the battery terminals to just the radio?
Not using the wiring loom at all? It is a good test to try.
 

Thread Starter

sdowney717

Joined Jul 18, 2012
648
I know I've asked it before, but have you tried running separate fairly heavy power cables directly from the battery terminals to just the radio?
Not using the wiring loom at all? It is a good test to try.
ok, I can try it, why would that work, its all interconnected anyway. The charger output does charge the batteries.

I think the current sense relay idea has good potential.

I also think maybe its not ac line hum, maybe its radio wave interference coming from the charger when the load increases? Clearly I dont know.

Another thing, press the mic, and you can hear interference 'hum' coming out of radio speaker when charger is on. Charger off, its silent., so maybe not vhf frequency interference.

Put digital meter on AC range and on DC wires + and -, result is numbers jumping all over the place on the meter like a cyclical thing.

At least no other DC appliance or DC device, meter, gauge is affected by the charger., not that I can tell.
 
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dendad

Joined Feb 20, 2016
3,564
It is fairly standard practice to wire radios directly to the battery. Then, you eliminate the noise generated by voltage drops from the shared cables. It often helps with inter-device interference.
There is something wrong with your installation there as you say the radio gets noise from the engine too. It may even be a corroded connection or something odd like that. Sometimes, chasing down this can be "fun".
Did the radio ever work ok, or has it always had this problem?
The current sense relay idea may work, but it is fixing a symptom, nor a cause.
 

Thread Starter

sdowney717

Joined Jul 18, 2012
648
It is fairly standard practice to wire radios directly to the battery. Then, you eliminate the noise generated by voltage drops from the shared cables. It often helps with inter-device interference.
There is something wrong with your installation there as you say the radio gets noise from the engine too. It may even be a corroded connection or something odd like that. Sometimes, chasing down this can be "fun".
Did the radio ever work ok, or has it always had this problem?
The current sense relay idea may work, but it is fixing a symptom, nor a cause.
Its one of those if you dont know you have a problem, you dont care.
I just discovered it doing a radio check the plays what you say back to you, so you get to hear your own broadcast. Its a Seatow service, in Seaford Va its on Channel 26.
So you dont ever actually hear your own broadcast signal.

Its probably spark ignition interference, it hits like little ticks of noise which varies with engine speed, it s not a steady hum like the charger produces.
And even though its annoying, people can still hear your voice thru the noise. You should hear how bad some other boats sound, some are great, and some its tough to make out what is said.

Without the charger on or an engine running, my radio sounds great. That engine was the port one, I have not checked starboard or generator yet.

Another potential noise could come from a PC PSU, some I tested in the past were extremely bad, and some really quiet. So I think the one I have is pretty quiet now.
Problem is no one really markets them as to how much electrical noise they make, so maybe potluck or buy a good one you can send back.
 
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