Battery charger - electrical interference

Submitted: Wednesday, Jul 12, 2017 at 13:11
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To the electrical gurus out there please

Its a 40 ah 5 stage 240v charger that causes the following frustrations. (But firstly a description of the power/sound system set up in the caravan)

# The van is wired so that the radio feeds to roof speakers
# The TV sound is connected via jacks and cable to the radio and hence the speakers
# Our van is all 12v (compressor fridge etc) and the issue is only relevant when we are forced to stay in caravan parks and the solar panels are shaded at that site...hence we need the 240v.

* When on "battery charge mode" it causes significant electrical interference to the sound system in the caravan. ...a high pitched oscillating whining noise making the sound system unusable.
* When on "supply mode" the issue goes away
* If I pull the sound out jack from the TV then the issue goes away ( when on battery charge mode) and we can listen but the TV speakers leave a lot to be desired as far as volume and sound quality.
* What I cant understand is that on supply mode our house batteries are slowly losing charge.......now after 4 days they are down to 74% SOC.........
* They would be a down to less than 50% ...in this time frame out in the bush with solar panels inoperative (like now) so therefore they must be getting some trickle top up from the 'supply mode'...but are losing ground

< So what is "supply mode" doing...a constant 12v supply I guess...and some trickle charge?...Like a full charge battery connected in Parallel to a discharged battery...they sort of equal out?

## If we run the generator out in the bush on battery charge mode the genny hunts something chronic....like fuel starving........I assume the charger electronic conflict with the genny electronics?....

Appreciate some diagnostic help please and and a fix if possible and a more definitive understanding of what the 2 modes are meant to do

Cheers

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Reply By: IvanTheTerrible - Wednesday, Jul 12, 2017 at 15:41

Wednesday, Jul 12, 2017 at 15:41
Battery chargers are not designed to be power supplies. They were never designed to power audio. What you are hearing is the output of the battery chargers switchmode circuitry. Easiest fix would be to put a filter on the power supply to the audio and TV
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Follow Up By: RMD - Wednesday, Jul 12, 2017 at 17:21

Wednesday, Jul 12, 2017 at 17:21
The generator hunting shouldn't be caused by the battery charger as Ivan has mentioned, the switchmode circuit is operating at high frequency and a filter of some sort would be needed.

The hunting of the generator would most likely be when it is operating on Eco setting and it's carby is a bit blocked in the jets and is trying to run but is starving and trying to run lean. Do you always drain the carby if leaving unused? If not it most likely has gummed the idle and or main jet and that is retricting normal fuel mixture. My Eu20i did the same in a very short period of time. Try running a small percentage of metho in the tank, cup full perhaps, of the gen to attempt at dissolving the gummy film which occurs. Not too much as it is not an alcohol carby.
If it doesn't cure it, removal of the carby, dismantling and soaking of the internals in solvent may have to be done.
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Follow Up By: Member - bungarra (WA) - Wednesday, Jul 12, 2017 at 20:00

Wednesday, Jul 12, 2017 at 20:00
Thanks

But it is definitely not a carby/ genny issue.

I have been down that path some time ago and satisfied myself to that.
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Follow Up By: Notso - Wednesday, Jul 12, 2017 at 21:14

Wednesday, Jul 12, 2017 at 21:14
I have a suspicion that the hunting is being caused by a pulsing charger.

As the charger pulses it will caused the genny to fluctuate in power levels to match the charger as it pulses power into the batteries.

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Follow Up By: The Bantam - Thursday, Jul 13, 2017 at 13:39

Thursday, Jul 13, 2017 at 13:39
Many generators will not respond favorably to any other than stable resistive loads.

The battery charger may have quite a significant power factor ........ try running something like a 500watt halogen lamp or such to provide a stable load and to mask the power factor.

Yes the output of many chargers will be noisy ....... the output of the charger is deliberately pulsed and this pattern may vary depending on what part of the cycle the charger is in.

In the power supply mode the voltage of the "not now a charger" may not be sufficient to charge the battery.

These so called "smart" switch mode chargers are a wonderfull thing ..... nothiong sticks charge to a battery as well or as fast WHEN it is working as a charger with a direct and exclusive relationship with one battery.

HOWEVER they can be problematic in a number of situations.

IF you are running a system off batteries while connected to mains ....... what you realy want is a steady state single voltage power supply / charger.
or what some would call a two stage analogue charger ....... it is voltage regulated at a single specific voltage and current limited. ....... AND with a smooth filtered output.

We have been running systems like this sucessfully for nearly a century ..... every telephone exchange and most other communications sites, most alarm systems and many other systems where they are supplied from mains and backed up by batteries at the operating DC voltage.

Unfortunatly you will have a hard time buying other than a switch mode multistage charger in the caravan market these days.

cheers
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Follow Up By: Nomadic Navara - Thursday, Jul 13, 2017 at 18:07

Thursday, Jul 13, 2017 at 18:07
Quote "Battery chargers are not designed to be power supplies"

Why?
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Follow Up By: Notso - Thursday, Jul 13, 2017 at 18:39

Thursday, Jul 13, 2017 at 18:39
I once owned a Ctek that was both! Basically output 13.8 volts. Whereas on Charge it would go through 7 stages or something around that.
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Follow Up By: IvanTheTerrible - Thursday, Jul 13, 2017 at 20:15

Thursday, Jul 13, 2017 at 20:15
PeterD. Since you are a retired radio and electronics technician you can put a current gen or any battery charger on an oscilloscope and tell me what the output waveform looks like.
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Follow Up By: Nomadic Navara - Thursday, Jul 13, 2017 at 20:25

Thursday, Jul 13, 2017 at 20:25
Ivan, The old simple chargers had a quite lumpy output. The newer multistage chargers can be well filtered have a smooth output. At least the models that double as power supplies do.
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Follow Up By: IvanTheTerrible - Thursday, Jul 13, 2017 at 21:53

Thursday, Jul 13, 2017 at 21:53
Do the test. The only difference is they now have high frequency interference instead of mains. I'm talking battery chargers not power supplies as was reported in the main thread

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Follow Up By: The Bantam - Thursday, Jul 13, 2017 at 23:12

Thursday, Jul 13, 2017 at 23:12
Sure there where and still are crude battery chargers that consist of little more than a transformer and a rectifier .... these have as would be expected fairly lumpy ( rectified sinewave) unregulated output..... with the addition of any crap that comes down the mains supply.

But there also where and are, properly filtered and regulated charging systems that where specifically designed to give a smooth output for the benifit of the equipment that they supplied

I have a ball tearer 20 amp regulated battery charger here that outputs a pretty damn clean DC output.
It's one of my best second hand buys ever.

I also have several regulated supplies I use to charge batteries ranging from 500mA to 5 amps ... all well regulated and giving a smooth clean output.

I also have several chargers that have dirty outputs and one or two that radiate quite a bit of spurious radiation such that it interferes with my workshop radio ( not connected to these chargers).

A device that is intended to charge a battery alone, realy does not need to have a clean smooth output ..... however if you are running electronics off the battery while it is being charged ..... it is advisable to use a charger or regulated supply with a well regulated, clean smooth output.

I have a couple of small switch mode multi stage chargers .... the documentation on the large one shows that at different stages, pulses are deliberately introduced in the output.

In the desulphation phase high frequecy pulses are introduced...... in one of the rapid charging phases the charge current is delivered in short low frequecy pulses ...... I've never tried to run electronics of this charger, because I have better equipment for that purpose.

cheers
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Reply By: Allan B (Sunshine Coast) - Wednesday, Jul 12, 2017 at 17:16

Wednesday, Jul 12, 2017 at 17:16
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Hi Bungarra,

Your charger would incorporate a 'switchmode' power supply running at a high frequency, 50kHz or more. If this is able to infiltrate your audio section it will sound as a 'whine'.

A real clue in all this is that....... "If I pull the sound out jack from the TV then the issue goes away ( when on battery charge mode) and we can listen but the TV speakers leave a lot to be desired as far as volume and sound quality."
It is highly likely that you have what is known as a "ground loop" in the radio path between the TV and the radio. This commonly comes about when there is not a clear single path for the 'earthy' conductor between the source (TV) and the receiver (radio). Such "ground loops" can be tricky to identify and resolve but a decent audio technician would handle it.

I can suggest two resolutions you can try.
1. Connect a solid (4mm or more) wire between the chassis of the TV and the chassis of the radio. This may prove difficult due to plastic cabinets impeding access to the product chassis. Note that I am not talking about the vehicle chassis.
2. Use a Ground Loop Isolator in the audio cable from the TV to the radio.
This is essentially a small transformer which eliminates any direct earth connection between the two appliances. Jaycar AA-3086 for mono and AA-3084 for stereo, both at about $10. If a ground loop problem, this will definitely solve it.

The use of "auto noise filters" may or may not diminish the problem. My experience is that they are usually not adequate.

You have not commented on whether the radio performs OK when the charger is operating and the TV audio cable is unplugged from the radio. If it is OK then this confirms the 'ground loop' diagnosis.

The issue re "supply mode" ..........
1. If the TV sound is unaffected when the charger is in 'supply mode' and the fact that your battery is losing charge suggests that the supply mode is simply not working. The switchmode circuitry would still be used in supply mode so the interference noise would still be present.
2. Supply mode puts out a constant ~12.6v which would be sufficient to keep the battery from discharging. So if the battery is "slowly losing charge" then the charger is not supplying 12.6v

It could be helpful to know the brand and model of your charger.

The gennie "hunting" is likely due to insufficient load. Those experienced with such genius may have comment on this.


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Allan

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Follow Up By: Allan B (Sunshine Coast) - Wednesday, Jul 12, 2017 at 19:41

Wednesday, Jul 12, 2017 at 19:41
.
Something else I should have asked Bungarra......
Is your charger connected directly onto the battery terminals, or is either the positive or negative leads connected elsewhere on the wiring system?
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Follow Up By: Member - bungarra (WA) - Wednesday, Jul 12, 2017 at 20:17

Wednesday, Jul 12, 2017 at 20:17
Hi Allan...I was hoping you would pick up on this thread.

In answer to your suggestions.

1) The charger cables do go through a bi directional shunt so as the PL60 solar controller can use the information for a more accurate assessment and charge control using in/out amps
2) The radio interference does not occur with the charger mode functioning and using radio only...no TV....and I didn't actually pull the audio plug...I just left in connected between TV and radio ...the TV was on standby....
3) Tonight I see my SOC has improved to 84% over the day...Battery voltage 13.2....its now dark and the read out tells me 14.3 amps is going in....so maybe the power supply mode is contributing but got behind a little...bit strange that one.
4) Just turned the TV on (power supply mode still) and the charge has gone to 16.7 amps.....so there appears to be something responding.
5) I will play with an earth wire direct as you suggest and see what happens.......no chance of a Jaycar visit or similar for a few weeks atm
5) unfortunately it is a no name charger supplied with the 'van.....looks substantial but ?...its just a large black box almost shoe box size :)

Thanks for your input...I will fiddle and get back

Cheers
Graeme
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Follow Up By: Allan B (Sunshine Coast) - Wednesday, Jul 12, 2017 at 21:16

Wednesday, Jul 12, 2017 at 21:16
.
OK Bungarra, some extra clues in there.......

The fact that there is no whine from either the TV or from the radio when used alone for sound out suggests that they are each OK. The whine only comes when you use the audio interconnection from TV to radio. Almost certainly then this is a 'noise' signal being introduced via that audio cable. If it is a 'ground loop'. it typically comes about when there are two (or more) paths for the 'signal return'. This return is normally via the the second conductor of the audio cable or the screen of the audio cable whose ends join the 'common' or earthy sections (chassis) of the two appliances together. If any there is any small voltage difference between the chassis of the two appliances then some small current will pass through the audio return conductor and introduce an interference into the signal.

The idea of bridging the chassis of the two appliances together with a solid cable is to parallel the existing signal return conductor with a low impedance path to bring the two chassis to closely equal potential so that no current passes through the signal return conductor. It is the easiest fix to try. The negatives of the 12v power supply to each appliance should be internally connected to the chassis so if it is more convenient, you could try connecting your solid bridge cable to those two negative inputs.

There is another way of eliminating a ground loop. It is a bit 'agricultural' but does sometimes work and is simple to try. Simply disconnect the return conductor of the audio cable at either end. Now there is no loop and the audio return path is via the power supply cabling. It may work or it may make the interference worse, or it may case loss of all signal, it all depends on circuit configurations.

Just one other possibility of interference is capacitive coupling between the audio cable and 12v power cables. Route the audio cable away from any 12v cables as much as possible. Certainly do not bundle them.

Cheers
Allan

Cheers
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Follow Up By: Allan B (Sunshine Coast) - Thursday, Jul 13, 2017 at 09:47

Thursday, Jul 13, 2017 at 09:47
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Another consideration Bungarra................

Do the 12v power supplies to both the TV and the radio come from exactly the same points, both positive and negative. If not, then there can be a small difference in potential, especially of the negatives.
Your comment about the bi-directional shunt alerted me to this. If the shunt is in the negative line of the charger there can be a few millivolts difference either side. If the TV gets its negative from one side and the radio gets its negative from the other side then the two appliances will have a few millivolts difference in their negatives (chassis potentials) which will certainly reflect the charger whine into the audio path.

My brain is running a bit slow from a massive head cold!
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Allan

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Follow Up By: HKB Electronics - Thursday, Jul 13, 2017 at 10:09

Thursday, Jul 13, 2017 at 10:09
As per Alans input, if the audio out is via RCA style plugs try partially removing the RCA plug so that only the centre pin is connected, this may cure the problem.

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Follow Up By: gbc - Friday, Jul 14, 2017 at 18:39

Friday, Jul 14, 2017 at 18:39
Plug an incandescent light into the genny to stop it hunting and drag it into 50hz. It's a trick we used to stop cordless drill battery chargers from melting in the days prior to inverter gennies.
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Reply By: Hoyks - Wednesday, Jul 12, 2017 at 17:26

Wednesday, Jul 12, 2017 at 17:26
Another option would be to turn off the charger and live off the 12V system for the evening and then flick on the charger when you go to bed. A 40A charger overnight will pump a fair few electrons back into the batteries.
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Follow Up By: Gronk - Wednesday, Jul 12, 2017 at 18:52

Wednesday, Jul 12, 2017 at 18:52
Give the man a medal !!
Easy, cheap solution and no thinking or things to do....except remembering to turn the charger back on !!
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Follow Up By: Member - bungarra (WA) - Wednesday, Jul 12, 2017 at 20:19

Wednesday, Jul 12, 2017 at 20:19
Yes Hoyks...
yes that is what I can do....but I like to solve the issue......not go around it...that's just me :)
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