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Old 07-12-2013, 09:43   #16
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Re: ICOM 802 Power Draw When Off

Thanks ,that answers my question.
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Old 07-12-2013, 09:43   #17
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Re: ICOM 802 Power Draw When Off

Quote:
Originally Posted by steve77 View Post
.....Trayfor, by "dropped ground", do you mean an inadvertent connection of the ground wire to DC positive? I'm just not familiar with the terminology......Steve
"dropped ground" means an inadvertent break in the ground circuit of an installed device. This can happen due to some fault in the device, to physical damage, to corrosion, loose connections, etc.

Example:

Somehow the NEG cable to your starter/engine gets broken. You try to start the engine. As seen by the starter solenoid, the only path to the negative pole of the battery is thru the engine, back to a common ground point, back up thru a radio ground wire, then thru the radio chassis down the negative cable to the battery.

When you press "Start", the starter tries to draw upwards of 150-200 amps thru the radio ground/neg cabling.

This example won't happen with all radios....some of them have chassis insulated from the negative power terminal....but it could happen with any device connected both to the boats ground and the battery negative terminal.

Rather than worry about this and try to trace out all circuits which could possibly create this condition, it's much better just to install a proper fuse in the negative as well as the positive cabling to the radio.

Bill
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Old 07-12-2013, 10:00   #18
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Re: ICOM 802 Power Draw When Off

Thanks for the explanation, Bill.

Steve
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Old 07-12-2013, 14:21   #19
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Re: ICOM 802 Power Draw When Off

Sven,
As usual Bill (btrayfors) has given you some great answers/information...heed it...

Now specific to your questions...
Quote:
Originally Posted by SvenG View Post
One of the reasons why ICOM tells you to connect the ICOM directly to the battery instead of through a breaker has to do with the crystal oven.

What I'm wondering is what current draw that oven imposes. It's nice that the radio is always warmed up and ready to go but I'm not sure that our all-solar budget is happy about the constant drain. I don't want to install a switch if the draw is miniscule, but our power budget seems to have suffered ever since the installation.
1) The Icom M-802 draws VERY little power when Off ("Stand-by")....approx. 1/10 of an amp....and most other commercial HF radios have the same / similar power draw to maintain their frequency stability, as well...

Icom mentions this specifically in their M-802 manual, so that owners/installers do NOT switch off the DC power to the radio (thereby preventing the radio from meeting the prescribed frequency stability specs), as well as to properly inform those on smaller vessels with limited electrical power and/or limited charging capability, of the small power draw of the radio even when turned Off...


2) The actual power draw when turned Off, is VERY small....at 100ma to 120ma....that is 1/10 of an amp!!!
And over a 24 hour period, that represents 2.4 A/H per day!!! (less than one night's use of an LED anchor light...less than most GPS receivers, etc...)


3) If you're having energy budget issues since installing your M-802, it might be because of how much you are using the radio, or maybe completely unrelated to your M-802 use...
But, it is almost certainly NOT the small (2 A/H, per day) power use of the radio when turned Off!!

BTW, here are some of the power draws (I measured myself, on-board, a few years ago) of my M-802....
Normal SSB RX / Max Vol = 2.1 amps
Normal SSB RX / Avg Vol = 2.0 amps
DSC Watch Mode / bright display = 1.9 amps
DSC Watch Mode / dim displat = 1.8 amps
Turned OFF / Standby = ~0.1amps (~ 100 - 120ma)


4) If you did not have a solar array, and were laying-up on the hard, etc. for a season....then, Yes, disconnect/unplug the DC power from the M-802...
But, for day-to-day us, or even week-to-week use, most will not find an additional 2.4 amps per 24 hour period to impact their energy budget at all...
(This additional power draw added to your daily energy budget, is like removing 7 watts of solar....on most boat's with a decent sized solar array, the difference of 7 watts can be like wiping some dust off the panels!!)

Not sure where in Mexico you are now, but remember the sun is lower in the sky this time of year here in the Northern Hemisphere!!! Dec 21st (the winter solstice) is just 2 weeks away!!!
And, remember that the amount of energy that solar panels produce is dependent on their angle to the sun and the number of hours of sunlight daily...
So, wintertime means LESS solar output!!!
Again, I'm not sure where you are at, nor what your solar array consists of....but I suspect that now being wintertime has a LOT more to do with your solar array not keeping up with your on-board power use, than the addition of the M-802's power draw when tuned Off!!



I hope this helps..

Fair winds..

John
s/v Annie Laurie
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Old 07-12-2013, 15:01   #20
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Re: ICOM 802 Power Draw When Off

Quote:
Originally Posted by steve77 View Post
Apologies to the OP, not meaning to hijack this thread.
No problem, it's a useful discussion.

Quote:
If no one else has posted the result by then, I'll let everyone know what I find.
It seems as if Wotname recalled right when he said it was on the order of 0.1 A.

We haven't plugged into shorepower once after casting off the lines on May 15th 2012 and we have only run the engine a half dozen times since to help the solar panels. That's 19 months with solar running the fridge, the water maker, heatgun, other powertools, computers, GPS, radios, lights ... when I saw that our spectacular new radio had its oscillator in an always-on oven I started worrying.

We can live with 2.5-3 AH/day.



-Sven
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Old 07-12-2013, 16:58   #21
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Quote:
Originally Posted by btrayfors View Post

"dropped ground" means an inadvertent break in the ground circuit of an installed device. This can happen due to some fault in the device, to physical damage, to corrosion, loose connections, etc.

Example:

Somehow the NEG cable to your starter/engine gets broken. You try to start the engine. As seen by the starter solenoid, the only path to the negative pole of the battery is thru the engine, back to a common ground point, back up thru a radio ground wire, then thru the radio chassis down the negative cable to the battery.

When you press "Start", the starter tries to draw upwards of 150-200 amps thru the radio ground/neg cabling.

This example won't happen with all radios....some of them have chassis insulated from the negative power terminal....but it could happen with any device connected both to the boats ground and the battery negative terminal.

Rather than worry about this and try to trace out all circuits which could possibly create this condition, it's much better just to install a proper fuse in the negative as well as the positive cabling to the radio.

Bill
This really doesn't make sense. Firstly the radio neg is connected to the battery how is there a connection via the engine common point ( a stupid idea anyway ) the fact is if you adopt that line of thinking you could load dump through almost any neg return.

Dave
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Old 07-12-2013, 17:10   #22
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Re: ICOM 802 Power Draw When Off

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Originally Posted by goboatingnow View Post
This really doesn't make sense. Firstly the radio neg is connected to the battery how is there a connection via the engine common point ( a stupid idea anyway ) the fact is if you adopt that line of thinking you could load dump through almost any neg return.

Dave
I think it makes sense only when the chassis of the radio is also connected to "ground". This is the usual case when say the radio is mounted in a vehicle as the the chassis is almost always affixed to the metal body of the vehicle.

Another instance is when the radio chassis is directly mounted to body of a metal boat or installed in a radio cabinet that is grounded to the metal superstructure of the vessel.

If the radio chassis is not somehow connected back the battery negative, then as you rightly assert, there is no return path.

I don't believe protecting the -ve lead is a issue when the chassis is floating (as I expect is the case for most small boat users).
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Old 07-12-2013, 17:16   #23
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Originally Posted by Wotname View Post
I think it makes sense only when the chassis of the radio is also connected to "ground". This is the usual case when say the radio is mounted in a vehicle as the the chassis is almost always affixed to the metal body of the vehicle.

Another instance is when the radio chassis is directly mounted to body of a metal boat or installed in a radio cabinet that is grounded to the metal superstructure of the vessel.

If the radio chassis is not somehow connected back the battery negative, then as you rightly assert, there is no return path.

I don't believe protecting the -ve lead is a issue when the chassis is floating (as I expect is the case for most small boat users).
Only an idiot engineer would design an exposed case connected to DC negative. This is because you could create unintended DC return paths , both causing unexpected return current paths and very bad ground loops. Case earth is a seperate thing altogether.

I don't see byrayfors explanation as valid. If it were so you would have to protect every common DC return wire. Furthermore you could create a dangerous situation where the radio d. Return went through the case via an unintended path.

None designs like that

Dave

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Old 07-12-2013, 17:23   #24
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Re: ICOM 802 Power Draw When Off

Quote:
Originally Posted by goboatingnow View Post
Only an idiot engineer would design an exposed case connected to DC negative. This is because you could create unintended DC return paths , both causing unexpected return current paths and very bad ground loops. Case earth is a seperate thing altogether.

I don't see byrayfors explanation as valid. If it were so you would have to protect every common DC return wire. Furthermore you could create a dangerous situation where the radio d. Return went through the case via an unintended path.

None designs like that

Dave

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You may be right about idiot engineers but many many steel boats (small ones anyway) have the hull connected to DC -ve;, just like all cars do. Simply a fact of life. Also many (but not all) radios have the case connected to the DC -ve inside the unit - again a fact of life.

Many commercial mobile radios fitted to vehicles now call for protecting (fusing) the -ve lead (as well as the +ve) because it can be an issue.

It is just one more may to protect us from the said idiot engineers I guess.
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Old 07-12-2013, 17:38   #25
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You may be right about idiot engineers but many many steel boats (small ones anyway) have the hull connected to DC -ve;, just like all cars do. Simply a fact of life. Also many (but not all) radios have the case connected to the DC -ve inside the unit - again a fact of life.

Many commercial mobile radios fitted to vehicles now call for protecting (fusing) the -ve lead (as well as the +ve) because it can be an issue.

It is just one more may to protect us from the said idiot engineers I guess.
The primary reason you fuse a large negative wire connected to a battery is to prevent it for acting as a short circuit return in the case of a unfused positive fault. A small cable will self fuse in effect , but a big negative cable will not and severe damage to a battery , fire , venting could result.

It's got nothing to do with case connections.

I'd still love to see a design that deliberately connects an exposed case to DC neg.

Cars are slightly different in that some deliberately use the body as a DC return path , different issue entirely.

Equally the steel boat issue. Different issue.

I remember the odd student engineer making the heat sinks on audio amps dc neg all right but its very bad practice. I'd love to see the equipment you mentioned. Potentially very dangerous to allow DC negative to connect to a case ( imagine two cases touching one with a 5a return neg and the other with a 40 a. !!!! ) like I said of that was the case you'd have to fuse every negative on the boat.

The fact is its not the case.

Note this is not the same as a case lug connection.


Dave
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Old 07-12-2013, 18:01   #26
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Re: ICOM 802 Power Draw When Off

A metal boat, if not completely isolated from dc -ve, will have one connection point and one only. The one connection point will be at or very near the -ve bus. That is unless one wants the boat to disintegrate quite quickly due to stray electrical currents.
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Old 07-12-2013, 18:04   #27
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A metal boat, if not completely isolated from dc -ve, will have one connection point and one only. The one connection point will be at or very near the -ve bus. That is unless one wants the boat to disintegrate quite quickly due to stray electrical currents.
I would argue as many do that a steel boats hull should be completely isolated from DC negative. This is definitely the practice in aluminium hulls

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Old 08-12-2013, 10:47   #28
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Re: ICOM 802 Power Draw When Off

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I'd still love to see a design that deliberately connects an exposed case to DC neg.
The M802 is just one of many that comes to mind.

Eric
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Old 08-12-2013, 14:45   #29
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Re: ICOM 802 Power Draw When Off

Yep, Eric nailed it!

I've been following this thread with some amusement at the learned discourse re: dumb engineers who design radios with the chassis connected to the negative power connection for the radio.

Fact is, MOST if not all ham radios, marine radios, military radios, land-mobile radios, etc. do in fact have such a connection, i.e., there is a dead short between the -VE power connector and the chassis.

Whether this is the result of brain-dead engineers or not I can't tell you, but I CAN tell you that the sampling of such radios in my workshop/ham shack ALL had their chassis connected to the DC negative power lug.

Bill
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Old 08-12-2013, 17:30   #30
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Re: ICOM 802 Power Draw When Off

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Originally Posted by goboatingnow View Post
.......

I'd still love to see a design that deliberately connects an exposed case to DC neg.
.......
Just to add to Bill & Eric's observations, I would love see one where it isn't connected.

Oh sure, I bet there are some out there but I have yet to see one.
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