Battery fuses

[digitalanalog]

And never ever use the chassis near the radio as an earth... aaargh!

Why Not?

 

[N_Jay]

Why Not?

Because they don't like to.

In reality, it typically does not cause any issues.

BUT, that being said once you do go directly to the battery, it is proper to install a fuse in the ground lead.

 

[richardc63]

Why Not?

Have you ever looked under the floor vinyl in a 10+ year old truck (particularly fire trucks)? Dirt, moisture and corrosion... all makes for an unreliable connection along with possible RFI issues. Why take such a short cut when you can do it properly in the first place? Our trucks have a planned lifespan of 20 years- and so should the radio installation (even if the radio itself lasts only 10 years).

Cheers,

Richard

 

[N_Jay]

Have you ever looked under the floor vinyl in a 10+ year old truck (particularly fire trucks)? Dirt, moisture and corrosion... all makes for an unreliable connection along with possible RFI issues. Why take such a short cut when you can do it properly in the first place? Our trucks have a planned lifespan of 20 years- and so should the radio installation (even if the radio itself lasts only 10 years).

Cheers,

Richard

Yes, but all the other electronics rely on the chassis ground.

I would hope that a good radio tech would know how to get a chassis ground that is well protected from corrosion.

I am not saying a battery ground is better or worse, there are pros and cons of both methods.

For some deep thought on why a close by chassis ground could be better, ask yourself;
"Where is the RF ground?".
Then ask yourself;
"Could I be creating paths for ground loops?"

Remember, for any task there is often more than one "right" way, and almost infinitive "Wrong" ways!

Have fun.

 

[kb0nly]

Its a pretty simple thing to explain, i see others have already said the same thing, but to further explain, again....

You will see that most if not all Ham Radio gear is sold with a fuse in the negative lead. Is it needed? Yes and No...

Yes: If you install it as the manual suggests and connect the negative lead directly to the battery then leave that fuse in the negative lead. Why? If the ground from the battery to the body/frame/engine of the vehicle failed all of the vehicles power load still needs a ground, your radio becomes a path to the battery ground. The fuse pops and saves the radio.

No: If you install it as you should in my opinion, the ground lead should be grounded to the body/frame of the vehicle at its mounting location. Now if the vehicle ground fails your radio is at the same potential as all the vehicle electronics, it has no ground and no power, no issues.

Why do they put that fuse in and suggest you connect it directly to the battery then? Well it can eliminate some noise in the receiver, and others think its a better connection, but in my opinion just do it the right way and bond to the body/frame at the radio. Motorola, GE, they have been installing their commercial gear this way for what 50 years? It's standard practice.

 

[richardc63]

Yes, but all the other electronics rely on the chassis ground.

I would hope that a good radio tech would know how to get a chassis ground that is well protected from corrosion.

I am not saying a battery ground is better or worse, there are pros and cons of both methods.

For some deep thought on why a close by chassis ground could be better, ask yourself;
"Where is the RF ground?".
Then ask yourself;
"Could I be creating paths for ground loops?"

Remember, for any task there is often more than one "right" way, and almost infinitive "Wrong" ways!

Have fun.

When you operate large fleets of vehicles (as we do) over a large area you learn not to assume that there always will be a good radio tech & sometimes installers may be just auto electricians. You have to set a standard that is conservative & easily repeated by anyone. Going back to the battery, fusing at the battery, or taking it back to some other clean & secure point (such as an under bonnet fuse box) is a lot more likely to be reliable than using a chassis ground.

It isn't a question of right or wrong, just which is the better. You learn that from experience, sometimes bitter. That is why we & many other major radio fleet users adopt this installation practice. But hey if you want to use a chassis ground for your installs- fine. Just don't come & do that to ours!

Cheers,


Richard

 

[N_Jay]

When you operate large fleets of vehicles (as we do) over a large area you learn not to assume that there always will be a good radio tech & sometimes installers may be just auto electricians. You have to set a standard that is conservative & easily repeated by anyone. Going back to the battery, fusing at the battery, or taking it back to some other clean & secure point (such as an under bonnet fuse box) is a lot more likely to be reliable than using a chassis ground.

It isn't a question of right or wrong, just which is the better. You learn that from experience, sometimes bitter. That is why we & many other major radio fleet users adopt this installation practice. But hey if you want to use a chassis ground for your installs- fine. Just don't come & do that to ours!

Cheers,


Richard

Yep, like I said, lots of right ways, and MANY MANY more wrong ways.

Just remember to start checking chassis grounds when the ground fuse pops.

 

[richardc63]

Why do they put that fuse in and suggest you connect it directly to the battery then? Well it can eliminate some noise in the receiver, and others think its a better connection, but in my opinion just do it the right way and bond to the body/frame at the radio. Motorola, GE, they have been installing their commercial gear this way for what 50 years? It's standard practice.

Who in Moto do it that way? They don't do it that way here in Sydney- Moto install as per our instructions. It isn't "standard" practice at all. You might say it is common practice, though I would even dispute that, but it certainly is not standard practice by any agency over here I know of. Don't assume your way is the only way any more than I do- the bottom line is the customer determines the "standard" and if you are happy to use the chassis then that is your business. It wouldn't be acceptable to us.

Richard

 

[richardc63]

Yep, like I said, lots of right ways, and MANY MANY more wrong ways.

Just remember to start checking chassis grounds when the ground fuse pops.

N Jay,

Absolutely- but to my knowledge it never has happened to us. Earth loops in our vehicles are a serious concern but to my knowledge this problem has not reared its head in 400ish appliances. Our biggest problems are underrated inverters etc due to firefighters wanting more & more technology in the truck... another problem entirely.

Richard

 

[N_Jay]

Who in Moto do it that way? They don't do it that way here in Sydney- Moto install as per our instructions. It isn't "standard" practice at all. You might say it is common practice, though I would even dispute that, but it certainly is not standard practice by any agency over here I know of. Don't assume your way is the only way any more than I do- the bottom line is the customer determines the "standard" and if you are happy to use the chassis then that is your business. It wouldn't be acceptable to us.

Richard

Standard practice with the old "Trunk Mount" radios was to ground to the chassis.
The ground lead in the wiring kit was noticeable shorter than than hot lead, and never had a fuse.

At some point more radios (even trunk mount variants) became more like dash mount radios, and the cable kits changed to where both leads were the same length and the negative got a fuse.

No "Rights" no "Wrongs", just "Differences"!

 

[N_Jay]

N Jay,

Absolutely- but to my knowledge it never has happened to us. Earth loops in our vehicles are a serious concern but to my knowledge this problem has not reared its head in 400ish appliances. Our biggest problems are underrated inverters etc due to firefighters wanting more & more technology in the truck... another problem entirely.

Richard

The problem we saw was bad box ground straps on ambulances cause the whole box to be grounded through the radio.

 

[richardc63]

The problem we saw was bad box ground straps on ambulances cause the whole box to be grounded through the radio.

This is probably sidetracking from the original question but I thought someone might be interested in how our fire appliances are wired. We have over 400 so they aren't going to all be the same but there are a few basic "rules" we have.

They all have an auxiliary "Comms" battery, usually around 12-17AH, which is float charged off the main battery. It is isolated so that if all power to the truck electrics is lost the radio should always work for long enough to get a call out. Most modern trucks are 24V so this is supplied through a 24-12V converter. The battery is in most cases located close to the radio. In the earlier trucks that have no operator console the radio is wired directly to this battery with fuses at the battery (both pos & neg). In more modern trucks, which is the overwhelming majority, there is a Comms control pod containing the inverter, DC distribution & isolation, and individual fused outputs, controlled from a central operators console. There is a very heavy strap bonding this pod to the battery earth of both batteries, as well as the chassis. The radios are mounted in this enclosure.

If anyone is interested let me know & I might be able to dig up an electrical diagram showing this.


Richard

 

[kb0nly]

Who in Moto do it that way? They don't do it that way here in Sydney- Moto install as per our instructions. It isn't "standard" practice at all. You might say it is common practice, though I would even dispute that, but it certainly is not standard practice by any agency over here I know of. Don't assume your way is the only way any more than I do- the bottom line is the customer determines the "standard" and if you are happy to use the chassis then that is your business. It wouldn't be acceptable to us.

Richard

Everyone, if you don't then fine, but read the manual like most installers do before you claim i don't know what i am talking about or that NOBODY does it. Have you ever looked at the install manual for a Motorola mobile? I have many service and install manuals here, all of them show grounding the radio at its installation location, to the chassis/frame of the vehicle.

If they don't do it in Sydney then i guess thats one place in the world they don't. Here in the USA they follow a common practice. I haven't worked on any commercial installs yet where the ground went all the way back to the battery, thats just stupid. I have seen one installed in this manner, the ground became intermittent at the battery and the radio was using its antenna mount as a ground, disconnect the coax and the radio went off, hmm thats odd, look at the battery and find the rotted off cable, well there's your problem. Cut the ground at the radio installed a ring terminal and grounded it to the body/chassis and all better.

If you do it right there is nothing wrong with it, and if you put a ground to the battery on any of my installs that wouldn't be acceptable to me as its rediculous.

 

[richardc63]

Everyone, if you don't then fine, but read the manual like most installers do before you claim i don't know what i am talking about or that NOBODY does it. Have you ever looked at the install manual for a Motorola mobile? I have many service and install manuals here, all of them show grounding the radio at its installation location, to the chassis/frame of the vehicle.

If they don't do it in Sydney then i guess thats one place in the world they don't. Here in the USA they follow a common practice. I haven't worked on any commercial installs yet where the ground went all the way back to the battery, thats just stupid. I have seen one installed in this manner, the ground became intermittent at the battery and the radio was using its antenna mount as a ground, disconnect the coax and the radio went off, hmm thats odd, look at the battery and find the rotted off cable, well there's your problem. Cut the ground at the radio installed a ring terminal and grounded it to the body/chassis and all better.

If you do it right there is nothing wrong with it, and if you put a ground to the battery on any of my installs that wouldn't be acceptable to me as its rediculous.

Hey if you are happy with your way of doing it then what ever rocks your boat... but I answered the question in terms of how we, and other major Australian emergency services wire their radios. But hey you know best... and what you described as happening at the battery terminal can & does happen when you terminate the negative hidden under the floor in an often damp/dirty location (when you can more easily terminate and water/dirt proof the connection at the battery). What you described is poor maintenance, not a poor installation.

And the word is ridiculous, not rediculous. It is a question of what is the best way of doing it, and I wouldn't be so "rediculous" as to suggest my way is the only way.

Happy New Year to all.


Richard

 

[digitalanalog]

Everyone, if you don't then fine, but read the manual like most installers do before you claim i don't know what i am talking about or that NOBODY does it. Have you ever looked at the install manual for a Motorola mobile? I have many service and install manuals here, all of them show grounding the radio at its installation location, to the chassis/frame of the vehicle.

If they don't do it in Sydney then i guess thats one place in the world they don't. Here in the USA they follow a common practice. I haven't worked on any commercial installs yet where the ground went all the way back to the battery, thats just stupid. I have seen one installed in this manner, the ground became intermittent at the battery and the radio was using its antenna mount as a ground, disconnect the coax and the radio went off, hmm thats odd, look at the battery and find the rotted off cable, well there's your problem. Cut the ground at the radio installed a ring terminal and grounded it to the body/chassis and all better.

If you do it right there is nothing wrong with it, and if you put a ground to the battery on any of my installs that wouldn't be acceptable to me as its rediculous.

I agree.