installing an ammeter
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Senior User
Joined: Oct 2004
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installing an ammeter
I have a 2005 F350 6l diesel and have no guage to monitor the charging system. As a result I have been caught with low battery more than once and on another occasion had the truck dead at the side of the road due to a bad alternator.
I want to install an ammeter to keep an eye on things. My question is, " What brand works well and looks good, where do I hook it up, and where is a good place to mount it?" Thanks for any help and everyone have a great New Year.
I want to install an ammeter to keep an eye on things. My question is, " What brand works well and looks good, where do I hook it up, and where is a good place to mount it?" Thanks for any help and everyone have a great New Year.
Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
Ammeters are a pain, you have to have a shunt wired in on the alternator charge wire. A voltmeter would give you nearly the information without having to place a shunt on the charge wire. If the Alt isn't producing 13+ volts, then it's having trouble charging. Plus the volt meter will let you see the condition of the battery when the alternator is off. If you get below 11v, you're going to have trouble re-starting.
Cargo Master
Joined: Jun 2008
Posts: 2,752
Likes: 5
From: Stillwater, OK
Not very many people take the time to set them up anymore, but if you want one more bit of information about your charging system, and don't mind the hastle of installing an ammeter, they are worth it (IMO).
The ammeter goes on the charge wire between the alternator and the battery. It will show you if your alternator is charging your battery (reading on the + side), if the battery is charged (reading at 0), or if the current draw is more than your alternator can supply (reading on the - side).
A reading on the - side can indicate either a bad alternator or that you are trying to use too many accessories.
The ammeter goes on the charge wire between the alternator and the battery. It will show you if your alternator is charging your battery (reading on the + side), if the battery is charged (reading at 0), or if the current draw is more than your alternator can supply (reading on the - side).
A reading on the - side can indicate either a bad alternator or that you are trying to use too many accessories.
Lead Driver
Joined: May 2003
Posts: 9,303
Likes: 48
From: Lyndonville, Vermont
I suppose there are two types of amp meters. One with a shunt and one you wire direct by cutting into the main alt wire.. You would want the shunt type so you don't have to run monster cable to the dash..I havn't done an amp meter in years. We used to just cut the wire and extend it all the way to the dash and back and reatach....
Dick
Dick
Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
Ammeters are usually pretty low amperage, modern alternators are in 100-300 amp range, it's a lot of current to pass through a meter when you can just check the voltage drop through a shunt and make a cheaper meter. I've seen some meters that could handle that amperage, but they were huge, not the kind of thing I would want in the dash.
Out of curiosity, how many amps did those old ones read without a shunt?
Out of curiosity, how many amps did those old ones read without a shunt?
Cargo Master
Joined: Jun 2008
Posts: 2,752
Likes: 5
From: Stillwater, OK
it depends on how much you want to pay for one...
you can find them in +/-30, 60, 80... There is probably a 100 out there somewhere, too.
if the ammeter is hooked between the battery and the alternator it won't ever have that many amps running through it unless the alternator completely goes out and the engine is being run off of the battery. It wasn't really a problem on those old pickups... the coil, and radio aren't that much of a current draw.
you can find them in +/-30, 60, 80... There is probably a 100 out there somewhere, too.
if the ammeter is hooked between the battery and the alternator it won't ever have that many amps running through it unless the alternator completely goes out and the engine is being run off of the battery. It wasn't really a problem on those old pickups... the coil, and radio aren't that much of a current draw.
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Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
You need to explain that a little better. The alternator makes the power that keeps the battery charged. The battery is only hold current for reserve and restarting. The rest of the time the engine is running and the alt is producing enough amperage to keep the battery charged and everything running. On modern vehicles, that could be 150amps while the battery is recharged from starting/sitting over night. The stock Superduty Alt was 110 or 130 amps, so I would suggest not going any lower 130a.
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Cargo Master
Joined: Jun 2008
Posts: 2,752
Likes: 5
From: Stillwater, OK
130a is the load that the alternator is capable of running without help.
there will never be 130a traveling between the alternator and the battery...even if the battery is dead (the alternator is supplying the current for the engine and accessories to run, too)
An ammeter is generally used to check to see if the battery is being charged or discharged.
now, if you want to use an ammeter to be able to check the load on the alternator, it is necessary to find one that can measure the full capability of the alternator.
there will never be 130a traveling between the alternator and the battery...even if the battery is dead (the alternator is supplying the current for the engine and accessories to run, too)
An ammeter is generally used to check to see if the battery is being charged or discharged.
now, if you want to use an ammeter to be able to check the load on the alternator, it is necessary to find one that can measure the full capability of the alternator.
Former ******
Joined: Nov 2004
Posts: 4,901
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From: Salt Lake City, Utah
I would vote not to have an ammeter. A standard volt meter gives a better idea about the health of the charging system, including battery health. Ammeters are generally not used any more because the information they give is generally not that useful. It takes voltage to turn over the starter motor, and regardless of how many amps you have available, if you can't give it the voltage, it won't start. As mentioned, a quick glance at the voltmeter can tell you what is going on. If the voltage is below 12.8V with the key on/engine off, either the battery is weak/not taking a charge, the connection at the posts is poor, or the alternator is not working properly. If the voltage is above 13V when the engine is running, the alternator is working just fine. If the needle bounces around, then the connections are poor, or the diode packs in the alternator are starting to go. If you have any other problems, a quick stop by the auto parts store for a complete charging system checkup can tell you if anything is not right, and having that done is free.
Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
If it wasn't for having a shunt, I would like to see if my 230amp alt is putting out full current while using my winch. Voltage can give you a decent approximation, but it still would be cool to see it.
A battery has 6 2.1v cells, so the voltage key on, engine off should be 12.6 or there about. There is a mili-amp draw so over time, you will have a voltage drop, probably down to 12.1 or so and still have a good battery. When it drops under 11v, is when the trouble is supposed to start.
A battery has 6 2.1v cells, so the voltage key on, engine off should be 12.6 or there about. There is a mili-amp draw so over time, you will have a voltage drop, probably down to 12.1 or so and still have a good battery. When it drops under 11v, is when the trouble is supposed to start.
Fleet Mechanic
Joined: Feb 2007
Posts: 1,852
Likes: 39
It's not THAT big a deal to install a shunt and wire up a true ammeter. If you wanted to get fancy, you could have a shunt and a voltage divider, and use a switch with a single panel meter to select whether you wanted to view current or voltage. Or, just have two meters.
I found a heavy-duty shunt, I think it was 500A, and put it in series with my winch cable. Then I used LED bar-graph chips to make a segmented display, showing the true current that the winch was drawing. I think I set up the range to be 0 to 400 Amps. This is pretty cool to have, because it gives you a direct indication of just how hard the winch is pulling at any given moment.
I found a heavy-duty shunt, I think it was 500A, and put it in series with my winch cable. Then I used LED bar-graph chips to make a segmented display, showing the true current that the winch was drawing. I think I set up the range to be 0 to 400 Amps. This is pretty cool to have, because it gives you a direct indication of just how hard the winch is pulling at any given moment.
FTE Leadership Emeritus
Joined: Jul 2002
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From: Long Island USA
An ammeter doesn't tell you much about the current state of your batteries, just what the alternator is charging at, or how much drain you are putting on them.
A volt meter, especially with the engine NOT RUNNING would tell you more about the batteries than an ammeter will.
Of course, both would be nice. But again, a volt meter does more (to me) than anything else.
A volt meter will tell you how good the batteries are BEFORE you start, will tell you how much the batteries are charged (over 14 volts means just about 100% fully charged) and it will tell you how much drain you have on the batteries. If you are dropping back towards 12 volts, you are maxing out the alternator.
A volt meter, especially with the engine NOT RUNNING would tell you more about the batteries than an ammeter will.
Of course, both would be nice. But again, a volt meter does more (to me) than anything else.
A volt meter will tell you how good the batteries are BEFORE you start, will tell you how much the batteries are charged (over 14 volts means just about 100% fully charged) and it will tell you how much drain you have on the batteries. If you are dropping back towards 12 volts, you are maxing out the alternator.
Lead Driver
Joined: Sep 2007
Posts: 8,180
Likes: 669
From: Scio, OR
There is another issue with installing an amp meter on a 6.0L. If it's like mine anyway.
On the passenger side battery is the wire that goes from the battery to the alternator. That's all it does is carry alternator current to the batteries.
The main feed into the CJB is another heavy wire coming from the drivers side battery. In order to connect an amp meter in such a way as to properly measure battery charge, you'd have to re-wire the truck so that their was a single point where power went into and out of the batteries.
If you just connected the amp meter to to the alternator wire, you'd see a significant "charge" at all times, since the engine (at least mine) draws about 50 amps off of the alternator at idle.
On the passenger side battery is the wire that goes from the battery to the alternator. That's all it does is carry alternator current to the batteries.
The main feed into the CJB is another heavy wire coming from the drivers side battery. In order to connect an amp meter in such a way as to properly measure battery charge, you'd have to re-wire the truck so that their was a single point where power went into and out of the batteries.
If you just connected the amp meter to to the alternator wire, you'd see a significant "charge" at all times, since the engine (at least mine) draws about 50 amps off of the alternator at idle.