Best use of digital ammeter?

[ginga]

So I'm coming to the end of all my van's electrical work.  The last thing I need to hook up is an ammeter.  Specifically this one here: 

https://www.amazon.com/dp/B013PKYIL...QJ64BT7BRM804PXK1&ie=UTF8&qid=1488977982&sr=1

I'm just having trouble discerning the best setup for this, especially considering that I technically have 2 loads.  I have a fuse block which connects two lights, a fridge, and a fan to the batteries.  Then I have a power inverter connected to the batteries.  Sure I could buy a second ammeter, but that's not really an option right now.  I'm also feeling torn about which group of power would be best to monitor...do I want to monitor the power from the fuse block or do I want to see how much comes and goes from my inverter?  

I have a set of cables from my inverter - a negative and positive, lug on one end and a clamp on the other.  I don't suppose I could wire up the ammeter and then use the alligator clips to snap on to different loads at will could I?  Sure this wouldn't give me 100% consistent information, and it would be less safe so I wouldn't want to leave them clamped all the time but would that be a viable option for this dilemma?  Or maybe I ought to just get it wired to the fuse block, seems like that'd be using the most.

 

[reflex439]

I have the same meter. Mine is hooked up to a shunt at the battery bank itself, so it measures all loads on the battery, regardless if its from the 12V or inverter sections. Basically, it will monitor what is pulled out of the battery until you reset it, the current load (12v, 120V, or both if the inverter is on), current voltage, etc. I use it as sort of a fuel gauge, knowing how many watt hours (labeled energy on the meter) I can use out of the battery bank for both 12V and inverter use before I need to recharge.

I.e., if I can safely pull 900Wh out of the battery leaving it at 50% charged, then I reset the meter when I know the battery is fully charged and know I can wait until around 900Wh before I need to recharge again. I also monitor the voltage and current to assess the battery charge status as a secondary indicator, and the current to know how much I’m using at that given moment.

It takes a little effort to calibrate the readings with your battery setup to know how many Whs you’re battery will deliver before reaching your lowest desired charge level, and what the voltage actually means at a given current level. To help assess the batter charge condition, I always check the voltage under a 4aHr current to be consistent. The voltage will vary based on the load pulled off the battery, so reading the voltage under a specific load will give you more consistent results. I turn on the fantastic fan to high, inverter on (idle load), and the stove top range fan and halogen light (all other lights are LED). This gives me my ~4aHr load.

You can adjust the high and low voltage alarms (basically, the LED display blinks on and off as the alarm). Mine is set for 14.8v on the high end, and 11v on the low end. The high end is a reasonable setting and never seems to go off. The low setting is kind of pointless. Since the voltage will vary a lot under high to low loads, there is no reasonable setting that works for both. If you set it at say 12V, under high short loads it will go off constantly, but would be fine for low current loads. If you set it for the high current loads, a low current load will easily bring your battery to near exhaustion before going off. If you have a more constant load, you could find a reasonable setting to work well. But in an RV with such varying loads, it’s not to useful. Best to monitor the wHs used, and the voltage reading under a constant and repeatable load.

I’ve run the wiring from the battery to where the meter is installed, which is about 20’ of small gauge wiring, so it appears there is no issue with distance across the RV. Its a 4 wire setup.

I hope this helps.

 

[highdesertranger]

yes the shunt goes on the negative battery cable, no other grounds go between the shunt and the battery. does that meter measure both ways? amps in and amps out. highdesertranger

 

[John61CT]

At that price can put one on all big load consumers.

Just take the amp ratings with a grain of salt.

Total nother level of cost and complexity, but I've been checking out Bogart Engineering line of coulomb counters, and their Pentametric supports logging multiple shunts from one central monitor.

 

[SternWake]

I would be interested in how accurate one of those are.


I had an Ammeter only that used the same 100 amp shunt, and while it could be calibrated, when calibrated at 4 amps, 40 amps was 5 outta whack, when calibrated at 40 amps then 4 actual amps read as 1.2 amps.

Had to do a shoulder shrug and just know it was a general range, not precise.

I have a blue skies IPN pro remote battery monitor that uses the 500 amp 50Mv deltec shunt, and this is accurate as far as amp readings, but as far as amp hour counting and how it relates to actual state of charge, it drifts as the battery is turning some amperage into heat.  When amps taper to 0.4 at 14.7v, which is 100% on my AGM battery, the AH from full screen does not always agree.  It is usually close, but rare that it goes to 0 from full at te same time amps taper to 0.4.

Take the readings with a large grain or 200 of salt.

Shunts usually HAVE to go on the (-)

this hall effect ammeter (not an ah counter) can be slid over either single wire, but its resolution is only 0.2 amps

https://www.amazon.com/bayite-Digital-Current-Voltage-Transformer/dp/B01DDQM6Z4

 

[John61CT]

For SoC accuracy I hear nothing beats SmartGauge, marketed and well-supported in the Americas by Balmar.

At least lead-based banks, not LFP.

In conjunction with SmartPass, can isolate/combine via relays.

With the SG or the best shunt-based coulomb counters, real-time SoC calc is a bit of a black art, within 3-5% accuracy is good as you're going to get.

And the SG has no ammeter, just SoC, so I'll be getting a Bogart coulomb counter as well.

 

[reflex439]

I never calibrated mine as I honestly don't care what the numbers are. Only real concern is that it gives me a better picture of where I am in the battery capacity scale over the typical 4 Green, Yellow, Red leds on most cheap monitors that only measure the voltage. Instead of watt hour measurement, they could call them charge units for all I care. As long as I know xxxx units used puts me around 50%, I'm good to go, and this meter does that for me. I reset it after a full charge.

I did measure the voltage and it matched with my digital voltmeter. I did not measure the current, as again, I really don't care if its accurate to actual amp hour measurements. As long as I can see I'm pull 2aHrs vs 5aHrs, I don't mind if its actually 3aHrs vs 6aHrs, or 1aHrs vs 4aHrs. I know if it usually says 2.5aHrs when the fan and tv are on, then things are normal. If it says 5aHrs, then I'll go looking for something somewhere that I may have left on.

highdesertranger, thats how mine is hooked up. And no, it does not measure anything put back in, just taken out. When the battery is on charge, it reads the voltage, but the load is 0 even when I have a load on. I don't know if I exceed the capacity of the charger with an excessive load if the delta would show up.

It's not perfect. But its inexpensive and is a repeatable and accurate way to judge where I am in the battery curve, and when I high low vs high current loads happening.

 

[Weight]

I have a victron pmv-700. It monitors amps both directions. It has to be re-calibrated occasionally. Easy to do. All my negatives go to a bus bar and the bus bar connects to the shunt. As this measures both directions, the charger negatives also go to the bus bar. The other side of the shunt has the battery negatives. All negatives must go through the shunt or they are not measured.

 

[ginga]

I have the same meter. Mine is hooked up to a shunt at the battery bank itself, so it measures all loads on the battery, regardless if its from the 12V or inverter sections. Basically, it will monitor what is pulled out of the battery until you reset it, the current load (12v, 120V, or both if the inverter is on), current voltage, etc. I use it as sort of a fuel gauge, knowing how many watt hours (labeled energy on the meter) I can use out of the battery bank for both 12V and inverter use before I need to recharge.

I.e., if I can safely pull 900Wh out of the battery leaving it at 50% charged, then I reset the meter when I know the battery is fully charged and know I can wait until around 900Wh before I need to recharge again. I also monitor the voltage and current to assess the battery charge status as a secondary indicator, and the current to know how much I’m using at that given moment.

It takes a little effort to calibrate the readings with your battery setup to know how many Whs you’re battery will deliver before reaching your lowest desired charge level, and what the voltage actually means at a given current level. To help assess the batter charge condition, I always check the voltage under a 4aHr current to be consistent. The voltage will vary based on the load pulled off the battery, so reading the voltage under a specific load will give you more consistent results. I turn on the fantastic fan to high, inverter on (idle load), and the stove top range fan and halogen light (all other lights are LED). This gives me my ~4aHr load.

You can adjust the high and low voltage alarms (basically, the LED display blinks on and off as the alarm). Mine is set for 14.8v on the high end, and 11v on the low end. The high end is a reasonable setting and never seems to go off. The low setting is kind of pointless. Since the voltage will vary a lot under high to low loads, there is no reasonable setting that works for both. If you set it at say 12V, under high short loads it will go off constantly, but would be fine for low current loads. If you set it for the high current loads, a low current load will easily bring your battery to near exhaustion before going off. If you have a more constant load, you could find a reasonable setting to work well. But in an RV with such varying loads, it’s not to useful. Best to monitor the wHs used, and the voltage reading under a constant and repeatable load.

I’ve run the wiring from the battery to where the meter is installed, which is about 20’ of small gauge wiring, so it appears there is no issue with distance across the RV. Its a 4 wire setup.

I hope this helps.

Oh very interesting.  I didn't consider that I could hook it up straight to the battery for a reading of all of my power output.  Is this dependent on the shunt being placed on top of the negative lugs though?  I'm going out today to buy these:

 https://www.amazon.com/Shoreline-Ma...19&sr=1-1&keywords=battery+terminal+connector 

Or maybe I should just order those ones off of amazon.  I ask because my negative terminal has no room to screw the shunt onto it.  If I can use a terminal connector for the fat terminal then I can swap a negative over to that terminal and have room for the shunt to be hooked up.

So I'm using two 6v batteries in a series. If I'm going to measure the battery bank itself as the load am I correct in thinking that I would screw the shunt onto the negative of battery2 and then a cable runs over to the positive of battery1 ? I'm also curious as to what gauge cable you used for this.

This does help though, thank you very much!

 

[highdesertranger]

woah slow down you can get those terminal at an auto parts store for a couple of bucks each.  a much better terminal is a military terminal like these,



highdesertranger

 

[MikeRuth]

Ginga your missing out on how the shunt works and is connected. 

Any thing connected to your ground post will now be connected to one side of the shunt and then another short cable will connect the shunt to your battery ground terminal. 

Hopefully this picture will help....
http://popupbackpacker.com/wp-content/uploads/2013/10/Milan-2013-10-05-01409.jpg

notice how everything is connected to the right side, the left side has the short cable going back to the battery. So you won't have any issue with running out of room on the battery, you might have trouble getting everything attached to the shunt 

MIke R

 

[ginga]

Ginga your missing out on how the shunt works and is connected. 

Any thing connected to your ground post will now be connected to one side of the shunt and then another short cable will connect the shunt to your battery ground terminal. 

Hopefully this picture will help....
http://popupbackpacker.com/wp-content/uploads/2013/10/Milan-2013-10-05-01409.jpg

notice how everything is connected to the right side, the left side has the short cable going back to the battery. So you won't have any issue with running out of room on the battery, you might have trouble getting everything attached to the shunt 

MIke R

Oh so the shunt could go right on the negative battery terminal and then the negatives that were previously on that battery get connected to the second side of the shunt?  I think I understand now, thank you!

 

[John61CT]

Yes point is the current passes **through** the shunt, that's how it gets measured

 

[Weight]

Battery negative, battery cable to shunt, shunt cable to negative bus bar, all negative wires and cables from Stuff to negative bus bar. If using chassis grounds, negative bus bar to chassis. The shunt could not, should not, be mounted directly to the battery terminal. In fact, my shunt contains electronic things that do not like inside battery box.

 

[ginga]

The shunt could not, should not, be mounted directly to the battery terminal.

why not? 

https://www.amazon.com/review/R11UR...Thread=TxAWWNFBRBDG8F&store=hi#wasThisHelpful

 

[Weight]

My. My shunt has electronic board as part of the shunt. It would not like fumes from battery. Yours. Yours may be different and you can mount it where ever you can. If like the photo, do something to keep the shunt from flexing.

 

[ginga]

Grr! It didn't work you guys! I wired the ammeter up exactly as you see it here. https://s-media-cache-ak0.pinimg.com/564x/dc/e7/22/dce7228e806e656ba2ade63376ac5947.jpg The ammeter turned on and worked just fine, but anytime I turned a device on it didn't register anything. I saw 12.32 volts. No current, no watts, and no ah.

The shunt has removable bolts, so for the negative connection to the battery I slid it right on the terminal. Then for the other end of the shunt, I put the load negatives on the shunt terminal. I received power to the devices but the ammeter didn't measure anything. What gives? The only help on the instructions for that particular issue says that my wiring is wrong. Well I've quadruple checked and even mixed up the wiring a few times and it doesn't do anything.

My only thought is that maybe the positive is in the wrong position? My auxiliary batteries are two 6v in series. I wired the ammeters positive to the first battery (the meter showed me at 12.32v). The positive terminal has 3 connections to it. A solenoid, then one of these https://www.amazon.com/Blue-Sea-Sys...-3-catcorr&keywords=blue+sea+terminal+battery with both terminals used up. Does it matter which positive the ammeter draws it's power from? Does it perhaps need to be the absolute first connection? Maybe that is my mistake.

:s

 

[SternWake]

Battery is not the load

Power dc 6.5 to 100v is the battery

Or.possibly a defective unit. It happens

 

[gapper2]

Video is a little shaky but the best I could find.

 

[gapper2]

also will need a load on the battery to show current and power useage?