Amp gauges for 260A alternator.

[GeneralDisorder]

I'm considering a pair of these. They come with shunts and are 12/24v and they are relatively inexpensive. One for each side of the 260A alternator. My main need beyond monitoring the draw on the stupidly expensive alternator is to ascertain how much overhead I have to work with on the 24v side to choose appropriate size and quantity of Victron Orion-Tr DC/DC Converters for charging my habitat solar bank.

Digital Ammeter Gauge - CEAR | Electrical Monitoring | KUS Americas, Inc.

The Digital Ammeter gauge CEAR provides an overview to the user and tells the user whether the system is charging or draining the battery charge.

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My only concern is that the specs given by Niehoff do say the alt can produce "28 V 260 A/14 V 140 A" which the 14v side is well within the capability of the gauge.... but if the 24v side can actually push 260A...... of course the LBCD would shut the truck batteries down if it senses more than 200A going through it..... the gauge could easily max out though I'm not sure that would be all that big of a deal since I probably want to keep the output below 150a even with the DC/DC converters in play. The ones I'm looking at can supply 17a each to the habitat batteries and I'm thinking of 2 or 3 of these in parallel.....

Anyone know what the 24v side on these trucks is nominally pushing for amperage on a C7 truck with fully charged truck batteries? My 1079 does have a bunch of 24v lighting around the outside (it's not 12v like the truck lighting) of the habitat but it's all LED. I know the older trucks even some with C7's had the 100a alt so I can't imagine I don't have the overhead needed to run a couple converters at 34a to charge the solar bank while driving.

Or if anyone has suggestions for better gauges......

 

[Ronmar]

The ECU and TCU load are probably not all that great. Then there is wiper, heater-A/C and I supposer air dryer heater when its cold out. And of course + any 24v lighting you have added. You would have to measure to be sure, but all up probably not more than 30A @24v.

Where did you come up with that 200A LBCD cutoff? I have seen a low battery side/system voltage of 20.5v listed as a cutoff/shift to trickle charge point for the N2003, and it will hold that disconnect until it sees the batts float up over 24.5V under trickle charge, or is reset. I havn't seen an amp spec for cutoff. The charge current from alt to battery dosn’t pass thru the LBCD anyway.

I think I would look for a shunt/meter pair that can go to 260, because unless the 12v lights are on, I think the alt will produce it as long as it can maintain regulated voltage…

 

[Skyhawk13205]

I am not sure about max draw, I have a 3126 with a 100 amp alt. The only time it is maxed is when the grid heater is on. It drags down the alt to max output. Voltages go down to 22 when the grid heater cycles. Grid heater has a 100 amp fuse so it should not be more than that.

my friend was a 1083A1 C7 with a 100 amp alt. It seems to run without issue. I think the transmission cooling fan is electric but I am not 100% sure.

having a current monitoring system is a good idea. I was thinking about using a transformer type to measure draw. Let us know how it goes.

 

[GeneralDisorder]

Ah yes it is voltage based on the LBCD cut off..... the LBCD itself is *rated* to handle 200a but as you pointed out the charge current doesn't pass through it so that's probably not much of a limitation in practice.

The grid heater doesn't seem to bother the 260a alt much. The voltage drop is minimal with it and the 4 battery setup. I probably will wire the remote switch for the Orion chargers through whatever relay controls the grid heater in addition to a manual switch so no charging takes place while it's on and I can turn off the Orion's manually. I'm hoping to be able to run three or four of them in parallel for 51 or 68 amps of charging from the alternator.

 

[Ronmar]

Oh yea, I forgot all about the grid heater, that is typically a fairly short duration load though. @Skyhawk13205 if you are experiencing a significant voltage drop when the grid heater is engaged, I would suspect weak/dirty connections. The giveaway for this is if you measure the voltage at the source, it will not have as much voltage drop as the panel gauge. In a properly wired world, the voltage drop should be less than 3% from source to destination at max load… and of course you are loosing up to 3/4 of a volt thru the polarity/LBCD diodes. Nice airplane

@GeneralDisorder I don’t think you will have any problem getting 70A for house batt charging…

 

[GeneralDisorder]

I checked the amperage output from the alternator this afternoon. Fully charged batteries. With everything on the draw was about 12 amps on the 14v side and somewhere between 6 and 12 amps on the 28v side. That's with all the 1079 24v lighting turned on, service drive and panel bright engaged on the lighting switch.

The 260a alternator does not work hard on my truck clearly. I'm still hunting for 300 amp capable gauges and shunts but I'm going to figure probably six of the 17 amp Orion chargers. That will be 102 amps but it sure seems like that's no problem for this beast and it will charge the house batteries in a hurry which means lower fuel consumption and shorter idling times.

Anyone see an issue with that plan? I will have them shut off during warmup with the grid heater and have a manual override as well in case of high battery draw from the truck batteries.

 

[Ronmar]

Yea you will pull a little more than that @24 with the heater blower, A/C and wipers on, but not all that much more. That is quite a bit less than my guesstimate…

You have LED lights? That 14V load seems low for all the lights on. I totaled them up one time With incandescents the total bulb wattage needed like 26A@13V for a 1078 when you were stepping on the brakes, and just shy of 34A @13V on the 1079 with all the added box marker lights. Almost 10A of that was the headlights on high beam…

What you are proposing sounds perfectly feasible.

I am looking at something similar myself. Simply shifting all the vehicle load over to 28V gained me nearly a KW of potential output out of the 100A alt. With LED’s I estimate I can get nearly 60A@ 28V, so probably 3 of the 24-24 chargers. The Orions are cool in that you can control them remotely and they are designed to parallel, so tailoring load to availability should be easy. I am also looking at a 28V generator, so will have yet another option(solar, service alternator or generator) to feed my charge controller…

 

[Skyhawk13205]

Oh yea, I forgot all about the grid heater, that is typically a fairly short duration load though. @Skyhawk13205 if you are experiencing a significant voltage drop when the grid heater is engaged, I would suspect weak/dirty connections. The giveaway for this is if you measure the voltage at the source, it will not have as much voltage drop as the panel gauge. In a properly wired world, the voltage drop should be less than 3% from source to destination at max load… and of course you are loosing up to 3/4 of a volt thru the polarity/LBCD diodes. Nice airplane

@GeneralDisorder I don’t think you will have any problem getting 70A for house batt charging…

I wish it was mine. It was the one I learned on so it is forever stuck in my mind.

I have been having issues with my electrical system I cleaned all my major connections alt connections, block ground, pdp points, diode block connections, checked for shorts and rotated my batteries. I am having voltage fluctuation of about .5v on both 28v and 14v. The fluctuation is more pronounced at a high load on the 14v buss. The voltage at alt and batteries agree. The Diode block has a VOM test drop of .46 for 28v run and .7 for 14v run. The pdp reads a voltage drop of .5-.7ish. I have been troubleshooting for about 2-3 months. I am basically at the point of parts change. I suspect my alternator is weak and not able to output sufficient load but not outright failing. The grid heater voltage drop is consistent at all these points, it is basically as if the alt drops offline when the grid heater cycles.

 

[87cr250r]

You seem hyper focused on the alternator but what is the condition of your batteries? I've never had an alternator alternate functionally. They always just stop working. The box full of acid should always be your first suspicion, much more to go wrong there. If you're batteries are more than 5 years old you should be very suspicious of their condition. If they're more than 7 years old you should replace them regardless of their condition.

 

[Ronmar]

Yea they do stick with you.

Have you load tested the batteries? I would pick the best two and drop to just 2, at least for testing. Batteries in parallel can make troubleshooting difficult as a good battery can mask a bad one. If you had a bad cell in a battery it would have trouble maintaining voltage under load and could also suck up a lot of the alternator output.

probably should start a new discussion or PM me so we don't hijack this one.

 

[GeneralDisorder]

Yea you will pull a little more than that @24 with the heater blower, A/C and wipers on, but not all that much more. That is quite a bit less than my guesstimate…

You have LED lights? That 14V load seems low for all the lights on. I totaled them up one time With incandescents the total bulb wattage needed like 26A@13V for a 1078 when you were stepping on the brakes, and just shy of 34A @13V on the 1079 with all the added box marker lights. Almost 10A of that was the headlights on high beam…

Yes the entire truck including the headlights are LED. Other than the headlights which I upgraded to the heated TruckLite LED's, the truck was built with 100% LED's from the factory with the exception of the lights on the inside of the van. Those were 24v incandescent aviation bulbs - I swapped them to LED also and put 24v LED bulbs inside the T12 housings and wired those to the truck as well.

The 14v readings I was getting were bouncing a bit on my meter - readings between about 6 and 15 amps.