Interesting read on battery SOC measurement.

[avanti]

Originally Posted by GeorgeB

Our 2014 van is still under warranty for another 3 year so all the mods have to be done or approved by the upfitter.

This is totally untrue, at least in the US. The Magnuson Moss Warranty Act makes any such requirement illegal. You can NEVER have your warranty "voided" due to the use of aftermarket mods, unless the OEM can prove that your mod caused the fault. And, the burden of proof is on the OEM. You don't have to prove anything. If you read your warranty carefully, you will almost certainly find nothing to contradict this. And if it does, it is nonsense.

[gregmchugh]

The load on the alternator comes from the device on the end of the cable not from the cable itself. The cable needs to be sized large enough such that it does not overheat at the amperage of the load and cause a fire and such that the voltage drop through the cable is not significant. The circuit protection fuses or circuit breakers on the ends of the cable are sized to match the size of the cable and prevent an overload of the cable in the case if a short circuit, the overload would overheat the cable and result in an electrical fire. A larger cable will not increase the load.

[avanti]

Originally Posted by gregmchugh

The idea that the alternator could be damaged by using too large a cable does not make any sense. Larger cables cannot result in increased loads on the alternator.

Well, this isn't quite true. Although larger cables can't consume current, smaller cables can cause voltage drops which in turn would limit current. So, a too-small-cable could be a half-assed way to limit current.

There are situations in which a cable can be safe from overheating but still produce excessive voltage drop.

[markopolo]

Looks like the factory upfitter connection is spec'd at 50A (53A max). If that's the case then an alternative wire run would have to be used.

50A to 2 batteries isn't too bad. They wouldn't draw that for too long. George doesn't take them way down. I'd still focus on getting the volts up. Half a volt could be lost if using an isolator. I'd take a look at the ground path also. An inexpensive relay and better ground resulted in a 1 volt gain in my van with a heavy load like a microwave oven running.

[GeorgeB]

Originally Posted by avanti

This is totally untrue, at least in the US. The Magnuson Moss Warranty Act makes any such requirement illegal. You can NEVER have your warranty "voided" due to the use of aftermarket mods, unless the OEM can prove that your mod caused the fault. And, the burden of proof is on the OEM. You don't have to prove anything. If you read your warranty carefully, you will almost certainly find nothing to contradict this. And if it does, it is nonsense.

Your'e right it is not supposed to void it. I simply have a very good and productive relationship with Safari Condo. They are very open for mods to their builds, but they are interested in understanding and approving what's being done to the core systems so they can eventually implement it in future campers and be able to service the vehicle if I sell it. I convinced them to do the Trimetric install and they offered it to other customers. Trying to get them to start thinking about Lithium batteries!

The mods that were done on our van
http://www.classbforum.com/forums/f8...mods-4059.html

[booster]

The #6 wire is going to cost about .5 volts at 50 amps compared to a 2/0 cable. The big thing with the wire size is not that the cable resistance is so high it drops current, it is that the cable resistance drops the voltage enough to affect how much current the battery will take at any given state of charge. At 50 amps, his alternator may or may not be turning itself down much as it would be seeing probably 70-80 amps total load, or about 1/3 of rated output. It would be interesting to see what the alternator is running at when he sees the low voltage at the batteries.

George's agm batteries would probable accept well over 100 amps if down 50%. When I had 220ah of our 6 volt AGMs on the bench, they would pin the 100 amp s ourhore charger when only down 20%, at 14.3v.

As to the question if OEM alternators turn themselves down. The do, and do it very early compared to the aftermarket high output ones because they are not designed to put out large output for more than a short period of time and heat up quickly. Most will lose something like 30% of capacity hot, while the high output version might be 1/3 of that much. The reliability reduction in the OEM when used hard is basically just that the parts they use are not meant to be run that hard, reductions or not.

[GeorgeB]

Originally Posted by avanti

Well, this isn't quite true. Although larger cables can't consume current, smaller cables can cause voltage drops which in turn would limit current. So, a too-small-cable could be a half-assed way to limit current.
There are situations in which a cable can be safe from overheating but still produce excessive voltage drop.

I am puzzled by the 50A fuse that blew when I used the microwave with the engine running. The batteries where low and the engine hasn't been started for a while. I happened only once. The upfitter told me that the GM and Sprinters have a 70A fuse (and a bigger cable I suppose) for the link between the systems.

UPDATE: You answered my question booster when I was writing this!

Please educate me! It's my Class B class electric mods 101!
I always though that the higher the voltage the thinner the wire can be. That's why we need #4 gage cables to feed the very high amperage our 12v systems have.

So if you use a bigger cable do you give chance to the high amperage to get to the load but do you also run the risk of loosing voltage if it's too big?

Why would a thinner cable cause a voltage loss?

The discussion about increasing efficiency with higher voltage is very interesting _all the electric vehicles, including bicycles, use higher voltage than our usual and somehow inefficient 12v systems. Roadtrek tried the dual 24v/12v systems with some problems.

[GeorgeB]

Originally Posted by markopolo

Looks like the factory upfitter connection is spec'd at 50A (53A max). If that's the case then an alternative wire run would have to be used.

50A to 2 batteries isn't too bad. They wouldn't draw that for too long. George doesn't take them way down. I'd still focus on getting the volts up. Half a volt could be lost if using an isolator. I'd take a look at the ground path also. An inexpensive relay and better ground resulted in a 1 volt gain in my van with a heavy load like a microwave oven running.

I guess you also have to factor the load from the inverter. That's what killed my 50A fuse. 2 batteries charging + the extra 60 amp load for the microwave (700w). The inverter taps into the batteries and the alternator. Hard to tell why the load to the alternator peaked higher than 50A.

Still thinking the dual alternators is the ultimate solution. Do you like your setup avanti?

[avanti]

Originally Posted by GeorgeB

Still thinking the dual alternators is the ultimate solution. Do you like your setup avanti?

It is a dream. Best thing I have ever done for the van. It more-or-less takes power out of the boondocking equation. A little bit of local sightseeing every day is enough to get us through the night. Recommended.

[GeorgeB]

Originally Posted by avanti

It is a dream. Best thing I have ever done for the van. It more-or-less takes power out of the boondocking equation. A little bit of local sightseeing every day is enough to get us through the night. Recommended.

Great!
Does it affects your MPG?

[avanti]

Originally Posted by GeorgeB

Your'e right it is not supposed to void it. I simply have a very good and productive relationship with Safari Condo. They are very open for mods to their builds, but they are interested in understanding and approving what's being done to the core systems so they can eventually implement it in future campers and be able to service the vehicle if I sell it. I convinced them to do the Trimetric install and they offered it to other customers. Trying to get them to start thinking about Lithium batteries!

Sounds like a great, collaborative relationship. I was only reacting the words "...have to be done...".

[GeorgeB]

Originally Posted by avanti

Sounds like a great, collaborative relationship. I was only reacting the words "...have to be done...".

Yes, should have said ..I prefer that they do it...

They have a very "paternalist" but caring attitude toward their vehicles. As the owner told me once they don't want to have orphans! They do care about all the family members

No wonder most of their vehicles are still on the road. They've asked the owners to post their vehicles with the serial number I'm #1605. See the #31 https://www.facebook.com/12310412785...type=3&theater

[booster]

Originally Posted by GeorgeB

Please educate me! It's my Class B class electric mods 101!
I always though that the higher the voltage the thinner the wire can be. That's why we need #4 gage cables to feed the very high amperage our 12v systems have.

So if you use a bigger cable do you give chance to the high amperage to get to the load but do you also run the risk of loosing voltage if it's too big?

Why would a thinner cable cause a voltage loss?

The discussion about increasing efficiency with higher voltage is very interesting _all the electric vehicles, including bicycles, use higher voltage than our usual and somehow inefficient 12v systems. Roadtrek tried the dual 24v/12v systems with some problems.

Higher voltage will give lower amps if providing the same amount of watts of power, in direct proportion. Double the voltage, 1/2 the amps. That is what allows the smaller wire as it is the current, not the voltage, that is the primary issue with wire sizing. Bigger wires at the same amperage give less voltage drop, so whatever is on the load end gets a higher voltage than with the small wire.

In the cases we are talking about here, it gets a bit weirder because batteries react differently than other loads. With a load like the inverter running the microwave, you have a nearly constant watts, so increasing the voltage will reduce the current in the direct ratio as you described. With the batteries it all flips on its head as the batteries consume more or less watts of power depending on what voltage is put on them. This is true even when the batteries are at any state of charge for the most part. For this reason, if you increase the voltage to the batteries, the current to the will go up, not down like it would with a load like the microwave.

The battery deal has some downsides, but also some upsides. Hot wires, blown fuses, failed alternators can be downsides. Upside is that if the voltage is down a bit because of wire resistance or alternator reduction, that voltage reduction will get smaller and smaller as the battery fills up and the current drops. By the time the batteries are full, you will see essentially full alternator voltage (unless there are other loads) and almost no current, which is good for topping the batteries. What does happen, though, is that if you have the resistance lowering the voltage and current in the early charging , is that it makes the charging slower initially, so you need more time to get full.

[avanti]

It is worth noting that in the case of the Balmar regulator in my 2-alternator system, the regulator has a "sense" input that provides feedback to the regulator. The reg will constantly adjust the alternator such that the sensed voltage is kept to the current target voltage (which, in turn, is determined by the 3-stage charge algorithm and settings). So, if you run the sense wire directly to the + terminal of the battery, the system will automatically adjust for voltage drop on the main charge wire.

[avanti]

Originally Posted by GeorgeB

Great!
Does it affects your MPG?

Well, I guess it has to. But, not that I can notice. And, of course, when the battery is fully charged the alternator just freewheels, so it is in any case only a short-term issue during charge.

Interestingly, the regulator has a feature called "small engine mode". You can attach a manual switch that reduces the field voltage to 50%, thus limiting the load on the engine. It is intended for small boats that need bursts of extra thrust. It works by shorting the alternator temperature sensor input, thus making the regulator think the alternator is hot.

[GeorgeB]

Originally Posted by booster

Higher voltage will give lower amps if providing the same amount of watts of power, in direct proportion. Double the voltage, 1/2 the amps. That is what allows the smaller wire as it is the current, not the voltage, that is the primary issue with wire sizing. Bigger wires at the same amperage give less voltage drop, so whatever is on the load end gets a higher voltage than with the small wire.

In the cases we are talking about here, it gets a bit weirder because batteries react differently than other loads. With a load like the inverter running the microwave, you have a nearly constant watts, so increasing the voltage will reduce the current in the direct ratio as you described. With the batteries it all flips on its head as the batteries consume more or less watts of power depending on what voltage is put on them. This is true even when the batteries are at any state of charge for the most part. For this reason, if you increase the voltage to the batteries, the current to the will go up, not down like it would with a load like the microwave.

The battery deal has some downsides, but also some upsides. Hot wires, blown fuses, failed alternators can be downsides. Upside is that if the voltage is down a bit because of wire resistance or alternator reduction, that voltage reduction will get smaller and smaller as the battery fills up and the current drops. By the time the batteries are full, you will see essentially full alternator voltage (unless there are other loads) and almost no current, which is good for topping the batteries. What does happen, though, is that if you have the resistance lowering the voltage and current in the early charging , is that it makes the charging slower initially, so you need more time to get full.

Understood. Thanks for the very informative answer!

What I don't really understand is how the different sources of charging interact with each other. For example the solar controller does send current to the batteries even if the alternator is running at a much higher amperage. I've tried to see what happens when I'm plugged into shore power, the motor is running and there's a bright sunlight. No difference in voltage if I unplug the shore connection. Normally the Inverter/charger priories the shore power, there's a disconnect relay. Could the alternator be charging the batteries at the same level than the shore. Normally not.

[GeorgeB]

Originally Posted by avanti

It is worth noting that in the case of the Balmar regulator in my 2-alternator system, the regulator has a "sense" input that provides feedback to the regulator. The reg will constantly adjust the alternator such that the sensed voltage is kept to the current target voltage (which, in turn, is determined by the 3-stage charge algorithm and settings). So, if you run the sense wire directly to the + terminal of the battery, the system will automatically adjust for voltage drop on the main charge wire.

Did you left the wiring between the van battery and the house system in case the second alternator busts? So you can activate it manually? Or the reverse, in case you need a boost to your van battery, with a bypass?

[avanti]

Originally Posted by GeorgeB

Did you left the wiring between the van battery and the house system in case the second alternator busts? So you can activate it manually? Or the reverse, in case you need a boost to your van battery, with a bypass?

Yes, the original wiring is still there, as is the old isolation relay. I did this precisely so my "boost" button would still work. I did disconnect the wire from the "engine running" signal to the isolation relay, so currently it is ONLY controlled by the boost switch. So, in case of a failure, I would have to reconnect that wire. Easy enough.

[booster]

Originally Posted by GeorgeB

Understood. Thanks for the very informative answer!

What I don't really understand is how the different sources of charging interact with each other. For example the solar controller does send current to the batteries even if the alternator is running at a much higher amperage. I've tried to see what happens when I'm plugged into shore power, the motor is running and there's a bright sunlight. No difference in voltage if I unplug the shore connection. Normally the Inverter/charger priories the shore power, there's a disconnect relay. Could the alternator be charging the batteries at the same level than the shore. Normally not.

The interaction of the charging systems is something we have struggled with and discussed here many times.

In general, if the charging sources don't base their charging on amps, there are not major interactions. Voltage is pressure, so the highest voltage generating source does as much work as it can. Just like water in pipes, the high pressure on will flow and the lower ones won't. If the highest voltage source is on and keeping up, you won't see a change in voltage ass you turn on the other sources.

This all changes if any or all of the sources use amps in their charging control, and it can get really weird sometimes.

If they use amps internally in the charge source, they don't know where they are going. They can be going to the batteries, which is what their algorithm thinks, or they can be going to a load which totally messes up the control. Xantrex and Blue Sea both make chargers that measure amps internally, and it is hard to deal with in an RV. Some of the smart regulators on alternators also use amps internally, so they would have the same issues. I think the Balmar does, but Avanti probably knows for sure. It doesn't have to be a smart regulator add on to be an issue, either, as the DC Power alternator we have has a Denso internal regulator that does the same thing, but to a lesser output change and not programmable.

Other system use amp to control charging but measure the amps right at the battery in and out, just like your Trimetric does. They only see what the battery is doing, so loads or other charging sources don't mess them up at all, and they don't interact with each other. They run off a shunt or inductive pickup, so it is easy to tell. Blue Sky solar controllers work that way, as do others. For chargers, the only one I know of is Magnum with the right options. I don't know of any alternators or smart regulators that work off shunts, so you get stuck with a manual system for them, if you want to eliminate any interactions with the other systems, which is not bad because all you do is watch an ammeter a bit as you drive, and turn it off when it has finished charging.

[GeorgeB]

Originally Posted by avanti

Yes, the original wiring is still there, as is the old isolation relay. I did this precisely so my "boost" button would still work. I did disconnect the wire from the "engine running" signal to the isolation relay, so currently it is ONLY controlled by the boost switch. So, in case of a failure, I would have to reconnect that wire. Easy enough.

That makes a very fail-proof and resilient system! If only the ProMaster second alternator option ( Dodge Promaster Dual Alternator Kit with 280XP High Amp Alternator for 3.6L Gas Engines ) was a proven reliable option I would start convincing my upfitter to try it out even if it's a very expensive mod. I have the feeling the Sprinter install is more sturdy. Am I right?

I haven't read all the dual alternator thread yet. Did anyone installed successfully the Nations on the ProMaster ?