New alternator. DC to DC breaker issue.

[posplayr]

Looking at the voltages this is definately a problem with the new alternator. The feed lead for the DC to DC charger did need to be moved for sure, but the voltage regulator should NOT vary voltage output that much, and the alternator MFG (Powermaster) agrees. They are shipping a replacement out on Monday.

The variation may have nothing to do with the alternator. This is speculation but if you install the new alternator and nothing changes you can explain it this way:

If you have a high resistance path between the Alternator and the DC to DC (strong evidence if you keep tripping breakers at input to Dc-DC)

For example any combination of the following:

1. You connected to the start battery and have old and compromised battery connections to the alternator:
   
2. You have dirty/corroded connections in your original wiring to the aux battery.
   
3. The wiring is undersized over a large percentage of the total path length.

​

An oscillation can setup depending upon how fast the DC-DC convertor settles as well as how fast the alternator responds to changes in load.

When the DC-DC requires more current from the alternator (to maintain for example 14V @ 40 amps at the output), DC-DC the input current demand will rise proportionately higher for a larger path resistance to the alternator. A lower resistance will not require as much additional current demand.

As the demand increases it is more likely for the alternator to exceed its RPM-dependent charging capacity, which reduces the voltage output and further increasing the required demand.

As some point even with a disconnected ACC wire, the voltage will drop below 12.5 volts (disconnect voltage without ACC) and the DC-DC will stop charging and the current demand will drop and the alternator voltages will again rise to levels consistent for idle RPM without the DC-DC. At some point, the voltages are high enough (13.0 V without ACC) and the DC-DC turns back on again continuing the oscillation and voltage variation.

If these currents are high enough (and despite the on-off-on duty cycle) you will eventually trigger the thermal limit for fuse/breaker and it will reset (at the input to the DC-DC).

Based on what is happening, you might be safer to just connect your start battery directly to the lithium battery so you can at least see what your voltage drops/current draw is to gauge how much resistance you have.

You are more likely to under-charge the lithium with a direct connection and you can see where you are at with your connections without fear of tripping a fuse/breaker.

Note the difference between 12.5 and 13.0 for turn-off and turn-on is used to guard against the type of described oscillation, but if the resistance is too high , then the 0.5V spread is insufficient to keep from oscillating

 

[dbhost]

Update. Amazon has delivered the Cooper Busman 60 amp breaker.

This thing has easily twice the mass of the Chineseiium breaker.

More importantly continued testing shows the China breaker blows at 38.47 amps reliably, WAY under its rated amperage.

With the new breaker installed, 20 minute test so far and zero failure.

 

[posplayr]

Update. Amazon has delivered the Cooper Busman 60 amp breaker.

This thing has easily twice the mass of the Chineseiium breaker.

More importantly continued testing shows the China breaker blows at 38.47 amps reliably, WAY under its rated amperage.

With the new breaker installed, 20 minute test so far and zero failure.

If you go to the amazon link for yhe red wolf 60a breaker there is a 1 star review fir someone that installed a 60a breaker for a 40a dc-dc charger thst reset immediately; sound familiar?

Best to read the worst reviews as well as the best

That said, I have done quite a bit of testing on the breakers I use to get an idea if the breaker trip currents/ duration times. Never recall seeing anything this bad.

 

[1der]

More importantly continued testing shows the China breaker blows at 38.47 amps reliably, WAY under its rated amperage.

With the new breaker installed, 20 minute test so far and zero failure.

The fact the breaker was getting hot was due to some out of spec resistance. Could be the connectors on the ends of the wires, the connection to the breaker terminals or internal to the breaker. I have had the same occur in the cheaper fuse blocks. 100 amp rating for the fuse block was way overstated to reality. 50 amps of current was melting the posts.

So, the breaker's internals in this case was the issue.

The alternator voltage range seemed okay to me.

 

[posplayr]

The fact the breaker was getting hot was due to some out of spec resistance. Could be the connectors on the ends of the wires, the connection to the breaker terminals or internal to the breaker. I have had the same occur in the cheaper fuse blocks. 100 amp rating for the fuse block was way overstated to reality. 50 amps of current was melting the posts.

So, the breaker's internals in this case was the issue.

The alternator voltage range seemed okay to me.

most all fuse/breakers are thermal devices, some alternate heat sources will degrade the specified current trigger point.

 

[dbhost]

The fact the breaker was getting hot was due to some out of spec resistance. Could be the connectors on the ends of the wires, the connection to the breaker terminals or internal to the breaker. I have had the same occur in the cheaper fuse blocks. 100 amp rating for the fuse block was way overstated to reality. 50 amps of current was melting the posts.

So, the breaker's internals in this case was the issue.

The alternator voltage range seemed okay to me.

That's the way it was looking. Since the Cooper Busman swap it is working as expected. HOWEVER...

This at least got me to get off my tailbone and tap off of the chassis battery instead of the alternator to shunt over to the DC to DC charger... So I am finally wired in spec for my devices.

I do still want to make my connection to the acc signal lead so I am at 100%...

 

[posplayr]

This at least got me to get off my tailbone and tap off of the chassis battery instead of the alternator to shunt over to the DC to DC charger... So I am finally wired in spec for my devices.

I'm sure you don't want to hear it but for anybody else reading the thread, you are worse off as far as a DC-DC charger is concerned connecting to the start (chassis) battery vs connecting directly to the alternator B+ and mounting bolt ground.

This is plain to see once you understand that any charging currents into the DC-DC charger are coming from the alternator. This is because as a general rule, if the engine is running the alternator output will be higher than the chassis battery voltage.

The net effect of connecting to the start battery is you now have to pass current from the alternator to the chassis battery and then follow you DC-DC battery connection which adds additional voltage drops.

For my 2002 E-250, I typically see close to 0.5V drop off my cigarette lighter voltage meter. This is an always Hot connection but it is not drawing any more current than the meter, so that drop is related to about 15 amps being provided by the alternator to the charging system.

If you connect the DC to DC to the chassis battery you would be quadrupling that current 15 amps (minimum alternator draw at idle) + 45 amps (DC-DC draw at input = 60 amps total through the alternator connections. With additional chassis loads like AC, heater, lights it just gets worse.

It has been discussed and it is pretty much common knowledge that a 40 amp DC-DC left to run at idle will cause an alternator to burnup because of lack of cooling at idle. These additional voltage drops just make the current drawn from the alternator proportionally higher. Your DC to DC has no way to shut off the charging, so you are kind of "up a stream without a paddle" if you plan on any extended idling periods. As a general rule, you probably don't want your alternator to be more than 220 degF else it will shorten its life.

Unless the alternator was already rewired for a DC-DC and you have similar wiring as my E250, you could be dropping more than a 1-2 volt. These drops are easy to measure (alternator B+ -> chassis battery + and Alternator mounting bolt to Chassis battery -).

 

[dbhost]

I'm sure you don't want to hear it but for anybody else reading the thread, you are worse off as far as a DC-DC charger is concerned connecting to the start (chassis) battery vs connecting directly to the alternator B+ and mounting bolt ground.

This is plain to see once you understand that any charging currents into the DC-DC charger are coming from the alternator. This is because as a general rule, if the engine is running the alternator output will be higher than the chassis battery voltage.

The net effect of connecting to the start battery is you now have to pass current from the alternator to the chassis battery and then follow you DC-DC battery connection which adds additional voltage drops.

For my 2002 E-250, I typically see close to 0.5V drop off my cigarette lighter voltage meter. This is an always Hot connection but it is not drawing any more current than the meter, so that drop is related to about 15 amps being provided by the alternator to the charging system.

If you connect the DC to DC to the chassis battery you would be quadrupling that current 15 amps (minimum alternator draw at idle) + 45 amps (DC-DC draw at input = 60 amps total through the alternator connections. With additional chassis loads like AC, heater, lights it just gets worse.

It has been discussed and it is pretty much common knowledge that a 40 amp DC-DC left to run at idle will cause an alternator to burnup because of lack of cooling at idle. These additional voltage drops just make the current drawn from the alternator proportionally higher. Your DC to DC has no way to shut off the charging, so you are kind of "up a stream without a paddle" if you plan on any extended idling periods. As a general rule, you probably don't want your alternator to be more than 220 degF else it will shorten its life.

Unless the alternator was already rewired for a DC-DC and you have similar wiring as my E250, you could be dropping more than a 1-2 volt. These drops are easy to measure (alternator B+ -> chassis battery + and Alternator mounting bolt to Chassis battery -).

You are quite possibly correct in this, however, I believe the chargers MFG intent for direct battery connection is to support reverse charging. I.E. using the coach battery to charge a chassis battery to get you out of a jam.

The signal wire is being reconnected at some point tomorrow or Monday.

Looking on Amazon I can see about 5 different "brands" of what appears to be the same DC to DC charger / MPPT charge controller. And there are versions within versions as it were. The earlier models did not include a LiFePO4 charging profile. The new ones do...

Long idling periods are rarely if ever a great idea for a ton of reasons, so I will personally be trying to avoid them as much as possible...

 

[Scalf77]

The signal wire is being reconnected at some point tomorrow or Monday.

Don't, for your alternator you do not want to connect to the ACC terminal.

 

[posplayr]

You are quite possibly correct in this, however, I believe the chargers MFG intent for direct battery connection is to support reverse charging. I.E. using the coach battery to charge a chassis battery to get you out of a jam.

I did not try to decode the Chinese manual;
Is the chassis battery (reverse) charging using a Boost charger?

Assuming it is just a relay type connection and you have a Lithium Aux battery which is around 3.2V per cell or 12.8V at the battery terminals, you are not going to be pushing much current in reverse unless the start battery is really dead in which case it might not take anything. Typical charge rates are about C/10 at voltages just over 13V and that is probably 5-8 amps depending on your start battery amp hour capacity.

Pushing in reverse when the DC-DC is connected at the alternator adds the wire connections between the alternator and the battery but at a much lower current. So you are limiting the reverse chassis battery charging capacity, with the alternator connected DC-DC but at 5-8 amps that will have minimal impact to your situation.

A lithium charge pack would be a better alternative. I found a cheap one that spins over my V10 6.8L quickly.

This one is not available anymore but I picked it up for $60 shipped with tax.
https://www.amazon.com/gp/product/B09TZXGCB7/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

If you can shut down the DC-DC, you can also add a cheap 120VAC to 12V DC charger run off an investor to charge the house battery to the start battery at 14V. Even then, the alternator connections are not going to cause any problems.


At one point i was going to design a controller for the Renogy DC-DC which has a 0A, 20A and 40A settings. It required measuring the alternator temperature of at least using a tehrmal limnit switch. It going more complicated with just the limit switch.

In the end, I found a 300A alternator that had internal current limiting for thermal control making the DC-DC control function unnecessary. With my latest project trying to supply current to a 300 Amp-hr AGMs and a 50+ amps to a 12V AC (peaking between 80-100 amps supplied at idle + 15 amps to the chassis electrical) I dropped the DC-DC altogether.

The Renogy 40 amp DC to DC worked for a while but then reported an error after having run for a couple of days. I put in the smart Victron relays and it is now looking much more reliable and my 12V AC doesn't shut down from low voltage.

 

[dbhost]

FINAL UPDATE: So the alternator and alternator lead flat out failed due to insufficient lead diameter. I ordered the 140 amp alternator and 150 amp alternator hook up kit from Summit. The connection of the cable came off and it is all a melty mess...

Upon further review, Summits 150 amp alternator wiring kits are 6awg. Hardly sufficient for 150 amps. Maybe 100!

Given that issue, Summit is sending me a new not melty alternator, and a 2awg wiring kit Which allegedly is rated for a 200 amp alternator. Looking at ampacity charts they are all over the place, either 2awg is overkill or not nearly enough...

 

[posplayr]

As per my previous discussion, if you have high resistance between the slternstor snd the dc-dc charger you will have correspondingly higher dc-dc input currents that will stress you alternator even more.

Eliminating the effects of poor chassis battery connections and going straight from the alternator will effectively isolate the aux dc-dc charging from the exiting chassis charging wiring. This will minimize the dc-dc demand current.

You can try and fo a direct connect using only the alternator +B, and relaying on frame grounds. But yhen you are back to the original chassis wiring.

In my analysis it is better to just account for the two way loss of the 4-6 awg wiring as s funtion of the distances between alternator and dc-dc

 

[dbhost]

I am going back to wiring the charger direct to the alternator instead of going through the battery... Thus eliminating that load from the cattery wiring.

 

[posplayr]

I am going back to wiring the charger direct to the alternator instead of going through the battery... Thus eliminating that load from the cattery wiring.

Sorry for not following through sooner, but with the implied currents you were experiencing to melt the insulation off of 6 AWG wire, I would measure the voltage crops and current levels you have going into the input side of the DC-DC.

In theory, the DC-to-DC charger will limit the output current to the rated 40 amps, but voltage drops will increase the DC-to-DC input amperage above the output. In the extreme, I would expect you to see an overheated alternator before you burn the insulation off any wires. Something doesn't add up and bears some investigation.

If the DC-DC input leads don't burn/melt with a direct connection to the alternator, that can be partially explained but still suggests there is something wrong with the DC to DC exceeding 40 amps at the output.

 

[dbhost]

Something to note. The DC to DC converter had worked perfectly prior to the original alternator swap. I have crawled through the entire underside of the van looking for any indication of damage to the feed line coming from the engine compartment to the electrical compartment, and found no visible damage. No signs of corrosion whatsoever, no heated or otherwise damaged insulation.

We have resolved the issue found with the breaker throwing yes. And the 60 amp breaker was CLEARLY throwing before it got anywhere near 40 amps.

And yes, I will certainly once the new alternator is in and it is running again test voltage coming from the alternator, at the breaker, and at the feed into the DC to DC charger. Kind of hard to do wthough as the old alternator hard failed.

I am no expert in wire sizes I just look at the recommendations, and what the engineering ampacity charts tell me and those thigns are ALL OVER THE PLACE. BUT... all of them say for alternators up to 120 amps 6awg is acceptable. For alternators OVER 120 amps like my 140 us a minium of 4awg, I am going with 2awg to bump up that safety margin a bit... AND I am shunting off the 40 amp load from the DC to DC charger onto a different 6awg cable which should more than handle the load.

So yes, there is more to be done here. I THINK I am on the right path, poor or should I say misidrected choice on alternator feed line, and a clearly defectdive breaker certainly did not help the situation.

Get it all reassembled, and tested, only thing left to test is the hunk of wire / voltage drop between engine bay and the dinette bench / electrical compartment... And if that is faulty, that will be replaced soonest possible. If it is the charger itself that is faulty, I have a spare unit ready to go in, and it doesn't have any issues on MPPT function so not convinced it is an issue. We will see, and monitor...

 

[posplayr]

I am no expert in wire sizes I just look at the recommendations, and what the engineering ampacity charts tell me and those thigns are ALL OVER THE PLACE. BUT... all of them say for alternators up to 120 amps 6awg is acceptable. For alternators OVER 120 amps like my 140 us a minium of 4awg, I am going with 2awg to bump up that safety margin a bit... AND I am shunting off the 40 amp load from the DC to DC charger onto a different 6awg cable which should more than handle the load.

.

There seems to be confusion about how to select wire gauge sizes for a DC-DC Charger.

This is the specification for the AP40DC's conductor size. The specification for "Twin Core" implies both a positive and negative lead running from the chassis power source to the DC-DC charger input and DC-DC output to the auxiliary battery.

Please note that the Twin Core cable size requirement is related to the cable length.

Cable Length / Twin Core
0 – 1 Metres 8AWG
1 – 5 Metres 6 AWG
5 Metres + 4 AWG
​

In contrast, ampacity is a normalized per-unit length metric related to maximum temperature/heat dissipation performance and installation conditions.

The ampacity of a conductor depends on its ability to dissipate heat without damage to the conductor or its insulation. This is a function of the insulation temperature rating, the electrical resistance of the conductor material, the ambient temperature, and the ability of the insulated conductor to dissipate heat to the surroundings.​

https://en.wikipedia.org/wiki/Ampac... the,without exceeding its temperature rating.


What is most appropriate for cable sizing for a Dc-DC is not ampacity but rather voltage drop. As stated multiple times, whatever voltage drop exists from DC to DC input from the alternator will have to be made up by the Boost convertor DC-DC charger to meet battery charging voltage requirements. This increases alternator amperage demand on the alternator.

1. Branch Circuits – This FPN recommends that branch circuit conductors be sized to prevent a maximum voltage drop of 3%. The maximum total voltage drop for a combination of both branch circuit and feeder should not exceed 5%. [210-19(a) FPN No. 4], Figure 2.

https://www.mikeholt.com/technnical-voltage-drop-calculations-part-one.php

In my own spreadsheet analysis, I adjusted my design to maintain no more than a 3% voltage drop as an objective. Some excursions to 4-5% are possible under extreme corner conditions.

To be clear maintaining a 3% maximum voltage drop will contain the boosted current increase to the same 3% range.

I cant find my spreadsheet now, and I was doing these calculations close to 3 years ago but as I recall using a 3% voltage drop rule I was getting close to 55-60 amps draw from the alternator to deliver 40 amps at the output of the DC-DC.

For example, if you need 14 VDC for your particular batteries, and you are only delivering 11 VDC to the input (because of underrated cables over too long of length)of the DC to DC, then you need an additional amount of input current. The total would be 40*14/11=50 amps.

The setup I have been working with to power a 12V roof top air conditioner power from 300 amp-hours of AGM is a direct connection from the alternator to the AGM bank through a Victron smart battery relay.

When the AGM battery is less than fully charged, the 300 amp alternator is able to push 100+ amps through a 6AWG pair of welding cables over a 15-foot distance at idle while also supporting 15 amps of chassis loads.

This is a lead acid wet start battery to lead acid AGM 300 Amp-Hr battery connection without any boost charger. The alternator charges at 14.5V and with currents of the high end (50-70 amp) of the 100Amp meter range there are only about 0.3-0.4V drop to the auxiliary AGMs corresponding to about 2%-3% voltage drop.

This demand current is probably 30%-40% higher than a 40amp DC-DC charger should demand which is why the smart relay is preferred in this situation over a DC-DC charger

The bottom line is that with 15 feet of "twin cable" distance (one way length) you should be fine with 6 awg wire. The DC-DC charger should be close to the auxiliary battery as that will minimize voltage drops that are not measurable by the DC - DC charger. These drops will lower the output charging when not in bulk mode, a somewhat minor consideration but it is nevertheless good practice to keep the DC toDC as close as practical to the auxiliary battery.

 

[dbhost]

So from Sportsmobiles original wiring, which was supposed to be 45 amp, there is a single conductor running from the alternator, to the battery isolator / charger under the hood, from the battery isolator / charger to the original or at least what was there when I bought it 50 amp breaker mounted next to the isolator / charger. We used the original wiring but took the isolator out of the circuit and made sure the alternator fed the chassis battery, the other line went through breaker and was sized to 60 amp per Atems recommendation. So both fed off the lug off the alternator, chassis battery took what it needed, DC to DC charger took what it needed via the Sportsmobile wiring which I honestly am unsure if it is 6awg or 4awg. It makes a run of approximately 4m, certainly no more than 5m MAX.

And I can not reiterate this strongly enough. All was well and good before we swapped the alternator for the new high output alternator, and the reason for the replacement was mechanical due to noisy bearings.

Again, need to get the swap done, waiting for the proper fan clutch wrench set to arrive to finish the alternator swap job since pretty much everything has to come off to get the alternator out... Once done I will measure voltage at the battery and at the DC to DC converter and verify.

 

[posplayr]

And I can not reiterate this strongly enough. All was well and good before we swapped the alternator for the new high output alternator, and the reason for the replacement was mechanical due to noisy bearings.
.

Not sure if any conclusion can be drawn from that other than the fact that the original alternator could not push enough current to burn up your wires and the new alternator had enough rated current to do so.

"all is good" or "all is as should be" are often used statements that convey little other than doubt.

I attached a chart and set of specs for the 1997 Econoline model year.

The amperage rating is the maximum possible at or above redline of the engine.

As you can see from the table the bench mark amperage is at 2000 RPM which h is probably going 60 mph in overdrive.


At idle (750 rpm) the current output is going to be even less.

The shape of the curve is fundamental to electrical machinery. It is a magnetic saturation curve. Magnetic flux in the alternator is generated by the spinning armature cutting lines of flux in the stator. The magnification of this flux is related to the flux path and how magnetized the material becomes. Teh curve saturates (gets flatter the higher the RPM) because in layman/engineer terms all the randomly oriented electrons have rotated (max 90 degrees ) to align with the magnetic field and that is all the flux they can produce.

https://en.wikipedia.org/wiki/Saturation_(magnetic)


At 750 RPM idle the 215 amp alternator shows approximately 80 amps
At 2000 RPM the 215 amp alternator puts out about 170 amps.

So we can then estimate what the 95 and 130-amp alternators would be.

At 750 RPM idle the 95amp alt is 76*(170/215)= 60 amps
At 750 RPM idle the 130amp alt is 87*(170/215)= 69 amps

Remember the Chassis requires some of this current and I have measured about 15 amps on my 2002 5.4L with the lights and HVAc off.

This would leave:

95 amp Alternator 60-16= 45 amps available to the DC to DC Charger
130 amp Alternator 69-15 = 54 amps available to the DC to DC Charger

In this case, the 130 amp might be able to do some damage with poor connections. The 95 amp less so.

I don't have a 1992 Econoline to look at but I recently changed the battery cables on my 1990 Ford F150 with 4.9L I6. I was not adding any electrical loads but (when changing the O2 sensor) I discovered that the ground cable had been smoked. I changed it with a Motorcraft factory unit as well as an after-market positive lead to the solenoid.

It is not obvious how this might have been shorted out so i guess it is a possibility of normal loads getting it hot(engine cranking)?

There are factory upgrades to the battery connections for higher amperage alternators. i bought one for my 2011 E-350. With a DC-DC charger I would not rely on this but rather go direct to the alternator with both + and - cables.

If you did not run a separate ground cable from an alternator mounting bolt to the DC-DC charger as specified, you are still using some unknown and possibly circuitous ground return path.

 

[dbhost]

Grounding is direct to chassis from the DC to DC charging, Giant bolt through the floor with the Sportsmobile I assume at least 1" stainless steel ground strap from that bolt to the frame of the van.

 

[posplayr]

Grounding is direct to chassis from the DC to DC charging, Giant bolt through the floor with the Sportsmobile I assume at least 1" stainless steel ground strap from that bolt to the frame of the van.

In electrical engineering, you start off learning how to analyze "circuits". It is called "circuits" because the electrons flow in complete circuits. So while it might be confusing, a "ground " is not a black hole where electrons disappear.

Rather it is a collection point for all the electrons that are returning to the source (e.g. alternator ground). So there should be another grounding bolt somewhere else on the frame that jumpers to the engine so that the electrons can work their way back to the alternator to complete the "circuit".

Usually, there is an OE ground strap from frame to the (-)battery to the starter and then current goes through the engine block to get to the alternator mounting bolts. Where exactly this other end of the frame ground is that gets to the engine is unclear. The body ground strap to the battery negative is generally not a heavy 6 awg gauge (usually smaller). Maybe the Sportmobile has a corresponding frame strap in the engine compartment. What ever currents are flowing through the frame have to get back to the alternator mounting bolts to complete the circuit.