an easy question for a Battery GuRu

[ShadowsPapa]

Why do you want to know the voltage of the two batteries separately? As Shadow Papa said, it’s only relevant during an ESS event. If it’s about battery health concerns, then I’d either just get rid of the Aux or replace it with a better unit than the OEM one and keep the truck on a tender.

To me, the Aux battery is like my appendix. It’s not really needed but it’s there. It has only two states I care about: unhealthy/failing AND Okay. I don’t monitor my appendix because the information wouldn’t help me. If it goes bad, I’ll have it taken out and stored in the garage in a jar next to my Aux battery. I don’t think monitoring the Aux voltage would tell you anything helpful. If it’s low, maybe it needs to charge. It’s a small battery, maybe there’s been a lot of ESS events. Voltage drop over time with no load might be a useful metric but you can’t test that the way it’s connected. If I have a thing that I don’t really need and I’m thinking about fabricating stuff for it, then I’m thinking about getting rid of it.

Nice to know if the combined voltage is good because of the aux battery being good, main being bad, or other way around.
You can do a lot of diagnostics based on voltage levels under various conditions - trending, for example.
Some of us simply want to know more about about their vehicle, like to keep track of it. Sort of like oil analysis - not necessary but some of us want to know, and trend things.

I don’t think monitoring the Aux voltage would tell you anything helpful. If it’s low, maybe it needs to charge. It’s a small battery, maybe there’s been a lot of ESS events.

Well, I see a lack of understanding the why and how and what good it does that just isn't going to be satisfied without something long and deep.
In short, yeah, it can be very helpful.
And no, it should charge up quickly - so small is actually going to mean it should charge faster.
Also you obviously missed my prior testing where I showed that even the main battery voltage dropped during ESS events - because it runs the engine fan, EHPS and other fun stuff. I watched the voltage drop almost as much, almost as fast, during multiple ESS events a year ago.
I have yet to do more testing with better rigging than last time.

Anyway, why are you dissing others' wanting to know more about their truck's systems, learning more about the batteries and electric systems?
You don't like it doesn't mean others aren't just fine with it.
Mine works great, as did my 2020 for 2 1/2 years (after I recharged both batteries independently and reset the IBS)

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[Wolf Island Diver]

You can establish monitoring in a series or parallel battery bank using shunts. Victron has articles with diagrams in this. My Renogy system is set up to do this, I’m just not running a second battery yet, maybe never. But I can monitor parallel batteries individually. Renogy provides for this with their battery internals but you can also wire up separate individual monitoring with a shunt.

https://www.victronenergy.com/media/pg/SmartShunt/en/midpoint-voltage-monitoring.html

The point of my previous post was that I don’t think it’s worth the time and money. I’m not “dissing” the OP for “wanting to know more about their trucks systems”. Wiring up a monitor isn’t “learning about how something works” it’s monitoring. And there is such a thing as too much monitoring when the data is too granular to be useful in making a decision. The analogy is in medicine where you’re taught to treat the patient, not the vital signs. There’s lot of ways to learn things without modifying your personal vehicle. A take the OP at face value that this was about monitoring the Aux battery.

The Aux battery only does one thing and it is already monitored by the ESS system. This is why it won’t work under certain conditions. A delta in the availability of ESS over time is the a good indicator that the battery is failing. This is exactly the symptoms described by numerous people here and on other forums prior to a failure of one or more batteries.

You may install monitoring for this battery but the times that you notice low voltage on your gauge for example will also likely be the times that ESS isn’t available. In other words, I don’t think this monitor will give you actionable data in absence of other indicators that you already receive from the vehicle. Hence, why I say it isn’t worth the money. As an DIY exercise for your enjoyment, you do you.

Again, I’m not against ESS in principle. But according to my dealership the system is a liability and they recommended to me that I disconnect the brand new AUX battery they installed under warranty, especially because of the DEF system. This has lot to do with the fact that when an individual cell in 1 battery of a battery bank fails or begins to fail, it can damage the whole bank. These are cheap OEM batteries. You could replace them with better quality batteries and probably worry less about it. However, I personally don’t want any other battery connected directly to my starting battery. When my batteries failed, it progressed from warning messages to a dead truck rapidly. My DEF heater stopped working. Had it happened 24 hours prior, it was below freezing and that would have been a disaster. As one forum member who actually owns the diesel to another, I think this is a really big deal. Had I been off road somewhere, it would have been an expensive tow out, so that’s another consideration. Thankfully, all I ended up with is 2 shredded windshield wiper blades and 2 days of inconvenience.

I’m not trying to patronize anyone here. People can take any advise they want. I do understand how these systems work. I do have practical experience working with DC electrical systems and monitoring primarily for Naval nuclear propulsion. I’m trying provide some practical advice from my experience with this system failing. But no one has any obligation to follow it, nor am I offended if they respectfully disagree. Personally I won’t run this system in any vehicle that’s required to keep certain systems like a DEF heater running all the time or in a vehicle that goes off road. So monitoring of the Aux battery is moot.

 

[SargeDiesel]

To be honest, I first was just curious if it could be done... cheaply with inexpensive digital meters ($10 or less). I just thought it would be "a nice to know" mod. I pay attention to the main battery's voltage and health, so I figured why not the Aux battery.

It seems to be more expensive and trouble than it is worth... I can always get my answer manually if need be.

I appreciate the points of view and the advice of all forum members, so thanks for everyone's input.

 

[Wolf Island Diver]

To be honest, I first was just curious if it could be done... cheaply with inexpensive digital meters ($10 or less). I just thought it would be "a nice to know" mod. I pay attention to the main battery's voltage and health, so I figured why not the Aux battery.

It seems to be more expensive and trouble than it is worth... I can always get my answer manually if need be.

I appreciate the points of view and the advice of all forum members, so thanks for everyone's input.

Yeah, I think ShadowPapa’s description of how you could disconnect it and check it manually isn’t bad idea at all, just to get an occasional state of things. My point was about real time monitoring. It’s never a bad idea to check the batteries during maintenance especially with these OEM batteries. There’s some write ups on adding plugs for battery tenders. I used a magnetic connector for mine because I figured I’d never be forget. It was connected and drive off. But now I’ve got a 100w solar panel charging everything including the starting battery through a DCC50S. That’s an expensive option but a NOCO genius is pretty cheap off of Amazon. The diesels seem to consume a lot of power sitting for more than 24-48 hours.

 

[SargeDiesel]

Yeah, I think ShadowPapa’s description of how you could disconnect it and check it manually isn’t bad idea at all, just to get an occasional state of things. My point was about real time monitoring. It’s never a bad idea to check the batteries during maintenance especially with these OEM batteries. There’s some write ups on adding plugs for battery tenders. I used a magnetic connector for mine because I figured I’d never be forget. It was connected and drive off. But now I’ve got a 100w solar panel charging everything including the starting battery through a DCC50S. That’s an expensive option but a NOCO genius is pretty cheap off of Amazon. The diesels seem to consume a lot of power sitting for more than 24-48 hours.

I really wanted "real time" monitoring... just didn't understand how or if I could easily obtain it. It seems I can not.

I have a semi-permanent (I can remove it if I want to, but its not going anywhere otherwise) pig tail that I plug my NOCO10 into when needed. I bought the NOCO extension cable and have it running down into the wheel well and tucked into a hole in the frame. I can get to it easily and don't have to open the hood to connect the charger.

I have the NOCO10, along with their jump starter. They seem to work well and be of good quality.

I also have a 100w solar panel and a x300 Fremo backup battery bank .

So far (knocking on wood or my head)... I haven't had any battery issues.
For example, I do not drive on a daily basis, I have a 22 with approximately 5,500 miles... I had to go out of town for over a month, when I got home, I was going to plug it in... but decided to crank it up and see (FAFO.. ha ha)
It fired right up, so I have just continued to drive it.

Now I did just order a Scangauge III... it should provide me with some good info for the diesel.

 

[Wolf Island Diver]

I really wanted "real time" monitoring... just didn't understand how or if I could easily obtain it. It seems I can not.

I have a semi-permanent (I can remove it if I want to, but its not going anywhere otherwise) pig tail that I plug my NOCO10 into when needed. I bought the NOCO extension cable and have it running down into the wheel well and tucked into a hole in the frame. I can get to it easily and don't have to open the hood to connect the charger.

I have the NOCO10, along with their jump starter. They seem to work well and be of good quality.

I also have a 100w solar panel and a x300 Fremo backup battery bank .

So far (knocking on wood or my head)... I haven't had any battery issues.
For example, I do not drive on a daily basis, I have a 22 with approximately 5,500 miles... I had to go out of town for over a month, when I got home, I was going to plug it in... but decided to crank it up and see (FAFO.. ha ha)
It fired right up, so I have just continued to drive it.

Now I did just order a Scangauge III... it should provide me with some good info for the diesel.

Their jump starter has saved me when I left lights running. And I like that I can help somebody who needs a jump without risking my own vehicles, electronics. It’s good stuff I work from home so my truck sits which is terrible for the battery. Not great for the diesel either. Pretty much the diesel need a tender.

I got a ScanGauge so I could monitor the DPF loading and know if I’m close to going into regen before going on a trail. I mounted it the grab handle with a CMM ball and this bracket https://absolute-wits-end.com/scangauge-ii-mounting-bracket/. In real world experience my plan hasn’t panned out. I usually forget to look at it and unless you’re right there at the trigger point for regen which seems to vary, you can’t really just drive around on the interstate waiting for the regen before hitting the trail. I mean you can but who wants to do that. Inevitably my truck goes in a regen When I’m creeping up a trail at 5 mph. Part of this is inevitable because the DPF really fills up quickly at low speed. I still think of ScanGauge is pretty useful. You can use it for monitoring the turbo temp before shutdown. You can use it to at least have some idea of where the soot load is. My plan of timing my regens never really worked out. I wish you could force a manual regen of force a regen skip to the next time it hits some predetermined speed.

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