New Group 31 battery not sustaining voltage to aux battery as well as old Group 27 battery (1 Viewer)

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Trying to figure out what's going on here and whether I have an issue.

I recently upgraded my old OEM battery to a group 31 standard lead-acid. I also upgraded to the Slee extended battery terminals, whereas previously all my accessories were connected directly to the posts. The battery was manufactured in August, and I had let it charge for a few hours after installation.

I have a heavy-gauge wire running from the battery into the cabin, where it connects to a Victron DC-DC charger. This charger converts the starter battery voltage to 24V and then sends those volts to my Goal Zero 1500x via the Anderson-like input. I can monitor the voltage coming in and going out of the charger on the Victron app.

Previously, with the old battery, the app would show 13.7V coming in from the starter battery, regardless of whether the charger was on at the time and putting out its ~380 watts at 24volts. Now, with the new battery, I get 13.7V when the charger is off, but the volts drop to 12.7 when I turn the charger on.

Nothing has changed in the aux system. No wires were touched. So, why would I be getting this 1-volt drop now and not previously? Anyone have any ideas?

For the first time, I am also experiencing weird behavior on the Victron app. The output will show 24V as soon as I turn on the charger. Then, as the voltage coming in drops to 12.7 over about 7 seconds, the app will show a dash in the output display, as if no volts are going out. But the volts are going out, and I am getting the full 380 watts into the Yeti. I can see this on the Yeti itself as well as on the Yeti app.

Troubleshooting note: To test the new battery after finding this issue, I parked the car and turned on EVERYTHING: seat heaters, heating, all offroad lights (a lot of them!), high beams, rear defroster, etc. During this test, my voltage dropped incrementally from 13.7V to 13.4, as monitored inside the cabin at the DC-DC charger input point with the charger turned off. Then I turned on the charger, dropped a volt again, and found the maximum output I was getting was 180 - 240 watts instead of the 380. Turning off some of the accessories brought the charger back up to 380 watts. So I seem to have found the limit of my available current at idle in this test. (Not sure if this test provides any relevant information at all. I have no baseline test with the OEM battery to compare it to.)
 
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I’ll take a WAG and suggest you clean and retighten all connections to the new battery terminals, including the terminal to post connections. A bad connection there, or problem with the terminal ends on the heavy wires, could lead to those symptoms.
 
I’ll take a WAG and suggest you clean and retighten all connections to the new battery terminals, including the terminal to post connections. A bad connection there, or problem with the terminal ends on the heavy wires, could lead to those symptoms.
Gonna give this a try, for sure. As noted in another post, I make a couple mistakes in installing the tray, so I'll have to do this anyway.
 
I’m just surfing through the headlines here, no experience with 200’s.
But I’m curious as to why you are or what are you running at 24V?
 
I’m just surfing through the headlines here, no experience with 200’s.
But I’m curious as to why you are or what are you running at 24V?

Doesn't have to be 24V exactly, but the Yeti 1500x requires at least 14V when using the high-power charging port. Prior to the upgrade, the system was working great for me for many months.

The Victron can be adjusted to output less--for example, 20V--without changing the watts going into the Yeti or the issue I'm having at the moment.
 
I went to dual series 31 and a 120A alternator. Charging output depends on what’s required,
but your system is far more complicated than mine. I have a primitive electrical understanding at
best
 
there seems to be some resistance at the terminals if nothing else has changed - that or the G31 battery in incapable of the voltage (i.e. internal resistance or something)... those are the only 2 electrical items you changed.
Test it first by putting the G27 back in on the New Terminals and then you should be able to tell which system is causing it (if results are the same with the G27 - then switch back to the old terminals..)
 
A conundrum for sure.

Make sure to check the ground points all around. Many electrical system anomalies have been traced to this.

Can you give us a few more data points?

What G31 battery are you running?

Using a multi-meter
1) Can you tell us what the G31 battery voltage is at rest (car not on)
2) When you see the voltage drop at the DC-DC charger, does the multimeter agree when referencing the battery posts itself?
3) Can you turn on the DC-DC charger when car is off and tell us the voltage drop reported at the DC-DC charger and at the battery posts?
 
A conundrum for sure.

Make sure to check the ground points all around. Many electrical system anomalies have been traced to this.

Can you give us a few more data points?

What G31 battery are you running?

Using a multi-meter
1) Can you tell us what the G31 battery voltage is at rest (car not on)
2) When you see the voltage drop at the DC-DC charger, does the multimeter agree when referencing the battery posts itself?
3) Can you turn on the DC-DC charger when car is off and tell us the voltage drop reported at the DC-DC charger and at the battery posts?


Thank you for the help here, @TeCKis300. I will conduct these tests soon. I'm also picking up a fresh set of terminal adapters today--the Deka brand, which are lead and identified as being for group 31. It might be worth noting my generic Amazon adapters are zinc.
 
Thank you for the help here, @TeCKis300. I will conduct these tests soon.

I did some troubleshooting today, including your tests @TeCKis300.

I redid all the input and output connections at the charger point. I also redid the connections on the switch in between the charger output cable and the Yeti. I also redid the installation of the battery billets and cable on the starter battery. None of this changed the outcome.

The multimeter shows the following at the starter battery terminals:
  • When the car is idling
    • and the charger is off: 13.82V
    • and the charger is on: 13.7V
    • Delta: 0.12V
  • When the car is off
    • and the charger is off: 12.6V
    • and the charger is on: 11.3V
    • Delta: 1.3V
The 0.12V delta at the terminals when the car is idling compares with a 1.0V delta at the charger (13.8 charger on vs 12.8 charger off [numbers based on what the charger sees at its input point]).
 
I did some troubleshooting today, including your tests @TeCKis300.

I redid all the input and output connections at the charger point. I also redid the connections on the switch in between the charger output cable and the Yeti. I also redid the installation of the battery billets and cable on the starter battery. None of this changed the outcome.

The multimeter shows the following at the starter battery terminals:
  • When the car is idling
    • and the charger is off: 13.82V
    • and the charger is on: 13.7V
    • Delta: 0.12V
  • When the car is off
    • and the charger is off: 12.6V
    • and the charger is on: 11.3V
    • Delta: 1.3V
The 0.12V delta at the terminals when the car is idling compares with a 1.0V delta at the charger (13.8 charger on vs 12.8 charger off [numbers based on what the charger sees at its input point]).

Am I understanding this correctly.

When the car in on and idling.

Charger off:
Voltage reference at battery post vs the input of the DC-DC charger is 13.82V to 13.8V respectively.

Charger on:
Battery post vs charger input is 13.7V vs 12.8V

The voltage drop on the positive wire from the battery to the charger is suspicious and indicates pretty high resistance in that path somewhere.

I would check for any voltage drop there across the slee extended terminals, wire, anderson connector, to see if you can't isolate where the problem is.
 
@TeCKis300 No, that's not quite it. Sorry if my presentation of the data was confusing.

When the vehicle is idling and the charger is off, the voltage at the battery post is 13.82V (per multimeter), and the voltage at the charger is 13.8V (per Victron app). So the loss of voltage is only 0.02V, with the caveat that two different instruments are being used for the measurements. (I'm using a heavy gauge cable for the wire run. This cable is actually designed for higher wattages than I'm using.)

When the vehicle is idling and the charger is turned on, the voltage at the battery post drops only 0.12V to 13.7V. However, the voltage at the charger drops a full volt to 12.8V.

So, there is a discrepancy between the battery post and the charger input point that only arises when the charger is turned on.
 
I should report another factor that may or may not be related. This just came to my awareness yesterday.

Yesterday, when using a hair dryer in my Goal Zero 1500x power station (the aux battery being discussed above), the meter on the battery initially said 93% charged. I was drawing 1490watts for about 7 minutes, which was well under the power station's limits. However, the power station suddenly failed, showing 0% on the meter. It should have only gone down to about 80% at the worst.

I called Goal Zero tech support about this, and they said to cycle the battery a few times (drain, charge, and repeat...) to restore the battery's calibration.

Is it possible the 1500x issue is somehow behind the issue at hand?
 
@TeCKis300 No, that's not quite it. Sorry if my presentation of the data was confusing.

When the vehicle is idling and the charger is off, the voltage at the battery post is 13.82V (per multimeter), and the voltage at the charger is 13.8V (per Victron app). So the loss of voltage is only 0.02V, with the caveat that two different instruments are being used for the measurements. (I'm using a heavy gauge cable for the wire run. This cable is actually designed for higher wattages than I'm using.)

When the vehicle is idling and the charger is turned on, the voltage at the battery post drops only 0.12V to 13.7V. However, the voltage at the charger drops a full volt to 12.8V.

So, there is a discrepancy between the battery post and the charger input point that only arises when the charger is turned on.

Thanks for the clarification. We're not talking past each other and that is how I'm understanding it.

The .12V delta is a good cross check that confirms apples to apples when the charger is off.

The 1V drop when the charger is on - suggests high resistance somewhere as I said earlier. It's not as likely the wire itself if you've sized it appropriately. It's often the terminals or connections. It could still be the ground path depending on how you're measuring voltage.

Take your voltmeter, and measure across stuff to isolate where you see the most voltage drop (while the charger is on).

If testing the anderson for example, probe the back side of each terminal to read the voltage delta (if any) across the junction. If the leads on your meter are long enough, or even extend it with a bit of wire, measure the drop directly with one probe at the battery post and then input of the charger.
 
Maybe the charger failed?
I had one fail so now I carry a bypass wire on trips
 
Well, after further testing with a multimeter, as @TeCKis300 suggested, I believe the issue is the Goal Zero power station that I'm charging.

The voltage measured at the aux end of the wires from the starter battery is almost identical to the voltage at the starter battery terminals. This voltage is also the same as the voltage at the terminal input points on the aux charger after the wires are attached to it. Additionally, the output setting of 20V set in the charger app is almost exactly what I'm getting at the Anderson connector that plugs into the power station--when the connector is not actually plugged in. Once the connector is plugged in, the voltage issues occur. There is no wiring or grounding downstream of the power station--nothing further to test beyond it. So it seems the power station must be causing the fault.

When this reasoning is considered alongside the additional battery issue that I just got (sudden drop to 0%), I think the answer is clear. I'm guessing the power station MPPT, or some associated internal part, has gone wonky. Or maybe the input port on the power station has gotten loose.

It's likely the timing of this issue with my new starter battery replacement was a coincidence. Or maybe I only noticed it because I was testing everything.
 
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So, another bit of clarity on this situation. After taking more measurements, I think I figured out a little more precisely what's happening.

The Victron puts out my choice of any voltage in the 20V to 30V range. Meanwhile, the Anderson-like input on the Goal Zero Yeti is rated for 14V-50V. This input is connected to Yeti's internal MPPT. I just discovered that, for some reason, the Yeti's MPPT is converting the incoming voltage to 16V, even though it can easily handle the 20V to 30V and the full current delivered at those voltage's by the Victron. The 16V is below the Victron's minimum output; so that explains why I'm seeing a dashed line on the output measurement in the Victron app. Meanwhile, since the Yeti is changing the voltage being returned through the negative wire to the Victron, maybe this voltage drop is what's causing the appearance of a 1V drop coming in from the starter battery. (I can't fully explain the latter phenomenon, so I'm speculating on that.)
 
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For your latest post, I think your Victron is underspecified for the job. I'd suggest replacing the Victron with Yeti's Vehicle Integration Kit. Hope this explanation makes sense. Happy to go into more detail.

1666037017629.png

But about the 1V drop at the input of the DC/DC, I agree with TeCKis300 that there's likely a bit of resistance somewhere in the connections to cause that droop. Since the voltage drops when the charger is passing current, it points pretty squarely at resistive losses.
 
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I think your Victron is underspecified for the job. I'd suggest replacing the Victron with Yeti's Vehicle Integration Kit. Hope this explanation makes sense. Happy to go into more detail.

View attachment 3143114

Great diagram, @daneo . Thank you!

I have the car integration kit too. In fact, it's the cable from that kit (with connectors replaced) that I'm using for the run from the starter battery to the Victron.

I had a few issues with the kit over many months of usage. First, the connection between the cord and the input in the back of the power station got loose. Second, That input doubles as the connection point with the expansion tank, which I use on occasion, resulting in a number of convenience and complexity issues. Third, I had a couple instances of starter battery drain, which may have been related to the kit, though I'm not sure.

The Victron approach has been much more set-it-and-forget-it for me, even if the charging is 1/3 slower.
 
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