Help me understand my DC charging/depletion

[flightlead404]

Now I’m spending much more time on the hook, trying to be close to 100% until spring, I’m observing unexpected behavior in my battery charging/depletion.

In a nutshell, house and start appear to be acting as a single large bank, charging and depleting as one, remaining at the same voltage. It was brought home to me after I found I needed to start the main engine and rev it up before starting the generator.

I have a “parallel charge circuit” which is a Cole-Hersee 24117-01 SPST NO solenoid. The high voltage terminals are connected between the house battery switch comm/on terminal and the start battery switch battery terminal (wiring diagram shows them both on comm/on terminals). The solenoid is not an ACR per se and has no “smarts” with respect to on/off voltages or hysteresis. The system is behaving like this is “always on” allowing the two banks to charge/discharge in parallel. I expected them to charge in parallel but for house loads to only deplete the house bank.

The solenoid is switched with a yellow and yellow/red wire pair that disappear into a harness with a 6-pin Deutsch connector (pins 4 and 5). In the wiring diagram (dated 2004 I have a 2007) the yellow/red is labeled “disconnect only for 100A alt. option” - I have an 80A alternator an do not have the isolator for the 100a alt option.

How is this solenoid switched?
Is my thinking about how this is intended to work correct? Ie that when there is a charge source the solenoid should be “on” and parallel the batteries, and when no charge source if should be “off” and decouple them?

 

[Johann]

My cat came with similar Cole hersee solenoids for combining the house and start when the engine was running. When voltage is applied across the two smaller the solenoid is energized and the two larger studs are connected. What is applying this voltage in your case I don’t know, but both my solenoids had problems. One failed open, the other only worked intermittently. I understand it is a common issue. In any case, since we were going to Lithium I replaced the solenoids with Victron Orion DC-DC chargers.

 

[ice breaker]

You may have a welded closed solenoid.

 

[DayDreamer41]

The solenoid is closed when the ignition switch is in the "ON" position. Sounds as if your solenoid has contacts which don't open. Replace the solenoid with an ACR.

 

[flightlead404]

Just saw daydreamer41’s post. I was thinking after baking on this for a while is that it is supposed to be energized by the alternator, ie to charge both banks when the engine is running, so that more or less jives with dd41’s post. I’ll confirm it tomorrow, and will remove the solenoid and put a multimeter on it to see if it is indeed bad.

If its bad I’ll replace with an ACR, which will also let me remove the 2nd line from my master volt battery charger and let the ACR manage it, the solar, and potential future wind gen. In the meantime I can just turn the battery switch to OFF once the start battery is fully charged, and only turn it ON to start the engine or generator.

 

[Davidasailor26]

Before you remove the solenoid you could just check the voltage across the posts that energize it. If one of the posts is powered then something is energizing the solenoid when it shouldn’t be. If neither post is powered the solenoid May have failed and seized closed.

 

[DayDreamer41]

@flightlead404 This look familiar

 

[DayDreamer41]

And

 

[flightlead404]

Yes, I have almost that diagram. Slightly different, mine is dated 04 but essentially the same. My actual setup is slightly different. My diagram and the above shows the parallel charge circuit breaker on the switched side of the start battery switch. It is actually connected to the BATT side, which is why even though I turned the start battery off at 95% last night its at 65% this morning. The jumper looks factory and I’m not sure I have the length to move it to the switched side. But opening the parallel charge circuit breaker should have the same effect.

 

[flightlead404]

Yellow/red is energized when engine key in the RUN position as d41 says above.

The solenoid appears to be functioning correctly. That is, no continuity between the two high current posts when key in OFF, zero resistance between them when key is in RUN.

So I’m back to the question of why the start bank is depleting along with the house.

 

[Johann]

Yellow/red is energized when engine key in the RUN position as d41 says above.

The solenoid appears to be functioning correctly. That is, no continuity between the two high current posts when key in OFF, zero resistance between them when key is in RUN.

So I’m back to the question of why the start bank is depleting along with the house.

If the start and house were connected somewhere else, wouldn’t there still be continuity between the two high current posts even if the solenoid was open? Perhaps the issue is in the battery meter?

 

[flightlead404]

If the start and house were connected somewhere else, wouldn’t there still be continuity between the two high current posts even if the solenoid was open? Perhaps the issue is in the battery meter?

Yeah I’m trying to identify oddities. The battery meter is a single gauge with an MOM-Off-MOM switch to select which battery is being tested. I don’t believe that’s an issue.

There are two heavy gauge cables on the switched side of the start battery switch, one looks factory, the other doesn’t. One of them is the starter, unsure what the other is. Could be a separate run for alternator, but normally I would expect the alternator output to just connect to the starter positive post and share a single heavy gauge run to the battery.

 

[DayDreamer41]

Stating the obvious, where do both cables go from the switched side of the start battery switch? one to the start battery, but where does the other go? the picture of my start battery switch only has the single cable to the start battery connected to the switch.

 

[Maine Sail]

Just saw daydreamer41’s post. I was thinking after baking on this for a while is that it is supposed to be energized by the alternator, ie to charge both banks when the engine is running, so that more or less jives with dd41’s post. I’ll confirm it tomorrow, and will remove the solenoid and put a multimeter on it to see if it is indeed bad.

If its bad I’ll replace with an ACR, which will also let me remove the 2nd line from my master volt battery charger and let the ACR manage it, the solar, and potential future wind gen. In the meantime I can just turn the battery switch to OFF once the start battery is fully charged, and only turn it ON to start the engine or generator.

This will walk you through how an ACR works:
https://marinehowto.com/automatic-charging-relays/

 

[flightlead404]

Stating the obvious, where do both cables go from the switched side of the start battery switch? one to the start battery, but where does the other go? the picture of my start battery switch only has the single cable to the start battery connected to the switch.

Start battery switch Common side has two cables, one to the main engine starter the other to the generator

Start battery switch Batt side has three connections. The battery obviously, the cable from the A/C battery charger, and the parallel charge circuit breaker.

I ran both house and start up to absorption with the charger running off generator.Now has turned off the batt switch and pulled the parallel charge circuit breaker. Will see what it’s like in the am.

 

[flightlead404]

Overnight down to 70% on the house, which is a big loss for running anchor light, fridge, and freezer, but start battery still at 100%.
So, issue is either with the parallel charge circuit or something on the switched side of the battery switch (engine and generator starters).

 

[Hello Below]

Overnight down to 70% on the house, which is a big loss for running anchor light, fridge, and freezer,

With these overnight loads and given your total house bank capacity, what would you expect the SOC to be in the morning?

 

[flightlead404]

With these overnight loads and given your total house bank capacity, what would you expect the SOC to be in the morning?

I haven’t actually done the math but around 20% was my experience last year. I have two Dec 2019 210 aHr AGMs that were in great condish but I am afraid a power outage on my dock over the summer had them cycling down to 30% SOC before I was able to get there and may have degraded their performance. A de-sulphation may be in order.

 

[Hello Below]

I haven’t actually done the math but around 20% was my experience last year. I have two Dec 2019 210 aHr AGMs that were in great condish but I am afraid a power outage on my dock over the summer had them cycling down to 30% SOC before I was able to get there and may have degraded their performance. A de-sulphation may be in order.

That is a significant change; however, I wouldn’t think that a single cycle below 50% SOC would negatively impact even AGMs that much. The math is important and will help in directing what needs to be fixed if anything.

 

[flightlead404]

To close this out, bad parallel charge solenoid. It isn’t a perfect connection, hence my elimination of it early on, doesn’t beep a continuity tester, it’s a higher resistance connection but enough to leak current from start to house.

will replace with an ACR if it’s plug and play and all the existing cables and terminations work, otherwise with a new solenoid at least temporarily