Need feedback - PROISO to 2 ACR system layout

[JackConnick]

I have 2x Cummins 5,9BT 210 engines with newish 90 amp 10si alternators, 2x G31 Odyssey start Batteries and a 600amp AGM L14 house bank, 1 G24 SLA start battery for the generator - 4 banks altogether. 12v system.

I have a Victron Phoenix 50/3 charger for topping up the start banks and a Victrom Multiplus 12/3000/120 for the house.

I had all of this redone and wired a couple of years ago and they installed a PROISO 120/4 isolator. But I've never gotten anywhere near the charging capacity I should be getting from the 2x 90 amp alternators. Real world maybe 150 amps or so to start bulk charging. Lots of issues, they had the alt sense going to the start batteries, not the house, proiso choking to a max of 120amps, uneven charging (one at 70 amps, one at 35).
So I want to pull the PROISO and use 2x ACR ML relays. I'm hoping to get 30-50% better output.

I've been playing with AI designing the new system. I have a lot of fusing cables etc that can be reused. But I wanted to get some real-world feedback on the design and fusing. Not sure if I'll do this myself or find a tech. (that doesn't charge $200/hr).

Let me know any feedback, or if others have installed this system.
------
Legend:
ACR1 = ML-ACR #1 between Start A <--> Start B (Engine Isolation enabled)
ACR2 = ML-ACR #2 between Combined Start Bus <--> House Bank
PHX = Phoenix 50/3 charger (3 isolated DC outputs)
-------
FULL SYSTEM — Twin Engines, Dual ML-ACR 500A, Phoenix 50/3
(ABYC: battery fuses at battery +, alternator protection if mountable, control wiring fused)

PORT ENGINE STBD ENGINE
90 A Alternator 90 A Alternator
(Alt B+ stud) (Alt B+ stud)
| |
(if alt fuse @ alt: 125A ANL @ ALT B+) (if alt fuse @ alt: 125A ANL @ ALT B+)
| |
protected 2 AWG run protected 2 AWG run
(wire sized per battery fuse) (wire sized per battery fuse)
| |
+---------------+-----------------------------------------+---------------+
| |
+-------+-------+ +-------+-------+
| START BAT A | | START BAT B |
| G31 100 Ah | | G31 100 Ah |
| FUSE @ BAT+ |-- 150 A (Class-T / ANL) --+ +---- | FUSE @ BAT+ |
+---------------+ | | | +----------------+
| | |
PHX OUT1 40–50A | | | PHX OUT2 40–50A
(fused at PHX) --6AWG-|-------------+ |-- 6AWG ---(fused at PHX)
| | | |
| +-------------+--+
| (logical node; exists when ACR1 closed)
|
----------------- ACR1 (ML-ACR 500A) -----------------
| A stud <-- Start A + (after 150A battery fuse) |
| B stud <-- Start B + (after 150A battery fuse) |
| EI engine-run sense inputs (16 AWG from each) |
| Manual/Isolate input (16 AWG, 1–2A fuse) |
| When EI active (both engines) -> ACR1 OPEN |
-----------------------------------------------------
|
*** COMBINED START BUS (when ACR1 closed) ***
|
PHX OUT3 40–50A MIDI --- 6 AWG (optional) ---> GENERATOR BANK +
(fused at PHX)
|
+------------------------+------------------------+
| |
| ACR2 (ML-ACR 500A) |
| A stud <-- Combined Start Bus (heavy cable) |
| (e.g., 2/0 AWG) |
| B stud --> HOUSE BAT + |
| (FUSE @ HOUSE + : 300A Class-T within 7") |
| Manual/Isolate input (16 AWG, 1–2A fuse) |
| Control accepts Phoenix 12V "charge active" |
+-------------------------------------------------+
|
HOUSE BAT + terminal
[FUSE AT BAT + : 300 A Class-T (within 7")]
|
HOUSE BANK (600 Ah AGM)
|
HOUSE DC BUS / INVERTER (Multiplus II) / loads
|
COMMON NEGATIVE BUS (all - tied here)

CONTROL LOGIC (low-current wiring / tinned 16 AWG)
Phoenix "Charge Active" +12V -> 1–2A inline fuse -> 16 AWG -> SPLIT to:
-> ML-ACR #1 manual/isolate input (forces ACR1 OPEN while PHX charging)
-> ML-ACR #2 manual/isolate input (forces ACR2 OPEN while PHX charging)
(If Phoenix can't source both, use small 12V SPDT relay driven by PHX charge-active;
relay contacts feed ACR manual inputs.)

ENGINE ISOLATION (EI) for ACR1
- Run 16 AWG tinned engine-run sense wires from each engine run/ignition or alternator sense
to ML-ACR #1 EI terminals per Blue Sea instructions.
- With both engines running, EI forces ACR1 OPEN so each alternator charges its own start battery.

IMPORTANT ABYC FUSE & WIRING RULES (high-level)
- All battery positive conductors fused at battery + within 7" (battery main fuse).
Start A + : 150 A Class-T/ANL
Start B + : 150 A Class-T/ANL
House + : 300 A Class-T
- Alternator fuses (125A) only if mountable within 7" of alternator B+; otherwise size run wire
to battery fuse ampacity (e.g., 2 AWG for 150A).
- Phoenix DC outputs each fused at the charger (40–50A MIDI fuses).
- ACR control wiring protected 1–2 A inline fuse.

QUICK TEST / COMMISSIONING (summary)
1) Install/torque ACR studs & lugs with battery fuses removed.
2) Fit battery main fuses at each battery + within 7".
3) Connect alternator runs sized per fuse; fit alternator fuses if mountable within 7".
4) Connect Phoenix outputs to Start A, Start B, Generator bank (each fused).
5) Wire Phoenix control to ACR manual/isolate inputs (or to relay coil).
6) Connect EI sense wires to ACR1.
7) Tie all negatives to common negative bus.
8) Test engines single/run/both; Phoenix on/off; confirm ACR behaviour and no backfeed to House while Phoenix charging.

 

[Mac2]

What is a PROISO? Sorry if I missed it, but do you have alternator regulators?

 

[JackConnick]

It’s a step diode isolator. Supposed to spread power around banks as needed. No external regulators, they might be added later. This is more bang for the buck.

 

[DDW]

Is the PROISO a silicone diode, Schottky diode, or FET isolator? If not FET, I'd first consider replacing it with a FET isolator, which has far less voltage drop than the diode versions.

I've had many issues with ACRs, specifically the ones you are considering, because the switching voltages are set too low for AGM, and won't work at all should you go to LFP batteries (and you will, someday). They also have some odd behavior when manually or electrically locked off.

90A 10Si alternators aren't going to put out 90A continuously no matter how hard you flog them. I'd expect <60A once warm, you probably have 20 or 30A load when running so 60 x 2 -20 = 100A is about the most to hope for, even if externally regulated. Just for reference I had a 28Si alternator, 160A rated and 178A tested output, externally regulated and well tuned, and could get about 95A into the batteries continuously once everything was warmed up and settled. 105A if I really wanted to push the alternator temperature.

 

[Mac2]

Jack: I got a headache trying to understand your post. Are you asking how to work with what you have, or are you asking for a new “best” system?

 

[SteveK]

I see too many components. You have internal regulated ALT's and AGM batteries, all compatible devices.
I have AGM start and LFP house which requires an in between charger like DC2DC for the LFP charging. I have made one start bank with 2 batteries for both engines. Port ALT to engine start battery, SB to GEN start battery, then from both DC2DC 60A to charge the LFP bank.

I suggest consider combining the two G31 for starting both engines, have both ALT feed direct to the house bank and use the PROISO from house bank to to charge engine start and GEN start batteries.
Engine and GEN start batteries will fill fast and you are left with whatever the two ALT is able to provide.

When I did both ALT to one battery without isolator I noted both going full out as one alone would do until close to full charge when one ALT took over to finish.

 

[JackConnick]

The proiso is nothing more than a stepped voltage sensitive combining relay. For added complexity and additional failure points the units often have multiple relays in one box and it's installed in-between the alternator and the bank not between batteries like other charge management devices... The PI or PS combines batteries based on voltage in a priority order or steps. It waits until each battery has come to 13.3V before bringing another bank on-line. Mine does limit the max combined amps to 120.

Right now with it, once I moved the excite/sense wires over to the house bank, I can get a max combined bulk charge of around 100 or so amps.

 

[SteveK]

The proiso is nothing more than a stepped voltage sensitive combining relay. For added complexity and additional failure points the units often have multiple relays in one box and it's installed in-between the alternator and the bank not between batteries like other charge management devices... The PI or PS combines batteries based on voltage in a priority order or steps. It waits until each battery has come to 13.3V before bringing another bank on-line. Mine does limit the max combined amps to 120.

Jack, try it like I suggested and then tell me it does not work. It will still be connected to the ALT as the ALT feeds are to the where it will get the input. It may not turn on until the house bank is satisfied. Start batteries can wait.

 

[JackConnick]

Steve I don’t believe you can wire the proiso that way. You could with Acrs I think.

 

[JackConnick]

Jack: I got a headache trying to understand your post. Are you asking how to work with what you have, or are you asking for a new “best” system?

Either way. Just trying to see if I can get more amps.

 

[JackConnick]

I've had many issues with ACRs, specifically the ones you are considering, because the switching voltages are set too low for AGM, and won't work at all should you go to LFP batteries (and you will, someday). They also have some odd behavior when manually or electrically locked off.

It says software controlled, so I’m assuming FET. Good to know about the ACRs as I was assuming that was what I need to move towards LFP eventually.

 

[DDW]

Is it a ProMariner product? Those all seem to be simple diodes.

 

[JackConnick]

Yes, promariner. No they have these:

The ProIso Charge series allows you to save space and time by eliminating traditional diode-based isolators and typical voltage loss while still charging multiple battery banks simultaneously.

Seamless charging of up to 4 battery banks
0.0% voltage drop insuring maximum charging capability

The ProIsoCharge is installed between the charging source and multiple battery banks. The ProIsoCharge is activated by the ignition feed (key on position) indicating to the unit that charging will begin. When the unit is off, it draws no power. The unit will self-test on each start-up, and begin assessment of the connected batteries conditions.
Beginning with the Start Battery, the unit will charge to 13.3V and then begin charging the second bank and then the third. Once all banks are at least 13.3V, the unit brings all 4 banks on line for charging. This process could take seconds or minutes depending on the state of charge of each bank. The solid state circuitry can also control backfeeding or when a heavy load such as a windless
attempts to draw from a neighboring bank; the unit will direct the charge to the bank underload. After the bank under load is fully charged, the rest come on line.

ProIso™ Charge 130-4
Part # 23127

The ProIso Charge 130-4 provides 130 Amps to four independent battery banks from two alternators in a 12V DC system.

I have a little older 120 amp version.

 

[l00smarble]

I was not able (willing maybe) to follow the whole post but if you are getting 150amps out of two 90amp internally regulated alternators (75a each) you are doing really well. There isn't much room for improvement here. If you are expecting to get 90a out of a 90a alternator you will have to change expectations rather than change the system.

 

[DDW]

OK, found that, unfortunately their documentation is nearly devoid of specs of any kind. I can guess that it had FETs switched on in sequence to charge the four outputs. There are only two numbers given, 120A, and 0.0V drop. That leaves tons of questions unanswered: 120A input on one alt, two alts, summed together? 120A output total among 4 outputs, 120A for any individual output? 0.0V drop at full input? output? something less? I've seen stone axes with more documentation.

The most charitable interpretation is that it can take up to 120A in either of two inputs, and put out 120A to any output, with 0.0V drop. If so, your output at least is exceeding the spec of the part. Which could mean that the drop is greater than 0.0V. You can test this: get the batteries discharged enough to demand full alt output, 60% SOC is probably enough to do this for awhile. Start and get it charging at max, then put a voltmeter across from the alt input of the device to the bat output. If it is meeting spec that should read 0.0V drop. You can afford about 0.1V drop, but AGMs are sensitive to charge voltage and 0.2V drop is sufficient to lower the charge acceptance a fair amount. If it is charging at 150A or whatever your max is, and still <0.1V drop, then that device isn't your problem.

Best guess is still that the alternators are putting out all they can, and the 90A rating, like all alternator ratings, is a fantasy reserved for very cold starts and lab conditions.

 

[JackConnick]

OK, found that, unfortunately their documentation is nearly devoid of specs of any kind. I can guess that it had FETs switched on in sequence to charge the four outputs. There are only two numbers given, 120A, and 0.0V drop. That leaves tons of questions unanswered: 120A input on one alt, two alts, summed together? 120A output total among 4 outputs, 120A for any individual output? 0.0V drop at full input? output? something less? I've seen stone axes with more documentation.

The most charitable interpretation is that it can take up to 120A in either of two inputs, and put out 120A to any output, with 0.0V drop. If so, your output at least is exceeding the spec of the part. Which could mean that the drop is greater than 0.0V. You can test this: get the batteries discharged enough to demand full alt output, 60% SOC is probably enough to do this for awhile. Start and get it charging at max, then put a voltmeter across from the alt input of the device to the bat output. If it is meeting spec that should read 0.0V drop. You can afford about 0.1V drop, but AGMs are sensitive to charge voltage and 0.2V drop is sufficient to lower the charge acceptance a fair amount. If it is charging at 150A or whatever your max is, and still <0.1V drop, then that device isn't your problem.

Best guess is still that the alternators are putting out all they can, and the 90A rating, like all alternator ratings, is a fantasy reserved for very cold starts and lab conditions.

Yes their specs leave a lot to the imagination. I'm pretty sure its 120 amps total output. My output at about 60% SOC was 100 amps between the two alts (70/30).