Combining Relays

[LADYBUG TOO]

There are two Blue Sea Combining Relays (ACR's) on the power distribution board. The top ACR, shown in a post to my album, had a 12 volt connection to the "Remote LED" terminal. I have disconnected that. The lower ACR between the Thruster and Start batteries has a connection to the lock out terminal that appears to have 12 volts on it when the battery switches are on. Is that 12 volts from the thruster controller to lock out the thruster battery when the thrusters are in operation? Am I wrong in assuming that if 12 volts is applied to that terminal then it would never "combine" with the start battery? We started looking at this when we found that the alternator voltage regulator was bad and we were just checking through all the related wiring.

Pat,
Ladybug, Too

 

[Osprey]

My experience is with a R27 , but the 29 likely is the same. Below is my simplified understanding of what the isolation/ combiner relays do. Different relay open/ close conditions can arise depending on the initial voltages.
We have two isolation relays, one between the house bank and the starting battery a second between the starting battery and thruster battery. One or both of the relays can be open or closed depending on the voltage and the duration of the voltage values applied to their sensing terminals. See details of the voltages and times required to open and close the relays on the Bluesea.com web pages. For simplicity, I will only refer to the 30 second voltage values. Further, the design is such that the starter motor can only draw current from the starting battery.
Once the engine has started the entire alternator output initially goes the house bank. After the house bank voltage reaches 13.6V (30 s or faster for higher voltage), the house bank to starter battery relay closes. The house bank and starter battery are now combined. In addition, once the starter battery voltage reach 13.6 V, the starter to thruster relay closes. At this point the alternator is charging all the batteries. The relays remain closed until the sensing voltage to a given relay drops to 12.75 V (30 s - faster for lower voltage). Consequently at these lower voltages, one relay can isolate the house bank from the starter and thruster batteries. and the second relay can isolate the thruster from the starter battery.

 

[SGIDAVE]

Is that 12 volts from the thruster controller to lock out the thruster battery when the thrusters are in operation? Am I wrong in assuming that if 12 volts is applied to that terminal then it would never "combine" with the start battery? We started looking at this when we found that the alternator voltage regulator was bad and we were just checking through all the related wiring.

Pat,
Ladybug, Too

Hello Pat,

This chart, taken from Bluesea.com shows what the LED light status means. To answer your question, if the 12VDC wire connected to the "start isolation" post is ENERGIZED, then the ACR will not close (or COMBINE). The LED on the ACR should be BLINKING if this is the case.

Fair Winds and Functioning ACRs,

/dave

 

[HRowland]

One more point, early tugs had the LED terminal incorrectly connected to 12V via a small fuse, my R27 was built this way. Ranger no longer does this. I used the LED terminal for a LED near the helm so I can monitor ACR state. When lit I know my ACR has combined the engine and house/thruster banks (I no longer have a separate thruster bank). If I see a blinking code then I know an under voltage or over voltage lockout has occured.

It sounds like your R29 was wired incorrectly like my R27, on your second ACR I suspect the wire to the lock out terminal was originally connected to the LED terminal.

Howard

 

[knotflying]

Also, and Howard correct me if I am wrong, on some of the tugs, when on shore power the battery switches have to be on for them to get charged.

 

[SGIDAVE]

Also, and Howard correct me if I am wrong, on some of the tugs, when on shore power the battery switches have to be on for them to get charged.

Mike and Howard,

I'm not disputing the wiring set up...it may well be that the 120VAC battery charger is wired THROUGH the ACRs.

HOWEVER, in doing so, doesn't' this defeat the benefit of, say, a fancy 3 bank multi-stage battery charger which is meant to be wired to each battery bank individually so as to obtain independent, bank-specific charging?

My 21EC originally had 3 battery "banks." One was the start battery, a second was the house battery, and the third was the bank for the 12VDC Air Conditioning system. The VERY NICE factory installed 3 bank 120VAC on board battery charger was wired DIRECTLY to each battery bank. In this manner, the banks are all charged even with the battery switches OFF. In fact, it's BETTER if the switches are off so that the ACRs aren't trying to combine the batteries (make 3 banks into one for charging purposes) like when the Alternator is charging. Oh wait, the switches being OFF only would make a difference if they were wired in BEFORE the ACR...another BIG IF.

Anyway, my point is you could have "smart" 3 or 4 stage charging which is AVAILABLE from your high tech 120VAC charger if it where wired to each bank individually. If not for the ACRs which then work to combine all your batteries into ONE BANK for charging purposes. Again, the "combined" mode of charging WILL WORK but you loose the benefit of independent charging of each bank which you COULD have had.

Probably not worth worrying about...

FAir winds and charged batteries,

dave

 

[HRowland]

Also, and Howard correct me if I am wrong, on some of the tugs, when on shore power the battery switches have to be on for them to get charged.

Yes, some tugs do have the ACRs connected after (load side) of the battery switches. The battery switches would need to be on to charge all the banks if you have a single output charger, such as a combined inverter/charger. In this case if the battery switches are off then only the house bank would charge. Note in this case the inverter battery switch must also be on.

HOWEVER, in doing so, doesn't' this defeat the benefit of, say, a fancy 3 bank multi-stage battery charger which is meant to be wired to each battery bank individually so as to obtain independent, bank-specific charging?.

Yes! In my case (2012 R27) the ACRs are connected directly to the battery terminals. The Pro Mariner ProNautic 1220P charger on my tug has 3 independent outputs, one for each bank. If not for the ACRs each bank would switch between charge states (bulk, absorption, float) independently. However, the ACRs defeat this feature because all of the banks get combined. This is why Blue Sea manufactures a charger that can drive the Lockout (or Start Isolation) terminal on the ACRs to disable them during charging.
In practice it is not a big deal, some of the batteries may get a little more charging than ideal. The life of the engine battery might be very slightly less since it sees a full charge cycle even though it is typically fully charged. Likewise for the thruster batter. Probably not enough to worry about, but if you are a purist you can add an 120VAC coil relay or small 12V power pack to supply 12V to the Start isolation terminal whenever AC power is applied to the charger. You may get slightly faster charging of the house bank since the charger can supply the most current to the bank that needs it the most. This would accomplish the same thing that the Blue Sea charger does.

Howard