charging question

[ftornabe]

Hello,

A couple of questions regarding charging.

When would I use the emergency parallel switch? It is my understanding that when boat is underway all batteries including the thruster battery is being charged. With that said why would I turn on the parallel switch to charge the battery? I usually put it on when returning to the dock as I expect will need the bow thruster to dock (especially with my docking skills) and want to ensure full thruster battery power. Is this good practice?

What are the requirements for solar panel to start charging? All Batt switches off or just the one being charged?


I have a 2021 25' Ranger Tug

Thanks!!

 

[Rocky]

The primary reason for the parallel switch is for starting with a bad start battery.
For example, for some reason your start battery looses charge after a couple days at anchor. You can turn "on" the parallel switch and use the house battery to start the engine.

Then switch it back to "off" and let the alternator charge everything as normal.

There is another reason - lets see if I get this right - if the house batteries get low enough to "trip" the ACR's, then you would put the parallel to "on to allow the house bank to charge enough (engine running) to reset the ACR.

If I have the ACR situation stated wrong - please correct me. I have not had that issue yet.

Thanks!!

Rocky

 

[CruisingElvinRay]

Andrew Custis did a great webinar on power and mentioned that he turns it he parallel switch on underway, but I don’t remember why. The webinar is a available here.

I have never used that switch, and would only use it in the case of a dead starter battery.

https://youtu.be/Uj_am-ecSt4


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[Submariner]

There is another reason - lets see if I get this right - if the house batteries get low enough to "trip" the ACR's, then you would put the parallel to "on to allow the house bank to charge enough (engine running) to reset the ACR.

If I have the ACR situation stated wrong - please correct me. I have not had that issue yet.

The ACR's (automatic charge relays) are basically an automatic parallel switch. Their purpose is to automate the charging of all three battery banks (engine, house and thruster). There is an ACR between the Engine and House, and another in between the house and thruster.

Sometimes you may need to use the emergency parallel switch to bypass the ACR. Here's an example.

You were at anchor for the night. You wake up and your house battery bank is low. You need to run the windlass to weigh the anchor. You turn on the engine, so it's at idle. At this point, the ACR would sense the engine charging voltage and would close, allowing the engine to charge the house bank. Then you start using the windlass. Next thing you know, the chart plotter and VHF radio turn off/on, and you see a low-voltage alarm pop up on your chart plotter just before it powers off.

What happened is, once the windlass started turning, it draws from the house bank. That would have caused a major voltage drop on the house bank due to the large electrical needs of the windlass. The ACR would sense this voltage drop and to protect the engine battery from the sudden drop in voltage it would open. This leaves you with an idling engine and isolated battery banks, thus, your engine is running but is no longer charging the house bank. The solution here is when your house bank is low and you need to run something large like the windlass, you would use the emergency parallel switch to parallel the engine and house battery banks together, bypassing the ACR, so the idling engine can output electrically directly into the house bank. Once done retrieving the anchor you would then put the emergency parallel switch back to off and let the ACR's operate normally.

 

[sjreib]

Really good information; thanks for posting. Knowing when to use the parallel switch can be a life(cruise) saver.

 

[Submariner]

Andrew Custis did a great webinar on power and mentioned that he turns it he parallel switch on underway, but I don’t remember why.

If I remember correctly, Andrew mentioned this in the context of getting hot water on an outboard powered boat. The hot water heater on an outboard only works off AC/120 volt power. To get hot water without shore power, one needs to turn on the inverter and the hot water heater.

The hot water heater will draw about 65 amps when it's heating water. The engine will put in between 30 and 45 amps (depending on whether it's the F200 or F250/F300) when on plane, cruising. The ACR will sense the voltage drop that will occur as a result of powering on the hot water heater and thus the ACR's will open to protect the engine battery, thereby isolating the house bank. Said differently, while underway, up on plane, cruising... the engine alternator would not be charging the house bank with the hot water heater heating water because the ACR's will isolate the house from the engine battery bank due to the large voltage drop that occurs.

The solution is to use the emergency parallel switch to parallel the engine and house banks while you're out cruising up on plane. This bypasses the ACR's and will put 30-45 amps from the engine directly into the house bank to help power the inverter to run the hot water heater.

If you leave the dock with the hot water tank hot, the load on the boat is not all that great since the heater will turn on/off to just maintain temp. If you left the dock with the hot water tank cold (45 degree water/ambient temperature), that hot water heater will run for just under 90 minutes and would consume about 120 amps which is enormous. I recommend against ever doing this. Always leave the dock with hot hot water if you want any hot water at all.

You could leave the dock with a tank of hot water, parallel the engine and house bank, turn on the inverter/hot water heater, and cruise to your destination. That'll ensure that you have a full tank of hot hot water upon arrival at your destination without causing an enormous drain on the house battery bank. The hot water will stay hot for about a day in the insulated tank.

 

[Submariner]

There is another reason - lets see if I get this right - if the house batteries get low enough to "trip" the ACR's, then you would put the parallel to "on to allow the house bank to charge enough (engine running) to reset the ACR.

If I have the ACR situation stated wrong - please correct me. I have not had that issue yet.

There is an under voltage lock-out on the ACR as well. If voltage falls to 9.5volts or less, the ACR will lockout and will not close, thus, the battery bank will never get charged. At 9.5 volts, it's probably a dead battery and this is the ACR's way of protecting the other battery banks. To reset the lockout you would need to bring up the voltage above 9.5volts without the use of the ACR to charge that battery bank.

Best way to think about this would be to consider the thruster battery. If it's voltage fell below 9.5 volts, the ACR would lockout the thruster battery. Meaning, the ACR would never close. You would either need to replace the battery with one that has voltage above 9.5volts. You could use jumper cables to charge the thruster battery above 9.5 volts. The battery charger (when connected to shorepower) does have a direct line to charge each battery bank individually, which is another way to get above 9.5 volts.

A fully discharged deep cycle battery would read 10.5 volts. So 9.5 volts is less than zero, and probably indicates a battery in need of replacement.

 

[Submariner]

I usually put it on when returning to the dock as I expect will need the bow thruster to dock (especially with my docking skills) and want to ensure full thruster battery power. Is this good practice?

What are the requirements for solar panel to start charging? All Batt switches off or just the one being charged?

The emergency parallel switch combines the house and engine battery banks. The thruster battery is all by itself in a third battery bank without a parallel switch. Paralleling the engine and house battery will have no effect on the thruster battery. There is no need to parallel engine and house banks while docking.

For the solar panel, it's always charging the house bank (and 10% goes to the engine battery) when there's sunshine. The solar controller is effectively a battery charger with sunshine as the source. As long as there is sufficient sunshine, and there is sufficient capacity of the batteries, the solar will charge the house and engine bank. If the batteries are at 100%, and there is full sunshine, the solar controller will prevent the batteries from being overcharged. Solar charging occurs even if the house and engine battery switches are OFF. The solar controller is wired directly to the house bank and engine battery on the unswitched side of 12volts DC (as it should be).

 

[CruisingElvinRay]

BTW, to add to Submariner’s solar comments: because the solar controller is wired directly to the house bank, you should cover the solar panels with a blanket, or something similar, when working on the battery banks (swapping batteries, adding a circuit, etc…) to ensure you don’t have a mishap, like an accidental short or something.


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[ftornabe]

This is great information. Thank you all. This website is such a great tool.

 

[Dave2016R29]

Some good information on this chain. I sometimes have a problem with my thruster battery in a 29S, and I am not clear how it gets charged. Based on this chain, the solar panel never goes to the thruster battery. I assume that when the engine is running that it eventually gets to the thruster battery once the engine and house banks are charged? Is this correct? If the thruster battery voltage is below the minimum, will setting the parallel switch on reset the thruster battery so it will charge? My thruster battery is also the start battery for the generator (it currently won't start due to low voltage). Does the generator charge the thruster battery?

Thanks for any input

 

[Brian 27 OB]

This thread reminded me I want to change out the 6 gallon water heater for a 4 gallon. Even two showers back to back it’s hard to run out of water with 6 gallons superheated.