Battery isolation?

Nov 21, 2019
6
Hunter 49 49 Clearwater fl
We are having problems with our batteries. Last night we drained all the batteries and couldn't start the boat at anchor. We don't understand how to isolate the start battery so it does not get drained. Here is the panel. Please help.
20191121_090531.jpg
 

capta

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Jun 4, 2009
4,766
Pearson 530 Admiralty Bay, Bequia SVG
It doesn't appear as though you have a start battery you can isolate. You would need another battery and a one/two/both/off battery switch to isolate that start battery from your house battery (a single battery?), which appears to be labeled as "start/house" battery. And then you are going to need a charging source for the start battery, so you have a bit of planning to do to get the system you want.
 
May 17, 2004
5,032
Beneteau Oceanis 37 Havre de Grace
+1 to what Capta said. You may also need to consider why the bank went dead overnight. Were the loads that high, or is the existing back nearing its end of life with reduced capacity.
 
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Apr 8, 2011
768
Hunter 40 Deale, MD
Agree with capta - you have some planning to do to resolve this problem. The short-term solution could be physically separating house and starting banks and rewiring to a new switch which allows you to select one or the other (or even combine them, though why?). You'll also need something to ensure BOTH banks get charged. Doing so will leave you with enough juice to start in the morning, but you'll kill your house batteries in very short order draining them down so low at night - all your batteries may already be damaged beyond recovery.

Lots of threads on here about how to think through designing a right-sized battery system. Starting with doing an energy budget. There's also a valid line of thought (Mainesail) that you don't really need a separate starting battery if you have the right sized house battery bank, and a system that protects you from inadvertently discharging your batteries to damaging levels that will not support an engine start. I've adopted that approach.
 
Oct 26, 2008
6,045
Catalina 320 Barnegat, NJ
That picture shows a Blue Seas Dual Circuit 5510E switch. It has 4 posts on the back side so it is designed to isolate the house and start batteries. When it is "ON" it switches both banks on but they should be isolated. The difference between this and the DCP is that it doesn't have the capability to combine the banks.

I would take a look at the posts. Is this boat new to you or have you owned it for a long time? If new to you, I suppose it is feasible that a P.O. may have jumped the posts on the back side so that the banks are permanently combined. That would be really dumb and not likely, but who knows until you look?

Other than that, perhaps both battery banks are on just one side. There shouldn't be a reason for both banks to drain simultaneously unless they are linked somehow. I would start at the back of the switch and trace from there.
 
May 24, 2004
7,129
CC 30 South Florida
You have a single pole switch to connect or disconnect the battery bank. I would consider it normal that you only have a single battery bank to perform double duty in starting the engine as well as powering House fixtures. A battery bank may be composed of a single battery or multiple batteries acting in unison. The same way a single cell can bring down a battery a single bad battery could bring down a multi battery bank. Did you run a large load overnight while you were at anchor? How large in Ah is your bank? This sort of thing happens, and that is why you need to build redundancy into your power storage system. A simple way to insure redundancy for engine starting is to carry a fully charged portable power pack like those used for Automobiles. A more refined option would be to have a dedicated and isolated starting battery.
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
It is difficult to help without seeing how the system is wired. In order to be really helpful, you'll need to trace the main battery cables and draw a schematic.

As for the batteries discharging over night, the first question is how old are the batteries? Followed by how are they charged? How do you monitor the charging? And what high loads do you have running? What kind of batteries do you have? Flooded Lead Acid? AGM?

Refrigeration and AC can draw a lot of current and kill batteries quickly, especially old batteries.
 
Oct 26, 2008
6,045
Catalina 320 Barnegat, NJ
You have a single pole switch to connect or disconnect the battery bank. I would consider it normal that you only have a single battery bank to perform double duty in starting the engine as well as powering House fixtures. A battery bank may be composed of a single battery or multiple batteries acting in unison. The same way a single cell can bring down a battery a single bad battery could bring down a multi battery bank. Did you run a large load overnight while you were at anchor? How large in Ah is your bank? This sort of thing happens, and that is why you need to build redundancy into your power storage system. A simple way to insure redundancy for engine starting is to carry a fully charged portable power pack like those used for Automobiles. A more refined option would be to have a dedicated and isolated starting battery.
Take a closer look … the switch IS 2 poles and designed for isolation. That said, it may not be used that way. Nick should investigate the back side of the switch.

BTW, the switch does appear to be too simplistic for the application. I'm wondering if there are additional switches behind the scene to give the operator the ability to use one bank to temporarily provide service when the other bank fails. It appears that the single 2-pole switch does not provide any redundancy when needed.
 
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Nov 21, 2019
6
Hunter 49 49 Clearwater fl
Take a closer look … the switch IS 2 poles and designed for isolation. That said, it may not be used that way. Nick should investigate the back side of the switch.

BTW, the switch does appear to be too simplistic for the application. I'm wondering if there are additional switches behind the scene to give the operator the ability to use one bank to temporarily provide service when the other bank fails. It appears that the single 2-pole switch does not provide any redundancy when needed.
There is switch to the top right ofof the red battery switch. If open it appears to not drain the starter battery. Also does not charge starter battery from the inverter. I am going to start the motor to see if the alternator changes the starter battery when the motor runs.
I think if I open that switch/breaker while at anchor my starter battery will now drain

Three new life line AGM batteries are on there way from Miami. Test showed our deep cell batteries were toasted. The batteries are over two years old and when checked last week they were very dry.
 
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Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
Three new life line AGM batteries are on there way from Miami. Test showed our deep cell batteries were toasted. The batteries are over two years old and when checked last week they were very dry.
This is a tell tale sign. Dry batteries are dead batteries.

Get to know your charging system well. The good news about AGM batteries is they have a higher charge acceptance rate. The bad news is they don't tolerate a Partial State of Charge (PSOC) very well and if not fully recharged correctly and quickly, they die an early expensive death.
 
Oct 26, 2008
6,045
Catalina 320 Barnegat, NJ
I'm certainly not an expert in these systems but I would try to learn a lot more about your particular system before going down the wrong road with new AGM batteries.

I see the red-light indicator for your "parallel charge circuit" and I see what looks like a red button on a rocker of some kind. I'm not familiar with that at all. I assume what you are saying is that when it is "on" you can charge both batteries from a charger/inverter combo. So this switch appears to be intended to combine the banks just for charging. If you leave it on, the banks are then combined for discharge as well. This is not good at all.

You also seem to want to know that if you leave the switch off, will the start battery charge from the alternator. I can also tell you that you don't want to rely on the alternator for charging the start battery. It may never receive a full charge and you may lead that battery down an early death due to chronic undercharging.

I would think seriously about re-vamping your charging system with a dedicated modern marine charger that charges both battery banks via ACR (auto charge relay). I'm not a fan of inverters and I would probably move away from that charger/inverter combo. I suppose many folks in larger boats like yours are used to having an inverter. I'd probably want it to be a separate unit from the charger. From your description, I'm not even sure you have a charger / inverter combo, but I'm assuming that is what you have based on your description of charging the battery from the inverter. :what::what:

I'd also think about re-vamping your switch. I like Dual Circuit Plus, but I have also added a separate switch for each battery bank (normally always on and hidden in a compartment) so that I can have isolation when it may be necessary to run house and start on just one bank.
 
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Nov 21, 2019
6
Hunter 49 49 Clearwater fl
This is a tell tale sign. Dry batteries are dead batteries.

Get to know your charging system well. The good news about AGM batteries is they have a higher charge acceptance rate. The bad news is they don't tolerate a Partial State of Charge (PSOC) very well and if not fully recharged correctly and quickly, they die an early expensive death.
Thanks for the info. We will watch that.
 
Jan 4, 2010
1,037
Farr 30 San Francisco
What Scott said. You should have 4 wires going to that switch
House battery + and Starter battery + are the inputs and House loads and Starter as the outputs.

This should totally isolate the starter battery from the house.

Now the only question given one alternator is how to charge?

The best answer it seems today is put the alternator to charge the house battery (it is much more heavily used) and then place a ACR (automatic charge relay) between the two batteries. This relay connects the two batteries if the voltage on one of them is over 13.5V and the voltage on the other isn't too low. 13.5V indicates
 
May 24, 2004
7,129
CC 30 South Florida
Take a closer look … the switch IS 2 poles and designed for isolation. That said, it may not be used that way. Nick should investigate the back side of the switch.
I stand corrected about the number of poles and capabilities and would need to defer to how it is wired as far as any further comments.