Balmar Duo Charge blown fuse

Dave: if you don’t have a load tester, you could do some tests to determine the amps (clamp meter), and volts (at the terminals). It’s worth recording these data for later comparisons. The batteries should probably be above 10 volts under load.

Jim

So I have connected the BlueSeas ML-ACR (it had been used for my engine start battery in the past). Fortunately, I happened to have a couple battery cables of an appropriate size to make work. Not super happy with the way the cables are arrayed but it will do for now.

Currently the banks are charging. After I combined the banks, the combined voltage dropped to 12.5v. After charging for about 45 minutes, it is up to 14.2v.

Hopefully the thruster bank charges up well.

Once fully charged you should perhaps consider priceeding with an Equalize charge, as its been a while since you had all batteries in that state.

Aquabelle said:

Once fully charged you should perhaps consider priceeding with an Equalize charge, as its been a while since you had all batteries in that state.

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Yeah, I was thinking about the same thing.

Using a 40A fuse sounds like a good way to prevent nuisance blowing of the fuse. But when the Duo gets into this overload mode and is running only briefly then shutting down, over and over again, I wonder if your bank will ever get recharged? If nothing else, it will take a very long time. So in some ways a blown fuse at least alerts you to the situation.


I think given a clean sheet of paper, a VSR or DC-DC charger is the way to go. I think the Duo is fundamentally flawed for it's intended purpose, since once you get into this overload situation, there appears to be no way out. If instead of shutting off when current exceeds 30A, the Duo limited current to a sustainable level like a charger does, it would be a fantastic device.

twistedtree said:

Using a 40A fuse sounds like a good way to prevent nuisance blowing of the fuse. But when the Duo gets into this overload mode and is running only briefly then shutting down, over and over again, I wonder if your bank will ever get recharged? If nothing else, it will take a very long time. So in some ways a blown fuse at least alerts you to the situation.


I think given a clean sheet of paper, a VSR or DC-DC charger is the way to go. I think the Duo is fundamentally flawed for it's intended purpose, since once you get into this overload situation, there appears to be no way out. If instead of shutting off when current exceeds 30A, the Duo limited current to a sustainable level like a charger does, it would be a fantastic device.

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I agree with everything you wrote. While I think the Duo Charge is great for a lot of applications, and has worked well on this boat for years, I think there is the potential for problems when it is used on a large battery bank with high current loads such as thrusters.

A much better solution would be the Sterling DC-DC chargers that CMS linked to. If I decide to ultimately return to a DC-DC charger, I will likely buy one from him.

The Duo Charge is ideal for smaller batteries like a start battery or maybe a windlass where the amp draw isn’t as high. I will warn everyone however, that it is NOT OK for a Cummins electronic start battery. The Duo Charge creates electrical interference that confuses the crap out of the Cummins. In that application, if the charge profiles are similar, the simple (and inexpensive) Xantrex Echo-Charger works well.

OK, after charging overnight with the ACR connecting both the house and thruster banks, it was at float this afternoon. After disconnecting the charger for about 15 minutes the batteries showed 13.2v. This is too high for the ACR to disconnect so I started the inverter and ran my oil pan heater, two fans, and two dehumidifiers (what is normally running while at the dock). It only took about a minute and I heard the CLICK of the ACR disengaging.

I then shut the inverter off. At that point the house bank was at 12.87v and the thruster banks was at 12.82v. I then ran the bow and stern thrusters for a bit, trying to simulate the amount of time they would be on in a really bad docking situation. Running both at once takes a huge amp draw.

Right after running the thrusters the thruster bank was 12.65. After 20 minutes of rest the thruster bank is 12.74.

I’m too ignorant to really know what all that means, but I’m guessing that the two Lifeline batteries that make up my thruster bank are still OK. It also means that I connected the ACR properly (I know it is simple, but I can screw up most anything).

I think now I’ll run an equalization cycle on the batteries.

I'm coming in late on this thread, but here's my 2 cents based on similar experience as yours: DO NOT run the thruster/windlass off the house bank. DO NOT charge the battery using trickle chargers (Balmar Duo, Xantrex Echo Charger). Instead, install a dedicated charger (I chose IOTA 45 amp), add an easy to see digital volt meter and a separate On/Off battery switch. The charger will do it's job whenever you run the generator or connect to shore power. If you decide to go with the ACR, then use the charger as backup. But Do Not run those high amp draw motors off the house bank--your nav instruments and other sensitive 12V devices will thank you!

nwboater said:

I'm coming in late on this thread, but here's my 2 cents based on similar experience as yours: DO NOT run the thruster/windlass off the house bank. DO NOT charge the battery using trickle chargers (Balmar Duo, Xantrex Echo Charger). Instead, install a dedicated charger (I chose IOTA 45 amp), add an easy to see digital volt meter and a separate On/Off battery switch. The charger will do it's job whenever you run the generator or connect to shore power. If you decide to go with the ACR, then use the charger as backup. But Do Not run those high amp draw motors off the house bank--your nav instruments and other sensitive 12V devices will thank you!

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For my application, I don't think a dedicated charger makes a lot of sense.



The Duo Charge has worked well for years and after looking at the fuses this weekend, It appears to me that both had poor contacts which could have caused heat to build up and the fuse failing. The fuse didn't look like it blew due to overcurrent, but simply heat. Having said that, I don't think the Duo Charge is the best current option for a DC-DC charger for a large bank with high amp draw.


The best option would likely be the Sterling DC-DC charger, but the ACR will likely work out quite well for now.


Your point about voltage sensitive instruments is well taken and a good reason to maybe avoid running the thrusters off the house bank.

FWIW, Mastervolt makes a line of DC to DC chargers too. I can’t say if they are better or worse than Sterling, but I used two Mastervolt for many years with no issues.

Update

I have been running the boat with an ACR between the house and thruster bank. However, I’ve had issues with voltage drops affecting the nav instruments when the thrusters are used.

So today and reconnected the Balmar Duo-Charge. Someone mentioned that the melted fuse holder could be related to simply a poor connection in the fuse holder. Certainly could be as the fuse has been there for almost a decade.

The other thing that I noticed before but never though about, was that the Duo-charge wasn’t installed according to Balmar’s instrucitons. So I ran a new 10AWG wire from the Duo-Charge to the battery. It is right about the 8’ length that Balmar recommends. Anyway, I’ll keep and eye on it and see if it performs well (as it had for almost a decade before).

Yeah; its good to take a voltage reading every few years on the high current users, right at the load. This will show any deficits in connections and even the battery(s) themselves.
My garmin chartplotter is my early warning canary when too much house V drop occurs.

Dave: have you checked the voltage drop at the thruster batteries with all charging sources off, including the ACR? If below 10 VDC, I suspect the batteries may be near end of life, particularly if the Duocharge worked previously.

In my situation, the issue I’m finding with the Duocharge is, the voltage drop between the Duocharge to the thruster bank is excessive, as the POs only used 10 gauge wire and the run is far too long. This is something I need to correct.

Jim

JDCAVE said:

Dave: have you checked the voltage drop at the thruster batteries with all charging sources off, including the ACR? If below 10 VDC, I suspect the batteries may be near end of life, particularly if the Duocharge worked previously.

In my situation, the issue I’m finding with the Duocharge is, the voltage drop between the Duocharge to the thruster bank is excessive, as the POs only used 10 gauge wire and the run is far too long. This is something I need to correct.

Jim

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If there is a fault with the thruster battery that could cause excessive current demand and the melting of the duocharge fuse.

JDCAVE said:

Dave: have you checked the voltage drop at the thruster batteries with all charging sources off, including the ACR? If below 10 VDC, I suspect the batteries may be near end of life, particularly if the Duocharge worked previously.

In my situation, the issue I’m finding with the Duocharge is, the voltage drop between the Duocharge to the thruster bank is excessive, as the POs only used 10 gauge wire and the run is far too long. This is something I need to correct.

Jim

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After the batteries initially had been discharged very deeply (when I found out that they were no longer being charged), I connected them to the ACR and got them fully charged. I then disconnected the thruster batteries, used the thrusters a tiny bit, and let the batteries rest for over a day. The batteries still showed 12.7v. So I think the batteries themselves are OK.

I’m not as sanguine about all of the connections as I haven’t had a chance to check them all yet. I will however.

I agree that the batteries are likely at the end of their life. I am unsure of their age, but they are likely at least 6 years old and could be as much as 8 years old. I have only abused them once, but it was bad as they ended up reading only about 10.5v if I recall. Still, I will see how they work with the Duo-Charge setup again.

As has been noted, Balmar wants the charger connected to the battery with a 10 gauge wire that is at least 8’ long. I don’t understand the reasons. Instead, this one was connects to a positive bus to the thruster bank so was connected with a 4/0 cable. When I reconnected it, I ran a 10 gauge wire connected directly to the battery. Not sure if that will make any difference. I will also use a 40amp fuse as CMS recommended instead of the 30amp.

Actually, Dave, I meant “What is the voltage at the batteries with the thruster engaged and all charging sources off?” If it drops below 10, it could be causing all of those problems with your nav instruments, if they too sense that low voltage. This test is one way to determine battery health in a relative sense. Do the test again when you have new batteries and you will probably find considerably higher voltages with the thruster engaged.

Dave if you are using an ACR there should be a terminal that will open the ACR contacts. That terminal just gets connected to the thruster solenoid coil so when the thruster is energized the ACR is open. This will prevent the voltage drop you are seeing on the electronics assuming that the electronics are on the house bank.

JDCAVE said:

Actually, Dave, I meant “What is the voltage at the batteries with the thruster engaged and all charging sources off?” If it drops below 10, it could be causing all of those problems with your nav instruments, if they too sense that low voltage. This test is one way to determine battery health in a relative sense. Do the test again when you have new batteries and you will probably find considerably higher voltages with the thruster engaged.

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Ah, thanks. That makes so much sense!

I’ll try and do that test the next time I’m down at the boat with a helper.

Ka_sea_ta said:

Dave if you are using an ACR there should be a terminal that will open the ACR contacts. That terminal just gets connected to the thruster solenoid coil so when the thruster is energized the ACR is open. This will prevent the voltage drop you are seeing on the electronics assuming that the electronics are on the house bank.

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I believe that it will provide a 3-5 minute lockout. I’ll have to look at my own setup. That wouldn’t be long enough if I connected it to the solenoid that energizes the thrusters. However, I’ll have to look to see how my thrusters at controlled at the motor. I imagine there has to be a solenoid (or two) at each thruster.

If you go the Blue Sea ACR route, they provide an Engine Start tab that, when connected to the engine start switch or, in your case, the bow thruster switch, will disconnect the ACR immediately when voltage is sensed at the ES tab.