Bow thruster turning off chart plotter and sounds weak

Agree with BlueYonder, load test on the bats would tell you for sure if they need to be replaced which I suspect is the problem. Still concerned though that you may be exceeding the 30 amp cutoff that would limit charging on the new bats. Short term exceeding will not be an issue but if you are running that way for along time then that would eventually shorten the life of the new bats. Given that these have lasted 7 years I expect that to not be the issue but just to be safe it would be worth checking it out.

cardude01 said:

Thruster and plotter hooked to house batteries.

So when I use the thruster should I measure the amp draw at the house bank? How do I do that?

Panel says pulling only 2 amps underway. When I hit the thruster it didn't change, so that's not accurate.

Sorry for all the questions, very new at this obviously!

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I didn't read everything, but a couple thoughts:
1) In all probability, the panel ammeter doesn't read the thruster draw -- its a lot of draw;
2) The chart plotter is shutting off because its voltage is too low. You should put a volt meter on the batteries while the thruster is activated. If the voltage before is anywhere near 13 (or at least 12.8), and if you have a big voltage drop (say to under 11), probably bad batteries, but conceivably the thruster is "shorted" and consuming way more than it should. But if that were the case, I would think the circuit breaker would break. I can't think of any other explanation, unless your thruster and chart plotter are on the same circuit, which they should not be.
3) You may have charging circuit deficiencies that are only tangentially related to the thruster problem, especially if the battery voltage is near 13 (see above) without the thruster and under 11 when the thruster is engaged. The higher voltage indicates that the batteries are getting enough voltage to eventually reach full charge (at least without loads), but that the batteries don't have the capacity to withstand the draw of the thruster without dropping to unacceptable levels. If you charger or its parameters are not correct, that can cause premature battery failure (loss of capacity).

Remove the cables from the batteries after they are fully charged, then load check them or better check the specific gravity of each cell. One bad battery could be causing a problem, if the batteries are as old as you think I would replace with new. All the batteries in a bank should be the same, I wouldn't replace a single bad battery in a bank. I have a question on the 30 amp limit on the charge relay (or whatever it is) will this limit charging and draw to 30 amps?

Most electric bow thrusters either have their own battery(s) or are tied into the starter battery. Sometimes they share the windlass battery.

Was the thruster on the boat from the factory or is it a PO installation? It doesn't sound like a factory install. You need to get it off the house bank.

Donsan said:

Most electric bow thrusters either have their own battery(s) or are tied into the starter battery. Sometimes they share the windlass battery.

Was the thruster on the boat from the factory or is it a PO installation? It doesn't sound like a factory install. You need to get it off the house bank.

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Each thruster of ours has two 8D's and have a series parallel switch that allows them to run on 24v. But they're are tied in with the House bank. I don't find it odd. Our Camano's thruster was also tied into the house.

Sorry I didn't see this thread till now, Bill. I had the same problem twice before. A check on my two 8D house batteries showed a dead cell both times. Replacing the batteries fixed the problem, but I have a long run to the bow thruster and I gotta have big cable and terminals clean. Low batteries will cause all the symptoms you've got there and once you determine this with a decent meter, it's just money, and we all know you've got plenty of that. Best of luck tomorrow on the ICW north.

healhustler said:

Sorry I didn't see this thread till now, Bill. I had the same problem twice before. A check on my two 8D house batteries showed a dead cell both times. Replacing the batteries fixed the problem, but I have a long run to the bow thruster and I gotta have big cable and terminals clean. Low batteries will cause all the symptoms you've got there and once you determine this with a decent meter, it's just money, and we all know you've got plenty of that. Best of luck tomorrow on the ICW north.

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Wait. What's this "plenty of money" talk? I sell used cars for a living...

I'll try to load test the batteries tamale. Have had too much beer to do it tonight.

If I do replace them, should I go back with AGM? Is there a better (cheaper?) AGM out there than Lifeline?

We've had god luck with our Odyssey 12v Group 31 AGMs, and the Sears Platinum AGMs are made by Odyssey (last I heard). But yes, there are less expensive AGMs, by Deka and so forth. The "premium" brand may or may not be worth it, but I can say we're starting our 10th season on our oldest bank of Odysseys.

That said... it sounds to me like you have an opportunity to re-do your system. Your G27s aren't really true "deep cycle" batteries. You could replace those with two pairs of 6v deep cycle golf cart batteries (GC2s, see Lifeline's GPL-4CTs for example specs) and end up with 440 Ah in the house bank... and these would very likely fit in the same space where your 4x G27s live now. A bit more Ah than what you've got now, but also better designed for the job.

Next, move your thruster to it's own circuit, with it's own battery bank, ideally with decent cranking amps. The Odyssey G31s, for example, provide really high CCAs...

Then I'd probably get all your electronics onto the same battery circuit your engine uses. That way you'd have all that stuff active and charged by the engine alternator, no matter what's happening to your house or thruster banks. (I'm wondering if, when your thruster makes your plotter go south, if it also makes you depth sounder and VHF and so forth crap out, too?)

Realize not all of this could happen while you're traveling, nor would it all have to happen at once...

-Chris

caltexflanc said:

Thrusters really work best on their own properly sized bank which eliminates this sort of problem. A Group 27 sounds pretty small for a thruster, let alone powering the whole shebang, and a thruster can cause a big voltage drop when engaged. If you are out of gear, in neutral at the time, you can try revving the engine and seeing if that gives you more oomph, problem is one often times IS in gear and using the thruster at the same time.

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What he said !

This will be a recurring problem until you have a dedicated battery for the thruster. You can put a large diode in line to stop it drawing down your other batteries.

Your start bank should be for loads that have a high current draw for short durations. Thrusters, starters, windlass. Choose the batteries for high CCA. Electronics and such have low current demands but run for extended periods of time. The house bank is where they should be. If your system is set up properly, your engine alternator should be charging both banks when the motor is running. Your Balmar system should be charging both banks as required.

A dedicated battery for the thruster is the best option. The wiring could be more complicated and your charger would need to support three banks. Connecting the thrusters to the start bank is a good compromise.

A charging battery willusually show lower voltagethan a fully charged one. After some charging during which the voltage will gradually rise it should show about 14.5 V when on charge.

BlueYonder said:

Electronics and such have low current demands but run for extended periods of time. The house bank is where they should be.

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Yep, that's a good point, too.

Design issues aside, I only meant to suggest that "problems" are sometimes actually lightly disguised "opportunities."



-Chris

Or.....his batteries are just fine and he has a charging system where, once the batteries get below a certain state of discharge, the Balmar engine charging system can't get them charged back up again because it's calling for more than 30A of charge current and shutting down.

Load testing the batteries is good, and you might well find a bad cell or two.

And beefing up your battery system is probably a good idea too.

But if your charging system works the way it's been described, I think you will just end up right back where you are now. So I'd check real carefully to be sure the Balmar engine charging system isn't shutting down when your batteries are heavily discharged.

cardude01 said:

So maybe the batteries are charging, but just old and weak?

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That's my bet

cardude01 said:

So maybe the batteries are charging, but just old and weak?

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Or maybe the batteries are fine and not charging once drawn down below a certain level.

This is what you need to figure out. You can guess, then replace parts and see what happens. Or you can do some test and experiments to really diagnose the problem.

Isolating each battery, checking its voltage, and load testing is a great step to assess the batteries themselves.

But even if you find one or more bad batteries, I'd carefully check the engine charging system, especially with respect to the Duo Charge (I think that's what it's called) and what happens if it starts shutting down when more than 30A is called for. If that happens, how will your batteries ever get recharged? If nothing else you need to know how to detect if this is happening, and have a way to recover from it.