Bow Thruster Batteries

[km1125]

OK, so now here's the counter-argument to just adding bigger batteries....

Personally, I think it's insane to have even a single group 31 battery for something like a thruster or a winch. Having two is worse. Why? Because you're installing a lot of CAPACITY when you really need POWER.

You really should understand what your thruster (and winch) needs and how you use them. You should only need to use either a couple MINUTES at a time, at the most. With a thruster, you should be using short bursts of power, typically only 3 to 5 seconds at a time. With a winch, the most you use that is retracting a chain in deeper anchorage and that still should be limited to a couple minutes at most. In fact, a lot of these devices are THERMALLY limited (meaning they'll overheat) if you use them more than several minutes within the hour.

It will vary with the size of devices, but a typically thruster might draw 250A when running. That comes out to only about 0.35 amp-hours of capacity for each 5 second application. If you used the thruster TEN times during a docking maneuver (which should be excessive) and used it for FIVE seconds each time, that only adds up to 3.5 amp-hours.

Again, individual devices will vary, but a larger anchor winch could use 150A when retrieving. Using that for a FULL two minutes (which could be 150-300 feet of chain) would total up to about 5amp-hours.

Putting in two (or even one) Group 31 batteries for these applications is "crazy" IMO. It's overkill and you're adding a lot of weight, taking up a lot of space and using up a lot of $$ for a lot of capacity you will never use. And that's especially true if that/those Group 31's are deep cycle or dual purpose. You would be better served with one (or even two) group 24 or group 27 STARTING batteries, as those are intended for high-current, short duration loads - just like a thruster or winch.

[Tireless]

Km1125, I am starting to research where I would get a replacement toggle switch, QL part #41100743. A buddy of mine has told me he believes that you can replace the switch, without replacing the entire toggle.

He may have found the manufacturer that makes the switch. I need to go to the boat and pull it to get the part number for the switch.

The dedicated battery I have on the bow thruster is a Crown, Fleet Manager 31S-1100, with 1375 CA and 1100 CCA, however, based on what I am hearing I may treat myself to a second one to ensure it works at peak performance.

Also need to follow up on comment by Km1125 about what maybe too much. Have to take a meter to the thruster and flick the switch to see what impact thruster has on the battery.

Greg

[Midnightsun]

Not a big difference in size between a 27 and a 31 in terms of size, I believe it is 1". My engines require a minimum of 1000cca which is not available in a group 27. Group 31 batteries in a starting format are what is required for windlass and thruster applications as they can handle large amounts of current draw unlike hybrid or deep cycle.

I purchased my last set through Cummins which were only $119 cdn so pretty cheap. They have gone up slightly in 2 years but not much considering everything else is skyrocketing and are not surprisingly out of stock now. I must assume these batteries are designed to start diesels being they are the Cummins brand. https://shop.cummins.com/CSSNAStore/s/p ... ng-battery

I did not design this or tweak this, Carver set this up at the factory however I believe they used the Crown brand in a group 31 starting format.

[Viper]

For engine CPUs, we're not so concerned with capacity used as much as how much the voltage drops during high loads, even in short bursts. Total amp hour usage can be low yet still cause a brownout. One would think the alternators would mitigate this problem but instead we're finding more and more that we're having to isolate newer engine banks because of CPU brownouts. Isolating banks for nav systems/electronics is becoming more popular for the same reason, they don't like brownouts either. Nothing worse than your electronics suddenly going dark and having to wait for everything to power up again, resetting courses, acquiring signals, etc. In a world where engine CPUs are becoming more dominant and control systems are high tech fly by wire CAN BUS networks, we're finding more and more that voltage drops from high loads kicking in often cause gremlins that are usually non-existent with isolated system power sources.