Bow Thruster Batteries

Deep cycle or starting? I'm at West Marine. Thinking ahead , not Can TF come up with a consensus in time? I think so! Let me know what type you have, thanks.

AGM- group 31 is what I have.

Starting but there are a lot of combo batteries like agms that seem to go both ways. Lifeline is what we use and have had very good luck

The Manual says I need 760 CCA or 988 MCA. That means a starting group 24 1000 or starting group 27 1050 or go to a 4d dual purpose. That seems like a lot! I have a Side Power SE 100

If you get into docking situations where you use your thruster for longer periods, you will take the battery down into deeper cycles and the need for a deep cycle battery. There really is no dual purpose battery.
If you have room, an 8dd gives much longer service than any car sized battery. Both in how much power can be used and how many years they last. The 8ds that came with this boat (8dds and 8dcs) were 25 years old when replaced.

I think a bow thruster battery is closer to a starting battery than a house battery. A bow thruster will draw a couple of hundred amps whereas starting a good size diesel will require double that. A house battery typically uses 10 amps or less on average.


But in any case, a bow thruster mounted at the bow is a good candidate for an AGM, and for AGMs there is no difference between deep cycle and starting.


David

I have a 8D, to a Lewmar thruster, it has never cut out which is nice for those tricky docking times.

Thinking about the group 31 agm. I forgot to say I have a 24v thruster. Does anyone know how two batteries effects cca/Mca? Do both batteries have to have the correct power or does it double like the voltage?

Placing two similar batteries in series shouldn't have much effect on the CCA ... But because you doubled the voltage you doubled the amount of power to the thruster... I did something similar used 2 12v batts in series and charged them with a 24 volt charger plugged into an outlet powered through the inverter...

djmarchand said:

But in any case, a bow thruster mounted at the bow is a good candidate for an AGM, and for AGMs there is no difference between deep cycle and starting.

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I have a 24v 10hp SidePower bow thruster and it is powered by 4 Full River 6v batteries. (AGMs) So far I have had no issues with these batteries but I have only had them about 7 months.

I used two standard 8Ds for my 24v thruster on my Hatteras 56MY (that's the way it came to me) . I understand that the Florida Bow Thruster now typically uses two Group 31 AGMs like the Sears Platinum for that size. I had one of those for my generator starter, nice battery with 1000CCA if I recall correctly.

I would vote for a start batt , as it can be used elsewhere in an emergency.

The thin plates will make good amperage and the resulting gassing will drop the voltage before the batt is deep cycled , which it can not handle.

The other good news is most DC thrusters have short only operating cycles permitted.

The gassing and voltage drop of the start batts may save the thruster motor.

Be sure to reed "Da Book", on how long you can hold the button down.

I have 2 Optima spiral wound "Starting" batteries in series for my bow thruster. The spiral wound cells are supposed to handle vibration and shock better. Been very happy with mine. Available online from Summit Racing for a great price with free shipping.




Ted

Our Vetus 12volt thruster is wired to the 4D engine start battery. Only use it with the engine running, so not much chance of draining it down. Pretty heavy cable run from the engine room to the bow, but it works great.

caltexflanc said:

I understand that the Florida Bow Thruster now typically uses two Group 31 AGMs like the Sears Platinum for that size.

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One company (might be them, too) used a pair of Odyssey PC-2150 AGMs (Group 31, and same as Platinum Plus, private-branded for Sears) for their installations. Huge CCAs, relative to many other G31s.


AGNs mounted very near the thruster, so reduced off-gassing in living quarters was one of their selling points, too.

I haven't pulled the trigger yet, but whenever it bubbles to the top of my wallet I expect I'd go that way...

-Chris

Thanks Guys. I think I will go with 2 Gr 31 AGMs. I am looking into a Sterling battery to battery charger. It's 12-24v. The engine charges at sea, and the 12 volt charger from the house/starter bank charges ar dock.

In talking with the pros, they talked me into group 31 AGMs for the internal cabin safety and off the gassing issue alone. My first set made it about 5 years, less life IMHO than a well maintained LA but again, off gas minimized.

sunchaser said:

In talking with the pros, they talked me into group 31 AGMs for the internal cabin safety and off the gassing issue alone. My first set made it about 5 years, less life IMHO than a well maintained LA but again, off gas minimized.

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While generally I agree about the "less life"....I think you may be comparing apples to oranges as far as application goes. IOW, LA batteries in the same application would have lasted less time than in a less harsh application....like a house bank. Bow thruster service is pretty severe/harsh service. Apples to apples, I think the AGMs would outperform the LAs in this application.

Also, I do own and operate 5 Sears Platinum Marine GRP31 AGM Batteries. They are indeed the same batteries as the Odyssey 2150. I went looking on line for the Sears version and they come up "Unavailable". Something tells me the agreement between Sears and Odyssey may have expired. I paid $260 per for mine. I think Odyssey sells them for $390???? I do believe they represented a good value at $260. Would I pay $390 a piece for them???? I don't think so. As I type this I googled real quick and found them for $310. Still pretty stiff but I think I might go that far. I have had them for 3 years now and not even a twitch or flicker so I expect them to last a good while....we shall see.

To answer OP's question....AGM all the way. 2 GRP31s in series....and preferably a hearty GRP31 like the Odyssey. When one GRP31 weighs 50lbs and another weighs 80lbs, I don't know what it means(more lead I assume) but I would think it is a better battery. That is what those Odysseys weigh. Crazy heavy for a GRP31....but I imagine it means it's a better battery.

As an aside....My previous boat, Mainship Pilot 30, had 2 GRP 27s for house...starting...windlass...AND bow thruster!!!!!! Basically those 2 GRP27s for EVERYTHING!!!!! Let's just say they don't last that long when they are punished that severely. Nor does a bow thruster burst remain strong after the first 5 seconds...it starts to fade. If you need more than 5 seconds of thruster, generally speaking, you aren't doing it right!

I minimize weight since my boat is capable of planing. So thruster gets a starting type grp 24, flooded. I get about 4yrs out of it before it starts getting lame. New, 11v when running. If it gets under 10v, man you can tell the difference.

I think it is rated at 70Ah, so to go 50% that would be 35Ah, or 2100 amp minutes. At 300A, that gives you 7minutes to take it down to 50%, which sounds about right.

Only time I had an issue is when a bud was running my boat in a holiday parade. I was on the FB enjoying company and beverages, he was down below enjoying steering with the thruster. Finally he complained to me that the thruster quit. Dope slap time...