12V Bow Thruster Battery Replacement

[angus99]

I would cover the terminals in case you drop a wrench you don’t short out the batteries.

Thanks; thought I covered that:

“Also, still need terminal and fuse covers.”

 

[Comodave]

Ask me what happens when the wrench gets across the battery terminals. I have covers on all my battery but I was working on the thruster batteries so I had the covers peeled back. Huge sparks and half of the face of my adjustable wrench gone. Lots of dust around the terminals was what was left of the adjustable wrench face.

 

[angus99]

Depends on thruster and boat.

Ours, for example (Vetus BOW16024D, aka 250mm tunnel and 160 kg thrust 24VDC) specifies a minimum of 950 CCA and max of 1900 CCA. (Max may just mean beyond that, there's no additional benefit.)

For ours, Vetus suggests a minimum of two 125 Ah batteries (from among Vetus products, but maybe similar to G31s) or two 4Ds in series for the lower rating... and 4x in series/parallel for the higher rating.

Looks like Vetus recommends two 170 Ah batteries (from among their products) in series for a BOWB150. Don't see a CCA table to cross-reference from that... but maybe that'd be like two 4Ds. Or the Odyssey Extreme G31s, spec'd for serious CCAs.

-Chris

I talked to the Vetus engineer behind the BOWB line and to the manager at Florida Bow Thrusters. FBT recommends a pair of ODX AGM31s for this model thruster routinely. And yes, it’s to get 24 V as well as the amps required to get maximum thrust out of the unit. The VETUS engineer said, despite what the manual advised, that CCAs rule and AH should not be the determining factor.

 

[angus99]

Ask me what happens when the wrench gets across the battery terminals. I have covers on all my battery but I was working on the thruster batteries so I had the covers peeled back. Huge sparks and half of the face of my adjustable wrench gone. Lots of dust around the terminals was what was left of the adjustable wrench face.

I don’t need to ask. Been there, done that and I noted that covers were still needed in my original post. The photo you see was taken as the install was wrapping up. I appreciate your zeal, but I’ve got this covered (literally now).

 

[Comodave]

I guess I missed that in the original post. Glad you are up to speed.

 

[RickyD]

So I went with the recommendation of the ODX-AGM31 ... wired in parallel to juice up the CCAs. Quick question ... my main run to the thruster is with 3/0. No one around here carries 3/0 ... only 2/0 or 4/0. Thought 2/0 would probably be fine for a jumper. My resting voltage on shore power appears to be around 13.35 - 13.4 V. Curious what other ODX users see and what kind of drop and recovery I can expect on a ~3 sec burst.

Also, should I just beef up the jumper to 4/0? Thinking that might be better but would appreciate opinions. Thx.

A 3 second burst won’t affect the battery at all I believe. I ran mine as a test for several minutes at 75% power until the motor overheated and the ODXs came back to 12.5 after a short rest. No charger attached.

 

[Bacchus]

What do you need such battery power for? A single group 27 battery should do it for you.



pete

Pete
You must not have any experience thrusters.
Mine are fused at 500 A each. With V drop at activation, I can't imagine how long a GP27 would last. Losing a thruster when you really need/want it isvworse than not having one.

 

[ranger58sb]

The VETUS engineer said, despite what the manual advised, that CCAs rule and AH should not be the determining factor.

Yep, not surprised. And from what I can tell, the CCA and Ah refs were apparently to help identify specific batteries from the Vetus line-up.

I was mainly trying to hep Pete understand why a single G27 wasn't really viable in many cases.

-Chris

 

[mvweebles]

LFP automotive start batteries are starting to enter the market. They boast modest AH rating but incredibly high discharge (CCA equiv) ratings. This G27 shows 60AH capacity but 1800 'cranking amps' in discharge. If my back-of-napkin math is correct, should be able to run a 400A thruster for close to 10-mins.

https://antigravitybatteries.com/products/starter-batteries/automotive/ag-27-rs/

While expensive, it's small, lightweight, and sealed. This makes it much easier to place very close to the thruster.

For electric-start OBs, I understand some folks have tinkered with the tiny motorcycle version of these LFP start batteries - placing them under the cowling of the OB to make them totally hidden.

Peter

 

[JohnO]

Quick update to close this out ... took Ranger's advice and got twin Odyssey Extreme ODX-AGM31s. Fortunately the cable runs worked out with the parallel. The only extra work I had to do was adding jumpers for parallel setup and finding and configuring the battery box. Found a dual G31 battery box. Mounted the box in the old spot, then strategically added a few velcro pads in the bottom and cut some slots in the side for additional straps for each battery to hold them in place. Just need to clean up the wiring a bit and probably shorten the jumpers so they don't lay on top of each other just to be safe. Haven't taken the boat out to try out the new batts, but excited to see how it works ... thanks for the recommendations!

 

[Comodave]

Also maybe add some tie downs along the cable runs. ABYC specs every 18”. The photos aren’t clear enough but are those wing nuts on the battery terminals? If so go with nyloc nuts instead.

 

[JohnO]

Yeah - need to get the wiring tied down. Didn't have what I needed. Good call on the nyloc. I actually have locking washers on there (came with the battery), but a swap for nyloc is easy enough. Thanks for the advice.

 

[Bacchus]

Washers under terminals aren't a best practice. Getter w/o them and terminal in contact w the clean post base.

 

[Comodave]

If the washers are under the nuts but on top of the cable connectors then they are ok. Under the connectors and between the terminals then not ok, adds a lot of resistance which equals heat and voltage drop.

 

[JohnO]

Thanks guys - the locking washers are on top next to the nut ... all of the ring terminals are underneath.

 

[Comodave]

Good, just replace the wing nuts with nyloc and you will be good. While the connections are clean and corrosion free I like to spray the terminals with Boeshield to help keep them that way.

 

[JohnO]

Will do - Thx!

 

[angus99]

Looks very nice! I’m guessing you mean that the batts are held in place by straps screwed or otherwise secured to some solid surface—not to a battery box held in place with Velcro? In any case, the battery box isn’t necessary for an AGM installation—at least as per the last ABYC guidance I read.