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Old 11-13-2018, 05:43 PM   #21
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Odyssey 31M-PC2150ST are dual purpose crank and deep cycle (104 ah)
Yes, a most excellent choice for this use case, and Lifeline and Northstar got the same TPPL tecnology from Enersys, who invented it.
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Old 11-13-2018, 06:47 PM   #22
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I'd get something that matched the thruster manufacturer's specs. A novel concept here. Had a 24v bow thruster on my old Hatteras, 2 flooded standard 8Ds were at the upper end of the specs and that;s what we used, charged by a dedicated charger, all courtesy of a PO. Life was good. Still is for that matter, sans big boat and accompanying thruster, but not as good.
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Old 11-13-2018, 08:34 PM   #23
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Then your bank is undersized, by definition. Likely not fully charged, maybe never fully charged.

Murderous conditions.

> My charge link runs through a 10ga cable and 15A breaker from house bank. It trips the breaker if I did not use the relay scheme.

Way too small to make a difference.

> And if you run your thruster enough to take batt down to 10% SOC, you are dogging that thing!!

Go back and look, 10% DoD means 90% SoC.

My point is such usage has nothing to do with Starter patterns, absolutely within deep cycling's definition, as your details make even more crystal clear.

Systems design is much better off defined by the worst case scenarios, ignoring the best-case ones.
Hmm. Responses below:

1. Batt volts at 10.5 under thruster load is not indicative of a problem. Batt is well charged, healthy and thruster performance is good. Could it be better with a bigger batt? Sure, a few more rpm. But I do not need it. And as a planing boat, I pay for increased weight.

2. Murderous conditions? Hyperbolic much?? The charge link is 10ga, amps limited to 15A, but it works absolutely fine with the relay that disconnects charge link with motor running. Breaker does NOT trip. A half hour after using thruster the thruster batt is right up there at the same voltage as house bank. In bulk mode it is 14.4v, after that 13.5v and charge amps basically zero. Battery is happy there.

3. My mistake about SoC vs. DoD. Just using gut feel math my thruster does not draw batt more than 10% of capacity on normal use. That does make a start type battery inappropriate. And batt life seen confirms this. Six years is not too bad.

4. I am fully aware of system design criteria, I have done it for a living for 30yrs as a mechanical engineer. On a planing boat you want to minimize weight (just as you would on an aircraft). If you designed everything to the worst case conditions, the boat would be a pig. Or the plane would not fly.
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Old 11-14-2018, 06:58 AM   #24
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Originally Posted by GGroves View Post
Current batteries were Sears AGM (no longer made). Saw FBT at the Annapolis Boat Show and they said they now use Odessy 31M-PC2150ST AGM batteries (x2) connected in series for 24 v.

The Odessey 31M-PC2150ST are dual purpose crank and deep cycle (104 ah).

The Sears Platinum Plus line of AGM batteries were OEM Odyssey PC-2150 (Group 31) and PC-1500 (Group 34) respectively.

The "ST" is about specific terminal type or configuration, I think. IIRC, Odyssey offers a few choices there...

I'd think the PC-2150s would seem to be a very good choice for a thruster (huge cranking amps, very good longevity), especially if the batteries are installed in living quarters.

-Chris
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Old 11-19-2018, 02:33 PM   #25
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I like the idea of a relay to cut out the charger when the thruster is running.

With a big enough relay (and with enough DPDT contacts), it would be possible to wire it so that when the thruster is not running, the batteries are connected in parallel and being charged by the 12v charger. Then when it's activated, the relay disconnects the charger and reconnects the batteries in series for 24v to power the motor.

That would work. Just have to draw out the wiring diagram!
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Old 11-19-2018, 05:33 PM   #26
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12 / 24 realy

I also have a 12 / 24 - Parallel / Series relay. Let me know if you need one, I have a couple spares.

They use them on Big Rigs & heavy duty equipment.

12-volt wiring of the two 12-Volt batteries in parallel for recharging & then when you hit the starter, relay flips, & they go to series wiring & you have 24-volts to run the starter or thruster.

No Electronics to fail.

Works great.

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Old 11-19-2018, 06:24 PM   #27
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I also have a 12 / 24 - Parallel / Series relay. Let me know if you need one, I have a couple spares.

They use them on Big Rigs & heavy duty equipment.

12-volt wiring of the two 12-Volt batteries in parallel for recharging & then when you hit the starter, relay flips, & they go to series wiring & you have 24-volts to run the starter or thruster.

No Electronics to fail.

Works great.

Alfa Mike
Done it this way since 1994. No problems.
I got my series parallel switch from a farm equipment place, $54.00 for a switch from a Russian Belarus tractor which starts on 24vdc but then everything else runs on 12vdc.
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Old 11-19-2018, 06:34 PM   #28
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Yep, 12/24v relays are common out there. Some marine diesels above 10 liter use these too. I think it would be relatively easy to wire in for a thruster. Might need some diodes to fire the coil from the p/s run signal.
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Old 11-19-2018, 07:35 PM   #29
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Here's a link to a 12/24 relay. Charges the batteries in parallel at 12v, then puts them in series for 24 v for heavy duty starters or bow thruster applications.

12/24 Volt DC 1500 amp Series Parallel Solenoid Relay.
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Old 11-20-2018, 06:28 AM   #30
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Realize OP is starting with a 24V thruster... and don't mean to hijack, but didn't get any comment in the other thread I started about thruster options.

I'm still in "decision" mode, wondering if there's any reason I should prefer a 24V thruster over a 12V version, assuming all other things being equal. I wrote:
I'm still kicking this around, although given the state of my wallet just now I'm probably not seeing an imminent installation...

But seeing the discussion in the current thread Willo started with questions about batteries for a 24V thruster, leads me a a question of 12V vs. 24V selection...

Assuming batteries installed within 2' of the thruster... is there any significant advantage to a 24V unit over a 12V unit? Using the Side-Power SE100 12V and 24V models as examples, both spec to the same thrust: 100 kg at 10.5/21.5V, or 116 kg at 12/24V.

Our ride is essentially a 12V boat, and I'm thinking a 12V thruster would simplify requirements for charging sources...
Thoughts?

-Chris
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Old 11-20-2018, 06:41 AM   #31
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24V gets spec'd when the thrust requirements exceed those available in 12V. If on your boat you can spec an appropriate 12V unit and your boat is 12V, I'd go 12V. Higher volts make sense on larger units as the 24V allows physically smaller cables and physically smaller motors.
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Old 11-20-2018, 07:14 AM   #32
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I used two 12V AGM batteries wired for 24V for SE80 Side Power 24V thruster. I use a Sterling 12V to 24V charger for re charging when underway pulling from house bank charged by alternator on FL120. 12V house bank charger maintains and tops off at the dock. Works great.
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Old 11-20-2018, 09:14 AM   #33
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So at this point i'm going with the two NorthStar group 31, I can get a better price on them then the Odesseys for my SE120 side power. Then I think i'll be going with a Parallel / Series relay and recharge off House or Start bank. Each has its own alternator.
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Old 11-20-2018, 09:47 AM   #34
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I am in the process of installing a Side Power SEP170-250 24v in my Californian 55. I have ordered 2 Odyssey PC2150 group 31 AGM batts. Also, a ProMariner 20 Plus. I looked at more expensive chargers but could not justify them. Now I read this thread and wonder about the wiring. Maybe I should return the charger and go with the 12v to 24v switch for $60 bucks. I would like everything to charge off of the alternators and the generator not just at the dock. I don't know much if anything about this stuff so i need some help here.


I'll want of course to charge off of the shore power.
I have a 4kw generator and a 16kw generator so I want to charge off of them.
I'd like to keep the charge up from the alternators but since I run lots of power, I do need to run a generator daily so maybe I don't need the alternator source.


I have two 8Ds as starters for my Cat 3208s. The Port is isolated from the house bank, the Stb is included in the house bank. House bank is 2 8Ds. So should I drain the house I can always start the port engine. I also have a small start batt for my 4kw gen. Not sure where the 16kw gets its start energy. The boat is still new to me.


I have the charger and batteries on order. Now is the time to make any changes. Sounds like I did ok with the batteries. What about the charging system? Any suggestions would be welcomed.
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Old 11-20-2018, 12:52 PM   #35
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Originally Posted by Ski in NC View Post
24V gets spec'd when the thrust requirements exceed those available in 12V. If on your boat you can spec an appropriate 12V unit and your boat is 12V, I'd go 12V. Higher volts make sense on larger units as the 24V allows physically smaller cables and physically smaller motors.

Thanks! I'm translating that to mean since the SE100/185 (185mm tube) is good for the boat, and since we'd mount batteries adjacent to the thruster, there'd be no advantage to the 24V unit versus the 12V unit. Yes?

Given a 12V boat, I'm seeing it being a lot easier to deal with charging with the 12V thruster...

-Chris
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Old 01-12-2019, 02:47 PM   #36
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batteries for 24v thruster

I’m going to bump this thread as I’m looking for input. The existing batteries for my Wesmar 24VDC bow thruster (unknown hp) are Northstar NSB M12-210. They are a very expensive AGM, and are basically a 4D at 132 lbs a piece. The maintenance logbook indicates they were installed February 2010, so they have 9 seasons. Realistically they are nearing end of life. So I did some tests:

With the charger just turned off for the test. Batteries are at 13.27 Volts, measured at the battery with digital meter.
5 second thruster test: drops down to 9.2. Volts during the test. After the test, recovers to 12.94 volts quite quickly.

It did this 4-5 times. The thruster seems ok, perhaps a little less jump than I remember. Is the voltage drop to 9 volts excessively low?

Jim
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Old 01-14-2019, 02:00 PM   #37
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A further update: I used the clamp meter and measured a peak draw of 368 amps @ 24 VDC = 8832 watts / 745 = 11.8 electrical hp.

However I had measured 9.3 VDC at the batteries during operation, which would suggest a possible correction of:

2*9.3/24*11.8= 9.2 effective hp.

Does this make sense?

Jim
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Old 01-14-2019, 03:17 PM   #38
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9V when running sounds a bit low, but if thruster is providing enough thrust, it is good enough. What happens if you run it like 10-15sec? When my flooded batt gets tired, not only do volts go low, but an extended run you can hear rpms dropping.
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Old 01-14-2019, 04:36 PM   #39
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I’ve not noticed a change in RPM on longer tests. I realize now, when I did the test at the dock, the 40 amp charger was on, and able to contribute 40 amps @ 12 VDC. Probably should have done this test with the charger off, so I should probably repeat the test with the charger off and also for a longer period.

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Old 01-15-2019, 12:18 PM   #40
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Fully charge the batteries to float, then disconnect them. Wait 24 hours and then test them.

Nigel Calder is the best source of this sort of information - buy his book!

How long do you use your thruster for? 60 seconds? I think you need a starter-type battery, one that produces a large rush of amps for a short period of time, then is recharged. A CCA rating of 1100 amps is a good size to take care of the inrush current; take 370 amps out for a minute, you have used about 6 amps of your battery capacity which means a rapid recharge to full specs. If you use short bursts of thruster rather than steady on, you have two considerations - the starter-type battery will recover a lot between bursts but the inrush current is largest at the initiation of starting the motor and will also stress the relays more, causing a shorter time-between-fail for them (so keep spares).

Start batteries are designed for multiple high-load "bursts" and immediate recharging but deep cycles are NOT designed for that kind of loading.
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