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Old 01-19-2018, 08:11 PM   #21
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its not rocket science

a starting battery is designed for hi current short draw usage, it is also designed to be kept at or near a fully charged state

a deep cycle battery is designed to be drawn down over time to power parasitic loads, it is designed to "give over time" and to do so for extended periods of time

the dual purpose batteries are an attempt to fill both needs from one source, not a best of both worlds, but more like this is the best we can do for both
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Old 01-19-2018, 08:24 PM   #22
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Deep Cycle vs. Starting Battery
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Have you ever wondered why there are different sizes or types of batteries? Did you know every battery type serves a specific functionality? Well when it comes to the battery world, the type chosen and its usage varies significantly. Depending on both how much power output you require, and for how long you need power being produced is how the correct option can be chosen.
The two primary battery options that you will find will either be defined as “deep cycle” batteries, or “starting” batteries. It is very important that you find the correct battery for your particular application, as the wrong choice can affect both the battery’s efficiency as well as its lifespan.
Our first variety, deep cycle, is meant to provide a continuous current of the same intensity for a prolonged time span. Although they are certainly capable of providing surges of power, this is not their primary purpose. Because of the internal structure, they can be used for starting, but tend to provide a lower cranking output than similarly sized starting batteries. Also important to the deep cycle battery is that once discharged, it is best to recharge at a lower amp rating for a longer amount of time, and not to simply be “topped off” quickly. Quick charging could eventually shorten the cycle life of the battery.

Starting batteries occupy the opposite end of the spectrum, being designed to provide quick bursts of energy, such as a car would use while starting. This only discharges the battery by about 1-3%, which is then topped off typically by you vehicles alternator. This is perfectly acceptable for a starting battery, and ensures that they are always ready to provide maximal current on demand. The drawback being that in order to provide peak cranking power, a starting battery will trade off some of its reserve, and deep cycling capacity.
The bottom line. Deep Cycle batteries provide a greater reserve capacity, but cannot deliver as many peak CCA’s (cold cranking amps). Starting Batteries are made to provide high power for higher amp, more frequent short draws, and limited long term discharge. Ultimately, your primary need should determine your battery choice. Choosing the right battery always provides the right amount of power, and does so for the right amount of time.
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Old 01-19-2018, 08:45 PM   #23
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so what does the math say for general windlass use?
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Old 01-19-2018, 09:03 PM   #24
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pto driven hydraulics off of the main propulsion engine
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Old 01-20-2018, 12:01 AM   #25
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On my MS 34MK 1 I put a big 8D next to the biggest Vetus thruster recommended. I then put a solar panel, controlled, as only charging source. I wired it up with much smaller gauge wire from the panel to battery so big wire, long run with high amp draw to feed thruster from the middle of the boat would not be necessary to carry the amps to power the thruster. Battery to thruster, 2 feet..about. Small wire to keep it topped from the solar panel. Worked great.

Currently, on my Present I have a main engine driven v belt driven hydraulic stern thruster. Were l starting from scratch, I would have a 12 volt hydraulic power pack pump off the house bank pushing thruster(s) and windlass, independent from the main. I think that would work really good.
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Old 01-20-2018, 06:33 AM   #26
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so what does the math say for general windlass use?
Ooops, meant thruster....

To me.... the logic could go either way..still interested in seeing the math....
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Old 01-20-2018, 10:00 AM   #27
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OK, here is some math:

A midsize 12V Sidepower thruster such as what would be installed on a 34-38' trawler draws about 200 amps according to SP's literature and requires a minimum of a 300 CCA rated batttery, Notice that starting batteries have CCA ratings and deep cycle batteries typically don't. So SP is implicitly recommending starting batteries. A group 24 or 27 will meet this CCA spec.

If you were to use a group 24 deep cycle battery, these are usually rated at about 70 AH of capacity. So you would be drawing about 3 times its AH capacity in instantaneous amps. Ignoring the huge inefficency of doing this, such a battery would only last 20 minutes at this draw. Not that a starting battery would last any longer, but I suspect it would last a little longer at this rate. That is what it is designed to do.

As another data point, a small three cylinder diesel, the Yanmar 3GM that are commonly used in sailboats, draws about 200 amps starting and is often fitted with a group 24 starting battery.

Seems to me that a starting battery is the preferred type. But it won't hurt a deep cycle battery if it is a decent size one. Drawing 200 amps from a pair of GC batteries will work and won't hurt the battery (assuming it is immediately recharged) but won't power the bowthruster as long as an equivalent starting battery.

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Old 01-20-2018, 10:59 AM   #28
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I think it is an gravity feed oiler for the thruster.
It is, but the beauty of it is that by having the level of the oil above sea level, there will be slight positive pressure on the seal, so any leak would be of oil going out, not seawater coming in.

And my take on deep cycle or starting is that deep cycle is best (longer lasting), so long as they can put out the necessary amperage. In my case, ALL of the batteries are deep cycle, but the capacity is sufficient to put out the amperage necessary to run the high-demand stuff like windlass, thruster, crane.
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Old 01-20-2018, 11:11 AM   #29
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My boat is setup with a dedicated thruster/windlass bank of 2 8D AGM batteries located in the compartment under the cockpit aft. This powers the bow and stern thruster as well as the windlass. This bank is charged by a dc-dc charger from the house bank.

Yes, there is a very large 00 cable that runs from the positive buss bar in that compartment that runs to an auxillary dc panel in the forward end of the ER. There, the power to the bow thruster and windlass are controlled by relays and 1/0 cables from the ER to the bow.

The system uses lots of heavy and expensive cable but it also means that one bank controls both thrusters and the windlass. All in all, I like the system a lot.

If I was going to start from scratch, I would certainly consider placing a battery in the bow for both the thruster and windlass. I would still use a dc-dc charger but that would mean running small gauge wire from the closest and most convenient buss bar from the House bank. I would still use a deep cycle battery, not necessarily for the bow thruster but for the windlass.

John mentioned earlier in this thread the idea of just upsizing the house bank and using it. I seriously considered doing this when I replaced my house bank. Just combine my thruster bank and house bank. However, the thruster bank was replaced by the PO so are relatively new and in good shape. No need to replace it at this time. However, if it does need to be replaced down the road, I may yet consider that.
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Old 01-20-2018, 12:02 PM   #30
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The idea that starter-type batts are "better" at feeding high-amp loads is only true at AH sizes tiny for house banks.

Vendors generally don't publish the CCA for true deep cycle batts, because rightfully suspicious buyers would think "aha that's just a pseudo-dc dual use starter batt".

Obviously all batts **have** a CCA rating, it scales along with AH, so get a large enough AH capacity bank CCA becomes irrelevant.

Actual starter cranking usage is so short and infrequent it does not draw even a small batt down more than a fraction of a percent.

For many thruster setups, and windlasses, that is not true, can be a lot of AH draw very quickly. If any high-amp usage is depleting a bank by say 10+% DoD on a regular basis, that is by definition a deep cycling use case.

Large say 8D bank can handle the loads, but if not true deep cycle plate design, their **longevity** will be a small fraction of what you would get from a true deep cycle bank.

If your thruster usage is very light, draws your starter-style batt down just a few percent, then it doesn't matter.

And again, if at all possible, create a single massive bank that feeds House and thruster loads, Peukert's law means a single 800AH bank has much higher total AH, shallower cycling and longer life compared to a 500AH House separate from a 300AH bow bank.

It may require very heavy gauge wiring over the distance, but a one-time expense that saves money on consumables is a good investment.

And if your installation space requires AGM, note that Lifeline, Odyssey and Lifeline batts have **huge** CCA ratings but are in fact excellent true deep cycling as well, even those in automotive BCI sizes like G31

e.g. Odyssey PC-2150 series

Excellent for AGM that is; unless you really need sealed, FLA are more robust, long-lived and of course much better value.
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Old 01-20-2018, 12:07 PM   #31
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So would this make a decent battery for a thruster? Maybe 2 in series for a 24v system?
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Old 01-20-2018, 12:17 PM   #32
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I'm not familiar with Dyno's different lines, but CMS has stated they and Rolls-Surrette are exceptional makers of true deep cycle FLA batts, the only ones in automotive BCI Group form factors like G-27 G-31 etc

But if you go to a bank based on flooded GC or other lower-voltage cells, you can get much better cycle-lifetime ratings at much lower prices.

Deka's Duracell GCs sold at Sam's and Batteries+ for ~$200 a 200+AH 12Vpair for example, $400 per 24V.

But if Dyno says e.g. that batt's good for 800+ cycles at 50% DoD, I reckon they like Rolls can be taken at their word, unlike most vendors in the 12V arena.
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Old 01-20-2018, 12:40 PM   #33
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John61ct: how would you power a 24 volt bow thruster from a 12 volt house bank?
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Old 01-20-2018, 01:42 PM   #34
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Personally I wouldn't be in that situation, but adapting the larger version of Yandina's Trollbridge might be one way.

http://www.yandina.com/troll2400info.htm

Ann-Marie Foster is the inventor of the first combiners (aka ACR / VSR), stands by her products unconditionally and is a joy to deal with

tech@yandina.com
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Old 01-20-2018, 01:54 PM   #35
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24 volt series connections are not uncommon.


There are relays that will do it or a series of relays are easily done too.


Google it.


FF had a link to the 24/12 volt relays that I have someplace but not handy right now.
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Old 01-20-2018, 02:00 PM   #36
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Are you saying a DIY setup with the same functionality as the trollbridge?

Also 12-to-24V converters are common, just get pricey as you get up to high amps.
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Old 01-20-2018, 02:06 PM   #37
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Are you saying a DIY setup with the same functionality as the trollbridge?

Also 12-to-24V converters are common, just get pricey as you get up to high amps.
Think this was it...if not, with more time I'll try to get it as it is easy enough to google....

12 Volt DC 1500 amp Starter relay replaces Delco 1119845 - 9-845 10-D1602.
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Old 01-20-2018, 08:01 PM   #38
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Think this was it...if not, with more time I'll try to get it as it is easy enough to google....

12 Volt DC 1500 amp Starter relay replaces Delco 1119845 - 9-845 10-D1602.
That won't charge a 24v battery bank. That relay simply bridges two batteries in series to start the engine using 24vdc. You can temporarily bridge them, making 24 volts out to the starter, and the other gear on the separate batteries stays at 12vdc.

Making 24vdc out of a lower voltage is what is called a boost / buck circuit and uses a capacitor to charge and discharge making power spikes far higher than the input voltage. They regulate the output to what you want, clipping the peaks and providing pulses of higher voltage (lower amperage) power. Another capacitor on the output side converts the pulses into a constant voltage flow.
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Old 01-20-2018, 08:34 PM   #39
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I didn't think we were talking about charging a 24V bank, and if we were I'd go with a DC-DC charger e.g. Charles Sterling's.

In this case

Two 12V "bank halves" usually kept in parallel for normal use and charging purposes

get connected via the devices under discussion in serial, for intermittent use at 24V as needed.

Higher amp loads http://www.texasindustrialelectric.c..._1119865CD.asp

For extended continuous use and flexibility in switching / triggering relays, looks like this is handy

http://www.texasindustrialelectric.com/SCM.asp

As a DIY electronics newbie, I'd probably stick to Ann-Marie's Trollbridge for the hand-holding, unless this alternative was much better or a quarter the price or something.
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Old 01-20-2018, 08:39 PM   #40
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iI believe the relay is to power a 24 volt load with otherwise 12V charging.

People have reportedly used it for 24V thrusters, lets see if FF chimes in with his experoence and 12/24V relays.
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