Selecting a Starting (SLI) Battery

[GordMay]

SELECTING STARTING BATTERIES:

All batteries aren't created equal. A battery's size, rated capacity, and its age help determine how it will perform. The old adage "You get what you pay for" can be very true for batteries - so here’s a few tips on selecting a Starting (SLI) Battery for your boat.

Be sure to purchase the correct type of battery for the job it must do. Remember an engine starting battery and deep cycle batteries are different.

The starting battery (SLI - starting, lights, ignition) is designed to deliver quick bursts of energy (such as starting engines) and has a greater plate count, and heavier interconnecting buswork. The plates will also be thinner and have somewhat different material composition.

The deep cycle battery has less instant energy, but greater long-term energy delivery. Deep cycle batteries have thicker plates and can survive a number of discharge cycles. Starting batteries should not be used for deep cycle applications.

The so-called Dual Purpose Battery is only a compromise between the 2 types of batteries.

Do not be misled by CA, MCA or HCA ratings.

Cold Cranking Amps (CCA) is defined as the discharge load measured in amps, that a fully charged battery at 0 degrees F (-17.8 degrees C) can deliver for 30 seconds while maintaining the voltage above 7.2 volts (1.2 Volts per cell). The higher the CCA rating, the greater the starting power of the battery.

To find the power of a battery, multiply the CCA number by 7.2 volts.
* ie: For a battery rated @ 600 CCA:
P = IV = (600 A)(7.2 V) = 4320 Watts
Conversely, for a starter rated at 4320 Watts:
I = P/V = (4320 Watts) ÷ (7.2 Volts) = 600 CCA

To start a 2 or 3-cylinder diesel engine, you may need approximately 600-700 CCA.
For a 4-cylinder diesel engine 700-800 CCA, and 8-cylinder diesel engine about 800-1200 CCA.
To start a 4-cylinder gasoline engine, you may need approximately 600-700 CCA. For 6-cylinder gasoline engine 700-800 CCA, and an 8-cylinder gasoline engine about 750-850 CCA .

Batteries are sometimes advertised by their Cranking Performance Amps (CA) or Marine Cranking Amps (MCA), describong the discharge load in amperes which a new, fully charged battery at 32 degrees F (0 degrees C), can continuously deliver for 30 seconds and maintain a terminal voltage equal or greater than 1.2 volts per cell .

Hot Cranking Amps (HCA) is measured at 80 degrees F (26.7 degrees C).

To convert CA (or MCA) to CCA: multiply the CA by 8.
To convert HCA to CCA: multiply HCAs by 0.69.

In hot climates, buying batteries with double or triple the CCA ratings that exceed the OEM requirement is a WASTE of money. However, in colder climates the higher CCA rating the better, due to increased power required to crank a sluggish engine and the inefficiency of the cold battery*. As batteries age, they are less capable of producing CCAs.

* Temperature vs Available Battery Power
At 80 Deg. F - 100% CCA Available (Select 100% Battery CCA vs Engine Load)
At 32 Deg. F - 65% CCA (Select 155% Engine CCA)
And for your Car:
At Zero Deg. F - 40% CCA (Select 210% Engine CCA)
At -32 Deg. F - 25% CCA (Select 350% Engine CCA)

Reserve Capacity (RC) is the number of minutes a fully charged battery, at 80 degrees F (26.7 degrees C), can be discharged at 25 amps until the voltage falls below 10.5 volts.

More RC is better in every case! In a hot climate, for example, if your boat has a 360 OEM cranking amp requirement, then a 400 CCA rated battery with 120 minute RC with more electrolyte would be more desirable than one with 1000 CCA with 90 minutes of RC.

Buy “fresh” batteries - never older than 6 months on the shelf (‘sulfation’ occurs when lead sulfate can not be converted back to a charged material, and is created when discharged batteries stand for a long time or from excessive water loss). You can usually find a small decal on the side of the battery container giving you the month and year the battery was shipped out of the plant. But figuring out when a battery was made isn't always easy. You must decipher a code, usually either printed on an attached sticker or stamped on the battery's case. There are several differing date “code” systems, so be careful in deciphering them (ie: ‘Trojan’ marks a Date on the post, which is 2 months AFTER manufacture - a “best before” date).

BCI Group: Manufacturers build their batteries to an internationally adopted Battery Council International (BCI) group number (24, 26, 70, 75, etc.) specification, which is based on the physical case size, terminal placement and terminal polarity. Batteries of the same BCI Group, may have differing CCA / RC ratings - so pay attention to the specifications. Accordingly, some batteries will offer more “bang for the buck”, than others!
BCI Group (Size) Chart: http://www.rtpnet.org/~teaa/bcigroup.html

Energy Density is the amount of energy, typically quoted in watt-hours per pound (wh/lb) or watt-hours per kilogram (wh/kg), that can be contained in a specific quantity of the energy source.
Ie: Flooded lead-acid batteries generally have about 25 wh/kg, and the latest advanced lead-acid designs claim about 50 wh/kg.

HTH,
Gord

How long should it take to charge a battery after starting a small diesel engine? How soon can I shut down my engine after leaving the dock?
Thanks

[sv_makai]

The time it takes to recharge your battery is usually dependent on how easy your engine is to start, batteryage, alt size, and rpm. (does it take alot to crank or is a turn the key and it fires). It usually around 15-20 minutes.

There are other concerns though. It can be hard on your diesel to start and run it for short periods. We found our last boat we were not running long enough to bring the engine up to temp before we shut it down with the batteries fully charged. We had started running the engine longer than needed just to charge.

[Talbot]

Gord, I usually like your primers on different aspects of boating, but consider that you have really been far to simplistic this time. A discussion on batteries which just looks at deep cycle and engine starter batteries is missing a lot of detail. Furthermore with todays boating needs, stating that an engine starter battery is good for Starting, lights and ignition is really WRONG.

Lights should always be run from the domestic circuit cause they are a small drain over a long period. It would have been more accurate to have discussed high current load items and low current load. For example items like the bow thruster and the windlass both need to be run from batteries that have high Cold Cranking Amp capacity - which is mainly found in engine starter batteries.

Deep cycle batteries are unsuitable for this because the shock of trying to provide such high current will damage the plates and lead to premature ageing.

However, there is a class of battery that is suitable for both applications, and that is the types that have their plates reinforced with carbon fibre . these are also suitable for deep cycle, and their design also allows them to be charged faster than a normal deep cycle battery. But they are normally twice the price!

You have also failed to discuss sealed, gel or open acid batteries, and the differences in charging regimes that these require. Sealed and gel batteries have considerable benefits in a boat that leans over a long way, and especially in a knockdown, whereas the open versions are good where you are pushing a high charge into the battery and may need to top up the electrolyte. Most good regulators and mains chargers will have a changeover switch for battery type to account for the different charge rates and peak voltage requirements, Sufice it to say the really important consideration for any battery bank is that the batteries should all be of the same type, and preferably of the same capacity.

[Alan Wheeler]

Hi Talbot, I think if Gord was to go deeper, he would be sitting at his keyboard for a couple of days writing an Essay. It's just tooo complex of an issue now. His overview is accurate and concise.
But yes you are also right that the issue is far bigger in our present day. Just to add, I have just replaced my Engine starting bank with the new Calcium/Calcium design. Wow!!! It produces 3 times the CCA of the originals in a smaller footprint. The other thing is, they maintain their "shelf" charge for 10 months. So I don't use the charger on them anymore. They have a slightly higher cell voltage, so they sit at 14.9V. Heavey little suckers though.
And to answer the other question below, just to put it a little more plainly, what goes out must go in. The concise answer is, what ever you took out of the battery to start your engine, must be charged back into it. So to give an accurate answer to your question is like asking "how long is a piece of string" But a ruff indication is when your amp meter is no longer registering a current. "Ummmm, isn't there a slight flaw in that theory" I hear you ask?? Yep. It doesn't take into account top up charge and yadda yadda. This is where a good three stage charger should be employed when tied to the shore and you have access to shore power. Otherwise, you can use a three stage on an alternator. But it will only work when the engine is running, and I get the feeling you don't runn it for long.
Which brings me to the next point and slightly off our topic. If you have a petrol engine, then it isn't really important about how long you run it for. If it is Deisel, it is a whole nother story. A good rule, start your deisel, place it in gear, even if tied to dock. Bring it upto 25-50% RPM and let is run till the temp gauge comes up to opterating temp. Then open her up and run it for a good 15Min. This excersise should be done once every 1 to 2 months. NEVER let a deisel warm up under no load. It will glaze up the bore and the engine will smoke like crazy. A glazed bore is hard to get rid off, but if you have a badly blue smoking engine on start up, put this practise into place and sometimes it will come right, if the damage isn't too far done. It will take many cold start/run ups to do so, but it can sometimes work. I won't go further into this subject, as it is also an essay in answer. Unless someone asks of course.

[GordMay]

Sailorman:
You’ll not likely ever fully re-charge a Starting Battery with a typical Alternator/Regulator set-up - due to the MUCH reduced acceptance rate of a very lightly discharged battery.

A battery is fairly efficient in accepting a re-charge up to approximately 75% of its rated capacity. More energy is required to charge the battery from 75% to 100% of its rated capacity, because a greater amount of electrolyzing of water takes place after 75% of the battery’s capacity has been replaced. You will have probably only discharged your typical Starting Battery to 95% (or higher) of it’s rated capacity (used < 5%).

As WHEELS said - “what goes out must go in”. When a battery is discharged, the same amount of power has to be replaced. However, some of the power is converted to heat and lost due to the resistance in the cables, connectors and elements within the battery.

As Captain Bill and Wheels also indicated, you must bring your Diesel Engine up to proper operating temperature each time you start it (before shut-down). This minimum duration will likely recharge your Starting Battery to nearly full charge (as close as it will be practicable to get it without sophisticated equipment).

As Talbot pointed out, my original post was very basic, and was not intended to be exhaustive, nor to address issues beyond the common Ratings applied to Starting Batteries.
Nor should my use of the industry standard term “SLI” (Starting, Lighting, & Ignition) be understood to imply that a Starting Battery be used to operate Lighting Loads, which (as he indicated) should be run off the Deep-Cycle House Bank.

I agree (/w Talbot) that “minimalist” postings can be a little dangerous (as in - a little knowledge can be a dangerous thing), but would like to emphasize Wheels’ comments about the time it takes to write full essays. The more exhaustive a tutorial becomes, the more exhaustive it must be (anything that appears complete must be complete). Magazines pay me between $500 and $750 for 2,500 to 3,000 technical articles - and it’s not worth it!. It takes ME at least 80 - 100 Hours top prepare a first draft article, and another 20 - 40 hours in re-write - which then gets technically audited, and professionally edited by the publisher.

FWIW
Gord

[CSY Man]

Hi Gord.

Which Magazines do ya write for?

Did I see yer stuff in a "Good Old Boat" magazine a while ago?

As for starting batteries:

I have a 1000 CCA for my 4 cylinder diesel, whereas a smaller one would surely start the beast as well.

For an additional $5.00 I bought it instead of the 800 CCA.
Figured I could use the extra oomph if I ever had to bleed the engine cranking it over again and again.

Happy with the battery, a DEKA, price was $65.00 4 years ago.

Hoping to get another couple of years out of it.

On a different subject:

My diesel engine (4-108) have been a bit difficult lately:
It is slow to start in idle:
After cranking for several seconds it reluctantly fires on one cylinder, then the next and finally it runs normally.

If I crank it with the throttle slighty above idle, it fires right up.

1) The cranking speed is fast and normal.
2)The injectors were overhauled 300 hours ago.
3)Filters and fuel is clean and fresh.
4)Using my electric "booster" fuel pump to assist the lift-pump makes no difference, it still is reluctant to start IN IDLE WHEN COLD.
5) It fires right up when warm.
6) It runs normal with lots of power when warm.
7) No smoke, cold or warm.
8) Idle speed is normal and by the book, about 700 RPMs.

Does the above indicate that the high pressure pump is ready for an overhaul?

Or some other problem?
(It seems that a lack of fuel at the injectors when cold is the culprit)

Any ideas? (And dollar amounts)

[Alan Wheeler]

Maybe I can offer some help. Unfortunately, there are many more questions to ask.
When the injectors were overhauled, did you get the pump done as well? Could be poor delivery pressure. An injector is basicaly a needle valve. The pressure of the fuel delivered by the pump overcomes the seat pressure of the valve and lifts the needle, thus squirting in through a very small hole under immence pressure. The Air in the cylinder is being compressed to a very high pressure and the result causes it to super heat. At the right moment, the fuel is blown in, in a fine high pressure mist and ignites. Thats possible No.1
Possible No.2 is still the pump. The pump delivers a metered dose of fuel. The dose is varied by a mechanical system in the pump. There is not a lot of variation in the amount of fuel being sent to the injector between idle and full revs. Most of the control of the engine is done via the main Air intake. But there is some adjustment going on in two area's. One is timing. The fuel must be delivered at the exact moment. That exact moment varies with RPM.
The other, as I mentioned above, is the amount of fuel being delivered. in the injector squirt. It could be that the pump is no longer delivering the correct dose at cold. The pump may need adjusting or repair. It will probably need an expert to remove the pump and have it bench tested and set up. They do this on a big machine.
And finaly while on the injector side, 300hrs ago, did you have the injectors rebuilt or just cleaned and set. They may need rebuilding or replacing.
And finally, although I doubt this your problem,
Does your engine use glow plugs? Could be a problem with that circuit. The engine when cold, sucks away the heat developed at compression, reducing the temperature. Plus a cold cylinder has poorer compression due to leaks past the rings and finally, the air doesn't expand as much due to no cylinder lining heat being transfered into the air. So the Glow plug helps the hole process along by giving enough heat to ignite the vaporized fuel.

Something it most likely won't be is a fuel supply shortage. Most Diesels won't start at all if air gets into the pump. The air compresses and acts like a spring in the injector line. Thus there is never enough pressure developed to lift the needle in the injector, so it won't fire at all. It is why you have to bleed a diesel engine fuel system if you have ever run it out of fuel. Plus a fuel delivery problem would most likely show its head when under power.
Hope something in that lot helps.

[CSY Man]

Thanks for big reply Alan.

No, the pump was not overhauled, just the injectors.

The invoice says:

4 Lucas Reman Injectors with new nozzles.

The books says to overhaul the injectors every 400 hours, but many folks run 'em longer than that without a problem.

Wonder it the problem with slow starting will go away if I adjust the idle a little higher...., but then of course the idle will be too high when the engine is warm...Perhaps 900 RPM and more shock-load for the tranny whenever I put the thing in gear.

Hmm, we shall see.

(Of course I am hoping that the pump does not need an overhaul, that could eaaily run a grand or so...)

[Alan Wheeler]

Mate, if your Mechanic is charging you $1K and I presume that is US$1K, one of two things need to happen. One, you need to get a new Mechanic, because you are being ripped off. Or two, I need to come to the US and set up as a Diesel Mechanic
No, don't adjust your idle RPM. Instead, on the end of the pump or somewhere around the pump, you will have an adjustment of the amount of fuel that is delivered. It will be locked off with a nut. Try adjusting that 1/4 of a turn at a time. Mark where you started and go no more than one full turn in either direction. Most likely it will be screwing in that will do the job. On the inside of the pump, there is a spring, and the tension of that spring can change with heat and time. This screw is kinda like a mixture setting. Although not quite that simple. It adjusts the fuel rack inside the pump.Too much and your engine will black smoke, not enough and you could lean the engine too much and cause excessive wear in the cyclinder. The Diesel fuel is also a lubricant in the upper cyclinder and a position is sort, between not enough fuel, causing wear, and too much causing wash off of the lubricating oil off the side of the bore causing wear. So you can see that that setting screw is an important adjustment.
So with that explanation, it is why the injector pump should be looked at. Cause it may be causing harm to your engine long term.
Going back to that setting screw, if your engine show's no sign of smoke at all, it is a good indication that the engine is too lean, and that maybe your problem. There should always be a little blackish colour in the exhaust smoke under full RPM load and acceleration.
Too much black smoke can also indicate nmot enough Air being supplied to the engine, but that is another story. Blue smoke is usually a sign of the Diesel fuel not being burn't correctly and totally. It's a good sign of poor compression due to engine wear or glazing of the bore.

I need to also add. I am NOT a qualified Diesel Mechnic. I have worked around motors all my life as a hobby. But please do not take what I have suggested as "advice from and expert". I suggest you seek expert advise and help.
I do hope this helps though.

[CSY Man]

Hi Allan and thanks for the additional comments.

Yes, I am talking $1,000.00 for a high pressure-pump overhaul.

The price is about $800.00 for the overhaull itself, but after a few parts and taxes and removal / installation is over with, I can smell a good grand...

Will look for the "mixture" screw ya mentioed and study up on the subject.

Well, the engine is not entirely smoke less: When I give it full throttle at low RPM, it belches out a good cloud of dark smoke, but not when running steady at "cruise RPM".

Try to avoid those full power take-offs, but occasionally one has to gun the old Perkins to avoid hitting a dock or other boats when caught in a big current or trying to run away from a bridge that is closing the spans as ya go under it.......

(Got 5 draw bridge between me and the ocean, they are manned by people that are rejects from McDonalds fast food minimum wage program....Almost lost the boat twice cause they were closing the bridge without looking...Max power saved the day, and the black smoke was clearly visible)

Thanks again for the advice.

[BC Mike]

I have not followed all of this post but just a suggestion re starting. The starter motors get tired and do not crank over the engine like they did when new. Easy to take off after disconnecting the battery. Take it to the electric fix it shop.
Michael

[CSY Man]

Starter motor is recently overhauled and spins fast with the 1000 CCA battery....As mentioned above..

[BC Mike]

This time I read all of your post. Up here where it is a bit cooler the diesel will never start at idle, it requires a heap of throttle to pump enough fuel in to fire. During the warmer months just a little bit as in hardly any throttle is required. I have a 2QM15 Yanmar. A drop of oil on the top of the pistons will reveal if the compression is getting a bit low. A hard cold weather starting motor that fires right up after having the oil drops is likely low on compression. Michael

[Alan Wheeler]

Sorry to take so long getting another reply in. Been away Sailing, but thats another story Sounds like things may be OK mechanically. Mike has touched upon a point that could be the problem. Cold. I am not familiar with temperatures you guy's like to go out and play in up your way, but it sounds like it could be one or maybe a combination of two things. Cold fuel definately could be one, But the other is the type of fuel being used. We don't have as cold a winters here in NZ, but a winter additive is still added to our Fuel. This additive does a couple of things, but the main one is it stops a waxy substance forming, that blocks Fuel filters. But it also helps the fuel ignite better when cold. It could be that the fuel in your tank does not have any additive (if you guy's use such over there). Just a thought, But it could be worth thinking about.