Engine Starting Video / Real World Amp Load Data

[Maine Sail]

Hi All,

I saw a need for something often debated but rarely ever clarified.

Many sailors/boaters often believe that you need to switch back and forth between your house bank and your start bank or as I prefer to call it, "emergency bank" of batteries for engine starting.

The truth is you don't. Switching back and forth from bank 1, to bank 2, only leads to eventual human error, as has been reported here and elsewhere all to often. By switching back and forth you will, in due time, fry your alternator diodes with a mental lapse or via a crew member who's been asked to switch banks.

The reality is that your system should be wired to prevent this but that's another subject for another day and most will never get this far down the project list. I am simply trying to prevent any more fried diodes with this video!

Another mis-truth that is often perpetrated amongst sailors is the absolute need to use a "starting" type battery to start your small diesel engine. This mis-truth has caused many a sailor to start their engines using their "starting battery", then once running, switching back to the house bank or the ALL position to charge via the alternator. This practice has resulted in many, many, many fried alternators! The truth is that for most small diesels any sufficiently sized deep cycle house bank WILL start your motor just fine and there is no need to mess with the switch! Leave your start bank for an emergency!

This video will show why it is not necessary to use a thin plate high CCA rated battery to start a small auxiliary diesel engine. The max load when starting my engine, a four cylinder 44hp, is approx an average of 132A amps for less than two seconds. Any deep cycle marine battery you can find will have a LOT more than a 130+/- CCA, CA or MCA rating.

Start batteries don't, and won't, generally last as long as a true thick lead plate deep cycle battery so dollar for dollar deep cycles will generally cost less in the long run.

You should not be afraid to use your deep cycle house batteries to start your engine. I've always started my engine on my house bank. Hopefully this video will give some owners the piece of mind around the subject of starting and how little it actually consumes.

What Happens When My Engine Starts Video (LINK)

Or click the photo:


Stats:

Engine - 2003 Westerbeke 44B, 44hp four cylinder diesel (marinized Mitsubishi).

House Bank - 2 Group 31 batteries 120 ah rated each / 240ah bank

Glow Plugs - They consumed between 30 and 56 amps for about 8-10 seconds.

Starter - Average draw of approx 132A amps for about two seconds.

Battery Monitor - Xantrex XBM

 

[Ross]

That's about what I expected. Cranking a 426 cu.in. V-8 takes a bundle but not the little engines that most of us have.

 

[Maine Sail]

Most folks..

That's about what I expected. Cranking a 426 cu.in. V-8 takes a bundle but not the little engines that most of us have.

Most folks assume it is a LOT more than it really is that is why I posted this.. Nothing better than real world data...

 

[Don S/V ILLusion]

Good info again MS

As they say, all things are relative; some more so than others...

Once had an 11hp U5411 that would kill a 400 amp bank before it started sometimes but you're demo is quite infomative. By comparison, my 4JH will start if I just look at the igniition. Regardless, having a separate emergency battery is always good seamanship.

Your obvious desire to assist others is well appreciated.

 

[Bob V]

Thanks Maine Sail

I suspected that. That is the reason that I did not install a starting battery on my new C42. I had one on the last boat and never needed it. My approach on this boat has been to buy a starting battery and keep it stored under the cushions with a couple of heavy cables that can be hooked up to the house bank if I ever wake up with dead batteries. I charge it when I am connected to shore power with a small charger that I have for my dinghy batteries.

My question for you is - If I wake up some morning with 3 4-D batteries that are dead for whatever reason and I hook up a Optima starting battery to one of the house banks like a jump start, will the empty batteries "steal" amps to recharge themselves before all that good juice gets to the starting coil? I alway keep my battery selector switch on "both".

 

[Ross]

Re: Thanks Maine Sail

I wonder if Branch fusing would be a safe approach to protecting a boats electrical system from over load. My house load is less than 50 amps if I turn everything on. And my starting load is added to that. But if I fused the house load at 50 amps and the engine starting circuit at 75, Then a fuse would blow before any wire got hot enough to start a fire. By dividing the loads I could use small less costly fuses.

 

[Maine Sail]

My question for you is - If I wake up some morning with 3 4-D batteries that are dead for whatever reason and I hook up a Optima starting battery to one of the house banks like a jump start, will the empty batteries "steal" amps to recharge themselves before all that good juice gets to the starting coil? I alway keep my battery selector switch on "both".

YES!!!! The optima may not be able to recharge the other bank enough to start the engine. best to disconnect the house bank and wire in the optima..

The best move is to wire the 4D's in parallel, that's how your using them, as one large bank, and leave #2 for the start battery...

Not the best practice to connect a smaller emergency battery to a large dead house bank. Just use the known good bank..

 

[walt]

Thanks for posting..

There is one thing about a starting battery vs. deep cycle that I wonder about. They dont really spec this but Ill call it a "short duration output impedance" and the spec would tell how far a battery voltage would drop for a given current. Note that in the video, the battery voltage went from 13.15 and it looked like it flashed about 11.75 volts (delta of 1.4 volts) and its possible that the sampling rate of the meter display missed an even lower voltage. And the voltage poped up very quickly since the motor also started quickly.

A deep cycle battery doesnt need a very low output impedance since it delivers current at a slower rate. But with a starting battery, you would expect the output voltage to remain fairly solid even with lots of current.

If the output impedance of a deep cycle battery vs. a starting battery were only a factor of two, twice the size deep cycle would give the same output voltage at the same current. But if it were a factor of 10... things might start mattering.

Also, in the video, we saw a delta of 1.4 volts during starting but this was with batteries which were likely topped off. Would you still get the same delta of 1.4 volts if the batteries were at 50% and putting out less voltage even before the start.

And of course, what voltage does the starter begin to "care" that its input voltage too low?

No argument at all on the conclusions, just something Ive wondered about.

 

[Bob V]

Thanks for the reply Maine Sail

So if that unlikely event ever occurred I could disconnect "B" which is a single 4-D that is mounted forward for the windlass and just put the "B" leads on the Optima. Then I would move the switch from "both" where it has always been to "B" while I start the engine. After the engine is running I would move the switch back to both so that the alternator starts charging the "A" bank which is two 4-D's in parallel.

Or would it be better to just leave all of those discharged batteries off-line and use my Optima to get home and preoceed directly to the battery store?

 

[Stephen K]

seeing is believing

I too have always assumed that the draw would be much more (you know what they say about ass-u-me).
Thanks for the facts Maine Sail ! When needed, I will be better off directing my money towards a good pair of 6V Sams golf cart batteries vs. adding a dedicated start battery.

 

[kloudie1]

Nice work, Maine Sail !!! I have been doing this for many years with no problems.. I do carry one of those little portable “jump starters” as an emergency battery. It can be connected directly to the terminals on the starter motor, and will start the Yanmar 3 GMF. In the old days, the battery manufacturers warned against high amp draws on the deep cycles because it would knock off a lot of plate coating, and quickly foul the plates and short them at the bottoms.. Most new deep cycle batteries don’t do this.

 

[Lyle]

I still prefer a seperate start battery

The main advantage of a seperate start battery (IMHO) is never having to reposition my battery switch to prevent a dead battery. Several respected marine experts (including Nigel Calder) have long made the argument that one house bank and a seperate start battery bank is the most efficient and user friendly system. Any time you have to switch battery banks to manage your electrical requirements you have introduced the possibility for error - and the possible result of dead batteries. Also, normally the start bank is also charged from it's own charge source ensuring it is always fully charged. Yes you could carry a portable emergency start source - but once again you have to remember to always ensure it is fully charged or it will be useless when you most need it.

 

[Maine Sail]

The main advantage of a seperate start battery (IMHO) is never having to reposition my battery switch to prevent a dead battery.

Yes but only if you have it wired in a dedicated fashion, meaning directly wired to the starter via an on/off switch and it does not go through a 1/2/ALL/OFF switch.

Several respected marine experts (including Nigel Calder) have long made the argument that one house bank and a seperate start battery bank is the most efficient and user friendly system.

This is exactly my point as well. The only difference is that I realize the potential for human error is more common than one would assume. My point is to ALWAYS have two separate banks, a house and a start/emergency bank, but if you have a 1/2/ALL/OFF switch leave it in the 1 or house bank position and never move it! My point is that you do not need to actually use your starting battery to start your motor. This avoids costly "switch errors" or frying of your alternators diodes..

Any time you have to switch battery banks to manage your electrical requirements you have introduced the possibility for error - and the possible result of dead batteries.

That is the point of my entire post!

Also, normally the start bank is also charged from it's own charge source ensuring it is always fully charged.

Only while at the dock. I have yet to see a production boat (eg: Catalina) that has two charging sources while under engine power that was not a custom ordered upgrade from the factory. Most boats while using alternator charging require the switch be set in ALL or an added charging relay, isolator or Echo type charger be used. If you use an Echo or combining relay you'll never need to move your switch from the house bank position and your start/emergency battery will always be charged and ready for an emergency. Utilizing the ALL position is a dangerous habbit to get into.

Yes you could carry a portable emergency start source - but once again you have to remember to always ensure it is fully charged or it will be useless when you most need it.

I don't recall anyone ever saying to not have a seperate start/emergency bank.

 

[Lyle]

Maine Sail, I think you took my post the wrong way. I am certainly not disputing that you cannot start your engine with your house bank and I certainly do appreciate your effort to produce your video. And I agree that the high amperage draw during engine start is normally of very short duration - although a high amperage draw on a half depleted house bank could drag down the bank voltage enough to cause problems with any running 12 volt appliances, refridgeration, heater, or inverter that require a minimum voltage to operate. Also, if your house bank was fairly depleted your starter would turn over slower which could cause slow or difficult starting - further depleting your house bank. All I am saying is, IMHO I believe that the most efficient usage of stored electricity for your boat is to have a single large house bank. You end up with more available amp hours in one source using the 50% discharge rule v.s. using 2 house banks and trying to keep track of the state of discharge of each bank. In addition, I like to have a seperate battery dedicated ONLY to engine start - call it my peace of mind if you will. Yes that battery has its own seperate battery switch and seperate charging source through an Echo charger. I also have a LINK 1000 battery monitor to keep track of both banks. It was not simple to install but it it is VERY easy to operate. Under normal circumstances I never have to move ANY battery switch - at the dock charging, or underway charging with the engine, or while at anchor. We all have our own opinions based on our own experience. For me, I have spent well over 1000 days at anchor with this system on 3 different boats - it just works for me. Just my 2 cents worth.

 

[Maine Sail]

In addition, I like to have a seperate battery dedicated ONLY to engine start - call it my peace of mind if you will. Yes that battery has its own seperate battery switch and seperate charging source through an Echo charger. I also have a LINK 1000 battery monitor to keep track of both banks. It was not simple to install but it it is VERY easy to operate. Under normal circumstances I never have to move ANY battery switch - at the dock charging, or underway charging with the engine, or while at anchor. We all have our own opinions based on our own experience. For me, I have spent well over 1000 days at anchor with this system on 3 different boats - it just works for me. Just my 2 cents worth.

That is the system most every cruiser should have! The harsh reality is that maybe 5-10% do and the other 90% use a 1/2/ALL/OFF switch and they are most likely not going to spend the bucks to convert to an Echo and hard wired start battery even though they probably should..

I have never had a problem, even with sensitive electronics or motors, starting my engine even at a 50% discharge but I have more than one batteries worth of capacity for my house bank.

I would caution against starting on the house batt with just one group 27 as a house bank! One battery IMHO does not make a "bank"...

You have a great system,and one many boaters should embrace, but from what I've seen 90% of boaters don't. If you do a search here on "fried alternators" you'll see what I mean. My original post was not aimed at systems like yours and was intended for the 1/2/ALL/OFF crowd and is whay I said this in that post.

The reality is that your system should be wired to prevent this but that's another subject for another day and most will never get this far down the project list. I am simply trying to prevent any more fried diodes with this video!

Sorry for the confusion!

 

[Hermit Scott]

Miane Sail

I bought a boat that had all the electrical wiring harness to the engine and batt. banks removed. Which is fine by me. I don't have a problem rewiring the engine controlls and gages. What I am not 100% clear on is the battery/alternator/shore-charger configuration I should use.
I just bought 2X 125 amp hour batteries. I have a charger designed to charge two seperate batteries.
I have seen you say that the house bank should be wired in parallel. I agree, that's what I will do with those.
Do I use only one side of the charger hooked to the bank then, and keep the switch on '1'? not '2' or all? Of course making sure the charging wires are for the #1 battery.
The alternator is a 35 amp internal regulated hitachi. I took it apart, greased the bearings and painted it with high temp paint. I just had it tested minutes ago and it works.
Is it safe to connect the charge wire from the alternator directly to the + teminal of the battery bank to facillitate recharging?
I will run the heavy cables + and - directly from the battery bank to the starter. Then add a starter switch. Can the alternator be hooked directly into this system with out damaging anything? Is it ok to hook the alternator directly to the starter, since it's so close locationwise. I always appricaiate your emperically spawned wisdom.

 

[Maine Sail]

OK.

What I am not 100% clear on is the battery/alternator/shore-charger configuration I should use.

I just bought 2X 125 amp hour batteries. I have a charger designed to charge two seperate batteries.

These leads should run from the charger to each bank and be fused close to the battery.

I have seen you say that the house bank should be wired in parallel. I agree, that's what I will do with those.

Yes but only if they are 12V batts. If they are 6V batts you need series to get 12 volts.

Do I use only one side of the charger hooked to the bank then, and keep the switch on '1'? not '2' or all? Of course making sure the charging wires are for the #1 battery.

The easiest way to wire a charger is direct to the battery banks not through the switch. This way you can turn off the batteries and disconnect them from any loads when you leave the boat.

The alternator is a 35 amp internal regulated hitachi. I took it apart, greased the bearings and painted it with high temp paint. I just had it tested minutes ago and it works.
Is it safe to connect the charge wire from the alternator directly to the + teminal of the battery bank to facillitate recharging?

Personally I feel wiring direct to the house bank is the preferred method as you can never disconnect the load via the battery switch. If you do this you'll want a charging relay or a Xantrex Echo Charger to keep the start bank charged. I really prefer the Echo charger to a charging relay but I have a charging relay on my boat and thus far it's been fine.

If you add an Echo charger or combining relay for the starter battery you'll only need to wire the house bank to the battery charger lead not both batteries.

I will run the heavy cables + and - directly from the battery bank to the starter. Then add a starter switch.

Here is a good wire gauge calculator Wire Gauge Calculator (LINK)

Can the alternator be hooked directly into this system with out damaging anything?

Yes if wired correctly!

Is it ok to hook the alternator directly to the starter, since it's so close locationwise.

Not if you want to avoid the battery switch. I'd run directly from the alt output post directly to the positive post of the house bank and by-pass the switch all together. This of course only works with an Echo charger or battery combining relay.

I always appricaiate your emperically spawned wisdom.

Always glad I can help.

 

[Scott B]

Re: OK.

I have the 1/2/Both/Off switch with 2 group 24's on 1 and a deep cycle start battery on 2. I leave it on 1 all the time, but actually had to use the start battery twice this summer. I think one of the house batteries is gone bad as they don't seem to hold the charge as long, and hence looking into 4 golf batteries to purchase over the winter. After starting on the back-up battery should I leave it on 2 or switch back to 1 to charge the house under engine power. I have an echo charger for the start battery.

Or what I should be doing is separating the start battery from the switch alltogether and only switch it on if the house goes down? ( but better not if I have 4 x 210 aH)

 

[Don S/V ILLusion]

check this out Scott

Scott
It might be worth it for you to read the following:

http://www.c34.org/projects/projects-electrical-system-upgrade-2.html

This sounds precisely what you are trying to get to and includes a schematic of what is close to the ideal setup for you.

 

[Scott B]

Re: check this out Scott

Don, it appears that the engine start battery is being used to start the engine each time and not being kept in reserve for emergency start only when the house bank goes dead. In an emergency he either ties the house and engine batteries together or tries to start off the house bank. And if he shuts off the engine start battery at the switch he cannot charge from the echo charger. This is opposite to what Maine Sail has been saying.