[Dave_E]

Hi All,

I have a typical sailboat 2 battery bank, shore power with charger, a diesel engine with a hight output alternator, no wind generator or solar panels. My old Universal is a cold blooded rascal that doesn't always perk right up when cranking. I've noticed that if I leave the charger on during engine starting (glow plug time included), it cranks and starts much easier than if I'm on a single battery OR both batteries. Then after it's running, I turn the charger off and you can hear the alternator load affect the idle.

Am I hurting anything my electrical system in any way by doing this? Mostly a winter thing (cold temperatures).

Dave

 

[Minnewaska]

I'm flirting with just enough knowledge to get someone hurt. There should be some sort of isolating device, so your alternator and charger aren't acting on the batts simultaneously. That does seem to be the case, if you notice the idle drop when the charger goes off.

What I find more interesting is that you would need the charger on to notice a difference in cranking. Makes me think the batteries are starting to lose their mojo. Presumably, your batteries are at full charge when you start up, so I wouldn't expect the alternator to have much work to do right after starting, although it sounds like they do.

 

[mitchbrown]

I'm sure whats happening is when you turn off the charger the alternator sees the decrease in voltage and increases its charge rate causing the motor to be loaded I don't see any problem. Sounds like everything is working properly

 

[Dave_E]

I'm flirting with just enough knowledge to get someone hurt. There should be some sort of isolating device, so your alternator and charger aren't acting on the batts simultaneously. That does seem to be the case, if you notice the idle drop when the charger goes off.

What I find more interesting is that you would need the charger on to notice a difference in cranking. Makes me think the batteries are starting to lose their mojo. Presumably, your batteries are at full charge when you start up, so I wouldn't expect the alternator to have much work to do right after starting, although it sounds like they do.

I am thinking the same thing about the batteries. They're 2 years old and the PO didn't spend any extra $ getting top of the line units. He was bragging about getting 7 years out of his last set, but he stayed on shore power and motored everywhere.

 

[dabnis]

I'm flirting with just enough knowledge to get someone hurt. There should be some sort of isolating device, so your alternator and charger aren't acting on the batts simultaneously. That does seem to be the case, if you notice the idle drop when the charger goes off.

What I find more interesting is that you would need the charger on to notice a difference in cranking. Makes me think the batteries are starting to lose their mojo. Presumably, your batteries are at full charge when you start up, so I wouldn't expect the alternator to have much work to do right after starting, although it sounds like they do.

QUOTE=Minnewaska;1846642]I'm flirting with just enough knowledge to get someone hurt.

Me too, electrics are kind of like magic. I think the alternator sees the battery voltage and acts accordingly. If it sees a full charge it should reduce output. But as above, it seems like it is not seeing a full charge. If the charger is left on for a while the batteries, assuming they are good, should be topped off.

As far as keeping the charger on while cranking, which I have done, I don't think it will harm the alternator? However, if you need the charger to start, it again looks like your batteries may be tired. Under heavy load, the circuit breaker in the charger may trip, which can be re-set.

Paul T

 

[Maine Sail]

Something is not right.. What is the charger, brand & model? Do you have an isolator that it passes through? How many amp charger is it? How is it wired?

If the batteries were previously on charge there should be no load to speak of on the alt after starting..

 

[tommays]

I would measure the battery's voltage at least a few hours AFTER the charger is OFF

I would also clip on the meter AT THE BATTERYS so you can view it while cranking and if it was a few features like minimum/maximum voltage you can see how low it drops while cranking

 

[JimsCAL]

I'm with Minne in not understanding why the engine should crank faster with the charger on. Fully charged batteries are capable of supplying far more amps than the charger. If the batteries are good and the charger has kept them topped off, the charger shouldn't make a difference. I would start by checking the SG on the batteries and cleaning the connections.

 

[capta]

There are auto battery chargers/starters designed for engine starting, but I would imagine doing this with the modern solid state marine chargers often, will decrease the charger's life span. You really need to heed the advice above on checking the condition of your batteries and I would check and clean every single crimp connector in the system. Just like on your car, passing current is not the same as having battery power; the car headlights may be bright, but she still won't start if the starter can't get the current it needs, which is considerably more than the headlights need. It also might be time to have the starter serviced as the brushes and commutator could need a bit of attention.

 

[Dave_E]

Thanks for the reply everyone. I suspect my batteries are not 100% and they're falling off real fast during cranking. I know the battery connections are all 100% OK, just went through them. The starter... couldn't tell you anything about it. I'm going to the boat this weekend and am going to do a "battery health" checkup (specific gravity checks etc.). The charger is a big WM thing, that does everything - again, I can only hope and assume it's working properly. I get all the green and yellow indicator lights on in all the right places along with voltage checks that look good. This is all for a "first start O the day". After that, it's 3-5 revolutions and it's running fine.

 

[christian.hess]

your batteries are just a bit tired thats all...

of course as soon as you turn the charger off the load of the alternator is heard more...its working more, especially if the batteries are not at 100 percent

anytime the battery voltage drops the alternator will work harder

I became a master in these scenarios cause I had for a long time no way to charge my batteries on the hook and sometimes the batteries would go untouched for weeks at a time, even months...

but I got to where I could start my old yanmar with the decomp levers off and get the engine barely turning then 1 lever, then the next and voila...often times with barely over 11 volts or so...

the same thing happened when borrowing a fresh battery to jump start my battery...loaner on...voltage up...start...take loaner battery off and back to big load on my batteries

(this is btw very damaging to certain types of alternators...they can really overheat this way and what usually goes is the internal regulator)

the first hour or so of running you couldhear a real strong sound and whine from the alternator...but after charging 2-3 more hours it got less and less cause the batteries were getting topped off...

anywhoo

try equalizing your batteries...you might get an improvement or slow charging separately over a long period of time

 

[sony2000]

A charger is supplying up to 1.7 volts over the batteries 12 volts. That's why your starter springs to life, and may have negative consequences. Shorter starter life.
Since you start in the cold weather, have you thought of using synthetic oil?
Five year old batteries are done. Change them.

 

[Jaramaz]

A charger is supplying up to 1.7 volts over the batteries 12 volts. That's why your starter springs to life, and may have negative consequences. Shorter starter life.
Since you start in the cold weather, have you thought of using synthetic oil?
Five year old batteries are done. Change them.

Well, Dave claims batteries are TWO years old. Still, something is not as it should be as Main Sail says. It could be
- batteries not good. Test the starting battery for capacity: measure Voltage during draining the battery with a known consumption, from peak Voltage until it has decreased to something between 11.5 and 12 V. Also note time. A high slope indicate low capacity, the slope should be nearly 0. (find more on the internet).
- to high resistance in the connections between batteries and starting motor.

In both cases does an external Voltage source help keeping up the start motor cranking. The start motor very power hungry, often in the range 700- 1000 W, corresponding to some 60 - 80 A, which is a huge current. As V= R*I, even a small resistance in the connection battery - starter will result in a huge voltage drop; something the starter really doesn't appreciate. Thus: wires shall be short, and have a large area, no less than 50 mm2, preferably 70 - 100.
It is not unusual that old wires get tired ... putting up too much resistance.
Note that is very difficult to get accurate readings on normal ohm-meters for these low restiances. Not a bad idea to test new cables.

Battery age has little to do with the consition, unfortunately. One full drain is enough to damage the battery.

BTW: bateries shall not be chaged continously. That will also harm ...

/J

 

[Minnewaska]

That depends on whether you have a multi stage automatic charger, which I would hope everyone that leaves their boats plugged it at the slip would. A proper charger will keep your batts at the proper voltage, which is good for them.

 

[sony2000]

Starting an old diesel in cold weather on a regular basis, and your a fool not to have synthetic oil. Then you can talk batteries.

 

[SteveInMD]

It sounds to me like you should do a load test on your batteries.

Do you know how your high output alternator is wired? One thing that can make cranking easier is to connect the excite wire for the alternator to the oil pressure switch on the motor. This will prevent the alternator from creating load on the engine until the oil pressure comes up when the motor starts. Mechanics will sometimes do this while installing a high output alternator. You should check to see how your is set up.

 

[Dave_E]

Hi All,

Excellent feed back - thank you. I went to the boat last night with the battery hydrometer. Results weren't perfect, but don't yet warrant new batteries. I little difference between 2 cells in each battery. I will equalize them this week, (that hasn't been done since I've had the boat - 8 months). We're into our warm season here in the PNW now, I feel confident about their state for the summer. Come this fall they will be 3 years old. I'm considering replacing them with GEL batteries next go-around. (That's another topic in itself I imagine).
Dave

 

[christian.hess]

3 years is getting there but definitely not scrap...equalize and in my opinion charge them separately over a looooooooooong trickle charge or period of time...

swap positions if you can too(main connectors battery, switch with one that isnt)

and then see how you do

you can also take a look at the starter and see if it needs a rebuild, starter can eat a lot of power if the brushes are worn uneven and not making contact well...you can also rewind it with new wire...

anyways while Im not a fan of synthetic for availabilty reasons and price on sailboat diesels what sony says is abslutely true...

ease of starting and oil flow when cold while be greatly enhanced...

I still think you have 1-2 more years left in the batteries especially after equalizing and charging separately...

the you can look into agms or whatever

good luck

 

[christian.hess]

That depends on whether you have a multi stage automatic charger, which I would hope everyone that leaves their boats plugged it at the slip would. A proper charger will keep your batts at the proper voltage, which is good for them.

one with a low trickle charge and low float charge is prefferable to me

a lot of chargers have a very high float charge for some reason some where around or over 14.5 volts

this is actually damaging more than it is helpful(in the long run)

you want a nice float charge around 13-13.5 and a trickle charge right above that...to get to that voltage...

the same can be said for solar voltage regulators...and thats why mppt controllers are preffered over regular shunt or on off type controllers

a good charger is money well spent, but not all of us can afford the real good ones

 

[mitiempo]

one with a low trickle charge and low float charge is preferable to me

a lot of chargers have a very high float charge for some reason some where around or over 14.5 volts

If the charger stays over 14 volts when the batteries are fully charged it doesn't have a float stage.