what revs for battery charging?

[IainW]

we have a Beta 1.5 diesel engine (i think ) and a 70 amp alternator (i think) to charge leisure batteries. What revs approximately should i set the engine to charge the batteries best? Is tick-over OK?

[Tony Brooks]

we have a Beta 1.5 diesel engine (i think ) and a 70 amp alternator (i think) to charge leisure batteries. What revs approximately should i set the engine to charge the batteries best? Is tick-over OK?

 

 

I would say whatever speed is required to put maximum charge into the batteries at that time. If may start at maybe 1500rpm or more and then as the batteries charge and the charging current falls gradually reducing to about tick-over. This puts the maximum load on the engine and gives you the minimum charging time. It will also give the fastest calorifier heat up.

[Arthur Brown]

Watch the current as you increase the revs, you may find tickover is too slow to give a good charge rate.

[LEO]

we have a Beta 1.5 diesel engine (i think ) and a 70 amp alternator (i think) to charge leisure batteries. What revs approximately should i set the engine to charge the batteries best? Is tick-over OK?

 

Hi,

 

depends on pulley sizes, alternator controller fitted?

 

Leo.

[Ryeland]

My Beta 38 with 100A Iskra alternator gives 105A at 1200rpm. Usually give it a bit more for better ventilation.

 

Best to borrow a clip on ammeter to make sure what yours is like.

 

Richard

[Ex- Member]

Hi,

 

depends on pulley sizes, alternator controller fitted?

 

Leo.

 

Generally regular car/van alternators put out their maximum amps around 5 to 6000 rpm so depending on how your alternator is pullied will determine it's rpm. I think my pulley is near to around 5 to 1 so when at 1000 rpm the alt will be 5000 rpm if I go up to 1200 rpm cruising on a river say, then I'm around 6000 rpm.

 

Pays to check out the curve chart for your alternator to see where it puts out its max rating.

Edited March 4, 2013 by Julynian

[Guest]

About 1200rpm on my Vetus, 90A alt, no external regs.

[Alf27]

I have the same engine, I use 1100 revs if I am stationary which gives me 64 ish amps to the batteries if they are discharged to 60%, I feel though that the cable from the alternator is a little bit small at 16mm sq. Hope this helps. Alf

[Doorman]

Is tick-over OK?

 

A similar topic was discussed quite recently and I quoted an instance where the owner of a fat boat used to run his Isuzu engine for hours on tick over to charge his batteries. One one occasion, his engine seized due to overheating and in fairness to the manufacturers, they replaced the engine under warranty, but insisted that he no longer let it idle this way as they would not cover the warranty a second time.

[IainW]

thanks folks, i had been running it about 1400 but i'll drop back a bit and get a multimeter to experiment a bit :-)

[Tony Brooks]

thanks folks, i had been running it about 1400 but i'll drop back a bit and get a multimeter to experiment a bit :-)

 

A multimeter will be all but useless as far as optimising the revs for battery charging. The DC amp scale is normally 10 amps for x seconds or if you are lucky 20 amps for x seconds. You need to be looking at 70 amps or more.

 

Now you can get a cheap, but good enough, multimeter that incorporates a clamp type DC ammeter that is good for 400 amps for may be a bit over £30 from a known supplier or cheaper via Ebay. One of those will do.

 

I repeat that there is NO fixed best speed for battery charging. You need to rev at a speed that produces the maximum charging current and they you will have to gradually decrease the revs as the charging current drops.

[Keeping Up]

Tony is of course quite right, you can't measure the charging current with a multimeter. But sometimes you can get an idea of the optimum speed by using a voltmeter. With a fairly low battery so that you are getting the maximum current from the alternator, gradually increase the rpm and you should see the battery volts steadily increasing. When a further increase in rpm produces no further increase in volts, that is about the best speed to run the engine.

[Guest]

Tony is of course quite right, you can't measure the charging current with a multimeter. But sometimes you can get an idea of the optimum speed by using a voltmeter. With a fairly low battery so that you are getting the maximum current from the alternator, gradually increase the rpm and you should see the battery volts steadily increasing. When a further increase in rpm produces no further increase in volts, that is about the best speed to run the engine.

Exactly what I do.

[Doorman]

 

I repeat that there is NO fixed best speed for battery charging. You need to rev at a speed that produces the maximum charging current and they you will have to gradually decrease the revs as the charging current drops.

 

Hello Tony,

 

What are your thoughts on the comment I made earlier regarding the boater with the wide beam and his Isuzu engine failure?

 

I only know about this instance as the original engine was retained by a local engineer who was looking to either recondition it or sell it on to someone else to do the same. One of the bores was particularly badly scored and the external paint on the block was evident of overheating.

 

Without knowing the design of the skin tank and it's efficiency, I would imagine that other than an air lock or insufficient coolant in the system, tickover speed would be sufficient to circulate the coolant enough to maintain a safe working temperature.

 

Mike

Edited March 6, 2013 by Doorman

[Tony Brooks]

Hello Tony,

 

What are your thoughts on the comment I made earlier regarding the boater with the wide beam and his Isuzu engine failure?

 

I only know about this instance as the original engine was retained by a local engineer who was looking to either recondition it or sell it on to someone else to do the same. One of the bores was particularly badly scored and the external paint on the block was evident of overheating.

 

Without knowing the design of the skin tank and it's efficiency, I would imagine that other than an air lock or insufficient coolant in the system, tickover speed would be sufficient to circulate the coolant enough to maintain a safe working temperature.

 

Mike

 

 

Hi Mike

 

I have no thoughts because I simply do not know enough about the installation. Being a fat boat the hoses to/from the skin-tank would be longer than normal and may well have been installed with or allowed to develop kinks and bend that created an airlock. I normal circumstances I too would expect the design to allow sufficient circulation at idle.

 

Plant tends to be left idling for hours so it is instantly ready when needed but that will only have a modest alternator fitted. If the marinisers decide to fit a very large domestic alternator as well then this will load the engine and make it create more heat when idling so this could be a factor in the problem.

 

If the OP follows my advice they should always have sufficient cooling flow for the load they have put on the engine. After all idling for an hour or more while in a lock queue is no different to idling for an hour at the bankside except the former sort of implies a degree of boating at a higher RPM before you got to the lock.

[nb Innisfree]

It takes a good hour for an i.c. engine's oil to get up to optimum temp. Idling from cold results in much longer warm up times and does the most damage, better to use plenty of revs initially when in bulk charge and load is highest, only idle when near max temp is reached, even then I would give it an occasional burst to increase splash lubrication of cyl walls.

[Tony Brooks]

It takes a good hour for an i.c. engine's oil to get up to optimum temp. Idling from cold results in much longer warm up times and does the most damage, better to use plenty of revs initially when in bulk charge and load is highest, only idle when near max temp is reached, even then I would give it an occasional burst to increase splash lubrication of cyl walls.

 

 

I would hope that modern IC engines use an oil jet to lubricate the thrust side of the cylinder wall rather than simple splash and if so there should always be enough pressure in the system at idle to ensure adequate lubrication.

[Doorman]

It takes a good hour for an i.c. engine's oil to get up to optimum temp. Idling from cold results in much longer warm up times and does the most damage, better to use plenty of revs initially when in bulk charge and load is highest, only idle when near max temp is reached, even then I would give it an occasional burst to increase splash lubrication of cyl walls.

 

Are you advocating increasing the revs soon after start-up, before the oil has a chance to reach the extremes such as the rocker shaft and tappets?

 

Even with a pre-heating system, I allow the engine to idle for five minutes giving more than adequate time for the oil to circulate. Only then do I introduce a load to help promote a quicker warm-up period. Also, I find the use of a secondary thermostat that interrupts the flow of coolant direct to the calorifier helps in this process too.

Edited March 7, 2013 by Doorman

[Doorman]

After all idling for an hour or more while in a lock queue is no different to idling for an hour at the bankside except the former sort of implies a degree of boating at a higher RPM before you got to the lock.

 

If we are at a lock queue for any length of time we turn the engine off. Mrs Doorman then has me bow haul the boat each time a gap appears in front of us. This means that the only risk of overheating is me!

 

Cheers Tony.

Edited March 7, 2013 by Doorman

[RickH]

Tony is of course quite right, you can't measure the charging current with a multimeter. But sometimes you can get an idea of the optimum speed by using a voltmeter. With a fairly low battery so that you are getting the maximum current from the alternator, gradually increase the rpm and you should see the battery volts steadily increasing. When a further increase in rpm produces no further increase in volts, that is about the best speed to run the engine.

I have a Lister SR3 , turns slow so I increase the revs to a comfortable level whilst chsrging until my clip on voltmeter ( I think 16 quid off Amazon ) reads around 14.3 , I can then step it down to tickover and it usually stay at 14.3 . 2 hours charging normally gets my 4 leisure and starter up to 12.7 off an 80amp alternator .