Charging batteries by idling engine

[DeepFrz]

Diesels like to run at close to max power, so that is a minor concern (i.e. if you idle often, and do not run the engine at max rpm frequently, carbon will build up).

New diesels are much less prone to carbon up at lower loads as the fuel is metered much more efficiently. So long as the oil reaches safe operating temperature the engine should be fine running at lower loads. The need to apply max load to a modern engine no longer applies.

[Nicholson58]

Originally Posted by sailorboy1

Of course to be able to do this you need to be able to measure amps via either a panel ampmeter of a battery monitor

YES

What charge controller do you have? Does it perform a correct charge sequence? We put a Balmar external regulator on each alternator.

[Steve O]

I have a Balmar external regulator. I ran the engine at 1300 rpms (5300 for alternator) for two hours and 14 volts. I got the following voltage readings after engine shut down

0 hours 13.14V running Refr
0.5 hrs 12.67v running Refr and 1 fan
1.0 hrs 12.59v running 12v TV, Laptop and Refr
1.5 hrs 12.51v running 12v TV, Laptop and Refr
2.0 hrs 12.49v running 12v TV, Laptop, 2 Leds and Refr
2.5 hrs 12.41v running 12v TV, 2 Leds and Refr
3.0 hrs 12.39v running refr, 2 Leds
3.5 hrs 12.43v running refr, 1 Led (anchor lt)
6.0 hrs 12.45v running refr, 1 Led (anchor lt)

Looking at this I am guessing my system is in reasonable shape.

[smac999]

idling the engine your 116a alt will probably put out about 15a you'll probably have to run it at 1500rpm to get any power.

[NYSail]

Don’t forget the balmar alternator are not so efficient UNLESS you program the bulk and absorption times and volts as per the specs of your battery. I bought my alt and regulator from Maine Sail and he walked me through the process.......

[Sailmonkey]

Originally Posted by smac999

idling the engine your 116a alt will probably put out about 15a you'll probably have to run it at 1500rpm to get any power.

Our 100 amp alternator will output 100 amps at just a hair over idle. But cooling sucks at this speed, so we run The engine faster to get the fans moving some air.

[john61ct]

Eco-Tech is a top notch specialty maker, designed for charging deep cycling banks, can run high output 24x7 at 1800 rpm.

Not good for your motor to do that just for power though, better to have a small pony engine or inverter genny for extended use.

[01kiwijohn]

Run the engine at about 1500 rpm, you'll pump more air through it, won't use any more fuel than idling, and it will minimize the tendency to accumulate carbon deposits.

[stormalong]

To charge your batteries properly you need a battery monitor to measure soc and charge rate. You also need a good external voltage regulator. Just running your engine without knowing how much power is going in and how much power you need is just a guessing game.

[Mike Banks]

If you do that you will be glazing the bore of your engine. Diesel engines need to WORK. Idling is not good for them. I bought a small Honda genset for just this purpose. It runs for eight hours approx on a tank full of petrol--runs fans and computers as well as lights and refrigerator and all while charging battery bank, (either through the DC 8 amp plug supplied, or via the 240 volts output through my usual battery charging system which puts out 15 amps and has spare power to run fans etc. It has helped me sit out two cyclones, been out in the rain at times, and never missed a beat.

I would have liked the larger 2kva model, but it is much heavier--and the baby one works OK. The larger one would allow me to use power tools--a big bonus, but weighs a lot more.

So--do not idle your diesel engine longer than is absolutely essential. The first sign of a glazed up bore is excessive use of oil. Once done, you will need a catalyst in the fuel and a long hard distance under load to remove it. My diesel was a Yanmar 3 YM 30--about as modern as one could get at the time--and I managed to glaze it up doing just as you are doing.

[rgleason]

Alternator Charging

I use reverse, on mooring or anchored (gets interesting!). I change rpm and rev up to 2800 every hour or so, for a short duration. 3YM30, old balmar, non oem stator, 1600 rpm to get 40a, with belt ratio of 1.73. Not a good setup. New Balmar 120a (maybe more amps) set on belt program, with serpentine will have 2.18 belt ratio, 850 eng rpm ---> 40-50a, 1000 eng rpm=80a. (New alternator needed in any case for bulk or lithium batteries.) Much better rpm for at anchor.

PS: Have two bilge fans (in and out), out directed at alternator. Yanmar guys drill holes in the belt cover or get rid of it, blocks air flow!

Battery Full Charge

However, full charge to (.02C).01C trailing amps measured by a good clamp meter is a real drag in any case, even with the Balmar regulator user programmed to match your manuf. specs for the FLA batteries! Hours and hours.

There is a better way to handle the FLA long charge tail: Shore charging (expensive), Lithium Batteries (expensive) & Solar (expensive), Efoy (expensive)

Or just accept the cost of new batteries every 3-4 years.

[wsmurdoch]

When I run my 100A alternator at its minimum speed to produce 100A into my three half discharged group 31 batteries, I have two problems. First, the alternator gets hot and the external regulator with its temperature sensor on the alternator cuts back the current to the field coil reducing the charge rate to 50A. That is because the alternator fans (both of them) turn too slowly to provide a full flow of cooling air over the hot diode pack, coils, and bearings. Second, I get belt dust. That is because with a constant alternator power load the tension in the tight side of the belt is greater at low speeds than at high speeds, and the belt slips just a little at low speeds wearing the single 1/2" vee belt. Speeding the engine up a little thankfully helps with both problems.

Bill

[cgebluewater]

Anytime I see mention of portable generator use on deck it is important to also mention the need for safety precautions. The fatalities from there use is under reported and very much under estimated by many. I know it has been mentioned on these forums many times but that message can never be mentioned to much. I was a part owner on a boat with a fatality so I learned a lot of information the hard way.


Thank you in advance for understanding my desire to help avoid this danger to those that may be unaware.

[rgleason]

Wsmurdock wrote:
When I run my 100A alternator at its minimum speed to produce 100A into my three half discharged group 31 batteries, I have two problems.
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Out of curiousity, what engine & hp, alternator manuf, and regulator, and what is the minimum rpm for 100a?
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Would some 3' dia vents with bilge fans in and out help?

[eyschulman]

Well I know a lot of people use their diesel drive engine to charge their banks under low load. I think that is wrong and would never buy a boat with such an abused engine. When one speaks of newer engines tolerating low-load that may apply to electronic common rail fuel injection not found on typical engines under 100HP or of older design with mechanical fuel pumps. My very modern fully electronic common rail engines even come with manufacturers advise don't idle more than necessary and warm them up under-way. Even small diesel gen sets are not meant to run at low loads. A common rail fully electronic engine can run a low load more like 30-70% without issue but that is not no load idle. The answer is a gen set. There are small diesel DC charging generators and I had one installed in my previous boat and it did a great job of keeping my banks in good shape.