Mixed charging - is it OK

Some alternators need to be revved up to get excited and then you can drop the engine rpms and the alternators stay the same.
 
jfm said:
Crikey Piers you need to fix that. Just get one or two bigger alternators. On my engines the original Cat alternators were de-specced and a pair of mastervolt 150amp (@24v) beasts were fitted. These run to 6000rpm so with a x3 pulley they give 80 amps @24v when main engines are idling. You need a double pulley because there is a lot of torque needed to drive them (4Kw each). http://www.mastervolt.com/products/alternators-24v/alpha-24-150-mb/
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* When a standard alternator is replaced with a higher output alternator, you must replace the charging circuit wiring with the proper gauge wire to handle the higher output, otherwise you can cause a fire.

You will find out @ P speed when the auto extinguishers go off in responce to frying the wires !

I would get a competent boat electrician to test your alternators , regulators (s), wiring and battery (s) bank charge holding ,1st and go from there .

Could be somthing simpe like your bats are not holding there charge -this needs eliminating first .
Then look at the conections -corossion free ,otherwise increase in resistance -all the Amps it chucks out -does not reach the bats
Then look at the alternator , belt tight ? Is it polished inside ? - , pully slipping etc --regulator - needs measuring @ D rpm and P rpm --the output .


But you could do some basic maths and try and work out the total consumption , remember the engine electronics needs juice to run too .
To see how far off or close you are to maxing out your alternators .
Use say guess 80 % alternator out put at P speed and say 50 % @ D or lower ? Or google the alternator for the exact numbers and find the pully ratios , if you really like maths .

What D speed rpm do you do 16 hrs at ?
Whats your P speed rpm and WOT rpm .
A I said in a previous post I see both mine "excite " from about 800 rpm and kick out the same V -26.5 all the way up .
My D speed is 825-850 rpm

So may be ask if you can change the regulators in yours so they kick in @ your D speed
 
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kashurst said:
It shouldn't matter at all. If you start the engines with the mains charger running, the charger will at first notice a big drop in battery voltage as the engine cranks and will try to compensate for that, the charger has a maximum output that will be carefully protected by the charger. It won't be able to keep up with cranking current draw, but will do it's best without damaging itself. (People do lots of stupid things like short circuit chargers etc and they are designed to withstand quite a bit of abuse, errors etc)

Once the engine is running and the alternators kick in, the charger will see a rise in battery voltage and go into trickle mode or similar.

If the charger is one of the new wizzy ones that periodically charges at a higher voltage than the alternator output, the alternators will reduce output as they will perceive a very well charged battery.

Once shore power is off normal alternator behaviour will resume.

I have been doing this for 18 years on 5 boats, don't worry about it. I doubt the blown genny is related to battery charging issues.
Boat manual may state don't do this, but that could be for a variety of other reasons.
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+2

we very often run the genny during navigation, for the dishwasher or washing machine or desalinator.
and leave them running for many hours...
Victron battery chargers / invertors parallel with the alternators, without any problem.
With good battery chargers (Victron or mastervolt) in parallel with engine alternators you can't overcharge your battery's !
I'm planning to add Solar panels with MPPT regulator also in parallel on the service batt's.

Piers,
on top of other alternator(s)
place "battery monitor" devices on your batt's
 
Portofino said:
When a standard alternator is replaced with a higher output alternator, you must replace the charging circuit wiring with the proper gauge wire to handle the higher output, otherwise you can cause a fire.
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Understood. I'm in touch with my electrics guru (Robin of RES, Guernsey).

Portofino said:
What D speed rpm do you do 16 hrs at? Whats your P speed rpm and WOT rpm.
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1150 / 1200 at D speed. (Play d'eau is SD). Increasing to 1400 and the alts cut in fine but the extra power only adds half a kt. Just not comfy doing this. Doesn't 'feel' right. WOT is 2,600 which gives 17 kts.
 
1150 / 1200 at D speed. (Play d'eau is SD). Increasing to 1400 and the alts cut in fine but the extra power only adds half a kt. Just not comfy doing this. Doesn't 'feel' right. WOT is 2,600 which gives 17 kts.[/QUOTE]

So if it's poss to change regulator (s) or pulleys /belts - in which case not by much so they cut in at say 1000 rpm -you are sorted :encouragement:
Not suggesting move up out of sweet spot ,evey boat has a sweet spot (s) alts need reconfiguring to cut in just below ideally .
Read somewhere ,there are some Carlos Fandango -fancy regulators out there ,whereby you can adjust ,cut in and output level --set them up as suits .

That would be the easiest fix assuming everything else is working as it should .
 
Piers, fixing your alternators so your batteries charge better, while good for you, doesn't answer your original question, and I for one would like to know. Running a generator while underway is the only way to get 230v power if you don't have an inverter. Equipment like the fridge know when to switch, so do the battery chargers know or can the batteries accept two sources of charge, someone?
 
Bouba said:
Piers, fixing your alternators so your batteries charge better, while good for you, doesn't answer your original question, and I for one would like to know. Running a generator while underway is the only way to get 230v power if you don't have an inverter. Equipment like the fridge know when to switch, so do the battery chargers know or can the batteries accept two sources of charge, someone?
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Hi Bouba. Underway, I use an inverter which powers the fridge and kettle and any small mains power device. But it's not intelligent and is manually either on or off. It can provide 2.5kW (set to max at 2kW) which takes, of course, power from the batts.

So, the batts power everything whilst underway, whilst the alts try to charge them, yet their ability is strangled by the speed at which I cruise. Using a higher rpm takes me from a comfy D speed to a less comfy cruise. Hence, I asked the qn whether it was OK to run a genny and use the batt charger in parallel with the alts. The parish has answered, yes.

As a permanent solution, I prefer the idea of alts which can provide more oomph at a lesser rpm. Exactly what's needed. Whether this is achieved by a smaller alt pulley size (careful of too high an alt rpm at WOT) or more powerful alts (such as the Mastervolt jfm recommended) depends on whether the existing alts can provide the reqd oomph with a smaller pulley size.

Some calcs and tests should show this.
 
Piers said:
it's not intelligent and is manually either on or off. It can provide 2.5kW (set to max at 2kW) which takes, of course, power from the batts.
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Piers, all the inverters I've seen are either on or off (including my Victron Multiplus 24/3000), but this doesn't mean that they are constantly generating their rated AC current, drawing the required DC from the batteries.
When the fridges are in standby and there's nothing else demanding AC, they are bound to self-limit their output somehow, otherwise where would that generated AC current go...? :)
Not sure about how their internal electronic works, but I really can't see how ANY inverter could constantly create 2kW (or whatever) of AC drawing current from the batteries, whenever there's nowhere for the AC to be used.
 
MapisM said:
Piers, all the inverters I've seen are either on or off (including my Victron Multiplus 24/3000), but this doesn't mean that they are constantly generating their rated AC current, drawing the required DC from the batteries.
When the fridges are in standby and there's nothing else demanding AC, they are bound to self-limit their output somehow, otherwise where would that generated AC current go...? :)
Not sure about how their internal electronic works, but I really can't see how ANY inverter could constantly create 2kW (or whatever) of AC drawing current from the batteries, whenever there's nowhere for the AC to be used.
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Hi MapisM. Apologies for not making myself clear. I understand the inverter only takes what it needs to provide the reqd output. By saying not intelligent, I meant Play d'eau doesn't have a load demand system which looks at total load and activates the inverter/generators/whatever according to demand without manual intervention.

Does this make it clearer?
 
Piers said:
.... By saying not intelligent, I meant Play d'eau doesn't have a load demand system which looks at total load and activates the inverter/generators/whatever according to demand without manual intervention.
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this is more or less what a battery monitor device (Like Victron BMS700) can do for you,
actually it integrates all currents that go in and out a battery bank, (and shows ao the charge status on the display)
then you can set a alarm or a relay to activate the genny, when the battery charge is below xx % (I've set that at 60%)

the batt monitor also looks at battery voltage, (also visible on the display...)
depending on a situation, it can be that voltage drops below say 24V while battery charge status is still above 60%...
this can happen when the battery's are older, (higher internal resistance) and big current draw.
 
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