Alternator vs Charger

[aread2]

I've got a Victron Multiplus. Any idea what might happen when I use it for charging alongside the domestic alternator?

 

As a gas-free boat we have a 5kVA Travelpower attached to the engine to run the cooker and the standard 120 A Beta Marine domestic alternator. To date the domestic alternator has been disconnected and the batteries only charged when the Travelpower was running. The instructions on the Travelpower say don't run it all the time when you are not using 240 volts. I'd like to use the domestic alternator for charging while cruising and shut the Travelpower down when not cooking, leaving the inverter on for non-cooking domestic 240v.

 

My concern is that the Victron and domestic alternator might confuse each other if they are both trying to charge the batteries at the same time when we are cooking for instance and there is 240v supply present for the Victron to use. Or will they just reach some kind of equilibrium and charge the batteries anyway? It's not such a great issue as the batteries should be mostly charged from daytime cruising with the Travelpower off but I was wondering why the domestic alternator was disabled.

[steelaway]

I've got a Victron Multiplus. Any idea what might happen when I use it for charging alongside the domestic alternator?

 

As a gas-free boat we have a 5kVA Travelpower attached to the engine to run the cooker and the standard 120 A Beta Marine domestic alternator. To date the domestic alternator has been disconnected and the batteries only charged when the Travelpower was running. The instructions on the Travelpower say don't run it all the time when you are not using 240 volts. I'd like to use the domestic alternator for charging while cruising and shut the Travelpower down when not cooking, leaving the inverter on for non-cooking domestic 240v.

 

My concern is that the Victron and domestic alternator might confuse each other if they are both trying to charge the batteries at the same time when we are cooking for instance and there is 240v supply present for the Victron to use. Or will they just reach some kind of equilibrium and charge the batteries anyway? It's not such a great issue as the batteries should be mostly charged from daytime cruising with the Travelpower off but I was wondering why the domestic alternator was disabled.

 

 

Hi

 

How long have been running like this?

Has the alternator benn disconected from new?

 

Alex

[ditchcrawler]

I've got a Victron Multiplus. Any idea what might happen when I use it for charging alongside the domestic alternator?

 

As a gas-free boat we have a 5kVA Travelpower attached to the engine to run the cooker and the standard 120 A Beta Marine domestic alternator. To date the domestic alternator has been disconnected and the batteries only charged when the Travelpower was running. The instructions on the Travelpower say don't run it all the time when you are not using 240 volts. I'd like to use the domestic alternator for charging while cruising and shut the Travelpower down when not cooking, leaving the inverter on for non-cooking domestic 240v.

 

My concern is that the Victron and domestic alternator might confuse each other if they are both trying to charge the batteries at the same time when we are cooking for instance and there is 240v supply present for the Victron to use. Or will they just reach some kind of equilibrium and charge the batteries anyway? It's not such a great issue as the batteries should be mostly charged from daytime cruising with the Travelpower off but I was wondering why the domestic alternator was disabled.

By "disconnected" do you mean electrically or mechanically

[aread2]

The alternator D+ terminal has been disconnected from new. The engine has done 180 hours. I came to suspect the alternator was not charging because the Travelpower shredded its drive belt (I'd failed to tighten it enough) and the batteries went flat.

[FORTUNATA]

Do you have battery sensing? This sounds a bit like trying to re-invent the wheel, i.e. complicate a basic electrical system. All that's needed is a functional alternator with battery sensing that will sense the charge at terminal level (of the battery) and adjust accordingly. You need some idea of how many amp hours you use and how much charge the alternator needs to provide. You can split the battery bank up and provide another alternator if necessary so you have 2 alternators on the go. Battery charging is a great idea if you sometimes couple the battery to a charger as the charger will use higher voltage periodically in cycles.

 

I've got a Victron Multiplus. Any idea what might happen when I use it for charging alongside the domestic alternator?

 

As a gas-free boat we have a 5kVA Travelpower attached to the engine to run the cooker and the standard 120 A Beta Marine domestic alternator. To date the domestic alternator has been disconnected and the batteries only charged when the Travelpower was running. The instructions on the Travelpower say don't run it all the time when you are not using 240 volts. I'd like to use the domestic alternator for charging while cruising and shut the Travelpower down when not cooking, leaving the inverter on for non-cooking domestic 240v.

 

My concern is that the Victron and domestic alternator might confuse each other if they are both trying to charge the batteries at the same time when we are cooking for instance and there is 240v supply present for the Victron to use. Or will they just reach some kind of equilibrium and charge the batteries anyway? It's not such a great issue as the batteries should be mostly charged from daytime cruising with the Travelpower off but I was wondering why the domestic alternator was disabled.

[aread2]

Do you have battery sensing? This sounds a bit like trying to re-invent the wheel, i.e. complicate a basic electrical system. All that's needed is a functional alternator with battery sensing that will sense the charge at terminal level (of the battery) and adjust accordingly. You need some idea of how many amp hours you use and how much charge the alternator needs to provide. You can split the battery bank up and provide another alternator if necessary so you have 2 alternators on the go. Battery charging is a great idea if you sometimes couple the battery to a charger as the charger will use higher voltage periodically in cycles.

There's quite sufficient charging capacity. I have a Victron multiplus (12/3000/120). The Travelpower feeds into the Victron and the boat's 240v ac system for cooking so the batteries are charged when we cook. There is also a domestic alternator that is disabled because tthe D+ (excitation) connection is isolated. The Travelpower should ideally not be run all the time so I was wondering if the alternator and Victron could work together when the Travelpower is switched on or if the domestic alternator should stay off-line permanently.

[Tony Brooks]

There's quite sufficient charging capacity. I have a Victron multiplus (12/3000/120). The Travelpower feeds into the Victron and the boat's 240v ac system for cooking so the batteries are charged when we cook. There is also a domestic alternator that is disabled because tthe D+ (excitation) connection is isolated. The Travelpower should ideally not be run all the time so I was wondering if the alternator and Victron could work together when the Travelpower is switched on or if the domestic alternator should stay off-line permanently.

 

You need Chris or Gibbo for a definitive answer but as I understand things both the Victron and the alternator measure the battery voltage (well the alternator probably measures the battery voltage via the charging lead and the Victron via its connecting lead). the battery voltage will be proportional to the battery's state of charge so the charging voltage will also have a relationship to the state of charge and thus battery voltage because of the internal "resistance" of the alternator and charger.

 

I would say it is all but impossible to have both pieces of equipment trying to regulate the voltage at exactly the same value and even if they were the time it takes either to "switch down" will be different so at the worst I think one of them may not produce any output (the one set to the lower charging voltage at that time). I suspect all this is likely to cause is the alternator warning lamp refusing to go out. I can see no way it is likely to cause any damage.

[steelaway]

There's quite sufficient charging capacity. I have a Victron multiplus (12/3000/120). The Travelpower feeds into the Victron and the boat's 240v ac system for cooking so the batteries are charged when we cook. There is also a domestic alternator that is disabled because tthe D+ (excitation) connection is isolated. The Travelpower should ideally not be run all the time so I was wondering if the alternator and Victron could work together when the Travelpower is switched on or if the domestic alternator should stay off-line permanently.

 

 

Hi there

 

IMHO

It seems a very odd way of charging your domestic batterys.

Can you not disconect the battery charging circiut and re-connect the alternator.

I'm sure you will gain a lot more charge per running hour - and when the travelpower is not switched on

 

Alex

[Gibbo]

Tony is close.

 

You will certainly not damage anything by having them both connected.

 

Most likely the worst thing that will happen is that the one with the lowest acceptance voltage will shut down. This won't happen until the acceptance cycle is reached so it won't increase charge times.

 

However........ Many modern mains chargers periodically pull a little trick to take a guesstimate at the state of charge of the batteries. If the Victron does that while the alternator is charging it may get confused and instantly go into float, or perhaps even shut down altogether.

 

But I repeat, it won't damage anything.

 

If your domestic alternator has simply had D+ disconnected then it most likely won't kick in under normal useage. But if you rev the eninge hard it probably will kick in and once it has done so it will continue to operate until the engine is next shut down. So you might actually find that it has been charging some of the time.

 

If it was my system I'd find a way to be able to control each system (ie switch on and off) independantly and then possibly automate it too so that the Travelpower does not fire up (but the normal alternator is used) unless you need the Travelpower for cooking, and when you fire up the Travelpower it shuts down the normal alternator.

 

But I like automatic things as I tend to forget otherwise.

 

Gibbo

[chris w]

I would agree with Gibbo's answer. Your disconnected D+ will only prevent your domestic alternator from working initially. Once you go past maybe as low as 1200rpm, the alternator will spring to life and, as Gibbo rightly says, it will stay functioning (even if you go back to idle and until you switch off the engine again). The D+ line gives the alternator its initial excitation current which kicks it into life. However, alternators tend to have some small amounts of residual magnetism and this will also excite them if you can get them spinning fast enough. Once excited, they stay excited

 

One question.... do you have a tacho? If you do, follow its lead back to see where it's connected. Most are connected to the normal alternator. Even if the domestic alternator is working and the tacho is connected to it, the tacho may still read nothing if the domestic alternator's output is less than the charger's output.

 

Chris

Edited December 22, 2008 by chris w

[Nickhlx]

One question.... do you have a tacho? If you do, follow its lead back to see where it's connected. Most are connected to the normal alternator. Even if the domestic alternator is working and the tacho is connected to it, the tacho may still read nothing if the domestic alternator's output is less than the charger's output.

 

Chris

 

 

How does an alternator give an accurate indication of engine revs ? Presumably there is a tap off at some point which is (a.c.) frequency dependant, but assuming the same alternator is geared up differently on different engines, is there some "calibration" to be done ? If so, how do you know what the revs are when you are calibrating

 

Nick

[chris w]

How does an alternator give an accurate indication of engine revs ? Presumably there is a tap off at some point which is (a.c.) frequency dependant, but assuming the same alternator is geared up differently on different engines, is there some "calibration" to be done ? If so, how do you know what the revs are when you are calibrating

 

Nick

The tacho tap is taken from one of the stator coils and outputs a pulsating positive-going DC signal. But you are quite correct, the tacho will definitely need calibrating by knowing the pulley ratio and the number of poles or the actual revs as taken from a hand-held meter. On my tacho, it can be set electronically by inputting the number of pulses per revolution. Of course, one needs to experiment with different numbers as you won't know the pulley ratio absolutely exactly.

 

The best method, if you have access to a hand-held tacho (or a bicycle computer), is to measure the actual engine revs and adjust the tacho directly to read the same figure. My tacho has this facility, whereby the needle can be moved (by button press) to correspond to the required reading. Some tachos have lots of adjustment and some don't, but either way you either need to know the pulley ratio and the number of pulses per second or (best of all) the actual rpm from a hand-held tacho. To know the number of pulses per revolution also requires you to know how many poles the alternator has.

 

The calculation of pulses per revolution is simply the (no. of poles) x (the pulley ratio) so, in my case, this is 6 poles x 1.8 pulley ratio = 10.8 pulses per revolution. Of course the 1.8:1 ratio won't be exactly right as the pulleys were measured with a ruler and its difficult to know exactly where the belt bites. To ascertain the number of poles, without dismantling the alternator, see if you can get a black felt tip pen dot on to one of the poles as you view through the rear of the alternator. Rotate the alternator and count the poles until you are back with your original pole.

 

I fitted a bicycle computer to monitor my crank pulley (in order to get a direct reading of revs) and I discovered my tacho was reading almost 200rpm too low. I was able to adjust the tacho by its electronic adjustment button to correspond exactly. So even from new, the tacho had not been adjusted properly; I always wondered why the top revs were not as per the manual - now i know why!

 

The bike computer is definitely the easiest way of calibrating the tacho. Just set the "wheel circumference" to 1667mm and the speed readout to km/hr. The reading you obtain from the flywheel (I glued the magnet to the flywheel) will be exactly rpm if you multiply the km/hr reading x 10. So if the display states 108.3km/hr, the engine is running at 1083 rpm. You also now have a second tacho down in the engine bay for when you are tinkering.

 

In case it's helpful, here are the calibrating instructions for my tacho: click here

 

Chris

Edited December 22, 2008 by chris w

[Keeping Up]

If your ignition charge light is staying on, then the alternator is not giving out a charge. If it is OFF then the alternator is indeed working Try revving up and see if the light goes from ON to OFF.

How would the light come on if D+ is disconnected?

[Canalwatcher]

Our boat has a travelpower a Victron 1200 multi and a 80 A domestic alternator we have done 400 engine hours.

 

For most of this time when cruising we have the travel power on with the victron switched to "charge" only. The fridge is 240v and this is always on. When we stop we switch from Victron "charge only" to Victron "Inverter". The Smartgauge fitted invariably show 100% charged at the end of a days cruise. The domestic alternator is also connected and seems to work fine either with or without the travelpower being on. The Smartgauge shows the engine with alternator alone also charges the domestic batteries

 

My feeling is that by using the travel power with the Victron on charge only the batteries charge back to full capacity more quickly than if relying on the domestic alternator alone

 

The boat is an Aqualine and may have a switching circuit to cope with these combinations. No damage anyway

 

Mick

Edited December 22, 2008 by zodiak

[chris w]

How would the light come on if D+ is disconnected?

Doh I am definitely still suffering from flu!!

[Mick_B]

I would agree with Gibbo's answer. ......<snip>.... , as Gibbo rightly says, .....snip>

Chris

'ere Chris!!!! Ye can't be doin that... De ye think it's Christmas or what???

 

Dammit man... stand up and fight..

[Ernie]

I have a 3Kw Travel Power and two Sterling Pro Digital chargers, a 50Amp and a 30Amp.

 

When the engine is running, I always turn the Travel Power on along with the 50Amp charger. If the batteries are a bit on the low side, I will turn on the 30Amp charger as well. The engine is fitted with a 120Amp alternator permanently connected to the 660Ahr battery bank.

 

I phoned dear Mr Charles Sterling, such a lovely chap to talk to on the phone, about my charging arrangement and he confirmed that it was all OK and was the best way to get the batteries back up (I never let them drop below 65% if I can help it). When the batteries are low, I often see a charge current of 120 Amps or more (for a short while) with both chargers on. With just the alternator, I see around 50 Amps.

 

I do have a problem though in so much as my alternator only seems to charge to around 13.8V ( it’s a Prestolite and is only 2 years old). The best I ever see from the alternator, at any revs, is around 50Amps.

[chris w]

I have a 3Kw Travel Power and two Sterling Pro Digital chargers, a 50Amp and a 30Amp.

 

When the engine is running, I always turn the Travel Power on along with the 50Amp charger. If the batteries are a bit on the low side, I will turn on the 30Amp charger as well. The engine is fitted with a 120Amp alternator permanently connected to the 660Ahr battery bank.

 

I phoned dear Mr Charles Sterling, such a lovely chap to talk to on the phone, about my charging arrangement and he confirmed that it was all OK and was the best way to get the batteries back up (I never let them drop below 65% if I can help it). When the batteries are low, I often see a charge current of 120 Amps or more (for a short while) with both chargers on. With just the alternator, I see around 50 Amps.

 

I do have a problem though in so much as my alternator only seems to charge to around 13.8V ( it’s a Prestolite and is only 2 years old). The best I ever see from the alternator, at any revs, is around 50Amps.

Yes, the voltage is too low, it should be up at 14.8v if you have wet cells or 14.4v otherwise. An easy way to fix it would be to fit an alternator controller to it. At 14.8v you should expect around 75-80 amps from your nomimal 120A alternator (assuming you have a typical 2:1 pulley ratio). The other option is to buy a new regulator from Ebay (less than £10). The Prestolite is usually just a Lucas A127 lookalike. The new regulator won't be ideal though as it will be set at around 14.2v; the controller though more expensive is definitely the way to go.

 

Chris

Edited December 22, 2008 by chris w

[Eeyore]

Yes, the voltage is too low, it should be up at 14.8v if you have wet cells or 14.4v otherwise. An easy way to fix it would be to fit an alternator controller to it. At 14.8v you should expect around 75-80 amps from your nomimal 120A alternator (assuming you have a typical 2:1 pulley ratio). The other option is to buy a new regulator from Ebay (less than £10). The Prestolite is usually just a Lucas A127 lookalike. The new regulator won't be ideal though as it will be set at around 14.2v; the controller though more expensive is definitely the way to go.

 

Chris

There is a 14.8 volt regulator available for the Lucas A127 type alternator.

It is available from Holger Christiansen, and marketed under their Cargo brand. The part number is 230283.

Most alternator reconditioners will have a copy of their catalogue on the shelf; its on page 422 of part 2 (alternator components).

Steve

Edited December 22, 2008 by Eeyore

[chris w]

Yes, but at what price? I bet it'll be close to 50 quid and an alternator controller can be had for £100 with a load more features.

 

I recently bought a spare high current rectifier for my alternators to keep on the boat. It cost £15 off Ebay brand new; list was £57 + VAT.

 

Actually you could lift the voltage of your existing regulator by inserting a diode as per Gibbo's website. One diode will take it to around 14.4v.

 

Chris

Edited December 22, 2008 by chris w

[Eeyore]

Yes, but at what price? I bet it'll be close to 50 quid and an alternator controller can be had for £100 with a load more features.

Trade price £7.20 + vat, probably double that for retail?

I was suprised too!

Straight swop for standard item, no modification required.

Nice and simple (in a broad west country accent )

Steve

[ditchcrawler]

I would agree with Gibbo's answer. Your disconnected D+ will only prevent your domestic alternator from working initially. Once you go past maybe as low as 1200rpm, the alternator will spring to life and, as Gibbo rightly says, it will stay functioning (even if you go back to idle and until you switch off the engine again). The D+ line gives the alternator its initial excitation current which kicks it into life. However, alternators tend to have some small amounts of residual magnetism and this will also excite them if you can get them spinning fast enough. Once excited, they stay excited

 

One question.... do you have a tacho? If you do, follow its lead back to see where it's connected. Most are connected to the normal alternator. Even if the domestic alternator is working and the tacho is connected to it, the tacho may still read nothing if the domestic alternator's output is less than the charger's output.

 

Chris

My domestics are 24 volt and I never did connect the D+, when the engine gets to about 600 rpm away it goes, no light, no switch, no relay.

[chris w]

My domestics are 24 volt and I never did connect the D+, when the engine gets to about 600 rpm away it goes, no light, no switch, no relay.

I can't understand why you would not want to connect the D+ wire? There is no advantage in self-excitement ( ); the disadvanatge is that you have no charge light indicator. Since it self-excites at 600rpm, I presume you have a 3:1 pulley ratio at least?

 

Chris

Edited December 22, 2008 by chris w

[aread2]

Thanks all. I'm definitely going to reconnect the D+ cable. This explains something I observed when the Travelpower was out of action. I increased the engine revs that evening while the cooker was on and the load was apparent in the engine note when the oven switched in and out as the domestic alternator was put under load. The day after SWMBO was single-handing and the batteries went flat. My guess is that the revs never got high enough for auto-excitation during a day's leisurely cruising.

[ditchcrawler]

I can't understand why you would not want to connect the D+ wire? There is no advantage in self-excitement ( ); the disadvanatge is that you have no charge light indicator. Since it self-excites at 600rpm, I presume you have a 3:1 pulley ratio at least?

 

Chris

The main reason was to save having a warning/charge light that needed disconecting when the engine stopped. I have seen them switched by using contacts split charge relays on the engine battery. and slave relays on the "Ignition" switch. but mines run happily without the D+ and I know if its charging by the volts/amps.

Pulley ratio if I remember is about 5:1