Why purchase a Travel Power Unit

[Nickhlx]

Thats interesting and does make an inverter system look more attractive.

Can it manage 175amps continuously or does this fall off significantly as the alternator gets hotter?

 

My biggest concern is having huge current going into the batteries when no mains is needed and trading this against enough to maintain a decent charge even if an immersion heater or other big load is on. It would not be too difficult to make a controller if there was a market for it.

Alternator 1 most charges batteries, Alternator provides power for the inverter when needed but is controlled to limit maximum current into batteries.

I think I would also want an alarm if the rate of current draw from the batteries was high for an extended period?

 

..........Dave

 

I think on our set up, the current diminishes within minutes because we rarely get much below 80% SoC after an overnight stop, and we only have around 480 Ah ( when new) so maybe only 400 Ah now, and whacking them with 175 Amps rapidly brings up the bank voltage, so reducing the charge current being produced by the alternator...rather than the alternator heating up - maybe its the batteries heating up !!

 

Nick

[nicknorman]

Thats interesting and does make an inverter system look more attractive.

Can it manage 175amps continuously or does this fall off significantly as the alternator gets hotter?

 

Well to be fair I haven't tried it (if you mean at idle) - I think that would be cruelty! We normally use the TP for continuous heavy loads. But whilst the output may fall off a bit as it gets hot, I think one only has to raise the revs to say 11 - 1200 (which I would want do anyway for the reasons Nick mentions). At those sort of revs it seems happy, but I haven't run it a very long time like that. It does get hot pretty quickly though, so I would have thought that any falloff would be noticed fairly easily

 

Even though the belt is a polyvee and tensioned correctly, it does sound in distress when running at idle with full load on the alternator. As the revs are increased, the torque required to drive the alternator and hence load on the belt decreases. So apart from anything else, I think prolonged running at idle will shorten belt life

 

My biggest concern is having huge current going into the batteries when no mains is needed and trading this against enough to maintain a decent charge even if an immersion heater or other big load is on. It would not be too difficult to make a controller if there was a market for it.

Alternator 1 most charges batteries, Alternator provides power for the inverter when needed but is controlled to limit maximum current into batteries.

I think I would also want an alarm if the rate of current draw from the batteries was high for an extended period?

 

..........Dave

We have 440AH (when new) and although 175A is a little high for the bank size, I am not convinced its a big deal. As Nick says, the current tends to fall off after 20 mins or so due to the batteries just not wanting to take that much current. Battery life would probably be prolonged a bit by charging more slowly, but if you look at the overall costs of engine running time and battery replacement costs I think I prefer the convenience of a fast charge.

Edited March 1, 2013 by nicknorman

[Bobbybass]

Please...forgive me for what I am about to say (as I am ignorant...and of poor and unsound mind)

 

Is there a problem here with this thread..that we are relating amps/watts at 12 volts with amps/watts at 240 volts ?

 

You see (by my reckoning...rough reckoning..)..I always calculate that when I run my inverter ...it demands 20 amps from the 12 volt...for every 1 amp at 240 volts...( that is rough..as there are inverter losses)

 

So..if you have a 175 amp alternator at 12 volts....if you are running the inverter for your 240 volts...then it will draw (roughly) 20 amps for every amp at 240 volt..

 

Therefore...alternator producing 175 amps/12 volt....divide that 175 amps by the 20 that it demands to produce 1 amp at 240 volts...175 divided by 20 is 8.75 amps...

 

So my reasoning is...(this is hypothetical )..that if you ran your engine...with your 175amp/ 12 volt alternator...and you had a 240 volt appliance that demanded 10 amps at 240 volts...you would exceed the alternator capability ( at full engine revs)..by about 30 amps...and therefore the alternator 'route' is not as a good as a Travelpower..which could easily produce the 10 amps without touching the batteries...

 

No ???

Edited March 1, 2013 by Bobbybass

[WotEver]

No ???

Yes

 

But the OP doesn't have any large power devices @ 240V so for him there's an argument against a TP (or at least not strongly for one).

 

Tony

[Bobbybass]

Yes

 

But the OP doesn't have any large power devices @ 240V so for him there's an argument against a TP (or at least not strongly for one).

 

Tony

 

OK..I bow to your superior knowledge..( Grovel grovel)

 

So I am right is my 'rough' calculations, that if you did have a washing machine or large power device, a large (say 175 amp) alternator, is no 'match' for a Travelpower ?

My calculation..that if you had 175/amp at 12 volt...and you used a washing machine at 13 amps....you could be hitting your batteries for ..maybe 80 amps above what the alternator could produce..?

Edited March 1, 2013 by Bobbybass

[nb Innisfree]

Please...forgive me for what I am about to say (as I am ignorant...and of poor and unsound mind)

 

Is there a problem here with this thread..that we are relating amps/watts at 12 volts with amps/watts at 240 volts ?

 

You see (by my reckoning...rough reckoning..)..I always calculate that when I run my inverter ...it demands 20 amps from the 12 volt...for every 1 amp at 240 volts...( that is rough..as there are inverter losses)

 

So..if you have a 175 amp alternator at 12 volts....if you are running the inverter for your 240 volts...then it will draw (roughly) 20 amps for every amp at 240 volt..

 

Therefore...alternator producing 175 amps/12 volt....divide that 175 amps by the 20 that it demands to produce 1 amp at 240 volts...175 divided by 20 is 8.75 amps...

 

So my reasoning is...(this is hypothetical )..that if you ran your engine...with your 175amp/ 12 volt alternator...and you had a 240 volt appliance that demanded 10 amps at 240 volts...you would exceed the alternator capability ( at full engine revs)..by about 30 amps...and therefore the alternator 'route' is not as a good as a Travelpower..which could easily produce the 10 amps without touching the batteries...

 

No ???

Our 24v 100 amp Leece Neville only just manages to keep ahead of our 2kw auto w/m when the heater is running. So 175 amp @12v is a bit on the lean side, 250 amp is more like it.

 

Don't rate polyvee belts myself, we have twin 13mm V belts, never slip or need adjusting.

[WotEver]

So I am right is my 'rough' calcualtions, that if you did have a washing machine or large power device, a large (say 175 amp) alternator, is no 'match' for a Travelpower ?

Yeah.

 

But...

 

A 2.5kW mains beast will be drawing approx 10A, which will be closer to 200A at 12V. Obviously that means that at least 25A will be pulled from the batteries. However, how long will that demand be in place? 15 minutes maybe? That's around 6.5Ah which the alternator can replenish PDQ.

 

Tony

[Bobbybass]

Yeah.

 

But...

 

A 2.5kW mains beast will be drawing approx 10A, which will be closer to 200A at 12V. Obviously that means that at least 25A will be pulled from the batteries. However, how long will that demand be in place? 15 minutes maybe? That's around 6.5Ah which the alternator can replenish PDQ.

 

Tony

 

OK..thats fine...I understand....

 

I did start my post by saying I was frail and of unsound mind...so I just wanted reassurance that the bats in the belfry...were at least flying in the same direction...

 

Cheers..

 

Bob

[dmr]

Please...forgive me for what I am about to say (as I am ignorant...and of poor and unsound mind)

 

Is there a problem here with this thread..that we are relating amps/watts at 12 volts with amps/watts at 240 volts ?

 

You see (by my reckoning...rough reckoning..)..I always calculate that when I run my inverter ...it demands 20 amps from the 12 volt...for every 1 amp at 240 volts...( that is rough..as there are inverter losses)

 

So..if you have a 175 amp alternator at 12 volts....if you are running the inverter for your 240 volts...then it will draw (roughly) 20 amps for every amp at 240 volt..

 

Therefore...alternator producing 175 amps/12 volt....divide that 175 amps by the 20 that it demands to produce 1 amp at 240 volts...175 divided by 20 is 8.75 amps...

 

So my reasoning is...(this is hypothetical )..that if you ran your engine...with your 175amp/ 12 volt alternator...and you had a 240 volt appliance that demanded 10 amps at 240 volts...you would exceed the alternator capability ( at full engine revs)..by about 30 amps...and therefore the alternator 'route' is not as a good as a Travelpower..which could easily produce the 10 amps without touching the batteries...

 

No ???

 

You are correct but I think a neater way to think about this is to use Watts; with mains equipment most things are specified by Watts rather than amps (think light bulbs, soldering irons, vacuum cleaners etc etc). The Watts is the same whether they are at 12v or 240v,

So a 2.5kW device is going to take 2500/12 = 208 amps at 12volts.

Also need to factor in that inverter systems are only 80 or 90 efficient, so a good rule of thumb (From Gibbo amongst others) is to divide by 10 rather than 12

2.5kW 2500/10 = 250 amps from the batteries!

 

............Dave

[Biggles]

Is there anything special about the TP alternator?

[dmr]

Is there anything special about the TP alternator?

 

Yes! Its a standard (Bosch?) alternator but rewound so that it produces 230volts (or thereabouts) directly, rather than 12.

This is much more efficient: more volts=less amps=less heat loss in the windings.

This allows a standard size alternator to produce 3500 watts without melting.

 

(the box then rectifies this AC to DC, and converts this to the 230v AC at 50Hz.)

 

..........Dave

[costalot]

-We have the Beta with 175A and 45A alternators, 480Ah of Trojans and the Victron 12/3000/120 combi, but it won't run the washing machine, even when not on the heating cycle - is this due to a "setting" being wrong then ?

 

( It powers the microwave and other high current devices with no problem - just the washing machine, and the alternator has been seen to deliver up to 200Amps for short periods in the morning, so the alternator is not really in doubt)

 

Nick

 

I suspect it's either your washing machine or your inverter configuration. We have the same setup as you and it's happily powering our washing machine without assistance from the domestic battery bank!

[costalot]

I think on our set up, the current diminishes within minutes because we rarely get much below 80% SoC after an overnight stop, and we only have around 480 Ah ( when new) so maybe only 400 Ah now, and whacking them with 175 Amps rapidly brings up the bank voltage, so reducing the charge current being produced by the alternator...rather than the alternator heating up - maybe its the batteries heating up !!

 

Nick

 

The way I look at it is our battery bank is 900Ah and we normally use less than 25% of it daily. Therefore the combined "bulk" stage of the daily re-charging from the combined alternator output (220A) doesn't take very long (less than 30 minutes). But I need to keep the engine running to reach 100% charge (Absorption stage) (another 2-3 hours)so the alternators are producing excess power I wouldn't normally use. However during this time I use the inverter to re-charge the batteries in all the 240V equipment (laptop, ipad, walkie talkies, etc). Also use the washing machine, vacuum cleaner, microwave, etc (obviously not simultaneously). Why waste the diesel?

[trackman]

Our silver box TP has been brilliant for over 6 years. As others have said it does all the heavy stuff like laundry for no extra diesel whilst we are cruising. It takes no real space and doesn't require petrol. The last is a big plus for me as I don't want the safety issues petrol involves.

If I had more room and unlimited cash I'd have a separate diesel generator because of the saving in wear on the main engine and the extra resilience of power supply that would offer.

[by'eck]

I have thought quite a bit bout about TravelPower vs Inverter.

On paper big alternators and a big inverter looks very attractive, and avoids the possible travelpower issue of reduced voltage at very low revs.

However when you start going into all the detail the TravelPower starts to looks more attractive.

Maybe we don't need 3.5kWatt but with start up surges etc lets say we need at least 2kW:.....

 

A 175 amp alternator, when hot and running at low engine speed, will get nowhere near 175 amps, maybe only half that.

(Travelpower is much more efficient and suffers less from heat)

So for 2KW peak we probably need getting on for 400amp of alternator!!!!!!

This is a big lump, and will need some thick wires plus all the connections maintained in perfect condition.

With a discharged battery and cold alternator, and a few engine revs, this huge current will all go into batteries which they might not like. It will also take a lot of power off the engine!

If you ever accidentally leave the immersion heater on without running the engine the batteries will be flat in no time, but if you work the inverter at full power the current available for battery charging will be minimal.

I think the TravelPower wins because it is a totally separate system, it is optimised to do just one thing and it does that really quite well.

 

I reckon a system with two big alternators, a big inverter, and a clever control system might just work. This controller would need to control both alternators and monitor battery current etc. I don't think such a thing exists yet???

Of course this whole scheme looks a lot better if you go for 24volts.

 

.............Dave

 

What you haven't factored in is that a decent sized battery bank will take up as much slack as is needed when running say a washing machine. You don't need to have the alternator(s) producing the full current draw of the inverter when running such.

 

The TP reigns supreme in terms of efficiency given its 250 volt alternator aided maybe by a higher mechanical gearing from the engine.

[dmr]

What you haven't factored in is that a decent sized battery bank will take up as much slack as is needed when running say a washing machine. You don't need to have the alternator(s) producing the full current draw of the inverter when running such.

 

The TP reigns supreme in terms of efficiency given its 250 volt alternator aided maybe by a higher mechanical gearing from the engine.

 

I had thought of that, I did say it but maybe rather indirectly: An inverter scheme overcomes the travelpower issue of limited power at low revs.

For me this would be the main advantage of an alternator system...none of that going into locks too fast because if you take the engine revs off the breadmaker makes a wet brick!!!!

However all the time the batteries are taking the slack, and when the inverter is stealing charging current, you are effectively increasing engine running hours (assuming you're not cruising of course). The advantage of TravelPower is that it makes 240v without compromising battery charging. However this is a bit pedantic because the cost of the TravelPower would buy enough diesel to charge batteries for quite some time!!!!

 

...........Dave

[Biggles]

Yes! Its a standard (Bosch?) alternator but rewound so that it produces 230volts (or thereabouts) directly, rather than 12.

This is much more efficient: more volts=less amps=less heat loss in the windings.

This allows a standard size alternator to produce 3500 watts without melting.

 

(the box then rectifies this AC to DC, and converts this to the 230v AC at 50Hz.)

 

..........Dave

 

 

Ah right. I had in my mind it was simply a 12v alternator feeding an inverter, a bit like the new range of inverter generators.

[Bobbybass]

Our silver box TP has been brilliant for over 6 years. As others have said it does all the heavy stuff like laundry for no extra diesel whilst we are cruising. It takes no real space and doesn't require petrol. The last is a big plus for me as I don't want the safety issues petrol involves.

If I had more room and unlimited cash I'd have a separate diesel generator because of the saving in wear on the main engine and the extra resilience of power supply that would offer.

Because I had to have new TP drive pulley made up from scratch (aircraft quality aluminium)...I designed in a 12 volt John Deer clutch...so my TP only rotates when I press a switch. This saves any wear...but it's not for the faint hearted...as I had to remount the TP (in a cradle) on a length of threaded bar to move it back (adjustable) by nearly 30mm...

Edited March 1, 2013 by Bobbybass

[bowten]

I have been singing the praises the T/P since I joined this forum.I wouldn't have anything else on any of my boats.No volatile liquids to spill or carry,no second engine to maintain,no loud generator outside on the banking,spending 600 to 800 quid every 2 years to buy another cheap gennie,will fit any space and when it's running it will power any thing yer throw at it and still charge yer batteries.If you are a live aboard or use your boat as intended it is something you should seriously consider.If you have a shiny boat in a marina and come out to play a couple of times a year spend your money on polish.I have said it before and I will say it again the boats main engine is an industrial unit and is built to last the rigours of slow running interspersed with full throttle usage and will do this for many hours.I have no commission coming by the way.

[mrsmelly]

I have been singing the praises the T/P since I joined this forum.I wouldn't have anything else on any of my boats.No volatile liquids to spill or carry,no second engine to maintain,no loud generator outside on the banking,spending 600 to 800 quid every 2 years to buy another cheap gennie,will fit any space and when it's running it will power any thing yer throw at it and still charge yer batteries.If you are a live aboard or use your boat as intended it is something you should seriously consider.If you have a shiny boat in a marina and come out to play a couple of times a year spend your money on polish.I have said it before and I will say it again the boats main engine is an industrial unit and is built to last the rigours of slow running interspersed with full throttle usage and will do this for many hours.I have no commission coming by the way.

 

Very well put. The tp for a liveaboard is simply the best way. Plenty of power for chores whilst cruising/charging and the full amount of leccy from the 12volt alternators charging the batteries at the same time from one unit. As for engine hours again spot on. One of our boats at work has well in excess of 30,000 hours on its two propulsion engines much of it at tickover, the engines ( Ford ) are still sweet as a nut.

 

Tim

[Dave_P]

We have a Beta 43 with 175A domestic alternator, the smaller engine one, and a TravelPower. There is not really an issue with the load being too heavy, although if you for example put the tumble drier on first thing in the morning after start, powered by TravelPower, whilst the 175A alternator is recharging the batteries at high current, the load is quite high and the engine likes to be 100rpm or so above tickover minimum, which can be a pain in locks etc. However, the solution is simply to avoid this scenario and not put heavy electrical loads on during the first 30-60 mins of battery charging, unless cruising and able to keep the revs a little above tickover.

 

Why have a TP? As you say, its not essential, but it provides a backup for 2 pieces of equipment: If the inverter fails, we have another source of AC power. If the 175A alternator fails, we have (through the Combi) the ability to still charge the batteries.

 

It also can supply a heavier load than a typical inverter. We have a Mastervolt 2500va Combi and a domestic vacuum cleaner. The startup surge from the vacuum is such that the inverter cuts out. But it works fine from the 3.5kva TP. We have a 2kw tumble drier. Whilst the inverter and 175A alternator could just about supply that, I am not convinced that the 175A alternator is very happy running at full load for a long time. We always use the TP for the tumble drier.

 

Just to mention that, whilst we have seamless operation of our TP with our Mastervolt Combi, there has been some discussion recently on this forum about people having difficulties with TP and a Victron. Personally I think its down to configuration of the Victron, but can't be certain. Others with a TP and Victron have absolutely no problems.

 

You could buy a generator for less than a TP, but the advantage of the TP is that it fits onto the engine without taking up any more space except for the electronics box, whereas a generator has to be stored somewhere and space is at a premium on most boats. It might also be tricky to use the generator whilst cruising to replace a failed alternator or inverter.

 

So its certainly a "nice to have" but whether you should get it depends on whether you can afford it. For us, in the context of a new boat build, it was a relatively small additional cost.

 

Arriving at the thread late but I have to say you've overlooked one important point. Yes, the travelpower provides a backup for the inverter and the alternator but where's the backup for your engine? Far more important in my opinion. With a stand-alone generator you aren't reliant on a functioning engine for your power. You can carry on living quite happily where you're moored until you get your engine fixed.

[nicknorman]

Arriving at the thread late but I have to say you've overlooked one important point. Yes, the travelpower provides a backup for the inverter and the alternator but where's the backup for your engine? Far more important in my opinion. With a stand-alone generator you aren't reliant on a functioning engine for your power. You can carry on living quite happily where you're moored until you get your engine fixed.

Yes that's quite true, however I suspect a modern jap engine has a longer MTBF than alternators and inverters. A separate generator is a good idea but requires space to store it and its a pain to use (have to get it out, refuel etc). A built in generator is better but again takes up fixed space. It's all a compromise!

[Dave_P]

I have been singing the praises the T/P since I joined this forum.I wouldn't have anything else on any of my boats.No volatile liquids to spill or carry,no second engine to maintain,no loud generator outside on the banking,spending 600 to 800 quid every 2 years to buy another cheap gennie,will fit any space and when it's running it will power any thing yer throw at it and still charge yer batteries.If you are a live aboard or use your boat as intended it is something you should seriously consider.If you have a shiny boat in a marina and come out to play a couple of times a year spend your money on polish.I have said it before and I will say it again the boats main engine is an industrial unit and is built to last the rigours of slow running interspersed with full throttle usage and will do this for many hours.I have no commission coming by the way.

 

Why on earth would someone spend £600-£800 every two years buying a new genny? Where are these genny's which cost that much (very expensive from where I'm sitting!) and yet suffer irreparable breakdown every two years? I certainly haven't come across them. I fact I've plenty of experience of genny's 30-40 years old, still running fine and only requiring occasional oil, plug and filter changes. Oh, and when I run my genny, there's less noise and vibration in my boat than when I run my engine. I don't even put it on the bank, it stay on my back deck.

 

There's nothing really wrong with a travelpower system but they have a major flaw in that they don't provide an alternative if your engine fails. The only really good argument I can see for them is space-saving. Having said that, my genny lives on my deck under a cover in a place which I wouldn't use for anything else. If someone offered me a travel power for around £100 I might take it as an extra option but that's all.

 

Yes that's quite true, however I suspect a modern jap engine has a longer MTBF than alternators and inverters. A separate generator is a good idea but requires space to store it and its a pain to use (have to get it out, refuel etc). A built in generator is better but again takes up fixed space. It's all a compromise!

 

I don't know what MTBF means but I get your point, I think. I'm not sure I agree with that though. An engine is dependant on lots of other systems / parts in order to work, e.g. fuel pump, cooling system, starter motor. A failure of any of these would mean that you couldn't get any power. Anyway, I don't have a modern jap engine, I'm not sure I want one coz they sound nasty to my ears.

 

I've mentioned the storage issue above. I don't have to get it out, it is out! I really don't feel like I'm compromising. The reality for me is that my genny has never failed me but my engine has always developed niggles and small faults which have prevented me from running it for certain periods.

 

For info, this is the same as my genny My link except I bought mine for less than this . Similar sorts of things come up on ebay all the time, often (as in my case) bought as a back-up in case of power failure and then never used. Why pay more?

[nicknorman]

Having said that, my genny lives on my deck under a cover in a place which I wouldn't use for anything else.

 

 

But that would be classed as deck clutter on our shiny boat - not allowed by HWMBO.

 

 

I don't know what MTBF means but I get your point, I think. I'm not sure I agree with that though. An engine is dependant on lots of other systems / parts in order to work, e.g. fuel pump, cooling system, starter motor. A failure of any of these would mean that you couldn't get any power. Anyway, I don't have a modern jap engine, I'm not sure I want one coz they sound nasty to my ears.

 

I've mentioned the storage issue above. I don't have to get it out, it is out! I really don't feel like I'm compromising. The reality for me is that my genny has never failed me but my engine has always developed niggles and small faults which have prevented me from running it for certain periods.

 

 

MTBF = mean time between failure - sorry, probably an aviation term. Your dislike of jap engines is your choice, but your experience of engine reliability a consequence!

 

We all have different priorities, for some the TP wins, for others it's a generator.

[Dave_P]

But that would be classed as deck clutter on our shiny boat - not allowed by HWMBO.

 

 

 

MTBF = mean time between failure - sorry, probably an aviation term. Your dislike of jap engines is your choice, but your experience of engine reliability a consequence!

 

We all have different priorities, for some the TP wins, for others it's a generator.

The engine's itself has been rock solid but in the last two years I've had to repair the starter motor, refurb the alternator and fix a leaking cooling pipe. None of these issues would have been prevented by having a japanese engine. Electrical/wiring faults are also a common cause of non-starting and are likely to be the caused by work done in uk boatyards. Again, the make of engine is largely irrelevant. I honestly can't say that friend's with Japanese engines in their boats have noticeably less problems than those with BMCs, Listers etc. Like I said, engine failure is just one of countless reasons for non-starting.