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Victron combi versus Separates


Dr Bob

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I am after some advice on Combi inverter/chargers vs having separate units.

Our boat is 15 years old and has a Victron combi (pic below). There are no invoices for the unit so I suspect that it was installed when the boat was new – although you may know better. On our old lumpy water boat we had a 240V supply via shore power with a battery charger and a separate small inverter. I found this system very 'controllable'.

With the Victon, I can see the benefit of having something that seamlessly switches between shore power and then going to the inverter if the shore power is lost, but that seems to be at the expense of a degree of controllability. For a while now, I have been thinking of swapping it out before it fails (15 years?) - I dont like the fact that all our 240v electrics are governed by this box and if it fails we are stuck until it is replaced/fixed. In the last few weeks however, a couple of things hit me that I dont like.

Firstly, When shore power is connected, the battery charger is always on. When coming into the marina with a 20% depleted battery, the victron gives an adsorption charge for a while but seems to switch to float at maybe 95% SoC (based on tail current). I then need to switch off the unit and on again to get it to do a bit more work – and maybe repeat this a few times. Each time I do this the TV/Rasp pie/ internet router go off. If I could control the battery charger independently it would be much better – and is there a battery charger that doesnt go into float too soon? This is only a winter problem as the solar sorts out the charge in the summer.

Secondly, we have just been off the boat for seven day (during the freeze and snow) and got back today to find the lecky to the 240v sockets off. No lights on the combi which was in the 'battery charger only' position – but 240v should still be on. I turned the combi switch to 'off' and then 'battery charger only' and the lights came on and the power was restored. The oil filled rads have therefore not been on for a few days – there have been big probs in the marina with the electrics and they have been rationing it – 6 hours at a time to the two sides of the marina – so that must have confused the combi. Again this is a 'winter only' problem.

I was therefore thinking of getting shut of the combi and replacing with a separate battery charger and inverter. A bright idea from a contact has suggested re-wiring to have a 240v supply to the boat via the switch panel and RCD etc and buy a battery charger to go on, and then use the existing combi as an inverter only to feed into the 240V system – which would be a much cheaper solution.

For 6 months of the year, we will be CCing so no shore power but the other 6 months we are on the boat 75% of the time and in and out of the marina – although in Dec/Jan likely in more that out.

What comments can you all offer?

IMAG0499.jpg

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There is a setting on modern Victrons to set when it should switch to float. Don’t know if yours has that. RTFM? 

Having said that if you’re remaining in the marina for a few days then float will eventually get the batteries up to 100% anyway. 

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I've just done this very thing. My Mastervolt Combi has an AC transfer switch fault so it has stopped recognising the AC supply to do the clever switching thing and I didn't want to wait the several weeks it could be in Mastervolt fixed price repair loop.

Rather than go direct replacement, I've fitted a Victron Inverter and a separate Victron charger. I've used a (1-0-2) 3 position switch to change between shore supply when at a berth with 240v supply of and the inverter when out cruising. I figured I didn't need the power assist or short break UPS features, neither of which I'd used in 4 years. I've made sure the shore supply only stuff (immersion and charger) are on their own breaker and have neon indicators to highlight when they're on. Happy to provide more info if any of this sounds helpful to you. 

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If you are at all savvy, then separates are better.  My brother's Mastervolt combi failed and he could not get power to the 240 sockets when he was on shore power - infuriating.  He had to run an extension lead in from the shore terminal, just to power his phone and laptop.  These combis are very clever, but if you know your boat's electrical system reasonably well, you don't need all the clever features.

If the shore power goes off, I don't want a 'bumpless' transfer to 'inverter mode' as the batteries will discharge and I will not realise until they are heavily discharged.  Victron and Mastervolt are competing for the yachty market.  Sterling are in the 'KISS' market.

Edited by mross
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45 minutes ago, WotEver said:

There is a setting on modern Victrons to set when it should switch to float. Don’t know if yours has that. RTFM? 

Having said that if you’re remaining in the marina for a few days then float will eventually get the batteries up to 100% anyway. 

I looked through the manual a month ago but didnt see the stuff on setting WHEN it goes to float. There was all the stuff about how to set the different voltages - but that didnt look easy.

When on float it is around 13.2V but hardly any current - protecting the batteries - so not sure how long it takes to get to fully charged. Last week I monitored the Amps out and amps in on a 3 day out tirp and we were 50Ahrs short of what went out when we got back in (660ahr bank) - and in the next 2 days on shore power we only got +10Ahrs in with the Amps at less than 0.5A all the time, hence the need to force the combi to go back to Absorption mode.

45 minutes ago, Sea Dog said:

 I figured I didn't need the power assist or short break UPS features, neither of which I'd used in 4 years. I've made sure the shore supply only stuff (immersion and charger) are on their own breaker and have neon indicators to highlight when they're on. Happy to provide more info if any of this sounds helpful to you. 

Yes, that's exactly what I was thinking. I will likely get a professional to come and fit it all but will get back to you if I try and do this myself.

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29 minutes ago, mross said:

If you are at all savvy, then separates are better.  My brother's Mastervolt combi failed and he could not get power to the 240 sockets when he was onshore power - infuriating.  He had to run an extension lead in from the shore terminal, just to power his phone and laptop.  These combis are very clever, but if you know your boat's electrical system reasonably well, you don't need all the clever features.

If the shore power goes off, I don't want a 'bumpless' transfer to 'inverter mode' as the batteries will discharge and I will not realise until they are heavily discharged.  Victron and Mastervolt are competing for the yachty market.  Sterling are in the 'KISS' market.

Yes, thanks for that. It mirrors what I was thinking. When the combi fails you get no power at all and have to use an extension lead until sorted and I dont want the combi switching to inverter without me getting invovled otherwise the batteries could go flat.

So, it looks like everyone likes the ideas of separates better, - what are the best battery chargers to go for given I am on cheapo lead acids at the moment but may switch next time to AGMs (so easy to change charging voltages) and i want to be able to control better when it switches to float.

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9 minutes ago, Dr Bob said:

When on float it is around 13.2V

Well, that definitely wants upping :)  

If you raise it to about 13.6V it’ll be a much more useful float voltage. 

Getting back to when it switches, does the manual say anything about “when the charge current reduces to x Amps...”. If so, can x be changed?

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If the transfer switch on the Victron fails it is an easy job to remove the cover and connect the mains input to mains output to continue supplying mains to your sockets via the shoreline. 

In its default setting the Victron dies switch to float before the batteries are fully charged. On our setup with a built-in generator I have it set to 'no battery type, fixed charge curve' so it won't go to float until the tail current is minimal. If on a shoreline for any length of time I switch it back to 'Adaptive Charging, battery safe'. 

Edited by pearley
Edited to add that it's easy with the VE Net interface.
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9 minutes ago, Dr Bob said:

Yes, thanks for that. It mirrors what I was thinking. When the combi fails you get no power at all and have to use an extension lead until sorted and I dont want the combi switching to inverter without me getting invovled otherwise the batteries could go flat.

So, it looks like everyone likes the ideas of separates better, - what are the best battery chargers to go for given I am on cheapo lead acids at the moment but may switch next time to AGMs (so easy to change charging voltages) and i want to be able to control better when it switches to float.

Combis follow the modern day trend of making something appear better whilst in actual fact building in a weak point. I am at present stuck in a marina plugged in and yesterday I switched leccy kettle on ( only EVER used when on shoreline ) and noticed a slight dip in the cabin lights this does not normaly happen. I went to investigate and the missus had inadvertently( yes it WAS the missus ) flicked off the shoreline rcd thingy so inverter had seamlessly taken over. Had we been on proper shoreline only power this would immediately have become apparent, no big deal and easily rectified on seperates wheras I could have crucified my batteries because of the too clever and totally unnecessary combi trickery.

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5 minutes ago, mrsmelly said:

It is blatantly obvious that Nick must be away from his pooter as he would be all over this thread by now telling us how marvellous combis are :D come on Nick!! awaiting incoming :)

Yeah, but if Nicks combi packs up, he just get the Jeeves to swap it out for the spare:)

Edited by rusty69
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4 minutes ago, mross said:

I think a 13A plug, on a flying lead, with three sockets marked, 'generator', 'shoreline' and 'inverter' is hard to beat.  It is uber-reliable and immediately obvious where the juice is coming from, or not!  It avoids any risk of back feeding.

It will never catch on cos its too sensible.

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33 minutes ago, mrsmelly said:

Combis follow the modern day trend of making something appear better whilst in actual fact building in a weak point. I am at present stuck in a marina plugged in and yesterday I switched leccy kettle on ( only EVER used when on shoreline ) and noticed a slight dip in the cabin lights this does not normaly happen. I went to investigate and the missus had inadvertently( yes it WAS the missus ) flicked off the shoreline rcd thingy so inverter had seamlessly taken over. Had we been on proper shoreline only power this would immediately have become apparent, no big deal and easily rectified on seperates wheras I could have crucified my batteries because of the too clever and totally unnecessary combi trickery.

That is only because you don’t understand how to use the device.:P

When you plug in shore power, you should always switch the Combi to charger only to avoid just this sort of problem.

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7 minutes ago, nicknorman said:

That is only because you don’t understand how to use the device.:P

When you plug in shore power, you should always switch the Combi to charger only to avoid just this sort of problem.

Yaaaaaaaaaaaay :D nice to see ya Nick.

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30 minutes ago, mrsmelly said:

It is blatantly obvious that Nick must be away from his pooter as he would be all over this thread by now telling us how marvellous combis are :D come on Nick!! awaiting incoming :)

Err yes, yes obviously a Combi is better, I didn’t think I had to say it. AGAIN!

Automatic switching, power boost, seamless integration with the Travelpower etc etc.

There is an argument that if you lose one you lose both and some truth in that. But if you lose the charger, yes you have lost the inverter but that is only relevant when you have external power so just patch the input and output mains wires together to temporarily get mains into the boat. If you lose the inverter well you are not on shore power so you don’t need the charger, and you have the engine to temporarily charge the batteries whilst it’s getting mended. So it’s not a massive point.

Just break out another box of your candles.

Edited by nicknorman
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2 hours ago, Dr Bob said:

I am after some advice on Combi inverter/chargers vs having separate units.

I have the same unit (12/2000/120) and would recommend you keep.   I have done some additions that enables you to easily by pass the unit and disable high power items when the shore power cuts out.   The cost is fairly low especially if you have space in a consumer unit.  Basically you have a contactor that is switched on only when shore power is available, these contactor feeds the breakers for your high power items.  Shore power goes off which then switches the high power items off, inverter part keeps the parts you want running.   The bypass switch is basically a crossover switch switching from shore to inverter (you could get another contactor (cross over one) to do this automatically, so if the combi fails it bypasses the combi automatically, but I don’t like that idea.) The benefit of the contactor is that you still have the Victron adaptive charging based on loads, bypass switch is just there incase I need to bypass the Victron for any reason.  I also have a inbuild genny and use another contactor to switch between the genny and shore power.   This all fits in a consumer unit and your only talking tens of pounds to do.

Edited by Robbo
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1 minute ago, mross said:

When a modern, clever combi fails, you can lose the inverter, the pass through to the 240 sockets AND the battery charger, because the unit refuses to switch on.

Install a bypass switch so if it does fail you just flip the switch to directly power your 240v from shore.

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Fit a changeover switch 'cam switch' that allows you to switch the sockets between shoreline inlet and combi output.

Fit a small 10A or 20A charger to work in parallel with the combi charger (don't have it powered from the combi output obviously!)

Both will help to overcome various issues and failure modes mentioned here, and will still be of use if and when you decide to go to separates.

HTH....

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