Yet Another Lithium/Inverter Question

[AdrianChen]

I used https://offgridpower.solutions for my last bits nice chaps, and Funster discount!

Auto changeover is pretty quick in the Multiplus I have, but worth a chat with these guys about your particular needs I guess

 

[Lenny HB]

So, the question is: Where do the collective go for 12volt Victron equipment?

Won't you need 48v for home?
As AdrianChen says Off Grid are the people to go to, best prices on Victron and 10% Funster discount.

 

[AdrianChen]

Yes because when just the inverter is running you don't want the fridge/heater/charger connected to the inverter output. When the Multiplus has a mains input the inverter output and the incoming mains will be combined.

On some Multiplus and other combi types there is a second AC output - output one supplies the inverter only stuff, and the second can be set to output when EHU/Shorepower/Generator is available - guess it depends on any existing wiring as to which is the easiest way to install....

 

[LithiumConvert]

Won't you need 48v for home?

I does not have to be. I chose 12v for compatibility with the motorhome.

 

[Lenny HB]

I does not have to be. I chose 12v for compatibility with the motorhome.

Not bought the batteries for the home yet then?

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[Speve]

I have two consumer units working with our Multiplus and you can if you want put a separate wiring into the second consumer unit for EHU only appliances rather than going through the inverter.
We have been out now since last Wednesday without using any external hook up and our 300a Fogstar Drift pro has not gone below 80% even when using electric Kettle and microwave and although it’s rained virtually every day all day for five days we are still getting back up to full charge by the end of our daily travels. Well pleased with the system

 

[Wh05apk]

Yes because when just the inverter is running you don't want the fridge/heater/charger connected to the inverter output. When the Multiplus has a mains input the inverter output and the incoming mains will be combined.

I think that makes sense!

Thank you.

 

[LithiumConvert]

Not bought the batteries for the home yet then?

I have the same Sterling Power lithium batteries and charger as I have in the motorhome home. (but a different inverter *). and, as I said above, it is all working well with the Agile electricity account. My electricity bill is about half what it used to be.
* We do not use 240v in the MH except a small inverter to charge the laptop.

 

[EuroTrotters]

I Will have to get my old laptop out and check my Victron Inverter settings now, I cannot remember what I set them at.

I think it was standard LifePo default parameters

Who would have thought going lithium had to be some complicated

 

[LithiumConvert]

Who would have thought going lithium had to be so complicated

It is not really at that complicated once you have got the hang of the basics.

And some of us also do this to keep the brain cells working.

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[GrahamPye]

For lead-acid types, divide the Ah capacity by 5, ie C/5. So a 100Ah can use 20A, 200Ah 40A etc. For lithium, they can take much more, so it's a good idea to fit a high amps B2B. Usually the lithium limit is C/2, but some can take C, ie a 200Ah lithium may be able to take 200A. You also have to check that the alternator can supply that power, with all the other loads. Usually it's not a problem.

I asked the Fiat garage yesterday what the rating of my alternator was and they said it was 125A. Which sounds a lot to me, so I was slightly suspicious of the answer. However (see below) I'm currently looking at a 40A B2B, I think that should be enough vs the cost of a bigger one, and having to upgrade some hard to get at wires.

Looking at the internal diagram of the Reich EMB 41.74000, I can't see any need for any relays. Maybe they are disconnecting the fridge power from the EMB and sending it through a relay, to power it directly from the alternator/starter battery instead of through the EMB. Perhaps to make sure that the leisure battery gets the full B2B output, and doesn't share it with the fridge.

I think the other thing needed, not requiring a relay, is to disconnect the starter battery feed to the EMB, and send the B2B output directly to the leisure battery.

I've had a more careful study of the Pilote provided diagram, and the two relays are both energised by D+ the second one seems to only be there to energise the second one, which acts as a split-charge relay, disconnecting the B2B which seems overly complex. I'll post the diagram here if you're interested.

So.... I'm definitely settled on the Fogstar 230Ah (which OffGridPower are expecting any day) plus the Victron Smart 2000VA inverter. As above, I think a 40A B2B will be enough for now. I'm also going to rely on the existing mains charger even though it only charges at 16A, since if I'm on EHU I won't need to run the hairdryer off the battery!

To avoid any complications with the B2B, I'm simply (?) going to disconnect the vehicle battery from the Reich EMB completely and attach the cable to the B2B instead. I need to check that the existing cable is big enough for the B2B's load. Of course this means I will no longer keep the vehicle battery topped up from EHU or Solar when the van is not in use. Maybe this isn't that a big problem, and just adding a (relatively) cheap Battery Master would solve that. However a better solution seems to be to desert Victron (as their B2Bs will only put 1A into the vehicle battery) and choose a Sterling Power BB1240 B2B which will "reverse charge" the vehicle battery at up to 20A.

Thanks for any further comments! Graham

 

[autorouter]

I asked the Fiat garage yesterday what the rating of my alternator was and they said it was 125A. Which sounds a lot to me, so I was slightly suspicious of the answer. However (see below) I'm currently looking at a 40A B2B, I think that should be enough vs the cost of a bigger one, and having to upgrade some hard to get at wires.

125A is not particularly big. Many motorhomes have an uprated alternator, 160A or even 220A.

I've had a more careful study of the Pilote provided diagram, and the two relays are both energised by D+ the second one seems to only be there to energise the second one, which acts as a split-charge relay, disconnecting the B2B which seems overly complex. I'll post the diagram here if you're interested.

That's a common thing to do. The D+ is only a signal, so only intended to supply a fraction of an amp. If it triggers a relay, then that relay can supply whatever its rating is, with a suitable fuse direct from the battery. Used in a motorhome where there are several things that need to be triggered from the D+.

To avoid any complications with the B2B, I'm simply (?) going to disconnect the vehicle battery from the Reich EMB completely and attach the cable to the B2B instead. I need to check that the existing cable is big enough for the B2B's load.

I've not seen the B2B installation diagram, but from the EMB diagram I think that would be OK. The relay you mention is used generally in B2B installations to disconnect the starter battery from the EMB/split charge relay when the engine is running. It reconnects the starter battery to the EMB when the engine isn't running. However from the EMB diagram when the engine isn't running the starter battery connection is cut by the split charge relay anyway, so as you say there's no point in having the connection at all.

However a better solution seems to be to desert Victron (as their B2Bs will only put 1A into the vehicle battery) and choose a Sterling Power BB1240 B2B which will "reverse charge" the vehicle battery at up to 20A.

Usually 1A is plenty. When you park up, at a site or back home, you've just driven enough to fully charge the starter battery, so it's just a matter of not letting it slowly discharge to a low level. And if the parasitic drain is more thn 1A you have a serious problem. On a car it's less than 50mA, and a motorhome shouldn't be more than say 500mA.

 

[GrahamPye]

OK, you've convinced me about the B2B, your explanation of the normal sequence of events is bang on, I just thought I was missing something somewhere. So I wonder what is the scenario for the Sterling B2B needing to back charge 20A....
So, back to the Victron camp then. I think I'd like to get one of the new Orion XS 12/12-50 B2Bs although Roger and Nigel are not expecting to get them until the end of the month. I'll have to figure out what to do in the interim! If I can keep the battery charged from EHU, then there shouldn't be a problem with it trying to take too much power from the alternator.

Thanks, Graham