New Victron Multiplus install with Li Batteries

[scfoster]

Originally Posted by MerMike

Back to your AC diagram in Post 107.

What do the DC block capacitors do? I've not seen them used before.

Post 104 discusses this article that shows how to install capacitors for the RF grounding.


From the article: To avoid making another DC ground to the engine via the HF/SSB radio copper ground strip, fasten the copper tape securely to an insulating piece of phenolic or to a terminal strip, cut a 1/10" gap across the tape, and solder several 0.15 uF ceramic capacitors across the gap.

It looks like you have two small chargers running off the AC output of the Multiplus. I'll have to find the reference but I don't think that running an AC charger off an inverter is recommended. You can use the secondary DC output on the Multiplus to trickle charge the start battery. The windlass battery is going to need a DC-DC charger.

The AC used to drive those two chargers is a pass through while connected to shore power. No plans to run them while on the inverter, or the water heater.

The Windlass is using the Renogy 50A charger + MPPT (black box) upper right corner.

Yes there's a lot to take in. Next iteration would be to organize everything with the shape of the boat in the picture, to show the relative locations of everything.

Your ship's grounds need to connect to the ship side of the GI. It's a bit hard to tell from the diagram but the fused ground connection from the common post to the ELCI panel needs to be made on the ship side of the GI.

Not sure what "GI" means. Attached a diagram, hoping to provide a better view.

[scfoster]

Trying to figure out how to get the Victron Li-CT 120 battery combiner to work without the external BMS.



Doing some more research and came across this YouTube video. The blog is here.

https://www.youtube.com/watch?v=hKU437Xh5yo

The Li-CT 120 is used to combine the LiFePO4 house batteries with the AGM starter battery. What I did not know is that the BMV-712 can be used to manage the connection of the alternator to the LI house bank. At 17 minutes into the video, they describe how they do it, using the Low SOC (state of charge) relay feature.

Here is the BMV-712 Manual. Page 23 references the SOC relay.

The BMV-712 performs the function of an external BMS to shut off the combiner current to the house battery bank.

[Palarran]

Originally Posted by s/v Jedi

The bilge pumps are missing from the always-on bus bar.

I think this is modified from Victron? I think the Multiplus has two positive and two negative cables.

Jedi, would you mind explaining the "always on bus bar" for bilge pumps. Mine is wired after the main fuse and after the main disconnect.

[scfoster]

Originally Posted by Palarran

Jedi, would you mind explaining the "always on bus bar" for bilge pumps. Mine is wired after the main fuse and after the main disconnect.

Jeff Cote at Pacific Yacht Systems has some YouTube videos and posts (like this one) to explain how the Bilge pump should be 'unstitched'. Obviously it should still have a fuse but should never be switched off, hence the connection to the busbar without a switch.

[scfoster]

Ordered a Cyrix-LI-CT from PKYS.



The left pin on the bottom (labeled Start Assist 85) gets connected to the BMV-712 on the back of the display.

In the menu you go to Relay, leave the mode as Default, set 'Low SOC Relay' to 90% and 95%. This will ensure the LI house bank begins to charge below 90% and will shut off at a cushion of 95%. With a 170Amp alternator, should be able to supply the 120Amps continuous so could charge a depleted house bank in a couple of hours.

[rgleason]

I thought that Victron had disabled the 712 #11 relay functions. I seem to remember some disappointment about that, however it only uses voltage rather than voltage and current. I've had the impression that using the tail current is a better way to regulate charging LFP batteries.

[scfoster]

Originally Posted by rgleason

I thought that Victron had disabled the 712 #11 relay functions. I seem to remember some disappointment about that, however it only uses voltage rather than voltage and current. I've had the impression that using the tail current is a better way to regulate charging LFP batteries.

In combination with the shunt, supposedly it's quite accurate. If this works, I'll use the DC-DC chargers for the last 5%.
At least this way I can use 120A of charging from the alternator.

Lots of posts on van conversion forums about using the BMV-712 to do this, so clearly it now works.

[rgleason]

That is good news. It's probably good to have some reserve capacity, because overcharge kills lfp, however as you know, they also need to get top balanced regularly. Maybe you don't need 3 converters then?

[MerMike]

Originally Posted by scfoster

Not sure what "GI" means. Attached a diagram, hoping to provide a better view.

GI=Galvanic Isolator.

See the attached thumbnail for a suggestion on your ground wire connection.

[scfoster]

Originally Posted by MerMike

GI=Galvanic Isolator.

See the attached thumbnail for a suggestion on your ground wire connection.

Thanks.. need to check with the mfg as it's in their documentation. Not sure why they have it that way.

[scfoster]

Originally Posted by rgleason

Maybe you don't need 3 converters then?

Probably not. Will repurpose one of them to use with the Windlass/bow-thruster battery.

[MerMike]

Originally Posted by scfoster

Thanks.. need to check with the mfg as it's in their documentation. Not sure why they have it that way.

I would be interested to know if they recommend that configuration with a GI. It appears to create path to ground that does not go through it, negating the benefit.

update: Their wiring diagram clearly shows it, and a galvanic isolator, so it may not offer that path. Worth confirming though.

[scfoster]

Originally Posted by MerMike

GI=Galvanic Isolator.

See the attached thumbnail for a suggestion on your ground wire connection.

Called Blue Sea technical support. They said the wiring as shown in the diagram is correct. That fused green wire from the two sensor coils that goes around the top and connects to the Source side is part of the reverse polarity detection.

[scfoster]

Victron posted a YouTube Q&A on "Using and Alternator to charge Lithium".

One of the nuances as to why DC-DC chargers make sense, is they manage the voltage to House LI bank, while the alternator regulator is set to take care of the starter battery voltage.

They kept mentioning salesusacanada@victronenergy.com for questions about the products.

The comment was made that the Cyrix-LI-CT (from now on just "Cyrix") can be used to charge the LI House bank directly from the alternator, but there is no voltage management other that what the regulator puts out. So the regulator has to serve both house LI and starter batteries, with different voltage needs.

I can envision using both approaches, having a switch on the Cyrix to keep the relay open when charging from the DC-DC chargers. So for typical engine start with house bank under 80%, the Cyrix would be used to combine both batteries with the Alternator, supplying 120A to the LI house bank. Would monitor while motoring with the BMV-712 opening the relay at 95% LI house bank charge. Could use the DC-DC chargers (in parallel) to top off the LI house bank. Otherwise, for day to day trips from the slip (95% of the time) where everything is already charged, the Alternator would only be connected to to the starter battery (Cyrix relay open). Any charging of the LI house bank would be via the DC-DC chargers.

PKYS.com won't provide recommendations on a 'non-supported' configuration of the Cyrix with the BMV-712 (not that I blame him) but does think it might work. He did recommend using some form of insulation between the underside of the DC-DC chargers and the fiberglass or plywood to which they would be mounted.

DC-DC charger efficiency is about 87% with the 13% discharged as heat.

Here is a good article about the pros and cons of DC-DC chargers and the Cyrix combiner.

https://www.youtube.com/watch?v=dzU_pQFa19s&t=3256s

[JustMurph]

It sounds like a reasonable plan to me. I suppose the main thing that comes to mind is making sure that there's somewhere for all of that current to go when the Cyrix opens, so you don't end up with a voltage spike that will fry your alternators. I don't have much expereince with that issue myself, but it gets mentioned quite a bit with Li setups. With the Li bank at 95%, the voltage should still be low enough that the AGM start batteries will absorb most of that power....I think. Also having the DC-DC charger on just before the Cyrix disconnects may help.