Stefanie avatar image

Battery Protect or Cyrix to control charger(s) in a LiFePO4 setup?

Currently I'm designing a new setup for my sailing yacht, switching from VRLA to Victron Smart LiFePO4.
System will look like this: 4x100Ah Victron Smart LiFePO4, Multiplus 12/3000, VE.Bus BMS, BMV, Cerbo GX and BP 12/220. See also attached system proposal.

There seem to be several options to control my charger(s) (SmartSolar 150/35 and SmartSolar 75/15 max. 600Wp PV and probably 2x Orion TR 12/30 in parallel, which will replace a Sterling alternator to battery charger, to save batteries in the event of low or high voltage / temperature. Since I want to keep the VE.Direct ports free to connect to the Cerbo, the option of using the VE.Direct non-inverting cable is not available.

Another option could be in using a smart battery protect and let the VE.Bus BMS do the job by "cutting" the line. And there are Cyrix with different options. Not sure if they are able to shut off the chargers in the event of LV or HV. And I'm probably not up to date with what Victron Connect or VE.Smart Network can do. Devs are very active and there are so many changes within the last couple of months.

So I'm asking for recommendations. Which way is the best to control my MPPT's and the Orion's?


MPPT - Solar Charge ControllerBattery ProtectLithium battery Smart
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JohnC avatar image

Hi @Stefanie. Random observations, incomplete, and maybe even irrelevant. See em as you will..

1/ A single Orion 12/12-30 might do. 2x could overwhelm your alt (even burn it out), and your start batt could be depleted. Use the 'ignition' function to turn it on.

2/ You could probably delete 2x Battery Protects. The one on your dc loads could stay.

3/ Your batt 'Main Switch' should be a total batt isolator, so I'd relocate it.

4/ Your GX Touch should make that DMC redundant.

5/ Consider using a Cyrix between the Starter and Thruster batts. When the engine is running that's most likely when you'll need it? More load on that alt.. But a bit of a backup for both batts.

6/ Isolators/fuses/breakers you may need to add in spots, but determine where you're going first.

Enough to discuss for now..

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Thank you @JohnC, much appreciate your input.

For 1) In that case I might opt for the VCC 12-50 (B2B). The old sterling AB1280 was able to pull out up to 40A from the alternator for years, but can't be configured properly for the Lithium setup. That's why I'm looking for something that comes close to the output.

For 2) So how to switch the MPPT's and B2B off in case of a high or low voltage event (not to forget about temperature), when I delete the two battery protect? I thought I could use them as a relay. That is the main question of my initial post.

For 3) The main switch in the diagram is already installed, but too weak to handle expected high currents from the Multi. I forgot to plot another into the drawing. But I get the point.

For 4) That is interesting. I've spoken to a Victron dealer at the Duesseldorf boat show. He told me that I still will need the DMC, even though I contradicted on my experience last year when I disconnected the DMC and controlled the Multi through the remote console within VC. That's why I put it in again.

For 5) The main reason for the separated thruster battery is this article by Matthijs. Currently the thruster is powered by my service battery bank. But according to the article that is not the recommended way in a lithium setup. I very rarely use the bow thruster and if, then only for a few seconds. But it's there, so it will be used. Wired by 8m (count that twice, then it's 16m) of 70mm2 wire. There is quite some voltage drop and that's why I thought it would be smart to put one of the older VRLA into the bow directly to the thruster. Cool, never thought of the Cyrix. That could do the trick.

6) Yes. The diagram is only a first draft to estimate what I need, what to order and what to drop. There is a lot of stuff installed already on the boat.

edit: I read through the VE.Bus BMS manual and discovered that the Orion has a remote on/off, which could be controlled by the BMS charge disconnect. Unfortunately both MPPT's don't have a physical remote on/off. So that requires either a VE.Direct non-inverting remote on/off cable or a BP to control them via the BMS. I'd opt for the BP then to keep the VE.Direct free for connection to the Cerbo. If I didn't read that wrong, it will answer my question.

"For 2) So how to switch the MPPT's and B2B off in case of a high or low voltage event (not to forget about temperature), when I delete the two battery protect? I thought I could use them as a relay. That is the main question of my initial post."

The battery protects can be used between MPPTs and the battery but there seems to be uncertainty if they are actually approved for this purpose due to reverse current. Victron have used them in this way them self though.

Have you investigated the BMS 12/200? I have no personal experience with it but it does looks to be the component that may be able to offer you a workable solution.

@Johannes Boonstra (Victron Energy Staff) replied to the above so if i tag him here he may see this and be able to offer some more details

Thanks for your input TTbb,

I wasn't aware of the other thread. I also read the manual for a BP and beside the mentioned paragraph 3 from the installation manual, further down there is the diagram with a 2nd BP used as a replacement for a Cyrix-Li charge.

So I assume that this could work for my installation without worrying about reverse current. See also revised pdf in my first post, which I just updated. It definitely should work with the 150/35. Not sure about the 75/15 because it has a load output.

"Figure 5: Second Battery Protect in between a battery charger or MPPT solar charge controller and a Li-ion battery

The second BP replaces a Cyrix-Li-charge relay (advantages: lower power consumption, alarm relay).
(not applicable if the charger has remote on-off contacts and can be controlled with an interface cable between the BMS and the charger)

Choose program for this application.

Caution: uncontrolled reverse current will flow through a Battery Protect if Vout > Vin. Therefore never use a Battery Protect for battery to battery charging."

I think you may be underestimating the value of the Cerbo in your system. And perhaps searching for unnecessary workarounds the Cerbo could already cover. My experience doesn't run to Victron smart batts or bms, but that'd be my priority. Call it a macro view.

To that end, I'd keep everything Victron, the aim being *total* monitoring and control by the Cerbo (or a lappy on your coffee table or beside your bunk).

I like how you've modified your plan (to a degree), but maybe now include the micro view. Ie. where all your VE.Direct and BT links might go.

I'm still wondering about the need for BP's at all. I'd expect a Smart batt bank could look after itself?

Yes. I'm still waiting for the manual of the Cerbo to be released. Until then I only have a vague idea of what else it is capable of compared to a CCGX/Venus GX.

Thought I had the VE.Direct links already in there. I have made it more clear now in an update. See new pdf. Most of the Victron devices are BT. Though not sure what extra value this is giving except for configuring and monitoring these devices.

Tomorrow I'll have phone call with my Victron dealer. Hopefully he's experienced enough to answer the question about need for BP's.
Yes, I would expect the same. It depends on how you define smart ;-)
Reality is that Victron Smart LiFePO4 have cell balancing and monitoring integrated, but then rely on the external BMS, which then is processing the information and controlling load and charge.

Yeh, I'm a bit old-school and expect to see wires. Maybe you could hang a BT symbol off each item on your plan with that intended connectivity? Might surprise..

Agreed that the bms should look after the batts, so then there's not much left (if anything) for the BT items to actually do directly. As it should be.. there, I dared say it.. :)

Your 70mm2 wires between the 2 aux batts is a head-scratcher. Theory sez it should be so with a 3kW thruster, but that's crazy stuff for something only running for a few seconds. Perhaps the cyrix should be turned off while the thruster is actually running?

You keep me busy thinking ;-) Just kidding. I know how important all this is . It's not just about money but safety.
See the updated schematics for BT connectivity.

Exactly, the bow thruster is causing me headache. Not happy with this at all. Simple solution could be to use the starter battery to power the bow thruster. Don't even need to change the existing wiring, except to put the positive wire to positive pole of the starter battery.

Gotcha thinking? Then I've succeeded, hey? Your money, and you've got to live with what you spend it on. :)

What your own experience may be missing is the GX world. It's a step-up from BT.

There's all sorts of little things that may impinge your decisions. And they change too. Like just yesterday I got the latest Connect beta up and can now do via the GX all that BT can do with my mppt. Oh my, I like that..

I've a CCGX, but all works better (for me) on a 17" lappy. I suppose I could push it to the bigscreen tv if I wanted. Ahh, maybe not.. :)

Keep thinking.

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FYI @JohnC,

Update to 4/

From the Cerbo GX manual I just learned that in a VE.Bus BMS System a DMC is mandatory.
Remote On/Off/Charger or Current limit needs to be set by the DMC. When the VE.Bus BMS is connected, the remote switch feature for the Multi is automatically set off and can't be changed. That's sad, because I was so much used to this feature. But on the other hand it's not really a big deal and is the price one must pay for when going for Lithium.

the DMC is no longer required for changing the current limit as that I think was fixed in version 2.42, however its still required for on/off/charger only. With that said, it's probably only a matter of time before that's also not required so depending on install date, you might be able to wait it out ;)

Not sure if that's technically possible. If it was, then I guess they would have implemented it already. My guess is that there will kind of a second edition VE.Bus BMS which supports remote switching. Just thinking of all boats having Lithium installed already and can't make full use of the Marine MFD GX integration.
However it goes, I'm prepared with my old DMC installed.