Lithium System Upgrade (REC BMS, Victron, Other)

[geoffr]

Looking for the wisdom of the internet as I'm putting together our upgrade to Lithium. I thinks I've got it all sorted out, but wanted to see if the wisdom here catches any errors or mistakes or suggested improvements.

I still haven't decided on the size of the LiFePO4 bank. Old LA is 675Ah (Trojan T105s). There is thinking of adding a 40A DC A/C in the future which would obviously mean a larger battery (and probably a second AC charger in parallel)

(Drawing attached)

Thanks!

[tanglewood]

Can you upload the drawing as a PDF? I can't zoom in and read what you have.

[UFO]

Have a look at this BMS:


https://123electric.eu/products/123smartbms-gen3/


I have been very happy with it and have had NO Issues over the last few years and it has kept the bank (1120Ah) well balanced - The price though may make your eyes water a bit

[wholybee]

Originally Posted by UFO

Have a look at this BMS:


https://123electric.eu/products/123smartbms-gen3/


I have been very happy with it and have had NO Issues over the last few years and it has kept the bank (1120Ah) well balanced - The price though may make your eyes water a bit

I'll add some really bad experience with that BMS. Lots of replacing failed boards, and needing to keep spares, problems with the connectors used for the bus between the boards, and ultimately the death of some expensive sinopoly cells.
When the master board finally caught on fire, the only thing available for immediate shipment was a P.O.S. Daly from Amazon. The Daly has been working for a couple years now with zero maintenance or problems. So as poorly as the Daly is rated/recommended, I rate the 123 worse.
This was not my vessel, but a friends vessel that I intervened with to get him sailing again. I just cleaned up the mess.
The REC and Victron are both excellent high-end options. Electrodacus is also popular and seems to be good quality.

[fxykty]

Not the cheapest but fully featured and very well functional: TAO BMS. https://www.taoperf.com/

[UFO]

Originally Posted by wholybee

I'll add some really bad experience with that BMS. Lots of replacing failed boards, and needing to keep spares, problems with the connectors used for the bus between the boards, and ultimately the death of some expensive sinopoly cells.
When the master board finally caught on fire, the only thing available for immediate shipment was a P.O.S. Daly from Amazon. The Daly has been working for a couple years now with zero maintenance or problems. So as poorly as the Daly is rated/recommended, I rate the 123 worse.
This was not my vessel, but a friends vessel that I intervened with to get him sailing again. I just cleaned up the mess.
The REC and Victron are both excellent high-end options. Electrodacus is also popular and seems to be good quality.

Yes they are fiddly to set up and your soldering skills need to be up to par. Not sure how the connectors between boards can mess up? as they are a very simple connection.


Anyway they have been very good for me and also a friend who recommended them to me who has had them even longer.


The TAO BMS as FXYKTY mentioned does look very good, but pricey as they stated

[wholybee]

The buss connection on the smart123 is just a push in friction connector. A small amount of vibration/movement or corrosion and it stops working. And if you need to take it apart to replace boards a few times, it gets worse.
Just one persons experience. You aren't the only person I have heard that really likes it. But having worked with a number of BMSs, it isn't one I personally would consider.

[geoffr]

Originally Posted by tanglewood

Can you upload the drawing as a PDF? I can't zoom in and read what you have.

Sure - here is a pdf.

[geoffr]

OP here - Thanks for the comments regarding other BMS, but unless the BMS talks to Victron equipment it's a non-starter for me. At this point unless there is a really compelling reason to switch I'll stick with REC.

[mvweebles]

A couple of general comments.

Rod Collins (Marine How To) likes the Epoch LFPs which are available with Victron interface.

If my math is correct, your showing about 500w solar. Plus 125a (12v?) Alternator. Won't go far for AC drawing down a 600ah LFP battery bank. But a lot depends on how your refrigeration is setup and what climate you'll be in (though if you need AC, likely decent load for refrigeration).

I'll look forward to other more knowledgeable comments. System looks complex to my eyes with many places requiring configuration and failed interoperability.

[geoffr]

I had originally planned on one of the "drop in" batteries like Epoch, but I wasn't able to find a solution to control the alternator and non-Victron solar controllers. Also by making my own battery pack from cells it's a lot cheaper. (even with the external BMS)

[geoffr]

Oh and yes, AC running off a 600Ah battery won't last long. (hence my comment about installing a second shore power charger )

[hjohnson]

I've gone all in on the Victron ecosystem, and am very happy with the results.

Rec ABMS managing my battery, Wakespeed WS500 managing my alternator, Cerbo GX, a pair of MPPTs, Multiplus Inverter/Charger, Tank 140, and other toys.

I'd really recommend moving yourself towards that, as having everything fully integrated makes life so much easier. It's at the point where i simply don't ever think about the power system on my boat any more, other than making sure to breaker off the hot water tank when away from the dock. Everything just works(tm). I get that you're trying to retain existing components (the Xantrex and the MPPTs) but I think you're adding a fair bit of complexity to keep those around, especially the solar controllers. The Victron MPPTs aren't stupid expensive, and well worth swapping in.

The thing I would do, though, is stick with two contactors one for your DC loads only (you can make that one a Battery Protect managed by the REC) and then the other the DC charging bus for your solar controllers, alternator, and inverter/charger. The REC is setup to work that way, and it works quite well.

[HankOnthewater]

Hi GeoffR, I am in the same boat, upgrading to lithium.
As your diagram shows, it is not really KISS. The diagrams I have drawn for my setup are just as complicated, but not looking as professional as yours. What software did you use for that?

Over the last few years one of the great advantages of LFP was (as we were told) that capacity can be reduced to about half (compared with LA=lead acid).
Now we learn, that really the useable SoC of LFP is between 20 and 80% (=60% of total capacity), that is if we want the LFP batteries to last. The target SoC of AGMs was 50 to 100%, = 50% useable capacity.
So, the capacity of new LFP should be closer to the old AGM one. My new LFP capacity is about 5% higher compared with my AGMs that will be removed this side of Xmas (I hope it is 2023 )

I was hoping that there would be more simple diagrams, maybe the future will give us more simple setups? Maybe it is drop-in LFP? Or new battery chemistry?

However, I am going with 4 LFP batteries in series, and monitored by TAO BMS (as in post #5), but it is as complicated as REC BMS in your diagram, maybe worse as I have 4 alternators.

Hmmm, at times I yearn again to simple sailing, no ugly solar panels on ugly stern arches, oil lamps for lighting, paper charts for navigation, maybe even without an engine. Likely that would be my next boat, when these LFP need replacing

[barcoMeCasa]

Originally Posted by HankOnthewater

Now we learn, that really the useable SoC of LFP is between 20 and 80% (=60% of total capacity), that is if we want the LFP batteries to last.

Not so sure there's much if any data to back that up, maybe for long term storage. Plus would be difficult to know what the SOC would be after a few cycles. High voltage generally seems to be the thing generally considered to be best avoided for longevity so stopping charging around 13.6v/13.8v would be just into the top "knee" where the voltage starts to increase rapidly when charging which takes you up much closer to full.