Old-school battery monitors on LFP

[sailingharry]

I'm continuing my ponderings about my upcoming LFP upgrade, and struggling with a BMS. I've mentioned this issue in other threads, but thought I'd ask the question specifically.

I have an ancient LINK2000 battery monitor. It's hard mounted at the Nav station. It gives, at a glance, SOC, Volts, and Amps (depending on which button was last pushed). SOC and Amps are incredibly useful info, at least to me. I want that information to be that easy to obtain with LFP (even if no one thinks you need it with LFP, "I want it!"). This would apply to other old-school battery monitors as well (Victron,etc). It also will continue in service to report on my AGM start battery.

So here's my conundrum. I'm looking at contactor based BMS (I think FET are even worse with this problem, but since I haven't been looking I don't know). As near as I can tell, the Electrodacus (which is actually a strong contender) is the only one that has a display of any sort (ABMS used to, but disconnected it). All of the others I've looked at require an app. Most (all?) aren't even bluetooth based, and don't have an app -- you connect by wifi, open a browser, and navigate to a web address.

Using my phone to get details, setup, and all that fun info is fine and I expect I'll do that several times a week. But for daily "where are we" info, that's a complete fail for me.
So, my question. I'm sure I'll have to reconfigure (Peukert's, charge efficiency, 100% reset, all that), but will a LINK2000 do a credible job of tracking LFP, and keeping that for my at-a-glance info isn't just a cobble, but a great answer? I know, they are all just Coulomb counters, but mine was designed in the last millennium for lead acid and I'm just nervous.

As an aside, my research has included the following BMS. Chargery, 123Smart, and JK all fail because as near as I can tell they have no control ports (shut down alternator, disconnect inverter, control charge sources, alarm, etc). Batrium, Nuvation, Electrodacus, and REC ABMS are all solid candidates for a contactor BMS (some are just too $$, but all meet my criteria).

[flightlead404]

I see no reason it wouldn’t work as long as you can configure
-peukert efficiency
-tail current
-possibly charged voltage
-threshold current ie below which is considered 0
-and obviously capacity

[tanglewood]

As long as it allows sufficient range in the adjustments, I can't see why it wouldn't work. I haven't used one in 20 years, but I'd certainly give it a try. The worst that can happen is you have to replace it with something else. Unless you have high C loads, I'd start with Peukert=1.0 and efficiency=98%, and work from there. The toughest part may be accounting for the BMS & contactor loads, which presumably won't be visible to the Link 1000.

[sailingharry]

Originally Posted by tanglewood

As long as it allows sufficient range in the adjustments, I can't see why it wouldn't work. I haven't used one in 20 years, but I'd certainly give it a try. The worst that can happen is you have to replace it with something else. Unless you have high C loads, I'd start with Peukert=1.0 and efficiency=98%, and work from there. The toughest part may be accounting for the BMS & contactor loads, which presumably won't be visible to the Link 1000.

I think the adjustments are all compatible. I've been frustrated with charge efficiency -- it's SUPPOSED to auto calculate, but I've found it's been horrible, but after a few weeks of watching and manually adjusting, I can get it to hit 100% SOC about the same time it re-sets to 100%. That sort of playing with LFP should do the trick too.


Separate accounting for BMS and contactor loads shouldn't be necessary. These are just loads, like anything else, and the negatives should be outside the shunt and counted. As those who know about Coulomb counters know, the nemesis is stray wires inside the shunt.

[tanglewood]

Originally Posted by sailingharry

I think the adjustments are all compatible. I've been frustrated with charge efficiency -- it's SUPPOSED to auto calculate, but I've found it's been horrible, but after a few weeks of watching and manually adjusting, I can get it to hit 100% SOC about the same time it re-sets to 100%. That sort of playing with LFP should do the trick too.


Separate accounting for BMS and contactor loads shouldn't be necessary. These are just loads, like anything else, and the negatives should be outside the shunt and counted. As those who know about Coulomb counters know, the nemesis is stray wires inside the shunt.

I recall having the same issue with my Link 1000 many moons ago, and having to adjust the efficiency by hand.


So you will install the shunt such that the BMS & contactor power is on the load side of the shunt? I wonder if that will throw off battery cell voltage measurements enough to matter? Something to consider.

[Chotu]

That’s the exact battery monitor I have and I am using and it’s doing a great job.

Just reset the Peukert's coefficient to something like 1 I think it was and it works just fine.

Actually maybe mines not the exact same one. Mine is the link lite. the same exact thing rebranded

I mean, get the fancy cool new one if that’s what you want, but don’t feel that you have to because the one you have is not adequate. It’s adequate.

I look at mine once every week or so or if it’s been cloudy for several days. Just to check there % charged. That’s how carefree the battery system is. Never needs to even be looked at. It’s crazy

[Pete7]

I have just mentioned this on another thread. Our Sterling BM is now 15 years old and probably designed before that. There is no ability to change the Peukert factor.

However, this isn't a problem. All I really want to see is what the DOD is at dawn each morning, plus the current and voltage during the day. When the batteries are fully charged or close enough, disconnecting the BM briefly then connecting back in resets the BM to assume the batteries are fully charged. If they are not and charging is still taking place, then the BM just sits there at 100% until there until the shunt sees a discharge.

I could remove and install a BMV, but have no plans to go down the Cerbo GX plus display route due to the cost, so happy to continue with the existing BM.

Pete

[sailingharry]

Originally Posted by tanglewood

So you will install the shunt such that the BMS & contactor power is on the load side of the shunt? I wonder if that will throw off battery cell voltage measurements enough to matter? Something to consider.

Well, that was in my intent. But your post, along with a post on the electrodocus website both got me looking carefully at the wiring diagrams. And it seems that it is not as simple as I had thought. In my simple mind, the BMS would have a plus wire and a minus wire that lit up the computer. And then a whole bunch of sense wires and control wires. But at least in the case of the electroducus, the sense wires are actually the power wires. All the outputs driving contactors and such can easily be powered by normal power routes, but the computer itself is not easy.

I believe the link has a configuration point for self-discharge rate. That might be a good place to hide it. But with a consumption rate around a 10th of an amp, it may be insignificant.

More significant is that a low voltage disconnect does not disconnect the BMS and so it continues to draw down a nearly flat battery.

[sailingharry]

Originally Posted by Pete7

I could remove and install a BMV, but have no plans to go down the Cerbo GX plus display route due to the cost, so happy to continue with the existing BM.



Pete

Indeed. All the discussions about CANbus and communications and all that start with a Cerbo GX, which has a very poor cost / benefit ratio. As one piece in a large Victron ecosystem, it may make sense. But not in my installation.

[SV Confianza]

The Victron SmartShunt is a super easy solution as well. You can monitor state of charge right from your phone through bluetooth. No other equipment or screens required.

That's what we are using temporarily (well, 3 years now) until I get far enough down my projects list for a more comprehensive monitoring solution for my various charging sources.

[sailingharry]

Originally Posted by SV Confianza

The Victron SmartShunt is a super easy solution as well. You can monitor state of charge right from your phone through bluetooth. No other equipment or screens required.

That's what we are using temporarily (well, 3 years now) until I get far enough down my projects list for a more comprehensive monitoring solution for my various charging sources.

Except as I indicated in my first post, that is exactly what I do not want to have to do. Otherwise, all of the BMS systems would be fine with their cell phone monitoring solution.

[CaptainRivet]

Originally Posted by sailingharry

Well, that was in my intent. But your post, along with a post on the electrodocus website both got me looking carefully at the wiring diagrams. And it seems that it is not as simple as I had thought. In my simple mind, the BMS would have a plus wire and a minus wire that lit up the computer. And then a whole bunch of sense wires and control wires. But at least in the case of the electroducus, the sense wires are actually the power wires. All the outputs driving contactors and such can easily be powered by normal power routes, but the computer itself is not easy.

I believe the link has a configuration point for self-discharge rate. That might be a good place to hide it. But with a consumption rate around a 10th of an amp, it may be insignificant.

More significant is that a low voltage disconnect does not disconnect the BMS and so it continues to draw down a nearly flat battery.

what are the components of your ecosystem??
Electrodacus is the joice if you have devices that have an external remote the BMS can switch on or off like all victron devices. If not its not your BMS!
nothing wrong with a good FET based BMS if you have a simple system that fits to it, its often a very good choice if you want a simple conversion from lead with DC2DC chargers for the alternator. Add a BMV712 to do some last resort stuff and get a reliable SOC battery monitor and you are done.

i have an all victron system with Electrodacus BMS and DIY LFP bank.

And with electrodacus you don't need a battery monitor, it is one and even better SOC then BMV712. you get a web interface and eg i use an old ipad1 as screen at the navstation that otherwise wouldn't have no use anymore then a photoframe.

Instead of trying to integrate all you have simplify you system and get rid of stuff you don't need with LFP anymore.


"you connect by wifi, open a browser, and navigate to a web address", perfect you can use an old ipad mini as screen (get it for 50Euro), set a fixed ip for the bms and put that as start page in your browser or with safari create a shortcut you start directly from screen like an app. huge adavantage is as long as you have a browser it runs on every device doesn't matter which OS or how old it is and no app updating/incompatibilities...

[sailorboy1]

If you have an old BM you using with LFP and can not change the PE or charge efficiency so what.

Stop stop looking anything other aH out and voltage and don't worry about it.