Merged LiFeYPO4 1000Ah Winston prismatic cells and all electric galley...

[hzcruiser]

Originally Posted by tanglewood

I agree on having some way of verifying contactor operation, and many contactors are available with aux contacts that follow the main contacts and are designed to provide exactly this feedback. So you command the contactor while at the same time sensing the aux contacts. [...]

Is there a schematic of how this contactor with aux works? Is it like a second set of contacts that carry a small test current?

[s/v Jedi]

Originally Posted by hzcruiser

Not necessarily a mistake but often a design decision and, as mentioned, ultimately a matter of increased complexity, chances of false positives, energy efficiency and cost.

I can't recall seeing relays with some extra feedback line?

One might think it can't be too hard to detect if a relay has switched state successfully, or can it?
Well, I thought I had this fully covered by measuring the voltage on either tab of the relay as well as the current going through the relay. Some might already say that's over-engineered...
Turns out even this approach is neither fool nor bullet proof: if you have a number of batts in parallel (like I'm handling every batt like a batt bank) and the system is at rest, meaning current flows are close to zero and voltages are equal, opening the relay cannot be detected by the means mentioned above.

Only later on, if some load or charger gets introduced, a discrepancy can be detected.
This can be seen as a negligible side-effect, but it nevertheless shows that even measuring a lot can sometimes be misleading.

Many latching solenoids have aux contacts just for this reason. The switch routine is foolproof and can only fail when the solenoid has failed... and you detect this. The pseudo code snippet I listed before requires a timeout of-course, which indicates solenoid failure.

[hzcruiser]

Originally Posted by s/v Jedi

Many latching solenoids have aux contacts just for this reason. The switch routine is foolproof and can only fail when the solenoid has failed... and you detect this. The pseudo code snippet I listed before requires a timeout of-course, which indicates solenoid failure.

In that case it would be almost negligent not to check for it.

[s/v Jedi]

Originally Posted by hzcruiser

In that case it would be almost negligent not to check for it.

The problem is that the designers of REC BMS did not support that, not do they have spare I/O pins in their wiring harness so it would require a logic adapter board. Sounds like a great application for a Tiny85

[tanglewood]

Originally Posted by hzcruiser

Is there a schematic of how this contactor with aux works? Is it like a second set of contacts that carry a small test current?

Gigavac contactors seem to be commonly used, and are available with aux contacts. https://www.gigavac.com/catalog/powe...ucts/gv-series


I have also used ABB's AF series of contactors for an AC switching application, and they are all available with aux contacts that are mechanically interlocked with the main contactor, and that open and close only after the main contactor has done the same. Regardless, I built in a delay after the aux contact indicates any parallel contactor has opened before commanding the new contactor closed. It also continuously monitors to ensure that the commanded and sensed positions are the same, allowing for a short gap during changeovers. And failure in the main or aux contactor, sense inputs, or relay driver is detected right away.

[beckett]

Originally Posted by beckett

Thank you.

Tonight I am a bit disappointed with myself ... I got an email from REC to realize that I was reading a manual for the wrong BMS. I was looking at the REC ABMS(that you use), however, I need to be looking at REC SI BMS: REC d.o.o. ...

I will have 8 cells(8S) and this REC SI BMS allows for 5-16 cells but does not have features of REC ABMS. Specifically, it seems to have only 1 optocoupler and 1 user-defined relays. I think they betting on CAN bus communications via CCGX, VINUS GX, or CERBO GX.

I have to re-think everything and look for other examples of an 8S battery built with REC BMS SI and the battery protection I have been learning looking at your design. Do you have any advice where do I go from here?

I am now pretty sure that REC SI BMS unfortunately is a very different beast from REC ABMS.

Ideally, I just needed REC ABMS for 24V or 8 cells... ))) unfortunately the REC SI BMS has only one charge optocoupler and only one relay for charging control. “REC SI BMS communicates with Victron via CAN and CCGX will be configured with DVCC to let the BMS decide the whole charging thing.”
REC has confirmed that pin 4/5 of the internal relay can be reprogrammed as a Load Control but only on a “battery“ level, not on a cell level. Not sure how dangerous this might be but I think it’s not as REC ABMS has cell level control.
I am too green in LiFePo4 to figure out if this route with REC SI BMS, Victron, CCGX, CAN communications would be suitable, safe or what I need for my future system.
I am glad I am learning and many thanks to CatNewBee for all your help and the inspiration! I will continue researching and hopefully will find a solution soon.

[CatNewBee]

The SI is the big brother of the ABMS, it measures and reacts on cell values, it just has less outputs. It is totaly comparable to all other BMS around with either single bus switching or charge / load bus switching, and it also has CAN integration, it only misses the two extra contacts the ABMS provides.

[beckett]

Originally Posted by CatNewBee

The SI is the big brother of the ABMS, it measures and reacts on cell values, it just has less outputs. It is totaly comparable to all other BMS around with either single bus switching or charge / load bus switching, and it also has CAN integration, it only misses the two extra contacts the ABMS provides.

Thank you. I guess to substitute for the "two missing extra contacts", which you use to control your Quatro, I would let REC SI BMS control the Victron Quatro charging and inverter via CAN bus integration? That would leave me with one optocoupler and one relay to control the battery LVC and HVC using two ML-RBS relays for the charge and load bus?

[newhaul]

I really don't get the making everything so complex.
I installed my Lfp 250ah 12v bank simply with a 200 amp in and out bms and simple battery monitor .
I believe in kiss . And every additional connection is a possible failure point you need to account for in life on the boat.
The meter does SOC, current in and out as well as state of charge .

[arsenelupiga]

Originally Posted by newhaul

I really don't get the making everything so complex.
I installed my Lfp 250ah 12v bank simply with a 200 amp in and out bms and simple battery monitor .
I believe in kiss . And every additional connection is a possible failure point you need to account for in life on the boat.
The meter does SOC, current in and out as well as state of charge .

from my research the main problem is multiple charging sources. Gets messy and can ruin your battery if you do not address correctly.

I also use simplicity method and have only 360W solar charging 400ah house batteries. On odd occasions I start generator to remove deficit from string of cloudy days but always let solar finish charging as victron has the best controllers out there. 0 issues in 2 years.

And of course CNB was my inspiration

[newhaul]

Originally Posted by arsenelupiga

from my research the main problem is multiple charging sources. Gets messy and can ruin your battery if you do not address correctly.

I also use simplicity method and have only 360W solar charging 400ah house batteries. On odd occasions I start generator to remove deficit from string of cloudy days but always let solar finish charging as victron has the best controllers out there. 0 issues in 2 years.

And of course CNB was my inspiration

I have 400 watts solar running through a 30 amp pwm controller and an airx 400 wind generator running on its built in pwm controller .
Thinking about a 75 amp alternator to run through a 60 amp b2b from the lead start to the lfp . Also a little 1k harbor freight genny that can run my 50 amp portable charger. Never had any issues . The solar and wind talk just fine its all about the voltage to them.

[s/v Jedi]

Originally Posted by newhaul

I really don't get the making everything so complex.
I installed my Lfp 250ah 12v bank simply with a 200 amp in and out bms and simple battery monitor .
I believe in kiss . And every additional connection is a possible failure point you need to account for in life on the boat.
The meter does SOC, current in and out as well as state of charge .

Two questions:

1 you always charge to 100% and keep a float charge after that?

2 what happens if your BMS switches the battery offline for any reason? I don’t just mean for things like electronics, autopilot etc. but also what happens to the alternator, charge controllers etc. when the battery is switched off suddenly?

[newhaul]

Originally Posted by s/v Jedi

Two questions:

1 you always charge to 100% and keep a float charge after that?

2 what happens if your BMS switches the battery offline for any reason? I don’t just mean for things like electronics, autopilot etc. but also what happens to the alternator, charge controllers etc. when the battery is switched off suddenly?

answer to #1. Actually no I don't I set my charge controllers to 13.8 v so just about 98%
At that point my dump load takes over and heats my water. Disconnect of my Lfp would not be an issue my controllers are not affected by loss of of battery based power .


#2. Read my next post I have a small Fla battery that is my start bank. So a disconnect would not be a killer . Aside from the fact I don't use my iron wind to charge my house bank. The alternator and 60 amp b2b is the oh Crap backup to my solar , wind , and 1k generator and portable charger . ( used in that order as needed)


what happens to your systems in the event you suffer the same that you asked me

[s/v Jedi]

Originally Posted by newhaul

answer to #1. Actually no I don't I set my charge controllers to 13.8 v so just about 98%
At that point my dump load takes over and heats my water. Disconnect of my Lfp would not be an issue my controllers are not affected by loss of of battery based power .


#2. Read my next post I have a small Fla battery that is my start bank. So a disconnect would not be a killer . Aside from the fact I don't use my iron wind to charge my house bank. The alternator and 60 amp b2b is the oh Crap backup to my solar , wind , and 1k generator and portable charger . ( used in that order as needed)


what happens to your systems in the event you suffer the same that you asked me

Haha.. okay, I also have a lead acid to take the punishment but in my defense, it is an AGM

I have an Outback solar controller and must admit I don’t know what it will do, but I am going to replace it when we replace panels and will get a dedicated Victron for each panel (big panels).

We don’t float charge Lithium but I’m going to change everything again and am still working it out before I can tell more about it

[newhaul]

Originally Posted by s/v Jedi

Haha.. okay, I also have a lead acid to take the punishment but in my defense, it is an AGM

I have an Outback solar controller and must admit I don’t know what it will do, but I am going to replace it when we replace panels and will get a dedicated Victron for each panel (big panels).

We don’t float charge Lithium but I’m going to change everything again and am still working it out before I can tell more about it

Im a retired navy engineer ( hull tech) i always think worst case and plan ahead for it so it wont happen . How many ways have you planned to stop water ingress due to hitting something at 0300? ( just an example of my thinking )