Critique my LiFePo4 Plan!

[mbartosch]

Originally Posted by Dockhead

As I posted in another thread, I don't believe this is true. If the same signal is used to cut the field wire to the alternator which acuates the high voltage cutoff, the high voltage cutoff acts almost instaneously, whereas it takes a certain amount of time for the alternator to shut down. So you'll still zap the diodes.



I think you need an alternator protection device in addition to this.

No, you don’t.

The trick is to attach the alternator more or less directly to the battery, NOT to the charge bus which is controlled by the
HVC event.
Stopping alt charging via regulator shutdown IS the HVC for the alt which you want. If the HVC occurs, the charge bus and all non inductive charging sources are separated. The alt gets shut down when field is powered down and will continue to produce energy for a very short time after HVC, dumping the energy into the bank.

[Maine Sail]

A few thoughts.

1- The Balmar regulators, for an LFP disconnect/load dump protection should be de-powered by the red regulator B+ wire (Terminal #2) not field (Blue) or ignition (brown) (unless you have plenty of time as brown saves some data before shutting down the regulator). For example the FCC circuit on a Lithionics battery, or the HVC on the old HPBMS shut down carging well before the battery is disconnected. Not all BMS systems provide for this. Cutting the regulator at the same time as the bank can still result in a load dump. Cutting regulator ignition/brown guarantees a load dump. At a bare minimum a Sterling Power Alternator Protection Device should be used as you also have a large inverter/charger with no way to shut that down shown.

2- The BMV shunt needs to be directly after the battery negative and every negative wire on the boat is connected to the load/system side of the shunt including regulator B- (terminal #1 and the relay coil wire)

3- It would appear that you are using a BMS designed for a "drop-in" battery to trigger a 500A relay. Unfortunately to depower an alternator or large I/C correctly, in order to avoid a transient, this cut needs to occur ever so slightly before the relay opens. By wiring the alternator B+ and B- directly to your pack (neg on load side of shunt and relay after the shunt), you can still cut the regulator with the relay and the alternator will not be load dumped as the alts B+ & B- output wires are physically connected ahead of the relay. Only the regulator would be shut down wiring like this. With drop-in LFP batteries you can't do this because you no access to the internal BMS. The only risk here is that if the alternator does get damaged, and creates back drain, the bank is not protected from over-discharge.

4- Setting a 90A alternator to run at 80A, into a 600Ah LFP bank, will not be enough, unless you're using a very heavy duty large frame alternator or you are rectifying that alternator remotely. Depending upon the alternator you're looking at 25% less to 60% less than rated to keep it within a safe operational envelope. Alt temp sense should ideally be utilized as your insurance policy and Belt Load Manager as your primary protection for the alternator.

5- Why is the alternator passing through the house battery switch? If you want to do this then you'll want a Sterling Power Alternator Protection Device. Good cheap insurance..

6- If you have a breaker in-line for the alternator it needs to be as close to the bank as is possible (preferably within 7" of the bank but after a Class T fuse for main bank protection. It should also be rated to at least 150% of the alternators output rating. The regulator B+ (terminal 2) should also be wired to the alternator side of the breaker so if it's accidentally left off you can't boot the regulator without the alternator.

7- Your BB1230 can only charge the start and windlass banks when those switches are on. BB1230 needs a fuse within 7" of the house bank and a fuse at the other end as well.

8- ANL fuses do not have the AIC rating for LFP. For main bank protection Class T fuses should really be used.

9- Your PV controller needs a fuse sized to protect its wire. You can't fit a wire large enough for a 300A fuse into that controller.

10- Inverter charger should have an ON/OFF battery switch in the positive feed.

11- I see no way to shut down the BMS. That 500A relay will burn power 24/7/365. One of the best relays for this job is the Tyco EV200 with coil economizer.

12- Be sure to at least capacity test each cell and carefully match your parallel blocks for capacity. We have had a lot of very poorly matched cells come through our shop lately, most likely B grade or reject cells most from AliX vendors.. You'll then need to do a good top balance.

[Qismat]

Thank you for chiming in! This is very useful!

Originally Posted by Maine Sail

A few thoughts.

The Balmar regulators, for an LFP disconnect/load dump protection should be de-powered by the red regulator B+ wire (Terminal #2) not field (Blue) or ignition (brown) (unless you have plenty of time as brown saves some data before shutting down the regulator). For example the FCC circuit on a Lithionics battery, or the HVC on the old HPBMS shut down carging well before the battery is disconnected. Not all BMS systems provide for this. Cutting the regulator at the same time as the bank can still result in a load dump. Cutting regulator ignition/brown guarantees a load dump. At a bare minimum a Sterling Power Alternator Protection Device should be used as you also have a large inverter/charger with no way to shut that down shown.

I was hoping to cut the regulator with the BMS somehow, but i suppose an APD will do. The I/C can be shut down on its own protocols, no? based on the charge profile. Or are your referring to a HVC situation?

Originally Posted by Maine Sail

The BMV shunt needs to be directly after the battery negative and every negative wire on the boat is connected to the load/system side of the shunt including regulator B- (terminal #1 and the relay coil wire)

Is that not how I have it set? As it sits now the Batteries are on one side of the shunt, with everything else (I/C, Solar in, BMV-712, and Ground Bus) reading off the other side. (I still currently have my FLA installed).

Originally Posted by Maine Sail

It would appear that you are using a BMS designed for a "drop-in" battery to trigger a 500A relay. Unfortunately to depower an alternator or large I/C correctly, in order to avoid a transient, this cut needs to occur ever so slightly before the relay opens. By wiring the alternator B+ and B- directly to your pack (neg on load side of shunt and relay after the shunt), you can still cut the regulator with the relay and the alternator will not be load dumped as the alts B+ & B- output wires are physically connected ahead of the relay. Only the regulator would be shut down wiring like this. With drop-in LFP batteries you can't do this because you no access to the internal BMS. The only risk here is that if the alternator does get damaged, and creates back drain, the bank is not protected from over-discharge.

Yes, its a minimal style BMS designed to drop the negative when an issue rises - Its not an REC BMS which I'm not sure even how to buy from Canada, they haven't anwered my emails and they're in europe, and there doesn't seem to be much other option than the ones Will Prowse is using...

I'm not sure I understand when you say "By wiring the alt B+ and B- directly to your pack" but then state "neg on load side of shunt and relay after the shunt" Do you mean move the relay to after the shunt? Ie it would go Battery -> Shunt -> Cutoff Relay ->Sources(solar,IC,BMV etc?)

Originally Posted by Maine Sail

Setting a 90A alternator to run at 80A, into a 600Ah LFP bank, will not be enough, unless you're using a very heavy duty large frame alternator or you are rectifying that alternator remotely. Depending upon the alternator you're looking at 25% less to 60% less than rated to keep it within a safe operational envelope. Alt temp sense should ideally be utilized as your insurance policy and Belt Load Manager as your primary protection for the alternator.

Alright, i'll have to dial it back to 60 with the BLM and the temp sensor settings. Thanks.

Originally Posted by Maine Sail

Why is the alternator passing through the house battery switch? If you want to do this then you'll want a Sterling Power Alternator Protection Device. Good cheap insurance..

I've removed this in my new plan and put the Alternator B+ Right to the charge bus - Is this better? The charge bus then feeds the main bus which feeds the load bus, which then goes to the house switch.

Originally Posted by Maine Sail

If you have a breaker in-line for the alternator it needs to be as close to the bank as is possible (preferably within 7" of the bank but after a Class T fuse for main bank protection. It should also be rated to at least 150% of the alternators output rating. The regulator B+ (terminal 2) should also be wired to the alternator side of the breaker so if it's accidentally left off you can't boot the regulator without the alternator.

So wire the regulator B+ to the same place as the Alt B+? That seems like it would result in losing the ability to cut the regulator B+ wire to kill the regulator.

Originally Posted by Maine Sail

Your BB1230 can only charge the start and windlass banks when those switches are on. BB1230 needs a fuse within 7" of the house bank and a fuse at the other end as well.

Correct - Only chargeable when the switches are on. I will fuse these locations.

Originally Posted by Maine Sail

ANL fuses do not have the AIC rating for LFP. For main bank protection Class T fuses should really be used.

So a Class T fuse just off the B+ terminal? sized for the wires from the B+?

Originally Posted by Maine Sail

Your PV controller needs a fuse sized to protect its wire. You can't fit a wire large enough for a 300A fuse into that controller.

It currently doesn't have a fuse inline - The PV controller can only feed 50 Amps, so wouldn't a 60 Amp fuse then be sufficient inline?

Originally Posted by Maine Sail

Inverter charger should have an ON/OFF battery switch in the positive feed.

Will install.

Originally Posted by Maine Sail

I see no way to shut down the BMS. That 500A relay will burn power 24/7/365. One of the best relays for this job is the Tyco EV200 with coil economizer.

What would you suggest to be able to shut down the BMS? A switch in the C- wire of the BMS? When would I shut down the BMS?

Originally Posted by Maine Sail

Be sure to at least capacity test each cell and carefully match your parallel blocks for capacity. We have had a lot of very poorly matched cells come through our shop lately, most likely B grade or reject cells most from AliX vendors.. You'll then need to do a good top balance.

Yes, I will be doing a full bench test on the cells and balancing them.

Sorry - I want to make sure I understand all of this correctly!

[Steve_C]

I regards to REC, I was having trouble reaching them as well. I was given the email of Maja Pozar maja@rec-bms.com and he has been incredibly helpful and prompt. I have attached the price list he provided.

They also accept PayPal!

[nebster]

If you just want a minimal, no-fuss BMS that's not the one from China that Will Prowse uses, check out Zeva's 8-cell monitor. These are cheap and work great for simple LVD/HVD and charge enable/disable. And they will customize the firmware for you if you want, for not too much.

[kirklkjb]

Looks to me that you are missing a bunch of fuses. Everything connected to a battery source should have a fuse in it. One short in a cable connected to a battery and your boat is burning down.

[Sir Rondo Normal]

Forgive me if this is a stupid question. I'm in the process of trying to plan my own system and my head hurts.

How is it that you're getting away with only one solenoid? Don't you need one for the high voltage protection and one for low voltage too?

[rom]

Originally Posted by Maine Sail

6- If you have a breaker in-line for the alternator it needs to be as close to the bank as is possible (preferably within 7" of the bank but after a Class T fuse for main bank protection. It should also be rated to at least 150% of the alternators output rating.

And the cable should then be rated what ? 200% of alt output ? Is this really practical when talking 200+A alternators ?

Originally Posted by Maine Sail

10- Inverter charger should have an ON/OFF battery switch in the positive feed.

Why would you add such design complexity and voltage drop when you can use the on/off button on the inverter ?

[Steve_C]

Originally Posted by Sir Rondo Normal

Forgive me if this is a stupid question. I'm in the process of trying to plan my own system and my head hurts.

How is it that you're getting away with only one solenoid? Don't you need one for the high voltage protection and one for low voltage too?

This entire design is hard to understand. Supposedly changes are being made, but we would need to see an updated schematic to understand and make sure we are talking about the same things.

Right now if there is a High Voltage event and the one main contactor opens, the entire system is unusable. With separate disconnects controlled by the BMS on the LOAD and CHARGE bus you can stop any additional charging but still continue to operate and discharge the bank, which is what you want.

Qismat, you have been given a lot of input on this thread. Please do an updated plan so we can see where your current design plan is and provide feedback if that's what you still want.

[s/v Jedi]

Originally Posted by nebster

If you just want a minimal, no-fuss BMS that's not the one from China that Will Prowse uses, check out Zeva's 8-cell monitor. These are cheap and work great for simple LVD/HVD and charge enable/disable. And they will customize the firmware for you if you want, for not too much.

This looks good, except that I want to drive the Blue Sea Systems remote battery disconnects which want a pulse for on and off, and provide a feedback on it’s switch position.

This product looks like an arduino integrated with cell monitor chips (ATtiny?) and I had planned to make one myself...

[Steve_C]

Originally Posted by s/v Jedi

This looks good, except that I want to drive the Blue Sea Systems remote battery disconnects which want a pulse for on and off, and provide a feedback on it’s switch position.

This product looks like an arduino integrated with cell monitor chips (ATtiny?) and I had planned to make one myself...

I am using the Blue Sea RBS disconnects myself. I wanted the ability to have the BMS control them, Have the ability to manually overide and lock them in the Open state as well as the ability to manually close them remotely, all with LED confirmation.

There are multiple choices for the control of these. I chose the 7717 - 24 Volt.

This version does not need a separate momentary signal for open and close respectively. It has 1 control circuit that when it detects the 24 volt signal it closes and stays closed as long as it detects the voltage. It is a true latching design, just like the other models from Blue Sea, so it is using only 3mV to monitor and no current is used to keep it closed. Once it no longer detects the "Close" signal it opens.

This lends itself to the way the BMS operates much better than the other models that require a "Momentary" signal. This would require you to take the constant output from the BMS and provide a "Momentary" pulse to operate the switch.

I have purchased 3 of the 24V - 7717 ML-RBS and am creating my schematic right now.

Isn't your system also 24 Volt Jedi?

[Sir Rondo Normal]

Originally Posted by Steve_C

This entire design is hard to understand. Supposedly changes are being made, but we would need to see an updated schematic to understand and make sure we are talking about the same things.

Right now if there is a High Voltage event and the one main contactor opens, the entire system is unusable. With separate disconnects controlled by the BMS on the LOAD and CHARGE bus you can stop any additional charging but still continue to operate and discharge the bank, which is what you want.

Qismat, you have been given a lot of input on this thread. Please do an updated plan so we can see where your current design plan is and provide feedback if that's what you still want.

Ok, I see. So then the solenoid is on the grd side to shut the whole system down in case of either a LV or HV situation and it must must be overidden and the situation corrected before normal operation can resume.

Thanks.

[s/v Jedi]

Originally Posted by Steve_C

I am using the Blue Sea RBS disconnects myself. I wanted the ability to have the BMS control them, Have the ability to manually overide and lock them in the Open state as well as the ability to manually close them remotely, all with LED confirmation.

There are multiple choices for the control of these. I chose the 7717 - 24 Volt.

This version does not need a separate momentary signal for open and close respectively. It has 1 control circuit that when it detects the 24 volt signal it closes and stays closed as long as it detects the voltage. It is a true latching design, just like the other models from Blue Sea, so it is using only 3mV to monitor and no current is used to keep it closed. Once it no longer detects the "Close" signal it opens.

This lends itself to the way the BMS operates much better than the other models that require a "Momentary" signal. This would require you to take the constant output from the BMS and provide a "Momentary" pulse to operate the switch.

I have purchased 3 of the 24V - 7717 ML-RBS and am creating my schematic right now.

Isn't your system also 24 Volt Jedi?

We’re 12V. When you program this yourself it does not matter which way it works. For me it’s easy as I once designed microcomputers myself so hacking an Arduino with some extra chips is easy. I may even add a nmea2000 interface to report battery status as well

Actually, I have so many Arduino projects coming up that I ordered a lab inventory of the stuff and my phone is telling me that Amazon just left it all at my door

[nebster]

Originally Posted by s/v Jedi

This looks good, except that I want to drive the Blue Sea Systems remote battery disconnects which want a pulse for on and off, and provide a feedback on it’s switch position.

I'm sure Zeva would give you a pulsed logic output if you wanted it, or you could of course convert it yourself. I'm not sure it could do anything with position feedback.

This product looks like an arduino integrated with cell monitor chips (ATtiny?) and I had planned to make one myself...

I know it's an ATmega inside, but I'm not sure if it's full-on arduino or what. My experience with such "low level" devices is limited to Teensy 3. Building your own seems like you get to endure the challenge of building good, isolated voltage monitoring while placing precisely equal loads on all the cells over time. Non-trivial, at least based on how many flawed implementations have been let out in the wild in the past!

[s/v Jedi]

Originally Posted by nebster

I'm sure Zeva would give you a pulsed logic output if you wanted it, or you could of course convert it yourself. I'm not sure it could do anything with position feedback.

I know it's an ATmega inside, but I'm not sure if it's full-on arduino or what. My experience with such "low level" devices is limited to Teensy 3. Building your own seems like you get to endure the challenge of building good, isolated voltage monitoring while placing precisely equal loads on all the cells over time. Non-trivial, at least based on how many flawed implementations have been let out in the wild in the past!

The trick is to use one microcontroller per cell, power it directly from that cell, measure it’s voltage and temperature, decide if it’s good to go or if a HVC or LVC event is required and communicate that to the outside in a galvanically isolated way. That can be onto-couplers on a communication line (CANbus like Victron does I think) or as simple as small signal relais.
When put into sleep mode, these only use 8-10 uA which is more than 10 times less as the cell self-discharge.

I have so many plans, like for smart breakerpanels etc. that my mind is blown a couple of times a day as I realize more possibilities opening up