Blackouts and Backup Comms/Nav Power

[rslifkin]

Many ships are reliant on generators, etc. so the GMDSS mandated backup batteries, etc. make sense in that context. Most of us are already running our electronics on battery power, so the potential failure modes that could cause a blackout at the helm are very different.

A backup isn't a bad idea, but it does need periodic testing to ensure it's actually working as expected.

[CaptainRivet]

Originally Posted by Dockhead

Sounds like you would benefit in several ways.


The re-wiring is extremely simple since you are just inserting the charger and battery into the lead which powers your electronics. Or, if you need to separate the electronics from something else in your panel, just a small bus bar.


I'm thinking that a lead, rather than LFP battery, would be good for this because in normal operation it will always be fully charged, something lead likes and LFP does not like. Or LTO.


Downside, besides adding a bit of complexity to the wiring, is a little efficiency loss through the DC-DC charger.

Well I didn't want a lead in my salon to gas out and turn my cat in swimming gas chamber.
That's why LTO is the best here, if not use a Lifepo4 and artificially cycle it deeper by using a low float voltage like 13.3V and big offset 0.15V of for a rebulk but for that you need a DC2DC charger for the buffer. Like this it cycles between 70 and 100%SOC and doesn't sit around on a high state of charge.

Size wise an LTO is more comparable to a lead as lower energy density is closer to lead then to LFP, a 50AH Lifepo4 (with only 50A const. Discharge, peak 100A) has the same size and weight as a 20AH LTO but the LTO can do 200A constant and 400A peak. I use lTO here because it has longer lifespan, the better discharge curve and the small capacity is enough plus with high current capability can emergency start an engine.
When using lead you introduce the weakest link into your system exactly to the most important electronics.

Additional advantage of a buffer its continuously tested to work and also doesn't need a manual intervention (flipping a switch) when house has a blackout.

[smac999]

dockhead's 12 page electical system isn't good enough so now he's working on adding page 13. incase the first 12 pages fail.

maybe you should stop thinking every so often.

[smac999]

never mind I confused you for s/v Jedi for a min . you both post lots but he's the one with all the stupid diagrams and overthinking everything. and now I can't edit my post

[svloki]

Originally Posted by smac999

never mind I confused you for s/v Jedi for a min . you both post lots but he's the one with all the stupid diagrams and overthinking everything. and now I can't edit my post

I for one have found Jedi's diagram very useful. He obviously put a lot of effort into it. Others should do the same if they have an approach that works for more modest vessels. Good to learn from the knowledge base here.

[barcoMeCasa]

Originally Posted by Dockhead

What do you guys think?

After having batteries fail in South America then the engine failed at the same time as the anchor windlass.. wasn't a good day.... but after the next refit the boat can now cross oceans no problem if all the toys break.

Aries windvane, tiny bit of power needed to run some lights.

[Dockhead]

Originally Posted by smac999

never mind I confused you for s/v Jedi for a min . you both post lots but he's the one with all the stupid diagrams and overthinking everything. and now I can't edit my post

The difference between me and Jedi is that he is an actual EE who does actual design work and excellent drawings, and I'm a lawyer who is way out of his element, struggling to understand how all this sparky stuff works.

[Loredo]

Dockhead, let me ask you a couple questions. You've had lead batteries for your whole sailing time in the past, right? Over the years you got used to keep an (close) eye on their voltage / charge, water level? You got used to monitor them all the time? Charge them when it's timely, not over-discharge them and so on. Am I right here?



Did that lead acid battery system have all"protections" build in you're thinking about for the LFP's? What I'm wanting to bring through is this, does any system need to be build to "idiot proof standards" when there is a man with a brain behind those systems? Jedi's stuff is technically correct, yet I did not follow his line of thinking. My take is that adding all that (electronic) stuff to a system adds also possible failure points. When I started building my LFP I had not one but two BMS's fail on me within a couple weeks. Bad luck? Maybe... I ended up installing a house bank without a BMS. Don't get me wrong, my system has all the necessary fuses voltage monitors and whatnot build in. Just no automatic protections. That's what my brain is for. After a couple years with the LFP's... SWEET! I keep a close eye (less and less) on them only to find out the stuff works without a hiccup. Relax, it's only batteries! YMMV

[Dockhead]

Originally Posted by Loredo

Dockhead, let me ask you a couple questions. You've had lead batteries for your whole sailing time in the past, right? Over the years you got used to keep an (close) eye on their voltage / charge, water level? You got used to monitor them all the time? Charge them when it's timely, not over-discharge them and so on. Am I right here?

Did that lead acid battery system have all"protections" build in you're thinking about for the LFP's? What I'm wanting to bring through is this, does any system need to be build to "idiot proof standards" when there is a man with a brain behind those systems? Jedi's stuff is technically correct, yet I did not follow his line of thinking. My take is that adding all that (electronic) stuff to a system adds also possible failure points. When I started building my LFP I had not one but two BMS's fail on me within a couple weeks. Bad luck? Maybe... I ended up installing a house bank without a BMS. Don't get me wrong, my system has all the necessary fuses voltage monitors and whatnot build in. Just no automatic protections. That's what my brain is for. After a couple years with the LFP's... SWEET! I keep a close eye (less and less) on them only to find out the stuff works without a hiccup. Relax, it's only batteries! YMMV

This is a great question; highly relevant.


Jedi can give a much better answer than I can, but I'll share my thoughts for what little they may be worth.


The differences in the classical way to build a lithium system, compared to lead, are these:


1. BMS controlling charging based on much denser information than a normal charger.
2. Much more sophisticated alternator regulator, controlled by the BMS(s).

3. Cell balancing.

4. BMS able to perform low voltage and high voltage cutoff.


The reason for all this, as I understand it, is:


1. Lithium is (or was) far more expensive than lead, so you want to take less risk killing it.
2. Lithium is less tolerant to over- and under-charging, which means a solid way of measuring SOC is less optional than with lead, and you need technical means to prevent over- and under-charging.


NOW, the world has changed a bit with the appearance of LiFePo4 cells which are actually cheaper than lead batteries. EVE cells are less than €0.20 per AH (@3.2V), so €0.80 per AH @12v, about half the cost of quality golf cart batteries and a fraction of the cost of AGM.


So that means that one of the big reasons for all these elaborate measures falls away. Suddenly we can take risks like we do with lead.


So maybe really do without the BMS? You can do high- and low-voltage cutoff with the Victron battery monitors. I think you can set a good battery charger to stop charging at a conservative voltage. You can regulate your alternator without commands from the BMS. You won't balance cells, but you can do that once a year or whatever with a multimeter, right?


If you get it wrong and ruin the bank, well a whole new large bank is less than a boat buck.



Maybe really this is the optimal solution?


I'm still leaning towards a Jedi-type system because even with lead I wouldn't mind that much more control and don't mind paying for it, but maybe for most people all that is really unnecessary.

[Loredo]

My LFP "control system" consists of : BMV 712 Smart, to monitor charge level in %. I also used the BMV's relay to control a relay to switch off the battery charger at a certain voltage (I'll come back to that later.). One ISDT brand RC voltmeter to monitor the cell voltages. That one is useless since it's more often than not off by several 0.0X volts. On paper it sounded good in reality... One 30A BMS connected also only to monitor the voltages at cell level. Similar to the ISDT thinghy it's also not good enough to really see the voltages. One active cell balancer that I switch on/off manually. Finally and the most important one is the high end Fluke multi-meter to actually know exactly the voltage of each single cell. The point is, if we trust the Fluke (which is calibrated & certified) then the ISDT isn't worth the time it takes me to type it's name. The BMS is a bit better but still off enough that if I was to use it as a reference I'd overcharge some cells when going to balance them. Have you heard that? The BMS voltage reading is NOT accurate. If I were to trust it blindly I'd kill cells overcharging them! From time to time I check the voltages directly at the cells with the Fluke and compare those readings with the other two. Since my house bank ended up in 1680AH & 24V I've chosen to not install any over-discharge device other than my brain. After all, that's what I used to control the lead acid for years and I never over discharged them. Lastly, the Wakespeed external regulator on the 90A 24V alternator dedicated to charging the house bank only. I do NOT reach balancing voltage with the alternator but stop charging @ 27.6V. Works great but is a real PITA to set up because of very poorly designed HI
(Human Interface aka their software).

The most important rule to DIY a LFP house bank is to thoroughly charge/balance all the cells to 3.65V before assembling them into the final battery bank of choice. IF they are real grade A cells, they'll stay well balanced for a long time. Back to the BMV's relay for overcharge protection. Normally I keep it set to 27.6V (3.45V/Cell) that's about 80% of the capacity. When I want to balance the cells I simply change the relay voltage to 29.2V (3.65V/Cell) and turn the active balancer on if needed. Thus far, I went to 29.2V a couple times in two years, more out of curiosity than need, only to find out that the max difference between the highest/lowest cell was 0.002V as per the Fluke. Good enough, no need to balance. OK, I'm probably an outsider who likes to think out of the box but when I confront the theory with reality and they don't match... something's off. We want and need to check a one thousands of a volt with a "cheap" instrumentation like that ISDT thing or a BMS? As I suspected from the beginning, in the real world it just doesn't work. With that said, Jedi's drawings are nice but can we trust the components within the system? Me, I like my brain to do and control stuff rather than automate. YMMV

YMMV

[Loredo]

I forgot to mention another piece in my build. I also installed the manual "off" switch for the WS 500. Reasoning was "if everything goes wrong"...
Thus far, I never needed to use it and am starting to think that it was wasted time & resources. That's what happens with overthinking stuff...
Just to make clear, I'm helping a friend doing the switch to LFP on his boat.
Since he's more an "artist" than tecnical inclined, for him it'll be drop in's, DC-DC, BMV, contactors & automatic relays. How many automatic protections to build into a system depends also on who will then operate said system. Not?

[CaptainRivet]

Originally Posted by Loredo

I forgot to mention another piece in my build. I also installed the manual "off" switch for the WS 500. Reasoning was "if everything goes wrong"...
Thus far, I never needed to use it and am starting to think that it was wasted time & resources. That's what happens with overthinking stuff...
Just to make clear, I'm helping a friend doing the switch to LFP on his boat.
Since he's more an "artist" than tecnical inclined, for him it'll be drop in's, DC-DC, BMV, contactors & automatic relays. How many automatic protections to build into a system depends also on who will then operate said system. Not?

No drop ins, take EEL KIT and order cells and build battery yourself. Like this you have a dropin with 280-304AH for 600Euro, cheap with the best mosfet JK BMS available=more security, not a Basic BMS like you get when you pay 1000Euro for the same from eg Li-time, powerqueen or other budget drop ins. And you can still can access the cells if need.
No automatic protections should be the same, doesn't matter if a pro or a simple user operates the system.
Only difference a pro I would put easy bypasses so he/she can operate system outside the ultrasafe zone if necessary. Like me I bypass BMS cut offs for starter and windlass so I can use it anytime, wouldn't do that with a simple user who has no glue what he is doing.

[Nicholson58]

We’ve had total blackout under way through reefs in the Caribbean. It turned out to be an open circuit on a battery jumper on our house Firefly banks. Switching to start bank only restored power. We’ve always had Navionics on a loaded IPAD so we were back up with a chart plotter in a minute while we sorted things out. Had to hand steer for a while. It took a deep dive at anchor to find the loose connector.

We upgraded to lithium start and house in parallel but still have the ability to separate the banks. I bought a spare BMS when we made the upgrade. The Blue Heron system has been faultless.