Blackouts and Backup Comms/Nav Power

[CaptTom]

I've been giving this some thought, too. On my boat I generally start one engine off the house bank. Sure, I could go below and flip switches, but I don't often bother. The problem is, during starting there's a voltage sag to the house panel, and some things reboot. When my battery monitor reboots, I lose the accumulated SOC reading.

I've always thought isolating the navigation, comms and monitoring systems to their own "critical" bus was a good idea, but this thing with the SOC is motivating me to look at actually doing it.

Seems to me like a small LFP and DC-DC charger would do the trick. After that it's just a bit of re-wiring.

[Dockhead]

Originally Posted by CaptainRivet

Simple I have all nav electronics plus NMEA and autopilot are isolated from rest of DC by an Victron Orion TR isolated converter 12-12/30A that charges a 20AH LTO buffer battery with 14.9V which then power the electronics.. . . .

That's more or less exactly what I had in mind.

Except only that I couldn't run my own autopilot on such a small battery, so I was going to exclude that from the system.

I might go with a slightly larger battery -- say a 100AH drop-in type LiFePo4 battery. But maybe LTO is worth looking into -- more compact so maybe more flexible installation. Or maybe even an AGM lead battery would be good for this.

[CaptainRivet]

Originally Posted by Dockhead

That's more or less exactly what I had in mind.

Except only that I couldn't run my own autopilot on such a small battery, so I was going to exclude that from the system.

I might go with a slightly larger battery -- say a 100AH drop-in type LiFePo4 battery. But maybe LTO is worth looking into -- more compact so maybe more flexible installation. Or maybe even an AGM lead battery would be good for this.

LTO worth look at as
1) you can run it without BMS. I have an electrodacus BMS which can be taken off and used as 3rd backup for the house (i call this working spare) in case the house would fail and the spare too. Just needs an active balancer, which balances the cells and this happens continuously at all voltages so it can never get out of balance doesn't matter what you do.
2)LTO has 10C cont charge and discharge, so even if empty can be recharged in 10min to full or a tiny 20AH can emergency start a 50hp volvo. It's my 3rd backup, dismantled easy from nav station in 2min and used with a starter cable to start the engine.
3) LTO has 30000cycles or >50years, it will survive your vessel and can be discharged to 0V and charged backup, yes you loose 500 cycles lifespan, well you have enough....
4) can be balanced and floated (not needed but you can) or kept as is at any voltage as long as you want. 13.8V is around 80%SOC, 14.9V 90% SOC, so perfect as buffer that's kept on that 80 or 90% continously.
5)safest battery chemistry in the world, the amount you can abuse these LTO is crazy, you can even drill into them while using it. you don't want an AGM inside and at navstation that can get a runaway or gas out. Lifepo4 is also suboptimal as buffer as kept on a high state of charge at all time will shorten life drastically or when you run it lower will get out of balance over time.

6x20AH LTO SCIB cell can be ordered at batteryhookup.com for 6x18$=108$ for a 12V/14.9V 20AH LTO. For 24V you need 11 cells. A nobrainer as buffer and to start 12V engine you just add at the 6th cell a takeoff for 12V, the active balancer will fix it if used that way in emergency.
As starter you could use Alternatively to LTO a 1p4S 304AH EVE with an electrodacus BMS or a BMV712+active balancer, assume that's 12V.
With cell prices of 80Euro per EVE cell that's a very reasonable big capacity backup.
I went with 60AH LTO instead as I like it's reliability and robustness, I know that's always there for me when **** hits the fan plus this combo can do 600A cont. and 1200A peak so handles everything you throw at it.

[rslifkin]

Originally Posted by Dockhead

That's always been my plan. I carry jumper cables (and flashlights ) in the compartment where the engine/gen start battery box is located, which is conveniently next to the bus bars for my electronics.



Never needed them in 15 years using this boat. Knocking furiously on wood.

My thought is that you're unlikely to need them. With a decently designed electrical system it should be pretty hard to completely lose house power in a way that can't be recovered by disconnecting or bypassing a failed component or something simple. Ending up with degraded capability can happen, but a total failure of a well designed system generally means that you've got some serious problems (likely extending far beyond just power problems).

And my setup is generally similar to what you describe of a house bank and 2 start batteries. In my case, I have 2 engines and a gen and 2 start batteries, so each engine (and the gen) has a switch to select which start battery it uses (normally port engine uses battery 1, stbd and gen use battery 2).

In my case, the charger for the start batteries has a 3rd output. It's wired to the house bank, but with the breaker left open. So for a failure of the Multiplus on my boat, I could bypass it for AC power from the gen, and close the breaker to allow the start battery charger (possibly with a few settings changes) to feed some power to the house bank (assuming I really needed AC charging and wasn't fine with solar and alternators).

For critical electronics, a buffer battery is one way to do it, but I kinda like the diode combiner method mentioned earlier in this thread. It's a pretty simple, elegant failover transfer switch in my mind.

I also figure that I have cell phones, a laptop with a GPS puck, and a handheld VHF on board, so even if I lose all nav electronics I have some self sufficient alternate options to use while I work on the power problems.

[CaptainRivet]

Originally Posted by rslifkin

My thought is that you're unlikely to need them. With a decently designed electrical system it should be pretty hard to completely lose house power in a way that can't be recovered by disconnecting or bypassing a failed component or something simple. Ending up with degraded capability can happen, but a total failure of a well designed system generally means that you've got some serious problems (likely extending far beyond just power problems).

And my setup is generally similar to what you describe of a house bank and 2 start batteries. In my case, I have 2 engines and a gen and 2 start batteries, so each engine (and the gen) has a switch to select which start battery it uses (normally port engine uses battery 1, stbd and gen use battery 2).

In my case, the charger for the start batteries has a 3rd output. It's wired to the house bank, but with the breaker left open. So for a failure of the Multiplus on my boat, I could bypass it for AC power from the gen, and close the breaker to allow the start battery charger (possibly with a few settings changes) to feed some power to the house bank (assuming I really needed AC charging and wasn't fine with solar and alternators).

For critical electronics, a buffer battery is one way to do it, but I kinda like the diode combiner method mentioned earlier in this thread. It's a pretty simple, elegant failover transfer switch in my mind.

I also figure that I have cell phones, a laptop with a GPS puck, and a handheld VHF on board, so even if I lose all nav electronics I have some self sufficient alternate options to use while I work on the power problems.

Agree on that.
The huge advantage with a buffer battery and charged with an isolated DC2DC converter or charger is that you completely isolate all the senstive electronics from the dirty DC of the boat...yes it's dirty and getting more dirty with ripples of inverters, big alternators....and on the other hand compare the filtering and power supply of a 15 years old chartplotter or radar and today's of the big 5 and the shows you without any doubt you need an isolation as filtering is basically inexistent and the power supply is weak and saved to death by controllers. One if the main reason axiom, Zeus3 ...plotters and Quantum radars die like flies, non that have an isolated buffer have problems on the hardware side.with them.
So the buffer solution catches 2 bunnies at the same time.

[Kettlewell]

My philosophy is that I don't want to have to dismantle anything or use jumper cables in the dark on a bouncing boat with foggy brains addled by the hour and the problem. A switch or foolproof multiple switches that can be flipped are better, but in the meantime I also want to be able to navigate and proceed with nothing working properly in the main electrical system. It is very easy to make a wrong move once problems start cascading one on top of the other. First the nav stuff goes black, then you realize you can't start the engine, then you find the battery cable is too short, and you can't remember which fuses are for 12-volt LA and which are for the LFP side, etc. etc. Make it as idiot proof as possible or Murphy takes over.

[barnakiel]

So you do not have two battery banks ?


In our boat, should the main bank die (unlikely, as I use multiple batteries), I will just disconnect the house bank and connect the engine battery to any instrument that I think I might want to use.


Btw our gps unit is AA based (and plugged into 12V) so should the boat electric fail, I still have the gps data and basic plotter available over some 10-20 hours (continuous, a couple of days, if I switch off between checks).


And with a box of AA batteries in the locker I can cross any amount of water just like that (while sorting out the house battery mess).


b.

[SailingHarmonie]

There are two separate issues here, and it is interesting how some people can only think of one at a time.

First, is can you jerry-rig a way of getting home after a failure. In almost all cases, the answer is at least a qualified YES. Given enough knowledge and skill on board, you can jumper around almost any single point failure. This does not really concern me.

The other issue that is far more important to me is the consequences of a single point failure at the worst possible time, and the likelihood of that. (Anybody here thinking of a bridge in Baltimore?)

To me, the design of Li battery systems are more reliable overall, in the long run, but also instantaneous failure of electrical power is also more likely than with a LA system. There are just MORE single points where an instantaneous failure is possible (even if unlikely).

Almost all failures in a LA system are slow moving. With a well instrumented system they should not catch a knowledgeable boat owner by surprise. With modern monitoring systems there is no excuse for a shorted cell to kill a bank, for example. This of course does not apply to poorly instrumented systems, or systems run by people who are ignorant of the clues to pending failure.

I know of three boats that have had total electrical failure with Li systems that were unpredictable and unexpected. All were able to be fixed or jumped around. But that really is not the point. In many cases a total electrical shutdown at an inopportune time can have serious consequences. I know of no boats that had sudden failures from a LA system that could not have been predicted ahead of time and prevented by good system monitoring.

[Dockhead]

Originally Posted by SailingHarmonie

. . . I know of three boats that have had total electrical failure with Li systems that were unpredictable and unexpected. All were able to be fixed or jumped around. But that really is not the point. In many cases a total electrical shutdown at an inopportune time can have serious consequences. I know of no boats that had sudden failures from a LA system that could not have been predicted ahead of time and prevented by good system monitoring.

This is exactly why I have been thinking of this.

[CaptainRivet]

Originally Posted by SailingHarmonie

There are two separate issues here, and it is interesting how some people can only think of one at a time.

First, is can you jerry-rig a way of getting home after a failure. In almost all cases, the answer is at least a qualified YES. Given enough knowledge and skill on board, you can jumper around almost any single point failure. This does not really concern me.

The other issue that is far more important to me is the consequences of a single point failure at the worst possible time, and the likelihood of that. (Anybody here thinking of a bridge in Baltimore?)

To me, the design of Li battery systems are more reliable overall, in the long run, but also instantaneous failure of electrical power is also more likely than with a LA system. There are just MORE single points where an instantaneous failure is possible (even if unlikely).

Almost all failures in a LA system are slow moving. With a well instrumented system they should not catch a knowledgeable boat owner by surprise. With modern monitoring systems there is no excuse for a shorted cell to kill a bank, for example. This of course does not apply to poorly instrumented systems, or systems run by people who are ignorant of the clues to pending failure.

I know of three boats that have had total electrical failure with Li systems that were unpredictable and unexpected. All were able to be fixed or jumped around. But that really is not the point. In many cases a total electrical shutdown at an inopportune time can have serious consequences. I know of no boats that had sudden failures from a LA system that could not have been predicted ahead of time and prevented by good system monitoring.

Let me guess that 3 boats had fairly complex system, it's not lithium itself but an overcomplicated install in 95% of the cases that was not installed and/or speced properly.
Keep things simple and you don't have a problem.
If your lead system didn’t have a problem, you don't have a problem with Lithium either when you see the cell values...in most cases if you do it's chinese surprise boxes without any communications that didn't have a good top balance and where charged to 13.8V (because recommend often) with minimal absorption and ran completely out of balance because the owner cannot realized that and got a complete shutoff.

As backup an LTO buffer is a simple and multipurpose even without flipping switch you are not in the darkness and fully operational even when the house has a blackout plus you protect your senstive electronics.

[CaptainRivet]

Originally Posted by CaptTom

I've been giving this some thought, too. On my boat I generally start one engine off the house bank. Sure, I could go below and flip switches, but I don't often bother. The problem is, during starting there's a voltage sag to the house panel, and some things reboot. When my battery monitor reboots, I lose the accumulated SOC reading.

I've always thought isolating the navigation, comms and monitoring systems to their own "critical" bus was a good idea, but this thing with the SOC is motivating me to look at actually doing it.

Seems to me like a small LFP and DC-DC charger would do the trick. After that it's just a bit of re-wiring.

You have a serious problem if the voltage sags during starting on a lifepo4 house that things like a battery monitor reboots. Should never happen even at 10% SoC.
You need to find the root cause of that asap as this could lead to fire, this is serious issue. And before adding anything, it's definitely either an out of balance battery or a damaged cell or a high resistance caused by I assume bad contact or multiple. Start with battery terminals, bad cable crimp, not properly torqued down, fuse terminals, bad quality cable fuse, if DIY too small busbars and/or bad contact to cells.
Bad cell or imbalance, look at the battery voltage: is one cell peaking or crashing. If you don't have access to cells, charge to 14.4V with 2h absorption: at what voltage does the battery cut charge, does it even reach 14.4V and if not at which voltage does it shut off charging.
Or your starting with a LFP battery that's too small/too less current capability, how much capacity does the bank have, which manufacturer/model and how many watts has the starter?

[CaptTom]

Originally Posted by CaptainRivet

You have a serious problem if the voltage sags during starting on a lifepo4 house that things like a battery monitor reboots...

I never said anything about an LFP bank.

[Dockhead]

Originally Posted by CaptTom

I've been giving this some thought, too. On my boat I generally start one engine off the house bank. Sure, I could go below and flip switches, but I don't often bother. The problem is, during starting there's a voltage sag to the house panel, and some things reboot. When my battery monitor reboots, I lose the accumulated SOC reading.

I've always thought isolating the navigation, comms and monitoring systems to their own "critical" bus was a good idea, but this thing with the SOC is motivating me to look at actually doing it.

Seems to me like a small LFP and DC-DC charger would do the trick. After that it's just a bit of re-wiring.

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.

[Kettlewell]

Bottom line is that anything critical to vessel operation must have multiple backup systems independent of each other, and I put navigation into that category. When, not if, something goes wrong with your electrical system you must have a way of knowing where you are that does not depend on the boat's main electrical system, and it must be instantly deployable. Some fogbound passages in Maine come to mind. Rocks on either side, current sweeping through, can't see the bow of the boat, too deep to anchor--I don't want to have to go below and be fiddling with anything in order to get a chart plotter working again.

[Dockhead]

Originally Posted by Kettlewell

Bottom line is that anything critical to vessel operation must have multiple backup systems independent of each other, and I put navigation into that category. When, not if, something goes wrong with your electrical system you must have a way of knowing where you are that does not depend on the boat's main electrical system, and it must be instantly deployable. Some fogbound passages in Maine come to mind. Rocks on either side, current sweeping through, can't see the bow of the boat, too deep to anchor--I don't want to have to go below and be fiddling with anything in order to get a chart plotter working again.

Certainly a good idea -- why does no one have the GMDSS mandated system?


I've never had a blackout in nearly half a century of cruising, but never say never, right?


I'm not that fussed about the chart plotter -- sailed for many years before they were invented. But RADAR -- yes, I would really hate to lose that in a situation like you describe. Or depth. And certainly -- radios. Which is where the GMDSS requirement came from.


Thinking about this now. I'm thinking more and more that since this is just backup and so the reserve batt will always be fully charged, that this is maybe a job for an old fashioned lead battery, charged with a small DC-DC charger.


It's not quite as dead simple as I dreamed about because you would want a monitor and possibly an alarm for it. You'd want to be able to check at a glance that the reserve batt is in fact fully charged, and you would want to be able to test it.


Maybe a simple voltmeter is all you would need, and a switch to switch the charger on and off. So you could periodically switch off the charger and be sure that the reserve system is working.


Systems I would run from this:


1. VHF.
2. SSB.
3. Nav lights.
4. NMEA2000 network.
5. Power supply to other nav gear.
6. a bilge pump?



SSB is complicated because one 12v lead battery is not optimal for that power draw. I power my M802 using a 24-12v dropper which works brilliantly because it provides 13.6v no matter what the amperage is. Maybe I would leave the SSB connected like that and add a changeover switch to the emergency system -- ekh, complication.


Another possible approach specific to me boat: I could leave one of my two existing lead banks in place -- I don't need the space for lithium, which fits in one of my two battery boxes. That's about 260AH * 24 of golf cart batteries. And then just leave the entire DC panel connected to that. Charge it with the appropriate DC-DC charger from the lithium bank. Big plus of this is that it would require almost zero reconfiguration of anything. Another is that it adds that much capacity. On the minus side, with more things attached, there is more to go wrong. Also minus -- weight and bulk.