Comments on my 12v wiring upgrade?

[Cpt Pat]

Well thought out and clean design.

I never take my LFP batteries below 12.7 volts terminal voltage, which under my normal loads equals 15% SOC.

Once your LFPs reach low voltage cut-off (LVCO), all power is lost on the bus in your design. You can switch to your starter bat, but the abrupt loss of power may cause all sorts of momentary problems: rebooted chartplotter, loss of radio comms, reboot of your radar, stoppage of your windlass, fumbling around below to find the A/B switch in utter darkness, etc. You may want to consider connecting a smaller AGM in parallel to prevent the sudden LVCO issue. I would place it physically as close as possible to the windlass to supplement its power and reduce voltage drops to that motor.

Ordinarily, the AGM won't do much since the LPF voltage is above its 12.6 volt nominal voltage. It should last a very long time.

Alternatively, I'd install a "battle lantern" in the cabin to provide light if the LVCO occurs in darkness.

Murphy's Law dictates that you will have a LVCO event in the moonless dead of night immediately after your anchor is unset in a windy crowded harbor while running your windlass.

[john61ct]

Originally Posted by Q Xopa

I dont know if limit max current is the intended 'central reason'. I would say it is the design and manufactures limitation.

When the **problem** is that a LFP bank is trying to pull much more current than the source can safely supply,

then the current limiting **solution** must come from somewhere.

A DCDC charger is one such solution fot that problem.

Needing more Ah per day is a very different problem

[rgleason]

I would prefer "more amps" from the externally regulated alternator, after de-rating the alternator by 15% for longevity and another 15% for heat. Ideally I would like to be able to charge the LiFePo during 2 x 45 minutes to and from harbor, but being more realistic, at .25 to .35C depending on the circumstances, to bring the batteries up to 90%. The major change would be the LiFePo chemistry which actually prefers not being topped off at 100%, which matches my cruise/mooring use much much better. My ideal configuration would certainly include solar panels as well. Dock dwelling is a different story. You really don't need any of it.

Originally Posted by john61ct

Yes, exactly.

If you needed more, they can be stacked.

Some members feel the need to push for "get all the amps out of your alt as fast as possible", or even "upgrade the alt, moar amps!"

But it all depends on your usage patterns and energy budget, Ah per day in / out balance as to which approach is more cost effective for **your** use case.

[SpaceRnglr]

Originally Posted by bcboomer

I expect the 650 watts of solar is all that is needed for most of the time.

Bingo. Since the boat isn’t even fully equipped 650 watts of solar is frankly overkill. Once we fit it out with water makers, washing machines, and an inverter I thing I will start to use a bit more of that power. If it’s not quite enough I could add another panel with some difficulty... Regardless the plan is to never run the engine just for electricity, but it is a good backup. One of the major reasons of LFP is the round trip efficiency being so much better. That’s especially important when power comes from solar.

I confirmed today there is another bus behind the 12v panels that the windlass connects to. I will upload the updated diagram tomorrow.

[KP44]

Originally Posted by zboss

The internally regulated alternator will burn up pretty quickly driving lithium batts and it may not match the charge voltages needed by the lithiums.

Add a much higher output alt, get an external regulator, and attenuate the field.

I use the original alternator as a completely separate system dedicated to my engine battery. The 150 amp alternator is a dual-belt and takes care of the house bank, using an external regulator.

I agree that the windlass (and inverter) must not go through the breaker panel, but have their own circuits with their own breakers. (Or fuses. I use big breakers.)

[SpaceRnglr]

OK, a few more updates.

We went for our normal Sunday sail this weekend and when we got to the boat the house bank was a 9.2V--yikes! I new the batteries were on their last leg, but i thought i would get a few more months of light use. So that means I am bumping this project to the top of the list and will be ordering parts, including the LFP batteries, this week.

I also checked and there is a small bus behind the main 12v panel so the diagram is updated accordingly.

The only remaining undecided point for the system is where to connect the alternator. The general advice from everyone is to get more than 60a from the alternator. I tried calling Beta Marine last night to ask if I can externally regulate my 1.5 year old 120a alternator that came with the engine. I they convince me it is possible / easy I may buy the Balmar regulator and move the alternator to the charge bus. If I do that, i would likely buy this B2B trickle charger to keep the start battery topped up from solar. I am still undecided on this point. here is the trickle charger in question, in case anyone has experience. https://www.amazon.com/Tecmate-Optim...ustomerReviews

[TassieBloke]

Nice layout.

I think you might need to revisit the load bus/battery selector sizing. You have indicated a future inverter, but have limited the size to 200amp at the load bus. This translates to max size of a 3.5kW inverter. Since you intend to go LFP, is this going to be large enough? Lets say you decide on a total of 5kW = 415A, which overloads the rating of the bus and battery selector switch.

If you intend to remain under 3.5kW, then its all good.

I also agree with the comment of removing the direct feed of the windlass from the Dist. Panel. I would also suggest a fuse/switch after the bus somewhere accessible for windlass so you can isolate it. You don't want to blow the main 12V fuse if you overload the windlass and lose all 12V supply when you are trying to reset the anchor in nasty weather.

Good luck with the project

[wingssail]

Originally Posted by SpaceRnglr

OK, a few more updates.

We went for our normal Sunday sail this weekend and when we got to the boat the house bank was a 9.2V--yikes! I new the batteries were on their last leg, but i thought i would get a few more months of light use. So that means I am bumping this project to the top of the list and will be ordering parts, including the LFP batteries, this week.

I also checked and there is a small bus behind the main 12v panel so the diagram is updated accordingly.

The only remaining undecided point for the system is where to connect the alternator. The general advice from everyone is to get more than 60a from the alternator. I tried calling Beta Marine last night to ask if I can externally regulate my 1.5 year old 120a alternator that came with the engine. I they convince me it is possible / easy I may buy the Balmar regulator and move the alternator to the charge bus. If I do that, i would likely buy this B2B trickle charger to keep the start battery topped up from solar. I am still undecided on this point. here is the trickle charger in question, in case anyone has experience. https://www.amazon.com/Tecmate-Optim...ustomerReviews

You are pretty far along in this design and have had a lot of useful comments so I can't really add too much, however, I do not see how you would be able to direct the charge current to a specific bank, in an exceptional situation. Example: Say, for whatever reason, your batteries are all completely discharged, (careless switch setting left for a day or two) and you want to put all your solar into the start battery in order to get your engine going. What do you do to keep the solar from going into the house bank?

[john61ct]

Such events do not require investing in automated solutions.

Accommodate them by designing so manual intervention works,

and put more effort in systems design and owner behaviour to prevent such mishaps.

In a healthy well maintained setup Starter very rarely gets discharged lower than 3-5%, and IMO nothing should rely on memory

[ashmun]

Hello SpaceRnglr,

very cool diagrams with a ton more detail and excellent fusing! Since you asked and in fairness having jus taken a quick look before I run out the door, here are a few items to consider:

1) It appears from the diagram that the charge bus fuses are closest to the batteries instead of closest to the source of current to protect wire run. If this was just to fit it all into a one page diagram, no worries. Otherwise, Over Current Protection (OCP) should always be at the charging source and adequate to prevent the wire from catching fire from an overload, chafing, short or other damage.

2) Installing Class T Fuses (300 Amp / BlueSea #5119) with 20,000 Ampere Interrupt Capacity (AIC) near the batteries or MRBF on each battery to protect all of the fuses or circuit breakers downstream that have low or no AIC rating. The electric system on older boats were designed for wet cell batteries (180amps +/-) and most of the circuit breakers and fuses (e.g. ANL, Megas, etc.) can not handle a short-circuit from non-wet cell batteries. For a example, my Victron 200amp AGM’s have a short circuit ampere of 6,000/ea on a house bank of three. That's 18,000 short circuit ampere (aka dropping a wrench on the terminals, cable chafing or as I’ve recently seen, a 2” screw drilled through the rub rail into the back of circuit panel (vs correctly sized bolt). The short circuit ampere of my AGMs exceed an arc welder and can jump ANL fuses and melt circuit breakers. A simple Class T Fuse* ($36-44) mounted upstream will near the batteries to protect all of the fuses or circuit breakers downstream. Nigel Calder’s latest edition of Boatowner’s Mechanical and Electrical Manual has tons of Over Current Protection (OCP) and AIC information. And Marine How To (aka Compass Marine/pbase) has several excellent articles on the topic: https://marinehowto.com/lifepo4-batteries-on-boats/ and https://pbase.com/mainecruising/battery_fusing, and https://marinehowto.com/battery-melt...rowly-averted/.

3) Instead of the A/B/both switch, have you considered a surface mounted Marinco/BEP MC10 Pro Installer 400A EZ-Mount Dual Bank Control Battery Switch or surface/panel mounted 772-DBC. This 3 in 1 switch (aka House, Start, and Emergency Parallel) saves space and install time. We really like the BEP Pro Installer Series which uses bars instead of cables between products. Here is a link to the hard to find PDF on the BEP Pro Installer Series.






4) On the inverter, you need an isolation switch (for safety and maintenance) and a chassis ground that is one size smaller then the negative cable. If you use the Pro Installer Series battery switch, you can add the inverter Key (on/off) switch.

5) I strongly recommend having properly placed battery temperature sensors on all charging sources (e.g. alternators, charger, solar controller, etc.). As a side note, We’ve been really happy with our Victron inverter/charger and battery monitor with Blue Tooth (BT) communication to our iPhones. We found the inverter/chargers to be a cost saving over purchasing separate inverter and charger.

6) And if you don’t already have an marine DC Wire Sizing app that follows ABYC and/or ISO, take a look at Circuit Wizard (free), Wire Sizer ($0.99) and DC Wire Sizer ($2.99), the latter two save the wire runs and the last can email/export wire run(s) and has an 85 page Technical section.

Again, excellent fusing!

Cheers,
Julia
s/v Esprit, Mariner 39cc

* Note: Class T fuses do not have an ignition protection rating

[SpaceRnglr]

Ashmun - some great comments, thanks! Let me take this step by step to pick your brain a little more.

Originally Posted by ashmun

1) It appears from the diagram that the charge bus fuses are closest to the batteries instead of closest to the source of current to protect wire run. If this was just to fit it all into a one page diagram, no worries. Otherwise, Over Current Protection (OCP) should always be at the charging source and adequate to prevent the wire from catching fire from an overload, chafing, short or other damage.

I am struggling to follow this point. I plan to put the fuses closest to the largest source of current. The battery has the ability to put much more current into the wires than any of the charging devices--I thought the right approach was to put the fuses near the highest source of current. Did I get this wrong?

Originally Posted by ashmun

2) Installing Class T Fuses (300 Amp / BlueSea #5119) with 20,000 Ampere Interrupt Capacity (AIC) near the batteries or MRBF on each battery to protect all of the fuses or circuit breakers downstream that have low or no AIC rating.... The short circuit ampere of my AGMs exceed an arc welder and can jump ANL fuses and melt circuit breakers. A simple Class T Fuse* ($36-44) mounted upstream will near the batteries to protect all of the fuses or circuit breakers downstream.

The Winston cells I bought are capable of max current of 4,000a. You are right that the AMG fuses I was planning to use are limited to 2,000a Interrupt Capacity. I need to get the battery in it's home to see if I have space for a MRBF. Thanks for catching this.

Originally Posted by ashmun

3) Instead of the A/B/both switch, have you considered a surface mounted Marinco/BEP MC10 Pro Installer 400A EZ-Mount Dual Bank Control Battery Switch or surface/panel mounted

Nope, but those sure look nice! Parts already ordered so I guess that will have to wait for my next boat... My plan was to reuse my 1-2-Both switch, but when I took it off last week I noticed it's amp rating is lower than my system. As a result, I have added 3 on/off selectors that will all be panel mounted with the connections behind. That is also shown on the updated diagram.

Originally Posted by ashmun

4) On the inverter, you need an isolation switch (for safety and maintenance) and a chassis ground that is one size smaller then the negative cable.

Noted. An inverter will be phase 2 of this project. The biggest single problem I have is where to mount it but regardless these are good comments. TassieBloke also pointed out my fuse may be too small, but as of now I am thinking I will go for an inverter <2kW so I think I am OK. I did switch the Load Bus to AMG fuses so can increase to 300a if I need to.

Originally Posted by ashmun

5) I strongly recommend having properly placed battery temperature sensors on all charging sources

All chargers will have temperature sensors--too many wires to show on the diagram...

Thanks for the wire sizing apps. I have just been using Blue Sea's web table but haven't ordered wires yet. I will check these out before finalizing.

I have created another iteration of my diagram. The main changes are I have removed the B2B charger as I think I want to externally regulate my alternator and connect it to the charge bus. I called Beta and while they don't sell a conversion kit, they did confirm my alternator is a Iskra 120a AAK3847. The local alternator shop says they can convert it. Either way, the external regulator appears to be a little more complex so will have to wait until later this year. In the meantime the ~700w solar will be plenty for my coastal cursing so the alternator is only charging the start battery.

Wingssail also had an excellent comment that if the BMS cut off the charge or load bus for any reason I would lose all charging to the start battery. If there is a fault in the house bank causing low voltage cutoff I might still want to run loads off the start battery and use the various charging sources to provide the current. To allow for this I have added a third battery switch to isolate the house bank, a general positive bus, and 3 way switches for the 2 isolation relays. Normally the three way switches are in auto mode to be powered by the BMS. If the house bank goes haywire I can isolate it with the manual switch, then activate the relays in "manual" mode giving a fully functional positive bus with all charging and loads connected to the start bank. This also has the added benefit of giving me a very easy switch to turn off the load and / or charge bus when I leave the boat, a useful feature since I am on a swing mooring and only using the boat on the weekends at the moment.

This drawing is starting to look rather complex, but any further comments appreciated.

[bcboomer]

You're on the right track and correct in your fuse placement and switch choices. Try to find room for better fuses because that's a lot of juice if the fuse doesn't break the connection.

[Peeew]

I did add a Balmar external regulator to my 120 amp alternator. I am new at all this and it only took an hour or so to do it. Seems worthwhile.

[rgleason]

Yes, true John.

But lifepo batts have high acceptance and would allow a larger properly engineered alternator, ext regulator to recover daily ah in much less engine run time, rather than limiting the charge rate to 60amps with the Sterling dc to dc charger.

I realize that this arrangement is more appropriate to a good powerful solar charging setup where the 60 amps Sterling does not limit the output off the panels, and losses are limited, depending on how they are connected.