Transition to LFP house bank

Boat Systems
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I did a 40 nm engine mount checkout voyage which went really well in terms of mounts and exhaust plumbing. However, I did experience a broken alternator bracket which was completely unrelated to the mounts and easily fixed. I also spent a night at anchor during which I realized my two 110AH house AGMs were compromised to the extent the bank would only deliver about 50 AH.

I did not spend a lot of time troubleshooting. I bought cheap AGMs a couple of years ago with the thought I would be upgrading to Lithium at some point in the future when I got up enough courage to face this new technology. Yea, I know, it’s not new, but it is to me. So that point has now arrived.

Anyway, to celebrate the end of the engine mount saga I decided I would launch into a house bank LFP upgrade, how hard could it possibly be? More famous last words have never been spoken :rofl:

So I bought an Ecoworthy 280 AH LFP battery. It is a cheap LFP but a fellow on YouTube I respect (Will Prowse) tested and tore one down to look at build quality. He gave the battery a thumbs up in the “cheap LFP” category.

Standard LFP batteries are not good start batteries (although they have been used to start) so I kept my old AGM start which was still in pretty good shape.

Since only my solar controller charge source had a Lithium profile I connected this directly to the LFP battery. I connected shore power and regulated alternator to the “charge bus” which charges the AGM start and also provides power to a Victron DC to DV charger which converts the AGM charge profile input to a LFP appropriate charge profile. BTW, the Victron can be configured for a variety of chemistries. It also has Bluetooth which allows this configuration to be done from the phone. The Ecoworthy battery also has Bluetooth. I downloaded the “overkill solar” app to access the battery and the integrated Battery Management System (BMS) so I can see all the BMS settings, cell voltages and so on. It is a real game changer in terms of visibility into what is happening with your batteries.

Anyway, I got it all put together and, after a week, I think I am sneaking up on an understanding of how it all works, Especially the charging and cell balancing element which took some serious time staring at what was happening with cell voltages as I applied charge current , did a discharge session, rinse and repeat about twenty times.

One thing I found is that there is an incredible amount of BS flying around regarding LFPs. There are a lot of amateurs (like me) pontificating without having a clue what they are talking about. Warning issued.

So I have completed testing on shore power and solar charging, They work, I have not tested alternator charging yet. That will be a biggie. One sweet thing about the Victron is that its max current transfer is 50 amps but it can be throttled all the way to zero in 1/10 amp increments. This is important because one feature of the LFP battery is its ability to accept a LOT of current for a long time. I have a 125 amp alternator on a serpentine belt but my alt probably will not like running at a constant 50 Amps for 5.5 hours while the LFP charges. I do have a belt manager on the Balmar ARS regulator so I have a second way to reduce alternator output but that requires some hands on work with the regulator while the Victron config is just an app away.

One new concern with LFP is the presence of the BMS. This electronic device (in my case embedded in the battery case) monitors temp, input and output voltage and current and cell balance (and probably other stuff) constantly. If it detects a fault in any of these parameters, it will shut the battery down until the fault is cleared. Now this is an interesting feature. I can remember a time approaching Pillar Point Harbor in the fog at midnight. If I had had LFP and the BMS had decided this would be a good time to dump the battery that would have been interesting. I do have a backup plotter on internal battery but everything else goes dark. I have to figure out a way to switch the +Bus to the AGM battery in an emergency.

I realize I am babbling but I thought I would keep you all updated on how this goes.

Some interesting LFP related links:

Will Prowse videos/battery reviews ++

https://www.youtube.com/results?search_query=will+prowse

DIY Solar forum (has a Marine category + much good info/resources)

2 Likes
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OK, have done a little cruising with my new LFP battery online and I am very happy.

I literally spent 5 days at anchor, freezer on full time. Depth and wind on 24/7, laptop charging, tablet/phone charging, anchor light etc. and only my 200 watt panels for charging the battery. Best I can get out of the panels is around 160 watts. I left the Anchorage with more power than when I arrived.

Extremely pleased so far

For emergencies ( for example. LFP drop due to internal BMS detecting problem) I have a strategy to quickly reconfigure to run all loads on my 100 ah AGM.

Took a while to sort out the new charging requirements and unique characteristics of LFP batteries but I made some progress on this and so far this system has been fantastic.

LFP batteries charge more efficiently than AGMs do and this may account for my experience at anchor. Alternatively my AGMs were just ready to give up the ghost…don’t know. Either way the LFP has been a big improvement. Overall project cost was about $800.00 + sweat equity. Weight reduction of about 100lbs and a lot more room in my battery box.

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This is great to hear Mike, as I am in the process of updating my AGM’s to a new engine AGM with a parallel pair of new 100AH Li batteries. I’ve been using 200W of solar with a pair of aging 6v 200AH AGM’s for the past 2 years and while it worked pretty well, the effective 100AH would be marginal during a cloudy spell with the fridge running full time.

This year I’m adding a DC-DC with an input for both the alternator and a dedicated 100W solar panel for the AGM. Once fully charged, that will then be delivered to the house bank.

I’m also adding a small 1000W inverter for occasional AC needs.

Your results are encouraging!

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I think you will be surprised at how well these things work. The only downside, and it is not that far down, is you do have to rethink the configuration and have little different mindset re charging, But no big deal, esp. since this tech is quite interesting and well worth the effort if my initial experience is any indication.

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Nice job Mike. I did a conversion three years ago with three Victron 200Ah LFP house batteries and have been thrilled with the results. I have an AGM starter battery. I do not have Solar, but I anchor out for several days at a time. I have a 250 amp alternator which charges the system very well. I can anchor out 3 to 4 nights with my 14’ fridge/freezer cooled by a Fridge O Boat refrigerator, running all the lights, computers, and everything else we use. I rarely let the system go down below 50% charge… I commonly do run the engine every other day or so to heat up hot water. It does not need to be charged over the winter because LFP batteries tolerate cold very well. I had mine installed professionally, which was quite expensive, but it works great.

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I have been really happy with Victron equipment, if you are willing to add some computer networking to your setup, the VenusOS running on a RaspberryPi really has some value added features.

You will need:

  • WiFi/networking router
  • Raspberry Pi (see docs for which ones are supported)
  • Victron Energy VE.Direct to USB Interface, enough for 1 per Victron device
  • Victron Energy Interface MK3-USB (VE.Bus to USB), if you want to connect a Victron inverter/charger to the rPI

Victron also offers their VRM cloud system, which the VenusOS can be configured to push up the status of the devices, assuming your router has access to the internet, and you can check the VRM status from the phone app locally or remotely. You have to be comfortable with sending that data into their cloud servers, but its very convenient to know the status of your batteries/solar/etc while away from the install.

Raspberry Pi Install Venus OS Instructions

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Shoes,

Yes one can really do some nice stuff with these systems. Remote visibility is really an interesting capability. The visibility/configurability is a game changer even for my setup.

I have to admit though, I purposely tried to keep my system dead simple until I had a good grasp of what I have and how it works in varying conditions. After a few more trips I will be looking to add features. I do have the advantage of having my boat in a backyard slip and I am down there a lot. But I am on travel now and It would be very nice to peek at the system remotely from time to time . I have access to my home internet mesh from the boat so that simplifies things while I am docked at home.

I will refer back to your recommendations as I move forward…great, more projects

1 Like
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I just did a lithium upgrade on my F45, taking out 3x8D AGM and replacing with 2xEpoch 460Ah batteries.

Charging is done by 340 watts of solar running through MPPT, a 135amp Maxpower alternator with Balmar MC-618, and Victron Multiplus II 12/3000 inverter charger. Added a smart shunt, Cerbo GX, and touch 50 display. It’s a huge improvement over the old system.

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@LanceRyley

I have a few questions about your setup. What do you have for a starting battery ? Does the alternator charge both the house and the starting battery? Does solar just go to house bank?

Did you have to program the regulator or was it ready to do lithium? Is the regulator setup to handle a Lithium BMS shutdown with potential risk to alternator ? Do you have an alternator temp sensor? Any dc to dc charging?

Any chance you have a diagram?

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Just another note for completeness on my basic setup. I did decide to buy and install a Balmar alternator protection device. I thought it wise to protect against an inadvertent battery switch when ALT is outputting high amps. Given my setup, I do not believe a BMS trip would damage the alternator due to the AGM shock absorber on the charge bus. But I am prepared now to be wrong.

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Start Battery is a spiral top AGM.

Alternator charges the house bank directly, and the start battery through an Orion XS 50.

Solar is through Victron MPPT controllers directly to the house bank.

The regulator for the alternator is a balmar MC-618 which has a compatible lithium program. I have a cutoff absorber, but I’m not too concerned about a BMS shutdown because the charge voltages are generous for the epoch battery expectations.

I absolutely have an alternator temp sensor. According to Balmar it starts reducing field at 100c. So far I haven’t seen anything close to that. I have a diagram but I need to update it and will post it once I do.

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Some pics of my battery set up aboard my mull 30.

Some may question my decision not to install a battery box but I have seen these torn down and the black box you see is, in fact, a box which encloses the LFP cells and BMS.

Recently I installed the battery terminal fuse after learning this was a must have. I do have 60 amp breakers on both input and output of the battery

The battery sits atop a small bench I built and epoxied to the hull. I used a ratchet strap to lock the battery in place. It weighs about 45 lbs.

I will be fabricating an acrylic window to stand off in front of the breakers along with a 3/4 surround wood frame to keep anything from unintentionally contacting breakers or cables.

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I have a muffin fan above and not in pic to circulate air over cool, below waterline, hull interior during hot weather. The battery is located in the bottom of the aft cabin hanging locker which I have turned into an electronic equipment cabinet.

The three breakers are DC to DC charger in, DC to DC charger out to batt and batt out to house bus. As mentioned, there is also a 100 amp fuse directly in the positive terminal of the LFP which can be seen in pic.

The solar is connected directly to the house bus for LFP batt charging. The DC to DC charger input comes from the charge bus and is fed by the shore charger at the dock or the balmar regulated alternator underway. My AGM start is also connected to the charge bus.

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Having just done this on my boat, you’re fine without a battery box as long as the batteries can’t move. It’s not like with flooded cells where you could end up with corrosive electrolyte everywhere if the battery fails.

A T-class fuse within 7" of the positive terminal is an ABYC must. Also, your wiring seems undersized for the size of that battery. It looks like you have only one battery but if you add a second, the positive connecting wire must be fused as well, but it can be an mrbf and doesn’t have to be a t-fuse.

I designed my system, installed it, then hired a marine electrician to inspect it and make recommendations. Definitely worth it, especially since my insurance company had specific requirements about the lithium upgrade.

Your installation looks really clean, but definitely examine your wire size.

Yahoo Mail: Search, Organize, Conquer

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Lance,

Yes, that is why I recently added the fuse. I had read this is an ABYC requirement and the explanation and realized I needed to add the fuse.

With regard to wiring, this is exactly why I have 60 amp breakers installed. I carefully reviewed my power budget and could not find a situation where I would be drawing more than about 20 amps. I will not be using this system in conjunction with a 110 vac inverter or other high loads. My shore power charger maxes out at 20 amps and I have my regulator limited to 40 amps. Although the victron is capable of 50 amps, I have been using a max 30 amp output. Combined with solar charging the worst case input to the batt would be about 55 amps with engine running, victron maxed out and arrays perfectly positioned on a perfect day.

So far I have found this arrangement to be satisfactory. I am not consuming much power and, combined with solar, the LFP is providing days of power at anchor, it is fantastic! Consequently I can live with relatively low engine charge rates.

I spent a week at anchor last summer and did an hour of engine charging when I got down to 50% SOC -old habits die hard - this was more for a test of engine charging than a necessary recharge. I wanted to monitor temps and performance in warmer weather. This went well, alternator heated up with a 40 amp load for an entire hour but stabilized well within temp margins. I was very happy with this performance although I would not be pushing the alt much harder than that.

The cable is sized to pass 100 amps, so I think I am within acceptable margins and am sensitive to this issue with respect to adding any large loads.

I originally contemplated replacing my propane with an induction cooktop, etc. but concluded the additional complexity was not worth the hassle esp since I finally have my propane tanks sorted out. Also, I was simply uncomfortable with these high voltages away from the dock where sometimes there is water coming in every which way on a 30 foot boat.

I do not intend to add another LFP with possible exception of a 100 AH back up battery in the space where the old AGMs lived. That is for the future though an i’ll do a design review before I implement that if I ever get serious about it.

Electrical inspection is a good idea and I appreciate your comments.

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By the way, the white device on top of the battery is a “space” temp monitor. It transmits cabinet temperature to an external meter which I can see in main cabin. I turn fans on manually to manage the temps in there and in the original battery space where the start battery and victron are located. I rely on BMS for cell temp, the solar controller temp monitor is located at bottom of positive LFP battery post. Victron is self monitoring and de-rates if necessary. Shore power and regulator temp monitors are connected to the AGM. A separate regulator temp monitor is connected to the alternator and will de-rate the alt if necessary.