LiFePO4 Conversion on sv BeBe - SM#387


Dan Carlson
 

Here is a bit of summary of the LiFePO4 battery conversion that we have been through on BeBe over the last year.    I’ll start off with a bit about ourselves as context for some of our decisions. Then describe the key components and results. 

 

Lori and I have owned BeBe for 4 years now and have sailed 7 months each winter in the Caribbean. We have primarily lived on 24v/12v power with minimal use of the previous 1800w inverter.  I’ve recorded a lot of stats as we have sailed to understand how we use things and what we need.   We typically use ~120-140AH per day at anchor and ~240AH per day underway (We’ve logged about 24 overnight sails in our four years on BeBe).  BeBe has the Yanmar 100hp main engine w/ 175amp Leece Nevile alternator, 7kw Onan genset and 160LPH 230v Dessalator water maker.  BeBe came to us with 405watts of solar on an arch. We just replaced the three existing panels with 2 LG NeON 2 panels with 345watts each (total of 690watts).   We sailed the first three years with 630AH of DECA lead acid batteries and we limped into Shelter Bay Panama at the end of season three with 3 batteries with internal shorts and the rest with greatly reduced capacity.  We ran the genset every day and twice when it was cloudy.   I was suffering from severe energy insecurity!

 

My philosophy errs towards DIY so that I know my boat systems well.  And I have a background in science/technology with lots of technical problem solving, as well as a long history of home, auto and boat projects.   But this was one of the biggest,  most complex, and daunting for me.

 

We took the approach to build an LiFePO4 system based on Prismatic cells, built into a ‘battery,’  governed by a BMS (battery management system).

  1. Our new batteries are Fortune 100AH cells in a coated aluminum case, purchased from Electric Car Parts Co.  I started 2020 with 24 cells in a 3P8S configuration (3 cells of 3.2v ea in parallel and 8 of these sets of 3 in series) for nominal 24v and 300AH.  This fall I added 8 more cells and reconfigured to 4P8S with 400AH capacity.   The height of the Fortune 100 is 305mm (12in) which is a couple of MM taller than the lip of the battery box so the lid securely holds the batteries in place.  I made custom buss bars with 1”x1/8” copper bar, and I reused the buss bars from the previous configuration to double the thickness bridging across the cell groups. (way more than adequate)
  2. I chose the ORION Jr2 BMS as it appeared to have the most capability and configurability for an application like mine.  It turns out that the amount of configurability was initially very daunting.  I know that you could get away with a lot less, but I still don’t know what capability I would want to give up or that I might want to take better advantage of in the future.   They do have good instructions to get started and have provided me with the support when needed.  But that are not geared up for end  users.  I can talk more on this in a separate thread if there is interest.
  3. Charging system changes:
    1. I replaced the original Dolphin 100A charger with a Victron Multi+ 3000/70/16/230-24v inverter/charger. The existing cables for the 100A Dolphin are barely sufficient.  Due to the heat concern in the engine room and the cable size I have limited the charging output to 60A charging. I think that the heaviest use and most likely failure mode to the unit will be due to charging usage and although the unit has cooling fans and protection circuits to limit output based on heat, I prefer to err on the safe side. We have not come near taxing the limits of the inverter.
    2. I have kept the original Dolphin 30A charger as emergency/supplement.  I only use it for short periods when charging with the generator to supplement the Victron charging. I plan to replace this soon with a similar size LiFPO configured charger.
    3. BeBe has the Leece Nevile 175A large body alternator.  I added a WakeSpeed 500 alternator controller, which I highly recommend.  I also added an Sterling Alternator Protection Device.  The WS500 is derated to 75% output and additionally has a temperature sensors on the alternator body which could derate further.  It pulls a little over 100 amps when running at 1500 rpm or above.  The highest operating temperature I have measured on the alternator is 165F.  One feature that I really like is a hard switch with sets the alternator at the ‘float’ voltage of 26.72v.  This really reduces the charging output and limits any risk of over charging.   I only flip the switch to ‘Charge’ mode when I am paying attention to what is going on when motoring. 

                                                               i.      Installation note:  Both the Victron Multi+ and the WS500 need information from the battery shunt.  I ran a 4-wire run from the shunt behind the battery box to the engine room to provide voltage and current information to the WS500 and voltage info to the Multi+.  

    1. The solar (pv) panels are controlled by a Victron Smart Solar 100/50 MPPT.  I had to upgrade the MPPT for the new larger (higher voltage) panels.  There is a fuse between the solar panels and the battery buss, and there is also a new 40amp Solid State DC relay between the solar panels and the MPPT that would allow the battery BMS to cut the solar charging if needed to prevent over charging of the batteries.
  1. System Monitoring and Control
    1. I replaced the Link10 battery monitor with a Victron BMV712 (Bluetooth enabled battery monitor)  Mounted on the 24v panel in existing hole.
    2. I added a Victron Venus GX monitor mounted on the bulkhead in the cabinet above the sink (to starboard of autopilot computer).  The Venus GX does not have a screen (Lori said no more displays in her galley!).  But everything is accessible via wifi from any of our laptops, iPads, mobile phones.  In addition it can be connected thru wifi to the external Victron VRM Portal to monitor your boat remotely.   I set this up over the summer with a wifi hotspot, but unfortunately halfway through the summer something consumed all of the data on the hotspot and my visibility went dark.    The Venus GX has wired communications from the MPPT, BMV and the Multi+.  I use it to remotely turn the Multi+ Inverter/Charger on and off.     I generally check the BMV or SmartSolar MPPT directly with the Bluetooth connection vs going through the Venus GX.   There is also the capability to establish a CanBUS network that includes the battery BMS and the WS500 alternator controller but I have not really explored the why and how to approach this yet.
  2. Other Bits of Kit:
    1. Contactors/Relays – Contrary to it’s name the BMS (battery management system) does not control your battery charging.  You primarily control that through the battery charging profiles that you set up in your battery chargers, solar MPPT and alternator regulator.  The BMS protects your battery system from over-charging or discharging, that can send signals to charging devices or activate relays to disconnect the charge or discharge sources when limits are reached.  This requires a large contactor/relay on the main battery.  I used a TYCO Kilovac EV200 500+amp 12-900v contactor.  This is a big chunk and consumes about 2AH per day.  Normally you would have one on the charge circuit and one on the discharge circuit but the Victron Multi+ confounds this (one set of wires for both charge and discharge), so I just use two small solid state relays SSR-25DD to relay the signal from the BMS to the main contactor.   I also installed an HB Controls HBC-D1D40A solid state DC relay on the positive cable from the solar panels to the MPPT to handle the Charge control from the BMS. The HB relay has a substantial heat sink to dissipate any heat generated by the load when there is a steady 70+v @ 10amp current flowing under full sun.
    2. Fuses – I added a very large fuse on the main battery for protection.   From BlueSea I selected the POWR-GARD JLLN 400A-P.   This is a 400A Class T fuse.  I would not use less than a CLASS T fuse on the battery.  And make sure your supplier provides you with the ‘time-current’ performance curves on the fuse.  The Amel SM bow thruster draws 400amps!  This fuse can handle that, and the fuse holder is also appropriately sized.   I also have a 200amp ANL fuse on the Multi+ battery cable.
  3. How I operate now:  I monitor both the battery voltage and cumulative current flow in/out of the battery bank on the Victron BMV712.  Every morning I record the battery bank voltage before sunrise and the cumulative Ahs drawn.  This gives me some benchmarks for future reference to cross check state of charge.  I have typically charged the battery bank when it gets down between 25.5v and 26.0v (this is somewhere around 15%-30% SOC.  During a period at anchor  I try to balance the battery SOC, my water tank level and planned activities to decide which days to run the generator.   I will typically run the generator for slightly over 90 minutes to allow me to produce approximately 270 liters of water and put 90+ amp-hours of charge back into the battery (usually twice a week at anchor).  At least once a month I try to top charge the battery up to about 27.4v – 27.5v (which is about 90% to 95% SOC). This helps to keep all of the cells in balance with eachother.  I keep the WS500 alternator controller switch set to the “float” when starting the motor and then based on battery SOC I will decide if I want to use the alternator to “Charge” the battery.  One trick here is that if I am motoring early in the day and ‘charge’ up the battery to high, the battery voltage will put the Solar MPPT into “float” mode and then I can lose much of the solar benefit for the rest of the day unless I rest the solar MPPT.   One other downside of not running the engine or generator to charge the batteries on a frequent basis we now need to plan for heating the water in the water heater.

 

Results:  I used to live with energy anxiety with my lead acid batteries.  Now I have a lot more capacity and confidence.  When I had 630AH of LA batteries the most that I ever used was 140AH. Last year with 300AH of LiFPO I regularly used more than 200AH before charging. Now I can comfortably use 300AH.  I used to run the generator every day.  Last season during two months of covid lock-down on anchor I ran the generator every 3rd or 4th day for water making and to top up the batteries.   This year with the increase in solar from 405watts to 690watts , only the need to make water will dictate when we need to run the generator.   And with the increased solar and battery capacity I can begin to look into induction cooking, and how to best rewire the inverter into the 230v circuit to enable use to easily run the hot water heater, washing machine, dishwasher, and even an AC in a pinch.   We don’t have unlimited energy but we are now very happy with our new limits/horizons. 

 

As I said this project was very challenging.  There are many decisions that you need to make along the way and every decision you make has many implications.  I’m far from an expert and definitely did not evaluate all of the possibilities fully.  I feel that I did navigate my way through to a solution that is best for our specific boat and style of living.  It did take me some time to get comfortable with all of the new systems.   Be aware of your comfort zone as you decide how to move forward.  

 

Happy to answer questions or provide additional information that can be of value.  But the best source of general information is the FaceBook group “Lithium batteries on a boat”.

 

Regards, Daniel and Lori Carlson on sv BeBe, SM #387

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