Since we have bought our Lagoon 42 ‘Blue Pearl Too’ I have been planning our new ‘liveaboard lithium installation’ , currently she has 6x 145Ah AGM batteries which would be more than enough for a few weeks vacation here and there and with the current 200Wp solar panels and the 5kW Fisher Panda i500 Neo generator there is ample power for ‘normal’ use.
But given the experience we built with our previous boat and the switch to lithium I am confident that a step ‘back’ to AGM batteries will be a disappointment , so we are going to install Lithium on our new boat as well
What I first did is to make a power inventory , basically going over all systems on board and figuring out how much power we need to operate all the equipment on ‘Blue Pearl Too’ without using the generator except in cases where we will have clouded skies for more than a week. This power inventory guestimate together with experiences on our previous boat and lithium bank, and some input from cruisers with similar boats we met along the way, I guestimated that we would need between 900 and 1200 Ah of capacity @ 12v.
Then I started to investigate which Manufacturer has the most integrated and affordable systems available , and that boiled down to basically one contender , Victron . But as I am not going to use any Victron lifepo4 Lithium batteries (due to costs) I needed to find a BMS (battery management system) that would communicate with the Victron systems ‘as if there were Victron batteries in the system’ . The BMS that closest matched my requirements is the REC-ABMS .
Once decided on which cells I am going to use , 16* Lishen 272Ah cells which make up a total of 1100Ah @ 12v, and the BMS system it was time to tackle the rest of the equipment.
Victron has some very detailed systems schematics available and once I found the one that is closest to my needs I just adapted it slightly to our specific needs (Catamaran , 2 engines, large generator , solar panels etc)
The equipment I decided on is as follows :
16* 272 Lishen 272Ah cells (ordered directly from China)
1* REC-ABMS battery management system (+display)
2* Victron multiplus 12/3000/120-50
1* Cyrix-Li-charge 12/24V-120A intelligent charge relay
1* Victron Cerbo + display
1* Victron Multi Control for Multi-Plus and Quattro
3* Victron Energy MPPT 100/50 solar Charge Controller
1* Victron smartshunt 1000A
5* Victron Energy VE.Direct Cable (one each for MPPT and shunt)
3* Lynx power in
12* Mega Fuses
2* busbar 250A for negative side
1* Victron BP220 smart BatteryProtect 12/24V – 220A
1* Victron VE Bus BMS – Battery Management Systems for 12 volt Lithium (not sure if I need this yet)
Currently ‘Blue Pearl Too’ already has some Victron (and other) equipment and I am fully planning on using the current equipment as well
2* Cristect battery isolators (used to distribute charge from both alternators on both engines to start and housebank)
2* Standard Cristec Battery chargers (2* 40A for the housebank and starter batteries )
1* Victron 100/30 MPPT for the current 200 Wp solar installation)
230V Multiplus Charger / Inverter placement:
Since we know (expect again) we will spend minimal time in Marina’s and/or on shorepower I plan to use the 2* 3kWh Multiplus inverters in parallel just after the large generator. After a lot of thought this specific placing made the most sense . The Multiplusses are invisible to the generator as they pass through all the power generated by the generator *while* charging the lithium bank with 2* 120A when the generator is running thus minimizing the generator run time. If we happen to be in a Marina on shorepower the standard battery chargers are enough to charge the batteries , this will go a bit slower but as we are on shorepower , so who cares ? And this also negates the need for a 3rd input switch for 230v . If we have shorepower we switch the 230v input to ‘shorepower’ and if we use the inverters *or* use the generator we just switch to ‘generator’ with the 2* Multiplusses.
Also I can turn off the ‘standard’ battery chargers (the 2 with the red arrow in the drawing above) on the boats switch panel so these chargers do not take any power from the inverters to charge the batteries while the Multiplusses are using power from the batteries to make 230v !
This set up gives us 4800 watt of inverted power from the lithium bank and should be enough to cook on induction , run the 230v watermaker , run the washing machine , use the microwave and one or two airconditioning units however not at the same time ! so we still have to be somewhat cautious what we use and when.
Solar Charging :
We will charge the lithium bank with 4* 400Wp Sunpower solar panels and we are planning to keep the current 4* 50Wp (200Wp total) flexible Sunbeam panels which are currently on the hardtop and bimini . If this all works we will have a total of around 1800Wp of solar charging the lithium batteries through 2* Victron 100/50 MPPT and 1* 100/30 MPPT solar controllers. On a good day I expect to see 150-160A from the solar panels to charge the lithium bank.
I know there is much ado about alternator charging a large lithium bank and protecting the alternators from going up in smoke due to large charge currents and prevent them from blowing up when the BMS cuts off charging. I have learned from several sources, that use the same engines with the same alternators, that the 120A alternators that Yanmar uses have built in temeprature protection, meaning that when the alternator gets too hot the charge current is throttled back to lower the alternator temperature to a more acceptable level and the current then settles to around 40-60A per alternator. I believe that this is enough protection for the alternator to ensure it doesnt overheat while charging .
The 2nd concern is an eventual voltage spike caused by suddenly disconnecting the alternator from the batteries by the BMS, this sudden disconnect causes a voltage spike as the charge current has no where to go and this spike can cause the diodes of the internal alternator regulator to blow up. As I plan to continue to use the current AGM starter batteries and the alternator charge current first goes through the start battery , the AGM starter battery will function as a buffer for these voltage spikes . And to prevent the alternator from overcharging the lithium I will use the start/house combine battery switches that are standard present on the Lagoon 42. the operator (me !) will choose whether or not to use the alternators to charge the lithium bank.
I expect that with 1800Wp solar *and* an 5 kW generator the need for charging with alternators will be minimal , who would want to use the boat engines to charge batteries anyway ? they are very inefficient for charging batteries and the diesel genset was made for this purpose ! (and with the 240A charging current from the Multi’s the generator is much more efficient)
Protecting the Lithium bank:
As the REC-ABMS communicates with the Victron equipment , protecting the litium bank from overcharging and from drawing too much power is quite easy. The REC-ABMS sees the cell voltages, State of Charge etc and if/when these values are at a critical level (11.8v low and 14.6v high) the REC-ABMS tells the solar MPPT’s to stop charging , if this does not help and the voltage continues to rise it sends a signal to the Victron Li-Charge relay to cut off the whole charge circuit from the battery , this basically stops any and all power from the MPPT’s and Alternators. If the Multiplusses are charging it also sends a signal to them to stop charging . And the same for low voltage protection , if the voltage drops to low the REC-ABMS sends a signal to the inverters to shut down and no longer use power and if the voltage continues to drop it operates a Victron 220A Battery protect (220A solid state relay) and opens that so no power can be used anymore by the ships systems . The REC-ABMS together with the Victron Cerbo has various other possibilities as well , one of which is to automatically start the generator to provide charge to the batteries , and the REC-ABMS of course also does the cell balancing if/when needed to ensure a healthy lithium bank.
Physical build & installation :
I am building our lithium battery bank out of 16pcs 280Ah cells and since these are new cells from the manufacturer in China they all first need to be brought up to the same level of charge . To accomplish this I first put the cells together in the final set up which is 4 cells parallel and then all 4 parallel sets in series and now you have a 12v nominal bank, as the cells are not balanced yet and will not self-balance either , I slowly charged them with a single 12v 120A charger keeping a close eye on the individual cell voltages. As soon as the first cell reached 3.6v I broke down the cells and put them all in parallel , 16 pcs all connected plusses to plusses and minusses to minusses. Then connect the special lithium 3.65v 20A charger to bring them all slowly up to 3.65v . Both steps took quite a long time to complete !
When this charger stopped at 3.65v and zero amps going in all cells are at the same voltage and same level of charge. To verify this I took away all busbars and connects and measured the individial voltages. When they maintain >3.55v after 10-20 minutes of waiting they are fully charged and since I charged them all up to 3.65v at the same time the cells are now ‘top balanced’ and ready to be put back into the final configuration
Since lithium batteries do not like to be kept at a 100% State of Charge (SoC) I connected the REC-ABMS , the Cerbo with smartshunt and the Multiplus to the battery bank so I could draw power from the batteries, through the inverter, down to 50% SoC. This is the state of charge percentage lithium is quite happy being stored at.
making the battery box:
When all the cells were balanced and tested I proceeded to built a battery box , for this I ordered pre-cut HDPE material after measuring . After receiving the material I screwed the box together with allen screws which are sunk into the material.
As the connectors of the cells do not seem to be the most sturdy I have ever seen I decided to bring the 2* plus and 2* minus connections to the outside of the box with busbars (layered copper for easy bending and pre insulated)
and I also used black & red heatshrink with glue to give the busbars a little more protection , I am very pleased with the final results and this box should fit the current battery space (under the portside rear bed) quite nicely , the only think I need to do know if have a piece of clear plexi made that will fit the top of the box for extra protection
there is 1 point that needs some extra attention , depending on the amount of current you are going to draw from the battery set the point where the 4 plusses meet the 4 minusses (in the middle of the left 8 cells in the battery box) this connection may get warm as the full current runs through there . If you want to play safe just add another busbar there to double up on the thickness . This is what I did , if you look closely you can see an extra busbar on top
connecting the battery bank and fusing :
As this lithium bank is going to provide quite a bit of current to the 2* 3000W multiplus (up to almost 400A total) I want to make sure everything is connected and protected as best as possible . For this I am using the Victron Lynx ‘Power In’ .
Normally these are 1000A busbars without any fusing but this is easily solved , first you need to get 4* M8 (or 5/16) bolts washers nuts . then open up the unit removing the middle black plastic cover , when you remove the cover you see 4 open positions that will take the 4 bolts .
when the bolts are in place but the black plastic cover back in place and put 4 mega fuses between the top bolts and the middle bolts
and now you are ready to put the + cables from the lithium batteries to the middle bolts , and they are fused as well ! . If you are wondering about cost ? these Victron busbars are actually quite cheap compared to having to buy busbars , fuses, fuse holders etc , and the quality and looks are great .
I am going to use 3 of these ‘fused’ Victron Lynx power ins , 1 that connects 4* 50mm2 cable from the battery back, the 2nd will connect to the 2* Multiplus with 4* 50mm2 each and the 3rd will receive all other ‘charging’ connections (Solar , Alternators etc) the boat systems , the normal + and – wires to power the boat will be connected to the connections on the Lynx , these are covered with red and black plugs, on the left side in the pic above. And between the 1st and 2nd busbars I will have the smartshunt so we can keep track of the battery SoC (state of charge) etc.
20-Feb-2021: I am still writing this so please check back as I should finish this whole article in the next weeks or so
Connecting the Multiplusses , Solar and shunt:
Where to install everything :
Some questions I received :
Q: i see you do not use any alternator regulators or protection , I thought that was needed ?
A: Overcharge is unlikely, stock alternators are usually limited at 14.2V, to charge 4 balanced cells to 3.65V (full) you need 14.6V, so alternators cannot charge a lithium battery full in a reasonable time, they just can get it to about 92..95% SOC. If it gets dangerous to the LFP battery, the BMS will disconnect the chargers any way.
Q: I was under the impression that REC ABMS can only measure and balance 4 individual cells and I see you have sixteen. Have I misread their capabilities?
A: every parallel set of cells (4 in my case) is seen as a single cell by the REC BMS , and as these parallel cells are balanced among themselves while charging , as I top balanced them and while they are in parallel they cannot drift, I see no risks, if one parallel set drifts in voltage compared to the other parallel sets the REC will balance them
Q: Are you not going to compress the cells more for increased longevity ?
A: There is a lot of debate about compressing these cells with 2900N , some people say that this compression is supplied by the case of the battery as this is stated in the specs of the cells , others state that you need to add extra 2900N compression. What I do know is that the specs say that with compression you get 3500 cycles , without compression 2500 cycles , using a 1C charge and discharge rate from 100% full to 0% . We will never be able to charge and discharge with 1C rates , that is 1100A for us ! And if you calculate 2500 cycles , with one cycle per day from 100% to 0% that is 7 years. As with our previous Lithium bank we may get 1 cycle per week , so 52 cycles per year which translates to 48 years *if* we charge and discharge with 1100A ! As we are charging and discharging with much lower current *and* we mostly cycle between 80% and 20% SoC these cells will last even longer . So (extra) compression ? I will leave it like this for now
Q: Can u guesstimate cost of the setup and how many years of usage u think is breakeven point? Thx
A: As liveaboards we go through a set of AGMs every 14-16months (drawing them daily down to 50-60% SoC) @ $480-500 usd per 100Ah AGM battery (in the areas where we have been) The lithium cells were cheaper Ah per Ah than AGM’s , so break even point is 14-16 months if I count a new bank in that time.
Q: Cats don’t like weight
A: Yes ! that is why I am taking 7* 50kgs (350 Kgs / 700 Lbs) out and putting 80kgs (160 Lbs) back
If you would like some assistance with planning and installing your own Lifepo4 bank, or would be interested in having one installed in your own boat , please feel free to contact me