The last boring lifepo4 post 😉
Disclaimer ! I am not a battery expert nor have I ever played one on TV ! (DYODD : do your own due diligence) so some of the reasoning is quite simplified to keep it easier to follow without going into too much depth , if you want detailed info follow the links in part1 and part 2 and learn as much as you can
After having sent the 2,5 ‘boat bucks’ to China the long waiting game started and finally received my Fedex tracking number from GBS after a few days . Impatient as I am I checked every day to see when the cells would arrive at our forwarding agent in Miami for consolidation with other parts and forwarding to Colombia
Oct 10th 2019 , the big day ! To me it felt like Christmas , all these boxes arriving at the dock with GBS cells from China , BMS from Australia , the Sterling B2B converter from the UK , the Philippi boxes from Germany and various small parts and components from eBay USA and Amazon ! Everything consolidated in Miami and on a plane to Santa Marta Colombia
The first thing I did (of course) is unpack the batteries , measure the voltages and make sure they are undamaged . Everything worked out fine and all cells have survived the long trip from China to Colombia. And being on a dock with shore power meant I could start working on the install without having to worry too much about depowering Blue Pearl completely and the fridge , freezer and all other equipment on board could continue to run . To achieve this I first hooked up our Sterling battery charger directly to the house wiring so everything was now powered directly from our 50A battery charger and 220v mains from the shore power .
The next step was to start taking out our 5x 100Ah AGM’s , 3 of which I gave away to our good friends of SY Nausica and repurposed 2 of them as our new starter and bow thruster batteries
Now that we have some room where the AGM’s were I started to solder wires to the BMS cell balancing boards and mounting them to the cells and putting the Lifepo4 cells into their final place .
Initially I wanted to use a nickel plated copper bar as a ‘bus bar’ to connect the 3x 200Ah 12v ‘blocks’ and make a 600Ah bank interconnected by the nickel plated copper bus bar as this would have been the easiest and cheapest solution to put 3x 200Ah in parallel . Sadly I could not find any nickel plated copper flat bar so the next best solution was to have 3x 50mm2 Red (+ve) cables and 3x 50mm2 Black (-ve) cables made from tin plated marine wire . All cables we’re made equal lengths to prevent different voltages (voltage drop) over the cables that would cause imbalance between the 3 separate 200Ah blocks . And then connected all +ve cables to the BMS and the -ve cables to a -ve bus bar .
1 of the things I wanted to make were separate ‘High voltage cut-off’ (HVC) and ‘Low voltage cut-off’ (LVC) as first line of defense with the BMS as a ‘last resort’
My idea was to use our the Simarine Pico together with the BlueSea 7700 Latching relays
This has taking me quite some time to solve as it seems that none of the current BMS manufacturers can operate 2 separate latching relays , some can do 1 , Mastervolt can do 2 (but I dont have a Mastervolt system) but afaik no one can operate 2 BlueSea 7700 latching relays
After a lot of searching I came across a Philippi box that could operate the 7700 latching relay based on a simple NO/NC signal, so I ordered 2 of these boxes
And to my utter amazement it works everything works as I had it planned
The 500A shunt measures the battery voltage on the BMS and sends this info to the Pico system , when the voltage hits 14.3 volt an audible alarm is triggered and after 5 minutes the high voltage relay is activated , this activation puls triggers the philippi box which operates the ML-7700 relay
When the voltage drops below 14.3 volt the alarm goes off, a pulse is sent to the philippi box and the relay is engaged again
There is a 5 minute delay between audible alarm and the relay activation so enough time to do something (shut down chargers etc)
The other relay works in the exact same way but with a low voltage alarm (12 volt) through the same shunt but through a different simarine box with a separate NO/NC contact
This way I have separate HVC and LVC
The BMS itself also has a ‘last resort’ cut-off through an internal latching relay and operates on much more critical voltages , 11v and 14.8v , and I would like to stay away from those voltages as much as I can as operating lifepo4 cells on the outer edges can introduce cell imbalance and other problems (like shortening the life of the lifepo4 cell or destroying them completely)
Once the system worked as envisioned and was tested for a day or so I finalized the Lifepo4 installation I turned my attention to the rest of the equipment that needed to be changed and installed :
The Sterling battery to battery charger
The flexible solar panels
The Wind generator
The Sterling bb1260 battery to battery charger I use between the AGM batteries and the LFP bank for a few reasons , but the main reasons , as mentioned before , are to protect the LFP bank from over charging and to protect the Alternators from burning up . I opted to mount this piece of equipment in the engine bay as it is supposedly very load when the fans turn on. I also noticed that the Sterling goes into ‘half power’ mode when it gets warm , so I am not quite sure how this will impact the charge capacity while motoring ? Time will tell.
One of the things I decided to do ‘last minute’ as I noticed the Sterling ‘half power’ mode was to install a ‘danger switch’ , this switch basically bypasses the Sterling so it allows the Alternators to put out full power to the LFP bank . Why is this a danger switch ? , well, because it can kill both the LFP bank and burn up the alternators ! So I am only going to use this in a controlled way ie when at anchor and I need to charge the LFP bank from the alternators , I think (hope!) I can get away with this by only using it while the engine is slightly above ’ticking over’ so 800-1000 RPM. The positive side is that I can now combine the AGM and LFP bank as well in case of an ‘emergency’ like a flat AGM starter battery or problem/disconnected LFP bank . This will enable me to still have power on the boat
I strongly recommend against installing this bypass switch on any system ! if you are unsure whether or not to install one, do not do it ! Even if you are sure you want to install it for whatever reason, think about it twice , sleep on it , and then decide against it . This may very well burn up your alternators and/or destroy your LFP bank.
Now that the Sterling was installed and working I decided to connect the 100Wp flex solar panels and the wind generator directly to the charge bus of the LFP bank. I did this because I figured that as our ’normal’ power usage is around 15Ah , and the max output I have ever seen combined from wind and flex solar panels is around 15Ah as well , the risks of connecting these directly to the LFP bank are minimal . Our Victron 100/50 MPPT will do most of the charging and stops at charging 13.8v and then goes to float (13.5v) There is no current from the Victron MPPT going to the LFP bank until the voltage drops to 13.5 volt . If the Wind and flex panels continue to charge with 15Ah after the bank is ‘full’ that it is enough to cover our usage without overcharging the LFP bank. Both the wind gen and the flex panels each have their own shunt that displays on the Simarine Pico so I can always keep an eye on their charge current .
And this is the final install schematic
And how do we like our new batteries ?
Since installation I took us off shore power so 99% of Blue Pearl has run on battery & solar for 2 weeks now . And I must say it almost performs better than expected . When the sun shines the batteries are fully charged around 1 – 1:30pm and I have even started making coffee with the Nespresso machine and cooking on our induction plate the last few days and batteries are great ! (and so is the food 😉 I can really recommend ‘Lomo de res’
the final equipment list for us :
Simarine Pico package : we already had this
12x 200Ah 3.2v GBS cells
12x EV Power Australia cell boards
1x EV Power Australia BMS
1x Sterling B2B Charger 60A
1x Sterling B2B Charger display
2x BlueSea ML-7700 relay
2x busbar +ve & -ve
3x battery post fuse holder + fuses
2x Philippi TSC boxes
Lessons learned :
Neither the 123smartBMS nor the EV power Australia BMS is able to operate the BlueSea 7700 latching relay ‘straight out of the box’ due to how they operate the relays and send switching signals , a better choice would have been a 7703/7713 although these are not true ‘latching relays’.
Neither the 123smartBMS nor the EV power Australia BMS can do separate HVC and LVC , they have either one output *or* switch both outputs at the same time.
I am sure there are BMS’ out there that *can* do a separate HVC and LVC , sadly I could not find one so I used our Simarine PICO , and that works great with the philippi boxes , (with the 7713/7703 there’s no need for the philippi box as our PICO could operate those directly)
I did not go with the drop-in replacements for the following reasons : 1) costs , cells were cheaper in the end 2) the internal BMS limits the current to 100A or so 3) I like to have more control 4) drop in does not have HVC / LVC , so I would still have to use the pico but with added complexity 5) drop in typically consists of many smaller cells inside = many connection points = many points of failure