Building our Sailboat’s 48V Lithium Battery [2.08]

[@peterlundahl2969]

Tack för ett mycket intressant avsnitt ser fram mot nästa avsnitt

[@andersnilsson6625]

Spännande projekt, eller i alla fall ett projekt med spänning 😄 Vad är det för kul projektbåt ni var ombord på och gjorde batterijobbet?

[@SailingAnneMon]

Tack! 😊 Det är en annan motorbåt på har

[@imar758]

Kommer det att finnas något reservsystem eller ligger alla äggen i en korg? Själv kan jag inte mycket om el men jag uppfattade det alltid så att man hade separat batteri för motorn. Det låter ju verkligen som du kan det här. Jag ifrågasätter inte ditt kunnande alls. Efter att ha sett filmen om er Atlantsegling med Anne-Mon 1 så känner jag ingen oro för ert projekt. Jag är bara nyfiken på hur det skall fungera.

[@SailingAnneMon]

Vi försöker tänka på att skapa redundans på alla kritiska delar i systemet så att ett fel på en komponent inte ska kunna slå ut båten. Än har vi inte riktigt landat i om vi kommer ha ett separat startbatteri och förbrukningsbatteri på 12V-sidan eller om det blir ett batteri med en ordentlig övervakning. I normalfallet kommer batteriet/batterierna på 12V-sidan bara hantera peak-laster eftersom att de annars hela tiden kommer ligga i ett float state från en DCDC från 48V. Det blir säkert en mer ingående förklaring hur vi tänker kring detta i en senare film. 😊

[@chrisr819]

Your 280AH bank is by far too small to run 2xMulti, you need min doubled.

[@SailingAnneMon]

Thanks for dropping a comment 😊 Do you want to explain why you think it is too small? This is how we have been reasoning: The main drivers for going for 2x5kVA Multis is that we wanted the charge current to fully utilize our genset and we also didn’t want to be limited during discharge in the way that we have to think about what appliances we turn on at the same time. It shouldn’t be a problem to turn on the water kettle when the cooktop and dishwasher is already running. So, if we start with discharge we will have a total connected load of apporx. 15kVA. Obviously we will never run all those loads at the same time. At our highest loads we will probably only run half of them, and that will be for very short period of time (minutes). From a thermal point of view that is long enough to be a continuous load for the Multis and that is why 10kVA felt reasonable. It also gives some head room for thermal derating. If we look at it from a battery point of view a load of 7.5kVA will result in 184A (7500/48/0.85) or 0.66C which should be within both cell and BMS specification. We will for sure do some thermal testing of this and I think our weakest point right now is the busbars between the cells. From a charging point of view 2x5kVA Multis can deliver 2x70A. For our 280Ah battery that means 0.5C which what is defined as a standard charge rate for our cells. Our genset will be the limiting factor here and we will not really reach 140A charge current. Then you could argue that we should have a bigger capacity in relation to our load to be able to run out of batteries for a longer period of time. Our target with this system is around 3 days from full battery to completely empty without any charging. Then we will rely on as much solar that we can fit and our genset if needed. In the end LFP batteries can withstand a lot of cycles and that is what we will try to utilize with this dimensioning. Will it work? Time will tell. Worst case we just add another battery in parallel 😊

[@chrisr819]

@@SailingAnneMon lot of theories…I am dealing with lithium since 20years, first cells scraped half legally from a military vehicle to build a competition car stereo vehicle and my buddy runs an NPO in Austria producing Powerwalls and commercial EVs. I am liveaboard and circumnavigate since 2019 running a 12V 4P4S 1088AH bank with 272AH Lishen cells. My cells are bought via my buddy who made sure I got grade A+ factory matched and internal resistance calibrated 16 cells (each cell was 180Euro, his factory purchase price and he gets every 2 week 3 container from Lishen) you cannot buy that as end customer unless you get Winston which only produce and sell this quality. The 280AH cells you have degenerate much faster if constantly used above 0.3C, doesn’t matter what spec tells you, they are budget storage cells most likely b grade at best and no Winston where same capacity costs 3-4 times your cells. What manufacturer (believe it’s eve or rept from terminals), what quality do you get (test report/scan QR codes) from which supplier? One 5kw multi from load is already limit for your 280AH cells, as eg 100A inverter load x1.4 means the real load 140A on/off in millisecond (don‘t believe put on Osszi in and it will prove you that). And if you use induction hobb ( a good one with industrial grade coil burners, cheap is even worse) add a cos pi of 0.7 which means 100A/0.7x1.4=200A is the real load on/off in milliseconds, you see 100A at BMS or Victron BMV712 battery monitor. Use class T or NH fuse with min 30kA short circuit certification as main battery fuse as these 16 cells can produce up to 18000A in an internal cell/bank short as each other fuse type will be arced and therefor useless by that up to 18000A. I burned a car down with a 24V 400AH bank that got an internal cell short and even a 15kA speced class T fuse got arced. Busbars are ok. During build I see loads of mistakes, no isolation between cells (the case carries positive and heat shrink is quickly damaged). No clamping/compression of cells. Battery box should be of non easy flammable material (I know loads of videos show wooden boxes…I use PVC, PP or acrylic boards), box should be airtight (otherwise corrosion and problems over time) but in case the gas valve of cell open that gas must be able to leave the battery box, if not you build yourself a bomb :-(…. I highly advice to get a 2nd set of cells with a 2nd BMS put in 1p16S put parallel, to get load and charge under 0.3C. For each battery class T or NH fuse plus disconnect relay in positive right after main terminal, negative a 500A shunt With a Victron BMV712 battery monitor which also has a relay steering output. The BMV712 does the independent last resort cut off in case BMS fails (mosfet BMS like JK the mosfets tend to fry close in overload or a short, so no disconnect anymore) that steers the disconnect relay. The BMV712 has also midpoint monitoring, so the 2nd measuring output of it goes on cell 8. like this the BMV can also detect a cell deviation means a dangerous cell runner as it measures the voltage of cell1-8 and 9-16, if that exceeds a threshold you can set (I advice 200mV) the BMV is also cutting the bank. This last resort is requested by ISO or ABYC installation guidelines and if you don‘t have it your insurance will bail out easily of any battery related claim/damage.

[@chrisr819]

@@SailingAnneMon just several other thoughts…2x5kw multi have a huge standby wattage (the real, not Victron marketing one) of 200W, that on the whole day is already 4,8kwh. I have 2 Multi 3kw and instead parallel staged them means only one is always on and 2nd is switched on via generator assist if load is above 2450W for more then 5sec. As multi has only one AC in you need a manual transfer switch where you can select if AC in comes from 2nd multi, generator or shore power. With a gen as main source a Quattro would have been much better and the right choice as it has 2 AC in and manages them automatically also with power assist and smooth phase in gen. With your loads you will do 1,5days max, not 3 as you calculated, double capacity will give you the 3 days if you manage the standby of your 2 huge Multis accordingly. I assume starlink comes on top, 60W always on…

[@SailingAnneMon]

@@chrisr819 The cell we have bought are Eve cells. It was not really the focus of this video but the cells are insulated with epoxy sheets, they are compressed with threaded rods and we use a class T fuse with 20 kA IC. On the topic of battery box I really agree. Ideally I would like to have a fully sealed, thermally insulated and burst valve equipped aluminum box with off boat ventilation. The problem is that it quite easily run out of hands. Instead we try to focus on a mechanically safe installation with the proper monitoring. Using the mid-point monitoring on a BVM/Smart shunt is a option. On the topic of Multi standby consumption it is really good to get input from others. Not sure if you have Multiplus or Multiplus 2. We have Multiplus 2 and the standby consumption per unit is 21 W without any of the power saving setting enabled. We have also measured this consumption. I have not been able to find any information about if a parallel configuration will set the slave unit in standby if not needed or if we get 2x21 W in standby consumption. Time will tell where we end up there. A Quattro would for sure have been really nice. We got our 2 Multis for a really good price during the autumn deal that Victron had so a Quattro was not really a viable option from an economical point of view. The shore power/genset connection we will solve with an automatic transfer switch and the input AC current limit we will try to automate with some logic in the Cerbo GX. Otherwise we just adjust in manually

[@chrisr819]

Battery box at least use PP boards which you can work on with wood tool, on top a screwed down 5mm acrylic plate so you can visibly see whats going on. For the 2 battery cable use protection plastic cable guards and just drill hole in the box thats 1-2mm bigger. Like this the box is 98% air tight but gas can exit. Simple and safe. Hardly believe they have 21W, have the better MP1 and they state its 26W but reality is 45W, with starlink on its around 100W. And this is just a 3kw one, 5kw has a bigger trafo and semiconductor so at real standby it must be >80W. Yes parallel means both are permanently on and use even more standby then each individually which has the reason that they need to sync the phase constantly. Thats why i gave you the tip that you can also stage them with has 3 advantages: 1st only 1 in standby=more then half capacitysaving, 2nd only 1 wears as 99% of time one 3kw or 5kw is enough and 3rd in case of a defect eg short in the system only 1 is on= can be damaged. 2 Disadvantages 1st multi only 1 AC in so you need a transfer switch shorepower, gen or fake 2nd inverter. 2nd use of 2 as charger needs manuell intervention means you have to switch to charger only and need a remote bypass switch so you can manually switch it on. You program the multiplus relay output of multi no1 with generator assitsent that closes this relay at eg 4000W. The relay output goes on remote/aux in of multi 2. AC out1 of multi 2 connects to transfer switch and that to AX in 1 at MP2. My main charge source is solar and i hardly ever connect to shore power and also to a semi permanent installed gasoline honda gen. So a manual 3 pole transfer shore,gen,switch is simple,reliable and cheap. Spend your money on important stuff like a BMV712, which is an excellent cheap independant and reliable last resort method that as side effect integrates battery data into cerbo. Don't know anything thats as reliable as that BMV. The 280AH eve you got have the worst of all terminal with very small surface and are definitely grade b at best. Your problem is to get a big enough contact surface so busbar hole must be minimum size possible but that gives you problems with busbar cannot move in technical expansion.