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[Music]  Jeff Cote here with boatingtechtalk.com  we've got a question from a fellow boater  Manny asks Jeff  do you have any advice on how to  design a charging system for a catamaran  specifically  Manny continues to ask combining two  alternators to charge three battery  Banks while sailing and charging using  Shore power at the Merino  and Manny keeps on and goes on and  says Jeff I've got two lead acid starter  batteries and one lithium house battery  Bank okay all right there's a lot of  information here to consider right first  of all  with a catamaran a little bit similar  to power boats that have dual engines  right you're gonna have basically  debt you should have dedicated starter  batteries for each engine which Manny  does good now they're lead acid  and that's in contrast to the lithium  so there's going to be complications  here on how do you recharge using an  alternator something that is lead acid  and something that is lithium so that's  going to be an issue that we're going to  resolve and then also questions about  how do you have three battery banks with  only a single let's say inverter charger  and how do you charge three battery  Banks offshore power okay well let's  start with first things first let's  start off with Shore power Shore power  in a boat like a catamaran or actually  again this would apply to other power  boats that have got dual propulsion  system right which is not uncommon for  many power boulders the first thing you  want to do is you'll probably want to  have because inverter charger is only  most of them only have a single  connection to the battery bank and some  of them have maybe an auxiliary but it's  quite hard nowadays they used to in the  past like sand tracks for example but  nowadays you're not going to be able to  use an inverter charger to recharge  three battery Banks it doesn't quite  work like that so one suggestion is to  install onboard  and most likely a lot of you if you're  going to have a boat of that size with  dual propulsion you might have an  inverter charger so if you've got an  inverter charger I would have my  inverter charger and especially the  charger profile of my inverter charger  just charged my house battery bank which  is lithium so again dedicated inverter  charger to Dedicated lithium that makes  sense but what about my auxiliaries what  about the starter batteries well the  starter batteries going to be charged  from Shore power via a small little  dedicated charger so it could be a 20  amp 30 amp 40 amp that small little sort  of auxiliary charger and we see that on  some boats you might have even a  generator on a catamaran and so it would  recharge both the engine port engine  starboard and generator battery and  generally those batteries are not going  to be lithium they're probably going to  be lead acid now it could be flooded  could be AGM but you know so install a  secondary a dedicated small charger  that is meant to recharge your starter  batteries so again the port and  starboard engine batteries and maybe  even a generator battery so so far we've  got an inverter charger for your lithium  because the battery is lithium and you  can configure your inverter charger for  lithium and then we're going to have a  small auxiliary charger for your  charging batteries for starting all  right so far so good but now the  question might be well okay Jeff great  so we've got this sorted out when we're  connected to shore power or running a  generator but what about under  propulsion what about how do I get my  alternators which are most likely  connected to my engine batteries and how  do I have my engine battery and my  alternator on either side recharge my  lithium battery well the way to do that  especially when you have different  battery Banks chemistry in this case  Manny has lithium and also lithium and  lead acid well then okay so then maybe  what you want to consider doing is  installing what are called DC to DC  smart converting devices right so these  devices and victron creates them and we  have a whole section on our website  check the links what it does is it says  okay well I'm seeing a what I consider  being a charge voltage at this battery  so a charge voltage assuming that your  starters are 12 volts could be 24 but  let's assume it's 12 volts  if ever we Sense on the anywhere on  the engine battery a charging voltage  meaning that somehow maybe the  alternators are working and charging the  batteries above let's say 13 4 13 3 then  maybe you want to share that charge and  have it go to the lithium but the  lithium won't want the same charge  profile as your lead acid battery so you  need a device that is going to basically  be a DC to DC device but also has some  intelligence so it needs to be a device  that actually looks and says okay well  what does the lithium battery need and  should it have what the lead acid  battery does and most of the cases it's  no so there's going to be some  adaptations there's going to have to do  something from what the lead acid  battery is getting which has its own  alternator with its either external  regulator or internal regulator and then  take that and convert that to the right  voltage that the lithium battery wants  to recharge now the limitation with that  is that these DC to DC charging  converters are generally not  we're not able to install them or  procure them with high amperage so you  know some instances where let's say for  example it's a small alternator you only  have a 50 amp alternator well you might  only put a 30 amp and that's basically  now in 2023 is basically the max size is  about 30 amps and so on some boats where  we want to share more alternative power  let's say you have two 100 amp  Alternators on either side you're like  well why would I limit myself to only 30  30 when my engine batteries don't need  more power and I want to take all that  extra power and I want to redirect it to  my lithium well in some instances we've  installed two  three so we'll actually put stack them  one on top of another not literally but  like effectively have maybe even three  of those devices go from starboard to  lithium and then from Port to lithium  and so we'll have three to three DC  smart charging Converters on either side  to be able to utilize the power from the  alternator especially once the engine  battery is full to have that power go  back to that house lithium battery and  general Strokes that's basically how we  solve multiple engines  or charging sources for alternator to  go back to lithium and that's also how  we charge having different chemistries  on a boat is to have different types of  chargers for different types of  batteries  so if you've got further questions  about this topic put post your  comments below and see if the  community can help out a little bit  we're curious to see what kind of  challenges you're facing and we've also  have different write-ups on this on our  website so let's geek out and make our  boats better and more reliable thanks  for all of you for watching  we appreciate it so if you're curious  again go on our website and find out  more answers and solutions with this  sort of setup and thanks for asking and  thanks for all of you for listening and  tuning in  English (auto-generated)  Videolytics      Tools