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Old 28-02-2021, 03:53   #1
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Lithium install for our 450

I have been planning and working on our lithium install for our ‘new to us’ L450 , hopefully we can get to her in the next month so I can install everything but I wanted to share what I have done so far

Please comment if you see something that could have done better or different ?
Thanks

http://www.svbluepearl.com/1100-ah-1...-a-lagoon-450/
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Old 28-02-2021, 06:46   #2
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Re: Lithium install for our 450

Pretty work. I wish my battery bank looked like that.
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Old 28-02-2021, 09:02   #3
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Re: Lithium install for our 450

It generally looks good, but by moving some connections as indicated by the blue arrows in the attached picture, you get more balanced currents through the batteries. Note that I would only take power out at one positive position and one negative position. Making these changes, you would get the classic way of wiring up such a battery pack.

Here is a simulation of your bank as I would make it: https://tinyurl.com/see98hv6

If you toggle all six switches by clicking them in that simulation, you get the setup you have with less balanced currents. You can move your mouse over the batteries to see their currents.

I set the internal resistance of the batteries to 120 uOhm which is what I found in a data sheet. The connections have a resistance of 24 uOhm which is based on a copper thickness of 2 mm, width of 25 mm and length of 70 mm. Whatever the resistances are, the balance will be improved by making the changes I suggest.

Even though the current differences between cells in the simulation are quite high, what would probably happen in real life is that the parallel cells will get a bit out of balance under high loads and then get back into balance when the load is reduced. So it may not matter all that much, but you might as well use the best possible setup.
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Old 28-02-2021, 09:36   #4
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Re: Lithium install for our 450

Another way to think about the balance is that as far as possible, you want all paths through the battery to have the same resistance. In the attached picture, I drew two different paths through the battery. The blue one has less resistance than the green one due to going through fewer connectors. This means that more current will follow the blue path and the batteries in that path will see a higher current. By making my suggested changes, all paths will have the same resistance.
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Old 28-02-2021, 11:48   #5
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Re: Lithium install for our 450

thanks Bjarne !
I will see if I can improve and if it will make a difference (heat , capacity , rsistance etc)
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Old 01-03-2021, 11:44   #6
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Re: Lithium install for our 450

following
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Old 02-03-2021, 06:18   #7
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Re: Lithium install for our 450

Quote:
Originally Posted by BjarneK View Post
Another way to think about the balance is that as far as possible, you want all paths through the battery to have the same resistance. In the attached picture, I drew two different paths through the battery. The blue one has less resistance than the green one due to going through fewer connectors. This means that more current will follow the blue path and the batteries in that path will see a higher current. By making my suggested changes, all paths will have the same resistance.
I'm very shortly embarking on building my own system, Batteries in transit, not to dissimilar to OP actually and have found this discussion really helpful, especially the link you provided.. will design my battery bank using that I think as this always seems to need a little brain power from me to get my head around :-). As simple as it is.

My bank will be 20 X 280AH in a 12V configuration of 5PX4S = 1400AH. so very close.
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Old 08-03-2021, 04:36   #8
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Re: Lithium install for our 450

These are very helpful posts, I plan building something similar. I have in mind to build 4 x 12V batteries out of the 16 cells, and monitor them individually with a Daly BMS 150A. Could that be safer because of the redundancy? If there is a fault in one cell, or one battery, then the others continue to run.

Another question:
I am unfortunately not on board my boat and cannot find the information on the amps of the electrical fuses. I have a European 230V system. I would like to connect (for example, on shore power) an induction cooking plate in the galley at the outlet with 3500 peak power. Is this possible?
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Old 08-03-2021, 04:57   #9
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Re: Lithium install for our 450

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Originally Posted by Ulstue View Post
These are very helpful posts, I plan building something similar. I have in mind to build 4 x 12V batteries out of the 16 cells, and monitor them individually with a Daly BMS 150A. Could that be safer because of the redundancy? If there is a fault in one cell, or one battery, then the others continue to run.

Another question:
I am unfortunately not on board my boat and cannot find the information on the amps of the electrical fuses. I have a European 230V system. I would like to connect (for example, on shore power) an induction cooking plate in the galley at the outlet with 3500 peak power. Is this possible?
Keep in mind I'm a beginner here also :-). Firstly running a 3500W (3.5kw) induction would draw roughly 274A, with possibly losses and voltage drops allow for 280-300A draw. this is doable as long as you have an inverter capable of that load and the correct cabling/fusing. The cables to your inverter will be large for 12V system and you need to do your calcs here and make sure the inverter is not too far away from the batteries and you have sufficient cable size. Once at 230V, i.e. after your inverter, cable run will not be a problem as Amps needed for 3.5kw at 230V are only 15A or so.

For your first question, my advice, for what its worth, for a system that needs to pull more than 100A would be to use a BMS that supports a remote Contactor rather than having that current run through the BMS. Such as RECBMS or Batrium etc.

Very high passthrough current BMS's don't have a long life reputation :-).

BTW, I've chosen to go 5P4S which means, more or less, 1 12V battery made up of 20 cells in parallel, so if a cell fails I need to fix it but it won't stop the battery working in the short term, it will cause in balance. But I could deal with this by dropping out one cell from each series until I had fixed the bad cell. I am also using a single Batrium BMS to manage the whole bank.
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Old 08-03-2021, 05:58   #10
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Re: Lithium install for our 450

I am a beginner too, and grateful for every input of thoughts.

Thanks, I'm aware of the high currents, but it can't be pointed out often enough. I may use the hotplate only with shore power. But wenn I tear out the old lead batteries I hope to have enough space to install the inverter right next to the lithium cells. Is there anything against this?

Of course I first thought about one bigger battery with a BMS and relays from Batrium or so.
I am not fundamentally averse to BMS solutions such as REC, Batrium, etc., but do not yet see the added value. To me, redundancy with four parallel batteries with their own BMS seems like a good thing. Hoping that e.g. the autopilot can not fail when I am below deck etc. One advantage that the BMS from REC, Batrium etc have are the high possible charge currents, which for me are a reason to think of 4 x 150A Daly BMS. Each is intended for a continuous charge current of 75A total then 300A. Also the load will hardly ever exceed the 75A per battery, the BMS usually only rarely to be used up to 50%. I can't judge the durability of the DalyBMS, they seem to be built into batteries on many commercial "drops in" LiFePo Batteries.

Does anyone know how many amps the sockets in the galley and the connection for the dishwasher are fused with (230V). 10A,15A,16A?
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