48v marine battery pack 300ah

Just joined this forum and see lots of good info and links to battery cells.
I just purchased a motor from electric yacht and in a process deciding on battery bank. I don't have 12k laying around for 300ah for battleborn setup so I'm leaning towards building my own 48v battery.
I found some good suppliers through this forum but I do have one question.
I can do this by buying 16 cells that are 300ah and just do them inseries and be done. But what happens if one cell dies, I would be screwed since I use them for propulsion.
My other idea is to get 100ah cells and do parallel and then series connection to get the same 300 ah battery. This way if one cell dies I can always cannibalize one of the parallel connections and replace the failed one and end up with 200ah battery and some extra cells. This way I can at least fix an issue and still have propulsion just at lower ah capacity. If I go with first option, then there is no fixing it on a fly.
So any recommendations on which setup to choose as far as being able to fix it while in the middle of nowhere?
Thank you

Kommy000 said:

.......
I just purchased a motor from electric yacht and in a process deciding on battery bank. ......
I can do this by buying 16 cells that are 300ah and just do them inseries and be done. But what happens if one cell dies, I would be screwed since I use them for propulsion.
My other idea is to get 100ah cells and do parallel and then series connection to get the same 300 ah battery. This way if one cell dies I can always cannibalize one of the parallel connections and replace the failed one and end up with 200ah battery and some extra cells. This way I can at least fix an issue and still have propulsion just at lower ah capacity. If I go with first option, then there is no fixing it on a fly.
So any recommendations on which setup to choose as far as being able to fix it while in the middle of nowhere?

Click to expand...

I think there is more probability of an electronic component failing than one cell falling off the cliff. If a cell is going to die it is going to deteriorate over time. That is why a good BMS is important as a management information system. In reality a large prismatic cell is a group of pouch cells in parallel. So you logic is similar to mine. In my case for my pack if 2P17S I have ordered two extra cells that I can use to replace a cell that may deteriorate. My application is stationary and I have a grid connection so I will not be stranded. I am going to mount a redundant 12 volt power supply because that is the one thing that failed in a previous system. As a result damage to the pack resulted while I was out of town. Admittedly I did not have contrls set up in a fail safe manner.

Good luck, it sounds like you have a good risk management strategy.

Kommy000 said:

Just joined this forum and see lots of good info and links to battery cells.
I just purchased a motor from electric yacht and in a process deciding on battery bank. I don't have 12k laying around for 300ah for battleborn setup so I'm leaning towards building my own 48v battery.
I found some good suppliers through this forum but I do have one question.
I can do this by buying 16 cells that are 300ah and just do them inseries and be done. But what happens if one cell dies, I would be screwed since I use them for propulsion.
My other idea is to get 100ah cells and do parallel and then series connection to get the same 300 ah battery. This way if one cell dies I can always cannibalize one of the parallel connections and replace the failed one and end up with 200ah battery and some extra cells. This way I can at least fix an issue and still have propulsion just at lower ah capacity. If I go with first option, then there is no fixing it on a fly.
So any recommendations on which setup to choose as far as being able to fix it while in the middle of nowhere?
Thank you

Click to expand...

To add to what Ampster said, your second idea for 100Ah cells does add redundancy, but keep in mind a 16S BMS will treat the three 100Ah parallel pack as a single 300ah 3.2v cell, and in all reality it doesn't make much of a difference because that's what's going on inside a big cell anyways. If space/complexity isn't an issue then three 100Ah pack is easier to break up, mod or service.

You didn't mention BMS but I'm sure that's the next part of your build. Tell us a little about the electric yacht? How long is it and how much does it weigh? What sort of electric motor does it have and how many amps at 48v does it draw at 100%?

Here's the other factor; not all LifePO4 cells are created equally, as in, some are designed for simple storage with a max of 1C draw current, continuous (it's the Ah rating of that cell x number, so 1C of a 100Ah cell is 100 amps continuous draw; 1C of 280Ah cell is 280a). Others are designed to deliver more and can handle 2C or 3C and higher bursts for a few seconds. Ask your sellers.

Weight distribution and stowage space may be a factor in designing a system for a yacht.

Fish Freak said:

To add to what Ampster said, your second idea for 100Ah cells does add redundancy, but keep in mind a 16S BMS will treat the three 100Ah parallel pack as a single 300ah 3.2v cell, and in all reality it doesn't make much of a difference because that's what's going on inside a big cell anyways. If space/complexity isn't an issue then three 100Ah pack is easier to break up, mod or service.

You didn't mention BMS but I'm sure that's the next part of your build. Tell us a little about the electric yacht? How long is it and how much does it weigh? What sort of electric motor does it have and how many amps at 48v does it draw at 100%?

Here's the other factor; not all LifePO4 cells are created equally, as in, some are designed for simple storage with a max of 1C draw current, continuous (it's the Ah rating of that cell x number, so 1C of a 100Ah cell is 100 amps continuous draw; 1C of 280Ah cell is 280a). Others are designed to deliver more and can handle 2C or 3C and higher bursts for a few seconds. Ask your sellers.

Click to expand...

Yes definitely will use BMS, not sure which one yet. As far as motor is 10kw at 48v so max draw is 200a, that is why I would like to build 300ah bank. Its a 32' freedom sailboat with 10k displacement. I should have enough space on center line where the fuel tank is to do 100ahx3 then in series to make 48v bank. I like idea of bigger cells but again, I need to be able to fix it and swap cells . I guess I can always buy extra bigger cell but then I have to have separate charging for this cell. My third idea was to keep my separate house bank and buy 4 more of same big cells and just build a 12v house bank to replace my acid battery and just charge it from the 48v bank. This way if something goes wrong with 48v, I can take apart my house bank with 4 cells and put them into 48 v bank so I have propulsion. Then I can just buy acid battery temporary to use as house bank for my lights and such. I was going to keep 2 separate circuits anyway since I didn't want to change all the existing 12 v wiring and was going to keep acid battery for that. I will as going to add 48v to 12 v device to propulsion so I can put fridge on it and maybe electric cooktop and also to charge the original 12v bank.
So in the end I will end up with 300ah house bank too and use it as back up cell parts. Though that will result in buying 4 more cells which still less money than buying 12 battleborn batteries

I feel you on the battleborns, they are not cheap. I'm installing some Roypow batteries that are 51 volts and 160 ahs for $2600 each. I'm trying to figure out if they can be paralleled as is, but if not I'm researching diodes / isolators because if one of the BMS decides to shut off the pack and the other continues charging there could be a massive amp draw from one to the other if paralleled without a diode.

Anyways, just thought I'd throw it out there for you. I'll be installing mine over the next three months on my Cal 2-46.

I also plan on getting a 48 volt brushless DC motor parallel to my existing diesel motor. I'm looking for a DC motor now, trying to figure out how many KWs I need. Anyways, I'll be posting about my install on this forum on a different thread once I get it all figured out.

I just decided on CALB 180ah cells for their strength and durability (the plastic case type)
Most of the aluminum cells have small / shallow bolts and I feared them comming loose do to vibration and constant shifting.
Let me know if you need some info on these cells.

danphillips said:

I just decided on CALB 180ah cells for their strength and durability (the plastic case type)
Most of the aluminum cells have small / shallow bolts and I feared them comming loose do to vibration and constant shifting.
Let me know if you need some info on these cells.

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That is a real concern Dan, we've seen a few of those aluminum 6mm thread terminals strip out. Also look at the Fortune/Frey cells because they have many excellent ways to connect the cells and their terminals are strong. In applications with a lot of motion or even impact like boating this is key.

danphillips said:

I just decided on CALB 180ah cells for their strength and durability (the plastic case type)
Most of the aluminum cells have small / shallow bolts and I feared them comming loose do to vibration and constant shifting.

Click to expand...

That would be my first choice in that kind of application. Have you looked at braided straps? I used them in an EV conversion where there was lots of vibration. @upnorthandpersonal mentioned in another threat that he was making some. I think i got some from Australia years ago.

Fish Freak, Thanks for your input. I looked at the Fortune cells but they only came in 100ah. that would be a lot of connections for my system.

Ampster, I will be locating the cells in a custom battery box that will prevent any movement. I havent seen any braided straps yet but I will be keeping my eyes open.

danphillips said:

Ampster, I will be locating the cells in a custom battery box that will prevent any movement. I havent seen any braided straps yet but I will be keeping my eyes open.

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I used them where the battery connections from the pack to the rest of the system had different fixing points and might vibrate differently than the mass of the pack. Multistrand cable has the same flexibility and can be found in larger current carrying capacity easier.

danphillips said:

I just decided on CALB 180ah cells for their strength and durability (the plastic case type)
Most of the aluminum cells have small / shallow bolts and I feared them comming loose do to vibration and constant shifting.
Let me know if you need some info on these cells.

Click to expand...

Can you share a link for those cells? How about BMS?

@Kommy000 ,
Here is a link - http://www.calbusainc.com/calb-ca-series

If you have any questions let me know. I looked at all the established cells and some of the inexpensive cells, and for our boat I decided on these for strength and durability.

I am intrigued about this because the time that you can motor anywhere seems very limited. You stated a 200amp draw, and you are building a 300Amp hour battery bank. So in low speed operation, using 100 amps, you would get only 3 hours of motoring before the battery is totally drained. How much range would that give you?

Also what are you planning on charging them with?

John.

This is the breakdown of speed and amps usage for my particular boat.
Speed and Power:



Speed & Power QuietTorque 10.0 48v air cooled PMAC Motor System

Kts Amps Watts (In Quiet Seas)

2.6 10 480

3.3 20 960

4.1 40 1920

4.7 60 2880

5.2 80 3840

5.6 100 4800

6.0 120 5760

6.3 140 6720

6.6 160 7680

6.8 170 8160

7.1 190 9120

Hull speed 6.81

I couldn't copy the graphic but basically range with 300ah lithium pack will be in sweet spot around 4knts at 24nm with some spare energy left and if I go down to around 2.5 then I can go around 66 nm pretty much all day. That is not counting any kind of charging.
I asked around other people with similar boats and seems and they are pretty happy with this setup.
As if now I'm wiring 400w of solar panels consisting of 4 panels x 100w and midnite solar kid mppt. From looking around I can already get higher wattage solar panels with better tech in the same space . I will probably see how it works once I do the engine swap. And if needs be, I will upgrade my solar capacity. I will also keep portable generator for emergency charging.
I just have to figure out which supplier/where/which cells to get. What BMS to get, like 300amp vs 200amp and which one that actually works and rated at those currents. I know max draw with this motor around 200amp soon guessing I probably need 300 amp BMS.
Also need to figure out the wiring. I see people using all kind of relays and I'm trying to figure out if I need them or/and fuses and where. I don't want to overkill but I don't want to fry anything by missing a simple component that should've been there. I can't even find battery switches that are rated for 200 or 300 ah currents.

Working on a affordable lithium option also

I've installed a QT20 on mine, as my vessel is about 38 ft steel hull and displaces about 12to (real life probably more towards the 14to mark with all the crap i carry on )
The whole system draws 380Ah at full throttle, but in three years of playing with the yacht I've used that only a couple of times and for very short bursts of no mere than maybe 10-20 seconds. Mostly my current draw is about 150A when going through the marina, then either sailing or motor-sailing with around 15-20A draw... It works great. The maneuverability at lows speeds / rpms is amazing!
For batteries, i've tested and commissioned the system on a 200Ah AGM 48Vdc bank and now I've ordered 17 EVE cells, to put 16 of them in series and have a spare one to play / replacement.
I'm planning to use a Chargery BMS16S 600A. All is designed up to the 400A rating of the electric propulsion system.
The cells will be installed 16s in a transparent acrylic box, held together with 6 threaded rods to make sure everything is tight.
That's the plan...so far ?

I have an old Electric Yacht Motor on my boat, which is the predecessor of the QT10. The previous owner installed it along with a 48v 270ah AGM battery bank made up of 6v batteries. I plan to eventually upgrade to Lithium, but not before I have to. However, one thing I noticed was that the 300ah cells I could find had a lower C rating than the 100ah cells. If this holds true, one could draw more amps out of the 3x100 bank than the 300 bank.

Kommy000 said:

This is the breakdown of speed and amps usage for my particular boat.
Speed and Power:



Speed & Power QuietTorque 10.0 48v air cooled PMAC Motor System

Kts Amps Watts (In Quiet Seas)

2.6 10 480

3.3 20 960

4.1 40 1920

4.7 60 2880

5.2 80 3840

5.6 100 4800

6.0 120 5760

6.3 140 6720

6.6 160 7680

6.8 170 8160

7.1 190 9120

Hull speed 6.81

I couldn't copy the graphic but basically range with 300ah lithium pack will be in sweet spot around 4knts at 24nm with some spare energy left and if I go down to around 2.5 then I can go around 66 nm pretty much all day. That is not counting any kind of charging.
I asked around other people with similar boats and seems and they are pretty happy with this setup.
As if now I'm wiring 400w of solar panels consisting of 4 panels x 100w and midnite solar kid mppt. From looking around I can already get higher wattage solar panels with better tech in the same space . I will probably see how it works once I do the engine swap. And if needs be, I will upgrade my solar capacity. I will also keep portable generator for emergency charging.
I just have to figure out which supplier/where/which cells to get. What BMS to get, like 300amp vs 200amp and which one that actually works and rated at those currents. I know max draw with this motor around 200amp soon guessing I probably need 300 amp BMS.
Also need to figure out the wiring. I see people using all kind of relays and I'm trying to figure out if I need them or/and fuses and where. I don't want to overkill but I don't want to fry anything by missing a simple component that should've been there. I can't even find battery switches that are rated for 200 or 300 ah currents.

Click to expand...

Does your system have regenerative capability? I am also thinking about installing an electric motor on my 35 foot sailboat. I plan to use solar + regenerative sailing to charge the batteries. The 48V system will also have an inverter to run my 120V AC appliances and my 12V DC appliances.

KFoecke said:

I am also thinking about installing an electric motor on my 35 foot sailboat. I plan to use solar + regenerative sailing to charge the batteries.

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Have you compared the efficiency of that versus a wind generator on the transom that would also produce energy while at anchor? My last sailboat had a folding prop so regenerative would not have worked anyway.