[PSUBS-MAILIST] Lithium battery

Mon Oct 19 10:42:09 EDT 2020

 Hank, I have been doing a lot of research on this vary issue with my new boat, the R800.  I really like the Valence U27-12xp lithium Li FePO4 battery.  There is a least one commercial private sub that uses these battery modules.  Do a search on YouTube for info/ teardowns on these batteries.  What is good about them is battery chemistry is more stable than conventional LI batteries and heavy duty electronics.  Not your typical crappy Chinese electronics. They come in a group 27 form factor with a nominal 12V with a built in BMS in each module.  Each module has a 137AH capacity.
These modules new are on the order of $2,500 each but are readily available on Ebay at $450 each.  Each module has a life of 3000-4000 cycles with used modules on Ebay with 10-300 cycles so lots of life left in them.  They are set up so that an overall BMS unit manages the entire pack interfacing with each modules interval BMS.  These modules can be configured in just about any series/parallel arrangement you can think.  For my boat, I am looking at  3S2P configuration, that is, 3 of these U27-12XP's in series with 2 banks, one in each pod in parallel. This would give a bank voltage of 36V and a bank capacity of 274AH or 9.9kWh.  I am using 36V the main propulsion bank to mate with the Minn Kota 101 running at 36V nominal.  IF you want more capacity, you would put more more in parallel, i.e., 3SnP where n=1, 2...  I am also using these for the emergecy battery bank with a 0S2P configuration for 24V nominal.
Communication with module and cells within each module is via. serial communication using RS-485.  After a bank has been wired, you can connect a laptop an plug into the overall BMS and integrated each module on aspects such as number of cycles, cell voltage and temperature, current  ...
For PLC guys, because it uses standard RS-485 serial communication, the PLC can also interface with any are all of the modules.  See for a quick overview.
Valence U-Charge XP Series Lithium Ion Batteries

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Valence U-Charge XP Series Lithium Ion Batteries

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On the downside of LI, it would be good to hear from Hugh Fulton, designer of the Q-Sub in New Zealand.  The last time I spoke with Hugh he said that he was on his third set of LI batteries and was not a happy camper on the battery front.  
As a comparison, below is a table of the Valence U27-XP compared with a Mighty Max ML110-12 AGM.

| Comparison - Valence U27-12XP and MightMax ML110-12 |
|  |  |  |
| Description | U27-12XP | ML110-12 |
| Configuration | 3S2P | 3S2P |
| Type | Li FePO4 | AGM |
| Group | 27 | 30H |
| Bank Voltage | 36V | 36V |
| Capacity | 276 | 220 |
| Watt Hours | 9.9 | 7.9 |
| Max Discharge current | 150A | 900A |
| Bank Cost (6 modules) | $2,700 used | $1,212 new |
| Cycles | 4000 | 500 |
| Weight (Lbs) | 42.2 | 63.9 |
| Requires BMS | Yes | No |
| Detailed cell sensors | YEs | No |
| SOC measurement | Yes | No |
| Interface with PLC via RS485 | Yes | No |

For a shallow diving psub, the advantage of LI energy density as compared with AGM is not that important as we normally add lots of ballast but for a deep diver, you normally have much less ballast due to the added thickness of steel in the hull so the energy density  becomes a very big advantage.  For the comparison above you can see the weight of the U27-12XP is 34% less than the ML110-12 AGM.
Let me know what you finally end up with.  I am assuming this is for the E3000?
Cliff
    On Monday, October 19, 2020, 07:22:26 AM CDT, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Hi All,I am looking at going with Lithium batteries inside my sub.  Of coarse weight is the reason.  Has anyone gone down this road?What is best?Hank_______________________________________________
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