lifepo4 independent and combined battery banks

SV Lyric

New Member
***Parts of this post were originally posted as a comment in another section but I have moved it here after receiving a suggestion to start a new thread***


Hello all. I'm a new member here with a solar system on my sailboat and I am looking to upgrade away from lead acid.

I wish to switch to lifepo4 but I have concerns if a single cell should die or if a battery bms shutdown should occur at a critical time eg poor weather. I am trying to design a independent but shared load 2 bank lifepo4 system with a lead acid start battery to replace my tired all lead acid system. My hope is with two (semi) independant lifepo4 systems I will lessen the likelihood of a sudden loss of power to navigation equipment and my beer fridge. :)

A basic schematic I have started is attached. I would appreciate knowledge and feedback anyone has to offer that could simplify the system or errors I might have with wiring or device use.

My schematic at this point for simplicity does not depict switches or fuses.
I already have bms(s) and the lifepo4 cells on hand and would prefer to use them for this build.
 

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mikefitz

Solar Addict
Those Victron Argo diode splitters are not needed, too complex and something else to fail.
Connect the battery inputs together and the outputs together. Feed all chargers to the batteries and take your loads from the parallel connection of the batteries.
You dont need the isolated version of the Orion, the non isolated version will be OK for your design.

With the Overkill BMS you can control the batteries via the app if required. Should any failure occur within one of the batteries the other will take over.

The 30 A Orion takes up to 40 amps from the charging system, operating two chargers could overload the alternator at low engine speeds.

Do you have power winches or power windlass or power inverter?

Mike
 

SV Lyric

New Member
Those Victron Argo diode splitters are not needed, too complex and something else to fail.
Connect the battery inputs together and the outputs together. Feed all chargers to the batteries and take your loads from the parallel connection of the batteries.
You dont need the isolated version of the Orion, the non isolated version will be OK for your design.

With the Overkill BMS you can control the batteries via the app if required. Should any failure occur within one of the batteries the other will take over.

The 30 A Orion takes up to 40 amps from the charging system, operating two chargers could overload the alternator at low engine speeds.

Do you have power winches or power windlass or power inverter?

Mike
Thank you Mike. I have a powered dc windlass. I need to check the amperage. I don't use much inverter power beyond the needs of a laptop/tablet or a cell phone.

The alternator is a concern that I have. I have a "new" never-used Balmar ARS-5 from circa 2012 (will need Valeo mod kit) that I had planned to use to limit the alternator and monitor alternator and lead acid temperatures. Won't the ARS-5 protect the alternator during low rpm and derate as temperature increases?

If I understand correctly you suggest that I use a 4s2p configuration, to cut out most of the gadgetry, each having it's own bms but sharing charger input. If one cell fails I will only lose half my amp capacity. Is there a concern of charge issues due to internal differences in each string of cells leading to a unbalanced and undercharged system? That was at least my fear and reason for only combining the two banks output with the Victron diode combiner but not input. (I assume that the Orion or Syklla should be programmed to cut charging prior to the bms limit settings.)

I had also considered to separate house banks where only one bank could be utilized at a given time but that required battery switch flipping to charge or use the appropriate bank. The boat had something similar with lead acid when I bought it but I wasn't a fan; the batteries have a tendency to run low when switching is inconvenient.

-Matt
 

mikefitz

Solar Addict
I have a powered dc windlass. I need to check the amperage.
The starting current will be much higher than the running current, this could be a problem with the BMS/cells, although you may be OK( the Overkill BMS allows short term overload).
Won't the ARS-5 protect the alternator during low rpm and derate as temperature increases?
should do, not quite sure how the Orion would respond. You may need some way of selection one or both Orions, easy control via the H and L control pins.
leading to a unbalanced and undercharged system?
reports on this forum suggest that the packs in parallel 'share' within a few%. With the BMS app its easy to keep a watch on the batteries and if necessary take action.
where only one bank could be utilized at a given time
could lead to an imbalance, but would be easy to implement as you can turn off the BMS charge or discharge path via the app.
However for safety and maintenance a mechanical isolation switch on the output of each battery would be useful.

Mike
 
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