Hybrid battery system

[johnmwalsh]

Hello and Happy New Year! I am going to use a hybrid battery system for my house and need a way to disconnect the lfp battery for hvd and lvd. Can you recommend a system/ relay that doesn’t draw a lot of current when on. Would you use a n/o or n/c relay to disconnect? I will be using a electrodacus sbms to control the relay. I know I will need to use a low current ssr to control the larger relay. Just looking for ideas before I attempt to draw it all out. I will start with a 100ah Fla with 200ah lfp. I believe my alternator is 70 amps, internally regulated. I will add another 200ah lfp when I know the system will be ok. Also I need to know if you guys recommend a charge bus and a load bus. I will have 540 watts of solar run through 2 dssr 20s. Thank you all for your help.

[kenbo]

I would use a bistable latching contactor. If that's not easily accomplished with your BMS I'd use an NC contactor. A charging and load bus are always good design features.

[CaptainRivet]

Originally Posted by johnmwalsh

Hello and Happy New Year! I am going to use a hybrid battery system for my house and need a way to disconnect the lfp battery for hvd and lvd. Can you recommend a system/ relay that doesn’t draw a lot of current when on. Would you use a n/o or n/c relay to disconnect? I will be using a electrodacus sbms to control the relay. I know I will need to use a low current ssr to control the larger relay. Just looking for ideas before I attempt to draw it all out. I will start with a 100ah Fla with 200ah lfp. I believe my alternator is 70 amps, internally regulated. I will add another 200ah lfp when I know the system will be ok. Also I need to know if you guys recommend a charge bus and a load bus. I will have 540 watts of solar run through 2 dssr 20s. Thank you all for your help.

suggest to load down the electrodacus beginner guide.
having a hybrid system means a) you use your LFP for starter and house or b) you use your LFA and LFP banks in parallel for the house. I think you mean you have a 100AH starter and a 200AH LFP as house, correct? If yes thats not a hybrid system.



Yes it is recommended to have load and charge bus as Electrodacus has a load and charge (they call it PV) shunt = seperation by default. Also cleans up the installation.

The electrodacus switches of all loads and charge sources directly at the source via their remote function, so you actually don't need the huge cut off relay. that is its huge advantage.
I used the 4 channel 718 optocopler boards for all remote switch off connection (also when they are officially not needed), they shine red when source on and that is really handy for troubleshooting. cheaper and better then SSR.
for the alternator you need a 30A DC2DC, together with your legacy house load thats all your alternator can handle.Suggest a Renogy DC2DC or if money a Victron Orion smart.
for the legacy house loads (means the main plus cable which most likely will carry 20-40A current max) I recommend a Victron battery protect 220A. Use the biggest, so you have overhead for capatitve loads. Would spend the extra 20 Euro for the smart, so you can switch it on/off via cell phone app. An inverter is connected directly to main load busbar and shut on/off via the electrodacus.
Instead of DSSR I would use a MPPT and as big and high voltage solar panels as possible which fit. Space is a premium on a boat and you need to harvest every mA you can get. The DSSR are fine for an offgrid house installation with lots of roof space but harvest much less then an MPPT and the low voltage will cause a big voltage drop till the DSSR.

[CaptainRivet]

Originally Posted by kenbo

I would use a bistable latching contactor. If that's not easily accomplished with your BMS I'd use an NC contactor. A charging and load bus are always good design features.

Electrodacus BMS has a different concept and way of working then most other BMS, it switches the sources that create load or charge via its factory remote on/off function and optimzes the battery management at the same time.

Like this you don't need big, unreialible and expensive (latching) relays as you switch on the low current and not the hot side.
The factory remote shut off is extensivly tested by R&D and extremly relaible compared to these high current relays.
To be able to isolate the battery completly i highly recommend to put an NH fuse directly after the shunts (they are on plus), this protects the bank as main battery fuse and the fuse can be easly pulled under load and acts as a cut off switch too. less conections, less points of faliure+voltage drop and much cheaper.

Electrodacus is not only a BMS, its a Battery optimizer too steering directly the sources and optimzing charge and discharge. Its the Single point of contact and the spider in the web for protecting the bank (BMS) and optimizing the battery management.
The parameter in the sources act as 2nd line of defense as Electrodacus manages all and they are only needed if it fails.

[johnmwalsh]

I wanted to keep a sla battery in front of the lfp for alternator protection from a disconnect at the lfp battery from hvd or lvd. How can I use the battery protects to disconnect charging and loads? I was thinking of using a battery isolator between the sla and lfp for disconnect. Would you happen to have a wiring diagram or pics that could lead me in the right direction? Thank you so much for your time.

[PaulCrawhorn]

Stop thinking of the batteries, visualise as separate circuits. One battery is not "in front of" the other, just the parallel connection control devices between the various circuits are opened or closed.

The alt-starterBatt circuit needs to be routinely isolated from the LFP-House circuit.

A DCDC charger is best for control, protecting the alternator from the too-high charging current draw from the LFP as well as delivering a healthy voltage.

If you put in a high power alt + expensive adjustable external VR for current-limiting instead, to send maximum current direct to the LFP-House circuit

then the Starter batt charging can be handled by any number of less expensive devices

but then you need a fancier (failure prone) solution for protecting the alt from routine LFP disconnects.

This can be simplified if you consider the lead Starter batt as sacrificial, replace it proactively on a schedule, choose a chemistry with the same charge voltage as your LFP, and wire House so it can if needed act as a backup starting bank.