RV camper electrics for review

[Peter]

Hello guys, if you find little time, I would be grateful for your feedback on my electrical design in the van. There are a few things I haven't seen anywhere else. ;-)

https://docs.google.com/drawings/d/1qYhP9BSZgqCqVNMfGxng1hFc_rXr4rki_F04bAA9R2w/edit

[Plamen]

   Hi Peter, 

You have to remove that 250A fuse and the 200A breaker or You'll damage SBMS0 if/when any of them is open circuit.

[Peter]

Hello Plamen,

are you sure I have to remove fuse and breaker from the battery? Even Dacian has in SMBS manual these kind of breakers (see picture on page 3). Could you explain more please?

Dne neděle 9. května 2021 v 16:48:56 UTC+2 uživatel Plamen napsal:

[Dacian Todea]

Peter,

Palmen is right those two need to be removed and installed in another place. There should be nothing between the two current shunts as shown in my user manual page 3 the shunts have a common connection point with nothing between them.

[Plamen]

Yes i'm sure. Just looked at page 3, Battery+ is connected to first shunt , then the next shunt and nothing between them. Now the reason for that is (not sure if i'll explain it correctly) if you open the breaker or fuse is blown nd there was some significant load connected, the shunt gets below the Batt.(-) because of the energy stored in the cable and will damage the shunt amplifier inside the SBMS. Dacian has explained it many times on the forum.

[Dacian Todea]

Plamen,

In this particular situation current can flow in to or out of the battery depending if there is a larger load or a charge source.  In case of higher charge source the voltage on PV shunt when disconnected will increase to well above battery voltage can be hundreds of volts depending on what can clamp that energy so current shunt amplifier can be damaged that way as it is designed for max 100V transient or if there is a higher load then voltage in that point when disconnected will become negative and then that will damage the current shunt amplifier.

[Peter]

After diving into the forum I see it is quite a common mistake to put fuse or breaker between the shunts.. :-) Thank you very much for pointing that out for me, I have adjusted the layout.

https://docs.google.com/drawings/d/1qYhP9BSZgqCqVNMfGxng1hFc_rXr4rki_F04bAA9R2w/edit

Although I have DSSR20 on my desk, I am thinking about Victron MPPT for theoretically better overall efficiency, every watt will count for my purely electric van build. I am thinking that in central Europe and with solar panels on the van (most of the time sub-optimal positioning of PVs) Victron MPPT will be more effective than DSSR20, right?

Dne neděle 9. května 2021 v 19:29:10 UTC+2 uživatel electr...@gmail.com napsal:

[Dacian Todea]

Peter,

If those in diagram are your panels 72 cell panels then yes MPPT will offer maybe as much as 20% extra power as 60 cell panels will be ideal used with 8s LiFePO4 battery then DSSR20 will be in average as efficient as the MPPT. The position of the panel has nothing to do with MPPT or DSSR20 they will both perform the same if they had 60 cell panels.

Not sure that 200A breaker is capable of that even if is just a thermal breaker and you will need to precharge the inverter capacitors before switching tha ON else it will damaged for sure.

[Peter]

OK, thank you for confirming MPPT would be better option in my situation.

I would love to implement inverter precharging but it would have to be automatic.

My intention is to be able to remotely/automatically turn the inverter on and off because:

- remote on before using some kitchen appliance (cook top / microwave /...),

- automatic on when battery is full free solar energy can flow into the AC boiler through the inverter,

- automatic off when there is no load on the inverter for some period of time.

To implement automatic precharging I would need some very good relay between battery and inverter capable of continuous 150A and with minimal contact resistance.

Would you know about such relay?

If I would go without inverter precharging, what are disadvantages? Shorter lifetime of both inverter and battery?

According to parallel discussion https://groups.google.com/g/electrodacus/c/hQCzKtIbQJk, I have replaced chinese breaker between battery and inverter with only simple battery isolator. Would someone suggest different setup?

https://docs.google.com/drawings/d/1qYhP9BSZgqCqVNMfGxng1hFc_rXr4rki_F04bAA9R2w/edit

According to local regulations, I should have accessible battery isolator that completely disconnects the battery. But I guess its not possible with SBMS0 that needs shunts directly on battery? Is it possible to put battery isolator on negative side of the battery?

Dne pondělí 10. května 2021 v 21:42:09 UTC+2 uživatel electr...@gmail.com napsal:

[Nils]

Hi Peter,

I don't know your local regulations so this is just a guess: But considering that of the shelf batteries also contain a BMS inside the box would make me think, that it would be okay to integrated any disconnect switches AFTER the battery shunt / pv shunt. SBMS0 becomes part of your battery and therefore alway will stay connected to the battery bank. Otherwise the local regulations would require you to disable an integral safety feature of your power system, which seems unintuitive.

Best regards,

Nils

PS: I am going for the same setup (all electric van) and will use DSSR20. MTTP can be added any time (if necessary, which I don't think it will be).