Powering the pond

[dmsims]

Hi all, I have started out on a project to power my pond and ancilliaries which are on 24/7. I've already replaced both pumps with much lower wattage versions and expected total draw is around 400 watts (2 x pumps , UV, Camera , Drum filter)

Power is currently provided via a shed which is powered from the main house via armoured SWA and a 2 circuit consumer unit



This where I am now, the gap on the left is for a Victron Multiplus 24/800 and outside there will be 2 x 360W panels

8 x 200aH cells, Smartshunt, Overkill BMS, bit of wire tidying left!

Only panicky moment was when moving the wiring I dislodged a bad crimp and the BMS showed all cells at 0.1V
Will never use the crimp on a wire cutter again and redid all of them with a ratchet crimper



On the AC side I plan to "Hijack" one of the circuits from the exisiting CU and put that in a brand new mini CU isolated from the house AC



Once I have the inverter/charger I plan to use scheduling since in the UK there are tariffs where elecrticity is much cheaper e.g. between 20.30 - 01.30 it is one third the price

Pond inhabitants:

 

[AntronX]

Use thicker wire on battery side of Victron charge controller.

 

[rmaddy]

Use thicker wire on battery side of Victron charge controller.

For a 30A SCC you only need 10AWG/6mm² for such a short run. Can't tell what the OP actually has but what were you proposing?

 

[AntronX]

6 gauge to reduce voltage drop so that charge controller does not go into absorption mode too soon. This way you could limit battery voltage to 3.44v per cell during bulk and absorption mode to extend battery life and still get full charge quickly.

 

[dmsims]

Use thicker wire on battery side of Victron charge controller.

Thanks for the feedback - the existing 6mm2 cable is rated to 48A

Edited - I don't mind upgrading it - just want to understand

 

[AntronX]

You need a bit more than the rating for this purpose to keep voltage drop low so batteries can get a full charge quicker. If there is a significant voltage drop on the controller to battery path the controller will go into absorption mode sooner. Does your BMS support setting custom balancing shunting voltages?

 

[dmsims]

It's an Overkill BMS set to 3.5v max

I can't give any meaningful information about charging ATM as I have no means to discharge.........

It's all hooked up to Victron VRM via a Pi 3+ so when the inverter is installed we should be able to see what's happening

 

[dmsims]

UPDATE

So supply problems with the Multiplus, the original order is not in stock and Victron are going to take 2+ months to fulfil, tried other retailers -same story
The original retailer is going to upgrade to a 24/1200 (which Victron do have) for cost price

In the meantime I have bought a cheap 24v/2000W inverter locally to get things moving



I setup an Alarm in VRM for when the Battery voltage reached 3.10V per cell

Voltage: 24.69 V
Low limit (hysteresis): 24.80 V (25.00 V)
High limit (hysteresis): 28.00 V (27.60 V)
Wait time: 60 seconds

Site time: 2022-06-04 06:39:08 UTC
UTC time: 2022-06-04 06:39:08 UTC

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Now I could do with some advice as when I then went and checked the BMS the cell divergence was more than I was expecting:

(at this stage the Smartshunt was reporting 25% capacity)