Immersion boost & Tesla Powerwall

[Gareth J]

Gas price is rising a lot more than electric. Still cheaper than electric for heating but any you can displace with diverted power is a bonus.

I'd assumed every self respecting battery management system would have a function to; close a relay if battery is full (or whatever you call full), until battery is to an lower preset level. Not the case?

If this was available, while imperfect, you could simply connect the immersion to said output relay and have it clunky on/off, while keeping the battery almost full.

[Oldgreybeard]

I'd assumed every self respecting battery management system would have a function to; close a relay if battery is full (or whatever you call full), until battery is to an lower preset level. Not the case?

Ours seems to do this. The battery shuts off at 100% and won't start to accept a charge again until the SoC has dropped to around 95% - 96%. Not unusual to see the battery at 97% - 98% (having been at 100%) and have surplus power going to the grid rather than topping the battery right up again. Presumably it does this to avoid having the battery get to 100% several times during the same day.

[Stinsy]

Gas price is rising a lot more than electric. Still cheaper than electric for heating but any you can displace with diverted power is a bonus.

I'd assumed every self respecting battery management system would have a function to; close a relay if battery is full (or whatever you call full), until battery is to an lower preset level. Not the case?

If this was available, while imperfect, you could simply connect the immersion to said output relay and have it clunky on/off, while keeping the battery almost full.

It'd be great to have some sort of integration between inverter and smart-plugs so that the plugs could be turned on and off with battery charge percentage.

Eg turn AC on when battery charge percentage is above 90% and off when charge drops below 80%.

[Joeboy]

Gas price is rising a lot more than electric. Still cheaper than electric for heating but any you can displace with diverted power is a bonus.

I'd assumed every self respecting battery management system would have a function to; close a relay if battery is full (or whatever you call full), until battery is to an lower preset level. Not the case?

If this was available, while imperfect, you could simply connect the immersion to said output relay and have it clunky on/off, while keeping the battery almost full.

It'd be great to have some sort of integration between inverter and smart-plugs so that the plugs could be turned on and off with battery charge percentage.

Eg turn AC on when battery charge percentage is above 90% and off when charge drops below 80%.

I would think that could be put together. Alibaba will have a unit that does it? They seem to have everything!

[Oldgreybeard]

Gas price is rising a lot more than electric. Still cheaper than electric for heating but any you can displace with diverted power is a bonus.

I'd assumed every self respecting battery management system would have a function to; close a relay if battery is full (or whatever you call full), until battery is to an lower preset level. Not the case?

If this was available, while imperfect, you could simply connect the immersion to said output relay and have it clunky on/off, while keeping the battery almost full.

It'd be great to have some sort of integration between inverter and smart-plugs so that the plugs could be turned on and off with battery charge percentage.

Eg turn AC on when battery charge percentage is above 90% and off when charge drops below 80%.

Very easy to do this with Home Assistant, the functionality is pretty much built in, and it will control a wide range of off-the-shelf "smart" plugs easily enough. I have a small IR remote in our bedroom, that's connected to HA via WiFi, and that can turn the bedroom aircon on, off, or change the mode or temperature, depending on anything that HA has via a sense or control integration.

[Gareth J]

Gas price is rising a lot more than electric. Still cheaper than electric for heating but any you can displace with diverted power is a bonus.

I'd assumed every self respecting battery management system would have a function to; close a relay if battery is full (or whatever you call full), until battery is to an lower preset level. Not the case?

If this was available, while imperfect, you could simply connect the immersion to said output relay and have it clunky on/off, while keeping the battery almost full.

It'd be great to have some sort of integration between inverter and smart-plugs so that the plugs could be turned on and off with battery charge percentage.

Eg turn AC on when battery charge percentage is above 90% and off when charge drops below 80%.

Precisely. It seems so obvious that I'm surprised it isn't a feature of them all anyway

[openspaceman]

It'd be great to have some sort of integration between inverter and smart-plugs so that the plugs could be turned on and off with battery charge percentage.

Eg turn AC on when battery charge percentage is above 90% and off when charge drops below 80%.

I tried to discuss this early on when I joined as an alternative to forking out for an Eppi.

The first problem I had is that the SOC reported by my Growatt system does seem to reflect on the present charge or discharge state that accurately and I still have not decided whether this is because the SOC reported by the battery is derived in part at least by an integration of charger-discharge current. The actual Voltage reported would also be dictated by the battery and connections' internal resistance. I imagine pylontech batteries are more amenable to accessing the information directly.

Next thing I wonder is if you did manage to start switching another circuit at ~100% SOC and run it down to 80% SOC and then switch off, how much would that taking the top off the charge reflect on the anticipated 6k charge-discharge cycles we are told to expect to get out of the battery?

If at the same time the sun were shining sufficiently to satisfy the newly switched load then the battery would not need to discharge; which brings me to thinking what are the energy losses in a hybrid system where the battery sits on the DC side compare with what Joeboy does, and I plan to do, which is to directly charge my battery from extra panels via an mppt DC charger, in effect the current could run directly from the charger through to the ac coupled inverter without going into the battery (as long as the ac load is present as the battery inverter cannot export).

In much the same way a car alternator may keep the voltage at ~14V when running with lights on but most of the current never goes to the 12V battery but is used by the car electrics directly with the current regulator of the alternator field controlling output voltage.

[sharpener]

Gas price is rising a lot more than electric. Still cheaper than electric for heating but any you can displace with diverted power is a bonus.

Surprisingly, heating the water with an oil boiler is only 2/3 the cost of off-peak electricity at current prices where we are.

So battery charging has priority, if there is not enough "export" to heat the tank the boiler is timed to do it after sunset. This thermostat is set lower than the immersion thermostat to allow for a 5 deg drop in temperature before it cuts in.

The solar priority is determined by which CT is nearer to the incoming grid connection. So when the Victron thinks it is "exporting" actually the immersion is grabbing the power before it gets to the grid (even though the actual circuit is downstream of the inverter).

[sharpener]

Gas price is rising a lot more than electric. Still cheaper than electric for heating but any you can displace with diverted power is a bonus.

Surprisingly, heating the water with an oil boiler is only 2/3 the cost of off-peak electricity at current prices where we are.

UPDATE: Just got the new pricing from Scottish Power wef 1/10/22.
Daytime units are up from 35 to 45p, night-time units are down from 16p to 11. Still above oil (9p) but sufficiently close for it not to matter, also I don't know what the replacement cost of the oil sometime next year will turn out to be.

[nowty]

UPDATE: Just got the new pricing from Scottish Power wef 1/10/22.
Daytime units are up from 35 to 45p, night-time units are down from 16p to 11. Still above oil (9p) but sufficiently close for it not to matter, also I don't know what the replacement cost of the oil sometime next year will turn out to be.

That beats Octopus E7 rate by about 4 p for the cheap slot.