Idiot's guide to a self build battery

[Stinsy]

I do similar to take my Pylontechs out of DC circuit, but it is a bit of a PITA. In my case at the low cut off voltage there is only a handful of amps flowing.

Wouldn't mid details on that set up Nowty. Looks like a logic switch and a relay/coil driving a mechanical make/break connection? Is the logic side 230Vac?

The white din mountable device looks like a GEYA voltage sensitive relay.

[nowty]

Wouldn't mid details on that set up Nowty. Looks like a logic switch and a relay/coil driving a mechanical make/break connection? Is the logic side 230Vac?

It all runs off the 48V DC battery, the logic switch is a voltage level sensing relay.

Its something like this,
https://www.aliexpress.com/item/1005006147916320.html

And the DC Relay is an Allbright 48V SP NC relay.

I probably will have no use for it once I've sold my Pylontech's so you can have it for the cost of postage shortly.

[Joeboy]

Wouldn't mid details on that set up Nowty. Looks like a logic switch and a relay/coil driving a mechanical make/break connection? Is the logic side 230Vac?

It all runs off the 48V DC battery, the logic switch is a voltage level sensing relay.

Its something like this,
https://www.aliexpress.com/item/1005006147916320.html

And the DC Relay is an Allbright 48V SP NC relay.

I probably will have no use for it once I've sold my Pylontech's so you can have it for the cost of postage shortly.

That would be smashing Nowty, I'm grateful!

[Joeboy]

An adjustable voltage sensitive no relay that can break under load would be nice. Would have to hook it up on battery side so it broke at say 50.1V. This may become more of a PITA than its worth.

Not yet though!

Yes a voltage sensing relay would be my next idea:

Possibly something like this:-

https://www.aliexpress.com/item/1005005849772632.html

I've not used on of these, but it looks like it would work. It will operate off 6-80v dc, and the contact is rated at 30A. Looks a bit fiddly to set up but hopefully you only have to do that once.

It can be set as active high or low, so if it's powered from the charger side, not the battery, and you use the NO contact, it cannot close the contact unless the charger is on. If it is then set to close the contact if volts (sensing battery side voltage) are <=50.4 then open at 50.5 it should work. In theory.

As the ideal diode is coming anyway, you could connect it between the relay and the battery as belt and braces in case the relay doesn't operate as planned whilst setting up. As the relay can only close when the charger is on, the ideal diode should be well within its 40v rating.

Thank you Marcus,I shall read this at the big screen and get my crayons out to understand it. Thank you!

[Joeboy]

Just heard back from the seller in China and he says no problem. The extra few Volts won't do any damage. I'll still put the diode in anyway. Even if it's just jewellery.

Not quite feeling brave enough today though.

[Joeboy]

A rainy day here, varying from 500W to 1kW incoming. Curry is cooking on the WBS low & slow.

A good time to try out the additional charger. Good news, no magic smoke! It kicks in below 50V stack charge which is around 80% soc.

To flip that on its head this means that the charger will assist up to 80% soc and the Goodwe hybrid will then continue on its own up to 100% soc.

Current flow seen from the add on charger is around 20A (1 kW) so far. It won't set the world on fire but it's enough of a lift for my purposes. Last few days we've hit 90 to 92% soc by 05.30 hrs. Will be looking for 100% soc tomorrow. The charger is set to run off a scheduled hive plug 23.30 to 03.30hrs. The stacks hits 80% soc sometime between 03.00hrs to 03.30hrs. It's handy having those soc graphs to look back on.

[Joeboy]

Battery is drained a little now as exporting. Tested again and it's closer to 1.5kW charge rate Pretty good for a golf cart charger!

That will give us 20% stack charge on its own across the charging window and weirdly opens up EV to contributing too.

A shame the EV is stuck in an Aberdeen garage waiting on warranty front suspension arms.

[Joeboy]

A nice start to the day, battery stack had went from 17% soc to 99% soc within the charging window. I'll leave it on its daily schedule, looks like a nice simple way to get that extra bit into the tank. The stack hit 80% soc at 02.20hrs. It will be great in Winter for running the ashp.

If I chose to I could also use the EV battery to run the add on charger, to charge the stack, to export to grid (or top up for a Winter hungry ashp). Can't see that becoming a thing but it's one more interconnect in place within the home. I will try it least once.

If anyone is interested for their own system? It is a chunky unit with a good cooling fan and excellent fins. Good quality flexible cables too along with an Anderson connector. All in all, a great, well built bit of kit. It should pay itself off incl postage in a little under 1.6MWh. About 6 months time.

https://a.aliexpress.com/_EvQESLO

Nowty, thank you very much for the logic switch offer but it looks like we're good.



Edit-
By completing the loop between EV and house stack which is V2H-G we raise the non intervention stack charging rate to 5.4kW (3.9+1.5) and the potential storage to 115kWh of battery. The potential export on that is in theory 70kWh in the 18hr window without solar if i get up at 05.30 and connect the EV (unlikely). The true charge rate of that 115kWh combined battery stack is 3.9+1.5+7.2 = 12.6kW. All for a £90 charger.

I am unlikely to go chasing this for export money but can see the scenario being used when the ashp is chewing through the stack in Winter. I'll be glad of it then.