Tue, 19 Dec 2023 08:18:57 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295310#Comment_295310 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295310#Comment_295310 Sat, 12 Mar 2022 22:18:58 +0000 jhsigma http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295311#Comment_295311 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295311#Comment_295311 Sun, 13 Mar 2022 09:36:32 +0000 revor Posted By: jhsigmaBeen told that the maximum power I can put into my proposed solax battery is 2 kw in and out is this the same with all batteries ? what is the restriction?

Simple answer is No all depends on the inverter and battery combo. Can only speak of my system which has 6 Kw inverter and 10 kw battery. The charging and discharging of the battery will be limited by the current as the discharge and charge is done at the battery voltage typically anything between 40 to 60 V so from a cable sizing alone it would mean big CSA (cross sectional area) to deal with the high amperage involved. My battery will discharge 5kw and can charge at up to 5kw but typically the battery management system and the inverter will vary this depending on the state of charge (SOC) of the battery. If battery is flat will trickle charge up to about 20% then typically at about 3.5 kw up to about 80% then will charge / discharge depending on the state of each cell.
As for having a new transformer will I suppose depend on what the grid will take. My understanding is that you only pay for an upgrade if you want to export more than 16A (3.68kw at 230V) you may have to cough up. You are as I understand entitled to export up to 3.68 kw without any need for you to pay to upgrade the network. I think you would be better off having bigger battery storage and limiting export to 16A than paying towards a new transformer which would be expensive. How are your panels arranged if E W you may never be in big export territory anyway]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295312#Comment_295312 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295312#Comment_295312 Sun, 13 Mar 2022 09:42:09 +0000 Ed Davies
Also, the inverter/charger attached to the battery will have a power limit.

Similarly, there's an upper limit on the amount of power you and your neighbours can put into the local distribution network before that'll reach too high a voltage. By rights you can put in 16 amps per phase (which corresponds to 3.68 kW at 230 V), if you and your neighbours all putting in that amount results in the voltage getting too high then it is the distribution network operator's (DNO's) responsibility to modify the network at their expense. They can tell you to stop feeding in while they do it but that's only temporary.

If you want to put in more than 16 A then the DNO needs to check if that'll be alright before hand. They have to bear in mind that if they give you permission to put in more then all your neighbours get PV or wind turbines or whatever and also put in their 16 amps then they'll be met with the expense to upgrade the network so it's only in their interest to give you permission if there's plenty of headroom available.

Two other approaches if you have more than 3.68 kW of panels:

1) Have a smaller inverter or configure the inverter to not output more than 3.68 kW thereby ensuring that the 16 A limit is met. Given that the panels only produce around their peak output for a very small part of the time (and usually when there's less need for energy anyway) this is a quite sane and common approach.

2) Have the inverter wired up with gubbins which the DNO is happy with to make sure that the export is limited to 16 A even though the panels are generating more because the difference is being used in the house to charge the batteries or for other useful purposes like normal domestic use, heating hot water or charging an EV.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295316#Comment_295316 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295316#Comment_295316 Sun, 13 Mar 2022 14:07:40 +0000 WillInAberdeen
I've seen rules of thumb that lead-acid batteries should be charge/discharged at max 10% of capacity per hour and lithium at max 50% per hour (IE for a 4kWh lithium battery that would be 2kW max in or out, which seems a reasonable match to a domestic solar array, but not enough for an electric shower)

That implies at least 2 hours to charge a Li battery. But some high-power EV 'rapid' chargers claim to charge much faster, eg in the time it takes you to take a motorway break. Any ideas how that works?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295317#Comment_295317 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295317#Comment_295317 Sun, 13 Mar 2022 14:28:29 +0000 philedge Posted By: jhsigmaBeen told that the maximum power I can put into my proposed solax battery is 2 kw in and out is this the same with all batteries ? what is the restriction? still awaiting decision from network company for 18 panels ,supplier says I may be asked to buy a larger transformer any one else had this ?

Were just in the throws of adding a second 16A limited system to give us 2x16A output to grid. Informal discussion with DNO so far reveals that our pole mounted transformer is undersized by their current standards so is getting upgraded from 5KVA to 25KVA at the DNOs expense. I think this is part of grid reinforcement for future EV/heat pump loads. The existing 5KVA transformer sounds a bit light on capacity but thats what the DNO says is there.

To keep us under the max voltage limit of 253V the transformer is being tapped down by 2.5% so that when the PV is generating it wont push the voltage over the 253V limit. All at no cost us! Only thing that we have to do is provide a disclaimer that we take reponsibilty for the reduced voltage which is still well above the UK standard of 230V.

Might be worth some subtle discussion about existing transformer capacity for future heat pump/EV loads. Im guessing all DNOs have a degree of gov funding for bolstering network capacity for much larger future electric loads??]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295318#Comment_295318 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17416&Focus=295318#Comment_295318 Sun, 13 Mar 2022 15:05:37 +0000 Ed Davies Posted By: WillInAberdeenThat implies at least 2 hours to charge a Li battery. But some high-power EV 'rapid' chargers claim to charge much faster, eg in the time it takes you to take a motorway break. Any ideas how that works?Yep, there are varying claims for various lithium batteries and it depends to some extent on how conservative the manufacturer is if they'll claim charging in 1 hour or 2 or whatever.

EV batteries are usually different from energy storage batteries, though. Typically, domestic batteries are LiFePOâ‚„ whereas EV ones have nickel, cadmium and other stuffs of dubious origin in them. Also most EV batteries have liquid cooling which is not so common in domestic batteries. Also also, that fast charge of EV batteries is typically only to 80% capacity.]]>