PC Pro - UK 2021-12)

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Forstorage,IchosefourUS2000C
batteriesfromPylontech.Theseare
wellregarded,andareinstalledin
theirmanymillionsaroundtheworld.
TheunitsthatIchosearenominally
2.4kWheach,sowithfourthetotal
systemcapacityis9.6kWh.However,
tomaximisethelifeofthebatteries,
I’vesetthemaximumdepthof
dischargetobe85%,soinrealityI
havearound8.2kWhofstorage
available.Aslongasyoudon’tabuse
them,thebatteriesareguaranteedfor
tenyears.
Somepeopleinstallthesebatteries
insmallrack-mountcabinets(theyfit
abogstandard19inrack,andeven
comewithmountingears),but
insteadIchosetostackthemusingthe
specialbracketsavailablefromthe
manufacturer.Truthbetold,you
don’tactuallyneedthosebrackets:
thebatterieshaverubberfeet,and
willsitontop of eachotherjustfine,
providingadequateventilation.The
brackets do havetheadvantagethat
theycliptogether andsoprovide
additionalstabilisation. Thatwas
importanttomeasthebatteriesare
installedinmyutilityroom,where
theymightgetknocked.
TheTeslaPowerwall canbe
installedoutdoors,whichmany
peopledoforsafetyreasons.Youcan’t
reallydothatwiththePylontech
batteriesbecausetheirIPratingis
onlyIP20,whichmeansthey’re
touchproof buthavenoresistanceto
liquids.Theycertainlywouldn’tcope
withtheBritishweather.
I’mnotworriedaboutthe safety
aspect,though.TheUS2000Cis a
LiFePO4lithiumironphosphate
battery, andthese,ingeneral,don’t
explodeor combust.They havegood
thermalandstructuralstability,and
themainriskoffirecomesfromthings
suchasexternalshortcircuits.There’s
alsoa goodbatterymanagement
system(BMS),meaningthatinternally
eachindividualcellismonitoredand
protectedagainstovervoltage,
overtemperature,deepdischargeand

otherproblemareas.But

thisis more about protecting

thelifespanofthebatteries,

because comparedwith

otherrechargeable

technologies,LiFePO4is

inherently prettysafe.I even

Googled“pylontechfire”

andcouldn’tfind any

exampleslisted.I know

that’snota thorough

scientifictest,butitdoes

provide enormouscomfort

whenyouhavea stackof

thesethings in yourhouse.

Batteriesareobviously

DC,soneedamechanismto

convert from 2 40 V AC when

chargingandbackagain

whendischarging.Thereare

numerouscombinedbatterychargers

andinvertersonthemarket,butthe

oneI choseistheME3000SPfrom

SofarSolar.It’sverymuchseenas

theentry-levelproductinthis

marketplace,anddoeshavea few

disadvantages,butitalsohassome

pluses:it’srelatively cheap,readily

available,andhasanactiveonline

communityofferinghelpandsupport.

I’dcertainlyrecommendittoanyone

wanting to diptheir toes intothe

batterystoragemarketplace.

SteadyEddi

Themaindisadvantageofthisunitis

thatit hasa maximumcharge and

dischargerateof3kW. So if yoursolar

panelsaregenerating 4kW, you’ll

needtofindsomewhereelseto dump

theadditional1kWifyouwantto

avoidexport.That’swheremyEddi

comesin.Andsimilarly,ifyou have

lotsof appliances allswitched on at

thesametime(myovenalonewants

around7kWwhendoinga quick

heat-up),thenitcan’tallcomefrom

thebatteryso you’llendupimporting

someelectricityfromthegrid.

Someothermanufacturers allow

youtorunseveralinverters in parallel

togethigherloads,butwhenI looked

atmypowerloads I found my house

usuallyonlyexceedsthe 3kW

maximum fora fewminutesperday.

Itsimply wasn’t worthspendinga lot

moreona systemthatallowsparallel

inverters,orindeedon some of the

rivalunitsthathavea 5kWratherthan

a 3kWlimit.Formypurposesthe

SofarSolar doesjustfine,eventhough

ithasa clunkyuserinterface.

A coupleoffinalpointsthatare

worthbearinginmind. First,evenif

forsomereasonyoucan’tfitsolar

panelstoyourproperty,youmight

stillbe able to makegooduseof

batterystoragebysigninguptoa

TimeofUse(TOU) electricitytariff

suchasOctopusGo.Thatwayyou

canchargethebatteriesovernight

whenyou’repayingaround5pper

kWhforelectricityandthenuse

themtopoweryourhouseformuch

oftherestof thedaywhenelectricity

fromthe grid is moreexpensive.

That’sa green thing,too – you’re

avoidingpeakgridloading.

Second,allofthekitI’vewritten

aboutneedsan activegridconnection.

There’sotherstuff outthereforpeople

whowantto go completelyoff-grid.

Thekeytoa goodsetupisgetting

theenergyflowscorrect.There’sno

pointintakingelectricityfromthe

gridtoheatmyhotwatertank,for

example,becauseit’stheretosave

gas,andelectricityismoreexpensive

thangas.Similarly,chargingthecar

hasto take priorityoverbattery

storageandtank heating because

petrol is moreexpensive(anddirtier)

thaneitherelectricityorgas.

Ina futureissueI’llwriteabout

someRaspberryPi-basedtoolsI use

thatgivemebettercontrolover

energyflows, andinparticularover

mybatterychargingandusage,

butfornowI’llsignoffbecauseI

promisedlastmonththatthiswould

onlybea two-parter!

“Thekeytoa

goodsetupis

gettingthe

energyflows

correct”

ABOVEThePylontech

batteriesareavailable

withclipstokeep

theminaneatstack

BELOWFormost

ofthedaymyhouse

isrunningon

batterypower

@PaulOckenden