SPF 3000TL HVM System questions..

[Athens Jim]

Hey guys..
after searching the web for weeks and seeing this forum constantly pop up.. i figured its time to sign up and introduce myself and ask for help..

My name is Jim ( obviously ).. originally from PA, and currently retired and living in Greece.. yup.. as in Europe..

never had experience with autonomous homes until i got here so bare with me while i fill you guys in..

my current 3KVA-PWM hybrid inverter is an entry level unit that came with the house when i bought it 06/2021.. it was used as a weekend house until i bought it, and has a generic china based inverter that has proven reliable in spite of it current $250 price tag... home has oversized wood stove for heat, and LPG for hot water and cooking..

but the batteries, 4x12v/250AH in 2s2p (24v/500ah) and panels 255 x 8 were upgraded by me last year due to my increased demands as a permanent residence..

and here is where i am in need of assistance..

im yanking the inverter and batteries and moving it to the garage for power independant of the house, and upgrading the home system so i can stop worrying about running the coffee pot (1000 watts) and electric water supply well pump (850 watts) at the same time, cause if the chest freezer and fridge happen to be running or kick on at that time.. i get an overload and the inverter restarts killing all power to the house obviously..

so ive chosen the growatt spf-3000tl-hvm-24, i have purchased 2 for now, (possibly 3 in the future) to run in parallel to a single battery bank and have the option of 12 x sopzs 2v/605ah, 15kw storage, or 2v/965ah 24kw storage batteries, ide really like to go ahead and buy the 24kw batteries, but i am worried about charging, over panelling, recharge capability, ect...

i intend to double the storage next year as funds become available..

i already have 8 panels up there, but i own 30 total of the same 32v/255 watt panels total, they were pulled from a "contract issue" 20 yr lease with the gov here so theyre old but showed an average 90% and better production, 7 amps or more each..

4 facing east, and 4 facing west, 15* roof angle, only during mid day are all 8 seeing full sun even though they are at an angle amp meter showed good production, but obviously morning hrs and afternoon hrs im seeing about 50%

what would you guys recommend in my situation? pros? cons?

1) 25.5v/605ah or 25.5/965ah batteries?
2) leave the panels as is and just swap in the growatts, or add panels to the growatts and in which configuration?
3) run 90% PV thru inverter and add panels thru another MPPT? ( my 1st choice) because as i mentioned, leaves room to grow next year when i add another dozen batteries


and now for some details..
my surge load demands are 3500-4400 watts with everything on at once. MAX demand.. i tested this using the genset by dropping the breaker for about an hr to insure the freezer and fridge were going to kick on again, turned everything on, inside and outside lights that are LED, coffee, water well pump, on demand water heater, and the washing machine on spin, and flipping the breaker on again, MAX load jumped several seconds up to 4400 watts, and settled down to 3950 for several minutes until dropped to 2400-3100 steady probably due to teh washing machine spin cycle changing directions..

my AH draw overnight during normal home use without worrying about anything is 8kw, under current budgeting situations, i drop down to 5kw overnight

also worth noting, i have a backup auto start diesel genset that up to now, has saved the batteries several times from -65% DOD during consecutive cloudy days..

its the charging, recharging to capacity that throws me off and need help... so any advice you guys have, ide appriciate enough to pick up the first round if we ever meet up

 

[sunshine_eggo]

1) Link batteries. Their specs matter. Lead acid needs to be charged in a range. Too much or too little is bad for them.

For 2000W array:

2000W/24V= 83A.

WIthout manufacturer data, assume:
Low end of charging is about 0.08C.
High end of charging is about 0.15C.

Bank should be between 83/.15 = 553Ah and 83A/.08 = 1037.5Ah

Adding more panels might overcharge your battery.

Additionally, if batteries are not in a temp controlled environment at 25°C, the chargers should be capable of temperature compensation with temperature sensors on the battery. I don't recall seeing that on the Growatt units.

2) Link inverter. Elaborate on available PV mounting options. You have 4E and 4W, can you add to those arrays at those same orientations, or do you have to mount elsewhere.

3) Exploit all available MPPT amperage first. Overpanel second.

 

[Athens Jim]

hi..
thanks for replying.. the panels would be mounted in the same orientation.. W/E and can fit all 30 up there if need be..

now when you say, exploit all MPPT amperage first... i dont understand how to do that, i am new to MPPT, volts vs amps vs watts.. etc...

the MPPT charger in the growatt is as follows.. and x 2 if i can use both inverters to charge the same battery bank??

max PV array power = 1500watt
mppt operating voltage = 30v-80v ( do i wire 2s = 64v?)
max pv OC voltage = 102v ( do i wire 3 in series = 103.89v?)
max solar charge current = 50amp ( do i wire parallel for max amps at what voltage?)
efficiancy = 98%

i cant seem to figure it out, v/ah to watts, v/w to ah... to configure for max voltage and max amps for watts

how would i configure OC 34.63v/255 watt panels for this?

i am using 32v because mid day the panels put out 30-32 volts, 6.80-7.30 amps each.... my current config is 1s/8p due to inverter requirements.. OV 20v-40v, 80amps max pv charge, so i am pushing 32volts x 56 amps..

my simple brain is telling me i am more restricted with MPPT but i know i am wrong, i just cant seem to figure it out...

and yes.. components and batteries are in a temp controlled room

and lastly, given that i have mentioned the panel specs, can i still run the larger battery bank? 25.5/965ah

 

[Athens Jim]

battery specs

 

[timselectric]

so ive chosen the growatt spf-3000tl-hvm-24, i have purchased 2 for now, (possibly 3 in the future)

At 6kw to possibly 9kw, I would recommend you go with a 48v system. To keep wiring from being extra large. And increase efficiency.

 

[timselectric]

Also
Volts x amps = watts.
Amps x hours = ah
Watts x hours = wh

 

[Athens Jim]

Tim..
thanks for replying.. i prefer 24v for cost vs redundency purposes...

i believe..

there is no redundency in 48v unless you have a BIIIIG wallet.. i believe the same results are accomplished with 2 x 24v systems in parallel and have redundancy with the same cost.. minus ofcoarse thicker battery cables

the inverters ($650 each) in parallel can be rewired for single in an emergency, as opposed to a single 48v 5k-6k inverter of the same price going down and no power.. modern tech is great until it isnt then its a nightmare...

also, 2 x 24v banks, each can be put out of service in case of a bad cell drawing power from healthy cells as opposed to 1 x 48v bank having a cell removed and being forced to work with reduced capacity, a cell removed..

 

[sunshine_eggo]

hi..
thanks for replying.. the panels would be mounted in the same orientation.. W/E and can fit all 30 up there if need be..

now when you say, exploit all MPPT amperage first... i dont understand how to do that, i am new to MPPT, volts vs amps vs watts.. etc...

You max out your MPPT capacity before you overpanel either.

the MPPT charger in the growatt is as follows.. and x 2 if i can use both inverters to charge the same battery bank??

Yes. Parallel inverters MUST be powered by the same bank.

max PV array power = 1500watt
mppt operating voltage = 30v-80v ( do i wire 2s = 64v?)
max pv OC voltage = 102v ( do i wire 3 in series = 103.89v?)

NEVER exceed Max PV Voc value AND allow for cold temperature margins.

What is your panel Voc?

max solar charge current = 50amp ( do i wire parallel for max amps at what voltage?)
efficiancy = 98%

i cant seem to figure it out, v/ah to watts, v/w to ah... to configure for max voltage and max amps for watts

how would i configure OC 34.63v/255 watt panels for this?

2S3P will be the maximum the MPPT can actually utilize, but you could go 2S5P for overpaneling.

i am using 32v because mid day the panels put out 30-32 volts, 6.80-7.30 amps each.... my current config is 1s/8p due to inverter requirements.. OV 20v-40v, 80amps max pv charge, so i am pushing 32volts x 56 amps..

I'm guessing the old controller is PWM and not MPPT, thus you are forced to use panels in parallel.

my simple brain is telling me i am more restricted with MPPT but i know i am wrong, i just cant seem to figure it out...

Totally opposite. PWM forces you to use panels at the appropriate voltage. MPPT gives you option of higher input voltage.

and yes.. components and batteries are in a temp controlled room

and lastly, given that i have mentioned the panel specs, can i still run the larger battery bank? 25.5/965ah

With 2X 50A controllers, that provides 100A total potential charging. I don't see charge current specs for the batteries, so I'll stick with .08-.15C meaning, 100A/.15 = 667Ah to 100A/.08 = 1250Ah.

Tim..
thanks for replying.. i prefer 24v for cost vs redundency purposes...

Tim's right.

Not sure I follow you. At least here in the states there is negligible cost difference between 24V and 48V on the inverter side, and you get double the PV power since you only need half the current, i.e., a 50A controller on a 48V battery can do about 2500W.

i believe..

there is no redundency in 48v unless you have a BIIIIG wallet.. i believe the same results are accomplished with 2 x 24v systems in parallel and have redundancy with the same cost.. minus ofcoarse thicker battery cables

There are almost certainly the same 3000W versions of those inverters in 48V at nearly identical cost. As per above, parallel inverters MUST run on the same battery.

Using individual 2V cells means you already have redundancy. If a single cell is lost, you can take it out of the bank and alter your charge parameter and keep going with -1 cell until you can replace it.

the inverters ($650 each) in parallel can be rewired for single in an emergency, as opposed to a single 48v 5k-6k inverter of the same price going down and no power.. modern tech is great until it isnt then its a nightmare...

Again, there are 3kW/48V inverters.

also, 2 x 24v banks, each can be put out of service in case of a bad cell drawing power from healthy cells as opposed to 1 x 48v bank having a cell removed and being forced to work with reduced capacity, a cell removed..

Your logic is flawed. Lose a cell on a 48V system and you've only lost 1/24 = 4.2% of your capacity.

If a single cell fails on a 2X 24V system, you either have to take one whole battery offline, losing 50% of your total, or take 2 cells out - 1 out of each.

Again, third time, to make sure it sinks in, both parallel inverters MUST be run on the same battery bank.

 

[Athens Jim]

You max out your MPPT capacity before you overpanel either.



Yes. Parallel inverters MUST be powered by the same bank.



NEVER exceed Max PV Voc value AND allow for cold temperature margins.

What is your panel Voc?



2S3P will be the maximum the MPPT can actually utilize, but you could go 2S5P for overpaneling.



I'm guessing the old controller is PWM and not MPPT, thus you are forced to use panels in parallel.



Totally opposite. PWM forces you to use panels at the appropriate voltage. MPPT gives you option of higher input voltage.



With 2X 50A controllers, that provides 100A total potential charging. I don't see charge current specs for the batteries, so I'll stick with .08-.15C meaning, 100A/.15 = 667Ah to 100A/.08 = 1250Ah.



Tim's right.

Not sure I follow you. At least here in the states there is negligible cost difference between 24V and 48V on the inverter side, and you get double the PV power since you only need half the current, i.e., a 50A controller on a 48V battery can do about 2500W.



There are almost certainly the same 3000W versions of those inverters in 48V at nearly identical cost. As per above, parallel inverters MUST run on the same battery.

Using individual 2V cells means you already have redundancy. If a single cell is lost, you can take it out of the bank and alter your charge parameter and keep going with -1 cell until you can replace it.



Again, there are 3kW/48V inverters.



Your logic is flawed. Lose a cell on a 48V system and you've only lost 1/24 = 4.2% of your capacity.

If a single cell fails on a 2X 24V system, you either have to take one whole battery offline, losing 50% of your total, or take 2 cells out - 1 out of each.

Again, third time, to make sure it sinks in, both parallel inverters MUST be run on the same battery bank.

hmmmm.... after letting this sink in, i see some logic i didnt consider before..


i will be researching.....