diy solar

diy solar

Do I have the numbers correct?

withaview2

New Member
Joined
Aug 8, 2022
Messages
23
Hi! Solar newbie here.

In the early stages in planning and have only the batteries so far. The load (minimum in bold) will be about: 8 indoor and 4 outdoor LED lights. Fridge and freezer. Kitchen appliances. TV and DVD. Battery charging station. Wierless network. Garden water pump. Running electric tools. Fan. Heating cable. Microwave.

EVE 8x280Ah (Lifepo4) cells + 8S 150A JBD BMS.
(24V)
Nominal Voltage 3.2V
Max discharge Current 1C/280A
Max charge Voltage 3.65V

The array will likely be two panels in series with 750W max output.

Longi LR4-60HPH-375M
Nominal capacity 375 Wp
Imp 10.84 A
Vmp 34.6 V
Isc 11.6 A
Voc 41.1V
Temperature rating STC:
Isc +0.048%/C
Voc -0.270%/C
Pmax -0.35%/C
Calculated temperature min -20 Celcius.

The SCC I'm considering is.

MPPsolar (2424MSE1).
(24V)
2.4kv Inverter
105V max PV input.
25A max utility charging.

Do have the numbers on my side or do I need to rethink something, hopefully not everything?
 
Last edited:
I do not see any loads numbers. You mention several without giving watts, amps or measured daily watt-hr
 
I do not see any loads numbers. You mention several without giving watts, amps or measured daily watt-hr
It's because I haven't purchased all I need yet. Apart from a few kitchen appliances it's mostly low wattage output. Will be using two chest freezers, one as a refrigerator with thermostat to keep the draw to a minimum.

You don't think 2.4kw will be enough for the basic load?

I would greatly appreciate if someone could tell me if this battery/PV/SCC setup will work, and if the SCC is suitable to charge these cells?
 
Last edited:
Oh I am sure that your components will do close to what they are rated to do. (Exception is the solar panels you frequently have to expect around only 75% of rating or less based on location and other factors).

Just understand that you get no power out without a load. Batteries will become a load when they need to be charged. Until than they just sit there other than normal rates of self discharge based on battery chemistry.

Take your homes utility supply. If it is USA standard it likely is 240vAC with a 200amp main service breaker. That means it could supply 48Kw every hour of the day if you needed that much. However it supplies nothing if you don't.
 
Oh I am sure that your components will do close to what they are rated to do. (Exception is the solar panels you frequently have to expect around only 75% of rating or less based on location and other factors).
So, just to be sure.

1) The 2x375W panels (in series) total output will not exceed max PV input of the SCC?

2) The battery bank charging voltage within inverter bulk/float//low DC cut-off voltage acceptable range?

Just understand that you get no power out without a load. Batteries will become a load when they need to be charged. Until than they just sit there other than normal rates of self discharge based on battery chemistry.

I'm not sure I understand. Will battery charging become load on the inverter?

Take your homes utility supply. If it is USA standard it likely is 240vAC with a 200amp main service breaker. That means it could supply 48Kw every hour of the day if you needed that much. However it supplies nothing if you don't.
I will be off-grid.
 
Appliances listed pretty much match what I'm already running in my own cabin, so without further clarification from you, based on what I'd see I'd say you need ≥4kWh per day. Call that 5-6kWh with power tools, and maybe 8+kWh if you add a small air-conditioner. That's summer. Maybe 3-4kWh in December.

So, based on that I'd say 750W is not enough. Assuming you get 5sunhours in June, maybe 1000W minimum, though I'd go with 1500W as your starter goal. Now 1500W with a 24V system would max out at about 60A, which is in the range of most good quality charge controllers.
 
Based on specifications here: https://www.mppsolar.com/v3/catalogs/PIP-HSE1_MSE1.pdf You have 40 amps and up to 105Voc that you can work with. Your two panels are rated at
Imp 10.84 A
Vmp 34.6 V
Isc 11.6 A
Voc 41.1V

So in series you have 82.2Voc (thus below the 105Voc max of the MPP) at ISC of 11.6 amps. The MPP is rated at 40 amps max charging. (40a*25vDC =1000w)

Charging the batteries will depend on the MPP settings for charging and how much the solar panels can deliver.

Battery charging does become a load on the SCC/inverter setup. However it is not necessarily from the inverter part of it. It depends on the MPP unit how it handles delivering battery charge current.

Being Off grid it becomes even more impotant to understand that loads drives your supply needs.
 
Appliances listed pretty much match what I'm already running in my own cabin, so without further clarification from you, based on what I'd see I'd say you need ≥4kWh per day. Call that 5-6kWh with power tools, and maybe 8+kWh if you add a small air-conditioner. That's summer. Maybe 3-4kWh in December.

So, based on that I'd say 750W is not enough. Assuming you get 5sunhours in June, maybe 1000W minimum, though I'd go with 1500W as your starter goal. Now 1500W with a 24V system would max out at about 60A, which is in the range of most good quality charge controllers.
Ah ok. To be clear. The appliances listed (except fridge, freezer, wireless network, some lights in the evening and phone charging) will only be used when possible and necessary. Future plans is getting a geny for support charging when needed. I do get alot of sun in the summer, more like 6-7 hours. Even more some days, others less.

From what I've learned (watching YouTube videos till my eyes bleed) lots of people use even less PV input with pretty much the same appliances. I was even thinking 750W was more than I needed :oops:
 
Last edited:
In the solar panel forum section I did Benchmark tests of 2-100 watt solar panels (Newpowa). It might be of interest to you to read. https://diysolarforum.com/threads/benchmark-2-newpowa-100w-12vdc-rv-solar-panels.44602/

Also I am presently running a off grid AIO hybrid system I just put in with 6-100watts supply. It has AC power along with solar. I do not consider it adequate to power the loads I have placed on it without grid AC adding to the supply mix.

Loads are;
1 - 12cuft upright freezer 70watt running 1.3kwh/day
1 desktop computer and LTE router setup for internet access. Aprox 50watt running
The AIO unit itself (it takes power to make power). Uses between 50w and over 100w running, estimate 1.5kwh/day
Various minor loads depending on need such as phone charger, alarm clock, some LED lights.
 
Last edited:
Ah ok. To be clear. The appliances listed (except fridge, freezer, wireless network, some lights in the evening and phone charging) will only be used when possible and necessary. Future plans is getting a geny for support charging when needed. I do get alot of sun in the summer, more like 6-7 hours. Even more some days, others less.

From what I've learned (watching YouTube videos till my eyes bleed) lots of people use even less PV input with pretty much the same appliances. I was even thinking 750W was more than I needed :oops:
Why are you resistant to the idea of more solar? Solar panels can be dirt cheap right now, 250-260$/kW. I'd really advise you to go with the maximal power level your system can handle. Switching stuff off to thaw at night is a poor scheme for conservation.

Supplementing power with the generator is a hallmark of inadequate, make do design. In today's solar environment we should all be past that. With my own system, I haven't had to run the generator for more than two years.
 
In the solar panel forum section I did Benchmark tests of 2-100 watt solar panels (Newpowa). It might be of interest to you to read. https://diysolarforum.com/threads/benchmark-2-newpowa-100w-12vdc-rv-solar-panels.44602/

Also I am presently running a off grid AIO hybrid system I just put in with 6-100watts supply. It has AC power along with solar. I do not consider it adequate to power the loads I have placed on it without grid AC adding to the supply mix.

Loads are;
1 - 12cuft upright freezer 70watt running 1.3kwh/day
1 desktop computer and LTE router setup for internet access. Aprox 50watt running
The AIO unit itself (it takes power to make power). Uses between 50w and over 100w running, estimate 1.5kwh/day
Various minor loads depending on need such as phone charger, alarm clock, some LED lights.
Thanks.

100W just for the AIO feels like wasting energy. What model do you have if may ask? Regular inverters draw less?


Why are you resistant to the idea of more solar? Solar panels can be dirt cheap right now, 250-260$/kW. I'd really advise you to go with the maximal power level your system can handle. Switching stuff off to thaw at night is a poor scheme for conservation.

Supplementing power with the generator is a hallmark of inadequate, make do design. In today's solar environment we should all be past that. With my own system, I haven't had to run the generator for more than two years.
Trying to keep the cost down. Even though the panels are relatively cheap, more PV:s will also raise cost of the rest.

I see what you're saying, it makes sense. I'm considering one more 375W which means I will need at least a 60A SCC. As a noob I like the simplicity of the AIO:s. MPP Solar seems to have a good reputation. Any other recommendations?
 
Trying to keep the cost down. Even though the panels are relatively cheap, more PV:s will also raise cost of the rest.

Any other recommendations?
Switch over to quality Trojan L-16 batteries which are only about 400$ right now. The thousands of dollars you save can be plowed into more solar. Since traditional batteries benefit more from overpanelling, it's a win/win situation. ~1500W is perfect for a 24V string of L-16s.
 
Thanks.

100W just for the AIO feels like wasting energy. What model do you have if may ask? Regular inverters draw less?
All inverters will use power in the conversion from low DC voltages to Higher AC voltages. Some inverter models have Power saving mode that will draw much less wattage when idle (My EAsun has this). However in power saving mode small loads might not cause the inverter to cycle up and large starting loads can force it into O/L.

No inverter is 1 to 1.

BTW. There are losses in every stage of the solar setup from panels to delivered to appliance wattage. Batteries take more power to charge than you get back out of them. Lead acid batteries self discharge with time. IIRC 3% per month.

Part of your numbers to size your system is to account for normal loss.
 
Last edited:
Switch over to quality Trojan L-16 batteries which are only about 400$ right now. The thousands of dollars you save can be plowed into more solar. Since traditional batteries benefit more from overpanelling, it's a win/win situation. ~1500W is perfect for a 24V string of L-16s.
Sure, but batteries already purchased and they where not too expensive actually. Thanks for the tip though (y)
All inverters will use power in the conversion from low DC voltages to Higher AC voltages. Some inverter models have Power saving mode that will draw much less wattage when idle (My EAsun has this). However in power saving mode small loads might not cause the inverter to cycle up and large starting loads can force it into O/L.

No inverter is 1 to 1.

BTW. There are losses in every stage of the solar setup from panels to delivered to appliance wattage. Batteries take more power to charge than you get back out of them. Lead acid batteries self discharge with time. IIRC 3% per month.

Part of your numbers to size your system is to account for normal loss.
Power saving sounds like a good option to have. Will have to look up EAsun.

So essentially, both AIO inverters and regular inverters (without the power saving mode) generally draw about the same wattage?

Question. Let's say I want to only run freezer and fridge over night. Is it possible to shut of the AIO/inverter in some way and still power them from batteries, with a second dedicated inverter perhaps?
 
Based on my research there are a few AIO's that have low internal draw. Generally speaking the ones with low self consumption are at the top of the price brackets. Inverters are much the same. There is a Thread on the Forum on low idle draw inverters.

It seems for lower cost off grid use, and more simple power needs, there is a lot of virtually identical Chinese made units. They go by a variety of names. However there is one that seems to be getting better reviews than the others. This is Growatt. I have never owned one so I am just going from what I read.
 
Sorry for late reply.

Took me awhile getting hold of another PV as these specific Longi 375W seems to be out of production.

Growatt is unfortunately to pricy for me.

I'm looking at either MPPsolar 3024GK or EPever UP-HI 3KW. From Alibaba the price is about the same.

The EPever has a BMS-link option. Will that work fully as a BMS or only as a complement to a separate BMS?
 
Ok, so if I understand this correctly the BMS link is just for monitoring the battery BMS and not a necessity for connecting to batteries?

If so, could someone please confirm if the UPower (see below) will work without the BMS link, and together with the external BMS connected to my batterybank?

Or is this unit perhaps overkill for my 1125W/154.1V set up?

Thank you!

UPower Hi series UP3000-HM10022
24V
Pure Sine Wave
3000W Continuos (6000W Surge)
80A Max utility charge current
100A MPPT (range 80-350V)
500V Max PV open circuit range
4000W Max PV input power
 
Last edited:
Anyone?

I'm about to make an order of the HM10022 but want to make sure if the BMS-link is necessary or not.

This is what I read about BMS link on another site:

"This unit is required using managed lithium batteries, like pylontech US2000 and US3000, and the EPever Lithium compatible inverters"

I guess the EPever HM10022 would be considered and therefore BMS link necessary for the unit to work with my batterybank?
 
Back
Top