My Solar Journey

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denmendez65

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Hi Everyone,

I thought I would make a little write up on my solar journey for those interested.

Despite the reduction in load shedding, the area where I stay is plagued with power cuts due to faults etc. So I decided it was time to do Solar but after getting married, purchasing a house and car all in a 8 month space the budget wasn't there. So I decided to research a lot on how best to do a budget solar home without stretching credit cards etc. Watching lots of YT videos on budget systems helped with the decision making. There were plenty of people in the US/Canada living off-grid with Lead acid based batteries. One guy had a system running for 9 years with the same battery bank. The key was being energy efficient and reducing your DOD use from them. They were all using about 10 to 20% capacity from their large and very cheap battery banks.

I then went with a GEL battery-based solar system, I will get lots of heat for this but hear me out. I started with 4 GEL batteries (2 parallel strings, each with 2x12V series connections). Each battery cost me 1.2k (12V 100ah GEL VRLA) so I got them very cheap after lots of online research. The inverter is a MUST 3.6kw MPPT one and I started off with 2x650W Fivestar solar panels. The system helped decently well to cover the power cuts which were bad but I wanted a bit more out of the system, I wanted to start cutting the electric bill.

So with the use of Payflex (interest-free payments over 3 months) I started expanding the battery bank. GEL batteries do not like being discharged below 50%. So my theory was (based on DOD and cycle life curves), get more capacity so that when you drain them, you drain no more than 30%. I got to 10 batteries with a total capacity of 12.8kwh. I then started expanding the solar panel array, I eventually wound up at 6x650W panels for a total of 3.9kwp. The next goal was to create a more energy saving house, I replaced all the lights outside with solar ones (this was very cheap to do) and used timers to shift the running of the fish pond to during the day only and the pool to peak sun hours.

I did all the right stuff for the batteries, I have battery balancers installed, fuses etc. Heaters where replaced with Gas ones, the house already had a Gas stove so no work was needed there. I then decided to make the whole house excluding the geyser run from the inverter only. And to my surprise the system was well balanced, I have not connected to eskom for the last 2.5 months. Winter affected the solar production obviously but the house is so efficient that i still have plenty of solar available to charge the battery, run the pumps for the fish pond and the pool pump. I only use 20% of the battery capacity throughout the whole night (despite us having a 65 inch TV and myself on my computer at night). With this consumption the batteries will easily last over 5 years of daily cycling (currently 6 months in and there has been no loss in capacity). For interest, at 20% DOD you get about 2200 cycles on most GEL brands, So with a conservative 1800 cycles i'm still at 5 years lifespan.

It took me close to 6 months to get everything done and while I would recommend someone starting out do Lithium, starting small and building up also works. It was less daunting with the initial capital requirements for the fancy stuff with the financial situation I was in. I got to take care of the power cuts in less than 2 months also. My future goal is to eventually wave goodbye to Eskom. I will get a second inverter and a large lithium battery bank for when the time is right to go off grid, I will run that together with the current system. Our finances have settled so it won't be very long in the future. The increases etc have just become unbearable for the average person.
 
I started small in 2017 with a 5kW off-grid inverter, 100Ah 48v battery and 8 425w panels.
Cost: R150,000
This was enough to get through loadshedding but had little benefit in saving money.

I upgraded to a 8kW hybrid, replaced the battery with 2 200Ah 48v batteries and added 10 more 580w panels. I added up the pool pump, pool heatpump and geyser (changed to a 2kW from a 4kW element) to the system.
Cost: R140,000
I got R9000 for the old 5kW inverter and battery.

It's a money pit, IMO. But my savings on Solarman looks lekker now because I am able to store more excess solar energy, and run the system in self-consume mode. I have it set to run to 0% and am able to refill to 100% daily, unless it's overcast.
 
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What was the cost of those 10 gel batteries?
Plus you only really have 6kw out of those batteries not 12, as you don't want to go past 50% and if you're only going down 20% does the cost really balance out against 2 lithium batteries?
 
Lupus said:
What was the cost of those 10 gel batteries?
Plus you only really have 6kw out of those batteries not 12, as you don't want to go past 50% and if you're only going down 20% does the cost really balance out against 2 lithium batteries?
Click to expand...
12k in total. The issue was the cheapest 24V lithium battery I could find was 7.5k for a 2.56kwh battery. I was buying 2 batteries every month for 2.4k. My finances where very tight and could not afford the upfront cost for the lithium battery and couldnt stand having to spend a whole weekend with no power so I spent 10k initially (3.5k for the inverter, 3.5k for the Panels and 2.4) to get started. The cabling wasnt too bad as it was a short route from the panels to the house and from the inverter to the DB board. I got another 2 almost immediately after as SARS credited me some 3k. I could have gone lithium if I waited another 2 months but the alternative was viable so I went with it. As mentioned I never use over 3kwh when the sun goes down so I made the system work for me. And even if I can only use 6.4kwh, the cheapest 5kwh 24V battery is 15k. But again, as I said, I would not recommend anyone get GEL if they have the money for lithium.
 
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Lupus said:
What was the cost of those 10 gel batteries?
Plus you only really have 6kw out of those batteries not 12, as you don't want to go past 50% and if you're only going down 20% does the cost really balance out against 2 lithium batteries?
Click to expand...
One 5kW LFP (remember LA Peukert Effect) will do the same job and last 20 years.
 
denmendez65 said:
12k in total. The issue was the cheapest 24V lithium battery I could find was 7.5k for a 2.56kwh battery. I was buying 2 batteries every month for 2.4k. My finances where very tight and could not afford the upfront cost for the lithium battery and couldnt stand having to spend a whole weekend with no power so I spent 10k initially (3.5k for the inverter, 3.5k for the Panels and 2.4) to get started. The cabling wasnt too bad as it was a short route from the panels to the house and from the inverter to the DB board. I got another 2 almost immediately after as SARS credited me some 3k. I could have gone lithium if I waited another 2 months but the alternative was viable so I went with it. As mentioned I never use over 3kwh when the sun goes down so I made the system work for me. And even if I can only use 6.4kwh, the cheapest 5kwh 24V battery is 15k. But again, as I said, I would not recommend anyone get GEL if they have the money for lithium.
Click to expand...
Not sure how you only use 3 units for 14 hours. Are you actively monitoring everything to ensure your usage?
If you're only using so little at night your base load must be next to 0. Plus the inverter does take about 50w
 
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For interest, I spent 35k in total for the entire system with cabling, accessories etc.
 
wingnut771 said:
One 5kW LFP will do the same job and last 20 years.
Click to expand...
Yup it would've, that's the thing about gel you may get 5 years out of it, but you're going to replace it 3 times at least before you'd even look at replacing the lithium
 
Lupus said:
Not sure how you only use 3 units for 14 hours. Are you actively monitoring everything to ensure your usage?
If you're only using so little at night your base load must be next to 0. Plus the inverter does take about 50w
Click to expand...
Base load is 70W when everyone is sleeping. The fridge occasionally kicks in here and there but it barely uses anything. With TV on its about 230W. With my computer on about 350W. So its about 0.4kwh between 5pm and 10pm. We typically sleep by then. Washing machine and dishwasher are scheduled to run during the day. I have 2 Tuya energy monitors checking everyting (havent bought the dongle for inverter yet) and when I check the battery voltage it is sitting at 25.0V and under load so if we assume resting voltage is 25.1, the batteries are discharged to about 85%. I say 80 for worst case scenario. Which ties in with my Tuya energy monitors.
 
Lupus said:
What was the cost of those 10 gel batteries?
Plus you only really have 6kw out of those batteries not 12, as you don't want to go past 50% and if you're only going down 20% does the cost really balance out against 2 lithium batteries?
Click to expand...
Agree, even using his use case scenario and figures, at best lithium breaks even.

This is based on quick googling:
IMG_20250626_153700_954.jpg

Assumptions both lithium and lead gives 1.28kwh.

Only 30% of Lead Acids are used: 30%×12.8kwh= 3.84kwh


For the lithiums, you can safely discharge 80% x 5.12kwh = 4.096kwh

I just took the 1st price for a 100ah 12v lithium battery.
 
rh1 said:
Agree, even using his use case scenario and figures, at best lithium breaks even.

This is based on quick googling:
View attachment 1830704

Assumptions both lithium and lead gives 1.28kwh.

Only 30% of Lead Acids are used: 30%×12.8kwh= 3.84kwh


For the lithiums, you can safely discharge 80% x 5.12kwh = 4.096kwh

I just took the 1st price for a 100ah 12v lithium battery.
Click to expand...
Its a 24V system so would need to be a 24V 100ah battery.
 
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rh1 said:
Agree, even using his use case scenario and figures, at best lithium breaks even.

This is based on quick googling:
View attachment 1830704

Assumptions both lithium and lead gives 1.28kwh.

Only 30% of Lead Acids are used: 30%×12.8kwh= 3.84kwh


For the lithiums, you can safely discharge 80% x 5.12kwh = 4.096kwh

I just took the 1st price for a 100ah 12v lithium battery.
Click to expand...
You forgetting peukert effect. LA has to discharge at C10 (10 hours) or C20 (20 hours) to get its rated capacity. LFP doesn't have this issue. Try discharge a LA battery in 1 hour and you probably only get maybe 60%.
1750945835077.png
 
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My previous job, my colleague went with lead acids as it was cheaper and I went lithium thanks to the advice on these forums. My colleague only looked at the initial savings. Just after year later after the multiple load shedding slots per day. Her batteries were dead.
 
wingnut771 said:
As each gel battery fails, replace it with an LFP.
Click to expand...
Yep thats the plan. In 5 years when I expect them to start packing up I will replace the entire bank with lithium. I will save some 2k a month for the solar expansion I will do going forward. The 24V inverter will run from a 10kwh bank probably and Ill add a 48V one to run any high power items I may need. Probably a 15kwh bank.
 
wingnut771 said:
As each gel battery fails, replace it with an LFP.
Click to expand...
Can't do that, he would need to gradually watch the capacity diminish and than replace the whole array.
Or just replace it as soon as possible with lfp, I've had gel it's possibly the worst battery for this scenario. Doesn't handle high draw very well, one or two dips below 24v and the batteries will be kaputski.
 
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wingnut771 said:
You forgetting peukert effect. LA has to discharge at C10 (10 hours) or C20 (20 hours) to get its rated capacity. LFP doesn't have this issue. Try discharge a LA battery in 1 hour and you probably only get maybe 60%.
View attachment 1830712
Click to expand...
Plus they require a long time to charge and they love being fully charged. Unlike lfp
 
denmendez65 said:
Yep thats the plan. In 5 years when I expect them to start packing up I will replace the entire bank with lithium. I will save some 2k a month for the solar expansion I will do going forward. The 24V inverter will run from a 10kwh bank probably and Ill add a 48V one to run any high power items I may need. Probably a 15kwh bank.
Click to expand...
No man, live on the wild side, just replace with 12V LFP one at a time, so you'll have one GEL and one LFP in a string.
 
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