Comparison of cheap vs expensive solar

[T1 Terry]

Should the relevant posts be moved to Jim's new build thread? I guess this was Jim's thread in the first place so up to him really.
I received your email thanks Jim, no worries about doing the sizing etc for the battery pack and solar on the open, I just needed to know if you were looking for big energy use over night like running an air con via an inverter and batteries, or there would only be limited power use overnight, like a CPAP machine, electric blanket and the fridge with a fe hrs of TV thrown in .... big loads for the old lead acid, but really only small loads for lithium batteries. From there I can gauge how much solar you need to recover what you use over night plus power what you want during the day as well. You could reduce you power use during the day if the Victron BMV suggested you should conserve power a bit because the state of charge (SOC) wouldn't be enough to get through the night, just a matter of setting the low SOC alarm to let you know when you were reaching the over night requirement level. Even if the alarm setting was 50% for a 200Ah battery, you would still have 90Ah you can use before you would need to dip into the 10Ah held in reserve. Those figures double for a 400Ah system.
The solar needs to be enough to recharge the battery with a few good days of sun as well as supplying the daily power requirements. The old story about requiring 200w of solar per 100Ah of battery capacity only relates to the old lead acid batteries because they were so slow getting to back up near the 100% SOC that they require each day or so. Lithium batteries don't suffer that problem, the only real need to ever return to a 100% SOC is to auto-reset the Victron BMV so the reading were again accurate. All these things have small errors that creep into the calculations, the Victron BMV can be set the closest to accurate when it comes to lithium batteries, but to get really accurate there would need to be adjustments between the 99% and 100% discharge and recharge efficiencies and the system would need to be able to measure the power the system uses to keep itself running. Only milli amps for each part, but over weeks and mths they do add up, by 6 to 12 mths the accuracy gets way out of wack so the auto reset feature helps keep the errors to a minimum.
Lithium batteries do suffer if never returned to 100% capacity, but it takes about 3 yrs or so to become really noticeable, it is just a memory effect thing and can be cleared, so ever 3 to 4 yrs we recommend a battery pack service to keep it in as new trim. We have systems now in their 9th yr and still returning 100% capacity when tested at the rather savage load testing the manufacturer uses for their original capacity testing.

T1 Terry

[T1 Terry]

Thanks Bruce. So, who all is going from here? Do you know?

Jim

Maybe we should book in as an exhibitor and do a few talks Wouldn't that put the cat among the pigeons

[Grandad]

Do it! Please?

Jim

[T1 Terry]

Apparently a few exhibitors who planned to attend the Stone The Crows event in Wagga cancelled out when the discovered we would be giving talks and demos there. We didn't even have to buy an exhibitors site, we don't really sell or do sales pitches at these events, we just try to assist in sorting the wheat from the chaff for those that are interested by expanding their knowledge without their eyes rolling back in their head .... still working on that, we still seem to be going over their heads after the initial "G'day"

[Mrcoolabah1au]

A picture tells a thousand words

[SemiD]

Terry's presentation at Stone the Crows may have confused some but many of the people I spoke to understood the majority of what was being discussed They all want the benefits but balk at the price. Their loss
I will try to get some pictures of my " homemade" 5th wheeler with it new lithium system on the forum ASAP
Ian SemiD

[Mrcoolabah1au]

Yes ok thanks for that great message