Is solar battery storage worth it?

MSE_Clare

Hi everyone

We've just published a new guide on solar batteries and we'd love to hear your feedback.

If you haven’t already, join the forum to reply.

Thanks for your help,

MSE Clare

nologo

My understanding is batteries are no longer recommended to be installed in the roof space as if there is a fire they can come through the ceiling and may injure a householder or fire fighter 

Netexporter

nologo said:

My understanding is batteries are no longer recommended to be installed in the roof space as if there is a fire they can come through the ceiling and may injure a householder or fire fighter 

Yes, I noticed that egregious error, so didn't bother to read the rest of it.

Reed_Richards

Fully charging a storage battery will damage it in the long-term and will make it inefficient to use.

I hope that this is not true because I have been charging my battery to 100% (given enough solar power) for the 5+ years since I got it.  What you can't do is discharge your battery to less than 15% to 10% (the recommended minimum seems to depend on the battery).  Hopefully the article got this topsy turvy.  

Ectophile

The document that previous posters are hinting at is PAS 63100:2024.  Available for free download https://www.bsigroup.com/en-GB/insights-and-media/insights/brochures/pas-63100-protection-against-fire-of-battery-energy-storage-systems/

Of course, my battery is in the loft, because that's where the installers always put them.

pete-20-11

Not sure noisy is relevant any more, most inverters and batteries are pretty quiet aren't they? Or do some still have fans rather than heatsinks?

Also some people might choose to get an AC battery system at the same time as solar panels - possibly for better live monitoring or possibly for better features (like whole home backup on the GivEnergy AIO for example).

EcoScruples

Some good points picked up there, 
1. You definately can charge to 100% and most operating instructions will confirm this, leaving discharged fully for long periods is of concern but most batteries have software that manages this for you.
2. Charging your EV for free? This isn't the case as that electric can be sold back to the grid so it's never going to be free but will be clean with a lower carbon footprint.
3. Loft installation as a last resort for fire safety, backed up by advise from the fire service.

A lot of other really good stuff in there like the figures and calls, would be nice to have evidence of the 5 to 15 year lifespan to back that up. 

Magnitio

Reed_Richards said:

Fully charging a storage battery will damage it in the long-term and will make it inefficient to use.

I hope that this is not true because I have been charging my battery to 100% (given enough solar power) for the 5+ years since I got it.  What you can't do is discharge your battery to less than 15% to 10% (the recommended minimum seems to depend on the battery).  Hopefully the article got this topsy turvy.  

For LFP batteries (which is most of them) you need to charge regularly to 100% so that the BMS knows the state of charge. Why do "guides" like this get published without being checked first?

Newbie_John

It would be worth to add what happens to the battery after 15 years? How much does it cost to get rid of it? If I was buying a house that had old not working battery in the attic I would look for a price reduction, so keeping it there forever is not an option really.

On the other hand if you have a lot of spare time you could make more money by playing with it and charging it while on ToU tariff.. but that again involves a lot of time and gains are tiny - compared to minimum wage fpr example 😃

ed110220

Definitely worth it I think. One thing that's often forgotten about is that it's not just useful for once the sun sets - if you're running a higher power device like a washing machine even on a mostly sunny day, it will often draw more than the PV is producing at that moment. If you have batts it will draw the difference from them rather than the grid. So even relatively small batts are useful for this. 

Something I didn't give enough thought to was the charging/discharging limit of the inverter. Ours is a 5 kW model (SPH5000) but it will only charge/discharge up to 3 kW so I have to be a bit careful not to run too many things at once if I want to make the most use of the batts and avoid import.

pete-20-11

Magnitio said:

Reed_Richards said:

Fully charging a storage battery will damage it in the long-term and will make it inefficient to use.

I hope that this is not true because I have been charging my battery to 100% (given enough solar power) for the 5+ years since I got it.  What you can't do is discharge your battery to less than 15% to 10% (the recommended minimum seems to depend on the battery).  Hopefully the article got this topsy turvy.  

For LFP batteries (which is most of them) you need to charge regularly to 100% so that the BMS knows the state of charge. Why do "guides" like this get published without being checked first?

The LFP battery I have (GivEnergy) is charged to a 100% user capacity regularly.

There's a buffer beyond that, so 100% isn't really 100%, and it's not recommended to get to top high a voltage (full) or too low a voltage (empty) very often. Occasional calibrations maybe, but not regular.