5 ms·

By far… not so. Just, marginally, as of the last year, perhaps - but the total cost over the lifetime per Wh of storage is still on a par with lead, because lea

By far… not so. Just, marginally, as of the last year, perhaps - but the total cost over the lifetime per Wh of storage is still on a par with lead, because lead acid batteries are cheap as chips, require little or no maintenance if you’re sealed, and if you get something like OPzS cells and treat them well, you will get 20 years of life from them. LiFePo4, you’re looking at a decade, maximum, before they’re trash. I set us up here, totally off grid, three years ago, using a bank of OPzS cells, giving us 42kWh of usable storage. I rarely take them below 70%. Their performance has barely budged since installation, and with the condenser caps, they have required zero maintenance - I check the specific gravity of the acid once a year, and go “yup”, and that’s it. LiFePo4 I am considering for a booster bank at our cabin, which is 500m from our power shed, as the cable limits us to ~2.5kW here before we see significant voltage drop - it’s either that or step-up/step-down at either end, but transformers are surprisingly expensive. Main reason I’m leaning towards them for this application is mass, as our only access is either by foot or an aerial cableway - our lead bank weighs about 2000kg, equivalent LiFePo4 is about 450kg. So - LiFePo4 is a decent choice, but depending on your application, a pile of big lead acid cells can be better. See, for instance, storage at various solar projects - it’s virtually all OPzS cells, as the amortised cost is still favourable.

louwrentius 4y ago
> LiFePo4, you’re looking at a decade, maximum, before they’re trash. I think they will be at 80% after a decade, thus not trash. > if you’re sealed, and if you get something like OPzS cells and treat them well, you will get 20 years of life from them. If you have the space, 6V or even 2V OPzS cells can be huge.
- madaxe_again 4y ago
  Mine are 2v 660Ah cells - 24 of them take up about 3m^2 of floor, and they’re about 80kg each. Power density, they do not have.
  - louwrentius 4y ago
    Thank for sharing, almost 2 ton in weight. But I believe that can work.
K0balt 4y ago
Idk. For a ten year battery in a nightly discharge application you get 0.28 AH for each amp he purchased even with the OPzS cells. First you have to diéntate to .7 for a nightly discharge rate, then to reach 10 years of life span you have to de rate to 0.4 depth of discharge . So if for example, you need 1600 AH, you would spend $1500 for a 2000 AH lLiFe02 bank, plus 150 for a decent BMS, so $1800 US including shipping. (Just bought our 5th and 6th banks) For the OPzS, you would need to buy 5714 AH to get the same cycle life and longevity, plus you have to write off 38 percent of your charging energy due to voltage and discharge rate discrepancies vs about 10 percent for the LiFeO2. I seriously doubt you could obtain 5700 AH, shipped to your location, for less than $1800.. and then the size, maintenance, and corrosion issues (some of that goes away with the considerably more expensive sealed designs) also add to the headache. If the battery magazine will be subject to below freezing temperatures, both types incur additional risks and energy costs for the lithium, you must heat it prior to charging. For the lead, you will need to add another 40 to 50 percent capacity to meet your target power capacity.
myrmidon 4y ago
TIL. For non native speakers: "specific gravity" means "density, typically relative to max density liquid water", which does not make sense to me at all.
- zdragnar 4y ago
  It's a simple way to check changes in concentration of a chemical in water when you're not worried about external contaminants (i.e. just water vapor or anticipated chemical reactions). For home brewers, measuring specific gravity at the start and end of your brew process is the simplest way to know how much alcohol is in your creation. For this you'd use a hydrometer: https://en.wikipedia.org/wiki/Hydrometer https://en.wikipedia.org/wiki/Hydrometer
- jaclaz 4y ago
  It is a common way to measure battery charge through a hydrometer in automobiles batteries (not the sealed type): https://en.wikipedia.org/wiki/Hydrometer https://en.wikipedia.org/wiki/Hydrometer >Battery hydrometer The state of charge of a lead-acid battery can be estimated from the density of the sulfuric acid solution used as electrolyte. A hydrometer calibrated to read specific gravity relative to water at 60 °F (16 °C) is a standard tool for servicing automobile batteries. See also here: https://deepcyclebatterystore.com/use-battery-hydrometer/ https://deepcyclebatterystore.com/use-battery-hydrometer/
ilyt 4y ago
Isn't charging efficiency for lead acid lower tho ? Then again if you save on batteries might as well get that extra panel or two
- yencabulator 4y ago
  Yes, LiFePO charges much faster and in solar setups can "use more of the input" when it does shine. Lead-acid can compete there mostly by building a much bigger battery pack. I'd personally not want a lead-acid battery burping flammable gas inside an apartment. They're supposed to be installed in ventilated spaces with drainage holes for any acid that spills out.
  - madaxe_again 4y ago
    Or you have recombiner caps - haven’t had to top up at all, as they turn the escaping O/H back into water.

louwrentius 4y ago

> LiFePo4, you’re looking at a decade, maximum, before they’re trash. I think they will be at 80% after a decade, thus not trash. > if you’re sealed, and if you get something like OPzS cells and treat them well, you will get 20 years of life from them. If you have the space, 6V or even 2V OPzS cells can be huge.

madaxe_again 4y ago
Mine are 2v 660Ah cells - 24 of them take up about 3m^2 of floor, and they’re about 80kg each. Power density, they do not have.
- louwrentius 4y ago
  Thank for sharing, almost 2 ton in weight. But I believe that can work.

K0balt 4y ago

Idk. For a ten year battery in a nightly discharge application you get 0.28 AH for each amp he purchased even with the OPzS cells. First you have to diéntate to .7 for a nightly discharge rate, then to reach 10 years of life span you have to de rate to 0.4 depth of discharge . So if for example, you need 1600 AH, you would spend $1500 for a 2000 AH lLiFe02 bank, plus 150 for a decent BMS, so $1800 US including shipping. (Just bought our 5th and 6th banks) For the OPzS, you would need to buy 5714 AH to get the same cycle life and longevity, plus you have to write off 38 percent of your charging energy due to voltage and discharge rate discrepancies vs about 10 percent for the LiFeO2. I seriously doubt you could obtain 5700 AH, shipped to your location, for less than $1800.. and then the size, maintenance, and corrosion issues (some of that goes away with the considerably more expensive sealed designs) also add to the headache. If the battery magazine will be subject to below freezing temperatures, both types incur additional risks and energy costs for the lithium, you must heat it prior to charging. For the lead, you will need to add another 40 to 50 percent capacity to meet your target power capacity.

myrmidon 4y ago

TIL. For non native speakers: "specific gravity" means "density, typically relative to max density liquid water", which does not make sense to me at all.

zdragnar 4y ago
It's a simple way to check changes in concentration of a chemical in water when you're not worried about external contaminants (i.e. just water vapor or anticipated chemical reactions). For home brewers, measuring specific gravity at the start and end of your brew process is the simplest way to know how much alcohol is in your creation. For this you'd use a hydrometer: https://en.wikipedia.org/wiki/Hydrometer https://en.wikipedia.org/wiki/Hydrometer
jaclaz 4y ago
It is a common way to measure battery charge through a hydrometer in automobiles batteries (not the sealed type): https://en.wikipedia.org/wiki/Hydrometer https://en.wikipedia.org/wiki/Hydrometer >Battery hydrometer The state of charge of a lead-acid battery can be estimated from the density of the sulfuric acid solution used as electrolyte. A hydrometer calibrated to read specific gravity relative to water at 60 °F (16 °C) is a standard tool for servicing automobile batteries. See also here: https://deepcyclebatterystore.com/use-battery-hydrometer/ https://deepcyclebatterystore.com/use-battery-hydrometer/

ilyt 4y ago

Isn't charging efficiency for lead acid lower tho ? Then again if you save on batteries might as well get that extra panel or two

yencabulator 4y ago
Yes, LiFePO charges much faster and in solar setups can "use more of the input" when it does shine. Lead-acid can compete there mostly by building a much bigger battery pack. I'd personally not want a lead-acid battery burping flammable gas inside an apartment. They're supposed to be installed in ventilated spaces with drainage holes for any acid that spills out.
- madaxe_again 4y ago
  Or you have recombiner caps - haven’t had to top up at all, as they turn the escaping O/H back into water.