Which is it? Wet LA battery 50%, 12.06v or 12.3v?

[82125]

Seems to be quite a variation as to what the acceptable voltage is for roughly 50% capacity, in this case for wet lead acids (sealed Numax 105ah LV30MF x 2)?

Most of the info ive just read says 12.3v is 50% but then theres quite a few stating 12.06v? Thats quite a difference when it comes to off-grid living and knowing its now time to switch things off until the solar has a chance to recharge them again the next day.

I'm generally finding that by about the 4th day off-grid I'm in the 12.2v - 12v territory (while still drawing a load), I realise that without fully disconnecting them I cant ever get an accurate SOC, but I'm trying to understand at what point (whilst still drawing power) I need to say that's it for today and switch off.

For instance, its day 4 off-grid so the only charge my batteries have received has been from the 500w solar panel. Whilst listening to the radio, re-encoding & rendering videos (which sucks a lot of power) and any other draws from the van, the voltage was down to 12.0v on my controller and external voltage display.
Switching off the inverter (that was charging the laptop whilst rendering and a few other devices on charge) and the radio and the battery voltage has quickly settled back at 12.2v, which seems "o.k".
Its yet another very cloudy day, nearly 3pm, so the solar is only putting 0.2A in (but was giving almost 10A for a while earlier on).

Q.1 Would it be reasonable to assume I can draw power until I see 12.0v displayed and set that as my limit for the day (as the resting voltage seems to be about 0.2v higher)? Or is 50% capacity actually 12.06v in which case i can continue using them down to about 11.8v?

Q.2 Given that at this time of year I'm clearly not fully recharging my batteries (until theres a nice clear sunny day or I plug in to EHU). Is this cycle (when its repeatedly cloudy) of only partly recharging my batteries over a number of days causing sulphating which will ultimately kill my batteries?

Thanks.

 

[IRHP]

There are a lot of charts available online most suggest 12.05-12.06 is 50%

 

[cmcardle75]

Get a battery monitor like a Victron Smartshunt or BMV. That will remove guesswork. Trying to determine SOC from voltage when still in use is very hit or miss.

If I was in your position, I'd use down to about 9.5V. Then, when the batteries get inevitably trashed, I have an excuse to buy some Lithium batteries!

 

[Lenny HB]

SOC by voltage is only an estimate and you need to leave the batteries to settle for 30 to 60 min without a load for the most accurate result.
The only real way of knowing is by counting the amps in & out from a fully charged state with a good battery monitor. Even then to get a battery monitor set up to give accurate percentage reading is quite an art also you have to allow for the age of the batteries when setting it up (approx 2.5% loss of capacity per year).

If working on voltage I would work with 12.2v as 50%.

 

[82125]

deleted

^{_{Subscribers  do not see these advertisements}}

 

[82125]

Get a battery monitor like a Victron Smartshunt or BMV. That will remove guesswork. Trying to determine SOC from voltage when still in use is very hit or miss.

If I was in your position, I'd use down to about 9.5V. Then, when the batteries get inevitably trashed, I have an excuse to buy some Lithium batteries!

lol! I actually had the two cheap Numax lead-acids put in on the basis that if they die then fine, but it gives me time to figure out what i want to do next, and understand my day to day power requirements and charging ability. I wasnt comfortable relying on the 5 year old batteries my MH came with.
I really am just trying to establish what is considered 50% capacity voltage, even if its a guesstimate, at least its a starting point I could work up from to avoid cycling the batteries unnecessarily.