Battery voltage discharge level.

[john61ct]

14.7-8V is probably where you should be for everyday charging, a bit higher if your sources have **good** temperature compensation.

And reading directly from the battery terminals with a **known accurate** DMM.

[a64pilot]

Originally Posted by conachair

Not that interested so long as they are actually getting fully charged often, but was hoping that comparing the smart gauge SOC with amps out would be a helpful indication of capacity - looks like it isn't going to tell much without some calibration against temperature & some kind soul to spend weeks with lab equipment checking if it actually tells you anything useful.

No, you can use amps out and what the SG gives as a SOC.
I do anyhow and it seems to work, just don’t discharge only 10% and think you can extrapolate that into capacity, because you may not can. But discharge deeper and it does seem to become more accurate.
But even a capacity check properly done often has to be done at ambient temp, not all have a water tank that is temp controlled.

Pretty much what people are comfortable with temp wise is close enough for a battery.

[john61ct]

I stand by
>> Equalizing is a once-off procedure that should be run manually, and precisely as per the batt mfg's spec'd protocol. Ideally from shore power.

Have never heard of more frequently than one session done and dusted, once a week.

Ideally each unit is equalized on its own, independently of the bank.

As you say, start at 100% Full, as defined above

Then, increasing the volts to the Equalize setpoint will result in a higher acceptance rate, but not by much, and it will also decline pretty quickly.

So, **if** you are truly getting to 100% Full before you start, even a puny say 20A source might be enough for equalising.

Again, ideally off shore power, and also with a user-custom voltage adjustable setpoint.

______
My understanding of the Trojan protocol is equalization requires (for 12V nominal) 16.2VDC @ 77°F , of course adjusting for temperature compensation.

Dig through this for some more in depth

http://www.cruisersforum.com/forums/...on-201841.html

Again, use a known good DMM and ammeter*so you know you're complying with the protocol.

> 4th of 4 batteries had a bad cell

That could have caused damage over time to the remaining units, only a load test will tell for sure

[Jeremy-KHYC]

Originally Posted by conachair

Done it Well, not quite. Voltage, current & temperature are pretty easy with a few dollars on sensors & a raspberry pi. SG & electrolyte level bit more complicated. Plotting data is fascinating, you'll see trends hidden in the noise that you'd never pick up just looking at the numbers.

Nice, i'm interested, have you documented what you did so that others can reproduce it?

[tony.keel]

This might interest somebody so I offer this information. Many of you will have more complete explanations I am sure The battery is made of cells - it is a battery of cells. The cell voltage is determined by the galvanic numbers of the metals in the plates - You can think of that number never changing. What changes is the internal resistance of the cells. Think of your battery as two objects inside the case: a perfect battery that will produce its fixed galvanic voltage for the entire discharge cycle, and an internal resistor that is dropping voltage in proportion to the current flow at that moment. The resistor gets bigger in value as the battery discharges so it drops more voltage. The other thing that reduces the voltage measured at the terminals is the amount of current the battery is delivering at that moment. Double the current and you double the voltage drop. V=IR. Ohms Law. V is voltage in volts, I is current in amps and R is resistance in ohms. This is not a perfect explanation but it helped me understand why battery voltage doesn't tell you a lot especially when the battery is not delivering current.
Read about how sophisticated battery chargers work. They are in effect measuring the internal resistance of the battery as an indicator or state of charge. They monitor the voltage and current simultaneously and adjust current input according to the known battery chemistry (galvanic numbers and characteristic internal resistance at any state of charge). Good ones measure temperature as well because that has an effect on the battery voltage. Hope that helps someone.

[john61ct]

Originally Posted by tony.keel

sophisticated battery chargers

AFAIK no chargers costing less than thousands do this, please link to any that you know of

> measuring the internal resistance of the battery as an indicator or state of charge

> galvanic numbers and characteristic internal resistance at any state of charge

When the user selects a battery chemistry, that just locks in a certain Absorb/CV voltage which may or may not match mfg specs for **your* batteries. Good chargers allow user-custom setpoints beyond those few canned options.

The stop-charge algorithm is most often time-based rather than using endAmps the canonical measure of 100% SoC.

Most even crazy expensive chargers drop from Absorb to Float too early, needing the owner to calibrate depending on factors like season, concurrent loads, usage patterns,

> Good ones measure temperature as well because that has an effect on the battery voltage.

That is true, aka temp compensation.