NextStep2 regulator bulk charge issue

[jackt]

Originally Posted by mitiempo

Allowing the voltage get high enough to send 320A into a small battery is hardly the issue. Wouldn't happen unless the charger was totally unregulated.

The regulator does not "regulate the voltage difference between the battery and the charging source". It has a set absorption voltage. The battery takes the current it can until that voltage is reached. It stays at that voltage for a period of time, set too short on most chargers as previously stated by Mainesail. 3 to 4 hours is much better than 1 hour. The charger then goes into float voltage at about 13.4 to 13.6 volts with the last few percent of charge going in slowly. This assumes a 3 stage charger. An alternator that has internal regulation is considered to have "dumb" regulation and has a single voltage setting, typically 14.4 when cold. As the alt heats up this voltage will drop.

A charger can be too small but not too large. The battery determines current.

My alt may well be too small. The SPECS from US Batts state the amps should be...as they say.

[mitiempo]

Originally Posted by jackt

Maybe you're not listening! I understand their SPECS as stating the ideal amps to get an alternator to put out. That would make perfect sense - you need a decent alternator with decent amps - they are recommending a value! What's the problem with that interpret. Regardless, it's utterly opaque and difficult to convert specs PER CELL to a specific case.

There's no problem except your interpretation. You do not have to worry about each cell.

Your charger should be 10% of bank size in AH. 46.4 (rounded to 50) amps for good battery life or larger.

14.7 volts absorption for about 4 hours.

What's not to understand?

[john61ct]

Originally Posted by mitiempo

Given the above there is no logic in using a charger that is larger than the batteries acceptance plus any house loads. A charger of 60 amps or so would be a good choice and an alternator of 80 to 100 amps.

Not saying "should" but when you can afford it, some reasons for going bigger:

House loads can grow.

Next bank may be bigger.

Next bank may be a chemistry with (much) higher acceptance rate, and shorter engine/genset runtimes possible.

Especially with Alt mods (space, mounting, belts & pulleys) best to spend that upgrade money just once.

Also why a programmable unit to fine-tune setpoints.

Funds may not permit, but if possible remember banks are consumables, most of the surrounding infrastructure may (should) be "the last one" you pay for.

[lateral]

Originally Posted by jackt

Maybe you're not listening! I understand their SPECS

What does Maine Sail say? Isn't he the guru?

Yep, AFAIK.
My system is based on his & Mitiempo's advice.
Make sense to me.
Google; His wisdom based on his experience with "murdered batteries" is all over the net sailing forums.

[john61ct]

This should be all you need to know now:

Minimum size charger at .1C (1/10th of 460, rounded up) you should use is 50A, better IMO to get a 100A charger.

Charge at 14.7A, until "full", meaning current drop to say 10A, only then go to Float.

If your charger doesn't allow this, measure manually to calibrate Abs time, likely between 4-5 hours? Default to longer rather than shorter, gassing's no problem with FLA, just replenish more often.

Ideally hit this Full level every cycle. Missing that more than occasionally will reduce lifespan. Same with going below 50%, try to avoid doing that.

Equalize/condition regularly (monthly?) according to vendor specs, ideally manually, supervising in person.

[mitiempo]

Originally Posted by john61ct

This should be all you need to know now:

Minimum size charger at .1C (1/10th of 460, rounded up) you should use is 50A, better IMO to get a 100A charger.

Charge at 14.7A, until "full", meaning current drop to say 10A, only then go to Float.

If your charger doesn't allow this, measure manually to calibrate Abs time, likely between 4-5 hours? Default to longer rather than shorter, gassing's no problem with FLA, just replenish more often.

Ideally hit this Full level every cycle. Missing that more than occasionally will reduce lifespan. Same with going below 50%, try to avoid doing that.

Equalize/condition regularly (monthly?) according to vendor specs, ideally manually, supervising in person.

I agree with the above.

[StuM]

Originally Posted by john61ct

Charge at 14.7A, until "full", meaning current drop to say 10A, only then go to Float.

Presumably, you mean 14.7V?

So you set your charger to NOT have a bulk (current limited) stage, but throw all the Amps at your batteries that they can take at absorption voltage right from the start?

Hmmm, wonder why EVERY battery manufacturer specifies a charging regime with an initial bulk, current limited, stage.

[mitiempo]

Originally Posted by StuM

Presumably, you mean 14.7V?

So you set your charger to NOT have a bulk (current limited) stage, but throw all the Amps at your batteries that they can take at absorption voltage right from the start?

Hmmm, wonder why EVERY battery manufacturer specifies a charging regime with an initial bulk, current limited, stage.

He means 14.7, as stipulated by the manufacturer. Remember that bulk and absorption voltages are the same. The charger in bulk will bring the batteries up to 14.7, holding it there for the length of the absorption stage.

[StuM]

Originally Posted by mitiempo

He means 14.7, as stipulated by the manufacturer.

14.7 What? Certainly not the 14.7A he stated.

So much wrong with this:

Remember that bulk and absorption voltages are the same.

1. Bulk charging doesn't have a voltage. It starts somewhere above the existing battery voltage and increases steadily until absorption voltage is reached (So in a way it does have a maximum voltage.)

When you start bulk charging a battery at , say, 50% of SOC, the charging voltage will be regulated to limit current. It could well be below float voltage initially to avoid pushing too high a current and overheating the battery. As the SOC increases, the current is kept constant by steadily increasing voltage up to the absorption voltage. (That steady current should be in accordance with the manufacturer's recommended charge rate(s). Exceeding the recommendation is likely to overheat and damage the battery).

The charger in bulk will bring the batteries up to 14.7, holding it there for the length of the absorption stage.

14.7V is the charging voltage, not the battery voltage.

The charger in bulk will bring the charging voltage up to 14.7 while still maintaining the bulk current limit.

Once it can no longer deliver the set bulk current at 14.7, it will go into absorption mode by holding the charging voltage steady at 14.7 and the current being pushed into the battery will decrease as the battery internal voltage continues to increase towards 14.7V and the potential difference between the charging source and the battery's internal voltage decreases.

Once the internal voltage (actually surface charge) of the battery gets "up to 14.7V", no further charging can take place. That's when absorption ends, not when it starts. (Actually, a bit before that, when the battery voltage is slightly below 14.7 and some small amount of current is still flowing).

[john61ct]

14.7V (yes, volts, thanks 8-) is simply the goal, the target setpoint during bulk.

As I made clear earlier, Bulk is NOT "current limited" as in somehow sensing a max amps level is "safe" for the battery.

So yes, charge sources just throw out as much as possible - which means as much as the bank's Resistance **allows**, up to the charge source's maximum.

Some sophisticated more expensive chargers allow you to derate their output, so a 120A charger can be set for 60 or 80A, so you don't blow mains power fuses or overheat a dumb alternator.

And some bench power supplies let you manually tweak an infinitely variable current control.

If such a power control, like cheaper MegaWatt, as opposed to pricier MeanWell, have no overload protection, a large high-CAR bank like LFP can easily burn out the power source.

But such current customization is relatively rare, certainly not part of the standard charge cycle algorithms.

When that target voltage (here 14.7V) is reached and maintained, transition from Bulk to Absorb stage, then current starts to decline, but again this is under the bank's "control", nothing to do with the charge source, which is simply controlling voltage and trying to still "push" out its max current level.

A higher CAR chemistry will continue to accept more amps even as SoC gets up there, allows for shorter engine runtimes, can make it economically to invest more in the bank besides just greater longevity.

Putting a low current charge into such banks is wasting that potential, which is why for example Lifeline specs a **minimum** of .4C charge rate.

Which for a 464AH set would mean 200A minimum.

If your old-school FLA only accepts .15C then buying that same charger would seem like overspending, but if your next bank is higher quality and higher CAR, it will turn out to have been a good investment.

And certainly won't do any harm, even to a single 100AH battery.

[StuM]

Originally Posted by john61ct

Some sophisticated more expensive chargers allow you to derate their output, so a 120A charger can be set for 60 or 80A, so you don't blow mains power fuses or overheat a dumb alternator.

Or overheat a battery?

[john61ct]

No, it is just to protect the upstream infrastructure, not batteries.

That's why good chargers and alt regulators have a temp sensor wire that goes to the bank.

Rather than running a lower charge rate all the time, just scale it back as needed in real time.

Also for varying the voltage setpoint, likely you've seen "temperature compensation" as a feature? Essential AFAIC

[mitiempo]

Originally Posted by StuM

14.7 What? Certainly not the 14.7A he stated.

So much wrong with this:
1. Bulk charging doesn't have a voltage. It starts somewhere above the existing battery voltage and increases steadily until absorption voltage is reached (So in a way it does have a maximum voltage.)

When you start bulk charging a battery at , say, 50% of SOC, the charging voltage will be regulated to limit current. It could well be below float voltage initially to avoid pushing too high a current and overheating the battery. As the SOC increases, the current is kept constant by steadily increasing voltage up to the absorption voltage. (That steady current should be in accordance with the manufacturer's recommended charge rate(s). Exceeding the recommendation is likely to overheat and damage the battery).

14.7V is the charging voltage, not the battery voltage.

The charger in bulk will bring the charging voltage up to 14.7 while still maintaining the bulk current limit.

Once it can no longer deliver the set bulk current at 14.7, it will go into absorption mode by holding the charging voltage steady at 14.7 and the current being pushed into the battery will decrease as the battery internal voltage continues to increase towards 14.7V and the potential difference between the charging source and the battery's internal voltage decreases.

Once the internal voltage (actually surface charge) of the battery gets "up to 14.7V", no further charging can take place. That's when absorption ends, not when it starts. (Actually, a bit before that, when the battery voltage is slightly below 14.7 and some small amount of current is still flowing).

I read 14.7 volts as that is what it should have been.

Bulk charging has a setpoint, in this case it should be 14.7 volts. The charger, as joh61 states, puts out all current up to its maximum as long as the battery will accept it. The only regulation at this point. The only limit is the current the battery will accept. This is a constant current stage. Once the battery reaches that voltage the charger goes into absorption, holding that voltage for a period of time, ideally several hours. During the absorption stage the batteries continue to accept a declining current. This is a constant voltage stage. At the end of the preset absorption stage the charger changes to a float voltage, 13.5 volts for example. The batteries are still accepting current, but very little at this point. After an absorption stage the batteries should be close to fully charged. If the absorption stage is too short the charger will switch to float voltage before the batteries are close to fully charged. This means that the batteries will not likely be fully charged for many many hours if not days. The batteries should be only a few percent away from full at the end of the absorption stage. When the batteries have achieved their absorption voltage charging will (and needs to) continue until the current the batteries are accepting drops very low.

In bulk the charger does not maintain the current, but is wide open until the set voltage (14.7) is reached. The battery is the determining factor, not the charger.

You state " once the internal voltage (actually surface charge) of the battery gets up to 14.7 volts absorption ends". Not true. Absorption is a timed event and must continue until the battery is very close to fully charged. When the battery hits 14.7 volts it will continue to charge with a still high but declining current as the charge is absorbed into the plates. This is the reason for a long absorption time.

[john61ct]

Originally Posted by mitiempo

At the end of the preset absorption stage the charger changes to a float voltage, 13.5 volts for example. The batteries are still accepting current, but very little at this point. After an absorption stage the batteries should be close to fully charged.
...
Absorption is a timed event and must continue until the battery is very close to fully charged.

Please don't take this as disputatious, just my preference.

Absorption should not stop until the battery is "100% full". Let's say that is spec'd by the manufacturer as "hold 14.7V until current drops to .015C".

How that is actually defined in practice may be limited by the charge source's programming options.

I would argue for making sure, if you are forced by those limitations to guesstimate a formula based on Absorption **time**, that you will slightly overcharge (current & time, not voltage) more frequently than you prematurely go to Float. This is especially necessary when there are ongoing variable-current (likely unpredictable) loads being carried while the bank is charging.

In my opinion Float is NOT to be used for "finishing" any last climb to 100% SoC.

Only to counteract self-discharge in storage contexts, and to keep the power supply on and available to continue to carry those ongoing loads, when that is preferable to unnecessarily starting another bank discharge cycle.

Yes, a nit pick I'm aware.

[mitiempo]

Originally Posted by john61ct

Please don't take this as disputatious, just my preference.

Absorption should not stop until the battery is "100% full". Let's say that is spec'd by the manufacturer as "hold 14.7V until current drops to .015C".

How that is actually defined in practice may be limited by the charge source's programming options.

Problem is that for most chargers - AC powered ones - absorption is a timed event, not current sensed. The absorption time should be long enough for a full charge but as you say with other loads that will vary somewhat. Overcharging is not really an issue as the battery only accepts what it will. Fluid levels may drop over time so should be checked regularly, at least until their habits are known. Temp sensors as found on Promariner's PronauticP chargers (and the Sterling under its other label) are essential I believe.

If not fully charged after absorption the batteries should at least be very close to full.