Overheating Battery Issues

[btrayfors]

Noelex is correct: almost all modern multi-stage marine battery chargers use constant voltage for the absorption, float, storage (in the case of Victron), and equalization phases.

There is no current limitation on the bulk phase, except for the ability of the battery bank itself to absorb current. When the voltage reaches the predetermined level for absorption, then the voltage is held constant at the predetermined absorption phase level.

And, AGMs can absorb a LOT of current. When 50% discharged, for example, Lifeline AGMs can absorb 1.3X rated 20-hour capacity @ 14.4VDC. If voltage is raised, they can take a lot more. And, if they're more deeply discharged, they can take at least 5X the rated capacity.

However, at any given state of charge, a battery will accept what it's going to accept at any given voltage and temperature. No more. Doesn't matter if you use a 1,000 amp charger, if the battery bank only wants 50 amps @ 14.4VDC, that's all it's going to take.

Bottom line: Battery chargers are voltage limited in all phases except bulk, though there is a maximum cutoff voltage at which time the charger goes into the absorption phase. The batteries themselves determine how much current they will accept.

Bill

[goboatingnow]

Originally Posted by Maine Sail

Even a "dumb" regulator has both bulk/constant current and absorption voltage.

Bulk = Anything before the batteries rise to the absorption voltage limit. This current can be limited by either the batteries or the limit of the charge source. If the bank will take 70A and you have a 50A alt it will pump out what it can until the voltage comes up to the absorption setting. If the batteries will only take 80A and you have a 120A alternator the alt will pump out 80A until the terminal voltage rises to the "limiting" set point then enter "absorption" or voltage limiting mode..

Absorption = The voltage limit of the regulator. Current is applied to the battery via pulsing the field so as not to "over shoot" the voltage limit.

Voltage regulators are nothing more than voltage limiters..... They limit voltage in absorption and then limit at a further reduced voltage when in float. Any time before they are limiting voltage at the set point the alt is in constant current mode. The regulator will turn the power on and off, very quickly, to match what the battery bank needs, in current, to maintain, but not over shoot, that voltage limit..

Any charge source that regulates to voltage, once the voltage set point is attained, is a constant voltage charge source. Just because bulk is technically a constant current (full field) does not mean the device is not a constant voltage charger, alt, regulator, solar controller etc..

Most regulators are either series or shunt or now switched mode. They don't regulate by "pulsing" the battery they merely reduce their output ( the exception being PWM solar controllers which use the current source characteristics of solar ) in series pass or shunt regulation the excess is lost as heat. In switched mode the pulse width into the inductor is reduced resulting In lower energy and hence lower DC output power.

Note the term voltage regulation is somewhat misleading. The regulator cannot regulate the battery voltage down below its SOC. point. It limits the upper voltage by in effect increasing. It's output resistance ,the battery chemistry is the primary determination of terminal voltage not the charger.

Dave

[Maine Sail]

Originally Posted by goboatingnow

Most regulators are either series or shunt or now switched mode. They don't regulate by "pulsing" the battery they merely reduce their output ( the exception being PWM solar controllers which use the current source characteristics of solar ) in series pass or shunt regulation the excess is lost as heat. In switched mode the pulse width into the inductor is reduced resulting In lower energy and hence lower DC output power.

Note the term voltage regulation is somewhat misleading. The regulator cannot regulate the battery voltage down below its SOC. point. It limits the upper voltage by in effect increasing. It's output resistance ,the battery chemistry is the primary determination of terminal voltage not the charger.

Dave

Perhaps "pulsing" was a bad choice of words for how they control the field.. Bottom line take away is they control the current so as not to over shoot the voltage limit.

I agree 100% that "voltage regulation" is misleading and why I suggest to consider them as "voltage limiters" instead. I use the word "limit" because as stated in your last sentance they can't "reduce" a voltage only limit it. If the voltage goes over they simply shut off until the voltage is no loger above the set point.

[noelex 77]

Originally Posted by goboatingnow

Note the term voltage regulation is somewhat misleading. The regulator cannot regulate the battery voltage down below its SOC. point. It limits the upper voltage by in effect increasing. It's output resistance ,the battery chemistry is the primary determination of terminal voltage not the charger.

Dave

The lowest target charging voltage is well above the batteries "SOC point".
As we always want charging voltages above the SOC point it seems irrelevant that the charger cannot adjust the battery voltage below this level.

The charger is always in control of the terminal voltage during the absorption and float stages of charging.
With the push of few buttons on the charger the terminal voltage can adjusted.

Only during the bulk phase of charging does the battery have any say in the voltage and even then the voltage is depdent on both the battery and charger. Change either one and the terminal voltage will change.

The important point is regulators on all devices charger, solar, wind and alternator do an vital job in controlling the voltages during charging and its essential that they are adjusted to meet the requirements of the battery.

[FlyingCloud1937]

Originally Posted by noelex 77

The lowest target charging voltage is well above the batteries "SOC point".
As we always want charging voltages above the SOC point it seems irrelevant that the charger cannot adjust the battery voltage below this level.

The charger is always in control of the terminal voltage during the absorption and float stages of charging.
With the push of few buttons on the charger the terminal voltage can adjusted.

Only during the bulk phase of charging does the battery have any say in the voltage and even then the voltage is depdent on both the battery and charger. Change either one and the terminal voltage will change.

The important point is regulators on all devices charger, solar, wind and alternator do an vital job in controlling the voltages during charging and its essential that they are adjusted to meet the requirements of the battery.

Properly known, they're Charge Regulators. They do control the voltage of the charge during charging, so they are called a voltage regulator, as they pertain to charging.

It's semantics not to call it a voltage regulator, bc the intended use is charging, and not discharging.

Lloyd

[goboatingnow]

Originally Posted by noelex 77

The lowest target charging voltage is well above the batteries "SOC point".
As we always want charging voltages above the SOC point it seems irrelevant that the charger cannot adjust the battery voltage below this level.

The charger is always in control of the terminal voltage during the absorption and float stages of charging.
With the push of few buttons on the charger the terminal voltage can adjusted.

Only during the bulk phase of charging does the battery have any say in the voltage and even then the voltage is depdent on both the battery and charger. Change either one and the terminal voltage will change.

The important point is regulators on all devices charger, solar, wind and alternator do an vital job in controlling the voltages during charging and its essential that they are adjusted to meet the requirements of the battery.

No wish to descend to too many technical not picking. But I was talking on the general case. The low input equivalent impedance of a large LA bank means that a low powered charger with a corresponding higher output impedance has a limited range over which it can raise battery voltage ( or lower it ) all that happens is the charger will not have the current capacity to raise the terminal voltage too much ( obviously the battery is being destroyed here)

With high charge chargers this relationship changes and without voltage regulation such chargers would rapidly destroy battery banks

Dave