AGMs and Dumb Regulator . . .

[FlyingCloud1937]

Originally Posted by Marqus

During the equivalent of Bulk charging, the dumb regulator would not exceed 14.4volt.
Later on (equiv of Absorption), as you say "any over voltage is wasted as heat". So the temperature feedback loop would reduce the voltage in order to contain the heat.

I get the feeling I'm not getting your point - what am I missing?

Temp of the bat changes the required voltage to charge, that's why all good charge sources are temp compensated.

Without measuring the voltage a regulator wouldn't be able to regulate. Temp doesn't determine SOC.

Lloyd

[hellosailor]

If the only control was temperature, I would guess that you'd par boil your battery. It would be kept as hot as the sensor thought was allowable, all the time, which means it would be getting a maximum charge way longer than it was needed.

[Maine Sail]

Originally Posted by Marqus

During the equivalent of Bulk charging, the dumb regulator would not exceed 14.4volt.
Later on (equiv of Absorption), as you say "any over voltage is wasted as heat". So the temperature feedback loop would reduce the voltage in order to contain the heat.

I get the feeling I'm not getting your point - what am I missing?

You still have to have voltage regulation as it is still quite easy to have situations where you have a cool battery but a voltage that can be too high.

Take today for instance. My batteries never got above 70F while running the engine but they were at absorption voltage and near full. Not enough current to raise the temp beyond 70F but I still needed to regulate the voltage or the alt could be pumping in 17-18+ volts which is not good for the batts...

[Marqus]

Originally Posted by Maine Sail

My batteries never got above 70F while running the engine but they were at absorption voltage and near full. Not enough current to raise the temp beyond 70F but I still needed to regulate the voltage or the alt could be pumping in 17-18+ volts which is not good for the batts...

That is quite significant to me.

I had thought that if you raised the charging voltage to a lead-acid battery, the effect would be an increase in current (via Ohms law). If the battery is already in a high SOC, this increased current would not increase the SOC but instead be consumed by a reaction that generates excess heat which can damage the battery.

What Maine Sail says above means that I thought wrong. So, the charging voltage can go up, but even though the current does not increase (and temperature does not rise), something can still happen to cause damage to the battery.

Can anyone cast more light on the mechanism of this damage, just to improve our understanding?

[FlyingCloud1937]

Originally Posted by Marqus

That is quite significant to me.

I had thought that if you raised the charging voltage to a lead-acid battery, the effect would be an increase in current (via Ohms law). If the battery is already in a high SOC, this increased current would not increase the SOC but instead be consumed by a reaction that generates excess heat which can damage the battery.

What Maine Sail says above means that I thought wrong. So, the charging voltage can go up, but even though the current does not increase (and temperature does not rise), something can still happen to cause damage to the battery.

Can anyone cast more light on the mechanism of this damage, just to improve our understanding?

Yes, it's called a big heat sink.The voltage will rise faster than the heat can build. So you end up with the second leading cause of bat-failure...positive grid plate corrosion..aka: chronic overcharge.

remember, current charges batteries, the diff... between voltage of the bats..and the charge source=current flow into the bats...

bats will accept current as long as you apply it...either by chemical action=(charge) or heat dissipation=(overcharge)
a bat by design has both, a set voltage, and a temp as a result of chem..reaction=V=SOC.



Lloyd

[FlyingCloud1937]

Originally Posted by Maine Sail

You still have to have voltage regulation as it is still quite easy to have situations where you have a cool battery but a voltage that can be too high.

Take today for instance. My batteries never got above 70F while running the engine but they were at absorption voltage and near full. Not enough current to raise the temp beyond 70F but I still needed to regulate the voltage or the alt could be pumping in 17-18+ volts which is not good for the batts...

That doesn't quite ring true, as you previously stated, that you didn't have a smart regulator, for your alternator.

i know of no interanly regulated alternator that does temp..... corrected charge regieme...

Did you finally install a smart regulator?

Lloyd

[Maine Sail]

Originally Posted by FlyingCloud1937

That doesn't quite ring true, as you previously stated, that you didn't have a smart regulator, for your alternator.

i know of no interanly regulated alternator that does temp..... corrected charge regieme...

Did you finally install a smart regulator?

Lloyd

Lloyd,

What part does not "ring true"?

1- If I had an external regulator, and my bank was near full, it would not have been at absorption voltage it would have likely been in float...

2- My regulator is internal and dumb it only knows two things wide open/constant current/bulk and the absorption/voltage limiting set point. Once out of "bulk", meaning the battery bank has reached the voltage limiting set point of the internal regulator, the voltage is limited to about 14.4V.

3- I had gone out for a sail which required motoring out of the river. Once outside I sailed for about 60 minutes and the wind died to below my patience level. This required me to motor back across the bay and back up into the river. The bank was at a low of perhaps 99% SOC as the only things I had running were the depth/wind & AP (on STBY).

4- Due to the bank being near full it was taking very little current at 14.4V (absorption), probably less than 2% of capacity but I did not specifically look. At 100% SOC it is less than 2% but I was probably at 99% starting out..

Despite running the motor for well over an hour the bank was still below 70F as measured with my Raytek pyrometer.. I measured it out of pure curiosity based on the assertion that one might be able to regulate charging based on voltage only.

What I found is that when batteries are near full, and taking low acceptance current, the voltage with low current alone is not always sufficient enough to raise the temp of the batteries into the range where temp limiting would even be necessary. My bank never even got to "industry baseline" for temp. If I had been regulating by only temperature, with no voltage limiting, my alt could have been pumping 17+ volts into the bank.



As another data point beyond the above, I had a customers wet cell battery on an equalizing charge two nights ago and the battery never broke 75F. Ideally I should probably be equalizing with a bank starting at 80F but that is not always possible in my shop as I'd be sweating bullets if I did. I also monitor battery temp when equalizing with a pyrometer to stay safe. I also only ever do "attended" equalizing..

Battery was seeing low current, as it should while equalizing, and 15.5v for well over an hour and still never hit the industry standard baselines of 77F or 80F.. You can have batteries that can be cool while still seeing electrolyte boiling voltage levels and this is most likely why temp only regulation is not used...

[Maine Sail]

Originally Posted by Marqus

That is quite significant to me.

I had thought that if you raised the charging voltage to a lead-acid battery, the effect would be an increase in current (via Ohms law). If the battery is already in a high SOC, this increased current would not increase the SOC but instead be consumed by a reaction that generates excess heat which can damage the battery.

What Maine Sail says above means that I thought wrong. So, the charging voltage can go up, but even though the current does not increase (and temperature does not rise), something can still happen to cause damage to the battery.

Can anyone cast more light on the mechanism of this damage, just to improve our understanding?

The current will increase with voltage increases. When I equalizes batteries they often move from a float voltage and accepted current of .2-.5% of capacity to 1.5-3% of capacity. This is done by simply going from 13.2 - 15.5V. In a cool environment or cool waters and cool battery compartment, this is often still not enough to raise the battery temp above industry baseline. In warmer temps I would suspect some more temp increase.

If you supplied an over voltage for long enough I am certain the temps would increase, even in a cool environment, but by then I suspect the damage would have been done. How long it would take, at a completely unregulated voltage I can't really say, and I'm not willing to try...

Even at 15.5V and as little as 2% acceptance the banks are audibly boiling even with battery temps below 80F..

[FlyingCloud1937]

Originally Posted by FlyingCloud1937

That doesn't quite ring true, as you previously stated, that you didn't have a smart regulator, for your alternator.

i know of no interanly regulated alternator that does temp..... corrected charge regieme...

Did you finally install a smart regulator?

Lloyd

Main Sail,

I'll eat the crow that I prepared for myself...sorry

Don't know why I misunderstood the post last night...but I sure must have. Because my post when I read it this morning...didn't make sense to me.

I was either up to late, or it was that shot of spiced rum.

Lloyd

[Maine Sail]

Originally Posted by FlyingCloud1937

Main Sail,

I'll eat the crow that I prepared for myself...sorry

Don't know why I misunderstood the post last night...but I sure must have. Because my post when I read it this morning...didn't make sense to me.

I was either up to late, or it was that shot of spiced rum.

Lloyd

Not a problem! I was just trying to figure out how I could have explained it better.. Mmmm Rum!

[Sailorman Ed]

Great information and mostly past me but what should I be doing with my internally regulated dumb alternator and my 360 AH gel cell house bank? On shore power, I have a 3 stage charger set to "gel" and will have a solar charger also set to "gel". In the past, I have just monitored the voltage during the limited motoring time, but what should I do for going for days on the motor down the ICW? My start batt is normal LA...any way to use a Blue Sea ACR to limit the voltage going into my gels with prolonged motoring?

[Maine Sail]

Originally Posted by Sailorman Ed

Great information and mostly past me but what should I be doing with my internally regulated dumb alternator and my 360 AH gel cell house bank? On shore power, I have a 3 stage charger set to "gel" and will have a solar charger also set to "gel". In the past, I have just monitored the voltage during the limited motoring time, but what should I do for going for days on the motor down the ICW? My start batt is normal LA...any way to use a Blue Sea ACR to limit the voltage going into my gels with prolonged motoring?

make darn sure your dumb reg can not regulate any higher than 14.1V!!!! Over charging gel batteries is not a fixable event...

An ACR will not limit voltage. You ideally need a new regulator unless your stock alt is very old and regulated at 13.8V, as many older ones were. Most newer ones are 14.2V - 14.6V which is too high for gels. When you get a new regulator be sure to take advantage of temp compensation.

Gels can last longer than any other battery I've come across thus far but can also be destroyed very easily by over charging..

[Sailorman Ed]

I came across the Sterling ProReg-B which looks good on paper and a reasonable cost. Has a setting for gel cells. Any issues to use one of these to charge my gel cells? Not quite sure how to also charge my normal flooded starting battery first before switching to the house bank