Getting to absorption but not always float.

[GILow]

Originally Posted by StuM

The problem with any fixed absorption time is that it assumes a fixed sufficiently large charge source output to meet house loads and still maintain the full charge current. . Neither of which are common with solar/wind and a boat with varying house loads.

Yeah, I’ve never understood how the Victron chargers decide they’ve completed absorption when I’m stuffing around with water pumps, the stereo, the coffee machine or power tools.

They seem to come in somewhere between two to two and half hours when there’s enough sunshine, but other than that I really don’t know what they are thinking,

[StuM]

Originally Posted by RaymondR

To take a legalistic viewpoint mate, you introduced the subject of recharging:

"Now, I’ve got another 380 Watts of solar on its way, but I think I am going to have to start using the engine to charge things from time to time."

in your OP.

Yep, and his question was how frequently to do so, not for how long or what time of day to do so.


> "How long would you let the bank go without completing absorption before you started to worry? A day, a week?"

[noelex 77]

Originally Posted by GILow

Yeah, I’ve never understood how the Victron chargers decide they’ve completed absorption when I’m stuffing around with water pumps, the stereo, the coffee machine or power tools.

They seem to come in somewhere between two to two and half hours when there’s enough sunshine, but other than that I really don’t know what they are thinking,

The Victron solar controllers display absorption time in a weird way. Rather than displaying the time the batteries are sitting at the absorption voltage, they display the time from when the absorption voltage was first reached (providing the re-bulk parameters have not been met). Fortunately, the controllers actually count the absorption time correctly.

So the absorption time listed on the app does not reflect the true absorption time. This, combined with the adoption of variable absorption time (based on start up voltage), means that the displayed absorption time will seem to fluctuate for no apparent reason.

[GILow]

Originally Posted by noelex 77

The Victron solar controllers display absorption time in a weird way. Rather than displaying the time the batteries are sitting at the absorption voltage, they display the time from when the absorption voltage was first reached (providing the re-bulk parameters have not been met). Fortunately, the controllers actually count the absorption time correctly.



So the absorption time listed on the app does not reflect the true absorption time. This, combined with the adoption of variable absorption time (based on start up voltage), means that the displayed absorption time will seem to fluctuate for no apparent reason.

Right, well I would never have figured that one out.

I think I still need to think about the implications of this to see if there’s some way of extrapolating a better estimate of true SOC based on this new understanding.

Or I could just sail north.

[rslifkin]

If you have a battery monitor or smart shunt and a GX device in the system, the Victron MPPTs get a bit smarter about when to end absorption. Then, instead of only going based on time and/or output current from the controller, they can go by time and/or actual current flowing into the batteries (accounting for loads).

[Thumbs Up]

There is only one good way (with those batteries) to know your true state of charge and that is with a hydrometer. If your system does not have a remote battery temperature sensor, and you changed climate you might need to adjust your temp. setting. If your batteries are using less water than normal, you are probably under absorbing. As long as you are at least reaching absorption voltage every day and don't go under 50% SOC, your golf cart batteries are going to be pretty happy. Running your engine near the end of a charge cycle is a waste, better to run it for an hour at the beginning of the charge cycle (in the morning). Yes I did read the question earlier. You did state: "good chance I'll want to use the engine at some point in a week........ not all that clear on what is happening during the absorption phase" How long before you worry? That's on you mate.

[LoudMusic]

I have lithium batteries and heaps of solar so they tend to fill at least once per week. But I'm also not fussed if it goes a couple weeks. For me the concern is more about reaching full voltage in order to synchronize the battery display.

[GILow]

Originally Posted by Thumbs Up

There is only one good way (with those batteries) to know your true state of charge and that is with a hydrometer. If your system does not have a remote battery temperature sensor, and you changed climate you might need to adjust your temp. setting. If your batteries are using less water than normal, you are probably under absorbing. As long as you are at least reaching absorption voltage every day and don't go under 50% SOC, your golf cart batteries are going to be pretty happy. Running your engine near the end of a charge cycle is a waste, better to run it for an hour at the beginning of the charge cycle (in the morning). Yes I did read the question earlier. You did state: "good chance I'll want to use the engine at some point in a week........ not all that clear on what is happening during the absorption phase" How long before you worry? That's on you mate.

Seriously, you still haven’t grasped the question.

But thank you for trying.

[sailorboy1]

Originally Posted by GILow

One for the battery fanatics.

I’ve got a bank of 6 Trojan T105s charged by solar with Victron controllers and a Victron battery sense.

Back in South Australia the bank would be in float before lunch time, often by 10 am in summer.

But I’ve sailed south to Tasmania and I am now at 43 degrees south, not 35.

I’ve noticed that for last week or so that the bank is not always getting to float. The absorption phase is beginning but not completing, there simply isn’t enough solar to get the job done.

Now, I’ve got another 380 Watts of solar on its way, but I think I am going to have to start using the engine to charge things from time to time.

How long would you let the bank go without completing absorption before you started to worry? A day, a week? I’ll run the engine when I have to, but I’d rather keep that particular joy to a minimum.

Matt

I tried to not allow my old T105s from getting fully charged for more than a week. The whole reason you use T105s is they are tough and cheap. You abuse them, taking reasonable care, and replace them.

But in 9 years I NEVER EVER saw them get to “float” by noon! They took hours at absorption to get low enough acceptance to go into float.

[GILow]

Originally Posted by sailorboy1

I tried to not allow my old T105s from getting fully charged for more than a week. The whole reason you use T105s is they are tough and cheap. You abuse them, taking reasonable care, and replace them.



But in 9 years I NEVER EVER saw them get to “float” by noon! They took hours at absorption to get low enough acceptance to go into float.

Well, cheap is relative, but yes, the T105s have a good reputation for durability.

Back in south Australia I was getting very good solar input by 9 am, sometimes even by 8am. Also, the power consumption of this boat is trivial, overnight I would normally get through only 20 AH at the dock. It’s a quite a bit more now I have AIS and the anchor lights going, but there’s never more than 70 AH to find in the morning.

So noon float was pretty common, though 10 am also happened once or twice in summer. Sure not going to happen now.

Once a week to full charge seems to be a figure many of us have worked with, without apparent problems for the batteries, so I’m happy with that. Maybe we could go longer but really, it’s plenty long enough.

And who wants to spend more than a week in one anchorage anyway? Bound to be some motoring on the way to next perfect spot.

[RaymondR]

T105s are pretty rugged.

I have 2 banks of them in my support/storage van which are 5-6 years old. In a couple of weeks I will depart for my winter cruise and not be back until NOV-Dec. I will fill them with water before I leave and when I get back refill them again. I have been doing this since 2016 and even though they're probably half dry so far they seem to recover.

I suspect that of I removed the acid and filled them with distilled water and turned the regulator voltage down they would probably de-sulphate and last forever with a 5 in use, 7 de-sulphating cycle but too many other boat projects have priority.

[GILow]

Originally Posted by RaymondR

T105s are pretty rugged.

I have 2 banks of them in my support/storage van which are 5-6 years old. In a couple of weeks I will depart for my winter cruise and not be back until NOV-Dec. I will fill them with water before I leave and when I get back refill them again. I have been doing this since 2016 and even though they're probably half dry so far they seem to recover.

I suspect that of I removed the acid and filled them with distilled water and turned the regulator voltage down they would probably de-sulphate and last forever with a 5 in use, 7 de-sulphating cycle but too many other boat projects have priority.

Yep, they came highly recommended by many cruisers, which is why I reluctantly parted with a fair bit of cash when my last bank of cheaper batteries died a premature death.