Windlass, battery, solar panel

[Bulawayo]

Well, Stu, you clearly have issues but not sure if its with me or my post. Either you dont understand batteries or .........?
It is very well documented that recharging LA batteries (amongst others) is very difficult to achieve as they go into super slow absortion/float mode at around 80%. This is a well acknowledged information - but not just by myself but by respected publications like Practical Sailor. Look it up. Im surprised its even being questioned. The sun also rises in the East or do I have to prove that as well? Its of no value to me to have to prove this to someone - I recognise and acknowledge the information and experience it regularly. This is one of the reasons that conventional installed battery capacity is often so high on a crusing boat. Anyone that pulls their LA units regularly below 50% shall also soon experience the pain of replacements. Keeping batteries at >80% of capacity is just about unheard of unless a generator is kept running. We have over 1000 watts of solar and 2x D400's but even so we do not maintain >80% all the time. We are looking to change to Lithion Ion but that wont happen very quickly as I need to understand the systems more.
So, how do you prove that you maintain LA batteries at over 80%? I very much doubt that and I have never heard of anyone that really does live aboard make such a claim. How do you achieve this? What are your loads? What are your batteries and what is the recharge regime? However, you are turning this into something personal and away from the subject matter.
I dont allege to be a 12v genius but I do know that being reliant on a 125A battery supported by just 30 watts of solar, to supply a windlass that draws 50-60amps is going to be a recipe that one day shall cause angst. The maths is not difficult to do when you factor in emergencies. I am aware that under 'average' conditions (whatever they are) there shall not be any issues. Its when the smelly stuff hits the fan and there is no opportunity to start initiating Plan B that it all goes to rat poo.

Originally Posted by StuM

Clearly you are still confused over amps v amp hours.
http://www.cruisersforum.com/forums/...ml#post1933764

It's the part in bold that has me puzzled. I have no problems with charging LA batteries to well over 80%.

FWIW, I prefer to keep my batteries over 80% as much of the time as possible.

Please provide your documentation that says that wet batteries are very hard to recharge over 80%.

[StuM]

Originally Posted by Bulawayo

Well, Stu, you clearly have issues but not sure if its with me or my post. Either you dont understand batteries or .........?
It is very well documented that recharging LA batteries (amongst others) is very difficult to achieve as they go into super slow absortion/float mode at around 80%. This is a well acknowledged information - but not just by myself but by respected publications like Practical Sailor. Look it up. Im surprised its even being questioned.
...
So, how do you prove that you maintain LA batteries at over 80%? I very much doubt that and I have never heard of anyone that really does live aboard make such a claim. How do you achieve this? What are your loads? What are your batteries and what is the recharge regime?

It's apparently a disagreement about the meaning of "very difficult".
And a misunderstanding of what absorption and float modes really are.

Batteries don't suddenly "go into super slow absortion/float mode"

They initially go into absorption (sp) mode when they reach around 80%. This mode is constant voltage with current steadily falling as the SOC increases.

The charging rate doesn't suddenly become "super slow". It starts off at the same rate as Bulk charge, but steadily tapers down from that point as the current the batteries can accept goes down. Another 4-5 hours with enough Amps available is generally sufficient to bring them the rest of the way up to full SOC again.

And that's what the solar tends to give you. The nice thing is that as the sun goes down in the afternoon and the Watts from solar goes down, the required charging Amps goes down at a similar rate.


I have 1000Ah of AGM. That means that I can burn 200Ah with no input and still keep them above 80% SOC. I have 800W of solar plus alternators on two engines. Any one of those three can give me around 30-50 Amps by itself.

If I can start fully charged in the late afternoon, that 200Ah is generally enough to see me through the night.

So the way to keep above 80% most of the time is to hit the batteries with a heavy alternator charge first thing in the morning when they can take all the Amps you can throw at them and then let solar gradually put the rest of it back throughout the day.

[Bulawayo]

We'll have to agree to continue disagreeing. Recharge regimes certainly do go into slow recharge at around 80%. They do not just slowly taper off. What you are writing about is not standard. This explains your confusion. This is why there are various batteries management recharge systems offered; specifically produced to provide the system you describe. Regardless you'll find plenty of articles on-line confirming that conventional batteries will not accept bulk charging over 80%. This is one of the benefits of Lithiom Ion technology which can be recharged via bulk. You mention that you have 800 watts of solar - I have over a 1000watts, and these are what we are reliant on to keep our batteries charged. Our BMS will not provide full solar power to our batteries when they reach 80% - they really taper off at that point and will reach 90 or 95% if we are lucky. Note taper, not drop off. This is courtesy of the BMS which is non-standard. To reach 100% .........? Nope.
I wonder if you are confused and actually believe that 90% is full? Or that your monitor is programmed to read that 90% is full? Or whether your battery monitoring is seeing a 'surface' voltage that if left to rest for 15-20 minutes would show a truer battery state? It is possible that as your solar system is providing a higher voltage that is concealing the true battery state. As such, whilst they are providing a higher voltage during daylight your system could be fooled into thinking it is in a higher state of charge than it really is. Once the sun goes down your voltage would then quickly drop to its true state. This would support the fact that you suggest you use 200a/h over night which is really significant. It makes me wonder how your batteries are ever able to be kept at better than 80% as when you add in your day time loads you will be using, daily, typically in excess of 400a/h. Im not sure how your 800 watts of solar manages that even with a bulk charge from your alternators each morning.
However, for us, also with significant loads, but not of your magnitude, we do not maintain a perpetual state of >80% charge. Our recharge includes 2x D400's which we usually release at night if required. They will often maintain our batteries over dark. My routine is to always check battery voltage first thing in the morning.

Back to subject matter: Regardless of our differing opinions, and the pedantics, I can't accept the wisdom of having a stand alone 125A battery supported by 30 watts of solar to operate a windlass. I repeat that this may be ok for 'normal' windlass operation but what happens when conditions change? I am not aware of any liveaboard that cruisers that have not, at some point, been required to re-anchor repeatedly. Typically this happens at the day end or on an overcast day. To be dependent upon a battery that cannot be provided with a substantial recharge power would leave me concerned.

This is not something to be recommended but is rather for the concience of the person concerned and maybe for those endorsing/encouraging it.

Originally Posted by StuM

It's apparently a disagreement about the meaning of "very difficult".
And a misunderstanding of what absorption and float modes really are.

Batteries don't suddenly "go into super slow absortion/float mode"

They initially go into absorption (sp) mode when they reach around 80%. This mode is constant voltage with current steadily falling as the SOC increases.

The charging rate doesn't suddenly become "super slow". It starts off at the same rate as Bulk charge, but steadily tapers down from that point as the current the batteries can accept goes down. Another 4-5 hours with enough Amps available is generally sufficient to bring them the rest of the way up to full SOC again.

And that's what the solar tends to give you. The nice thing is that as the sun goes down in the afternoon and the Watts from solar goes down, the required charging Amps goes down at a similar rate.


I have 1000Ah of AGM. That means that I can burn 200Ah with no input and still keep them above 80% SOC. I have 800W of solar plus alternators on two engines. Any one of those three can give me around 30-50 Amps by itself.

If I can start fully charged in the late afternoon, that 200Ah is generally enough to see me through the night.

So the way to keep above 80% most of the time is to hit the batteries with a heavy alternator charge first thing in the morning when they can take all the Amps you can throw at them and then let solar gradually put the rest of it back throughout the day.

[dlymn]

Go Stuie! Amped up again. I could listen to your 'clarifications for amphours and amphours

[barnakiel]

I think 'super slow' must be seen in a specific context.

E.g. We have a 100 Ah battery that is normally cycled only between 80% and 100%. At 80% the battery will still accept about 20A charge. At 90% about 10A. stc.

So, to us, only the last 5% is the super slow charging area.

I will try to excel a raw example later.

Let's not mix up what was super slow with an oversize alternator on a big diesel while others may be on solar panels and fuel cells that do change the state of the game.

b.

[barnakiel]

This is what I believe the required times might be (with some rounding):

20% to 10% - 45 minutes,
10% to 5% - 45 minutes,
5% to 2.5% - 45 minutes,
2.5% to 1.25% - 45 minutes,
1.25 to 0.75% - guess what another 45 minutes.

etc

So I cannot agree that once LA batteries hit 20% level they become super slow to charge. I could agree to maybe the last 5% being slow and the last 1% being very slow as we aim ad infinitum due to exponential nature of the formula.

For one can clearly get as close as 1% with just 3 hours of afternoon soon and a decent solar panel. You can alternatively use a wind or fuel cell generator at night.

If all you have is an alternator on your diesel aux ... sorry, it is 21 century here and the technology has overtaken you.

Cheers,
b.

[Bulawayo]

So now we get to the facts. My statements have been correct all along as we both knew. Then you try to belittle me further by stating 'its the 21st century here'. Really? I identified previously about using standard recharge regimes.....which was not acknowledged. The whole exercise was rather pointless, wasnt it? Your credibility is pretty low.
A bit below the belt, eh, attempting to ridicule others. You might be surprised to read that not everyone has access to your wonderful 21st technology. We met cruisers during the first Gulf War who were also totally dependent also on technology. It didnt help them when the GPS was switched off.
It still doesnt get away from the facts of the OP and the inherent problems that could occur as a result.

Originally Posted by barnakiel

This is what I believe the required times might be (with some rounding):

20% to 10% - 45 minutes,
10% to 5% - 45 minutes,
5% to 2.5% - 45 minutes,
2.5% to 1.25% - 45 minutes,
1.25 to 0.75% - guess what another 45 minutes.

etc

So I cannot agree that once LA batteries hit 20% level they become super slow to charge. I could agree to maybe the last 5% being slow and the last 1% being very slow as we aim ad infinitum due to exponential nature of the formula.

For one can clearly get as close as 1% with just 3 hours of afternoon soon and a decent solar panel. You can alternatively use a wind or fuel cell generator at night.

If all you have is an alternator on your diesel aux ... sorry, it is 21 century here and the technology has overtaken you.

Cheers,
b.

[barnakiel]

Originally Posted by Bulawayo

So now we get to the facts. My statements have been correct all along as we both knew. Then you try to belittle me further by stating 'its the 21st century here'. Really? I identified previously about using standard recharge regimes.....which was not acknowledged. The whole exercise was rather pointless, wasnt it? Your credibility is pretty low.
A bit below the belt, eh, attempting to ridicule others. You might be surprised to read that not everyone has access to your wonderful 21st technology. We met cruisers during the first Gulf War who were also totally dependent also on technology. It didnt help them when the GPS was switched off.
It still doesnt get away from the facts of the OP and the inherent problems that could occur as a result.

I am sorry.

I did not mean anything belittling nor below the belt. Please forgive and forget. Truly no ill will here at all.

I was trying to point at the fact that at 80% the charge rate does not get all that slow in absolute terms.

That's why I not just blahblahblah'ed verbally but also posted the curve (a homebrew curve, but I believe generally correct).

The OP said SOLAR and so I pointed at the fact that with solar charging, one can easily reach better than 95% soc easily, within one charge cycle.

I am TRULY SORRY what I wrote sounded uneducated. I did not mean to be rude nor offensive.

I should have read more in depth thru the posts above mine prior to my posting too.

I apologize to you and to all readers in this thread.

Best regards,
barnakiel

[Bulawayo]

Barnakiel, that is a very generous posting ..... & I retract any thing negative that I also said.
I might be from a third world country but I am first world educated, to a fairly reasonable standard - and still cannot understand why people believe that there is only one viable system on this planet. Many of us sail with boats outfitted last century and without the benefit of the latest technology. I do sometimes question technology though. I hired a Mercedes recently in Europe and it was a mission to programme the GPS and to reset the odometer or to change the radio station which required reading a very substantial manual. My old Landcruiser that I still own just requires a button to be pushed to reset the odometer whilst the radio is retuned by pushing a reset button or twisting the tuning dial. I can strip my outboard carburettor by torch whilst sitting in my dinghy. There is no chance of me doing that with the latest four stroke injected outboards.
As such, new tech is not always better for me, altho' when sat on the ICW and someone experiences an issue and can simply call up someone for tow I can see why they would think like this. My choice of cruising grounds is pretty far from 21st cntury tech. and we have to be self sufficient - kit must be self-fixable.
Not withstanding, if a 125ah battery is utilised by an windlass for repeated anchor retrieval it can easily be pulled down to below 50%. We also have a good probability of this occuring late in the day. A LA battery, we all know, does not like to be pulled below 50%. None the less, this does happen and the battery life is compromised as a result. For a 30watt solar arrangement to recharge this battery at around 2ah maybe for only for 4-5 hours at the best and reduced either side, then you are going to run out of daylight. You are going to be lucky to see 20ah going into the battery. As I said before, it shall 'normally' be ok. Its when the stuff hits the fan that you shall likely have issues. For someone sailing regularly, in unfamiliar waters, this is something that shall happen given time. I cannot ever promote or subscribe to something that has inherent risk unneccessarily when there is a perfectly good alternative.
i appreciated your post and the spirit in which it was sent. Thank you.

Originally Posted by barnakiel

I am sorry.

I did not mean anything belittling nor below the belt. Please forgive and forget. Truly no ill will here at all.

I was trying to point at the fact that at 80% the charge rate does not get all that slow in absolute terms.

That's why I not just blahblahblah'ed verbally but also posted the curve (a homebrew curve, but I believe generally correct).

The OP said SOLAR and so I pointed at the fact that with solar charging, one can easily reach better than 95% soc easily, within one charge cycle.

I am TRULY SORRY what I wrote sounded uneducated. I did not mean to be rude nor offensive.

I should have read more in depth thru the posts above mine prior to my posting too.

I apologize to you and to all readers in this thread.

Best regards,
barnakiel

[leftbrainstuff]

Originally Posted by Stonecutter36

" you generally shouldn't pull the boat using the windlass." Why??
I have a windlass that should pull me off a grounding. What is wrong with using it to pull me up to the anchor or even pulling UP a piece of reef ?

They aren't designed for a long duration full load duty cycle.

The wiring may also not be specced for continuous duty.

There is nothing stopping you using it as you suggest.




Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[barnakiel]

Originally Posted by Bulawayo

(...)

Not withstanding, if a 125ah battery is utilised by an windlass for repeated anchor retrieval it can easily be pulled down to below 50%. We also have a good probability of this occuring late in the day. A LA battery, we all know, does not like to be pulled below 50%. None the less, this does happen and the battery life is compromised as a result. For a 30watt solar arrangement to recharge this battery at around 2ah maybe for only for 4-5 hours at the best and reduced either side, then you are going to run out of daylight.

(...)

Agreed.

This is a big battery (good news) and a small panel (bad news). I have found the relationship should be the opposite for solar charging to be effective. In our boat, we have 150W of sun wired onto a 100Ah battery.

Where we might have a challenge, is where some owners may use the anchor winch to pull the boat towards the anchor, against the wind and other factors. But this is not good practice. One will normally power or sail towards the anchor and use the winch only to lift an anchor that is already free. I know many owners do not do it like this BUT I think this would be the thing to worship with a 'solar powered' anchor winch.

Cheers,
b.

[ramblinrod]

Originally Posted by mitiempo

I agree with Rod.

In addition you only buy the cables once. The battery needs both maintenance and periodic replacement.

Plus one more thing to consider regarding a dedicated windlass battery = lost storage space.

When considering a dedicated windlass battery, I ask the owner, "Is your house bank as large as it should be for how you use the boat?"

Most times, the answer is, "No, I wish I had a larger house bank." So I generally recommend, "OK, lets add the house bank capacity you need for all of your electrical appliances, and run the windlass off that."

For a windlass AND bow thruster, a dedicated battery forward is almost forgone conclusion.

[Bulawayo]

Yup ......we are on the same page.
Best wishes.

Originally Posted by barnakiel

Agreed.

This is a big battery (good news) and a small panel (bad news). I have found the relationship should be the opposite for solar charging to be effective. In our boat, we have 150W of sun wired onto a 100Ah battery.

Where we might have a challenge, is where some owners may use the anchor winch to pull the boat towards the anchor, against the wind and other factors. But this is not good practice. One will normally power or sail towards the anchor and use the winch only to lift an anchor that is already free. I know many owners do not do it like this BUT I think this would be the thing to worship with a 'solar powered' anchor winch.

Cheers,
b.