Another battery question

[pessimist]

I believe our batteries to have ~50% of their original capacity. At the moment this is ample for our daily needs topped up by solar alone (so long as the sun shines). The question - do they just degrade slowly from this point or does their capacity just fall off a cliff?

 

[peter gibbs]

My experience is no cliff edge. But if one cell fails the output will not exceed about 10.5v at which level quite a lot of gear will not work reliably.

I believe our batteries to have ~50% of their original capacity. At the moment this is ample for our daily needs topped up by solar alone (so long as the sun shines). The question - do they just degrade slowly from this point or does their capacity just fall off a cliff?

 

[pessimist]

Thanks, exactly what I wanted to hear.

 

[sailaboutvic]

What are the AH ? 50% not much , remember you can only really use 50% so if say your batteries where 100ah and you lost 50% that don't leave you much at all , probably it's your panels that saving you turning stuff on and they working .

 

[pessimist]

What are the AH ? 50% not much , remember you can only really use 50% so if say your batteries where 100ah and you lost 50% that don't leave you much at all , probably it's your panels that saving you turning stuff on and they working .

The batteries are nominally 400Ah, so around 200Ah capacity rema ining - 100Ah available for use. As you say solar takes care of our needs during the day and we use 20-25Ah overnight. Batteries usually 100% by around 1500hr measured by Smartgauge. Any engine running is just a bonus.

 

[sailaboutvic]

Can I ask if our managing on 100Ah with the help of panels
Why shure a big bank.
We Are full time liveaboard ( should I say where till march this year)
We ran all sorts of stuff like mico wave , kettle, hot water heater,the list goes on and on ,
We ran a 3k Inverter.
We had 400 ah for some years till we change to lithium 400ah , we hardly touch the lithium say (100ah) before they where fully charge .
We could sit in a anchorage for a week with over cast sky and never got pass 70% .
Just saying , if your a long weekend / holiday sailor you probably could say some money and weight by reducing the bank.
For now we back to LA 200 ah and just one panel 150w which we put out when we at anchor,
We back in northern Europe .
Just to add we not using things like ele kettle mico and we finding we managing .
We do have a small Inverter.
We still liveaboard but probably park up in Nov and move on land for the winter.

 

[Poey50]

The batteries are nominally 400Ah, so around 200Ah capacity rema ining - 100Ah available for use. As you say solar takes care of our needs during the day and we use 20-25Ah overnight. Batteries usually 100% by around 1500hr measured by Smartgauge. Any engine running is just a bonus.

A common benchmark for batteries being at the end of their useful lives is 80% of the original capacity, although I'm sure that plenty of boaters go below this. The main thing, if you don't want to change, is not to overestimate your capacity so as not to get caught out. The Smartguage does over-estimate capacity % while charging, it is more accurate on discharge so you will probably get the most realistic figure early in the morning before your solar comes on stream.

 

[pessimist]

Can I ask if our managing on 100Ah with the help of panels
Why shure a big bank.
We Are full time liveaboard ( should I say where till march this year)
We ran all sorts of stuff like mico wave , kettle, hot water heater,the list goes on and on ,
We ran a 3k Inverter.
We had 400 ah for some years till we change to lithium 400ah , we hardly touch the lithium say (100ah) before they where fully charge .
We could sit in a anchorage for a week with over cast sky and never got pass 70% .
Just saying , if your a long weekend / holiday sailor you probably could say some money and weight by reducing the bank.
For now we back to LA 200 ah and just one panel 150w which we put out when we at anchor,
We back in northern Europe .
Just to add we not using things like ele kettle mico and we finding we managing .
We do have a small Inverter.
We still liveaboard but probably park up in Nov and move on land for the winter.

We try to live on board during the summer. We're in southern U.K. We don't have microwave/kettle etc. But do have food processor (can't live without fresh bread?) I'm sure you're right and we could reduce our battery bank size but the extra gives us a nice warm feeling.
We've thought about lithium but can't really justify the costs or complexities of installation. Should have mentioned we have 320w of solar.

 

[pessimist]

A common benchmark for batteries being at the end of their useful lives is 80% of the original capacity, although I'm sure that plenty of boaters go below this. The main thing, if you don't want to change, is not to overestimate your capacity so as not to get caught out. The Smartguage does over-estimate capacity while charging, it is more accurate on discharge so you will probably get the most realistic figure early in the morning before your solar comes on stream.

Yes, I'd read about the 80% figure which is partially why I asked the original question. Any idea of the rationale behind the 80% figure?
I'm basing my estimate of remaining capacity on overnight consumption against early morning Smartgauge reading.

 

[Poey50]

Yes, I'd read about the 80% figure which is partially why I asked the original question. Any idea of the rationale behind the 80% figure?
I'm basing my estimate of remaining capacity on overnight consumption against early morning Smartgauge reading.

I've always assumed that, below 80%, the deterioration on each cycle accelerates so, although not a cliff edge, the ground tilts down progressively more steeply towards the sea. On the other hand it could be a big scam to sell more batteries. Battery manufacturers are notorious liars.

 

[sailaboutvic]

Fresh bread mmm where about are you anchored ? Haha
No food processor our 150w flex panel seen to keep our batteries up nicely. I'm not a fan of flex panel , but I'm finding moving it around help only having one panel.
My plain is to go back to lithium come winter when I have time and a base , there no doubts it's a game changer

 

[pessimist]

Fresh bread mmm where about are you anchored ? Haha
No food processor our 150w flex panel seen to keep our batteries up nicely. I'm not a fan of flex panel , but I'm finding moving it around help only having one panel.
My plain is to go back to lithium come winter when I have time and a base , there no doubts it's a game changer

what size lithium bank are you planning?

 

[sailaboutvic]

what size lithium bank are you planning?

We gone from a 42 foot boat with everything you can think of on board ( ar not a food processor) full time livaboard 9 month each year on our hook 3 in a marina.
We never hardly used shore power the few months we was in the marina.
To
36 foot cut down on stuff like water maker but plainning to have kettle and microwave and a smaller inverter maybe 1500k /2000k

There no way we are going to have the amount of solar we had (750w) ,
So for next year at less we stick with the flex we have and see how it goes.

I most likely go for 300Ah lithium, bank not because we need that much but because we won't have the solar to charge up quickly ,
We can probably get away with 200ah but the different in cost isn't that much .
I also brought a new 240ah LA batteries this year and I will incorporate that with the lithium,
Just got to work out best way of going so.
Remember you can use lithium to 90% dod at a pinch.
Our liveaboard days now we back in northern Europe will probably be 6 months and on land for the other 6 ,
May and Oct are going to be the problem months short days longer evening and over cast.
The great thing about lithium is the voltage don't drop like LA ,
I could be heating the hot water at the same time have the kettle on and voltage would stay 13.1/13.2v

 

[PaulRainbow]

Yes, I'd read about the 80% figure which is partially why I asked the original question. Any idea of the rationale behind the 80% figure?
I'm basing my estimate of remaining capacity on overnight consumption against early morning Smartgauge reading.

You need to make a proper calculation of battery capacity.

Fully charge the batteries.
Allow to rest.
Take a voltage reading at the batteries.
Apply a known load (car headlight bulb is a common thing).
Disconnect the load, allow the batteries to rest and take another voltage reading.

When the voltage reading is equal to 50% DOD you can work put the true capacity, hours x amps = ah

 

[pessimist]

You need to make a proper calculation of battery capacity.

Fully charge the batteries.
Allow to rest.
Take a voltage reading at the batteries.
Apply a known load (car headlight bulb is a common thing).
Disconnect the load, allow the batteries to rest and take another voltage reading.

When the voltage reading is equal to 50% DOD you can work put the true capacity, hours x amps = ah

Thanks for that, I understand the concept but it's a bit difficult whilst living on board. SWMO will not be impressed if I turn off her fridge. Am I likely to be a million miles off with the procedure described in the earlier post - Charge the batteries as far as I can without shore power. The solar charge returns full at around 1300 the Smartgauge at around 1500. The solar carries on doing it's thing until sundown. At around 2200 I initialise the amp counter and take a reading from the Smartgauge. At around 0700 I repeat the two readings and calculate remaining battery capacity. I think it's as close as I can get without going to a marina with shore power and temporarily moving off the boat?

 

[PaulRainbow]

Thanks for that, I understand the concept but it's a bit difficult whilst living on board. SWMO will not be impressed if I turn off her fridge. Am I likely to be a million miles off with the procedure described in the earlier post - Charge the batteries as far as I can without shore power. The solar charge returns full at around 1300 the Smartgauge at around 1500. The solar carries on doing it's thing until sundown. At around 2200 I initialise the amp counter and take a reading from the Smartgauge. At around 0700 I repeat the two readings and calculate remaining battery capacity. I think it's as close as I can get without going to a marina with shore power and temporarily moving off the boat?

You can do one battery at a time. Charge it, disconnect and follow the procedure above.

 

[pessimist]

You can do one battery at a time. Charge it, disconnect and follow the procedure above.

Yep, that would work thanks. Any ideas about the original question? Cliff edge or not?

 

[PaulRainbow]

Yep, that would work thanks. Any ideas about the original question? Cliff edge or not?

Don't think it'll be a cliff edge, more like a steepening curve.

 

[KompetentKrew]

Thanks for that, I understand the concept but it's a bit difficult whilst living on board. SWMO will not be impressed if I turn off her fridge.

You can do the test over 24 hours - the insulation in the fridge will keep the contents cold enough. Turn it up (colder) for a few hours before, put a container of water in next to the evaporator and freeze it if you like. (Assuming you're on shore power).

 

[geem]

Fresh bread mmm where about are you anchored ? Haha
No food processor our 150w flex panel seen to keep our batteries up nicely. I'm not a fan of flex panel , but I'm finding moving it around help only having one panel.
My plain is to go back to lithium come winter when I have time and a base , there no doubts it's a game changer

Vic, I keep hearing that lithium is a game changer. This only seems to be a game changer if you are not well set up for lead batteries in the first place. We have 4 T105s, 720W of solar, towed turbine/ wind turbine, batteries never go below 80% full. We use solar to make hot water, run the ice machine, food processor, sewing machine, spinner for washing. We don't use large electrical use items. We have gas cooking. Changing to lithium for us would not be a game changer.
If you had our set up I doubt it would be a game changer for you either. I am working on a liquid cooled lithium build at the moment and still don't get the lithium is the best option stance. It suits certain applications but its heavily reliant on electronics. Lithium are not robust like lead