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New batteries needed, AGM or FLA?


p6rob

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It's coming time to replace my 3 110Ah sealed lead acid batteries. Like the previous two sets, they've lasted two years. Whereas I don't mind accepting the relatively short lifespan, if possible I'd like to increase the time between purchases.

At the moment, I have two solar panels which I think are 300watt each and a 60amp Outback MMPT controller. The solar provides charge from about March til about mid October. The rest of the time, I run the engine to charge the batteries with a 70amp alternator, usually a couple of hours every few days and a longer 6-8 hour charge one weekend day.

I'm a fairly light user of electric and although I live on the boat, don't get to spend that much time awake on it. The lights are all LED, there is an inverter and TV, which rarely get used and when they are, the engine is usually running. The water, shower and bilge pumps are probably the biggest, regularly used current draws.

Although not an insurmountable issue, accessing the batteries to check acid levels is hard enough to be easily 'forgotten' if it's wet and dark. So if they need checking more than monthly, I'd probably not do it enough.

I'm wondering if changing to AGM or maintainable FLA batteries would suit and would the alternator need changing for AGM?

 

Thanks for any advice.

Rob

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You need to charge your batteries to pretty much full at least every other day,mother wise they will get sulphated in short order and last only 2 years.

A couple of hours every other day then a long charge at weekends is a recipe for the disaster that is 2 year battery life.

If your working life means this is the best you can do, it’s probably best to be resigned to buying new Batteries every couple of years, and don’t risk buying expensive.

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9 minutes ago, Richard10002 said:

You need to charge your batteries to pretty much full at least every other day,mother wise they will get sulphated in short order and last only 2 years.

A couple of hours every other day then a long charge at weekends is a recipe for the disaster that is 2 year battery life.

If your working life means this is the best you can do, it’s probably best to be resigned to buying new Batteries every couple of years, and don’t risk buying expensive.

Is it a disaster to change batteries every couple of years? That will be say £300 every two years, or 40 odd pence a day. Running an engine to fully charge every other day will cost several times that. I would stick with what your doing.

Ian.

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14 minutes ago, Richard10002 said:

You need to charge your batteries to pretty much full at least every other day,mother wise they will get sulphated in short order and last only 2 years.

A couple of hours every other day then a long charge at weekends is a recipe for the disaster that is 2 year battery life.

If your working life means this is the best you can do, it’s probably best to be resigned to buying new Batteries every couple of years, and don’t risk buying expensive.

In fairness two years is pretty good if the boat is used like mine.  The age of the batteries is only part of the equasion. I get two or just over two years from mine which is 700 cycles which for cheapos is fair enough for me. Question is will he get four years if the batteries cost twice as much? 

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I have just bought 8 x 130 ah lithium ion batteries cost £2800, they are secondhand but have done 15 cycles each they are for my bathtub [electric powered broads cruiser]. My current boat has full tractions on it, which are for one bank are 12 years plus and are still ok, I am good with looking after my batteries, so expensive batteries for me are good value, if you aint they represent expensive scrap! With your regime I would fit quality non maint leisure's and hope for 3 years between changes

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9 minutes ago, mrsmelly said:

In fairness two years is pretty good if the boat is used like mine.  The age of the batteries is only part of the equasion. I get two or just over two years from mine which is 700 cycles which for cheapos is fair enough for me. Question is will he get four years if the batteries cost twice as much? 

Yep, that's the right question.  If the answer is "yes, he will get 4 years" he still shouldn't do it in my view!  Maybe if 5 years is on the cards it starts to be worth a punt, but at break even longevity it just ain't worth it.  This is because it isn't really any more difficult to quickly ruin a set of more expensive batteries due to an imperfect charging routine.  If that happens after 18 months he'll be much more out of pocket than with the cheapos.

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12 hours ago, p6rob said:

I'm a fairly light user of electric and although I live on the boat, don't get to spend that much time awake on it. The lights are all LED, there is an inverter and TV, which rarely get used and when they are, the engine is usually running. The water, shower and bilge pumps are probably the biggest, regularly used current draws.

Are you sinking?

With your light consumption perhaps you should consider downsizing to 2 batteries as that would give the solar a better chance to charge them properly, might increase lifespan and cuts a third of the cost.

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Thanks for all the advice and to answer the questions:

 

The alternator charges at 14.2 Volts through a split charge relay. The starter battery is on the permanently connected side of the relay. I intend to change this at some point.

The current batteries are Super Batt Silver 9000 basically cheap off ebay. The previous ones were whatever Midland Chandlers sell.

No not sinking at the moment but the cruiser stern does let a lot of rainwater into the bilge and each side of the engine bearers has a separate automatic pump.

I have been wondering about reducing the number of batteries. Solar keeps up very well for about 8 or 9 months but it usually takes me a week or two to adapt lifestyle when the nights start drawing in, I suspect it's this that does the most damage to the batteries.

Do AGM batteries survive poor maintenance better then FLA? The reason I ask is that my Smart Car, with an AGM battery, stood for three years and I was pleasantly surprised when it turned over and started without needing the battery charged.

 

Rob

 

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3 hours ago, forsberg said:

Are you sinking?

With your light consumption perhaps you should consider downsizing to 2 batteries as that would give the solar a better chance to charge them properly, might increase lifespan and cuts a third of the cost.

I wouldnt downsize the batteries to 2. They will discharge deeper in the winter and therefore potentially suffer more sulphation on your charging regime. More batteries will be better especially during the spring autumn when on some days you can get more amp hrs in (as you have larger capacity). My strategy is to go for double the batteries. Rather than 3*110s I have 6*110's which means my overnight DoD is half so cycles are double (or more than double), and it doesnt take any longer to charge the last 5% as my tail current is double that of a bank half the size.

Having said all that, 2 years is not bad for the OPs position. I'll be very happy to get 4 years out of our 'double' sized bank although we are a heavier user. I think if I was the OP, unless he can improve his winter charging, I would do the same again with cheap LA's.

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1 hour ago, p6rob said:

Thanks for all the advice and to answer the questions:

 

The alternator charges at 14.2 Volts through a split charge relay. The starter battery is on the permanently connected side of the relay. I intend to change this at some point.

The current batteries are Super Batt Silver 9000 basically cheap off ebay. The previous ones were whatever Midland Chandlers sell.

No not sinking at the moment but the cruiser stern does let a lot of rainwater into the bilge and each side of the engine bearers has a separate automatic pump.

I have been wondering about reducing the number of batteries. Solar keeps up very well for about 8 or 9 months but it usually takes me a week or two to adapt lifestyle when the nights start drawing in, I suspect it's this that does the most damage to the batteries.

Do AGM batteries survive poor maintenance better then FLA? The reason I ask is that my Smart Car, with an AGM battery, stood for three years and I was pleasantly surprised when it turned over and started without needing the battery charged.

 

Rob

 

AGMs withstand more abuse, I've left ours disconnected at the master switch for 5 months on one occasion and they only discharged by a few %. 

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5 hours ago, Halsey said:

I'm a big fan of Varta Hobby 28's a little bit more but after 4 sets all lasting 5 years a piece 2 in my ownership and 2 in the previous owner who ran a commercial vehicle/battery garage worth a look - pellion tyres/batteries on the web 

We had Varta proffesionals last time and they did last slightly longer then our previous set. They lasted about four years.

Our current set of Bisons have been on for 12 months now. They were a little sluggish when first fitted but seem to have gotten a bit better over time. 

In theory the Bison's have a better spec then the previous Varta's and should last longer but I guess only time will tell.

If I were the OP I would opt for el cheapos again. If you kill them it isn't the end of the world and you can pick up replacements anywhere.

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14.2 is a tad low but addressing that is costly so not worth the bother with cheap batteries, unless the split charge relay takes a long time to to engage or cycles I would not bother to swap priority.

No lead batteries survive poor maintance, and there is no straight answer if one battery type is better or not as it also depends on metals used. However AGM are supposed to charge quicker which might help your situation if you continue with your current charging regime and not take the AGM's faster charge as an excuse to charge even less time.

Your charging regime seems to lack a bit reading between the lines but it also saves on engine hours and that's not bad either cost wise.

As Dr Bob points out more batteries might also make sense as while you have a light consumption you dont charge fully daily then again the solar should pick up some of the slack, however if double the bank only gives double the lifetime there would be no gain. It's very possible that your curent setup is as good as it gets, paying a bit more attention to your depth of disharge and trail current might be all that is needed as well as taking care of the solar, is the solar connected in series or parallell and do you factor that in?

A table similar to this might shed some light:ChargeTable.JPG.44ec3bf310e170d3dcf6a67c5364a029.JPG

The influence of solar might make it tricky to get correct readings.

 

 

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10 minutes ago, forsberg said:

14.2 is a tad low but addressing that is costly so not worth the bother with cheap batteries, unless the split charge relay takes a long time to to engage or cycles I would not bother to swap priority.

No lead batteries survive poor maintance, and there is no straight answer if one battery type is better or not as it also depends on metals used. However AGM are supposed to charge quicker which might help your situation if you continue with your current charging regime and not take the AGM's faster charge as an excuse to charge even less time.

Your charging regime seems to lack a bit reading between the lines but it also saves on engine hours and that's not bad either cost wise.

As Dr Bob points out more batteries might also make sense as while you have a light consumption you dont charge fully daily then again the solar should pick up some of the slack, however if double the bank only gives double the lifetime there would be no gain. It's very possible that your curent setup is as good as it gets, paying a bit more attention to your depth of disharge and trail current might be all that is needed as well as taking care of the solar, is the solar connected in series or parallell and do you factor that in?

A table similar to this might shed some light:ChargeTable.JPG.44ec3bf310e170d3dcf6a67c5364a029.JPG

The influence of solar might make it tricky to get correct readings.

 

 

Am I misunderstanding, or, are you suggesting discharging your batteries by 80%/90%/100%, or do you mean 'state of charge' (ie 90% state of charge = 10% Depth of Discharge)

I would not expect any battery to last very long with 90%-100% depth of discharge.

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1 hour ago, Alan de Enfield said:

Am I misunderstanding, or, are you suggesting discharging your batteries by 80%/90%/100%, or do you mean 'state of charge' (ie 90% state of charge = 10% Depth of Discharge)

I would not expect any battery to last very long with 90%-100% depth of discharge.

I'm not suggesting anything besides doing an audit , but yes it should have been "State of Charge" with those percentages. I did say "similar" as I got no clue as to what the OP can check.

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This topic is of interest to me.

2 years of battery life with light use sounds worryingly short. To the OP: at what point do you change your batteries?

No one has mentioned equalisation charging, which given the stationary nature of batteries on a boat might extend battery life, if not from desuplferisation, from reducing stratification of electrolyte.

I had thought that solar could still provide a useful output during the winter months?

Personally I would go for cheap batteries, its easy to damage batteries from unintended discharges, which will damage expensive batteries just as well as cheap. Battery technology is pretty mature, and I am yet to be convinced of the various buzzwords associated with 'new' technologies provide any meaningful extension to battery life.

BICBW

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5 minutes ago, Mikexx said:

I had thought that solar could still provide a useful output during the winter months?

Do you have any 'real-life' experience to support that statement.

It seems that for the majority of folks on here, the Winter output tends to be about 5%-10% of the Summer time output, ie, pretty much useless.

For the odd one or two that report no difference between Summer & Winter outputs I'd suggest a visit to Specsavers.

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15 minutes ago, Alan de Enfield said:

Do you have any 'real-life' experience to support that statement.

It seems that for the majority of folks on here, the Winter output tends to be about 5%-10% of the Summer time output, ie, pretty much useless.

For the odd one or two that report no difference between Summer & Winter outputs I'd suggest a visit to Specsavers.

 

Just from articles I have read, an example:

  http://www.pbo.co.uk/expert-advice/solar-panels-everything-you-need-to-know-24455

Suggests that output in December is a nominal 12% of that available in summer in terms of energy kWhr. And I believe from a total of 200W panels. The OP has 600W.

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27 minutes ago, Mikexx said:

 

Just from articles I have read, an example:

  http://www.pbo.co.uk/expert-advice/solar-panels-everything-you-need-to-know-24455

Suggests that output in December is a nominal 12% of that available in summer in terms of energy kWhr. And I believe from a total of 200W panels. The OP has 600W.

Interesting article - and you did notice the author was talking about his boat cruising in Greece ?

The angle of the sun at around 51 degrees North (central UK) is very different.

Even in Greece, in the Summer, the author was only achieving about 60% of the theoretical output (so 100w becomes 60w)

(If you do the sums the unavoidable losses on a new panel operating at 65°C are typically 40%. Our example 100W panel is therefore only putting out 60W, and that’s only for a few hours.)
 

Now take that to 'Winter in Greece' where the author is getting only 12% of his Summer time output (so the 60w now becomes 7w)

 

Remember that UK latitudes will produce approx. 50% output of those in Greece - see the graphs in the article - (so the 7w now becomes 3.5w)

(showing about 3kwh/month output in Jan in Cardiff, whilst in Greece  in Jan the same panels produce 10kwh/month) 

 

All figures are approximate and 'rounded' but the principle is accurate.

What is rated as a 100w panel (under perfect, equatorial conditions in mid-summer) becomes a 3.5w panel in Central England in the Winter.

 

 

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14 minutes ago, Alan de Enfield said:

Interesting article - and you did notice the author was talking about his boat cruising in Greece ?

Yes, but he also talked of his boat in Cardiff, have a look a a graph titled "Cardiff annual energy for flat panel (blue) tilted but fixed (red) and fully tracking (black)".

I have no idea where you got your figures of 100W vs 3.5W, but the figures in Cardiff show an energy difference of 8:1, and with less daylight implies at noon the solar output at midday might be closer to 4:1

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1 hour ago, Mikexx said:

I had thought that solar could still provide a useful output during the winter months?

 

My 560W of solar will typically charge at 0.1A for about three hours in the middle of the day around Dec/Jan (into a 24v battery bank). Do you regard that as 'useful'?

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