Short lifetime of leisure battery

[blackbeard]

This battery (70 Ah) seems, on my boat, to lose most of its capacity after about 2 years, even though I try to keep it charged and never run it flat. It's used as the domestic (ship's) battery and powers instruments, lights, radio, Waeco fridge, etc. The engine start battery seems to last a bit better.
Am I doing something wrong?
Or is it the hard life these batteries have?
Or is it just poor quality batteries?
Would fitting another battery, thus getting 140 Ah, help? or would it just double the replacement costs of domestic batteries?

 

[snooks]

35ah isn't a lot of battery capacity, well it would be ok if you hadn't mentioned the fridge.

I take it this is a normal lead acid battery?

If so and you want to keep your batteries a long time, it's best not to let them go below 50%, hence the 35ah, but also the faster you use the capacity the quicker they die [which is why your engine battery lasts for ever as it's only using a small amount of it's capacity every time]. If you buy two batteries the same now, instead of using 50% of one battery you'll effectively be using 25% of two so their life will be extended, assuming the same battery usage

How are you monitoring your battery level?

 

[Iain C]

I had to ditch a 110Ah after 2 yrs too. OK so the boat stayed in over the winter but I did run the engine every few weeks to top it up, and it does also have a forgen generator connected (waste of time though!)

However, the engine battery is at least 6 years old and for much of it's life would have been sat in storage and not charged for a few years. It cranks perfectly every time, although the engine starts easily. I will however install a voltmeter this winter to keep an eye on it (a BM1 looks after the domestic battery...I thought it was misreading as I was surprised how knackered my dom battery was after 2 yrs!)

 

[noelex]

Would fitting another battery, thus getting 140 Ah, help? /QUOTE]
Yes 140 Ahrs of a good deep cycle battery (golf cart flooded are the best bang for the buck) will give a better life and probably a cheaper per year cost.
Get a battery monitor.

You need to try an avoid letting them get down less than 50% other than very occasionally.

 

[blackbeard]

......How are you monitoring your battery level?

Volts (as shown on the GPS) with just GPS running. Generally 12.2 or more, if I measured at the battery with nothing running this would be about 12.3 or more, so it generally wouldn't have gone below about half charge.
The other level (acid) is correct and hasn't needed topping up.
Fridge is run only infrequently.
Generally haven't gone for long periods without engine running (or shore power and battery charger, careful not to over charge).

Mystery persists ...

 

[Paddingtonbear]

Perhaps a visit to the Smartgauge site might be in order? although I never have , a mine of correct information I am led to believe. I have not visited it because I try to keep things very simple and I have a little man who knows as much as Chris Gibson. The most important thing is to do a power audit.

 

[snooks]

Fully charged the resting batteries should be 12.7v, @75% 12.4v, @50% 12.2v, @25% 12v, 11.7v or less = knackered - This is at the battery, not using the GPS

But this only give a snapshot at any one time. In order to find out what's going on you need a battery monitor (something like a smartgauge will tell you the percentage left £160) If you don't want to go to that expence buy a digital volt meter.

Switch everything off for around 10 mins then get a volt metre on the battery terminals, your GPS is only measuring the voltage at it, not at the battery, you could loose tenths of a volt over a wire run, so it's not accurate.

 

[BabaYaga]

As I understand it, there are two major factors causing premature battery capacity loss:
1. Discharging under 50 percent, as already pointed out.
2. Not fully recharging the battery, something which can take many hours by alternator and even longer by shore power charger.
So could it be that you are too "careful not to over charge"? (Overcharging is normally not an issue with a modern charger).

 

[Cantata]

Hmmm. My service battery is 2x110Ah wet batts, cheap ones from a caravan shop (less than £50 each IIRC), one is 5yrs old and the other one is 6, and both still seem to be working well. Famous last words, perhaps...

 

[VicMallows]

, one is 5yrs old and the other one is 6, and both still seem to be working well. Famous last words, perhaps...

That's pretty much what I expect. At 5yrs the capacity has usually dropped off quite a bit, but a couple more useful years often possible. The problem is that at that stage they can completely die quite suddenly .... and maybe in an inconvenient place.

As has been said numerous times, keep them FULLY charged if you want them to last. I would hope to see 12.6v even on a 5yr old battery after it had been isolated on the boat for a month.

Vic

 

[noelex]

Volts (as shown on the GPS) with just GPS running. Generally 12.2 or more, if I measured at the battery with nothing running this would be about 12.3 or more, so it generally wouldn't have gone below about half charge.
The other level (acid) is correct and hasn't needed topping up.
Fridge is run only infrequently.
Generally haven't gone for long periods without engine running (or shore power and battery charger, careful not to over charge).

Mystery persists ...

I do not think any mystery persists

It is difficult to gauge the state of charge (SOC) from voltage alone. You need to take into account the charge history. A heavy discharge, or especially charge, can effect battery voltage for many hours.
The voltage shown on many GPS, or navigation instruments is inaccurate.
I have 3 GPS and speed/ wind instruments that read battery voltage. One reads +0.2v One reads -0.4V one reads -0.2V. These voltage differences, if they were acurate, would represent a big difference in the battery SOC.
Voltage drop in the wiring will also effect the readings.

The only way practical way for most people determine the SOC is to have a good quality battery monitor.

Calculating your expected , or measured, Ahrs usage is also very helpful.


The battery life you have experienced is typical of a reasonable quality battery discharged heavily to regularly say 20% or a poor quality battery discharged to 40%. Given your load, usage, and your small battery capacity you have this is within the discharge levels I would predict. So your battery life is within expectations.
If you want to improve it in future you need to make changes.

 

[Barry Jones]

If you systematically run the battery down below about half capacity before recharging, it will cause the battery to age prematurely.

How are you charging it ??

Extra battery capacity would help (providing you can recharge them properly).

This battery (70 Ah) seems, on my boat, to lose most of its capacity after about 2 years, even though I try to keep it charged and never run it flat. It's used as the domestic (ship's) battery and powers instruments, lights, radio, Waeco fridge, etc. The engine start battery seems to last a bit better.
Am I doing something wrong?
Or is it the hard life these batteries have?
Or is it just poor quality batteries?
Would fitting another battery, thus getting 140 Ah, help? or would it just double the replacement costs of domestic batteries?

 

[blackbeard]

Still a bit of a mystery AFAICS. MY GPS reading is actually not too inaccurate, I have checked with a digital voltmeter. Also I don't think I'm in the habit of heavily discharging the battery, although down to 40% could happen fairly often. So a poor quality battery could have something to do with it, I'm a natural tightwad and buy cheap batteries. Maybe that's a large part of the answer.

Thanks for all reples so far. I seem to be being persuaded to fit another battery (not necessarily easy in a 25' boat to find somewhere to put it but I have a couple of possible places in mind). There's probably a reason why 30' boats with roughly comparable electrics normally have two 100 Ah batteries plus an engine start battery ...

 

[john_morris_uk]

First of all you can get single batteries that are 110 Ah or even 125 Ah or so, so two of those would dramatically improve your battery capacity..

(At the risk of being called a smug g*t we have over 500 Ah of batteries on our boat and the batteries last for years and years....)

I also worry about comments like, "I run the engine every few weeks to charge the battery."

How long do you run it for? What sort of alternator and charge controller etc? How many amps is the thing actually putting into the battery?

I had a friend who used to think that motoring down the harbour for half an hour before he put out to sea would fully charge the battery on his boat. It does charge it - by a few amp-hours only.

We have a battery monitor with a smart charge controller on our alternator, but even with all these things in our favour it still takes HOURS to put 100 Amp hours back into our batteries. This is despite the alternator being forced to pump over 50 amps out for the first hour or so. Don't forget there are inefficiencies and heat loss in the lead acid charging cycle. You need to put in an additional 10-15% than what you take out. And trying to get the batteries back up to 100% is another waste of time. The last few % tales for ever and is pointless.

With respect, its no wonder your single 70Ah battery gives up the ghost after two years; especially if its a cheap one.

 

[snooks]

although down to 40% could happen fairly often. So a poor quality battery could have something to do with it, I'm a natural tightwad and buy cheap batteries. Maybe that's a large part of the answer.

If you think about it, you are taking your batteries down to -10% of their usable capacity fairly often, they aren't great batteries to begin with, and you're unsure how much you actually charge them (or even if your alternator is working?).

No mystery over here

Work out, with your volt meter on the battery terminals, how many amps everything on board is using individually, from that work out their use on an average day and how long you would run the engine for.

Remember to get the last 20% of charge into your battery requires you to run engine much much longer than it does to increase the charge from 40% to 60% as the absorption rate, or their willingness to accept charge, is greatly reduced.

 

[charles_reed]

Fully charged the resting batteries should be 12.7v, @75% 12.4v, @50% 12.2v, @25% 12v, 11.7v or less = knackered - This is at the battery, not using the GPS

But this only give a snapshot at any one time. In order to find out what's going on you need a battery monitor (something like a smartgauge will tell you the percentage left £160) If you don't want to go to that expence buy a digital volt meter.

Switch everything off for around 10 mins then get a volt metre on the battery terminals, your GPS is only measuring the voltage at it, not at the battery, you could loose tenths of a volt over a wire run, so it's not accurate.

the exhortations to get a battery monitor are, no doubt sincere, but fatuous.

He'd be able to buy another 210ah battery for the sum suggested - which would at least mitigate his problem rather than confirm it.

I have yet to discover, apart from the opportunity to demand more money, how a "LEISURE" battery varies from a normal battery in true detail (not what it's supposed to do).

Certainly 2 years out of a battery is low, I get more like 5-10 years, but then I live on the boat mostly, monitor the batteries most rigourously and have a total of 330ah (I'd have more if I could find anywhere else to fit them.

I eschew expensive batteries (though I recognise Trojan and Rolls as being high quality their premium price makes them cost-effective suicide), buy local, open wet-cell batteries at <€1/ah.

My guess is that a) the OP is leaving his domestic battery to stand in discharged state. b) he's working it too hard c) he's NEVER fully charging it - that will only happen if you use a switch-mode charger and allow about 96hrs of float charge after the preliminary bulk charge.
Whilst the fitting of a smart controller will help, they seldom if ever have enough time to fully charge batteries (unless you're motoring for hours in the Med) and my impression is that they knock the stuffing out of calcium-hardened plates. Why that should happen when a switch mode charger follows a very similar regime, I have yet to rationalise.

PS I do also have 320 watts of PV panel charging through MPPT controller.

 

[Barry Jones]

If you are only charging them a little and then back down to 40-50% SOC on your voltmeter, this will lead to premature sulphation and kill the battery.

Good battery maintenance necessitates that you find a way to get the battery up to 100% charge. Some use mains chargers on a shoreline and some use solar.

 

[vyv_cox]

I have yet to discover, apart from the opportunity to demand more money, how a "LEISURE" battery varies from a normal battery in true detail (not what it's supposed to do).

I understand that leisure batteries are taller, to accommodate a void beneath the plates into which sulphate debris can fall without shorting out the cell. Also that plates may be thinner and more plentiful to assist with recharge rate, at the expense of lower current output.

 

[r_h]

the exhortations to get a battery monitor are, no doubt sincere, but fatuous.

He'd be able to buy another 210ah battery for the sum suggested - which would at least mitigate his problem rather than confirm it.

Agreed - if the budget is limited (and power drain relatively modest) then spending on bigger batteries is almost certainly a better bet than expensive monitoring systems.

If lights represent a significant proportion of the power drain, then LED bulbs are also a good investment.

 

[snooks]

the exhortations to get a battery monitor are, no doubt sincere, but fatuous.

Obviously with the extra information gained since my quoted post, it's easy to come to that conclusion

At the time when I posted a battery monitor was, and still is the best solution to find out what is happening, whether it's economically viable is something for the OP to decide.

The OP obviously has either a usage or charging problem (or both) and while buying another bigger battery would reduce the depth discharge on that battery, if they are not charging it properly, the new battery will still lie in a state of semi charge which does it no good at all.