Batteries... ahhhhhhh

[Jennifer McM]

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Edited September 10, 2016 by bag 'o' bones

[Jennifer McM]

It's now become clear that the batteries are not holding their 'magic', after about 3 hours of cruising yesterday afternoon, they are now down to under 10V this morning. We've only had 2 laptops and a mobile phone charging up, and of course a bit of lighting last night.

 

We're under our 3rd week of being the owners of our boat - and now we think it's the end of the line for our bank of 4 x 110A batteries.

 

Yesterday we had 3 solar panels fitted, so we've got 'great expectations' despite the 'orrible' weather on the Coventry this morning. In just 4 hours of having them fitted, they managed to generate 90W into the batteries yesterday.

 

We were advised to replace them with 3 x higher capacity batteries rather than 4 lower ones, reason being; the batteries will fair better being worked harder. We've been recommended: Victron Energy 12v 130Ah AGM Deep Cycle Batteries, and have been quoted £225 per battery.

 

We're reading battery design life is 7-10 years (so in the greater scheme of things......)

 

Wondering what the knowledgeable members of this forum think? Thanks for any feedback.

Sorry guys, I've managed to post this 3 times..... internet kept dropping out so thought it hadn't 'gone'! Have reported my fault to the moderators.

[keith.]

I am fairly new myself but the consensus is to get cheapish flooded lead acid batteries and a decent monitoring system and learn the black art of battery care/charging before buying expensive batteries.

 

It is more about how you use them than what they are.

 

I know a motorhome owner who rarely camps without an electric hookup. To the extent that the original battery is still fitted after 10 years and the first gas bottle has just been changed over. On the other hand stories abound on this forum of wrecking a set of batteries in under 3 months.

 

I would make sure that the old batteries were given a good charging before declaring them dead.

Edited September 10, 2016 by keith.

[Jennifer McM]

Thank you Keith for your reply. Have downloaded what looks like a good app to keep track of battery information (VictronConnect) so we've no excuse for not knowing what's going on with the batteries.

 

I've read that some are upgrading their domestic battery banks by have more batteries, not less.... we just want to make sure, it's a big investment to get wrong.

Edited September 10, 2016 by bag 'o' bones
so the thread makes sense following merge

[keith.]

 

I've read that some are upgrading their domestic battery banks by have more batteries, not less.... we just want to make sure, it's a big investment to get wrong.

 

The trick is to know how many ah you are using between charges. Then bearing in mind that the best balance between initial cost, time to charge and life of battery is to size your bank so that between charges you using 20% - 50% capacity, you can determine your battery bank size.

[Tony Brooks]

At the moment you seem to be concentrating on only one side of the problem. If the voltage was down to 10V then one can reasonably deduce that either the battery bank size is too small for your demands - what you appear to believe - or, far more likely in my view that you have never provided sufficient charge. It is likely that you have already ruined your present batteries by undercharging so they now only have a fraction of their original capacity.

 

I also note that you seem very keen on Victron information. Please temper what you read from them that they have an interest in selling you somewhat expensive equipment.

 

You need to do a power/energy audit, then do the charging calculations. You will find an example in the mechanical maintenance noes on my website. Once you work through that you will have a rough idea if the problem is caused by insufficient battery capacity, insufficient charging, or if you need to reduce your consumption. You can prevaricate as much as you like about this but the fact remains that until you get your head round how the battery capacity, charging and consumption inter-relate you risk just ruining batteries.

 

Please either do the calculations or post a list of every item of electrical equipment you use together with their consumption & how long you run them each day plus details of your charging equipment.

 

You obliviously have a voltmeter so I hope its a reasonably accurate digital one. That will tell you when you should start charging. A similar ammeter will tell you when to stop charging. However you need to grasp the relationship between battery open circuit voltage and state of charge plus what tail current means.

Edited September 10, 2016 by Tony Brooks

[Alan de Enfield]

The batteries may be have a 'design life' of 7-10 years but on a boat you can totally destroy then within 7-10 weeks.

 

If this is your first boat, I would suggest that you stick with 4x 110aH 'cheapo' batteries (£60 each), if you do not destroy them after a couple of years, then by all means go and spend 'silly money' on some new batteries, but in the meantime you will have proven that you didn't really need to spend £700 on batteries.

 

If you do kill the 'cheapo' batteries you would have done the same with the £700 batteries so you have saved £450 and learned something - you need to improve you battery management skills.

[by'eck]

Given your batteries are 110 amp hour capacity they are probably commonly used leisure ones. On a boat they can last as little as six months if abused, but likely 4 to 5 years max, by which time their capacity will be less than half original. Yours are completely shot.

 

Given above I would suggest as a new boat owner you replace with the same economically priced leisure ones, before going for anything more exotic and expensive which could still be ruined in short order by a poor charge regime. Expect to pay £65-75 per battery for leisure.

 

BTW the 90 watts you quoted relates to instantaneous power. If your solar could deliver that for an hour you would have put 90 watt hours of energy into the batteries, minus modest charge losses. 90 watt hours would approximately equate to a more meaningful 7 amp hours, not a lot when you consider your total original capacity.

[Dave Payne]

^agreed.

 

This is what I have done.

[Jrtm]

Why do you need agm batterys? Do you have a fully electronic charging and monitoring system on the boat? Along with constant stop start where you constant power requirements are high but short busts of power.

 

If you have engine and solar pannels and only use a start battery you just need normal leasure batterys agm wouldnt even be needed on the start up battery.

 

Would be a waist of extra money getting agm wont aid you at all.

Standard leasure 115amp batterys would be fine

4x115ah + 7ah per hour charge should give you plenty if you run all led lights led tvs and charge things like phones and laptops during the day or when boating youll hardly use any power from the batterys

[mross]

What kind of charger do you have? No point buying expensive batteries if they are not going to get a full charge. It would also be good to know what alternator(s) you have and their output in amps. The energy put in by the solar is measured in Watt-hours (Wh) or Amp-hours (Ah). 90W may be the power of the solar panels at any one moment

[Geo]

I would suggest that you buy cheap wet lead acids at £60/70. If you can get them to last you 4 years keeping the water levels up, charging them fully as needed they will last four years at least. Then buy some crown, or one of the other expensive brands and they will last in the order of 8 years.

 

If you really want batteries that will last almost for ever buy NiFe a bank the size you apparently need will cost about £2000 and last probably the life of the boat.

[Robbo]

AGM's are still only liesure batteries and therefore should only be used for liesure use. They only have a few benefits over standard wet cell liesure batteries but not really double the cost worth. Low self discharge is one benefit.

 

If your a non liesure user and use the batteries to a high DoD on a regular occasion then traction batteries are the king (give or take lithium if you can afford!).

Edited September 10, 2016 by Robbo

[Phil.]

As others have said buy the cheaper version of batteries until you know what you are doing and have a decent charging regime in place. With the money you save, buy a smart gauge battery monitor if you don't have one already.

[MtB]

 

We were advised to replace them with 3 x higher capacity batteries rather than 4 lower ones, reason being; the batteries will fair better being worked harder.

 

 

This especially, sounds like bobbins to me. Batteries get damaged by being discharged excessively so fitting a smaller capacity bank of more expensive batteries seems daft to me.

 

OTOH I don't really understand the features and advantages AGM batteries, or why they might be a better choice for you.

With my cynical hat on, the reason you've been advised to buy three batteries at £225 each as opposed to four cheapos at £80 each is that with the former, the profit margin for the supplier is probably about £60 on each battery, and about £20 on each for the latter.

[WotEver]

Jennifer, there is lots of info in the previous answers you've received but let me try to conceptualise it for you. The one thing to bear in mind with a boat is that you are your own 'power station' - any power you use must then be generated (plus around 20% to account for losses) before you can use any more.

 

Bear in mind that 10V isn't flat - it's dead. 11.5V is way lower than you'd ever want to take the batteries, 12.2V should really be the minimum. So...

 

1. You need to calculate how much power you use each day as per Tony B's post.

 

2. You need to calculate how you will replace that. Either by cruising, solar (although that's going to get steadily worse now until next spring), or generator/shoreline with battery charger.

 

You HAVE to reconcile 1 & 2 before you move on to 3...

 

3. Select a bank of batteries of approximately 3 x the capacity that you calculated in 1.

 

The folk at Onboard Energy are very nice but they do have a vested interest in selling you Victron kit which is very good but expensive. Your scenario sounds to me like you might benefit from a SmartGauge although right now, once you've calculated 1 above, an ammeter would probably be of most use, and we can tell you how to use it once you have it fitted.

 

Hope that helps,

Tony

[Robbo]

If your looking to spend around £675 then look at what other options get you. First of is the recommended Trojan T105's and similar batteries.

 

6 T105's at around 675ah bank size

Cycle # to 50% -1600

 

3 Victron AGM's - 390ah bank size

Cycle # to 50% - 600

 

So the Trojans have more capacity and more than double the cycles!

[bottle]

Lots of good advice above, let me just comment on this

 

 

We've been recommended: Victron Energy 12v 130Ah AGM Deep Cycle Batteries, and have been quoted £225 per battery.

 

do not go down this line, I speak from experience.

 

I managed to wreck a set in two and a half years and I looked after them with kid gloves.

Monitoring and always fully charging, when possible, with charging system specifically for AGM's which is different to wet lead acid.

 

The only proviso I have a fully electric live aboard and use the batteries excessively.

 

The previous bog standard sealed wet lead acids lasted two and a half years, so figure.

 

Now have open wet lead acid deep cycle, with charging system adjusted to suit.

 

Still monitoring but even more detailed now, we shall see.

Edited September 10, 2016 by bottle

[Arthur Brown]

The design life of the most expensive batteries may be ten years BUT that's under extremely accurate charging conditions, which never happen outside a UPS battery room. A battery on a boat will last up to two years regardless of brand or price

 

Start now to monitor your electricity use and generation. A three hour generator period is probably no use whatever, find a place where you can charge the existing batteries for 12 - 24 hours. Watch the current from the charger log it and when it starts to fall into the 3A region maybe the batteries are as charged as they will ever be. Then you can determine the state of the batteries.

 

The advice to replace them with big batteries is good assuming that they still fit the battery cage. Learning to use a volt meter and ammeter will help a lot in determining the state of your battery, a Smartgauge will help more but will cost more. However remember that you can only remove about 80% of the energy that you charge into your battery.

 

Almost all of the short life failures of batteries are due to failure to charge them adequately.

[bottle]

Another way of looking at batteries,

 

It is not so much the type of battery that is important it is the way you treat them.

 

You can wreck cheap or expensive batteries in days let alone years.

 

The important thing to know how much amp.hrs you use and the capability of putting them back.

 

Lets say your usage is 100 amp.hrs per day then the battery bank will need to be twice that plus say 10%.

 

So a battery bank of 220 amp.hrs. This is the minimum and covers the not letting batteries go below 50% SOC

 

This is not gospel just an example the bank could be larger but cost of batteries and space to put them comes into it.

 

Also what you use will need to be replaced plus say 10% because of charging losses.

[Paul C]

As above, really. Buy cheap replacement leisure batteries for now, if you have extra cash to put towards the boat then invest in decent, proper battery monitoring. Cheap batteries can be made to last a long time if properly managed.

[MtB]

The important thing to know how much amp.hrs you use and the capability of putting them back.

 

 

This is the bit that I used to fail to get. Battery charging is not linear. The closer to fully charged you get them, the slower they charge.

 

The analogy to me is its like filling a lock. An initial rush followed by the last 20% to full taking 50% of the time.

 

So your three hours of charging will get them back up to 80%, but that final 20% will take a further 3 hours. Probably more once you get your ammeter and can see for certain when they are fully charged (by observing the tail current).

[Arthur Brown]

Assuming that you can cruise to charge batteries, you will probably need to cruise for 12 to 24 hours to completely charge flat batteries, and that's not 12 hours on tick over revs.

 

First charge the batteries you have to FULL, then determine how good they are, then buy new batteries. Remember that solar charging figures will go down for the next four months as the light level goes down. You need to sort out a winter charge regime urgently. Getting a winter mooring with shoreline power would be a fantastic option and probably cheaper that generating your own power.

[mross]

I hope OP tells us what charger she has.

[OldGoat]

Time to return to basics -

 

How do you charge the batteries at present.

You've mentioned a 90W solar panel - but that's small and will in effect be much smaller in the winter months.

Sooo -

What engine / alternator do you have?

MRoss mentioned charger - are you marina based?