Batteries... ahhhhhhh

[Tony Brooks]

Could well be a Freudian slip

[WotEver]

Could well be a Freudian slip

That's what I figured.

[Jennifer McM]

Sorry for not replying sooner, just got back into mooring after 3 rainy hours cruising.

 

We hope to be CCs, but are popping in/out a marina for September until we get sorted.

 

We found there's no battery charger with the victron inverter, and we've been advised we don't need to upgrade the Victron inverter as we now have 3x130W solar panels. There is a "Sterling Alternator-to-battery-charger" - "power management with power from two alternators" (says on the packet), (no charging from the shoreline).

 

We've been charging the batteries via the engine. The first week while bringing the boat down to our 'patch' we were cruising 7 hours a day, by morning the batteries were showing 10v!

 

Therefore the batteries do not seem to be holding charge - at this moment (after 3 hours cruising) there're showing 12.7v, the only power draw has been a Shoreline fridge freezer (12v).

 

I will be answering each question, or it maybe John (husband) .... so please bare with us for a while.

 

So grateful for your replies, thank you very much for your help.

[WotEver]

I suspect that you bought a boat with shot batteries as you originally suspected yourself.

 

However, all of the other questions - particularly the audit - need to be addressed in order to get you moving forward successfully.

 

Tony

 

Just one point - the solar will be next to useless from November to February and of only marginal use from October to March.

[Paul C]

Do you liveaboard? Work? Or more precisely, "how many hours are you on the boat between the hours of 8am-8pm"?

[Jennifer McM]

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.

 

 

Thank you for your reply Tony, John's got his head firmly into your website (he might be there for a while )

 

Electric survey - presently

 

• normal use of water pumps, discharge and running water (we've a Thetford cassette toilet)
• two laptops on constant charge (240v), they also charge via usb a *mobile phone, a myfi dongle, and a *tablet (*tho' not everyday) - laptops are 'asleep' for about 20-22 hours a day
• undercounter fridge/freezer running all the time 12v Shoreline
• LED lights throughout, probably 4 or so are on for 4 hours in the evening
• have not used any hairdryers, food processors, hoover, toasters
• cooking is via gas
• tv hasn't been switched on (still trying to sort the system)

I am looking to have 240v undercounter fridge, and 240v undercounter freezer both A++ rated in the future

 

Can't think of any other electrics we're using, except of course the electrical management system.

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.

 

Brilliant advice! Thank you Alan

[Jennifer McM]

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.

 

This is the route I'm sure is right - thanks for your help

[Jennifer McM]

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

Thank you Tony, I wondered how you knew about 'Onboard Energy' - but then I saw where you're based. You must have seen us? It's a lovely marina.

 

Totally agree with you, we can't afford NOT to be cynical.

[OldGoat]

Ah - now we have more info. In the first post you omitted the fridge (naughty!). A fridge takes a considerable amount of power. In the future you're planning TWO refrigeration devices, so that's a bigger load.

Laptops take a fair bit of power when on and charging.

I'm not a lover of CSs' Alternator to battery charger as they are basically inefficient - and that's important if you want to minimise your charging time. It was designed for those who didn't want to go to the trouble of modifying their alternator(s) - so there was a market need. I have misgivings about running two alternators through one A to BC.

 

As you want to develop a sensible strategy for your power needs - and I assume you will not be cruising all the time - so methinks a larger than 'normal' battery bank (together with - say - an 100 amp alternator, or larger) should be included in your plans. You need to look at all components in the mix and not just the batteries.

 

I wont go further - 'cos there's bound to be many and various opposite views.

[Jennifer McM]

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

 

 

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.

 

Thanks for sharing, very interesting!

[Tony Brooks]

I agree that it sounds as if the batteries are faulty so for now replace them with ordinary leisure batteries so you can see how it goes. Do NOT spend money on expensive batteries until you are certain that you can monitor them and look after them properly.

 

For CCing I think you need to minimise your electrify consumption so think about forgetting the freezer. Also see if you can get 12V supplies for the computers and ONLY charge them while the engine is running. Work off their batteries when stationary.

 

Whatever gizmos you have on the charging system it will still take many, many hours to fully charge the batteries so you need monitoring equipment to see when to start and stop charging. I too have reservations abut the A to B device, especially as it is more difficult to make it inoperative for fault finding purposes. I suspect it was fitted because the previous owner never fully charged the batteries and could not be bothered to lean about the problem - they believed the marketing blurb.

 

I have 3 x 110Ah leisure batteries, a single 70 amp alternator, 60 watt solar, 12V fridge, 12V laptop supply, 12V phone charger and a 100 watt inverter that is only used to charge items that do not have a 12 supply. Plus pumps and lights. My batteries are over 4 years old and still working well enough. Apart from the freezer and the need to run an inverter 24/7 for the fridge I suspect that your system is OK apart from the batteries.

[Joe the plumber]

I thought our batteries might be on the way out today as despite having fully charged them (at home) last week, and having cruised for three hours yesterday afternoon, when running our inverter to power the fridge (only) overnight, its digital display seemed to be occasionally dipping below 12V whenever the compressor kicked in.

 

However, while cruising back to base today, my wife found the freezer compartment door inside the top of the fridge had been slightly open all the time we were on board, so the poor old fridge had been running far more than it needed to, hence the greater battery drain.

[Robbo]

 

If they are correctly manage and looked after. If not either type could be gone in a year or so

The Trojans will be able to handle the abuse better and can be revitalised with equlisation charges and water replenished. Don't really have that option with AGM's.

[Geo]

I tend to agree with Tony.

 

Forget the freezer if you can, if not go for a 12V version. As a rule of thumb any thing run via the inverter costs about 10% to 15% extra battery power used.

 

I think I would add a decent Sterling or similar charger for those days when you do have a shoreline available.

 

Your biggest job is going to be putting the charge back into the batteries. Batteries do not make electricity they only store it. Think about them as say a bucket of water. Once the water is used the bucket has to be refilled. Unfortunately refilling a battery is not as simple as turning on the tap full as the bucket will take the water as fast as you can pour it in. A battery has a limit as to how much charge it will take at any time which is related to how discharged it is (DoD depth of discharge express a A/hs) If a 110A/h battery DoD is 50% then 55A/h of its available charge has been used. If the battery is put on charge using a charger (main, alternator solar panels etc) it will take about 55A, as its state of charge rises the amount of charge it will fall so that say at DoD of say 20% the battery will short of its full capacity by 22A/h and by that poiint in the charge it will only take about 22A and so it goes on getting slower and slower. It is generally accepted that a battery is fully charged when the rate at which it will take has dropped to 1% of the batteries capacity in Amps and that has not fallen for 1 hour. So for a 110A/h that would be 1.1A being delivered by the charger and it had remain at that level for 1 hour.

 

There is another term you will come across State Of Charge again like DoD this is a percentage base of the batteries total capacity except in reverse. Thus fully charged SoC is 100% and half charged SoC is 50%

 

SoC DoD

Fully charged 100% 0%

3/4 charged 75% 25%

1/2 Charged 50% 50%

1/4 charged 25% 75%

 

Thus I would suggest you need an accurate way to read the current going into the battery when charging to know when you have got to the 1% point for that a good ammeter say a BMV 700 or similar.

 

You also need something to tell you the amount of charge that has been used from the battery and the easiest I know is a Smartgauge. Unfortunately the Smartgauge is not that accurate at measuring charging particularly when there are solar panels in the equation.

[Geo]

The Trojans will be able to handle the abuse better and can be revitalised with equlisation charges and water replenished. Don't really have that option with AGM's.

 

I was not thinking or taking about AGMs. On a boats sealed batteries are in my mind always a problem,easy to sell to the non-technical but very difficult to manage.

 

I would suggest that no matter what lead acid battery is consistently undercharged over the period of a year the chance of recovery from the suphation etc is not high. Yes over a short period, a week or maybe even a month any wet lead acid can be recovered to a certain extent by using equalisation.

[Geo]

A further thought. If you have room and the money it might help to install a good diesel generator say 3 or 4kW. The cost would be 4 to £5000.

 

I really do not think using suit case petrol generators are a good thing, the petrol is not available on the cut, is dangerous in a boat, and is very expensive compared to diesel at non-propulsion rates cira 65p a litre.

 

Ed fingers and brain

Edited September 10, 2016 by Geo

[Arthur Brown]

As a live aboard with fridge, you need to consider the charging system. Clearly solar is good in summer but in winter it's better to have either hookup or generator "mains" with a big clever battery charger, probably 40a plus with some clever charge profile selected to match the batteries. The more solar that you can have the more of the summer you will live without burning diesel for generation. January's solar harvest is likely only 10% of July's solar harvest.

[bag 'o' bones]

How many reports did you have?

3 or 4

 

rather have too many reports than none at all.

Edited September 11, 2016 by bag 'o' bones