dead battery

[betty boop]

this time last year I got a new battery (not a cheap one either) and it's died, it start to fully discharge after 6 months, I've tried to keep it going but yesterday it wouldnt even output 9v despite a long charge and a long run on muffs to wake up the engine-

for my own sanity - could i have done anything to kill it off early? the only thing I can think of was during bad weather July/August when she wasnt used for 6- 8 weeks, surely that wouldnt have killed a new battery?

[Capn Jack]

I know that "cranking" batteries will only take a few discharges and not much below say 15% , it's called cycling. Having said that it doesn't make sense that yours has died that quickly.

How's your alternator, can you check to see if it's giving a charge, I'm not sure how you do it?

[Ed]

In my experience, (I have bit here as I used play around with car battery powered go-karts and stuff!) Car batteries whilst fragile are not as bad as people make out.

Batteries hate, ABSOLUTELY HATE sitting discharged. Their internal resistance will start to rise, which then means its even harder to charge them, and harder to draw current from them.

The only way I can get them to come alive again (if even possible) is to be really quite hard on charging them. I have a 40amp 3-16v power supply and I'll put the battery outside somewhere safe (risk of explosion) and charge them at 16v and keep an eye on the current and battery temp. Quite often on a dead battery, charge current will only be a few amps. This compares to a good but discharged battery would be at 40+amps @14.4volts (and 80% charged in only a few hours).

The only way to prevent this is to not allow the battery to go flat. Either remove it from the boat and keep it on an intelligent/smart charger in the winter to keep the battery voltage at around 13.2 volts and that will ensure a long life. The alternative on a boat where possible could be with a small 10-20w solar panel. That would be better than nothing anyway.

I did an article about charging systems for a car magazine recently. I don't know if it will help but here it is anyway: http://www.fusion-motorsport.co.uk/docs/charging.pdf

[Centaur]

Ed's quite right, letting a car battery discharge and leaving it that way will kill it very quickly.

The problem with boats is that they are often left for long periods and normal lead-acid batteries self discharge quite rapidly - even without other small loads such as bilge pumps, radios etc. Most boats only seem to have standard automotive batteries fitted (ignore labels saying 'heavy-duty' etc!) and they just won't tollerate even mild discharging. After 4-6 weeks they are really getting border-line for a top-up and, unless you have shore power etc, then the battery will start to take a hammering. Leave it for a few months and it's pretty much had it.

Shore power, solar panels etc or simply taking the battery home for regular re-charges will keep the problem at bay but an occasional quick run up the river for an hour or so will not. The alternator can put in a quick boost charge to a flat battery but the motor is unlikely to be run long enough to ever fully charge the battery. To properly top the battery up to full charge requires a very small current for several hours.

In my view, the best alternative is to get a more expensive (not necessarily bigger) battery that has very low self discharge - an AGM or gel type. Whilst more expensive initially, they are better value in the long run as they will last up to 10 years, whereas a lead-acid one is on borrowed time by 3 years - plus you don't know how long it was on the shelf or how well it was stored before you bought it. On my boat I have a twin battery installation. One is an AGM and one is a newer (car-type) lead-acid battery. The older AGM will hold its charge almost indefinitely and will readily turn the motor over even after a prolonged spell of inactivity. I wouldn't trust my holiday or afternoon on the water to the lead-acid one...

[Capn Jack]

Betty did you switch off the battery isolator?

Ed, I see you have a Draper Test Meter......

I have a question Ed, sorry to hijack for a second BB, but does it matter critically what the battery AH size is? I'm guessing the alternator output must come into play but for example if a manual suggests say an 80ah would a 90 be OK to use?

Also, would a 6amp charger fully charge a big battery for example say a 110ah or would you need something more butch to fully charge it?

[Ed]

Good post Centaur agree with all that really, except with care flooded batteries last /that/ bad if not allowed to go too deep.

Capn, The bulk charge of a battery is the first part of charging and accounts for about 80% of its capacity. Assuming you have a terminal voltage of 12v or under the battery is 100% dead. So 80% of 110 is 88amps. Assuming again that your battery charger is capable of maintaining 6 amps continuous during bulk charge that it will take around 14 hours to reach this point and about the same again/ish to charge to the final 20%.

If its a fairly basic charger (Halfords or something) then chances are if its rated at 6A it won't/can't maintain this.

As for battery size. You can use anything you want, will just take longer to charge. If you have 80, changing to 90, 110 or even 200 would be fine, but charge times would be a bit longer obviously. You can sometimes get problems if you go too small however, but that will never happen on a boat. The only other problem is perhaps if you have a really old unregulated charging system like my old Fletcher had, voltage can go too high and you just waste it as heat in the battery and again can shorten its life (hence why I had the nav lights on, during the IOW trip)

All alternator outputs are about 14.4 volts. Some alternators have external voltage sensing - Toyota used this a lot. Nissan don't seem to. (at lest for the stuff I work on) I quite like this as it takes the battery terminal voltage rather than the alternator output voltage, so can account for losses in the charging cables etc.

In any case things that kill a lead acid battery are - in order of what I consider most serious first (others may have other opinions on this):

Deep discharges - Greater than 60-80% For ANY period of time - this will be the cause of why some people get -2-3 years and others get 4-6 years from a battery, the ones who get 6 years may have medium discharges but not deep, and then left like that for months. I expect most boat batteries die due to this, leads to rapid decline.

Medium discharges - long periods of time (weeks/months or more), say you never fully charge the battery and the boat is never used enough to fully charge it. Battery may have enough cranking power but won't last that many years.
Never achieving full charge - plates will suffer with sulphation as above^
Lack of equalisation - Its necessary to equalise a battery occasionally. This is carried out by a controlled over charge. I suspect many people would find their batteries last much longer if they did this. I'd say this should be carried about at least twice a year on a boat battery, or any used for 'Leisure' applications. I suspect in reality this rarely if ever happens.
And finally
Frequent over charging - Batteries just don't like this - say broken alternator. Can dry the cells out leading to premature battery death.

I could write about this stuff for hours!!!

[Capn Jack]

That explains soooooo much, thank you.

What is a controlled over charge and how do we mere mortals do that?

Also some chargers are quite expensive, up to £200 -300. Would you recommend the highest ampage for your pocket? What about something around the £40-50 mark?

[Ed]

I don't actually have much first hand experience with 3td party chargers, but if I was to spec one, it would have to be 10-15A minimum continuous, 3 stage charger with battery equalisation option, and possibly battery temperature sensor/compensation.

Myself I use large power regulated supplies and keep an eye on it. The one I use on all my batteries is essentially the same as this: http://www.ebay.co.uk/itm/270965029644. I use them for so much I have two, one at home and one at workshop. You just need to know what your doing with it, or you risk pretty severe damage to you/battery/anything near you. I.e. no idiot protection built in. For a normal charge I'll set the voltage to 14.4 volts and leave it for 24H.

For a controlled overcharge/equalisation (really do have to be careful for this - I've seen batteries explode and its SEVERE) I'll set the voltage to 15.8-16v. Quite often nothing will happen for a while if its in a really bad way, you can tell as little current is drawn (3-6 amps).
Slowly activity will happen and current will hopefully begin to rise to 20+amps the more the better, if the battery is good and willing it may come right back and draw 40+ amps and the power supply will drop output voltage to avoid overload. If this happens the battery is still good, just very very discharged. If not after a time the current will begin to tail off but the battery is not necessarily beyond use, just not as good as it once was. From this point the battery will get warm even 30degC, which is fine, it encourages chemical reactions, the cells will also be gassing this is what you want, it stirs up the acid, helps remove sulphation on the plates and does good all round when done right ****BUT**** Extreme caution this is hydrogen/oxygen, do this outside only. I leave it like this for a couple of hours 'simmering', by this time the charge current should drop again to more normal levels (for this high voltage) as the battery accepts charge. In the end I drop voltage to about 14.4 then can compare with what I'd normally expect and leave it to complete charging over night @ 14.4 volts.

Complicated? possibly!!!!

I used to use a homebuilt power supply, but that had no regulation at all and so every charge was pretty much an equalisation charge. This was not great, although the battery(s) I did this on (used for camping) still lives @8+ years in a caravan, it did damage the capacity to probably around 60% of new.

[betty boop]

great advice - thanks guys-

Translating into non techy talk, I called Tayna batteries and they were very helpful, even though I didnt have a receipt or order date- they found my purchase and agreed on a 3 year g/tee replacement if needed. BUT also told me 90% of returns are due to charging failures, (bugger). Best we agreed on would be if I get a decent charger, use SB&R mags. battery saver device to de suplhar the cells if I've caused damage (or buy a charger with a de sulphar setting- correct me here if Im wrong please) - give the batt a 48hr deep charge and if she then falls below 12.7v - its call a courier time.

good to know the in's and out's but not so good that my solar Ebay charge is a pile of pants and prob so is the £9.99 car charge I use. it's going to be one of those spend £50 to save £80 gambles but I'll have a decent charger I guess.

Good service from Tanya though - come highly recommended.

[dpb101]

The depth gauge and gas detector were wired straight to the battery from new on my Bayliner and the battery would be to low to start the engine within a month. I rewired so nothing except the cd/radio memory lead was wired direct and it sorted the issue.
Could be worth checking to see if you have this going on?

[betty boop]

The depth gauge and gas detector were wired straight to the battery from new on my Bayliner and the battery would be to low to start the engine within a month. I rewired so nothing except the cd/radio memory lead was wired direct and it sorted the issue.
Could be worth checking to see if you have this going on?

good point- I did consider the radio being c##p and being faulty drain juice etc, but then found I'd taken the fuse out ages ago nothign else is wired direct pre isolater HOWEVER may be a coincidence but the battery troubles did start around the time I bought a dodgy fish finder off some dodgy power boat owner up north Im sure its just coincidence esp as it hasnt found any fish yet either

[betty boop]

Rats- I killed the battery - another expensive lesson learnt & new charger purchased- apparently batteries arent supposed to get hot when you charge them

[Ed]

They can do!! What did you do?

[Gazjen]

Rats- I killed the battery - another expensive lesson learnt & new charger purchased- apparently batteries arent supposed to get hot when you charge them

Not worth sending it back anyway to see if they will send you a new one?

Like Ed says I'm not sure how you could of killed it. Have you got a hydrometer to test the individual cells (presuming you can get into them)

[betty boop]

Im kind of at thier mercy of sending it back, its will cost £25 in charges and they say, with an amount of expertise, that the solar charger I had on over the winter wasnt enough to keep it 'topped up' so it dried out and de sulphared too much to be repaired. Add that to the original accident full de charge in the summer and the damage had gone too far. All I could achieve on my 7amp charger over 48+ hours was 11.5 A max and warm too touch.

was tempted with the you tube videos to drill it open - re fill and go again but I've got to trust it to work out at sea and if Im not confident - its not worth it.

Now I'll have a top notch de sulphar /constant on charger - so the new one is g/tee to last for 4 years - no questions.

if any one wants to have the almost new old one as a freebie to repair it - more than happy to stick i on a courier.