My boat battery failed after 2 and a half years. Thats pretty short time.Ive bought a new one, ok.  

Im not very knowledgable re batteries. Im thinking that, the battery doesnt like dropping to low charge. Ive got a anchor winch. It drains heaps of charge out of the battery. Then I run, mostly very short trips, to other places and back home. Possibly not enough to fully charge the battery. So, is it likely, the battery has dropped (and stayed) too low, and thats caused it to fail. 

With the new battery, when I raised the anchor, I saw (on my sonar voltage readout), the voltage dropped from about 12v to 10.7v; that seems pretty low?

Its a 1000w anchor winch, thats a high drain on the battery.

I will fully charge the battery (with a charger), and the see how much the voltage drops on anchor raising.

I would appreciate any words of wisdom on this.

am not likely to get caught out whilst out on the water since having a couple of backup features installed ... you are welcome to check them out once L2 is announced & restrictions are lowered.

Until it happens to us we seldom think about how vulnerable we are to battery failure particularly as modern day batteries seem to be much more prone to dying with little or no warning compared to their predecessors.

Of course firstly motor should be running before & during the winch being implemented as it is the major draw on any battery power, not that it will totally compensate but at least if motor is kept running you should be assured of being able to return to launching/retrieving place ... however am certain with your wealth  of experience you will be well aware of all that so will move on to other pitfalls that can be encountered due to a flat battery.

AlanL is the only person I know that has been able to rope start my 90hp Merc & that was when still on the trailer ... I certainly cannot manage to do so.

Next GPS/chart plotter possibly dead along with installed VHF, bilge pump & motor tilt ... mob ph could also be out of cover.

A small portable jump start may manage to start motor but have to take care cable clamps don't short out on anything particularly on ali hulls but seem to recall your new boat is FGlass.

On two occasions my main emergency backup system has come to the rescue ... would not be without it. 

A friend of mine has had the same/similar problems.

Seemed to have solved it with a permanent trickle charger when not using the boat.

Batteries lasting ages now.

Also as Bazza says, always advisable to have the motor running when raising the anchor. 

Oh my mistake - its 1000w anchor winch (not 100).

The battery voltage drops from 12v to 10.7v when the anchor winch is pulling up - not when starting the motor.

The previous battery, wouldnt start the motor - not a peep out of it. I took it to a garage and they load tested and said its stuffed.

When its charging, the voltage rises from 12v to 14v. 

But as Steps said, and you have deduced. The battery does not like being left half charged.

If you are only short running and potentially short charging , a trickle chargewhile the boat is stored is the answer. I leave all my boat and car batteries on trickle - for up to 6 mths. In the boat I am using right now a $100 battery (not even Marine) ), 3 yrs old - and still holding 12.8 V. It had been on trickle for 6 mths and had 12.8V after standing for a day or two. And still does. And cranks the engine no problem.

Also most batteries don't like rapid deep drain - but you can't avoid that with a winch. Is it Deep Cycle? Should be - for that job.

Alan

amperes:

RPM AMPERES (9A charger)

Idle 4.0

1000 8.0

(14 Ampere Stator) 2000 11.0

3000 13.0

4000 14.0

5000 14.0

RPM AMPERES

Idle 5.0

1000 10.0

16 Ampere Stator 2000 16.0

3000 17.0

4000 18.0

5000 18.0

The copy /paste got messed up. This is early Merc 2S around 90HP. Somewhere I have more recent specs but can't find right now. There are usually 3 charge options - small/med/large. But at 1000 rpm you should be charging around 10A. If not - you have a problem.

Alan

assume you have the now standard AGm chemistry battery - you, like many people are finding they dont seem to last as long as the old FLA batteries.

there are two issues you need to be aware of that are hurting your battery;

the anchor winch is drawing at least 80amps - possibly more if your wiring or terminals arent ideal - and whilst as mentioned above, the total A/hrs removed from the battery arent that many because of the short winching duration - the RATE of current is getting quite high - 80+ AMps is approaching double thew capacity of your batt and many manufacturers recommend against very high charge/discharge rates - often only 100% of capacity. this is where lithium is a big improvement - 500+% charge/discharge rates are no issue

secondly - AGM do not like being left at anything less than 'full voltage' for very long - best practice is to bring them up to full once a week. even with everything disconnected, they will often have a self discharge rate of 1 - 3% per month -  so they need regular attention.

basically you should consider getting a larger battery next time so your winch isnt asking too much from it in terms of 'rate of current draw' and get a decent multi-stage smart charger that can be left plugged in permanently when the boat is stored on the trailer between outings

According to the motor specs (2018 90hp 4 stroke) - the alternator output is 50amps. THat appears a lot higher than the 2 stroke amps mentioned. 

One thing Im bothered by. THere doesnt appear to be a way of measuring the % charged of the battery. If there was, I would know whether the battery needs charging - and put the charger on it. Has anyone figured a way of measuring this? 

Just put a voltmeter across your battery terminals 12 Volts =flat 12.5 volts = Half charge   12.8 volts = Good fully charged battery.

Do this test when battery is at rest and at least 24 hours after charging cause charging pushes voltage up (14V )and takes about a day or so to settle down... 

The winch draws 83 amps. 

Anchor retrieval max rate is 41m/min. 

Anchor drop rate is 45m/min. (not free fall)

I havent measured the exact time the winch operates - next time Im out I will keep a record of this.

I have calculated roughly how much power should be used to drop and retrieve anchor - for my maximum anchoring, say 3 times at 25m depth (with twice the depth out). Its about 7.8AH.

Charging at 35Amps, 7.8AH would take 17.8mins to recharge. 

I would always run for longer than 17.8 mins (at high speed) coming back in - so, theoretically, the battery should have always been fully charged when returned to the ramp.

Whether the old battery failed because it was left not fully charged, or there was something wrong with it, I will never know. Interestingly, manufacturers warranty appears to be max 2 years ONLY! THats pathetic.

But, maybe things dont always work according to plan.

So, I will buy a Battery Comfort Indicator to ascertain when the battery needs charging; and a Ctek MXS 5.0 charger to charge it up fully. 

Can anyone comment on how this performs, or if any other battery charger would be better. 

THanks for all the points raised.

The actual amps going into the battery is a function of the level of charge of the battery (the internal resistance of the battery increases as its state of charge goes up).

If your battery is above about 85% State of Charge (SoC) then the amps it will accept to charge are way lower than the theoretical max output of your charging device and usually this drops to about 10% of the battery capacity at 90% charge and keeps dropping as the SoC increases, so you may only be charging at 5.2 amps once the battery reaches 90 %. Ie it will take hours of running to get those last amps replaced and the battery back to full charge.

So, the net effect is that it is practically impossible to recharge your battery to 100% unless you spend hours trolling. As you do multiple trips you gradually decrease the level of chrge in a semi-cummulative manner. 

First trip starting at say, 100% you might end up at 92%. Next trip pulls the battery down further than the first because of the lower starting point and so is likely to end at lower recharge as well, say 90% etc etc etc as each trip gradually lowers the finishing SoC until the battery is more likely to fail, or you go trolling for 8 hours!

So, get a good battery charger, like the Ctek you mentioned and use it every time you return home. I don't personally like battery chargers left connected all the time as they can cause catastrophic damage if you get a dead short in the battery from a dead cell or thermal runaway in some AGM batteries. But a couple of days is all it needs each time.

Although a great idea these are not foolproof. I have a multistage charger and always recharge the battery before a trip out. I also fitted one of these battery level indicators to my battery as extra awareness on battery charge. 

However I'm now having to change my battery as although the indicator is still showing green, the battery voltage has dropped to 11.6V and the battery won't hold a charge as I think a cell has gone. 

your calculation on recharge time is flawed unfortunately

read SaltyC s post about declining acceptance rates as the battery comes up to full 

. I have a multistage charger and always recharge the battery before a trip out. I also fitted one of these battery level indicators to my battery as extra awareness on battery charge. 

However I'm now having to change my battery as although the indicator is still showing green, the battery voltage has dropped to 11.6V and the battery won't hold a charge as I think a cell has gone.


Chances are you may have , or have a voltage leak, maybe anything from salt/ dirt on the battery top between the terminals or in the isolation switch etc. A case of battery not being full charge when stored , and huge effect on battery life.

Quick test if battery going down/ cell dropping, and dont have a load tester...
Charge it up...leave 5 mins, note voltage. Then get an old incandescent car head lamp or something that pulls a lot current .. 12v pump, capstan/winch etc..run for 3 or 4 mins turn off wait couple minutes then check voltage... if good voltage will be same or very close to what was before loaded.

Chances are you may have , or have a voltage leak, maybe anything from salt/ dirt on the battery top between the terminals or in the isolation switch - battery is disconnected after each trip so no stray currents and no salt/dirt on connections

battery not being full charge when stored - I have always charged before a trip and I will now charge after each trip

I used to check the battery voltage occasionally with a volt meter but used the CTEK led battery monitor system as my routine go to for monitoring battery level - after this issue it is now in the rubbish bin.

I admit i havent for years, use winches stereo etc, up to 3 months gaps between use as well, never had a flat battery unless the isolator was left on and the stereo or something.

I even switch to the house battery for a start up occasionally to see if it will still do the job.

I bought a charger Ctek MXS 5.0 (5 amps max) - $159 from Repco.

My boat battery started at 12v - thats pretty low, although it us still enough to start the motor. 12v has been called "flat", but its not really, ive read that 12v is about 25% charged.. 

THe Ctek charger, went thru 4 stages (of analysis stuff), then at stage 5, charged at higher amps until 80% charged - took 16 hours. Then went on stage 6, charging at lower amps until fully charged (12.8v) - took 10 hours. 

Ive permanently installed the Ctek input cable onto the battery - its plug (to connect the charger) hangs outside the battery box, that easy to use.

So - took 26 hours in total. THats quite a long time, presumably the 5amps is relatively low. Fine if you have plenty of time, but not if you want to get out soon.

I thought of getting a Ctek Comfort Connect Indicator, that shows voltage in 3 bands (red <12v, needs charging (although its not totally flat), orange 12.4-12.65v, partially charged, green >12.65v fully charged. But as I have battery voltage shown on my FF screen, thats easy and more precise, so I probably wont use the comfort Indicator.

NOw Im happy to get out there - now Covid regs allow boating - but Ive got a doctors appointment - BUGG.R.

Oh, and Im  charging my ute battery, only 12v after sitting doing nothing for 10 weeks.

So - took 26 hours in total. THats quite a long time, presumably the 5amps is relatively low. Fine if you have plenty of time, but not if you want to get out soon.

 Modern agm batteries are NOT like our old school Pb car batteries... hence the new 'smart chargers'
They must be charged low and slow...
And as mentioned above.. must be tied down to reduce thumping.. they dont like that either.

At the end of the trip - 12.7v, thats about 100% charged.

Next day - 12.6v - interesting drop

then the voltage drops every day

after 5 days 12.5 about 90%

after 5 days 12.4 about 80%

etc - it appears to go down faster than I expect.

I have tried turning off the battery isolation switch, doesnt make any difference, so assume the drop is at the battery.

The battery is near new, 4 months old; and I cant see any dirt or salt buildup on the top of the battery.

So, I normally have the boat out of the water for around 14-21 days. The voltage should be about 12.4v when it goes for a spin and is recharged. I would prefer it to be fully charged.

So - two options - 

(a) I have a Ctek 5a charger, which if kept going all the time will keep the battery fully charged. 

(b) I could checking the voltage after each trip, and then leave it; and checking voltage around once a week, and fully charge before going fishing.

Im leaning towards option (a). Anyone see anything I should consider?

I imagine Covid lockdown has been bad for batteries, as they will have gone down too much and failed.

I would suggest there is still something draining amps at low but steady rate even with the battery isolation switch off.

If you can, get your hands on a mutimeter with an amp clamp and check the actual amps being discharged with the isolation switch off.

If you can't find one locally somewhere, give me a yell and let me know where you are (Whangaparaoa?) and I will drop in with mine when up there next.

If battery is discharging when disconnect find receipt and take back.

If battery is discharging when disconnect find receipt and take back.

Yep..
Dont rely on isolating switch.. mine 'broke ' a few months back.. so dismantled it while new on was coming..
They are sealed, but still get a vertigrease (think its called) build up inside ...
Combine that with something in the boat conducting and you have discharge.
Can use ammeter to find out where etc...
But end of the day, disconnect both terminals at the battery, way to go for 100% sure.

PS once the isolation switch was cleaned , seals plus silicone, back working  so have the new spare anyway.

Why are we all determanded that we plug them in to a trickle charger??Surely if under 24 months old they should hold charge unless damaged,isolator failure,engine not charging full capacity?

Mine is at least 4yrs and did have a issue with slight discharge hence why I went to above,Can sit for a month put on cheap warehouse charger and its full within 30 minutes.

This is sealed flooded battery.

What type of batteries are people having issues with??flood/gel particular brand??

Not sure if it's related but I've just installed a 100 Merc 4 Stroke. The installer was adamant that the battery needed to be upgraded as they are very sensitive to it. 

The manual (which covers the range from 75 - 115hp) states the min is 1000 Marine cranking amps (MCA), 800 cold cranking amps (CCA) or 65 amp hour (Ah)

The manual (which covers the range from 75 - 115hp) states the min is 1000 Marine cranking amps (MCA), 800 cold cranking amps (CCA) or 65 amp hour (Ah)

Yes. As described in several previous posts..

The manual spec is for bare engine... that doesnt put out much charge/current at low rpms.
Now throw in a current draw from a winch, or capstan plus gps and few other bits in pieces.. the engine alternator doesnt keep up with the load if battery is min. spec.
So engine running, high draw on say a winch, current/ voltage to things like seal alternator regulator, ignition CD! unit/ coils. They get hot and eventually intermittent loading like this over time they die.

usually the published output is the 'marketing dept' figures.

you should be looking for the 'hot rated' output values - which are usually 15-20% or so lower 

does the product manual declare whether the values are 'hot rated' - if it doesnt stipulate, they probably arent - usually the corrected for load output curves are only available directly from the alternator manufacturers

I thought my boat battery was losing charge between trips with the motor charging.

But - I was reading battery voltage on my sonar screen. I have now taken battery voltage with a multi-meter directly on the battery (terminals). It shows-

Battery voltage, With everything incl sonar off 12.82v

With sonar on 12.61v

With sonar on, voltage into sonar 12.5-12.6v

And, the battery voltage is NOT going down - over 5 days it stayed at 12.82v. This is the voltage after a trip charging the motor.

I dont know why the voltage on the sonar screen varies (when battery voltage is constant), but it doesnt matter.

It was an interesting discussion, and thank you for your input.