Batteries......again.

[Appleyard]

Just got back from 5 weeks in Greece. We left the boat in Cleopatra yard on October 10 last year.I had charged the batteries up using a heavy car type charger,disconnected them completely and cleaned the tops.On arrival back on May 9 this year the voltage readings had dropped by .1 and .13 volts on the two batteries respectively. I reconnected them and each easily had the guts to turn the engine over .So after 7 monthsof inaction without any attention whatsoever, the batteries were as good as when we left. Reading all the stuff about battery maintenance on this forum and elsewhere,much of it written by very knowlegeable people,I wonder if too much is made about keeping them topped up over long periods,eg using solar panels,wind gennys or float chargers.Is the answer not just to buy good quality batteries in the first place ,charge them up and leave well alone?

 

[MacW]

Well said.
years ago,before solar panels were available on the leisure market, and there were few wind generators, AC Delco used to advertise their ( lead acid ) batteries in PBO with the promise that they would start your engine after 18 MONTHS lying idle.
I sometimes wonder if all this newfangled electrickery is really only doing is floating a surface charge on the batteries whilst slowly cooking them................

 

[VicMallows]

Sounds quite normal to me if the batteries were in good condition when you left. It's when they're on the way out that you have to keep them on trickle charge all the time /forums/images/graemlins/grin.gif

Vic

 

[Appleyard]

Thanks for your reply Pete,interestingly enough both are AC Delco's!!!

 

[VicS]

I believe the modern low maintenance batteries were really developed to hold their chage for long periods in the days when car makers churned out thousands of cars to be stored in compounds, farm fields or whatever until they were sold!

The trouble begins though when they get a bit past their prime and don't in fact hold their charge for quite so long but are still able to give good service if recharged periodically

 

[pandos]

I have to agree.

I bought my first boat 3 years ago it had 2 110 amp truck batteries in it. I left them charged at the end of the first season,

I replaced them with new super dupper marine batteries for the second season and removed the batteries to the corner of the yard.

A month ago I jumpstarted a car with one of them with no charging since September 2004. I charged it and have just fitted it as the cranking battery in my new boat. Turns the engine endlessly even while I worked on the diesel pump and lines etc.

I have 2 new plastimo marine batteries in reserve just in case it fails at the wrong time but I am confident that it will not let me down.

tony.

 

[Rick]

Times have changed - years ago, before solar and wind gens etc, we didn't have lots of high demand electrical loads on our boats, so batteries lasted well - we also used little charge, and then replaced it slowly. Today, we have fridges, electronics, anchor winches, all sorts of other loads and then we replenish the charge used flat out via high current alternators. The weak link is now definitely the battery. Remeber how long your car battery used to last when you had a lucas generator, 35w main beams, and the biggest internal load was the fan for the heater - my Camry air con probably draws more power than my Austin A35 could ever produce .....

 

[Ships_Cat]

I think there are two things to consider (talking lead/acid here).

The first is that after charging to float at 13 point whatever volts the surplus charge will leak away relatively quickly and the battery settle at its fully charged 12 point whatever volts. If they are quality deep cycle batteries you do the batteries a service by keeping them at the float charge voltage as this allows continuing conversion of the sulphation in the thick plates of these batteries from the last discharge (this will not be all converted by a typical charge cycle from a battery charger and will become permanent if left). Solar panels are able to do that (and they need not be very big).

It is always worthwhile to charge at the bulk 14 point whatever volt rate too, for the same reason of getting depth of conversion, and a typical automotive type battery charger will not do that.

The other thing is that many boats have low discharges on board when the batteries are apparantly isolated. An obvious one is a bilge alarm which may be wired directly back to the batteries but a less obvious example to many is a marine ssb which also may be wired back to the batteries and so not isolated. These radios often have a small current drain due to the Xtal heater which is maintained on even when the radio is "Off". That is not insignificant over time - for example the Icom M802's I have measured seem to draw around 100mA even when "Off", which doesn't sound much but taking your 5 week example amounts to 84 AHrs which is quite a hit on any moderate sized battery bank which if left at that level of discharge will have its life charge/discharge cycles shortened. Another example might be the supply to the memory backup of a automotive type player if wired to the batteries.

I personally would always recommend that one way or another quality (eg expensive) deepcycle batteries (such as Trojan, etc) should be maintained at their float charge voltage. If the batteries are just automotive types or cheap (lightweight normally) leisure or whatever description batteries which will probably only have a shortish life anyway then the cost of maintaining a float charge is probably not worth it (we have just got 10 years out of a set of Trojans, which while expensive batteries, actually make them the cheapest choice for our use).

John

 

[William_H]

I tend to agree with you re. solar chargers. They are expensive and inconveneient to fit. Although many see a huge solar array as some sort of greeny badge of office. If I had shore power available or an inboard engine with alternaor I would not have solar on my boat. Yes batteries can last quite well. My only problem with your statement is in reference to "good quality batteries" How do you know just cos you pay more that you get good quality. I am afraid I am cheap is best man and put the difference towards the replacement. olewill

 

[Ships_Cat]

Hi olewill

Am also not a fan of big solar arrays. 60 watts worth is easily enuff for maintenance charging of well over 500AHr of batteries, but you need a hell of alot more area to make any useful contribution to anything other than a very energy frugal boat. And on an energy frugal boat one can charge the batteries economically in a matter of a very short time with shorepower or short engine run unless the batteries are large and (unwisely) deeply cycled so staying at partly discharged state for days or longer.

Regarding deep cycle battery quality the build of some batteries is well respected but as you say, like anything price does not necessarily mean quality. However, I have yet to come across high quality deep cycle batteries that are cheap.

Expensive batteries are obviously not the choice for boats with light electrical loads (either in terms of AHrs drawn or in terms of infrequent use) and if light enuff in a smaller boat a small auto battery is probably the cheapest choice even taking into account cost over whole of the battery's life as long as only shallowly discharged.

Again, all the above assuming lead/acid.

John

 

[Appleyard]

The batteries were not "Apparently isolated" they were in fact completely disconnected ie I unbolted the terminal clamps and removed the leads completely,so there were no bilge pumps,radios,or any other drains whatsoever still connected.I then dried the tops of the batteries and they were left like that for the following 7 months,with no attention whatsoever.They had retained almost their full charge when we returned.

 

[Ships_Cat]

Sorry, but I was responding to your general query in your post wondering why people kept them topped up.

In the specific case where batteries are left stored (ie no cables connected) then the 0.1 to 0.13 voltage drop you quote (assuming you measured it open circuit) represents around 20% discharge of the battery. All the comments I made regarding depth of charge with respect to the plates all still hold (probably more so as you are talking of partial discharge for a long period of 7 months) and ignoring that and not maintaining float charge will shorten the life of the batteries. Maybe only of concern if good quality (expensive) batteries are installed from which long life would normally be expected (so quite the opposite of your claim that quality batteries are best left uncharged).

However, I sense that you had already made your mind up that such was unecessary before you first posted? Which is just fine, of course - they are your batteries.

John

 

[Guest]

The main reason that "modern" boats need small solar cells to maintain their batteries is due to the battery monitor equipment they use.

Mine for example takes 28mA. For 6 months that is 122AH

Leave them disconnected after fully charging and they always seem fine for me.

As for solar panels in the UK, I was getting 1/6 maximum output at 7.00 in the evening last week! UK summers are wonderful; the nights are less than 2 watches long.