batteries change

[diverphil]

hi, i have a question about renewing batteries,at the moment from memory, the house batts are 2 x lead acid 140ah and are just about shot at, the engine start is also lead acid but is ok, the charger is an sbc quick 501 charger that can be set to gel or fla, the alterator i assume is standard vp,running through the origanal diode splitter thingy in (blue box) on the engine compartment back board.
would it be advisable/possible  to do a strait swap of the house batterys to agm of the same sise,and switch the charger to agm, or would it be better to re fit fla leisure instead.
the thing i cant decide is would agms be damaged by the alternator voltage when the engine is running, or if swiching the charger to agm, then the engine start would not be getting enough to top it up.
as ive spent a lot of this years budget getting the standing rigging renwed i could do without having to replace charging systems as well as the batteries.
the boats intended use is for days out of marina, weekends away and possibly a weeks trip at some point in the year, i also have a 1.6kw portable genny for if we were to use 240v for any reason.
has anyone done this ? and what was the outcome?
thanks
phil

[tiger79]

You can safely replace the house batteries with AGMs, there won't be any charging problems.  I doubt that your charger has an AGM setting, so leave it on the flooded lead acid setting.

[Yngmar]

Given your intended usage, AGMs are probably not worth the extra cost. Replacing the FLAs with another cheap set should serve you well. Don't bother with fancy brand names either, just pick a cheapish set with good reviews. A few years ago Numax was good value.

[diverphil]

thanks for replies, hope to get down to boat in a couple of weeks, so i will be able to see what fittings and dimensions the origanal ones are,
thanks
phil

[sunshine]

If you have the battery sensed alternator (thin yellow wire from house battery back to alternator), this setup charges at 14.3v. Any voltage drop at the diode (0.1v to 0.3v) is compensated for so that the battery gets 14.3v.

For the mains charger, its a bit more interesting. On flooded setting, it absorption charges at only 14.1v which feels a little low. On gel setting it absorption charges at 14.4v which is getting up towards the edge of max for a conventional flooded lead acid, although its only 0.1v more than the alternator gives, plus its a three stage charge cycle so drops down to float (13.5v or 13.8v) once fully charged. I suspect the standard setting is Bavaria having a safety margin so that less technical users don't boil their batteries. But if you know what's going on and can keep an eye on your batteries, you may feel comfortable at 14.4v.  I do this and definitely get the impression that i get a fuller charge into a depleted house bank, but I'm not on shore power very often. One thing to keep an eye on is actually the starter battery - it never gets used much but gets the same charging regime as the house battery, so it is more likely to get overcharged. Its your choice, but better to look beyond the flooded vs gel labels to the actual voltages.

[JEN-et-ROSS]

I agree with Yngmar.
AGMs are not really a good choice for a yacht. Yes they are better in all aspects but given the cost you can replace your cheap L/A Flooded batteries several times and still save money compared to AGMs.
 One point we discovered years ago, don't buy 'Low Maintenance' flooded batteries as topping them up is a pain in the neck. The cover for the cells will be hidden under a thick label and once you find it you will see that quite a bit of thought has gone into making it difficult to remove, but it can be done with some care without breaking it, though best avoided by simply buying even cheaper flooded batteries...(Low Maintenance' and 'Ordinary' Flooded batteries' are exactly the same battery just with different lids fitted at the end of the production line..)  .....Bill.

[symphony2]

Not sure that is true now. While "marine" AGMs such as Lifeline are still very expensive and only justified if you are a heavy user of 12v power, the newer automotive AGMs as used on cars with stop start are very competitive with good FLAs. The Exide 95AH AGMs as fitted to newer Bavarias are about £130 - 30% more than equivalent size FLAs but have over twice the total cycle times. They also take charge much faster and have low self discharge which is good for typical "weekend" type sailing. There are 5 in my boat, one for start, one for bow thruster and three in the service bank. They are now in their 6th year and I expect them to last at least 10 years. They hold their charge well over the winter - I only go on shorepower perhaps twice if they fall below 12.7v.

In my view a viable alternative and worth the extra expense if you intend keeping the boat to benefit from the longer life.

[tiger79]

I agree with Yngmar.
AGMs are not really a good choice for a yacht. Yes they are better in all aspects but given the cost you can replace your cheap L/A Flooded batteries several times and still save money compared to AGMs.
 

Not these days!  As symphony2 has said, AGMs are very competitively priced now and are an excellent choice for boats.  Like him, my boat has 5 AGM batteries, now 7 years old, and all working fine.

[JEN-et-ROSS]

I agree with Yngmar.
AGMs are not really a good choice for a yacht. Yes they are better in all aspects but given the cost you can replace your cheap L/A Flooded batteries several times and still save money compared to AGMs.
 

Not these days!  As symphony2 has said, AGMs are very competitively priced now and are an excellent choice for boats.  Like him, my boat has 5 AGM batteries, now 7 years old, and all working fine.

Interesting. The only thing I can add is we have x2, 115Ah cheapy Exide leisure house batteries that I've just replaced for @ £87.99 each.
A quick look back in our log says they were last replaced in winter 2013-14, so say also 7 years life. Having said that they are permanently being topped-up by a Rutland 913 and a 200W solar array so I guess if they were hammered more they wouldn't last as long....
But as you point out AGMs are getting more affordable.......Bill.

[symphony2]

Bit like yacht engines, batteries die from lack of attention. The key is the extent of discharge and then recharge and the total number of cycles. If you have a bank that is big enough such that you avoid heavy discharge in your normal pattern of use, plus an effective means of recharge then the batteries stand a chance of achieving their full life. Clearly running the engine for a reasonable time with an alternator and charging system that can maximise the amount going in plus solar and wind all help to keep the batteries as close to fully charged as possible. Assuming all these things are in place, the argument to me in favour of AGMs is that the increase in theoretical cycles over leisure batteries is now well in excess of the increase in cost. As you say, properly looked after FLAs do have a long life, so the decision whether to spend the extra does depend on your time horizons.

As a sort of aside I have a Morgan that I bought new in 2003. It has a Red Flash 28AH AGM battery and is still on the original. Although I use it all year round, inevitably weather means it sits in the garage for quite long periods and I plug in the trickle charger. Still on the original tyres, brake pads, exhaust as well, although the first two will probably be replaced this year. My regular car (2017) also has an AGM (stop/start system) and I hope to keep it another 10 years so will be interesting to see how long it lasts.

[diverphil]

ok I went for 2 x 140ah agm, for the better ability to keep a charge. my charger settings choices are as follows.

1) Charge absorption voltage 14.1vdc and float 13.5vdc when set as fla

2)Charge absorption voltage 14.4vdc and float 13.8vdc when set as gel

which of the 2 settings do you think would be better to use. ?

[fjoe]

number 2 for AGM batteries

[Odysseus]

Just for information.
UK battery supplier, first class service and you can talk to them about requirements,  very helpfull, and most of all very competitive.

I have no relationship with them.

Odysseus
Bav 38

[diverphil]

Ok.. thanks for the help.
Regards
Phil

[GeoffV]

Not sure that is true now. While "marine" AGMs such as Lifeline are still very expensive and only justified if you are a heavy user of 12v power, the newer automotive AGMs as used on cars with stop start are very competitive with good FLAs. The Exide 95AH AGMs as fitted to newer Bavarias are about £130 - 30% more than equivalent size FLAs but have over twice the total cycle times. They also take charge much faster and have low self discharge which is good for typical "weekend" type sailing. There are 5 in my boat, one for start, one for bow thruster and three in the service bank. They are now in their 6th year and I expect them to last at least 10 years. They hold their charge well over the winter - I only go on shorepower perhaps twice if they fall below 12.7v.

In my view a viable alternative and worth the extra expense if you intend keeping the boat to benefit from the longer life.

Ditto on my boat with 5 agm’s - 6 years old and still going strong with 200 watts of solar and a win gen.