Lead Acid vs AGM battert change

Indeed the boat does get hot here in LA. I have 3- yes 3- thermometers (they run in a range of about 10 degrees variance) in the cabin to get an idea of how hot it gets. Always above 100 June, July, August and Sept. Sometimes 120 and that is actual temp and not Heat Index. I have been told by others that 3 years on the average is about what is expected with batteries in general here.

I was thinking AGMs not just to get another year or 2 but to avoid the concern about having to add water. The batteries are under the quarterberth which is always covered with stuff and I'd rather be sailing, etc so my maintenance habits are not always the best.

I do find I have to add water every month or so. So that I do check regularly...kinda. The charger-- I was told I have one-- is somewhere in the beyond. I'll have to look more closely. I don't have a separate shore charger. I have a refrigerator (which only seems to run on AC shore power and not my batteries) that a previous owner added that takes up some of the space and sight line under the galley area back by the engine. But I recall "Ericson" on the outside of one of the metal boxes so that is likely the charger if that was standard equip with the E25+.

BTW, I run the engine about 20 mins a week, not daily. (Wish I could get out daily!) And, after I start on bat 1, I switch to Both. Only if I night sail (which I do a fair amount of in the summer since it's cooler) do I switch to bat 2.

I do put the voltmeter on the batteries ever so often. This last time when I did so after running the engine for about 10 or 15 mins, I got readings of 13.15v on one and 13.18v on the other. I thought that looked pretty good but the next day when I tried to start the engine, I had to switch to "Both" to get the 1-banger to kick over. I guess I should have then checked the readings on the voltmeter. And it's been several weeks since I checked the water level.

So I have some work to do this w/e, but- hey- this is a learning process! Thanks for all the helpful advice.

When you just finish charging, the batteries will always show a voltage that is much higher. You have to let it settle, or sometimes put a small load on it to speed things up, to find out its "real" voltage. Is it possible you measured the voltage right after shutting down?

OK, your batteries are lasting as long as other peoples. You are doing OK.

The time to check the voltage is when you are not charging or shortly thereafter. You want to know the voltage as you discharge the batteries. Below 12 volts is bad.

When I said 20 minutes a day, I meant on days when you were using the boat.

I agree with MaineSail; I don't think it's worth the money at the risk of blowing the alternator just to avoid filling the batteries. It's up to you.

Wow 120 degrees in the cabin can certainly speed up the self discharge and shorten life!!

To me it does not seem that you should be losing much if any water the way you run the boat unless you leave it connected to a non-smart shore charger all the time in 120 degree heat.

As Tom said, only charge when you are on or using the boat and your water loss should be very minimal if at all. The big down side is that self discharge in those temps can be very high so you might want to run the charger once or twice per week for a short amount of time to put back what was lost due to standby self discharge losses.

You might also check to see if you have any ghost loads drawing down the bank.

Also, using the BOTH feature when one battery can't start the engine only serves to bleed off precious cranking amps needed to actually start the engine. The second you hit BOTH with the engine off good amps from the good battery begin flowing to the bad battery. While not as bad with wet cells of similar sizes if you had a large bank you could literally kill the start battery by doing so and even more so with AGM batteries.

You would be better served to just switch to the other battery entirely for starting if one is dead than use BOTH. Ideally the BOTH feature should only be used when charging both batteries with the engines alternator, though there are now much smarter methods of charging two banks off one alternator. If your engine will not start on just one battery the batteries or connections are toast. It takes VERY, VERY little to start a single cylinder Yanmar.

Our 44HP Four Cylinder Westerbeke uses less than .1 of an Ah to start off a 230 Ah bank and than includes glow plug use. It also draws less than 160 peak amps and even then this is only for a split second. Even the smallest group 24 dual purpose batt should be supplying upwards of 600+ cranking amps especially at 100+ degrees.

I suspect you have a ghost load pulling down one battery as well as high summer temps killing your batts.

I believe that this is not off topic after reading this thread very carefully, but I have to say that the BEST investment I've made since getting my Ericson is the purchase and installation of a Victron BMV-602 dual battery bank monitor. There's no question that if properly set up, it tells me at all times just what's going on with the banks, under charge, under load, etc. So regardless of battery type selection, age, chargers used, etc it's my 'window' to everything electrical in the sub-systems! Hope this helps!

For a boat that day sails or weekends with minimal loads, no fridge, a battery monitor is great if you have lots of money and a love of toys. Otherwise it is that much more hair in the scuppers. For a boat that drains its batteries between charges a battery monitor is a requirement for good battery management.

As for Victron, the jury is still out. I bought one this spring, had a minor problem, it was replaced, the replacement failed and was replaced, and I am now waiting to hear back on my comments on the third unit. It's almost time for a phone call. I miss my old Link 10.

I too am planning to switch over to AGM. I use one in my camper (group 24) but it seems to me its even heavier than the group 24 lead-acid. Since its a strain to get batteries in and out of their locker in my E29 as it is, I'm considering getting 2 of the group U-1 AGMs. It doesn't seem to take much to light my Atomic A-4 and I'm never longer at anchor than three consecutive nights, and I'm converting my cabin lights to LED. Does anyone have experience with these smaller and lighter batteries?

Paul
E29 "Bear"

I understand that to get a true voltage reading with the multimeter you should disconnect all battery connections before taking a reading. Also, as mentioned earlier, if the batteries have been on a charger you should put a load on them (like turning on your cabin lights) for a few minutes before disconnecting them and taking the reading.

Mark - Why would you disconnect the batteries? Just turn everything off. To get a "true" reading you would have to wait for the voltage to stabilize.

There are not many reasons to measure the voltage after shutting down the charger.

I don't remember the reason for disconnecting the battery but I believe it was from a book on managing 12 volt electrical systems. The book is on my boat, so I'll have to look it up next time I am there. It also mentioned applying a load to the batteries before taking the reading.

The reason I think is more of a generality than an absolute. On many boats OFF is OFF but on many others there are still ghost loads or solar or wind charging sources that don't turn off with the battery switch.

Still can take a long time for the batts to stabilize. I've spent many hours trying to come up with a way to do better than "within 10%" but have not yet found it other than a long resting period. Deep cycle batteries with thick plates seem to hold surface charges for quite a while. 10% off for me is a whole days worth of bank use..