Batteries: Do I Have to Change All of Them?

[S/V Alchemy]

Originally Posted by pteron

If you consistently charge to only 90%, you are going to suffer more sulfation.

The initial cost of the batteries is only one part of the equation but the easiest to see and be swayed by.

True, but regarding state of charge, I was apparently unclear. I meant that if you restrict draw down of your banks to no less than 60% (400 Ah of a fully charged 1000 Ah bank, for instance) before you apply a fresh charge, then you will get plenty of life/full number of cycles. In other words, just because you can deeply cycle them, doesn't mean it's a good habit to have.

The goal is of course to get to the 100% charge and to stay there. Practically, you should think how far you'll go before you recharge, and either get more battery capacity or more charging capacity. Me, I plan on running a biggish lead-acid bank (provisionally 4 x 8D/840 Ah) with echo charging to an AGM start and an AGM windlass battery forward. I have 4 x 135 W solar and 400W wind, plus 2 x 2000W Honda generators to use, before I switch on the diesel with two 100 W alternators. The goal is to stay at anchor with refrigeration and comms and LED lighting for five-six windless, cloudy days without switching on the engine, and with "favour" given to the solar and wind amp sources mediated to the bank via an MPPT.

You could go the other direction, of course, and have half or less of that bank charged by a 3K genset.

A coastal weekender needs less capacity...just enough to keep steaks and beer cold Friday night to Sunday afternoon in an anchorage. Essentially, a single flexible panel could do a bit of charging, but it's essentially just about keeping the electricity flowing until you throw the shore power cord back on.

[btrayfors]

It's practically impossible for a cruising boat away from the dock to achieve 100% charge on it's house batteries, unless doing a LONG motoring leg.

It takes hours after achieving 85% state of charge (SOC) to bring the batteries up to 100%. Yes, solar and wind power are great things and, possibly, can do this but, remember, to do this they must generate substantially more power than is being used on the boat for an extended period.

Also, while 100% charge is a great thing and it's nice to float your flooded batteries at 13.2-13.8 volts or so, even this voltage alone is not sufficient to prevent sulfation. You really need a boost charge periodically to kick loose the PbSO4 crystals, even a periodic equalization charge of 16V or more.

FWIW,

Bill

[pteron]

Originally Posted by btrayfors

Also, while 100% charge is a great thing and it's nice to float your flooded batteries at 13.2-13.8 volts or so, even this voltage alone is not sufficient to prevent sulfation. You really need a boost charge periodically to kick loose the PbSO4 crystals, even a periodic equalization charge of 16V or more.

That's interesting - do you have a reference for this requirement?

My understanding is that AGM doesn't tolerate the over charge as well as the flooded cell batteries as it has limited capacity to deal with the gasses produced but in turn doesn't require it as it is less prone to sulfation.

I'd say that a 100% charge is a requirement, anything less and your batteries will suffer.

[btrayfors]

Originally Posted by pteron

That's interesting - do you have a reference for this requirement?

My understanding is that AGM doesn't tolerate the over charge as well as the flooded cell batteries as it has limited capacity to deal with the gasses produced but in turn doesn't require it as it is less prone to sulfation.

I'd say that a 100% charge is a requirement, anything less and your batteries will suffer.

Good question!

To give a full answer would require more time and space than I have available. Let me try to summarize.

My statement re: sulfation even with fully charged batteries derives from personal experience on my boat and with Trojan T-105's at home, plus battery experiments with "de-sulfators" over a 2-year period, plus reading, plus...."my hunches".

In the literature, you'll find all kinds of statements. Frequently you'll find "sulfation begins the moment electrolyte is added". Others say that sulfation begins when the charge falls below X % SOC. It's axiomatic that batteries for sale even in large vendor locations (e.g., West Marine) vary considerably in their measured capacity, presumably due to sulfation as they were allowed to sit with less than a full charge. Nigel Calder once told me he'd measured something like a 30% variance in NEW battery capacity in the store!

I have a total of 10 T-105's. Eight of these are on my boat, six of which are in series/parallel and rigged as a single house bank. The other two are forward under the V-berth and are for my windlass. The latter two are maintained by an Iota DLS-55/IQ4 charger with a float voltage of 13.6. They are on 24/7. The first six are maintained by a Victron MultiPlus, also on 24/7.

At home, I have two T-105's maintained 24/7 by an Iota DLS-45/IQ4 @ 13.6VDC.

Over time, I've noticed that the measured capacity of those on more-or-less permanent 13.6V float charge has deteriorated. So, too, did the six T-105's on "permanent" 13.2V DC charge with the Victron.

Until, that is, I changed the settings on the Victron to bump up the float voltage (to 14.0) and the periodic every-other-day repeat absorption voltage to 14.4VDC for 1/2 hour. The batteries showed a marked improvement over a 5-month period.

During the 2-year desulfator tests we found that none of the commercially-sold desulfators we tested really did much...almost no discernable improvement. However, equalization at 15.5-16.5 volts did make a difference, and sometimes a big one.

So...my non-scientific but heavily experiential and anecdotal conclusion is that maintaining your flooded lead-acid batteries at 13.2 to 13.8 really isn't enough....you need to periodically bump up the charge voltage to the 14.4 plus range and, occasionally, to the equalization range of 15.5 or more in order to keep their capacity up. Also, very important, is exercising them....after a few deep discharges and charges their capacity increases significantly.

I recently did a very deep discharge of two 14-year old gelled golf cart batteries in my basement. Then, fully charged them, including a controlled overcharge. Next day, they tested almost like new, much better than they'd tested in the four years I've had them (after living 10 years on a friend's sailboat).

Lotsa mysteries still to be unravelled :-)

Bill

[pteron]

Bill, loads of good stuff there, thanks. Maybe you've found the secret to prolonging battery life indefinitely? Expect a Trojan hit squad any day now...

[btrayfors]

Ha! We'll see.

What I did, though, was to discuss my findings with Trojan engineers. They told me that the results are very believable, and that in general modern battery chargers voltages are set too low...most likely due to liability concerns.

Here's the pic showing the results for four of the six batteries in my bank:



You can see from the tests in February that four of the six house batteries showed a marked improvement from a year ago. These four, by the way, are co-located under my port aft cabin berth, while the other two are located under the nav seat to starboard, some 8-10 feet away. The Victron charger is connected to the batteries under the nav seat. All are run as a single bank, with 1/0 cable connecting them. Probably too small.

Anyway, I'll do another test in a few weeks and see if these results hold up.

Note that the two at the top, and the two at the bottom are those which are maintained 24/7 by Iota IQ4 chargers, using a float voltage of 13.6. You can see that they've deteriorated over the past year.

Bill

[pteron]

I'm interested in seeing the results.

My day job is designing power management for much much smaller batteries - Li Ion for mobile devices, but it is interesting to see the similarities between Li Ion and Lead Acid charging.

Have you analysed AGM batteries?

[btrayfors]

I'm very wary of AGM's, because...

1. too many reports of catastrophic failures;
2. limited personal experience with AGM's dying faster than flooded batteries;
3. lower number of discharge/recharge cycles than either flooded or gels;
4. almost no one has a setup to take advantage of their higher charging acceptance rate;
5. too many client's alternators burned out by just replacing their flooded batteries with AGM's and not upgrading their onboard charging capacity; and
6. for many sailors, flooded or gels are better choices.

TPPLs may be a good alternative; Nigel Calder loves them, as does a professional colleague.

That said, Mrs. Lincoln, how did you enjoy the play?

Bill

[S/V Alchemy]

Originally Posted by btrayfors

It's practically impossible for a cruising boat away from the dock to achieve 100% charge on it's house batteries, unless doing a LONG motoring leg.

It takes hours after achieving 85% state of charge (SOC) to bring the batteries up to 100%. Yes, solar and wind power are great things and, possibly, can do this but, remember, to do this they must generate substantially more power than is being used on the boat for an extended period.

Also, while 100% charge is a great thing and it's nice to float your flooded batteries at 13.2-13.8 volts or so, even this voltage alone is not sufficient to prevent sulfation. You really need a boost charge periodically to kick loose the PbSO4 crystals, even a periodic equalization charge of 16V or more.

FWIW,

Bill

All true, and all (I hope) accounted for. The equalization charge can be obtained from different set points on the MPPT; the panels, for instance, put out 17 VDC from 11 to 1 in the tropics on a clear day. The alternators can be adjusted to do this as well.

I see it as a problem of management. Yes, a periodic dockside equalization charge is nice and may prove to be necessary, but it's not impossible to vary your charge sources to get that level of volts.

As for motoring, as our boat is a steel sailboat, we will likely alter periods of sailing with long (12-24 h) motors in light air if we are on passage, during which it should be pretty straightforward to get the batteries full and in good form.

Slightly off topic, does anyone have opinions about the supposedly "anti-sulfation additive" I've been seeing in the back of sailing magazines?

[S/V Alchemy]

Originally Posted by btrayfors

I recently did a very deep discharge of two 14-year old gelled golf cart batteries in my basement. Then, fully charged them, including a controlled overcharge. Next day, they tested almost like new, much better than they'd tested in the four years I've had them (after living 10 years on a friend's sailboat).

Lotsa mysteries still to be unravelled :-)

Bill

No kidding! There's still a bit of "black art" involved in battery science. I had the PO of our boat, who had (then) 17 season old Trojans, promise to buy us a new set of batteries as part of selling us the boat. But he said if we could wait a couple of months, he was going to work at a West Marine and could get the "employee discount". So we said, "fine, but what about these old batteries?" Well, the electrolyte level and density was OK, but they weren't reading much about 12.6...enough to start the diesel about twice, as I recall. He set up a charger he brought aboard and gave them 24 hours at between 15.5 and 16 volts. I thought he would cook them off, but they seemed fine...didn't even seem warm. Afterwards, he measured the electrolyte levels again, put in about 30 cc of distilled water, let them sit for an hour and got 13.1 out of the them. They charged at 14.2 from the old 40 amp charger aboard and held in the low 13 volt range for running the boat. We used them much of the summer without a problem, these batteries that went into our boat when my wife was still in highschool...and we switched in new Seavolt 6vdcs in the fall, which I still have and which aren't dead yet.

So the "overvoltage equalization" thing seems to have merit, but you have to have pretty close regulation of the inputs.

[btrayfors]

Yep, equalization works wonders sometimes.

However, note that voltage -- resting voltage after sitting overnite with no charge and no load -- has very little to do with the health of the battery, that is, with the CAPACITY of the battery to store and deliver energy (amps).

Lots of people believe their batteries are just fine and use them even with greatly reduced capacity because they're not really putting a lot of load on them.

The only reliable ways to tell about the condition of your batteries (i.e., their capacity) are:

1. a good battery tester which measures internal resistance and conductance (these are expensive, but are the current industry standard); or

2. a controlled load test over time, in which you typically put a 20-hour load on the batteries and measure their output.

I have a little homemade setup for doing load tests: a breadboard setup with six 12-Volt bulbs of various wattages which can be switched in and out of the circuit, connected to an ammeter and used in conjunction with a WattsUp analyzer which measures volts, amps, watt-hours, etc. I use it by calculating the approximate load for a 20-hour test, then switching in the needed bulbs (the "load") and letting it run overnite.

I've found that the results track pretty well with the results from my Midtronics MDX-650 tester (about $600).

It's sometimes amaaaazing how much energy is left in batteries which are considerably deteriorated, i.e., whose capacity is much reduced from new. So, it's no wonder that partially deteriorated batteries on boats are happily used by owners who believe they are still "good".

And, of course, we all know that starting batteries are always "good" until that fateful day when they won't start your engine :-)

Bill

[Alecadi]

The sequel...

As I am very smart.. I bought equivalent batteries at a better price from Defender, and made in the US not Germany...
So smart that I supposed that based on pictures and capacity they were identical in shape (and dimensions?)
Well I hope Defender will accept them back.. they are too long for a fraction of an inch and don't fit in my batteries compartment.
And all the 6v battery built here have the same dimension...
Fortunately my friend Geoff get some 6v 380AH so we will use only 2 of them instead of 4, that can be used put on their sides ( I didn't even know that that kind of batteries existed!!) (By the way the 2 cost as much as the 4 previous!! a large amount!!)

[Alecadi]

I'll have them on Thursday and will tell you how it went. Hope the problem will be fix.
Now I have to get rid of the new Defender's one that don't fit. Waiting from Defender to accept them back. If note I'll try to sell them on CF, as they said: "My loss your gain"

[Alecadi]

The German 6v Batteries had a size that fit perfectly the batteries compartment, or the compartment was built for them..
impossible to get the same size in the USA and make them coming from Europe was really too costly. (500+ per battery!). Try every 6v manufacturer around, no way!

So we found at U.S. Battery 12 V AGM 198 Ah that can be put on their side and that way they fit perfectly in the compartment.

So now they have been installed as one bank, 12 v 400AH
and the cranking battery still there.

Problem solved, thank you all for advices and comments

Alec

[chala]

Originally Posted by Alecadi

So now they have been installed as one bank, 12 v 400AH
Alec

In my view multiple bank configuration is preferable. In a one bank configuration the batteries are in parallel if one battery develop a fault it will bring down the complete bank. Also the efficiency is poor. Being in parallel each battery as a tendency to recharge the other batteries this underload or in stand by. Charging efficiency as low than 80% have been quoted. A conventional battery monitor will not record this loss of capacity of the bank.

Originally Posted by btrayfors

It's practically impossible for a cruising boat away from the dock to achieve 100% charge on it's house batteries, unless doing a LONG motoring leg.
Bill

This is easily achieved with a two banks configuration. On my boat when one bank is carrying the load the other is easily recharged to 100% with a 40W unregulated solar array.