Are My Batteries Toast?

[Kenomac]

I need to figure out my target SOC on my Magnetronic while charging (since the Smartgauge isn't able to give me this figure accurately), correlate this number with the amps going in figure, in order to know when to shut down the generator and let the solar take over.

Yesterday's goal was 16 amps goin in, today I'll shut off the generator when the number drops to 6 amps to see if the solar will bring the bank to float status.

One of the primary reasons I need to know this stuff and be more aware of the numbers, is because unlike most boaters, it's been two months since Orinoco was plugged into shore power, and it will likely be another two months before we plug in again.

[Kenomac]

Today's numbers: Charged system to 10 amps going in SG to 92% and Magnetronic reset to 93% with house bank of 430ah. Large Mastervolt 75 amp battery charger went to float status, smaller Mastervolt 50 amp continued to charge. Shut off generator and let solar take over at 9am.

Checked specific gravity numbers which were consistent within each battery but inconsistent between batteries, which seems to indicate they're in need of equalization. Some were as high as 1275, while others as low as 1240. Is it possible to equalize using a generator, or am I best to wait until dockside to plug in?

[Paul L]

SG of 12.75 is a SOC of 100%, SG of 12.40 is approx SOC of 75% at standard test temperatures. See the table in the Trojan manual earlier in this thread.

[Kenomac]

Originally Posted by Paul L

SG of 12.75 is a SOC of 100%, SG of 12.40 is approx SOC of 75% at standard test temperatures. See the table in the Trojan manual earlier in this thread.

I already know this from having read the table prior to doing the test. Now I need to know why the difference and how to correct it, since each of the individual batteries seem to be in a different state of charge at the same time.

In approximately 10 days, I'll be visiting Hvar where I can moor at the town warf and have acess to shore power for battery equalization if necessary.

[Dockhead]

Originally Posted by Kenomac

Today's numbers: Charged system to 10 amps going in SG to 92% and Magnetronic reset to 93% with house bank of 430ah. Large Mastervolt 75 amp battery charger went to float status, smaller Mastervolt 50 amp continued to charge. Shut off generator and let solar take over at 9am.

Checked specific gravity numbers which were consistent within each battery but inconsistent between batteries, which seems to indicate they're in need of equalization. Some were as high as 1275, while others as low as 1240. Is it possible to equalize using a generator, or am I best to wait until dockside to plug in?

Cross checking with SG is very good! That's how I did it when I got rid of my amp-counting battery monitor and was trying to evaluate how well a simple voltage reading works.

Just be aware that deep cycle batteries can have significant stratification of the electrolyte, so your sample from the top may be much less dense than average. Breaking up this stratification is one reason why we equalize batteries, but a vigorous absorption charge will also do it.

If you have a big difference in SG between cells after equalization, that is a sign that your batteries are getting to end of life.

[Sailmonkey]

Originally Posted by Kenomac

Today's numbers: Charged system to 10 amps going in SG to 92% and Magnetronic reset to 93% with house bank of 430ah. Large Mastervolt 75 amp battery charger went to float status, smaller Mastervolt 50 amp continued to charge. Shut off generator and let solar take over at 9am.

Checked specific gravity numbers which were consistent within each battery but inconsistent between batteries, which seems to indicate they're in need of equalization. Some were as high as 1275, while others as low as 1240. Is it possible to equalize using a generator, or am I best to wait until dockside to plug in?

We don't have a battery charger aboard, so I'm forced to equalize with the alternator.......imho you should equalize once you're on shore power. Otherwise you'll be running the generator all day to run a battery charger.

[john61ct]

Originally Posted by Dockhead

And we know this -- how? AFAIK, nothing but hints have been released about the way the SmartGauge supposedly works.

I have an expensive professional battery tester which uses impedence spectrography to test battery capacity and SOC, and it does not give much useful information.

My "explanation" is really just a collection of snippets from dozens of such "hints" dropped in mail lists and forum threads Chris Gibson participated in over the years when the SG was first released, a
later when Merlin bought him out and he was doing development work for the military, and when Balmar started marketing (and supporting well I might add) in NA.

If it was simply extrapolating from voltage only, the design would have been copied decades ago.

Doesn't matter to me, magic black box AFAIC.

The best way to use ot in a solar setup is check before bedtime and then when you wake up. It does get more accurate after a couple weeks once the bank is back under load, need to leave it hooked up.

In conjunction with a good coulomb counter, using the SG to calibrate the "efficiency factor" of **your** unique setup, counting AH in & out does give a good feedback combination.

With FLA, the hydrometer adds even better data to tweak the efficiency factor more accurately, especially to precisely nail down the decline in capacity, every three months or so, to keep the shunt unit as precise as possible.

For solar look at Bogart Trimetric + a pair of SC-2030 under its control, also Whizbang Jr likely similar. Not sure if Victron has such tight integration with the BMV-702?

[a64pilot]

You could in theory equalize with a generator, just be prepared to run it a long time.
Step one to equalize is to start with a fully 100% charged bank, and you need to let it cool back down in my opinion, you don't want to start equalizing a bank that is hot, heat is bad for batteries.
Smart gauge will flash an error code during equalization, or mine does with my 12 V bank, but it is not hurt.
Everything on my boat will accept equalization voltage, but be careful it may be higher than a component can handle.

A true capacity test is beyond almost any cruising Sailors equipment list.
However it's my opinion that with an AH counter and a Smart Gauge that you can tell the useable capacity of your bank close enough and can spot declining capacity and need to equalize.
For example if you had a 100 AH bank, and your Smart Gauge says your at 50% SOC, and your AH counter says you have used 40 AH, then your useable capacity is 80 AH. Assuming of course you started with a 100% fully charged bank. Then equalize and run the test again later to see how much you get back from equalizing. The test of course is just resetting the AH counter in the afternoon is all at the end of charging.

An issue it's a PIA to do all of this, takes time, but fortunately little actual effort. This is what I think what Sailorboy means by obsessing over your battery bank, only you can decide if all the effort and worry is worth it, or just buy a new bank every few years when it becomes obvious that it's gone.

[daletournier]

You can definitely do it with a generator, I have on previous boat. AC is AC. I think it took about four hours.

Have a look at charger instuctions Ken, it should explain the procedure.

Also I'm with dockhead regarding using the voltage to determine approx soc, first up in the morning prior to solar getting any light, its closer enough to give you a decent idea, ive tested this against the acceptance rate (generator charger). I like my batteries being no further down than 12.4v in the morning at anchor and 12.2v in the morning after an overnight passage. Gives an approx idea which is good enough.

[a64pilot]

Oh, in my opinion you can tell if they are toast if overnight they discharge more than 50%. Assuming of course bank was big enough to begin with, which I'm sure it was. Your coastal cruising and I assume batteries are available, so why not get all the good out of them before you replace them.
Good thing about equalizing and determining capacity with the Smart Gauge and AH counter, is you can see how long it may be before eventual replacement and can plan on that expense and maybe do some shopping around for a good price.
However as you cruise 6 months on and work the other 6, I would not buy a new bank at the end of one of my cruises, I'd limp on the dieing bank, and buy the new one at the start of the cruising season.

[Kenomac]

OK, at the end of sunshine today my batteries were in float status according to both battery chargers. Hurray.

So here's the question:

Seven off my Trojan 6v batteries had specific gravity readings of 1.260 in each cell, and one had readings of 1.240 in each cell. The Smartgauge which is still learning indicated 96% and my Magnetronic showed 99.3% with a capacity of 420Ah.

The chart indicates 100% at SG of 1.277 and 90% at 1.258 and 80% at 1.238

What does this mean?

[a64pilot]

It means most likely that your smart gauge is likely correct and your batteries were not full. You cannot trust chargers, Id fix it so the Solar stayed in absorption and never tripped to float.
On the battery that is low, I'd look to see if wiring could possibly be it, a dirty or loose connection or maybe the bank is improperly wired so it's not getting fully charged

[Kenomac]

Two of my solar controllers on the 120w panels had gone into float status for several hours and the remaining three had dropped to delivering between .8 and 1.4 amps combined to the batteries. When on shore power charged to 100%, this is what I see. Maybe another couple of days for the Smartgauge to become smart(er).

[a64pilot]

My Smart Gauge has been installed for a couple of years. It isn't accurate when the bank is charged hard, like on generator and both chargers are going, but under Solar when it's dribbling it in, it's pretty close.
Mine seems to be awful accurate right out of the box, but since manually set it at 100% cause my bank had been on shorepower an in float for weeks, so I am sure it was fully charged.

[hzcruiser]

Originally Posted by Kenomac

Yes, partly cloudy all day. Kotor, Montenegro.

You should be back to a blue sky now and for the forseeable future!

Greets from Korcula!