Are My Batteries Toast?

[Kenomac]

I'll be in Korcula in 10 days, yes it's beautiful today and the battery bank is 100% in float status so I reset the Smartgauge to 100%. Where will you be in 10 days time?

[hzcruiser]

Originally Posted by Kenomac

I'll be in Korcula in 10 days, yes it's beautiful today and the battery bank is 100% in float status so I reset the Smartgauge to 100%. Where will you be in 10 days time?

Back in Sydney, as that's where the boat is at the moment. All going well I'll be in the Med with the boat next summer!

Good luck with the SmartGauge and please keep us posted!

[Kenomac]

I'm beginning to have some serious doubts regarding this Smartgauge.

My battery bank was in float status all afternoon according to my battery chargers, Magnetronic monitor and the solar Genasun controllers, so I reset the Smartgauge to 100% where it remained all afternoon with the other indicators.

The sun goes behind the mountain and the Smartgauge immediately drops to 92% while all other indicators remained at 100% and began showing a slow rate of discharge.

There's no way I used 35-40ah in 10 minutes as indicated by the not-so-Smartgauge. Nothing was turned on and the solar was still producing a little according to the other indicators.

[a64pilot]

No, it's smarter than you realize, you were in float, but not 100% charged, that is what it is.
Trust that thing I have no idea at all how it works, PFM maybe, but it does indeed work.
Read Maine Sails article on the thing, if it didn't work he would have found out, but as long as it's a lead acid battery, the thing works.

Once you go into float here is essentially no more charging going on, if you drop into float at 92% you stay at 92%.
Trick those chargers to stay in absorption, and maybe over time you will get to 100% charged since you have a daily generator run, at least that is my experience, it's tough to overcharge being only at absorption voltage if you use the bank.

On edit, it could also be that one low battery that amounts to the missing 8%.
Wait till you get on shorepower, then by recycling the power switch on day one to make darn sure your at 100% by watching acceptance rate, leave them on float all night to cool, and the next day push them through an equalization charge according to the manual.

On my charger I sometimes have to turn it off and on three times to get to 100%, it's not going to hurt it if you stay in absorption for a few extra hours to be sure. Think about it, if your only charging at 4 or 5 amps, how long is it going to take to heat up how many hundred lbs of the bank with only 5 amps of power going in?

[Kenomac]

Update: My Magnetronic doesn't seem to be working, it's not counting off the ah and been acting intermittent since I installed the Smartgauge, not sure why, the two devices don't share any wiring or connections.

I'll reset the battery chargers tomorrow when they get to 92% in order to pack in some more amps to hopefully get them closer to 100%

I plan on plugging in to shore power for a day sometime late next week, so I'll reset the Smartgauge to 100% at that time.

[Dockhead]

Originally Posted by Kenomac

I'm beginning to have some serious doubts regarding this Smartgauge.

My battery bank was in float status all afternoon according to my battery chargers, Magnetronic monitor and the solar Genasun controllers, so I reset the Smartgauge to 100% where it remained all afternoon with the other indicators.

The sun goes behind the mountain and the Smartgauge immediately drops to 92% while all other indicators remained at 100% and began showing a slow rate of discharge.

There's no way I used 35-40ah in 10 minutes as indicated by the not-so-Smartgauge. Nothing was turned on and the solar was still producing a little according to the other indicators.

Why don't you check it against specific gravity?

Smartgauge is not "indicating" that you consumed AH's. It doesn't measure or care about AH's.

Smartgauge does not deal well with SOC when there are charging sources -- just like a simple voltage reading doesn't tell you much. So solar maybe confuses it.

But this doesn't actually matter so much -- why do you care? Once you start drawing down the batteries and the surface charge is off, it will give you the most accurate evaluation possible of where you are -- and that's when you really care.

[hzcruiser]

Originally Posted by Kenomac

I'm beginning to have some serious doubts regarding this Smartgauge.

My battery bank was in float status all afternoon according to my battery chargers, Magnetronic monitor and the solar Genasun controllers, so I reset the Smartgauge to 100% where it remained all afternoon with the other indicators.

The sun goes behind the mountain and the Smartgauge immediately drops to 92% while all other indicators remained at 100% and began showing a slow rate of discharge.

I think you've tricked the SmartGauge by (re)setting it to 100% SOC while the solar charge controller was on (and keeping the voltage higher than the battery resting voltage). A better way would have been to disconnect the solar, let the batteries rest for a few hours without any load on them and then set the SOC to 100%.

The same happens on pretty much any system: as soon as you disconnect the solar charger the batt voltage goes down to the resting voltage.

Originally Posted by Kenomac

There's no way I used 35-40ah in 10 minutes as indicated by the not-so-Smartgauge. Nothing was turned on and the solar was still producing a little according to the other indicators.

You're right as in you didn't use 35Ah. But that's not what the gauge said, or is it? It said your SOC "seems" to have dropped by 8%. (And you calculated that into Ah which you based on the original capacity of your banks? Here might be a second possible error creeping in).

The SmartGauge has to take a few parameters into account to come up with a SOC: battery voltage is one of them, current in or out is another (I don't remember if you mentioned you had a current shunt fitted). You can measure the battery terminal voltage yourself: Right after the sun disappears the voltage will most likely drop significantly. And when that happens the SmartGauge has to reflect that on its display, otherwise you might think it's broken. If the gauge only uses the voltage, then it has to tell you a lower SOC if the voltage drops, right?

Regarding your first post: as mentioned, a microwave is a big load on the batteries, in your case around 42A for a 1000W oven. The bank voltage will drop significantly and that's expected (unless you have LFPs, they tend to have less of a drop under load).

The same with cloud cover: the charge controller cannot keep up the voltage anymore and it drops down, again, as expected.

Less water to refill since you have fitted solar: that's a good thing, it means you don't need the same large amounts of charge current when running the engine or generator. Huge currents mean more acid gets split into oxygen and hydrogen but they cannot recombine quickly enough and the gasses escape through the vents. Now some "base load" is provided by solar.

Your windlass: I would check the brushes before replacing them, they are usually pretty beefy but that depends on the manufacturer, of course. I replaced my windlass motor last year but only because the cast iron housing had a fair bit of corrosion which caused water ingress.

You said it runs ok if the generator is on or the motor provides extra power. As mentioned, you would need to check the cable contacts for corrosion and yes, an ageing (but still working) battery bank will show some weaknesses there first.

I "tackled" that issue with a separate set of batteries for the windlass in the foc'sle, wired in parallel to the bilge bank but I can disconnect them remotely at any time. Even from here in Croatia while the boat is in Oz ;-)

[hzcruiser]

Originally Posted by Kenomac

I plan on plugging in to shore power for a day sometime late next week, so I'll reset the Smartgauge to 100% at that time.

Same issue then: the shore charger will keep a float voltage will is higher than the 100% SOC resting voltage. Think trickle charging...

[john61ct]

The key is how you define 100% full in order to be sure when to let the BM know.

Charge sources are the least reliable.

AH-counting shunt monitors not much better.

Using accurate instrumentation - ammeter and DMM/voltmeter and a manually controlled power supply is the way to go.

Proper voltage, high end of the mfg spec.

Keep charging until charge amps falls to say 1% of AH capacity, so 6A for a 600AH bank. Actual rate as per mfg specs.

Then - and this is key - you have to let the bank sit, no charge, no loads, for **minimum** 24 hours, 72 is better. Also true for hydrometer SG readings.

That is then the point to tell the BM the bank is full.

Obviously for most this can't be done very often. I find doing it same time as the monthly equalization protocol works for me.

The SG will take a few weeks, continuously connected through say twenty cycles, to improve its accuracy.

It will be within 4% with the bank at rest, 10% or so off while charging depending on current, and in between under light loads.

That's as good as it gets with realtime SoC monitoring.

The AH-counting BMs give supplementary info, but should be calibrated to the SG and hydrometer, not v/v. They also need to be updated with the declining AH capacity as that walks down.

And the whole point of all this is to not pay attention to the charge sources, program them to only go to float when SG says 100% or even a bit more.

[john61ct]

This is worth repeating, re-read those links, google and ask questions until the contents are well understood.

Originally Posted by mitiempo

Without the proper settings on your battery monitor - exact size of bank in AH - you will never know where you stand.

These links should help:

Installing A Battery Monitor Photo Gallery by Compass Marine How To at pbase.com

Keeping Your Battery Monitor More Accurate Photo Gallery by Compass Marine How To at pbase.com

[a64pilot]

However since we are talking Smart Gauge here, maybe this one
http://www.pbase.com/mainecruising/smart_gauge

[transmitterdan]

Ken,

Being in "float" has no meaning with regard to whether the batteries are charged. Chargers often go into float based on time. This is because when charging and drawing from the bank at the same time it may never go into float without the timer.

Some chargers allow you to adjust the "time to float" in the range of 2-4 hours. If your charger has that consider setting the timer to a longer time than it is now. Big banks require more absorption time than smaller banks.

[Paul L]

You already know the batteries are not at 100% by the specific gravity readings you posted, so it does not make sense to set your battery monitors to a 100%.

[Sailmonkey]

Originally Posted by Paul L

You already know the batteries are not at 100% by the specific gravity readings you posted, so it does not make sense to set your battery monitors to a 100%.

Ding ding ding!!!!

Setting all the counters and gauges to [emoji817] % when the battery specific gravity is not at the density required to be [emoji817] % is fooling no one but yourself. Your batteries have been chronically undercharged from day one (based on your other threads). What you need now is an intensive round or rounds of equalization to bring all of the SG values together and up to the [emoji817] % charged value (temperature compensated of course).

Only once you've done this are you at [emoji817] %.

However you can stop obsessing about it and just enjoy life knowing that with two chargers and solar your batteries are being better fed than the majority of boats out cruising.

[softdown]

Your battery bank is in good condition. There is no better test than SG.

All of my solar problems have come from one battery developing one bad cell. That acts to short out the whole battery bank and my security system wakes me up in time to save the food in the fridge and freezers...via using the genset.

I get a bad cell in a single battery about twice a year. I did not buy high quality solar batteries the first time around. Everything else...I did almost perfectly. A highly experienced "friend" advised me that truck 8D's were clearly the best solar battery for the money. He could not have been more wrong. Now I sit on the opposite extreme with FullRiver pure lead AGMs that weigh 170/lbs battery. The difference is astounding.

I have done a *LOT* of SG testing. There are roughly four tons of new and old batteries around here that I experiment with. Voltage reading will also tell you how good the battery is. The difference with SG is that it will tell you if you are developing a bad cell. A really, really bad cell reads close to "water" and that cell will "short out" the capability of the entire bank.

You have seen the effects of start up surge on your voltage readings. You have been advised of start up surge as well. Some motors may demand 4-5 times their stated power when surging to life. Especially is there is a significant load like your windlass will experience with deep water and a "good/bad hook" I'll bet your inverter fan usually kicks on when there is a start up surge of a significant motor. Microwaves are notorious heavy users. Many consume 1300-1500 watts of power. There are certainly inducements to cooking with gas...

Battery connections are under rated. I'll just assume that you have good ones. Post #37 (I am softdown - imagine that) has a picture of the best battery bus bar though possibly not realistic on most boats. Best way to hook up eight 12 volt batteries for 48 volt system... — northernarizona-windandsun

We'll see if this link works: