Are My Batteries Toast?

[john61ct]

Voltage will never give accurate SoC, and most especially with a damaged bank.

A coulomb-counting monitor needs to be programmed with an accurate AH capacity number in order for its SoC reporting to have any chance of meaning, they are pretty inaccurate at the best of times.

The only way to get the AH capacity is the 20-hour load test outlined above.

As soon as that bank dropped below 150AH, it became worthless scrap lead, a significant safety hazard to keep on board a boat and thus in need of immediate replacement.

[daletournier]

Originally Posted by john61ct

Voltage will never give accurate SoC, and most especially with a damaged bank.

A coulomb-counting monitor needs to be programmed with an accurate AH capacity number in order for its SoC reporting to have any chance of meaning, they are pretty inaccurate at the best of times.

The only way to get the AH capacity is the 20-hour load test outlined above.

As soon as that bank dropped below 150AH, it became worthless scrap lead, a significant safety hazard to keep on board a boat and thus in need of immediate replacement.

Dosent a Smart guage measure voltage, isnt this the data it uses to compute soc?

[john61ct]

No. Proprietary AC impedance spectrography algorithms involving ​low level AC voltage interrogation, phase angle and amplitude of the current to get AC impedance of the battery across a wide variety of frequencies.

Combined with the historical info collected over dozens of cycles, and a database of known behaviors of various chemistry types.

Only Gibbo the inventor, and Merlin who bought him out, know the details.

[daletournier]

Originally Posted by john61ct

No. Proprietary AC impedance spectrography algorithms involving ​low level AC voltage interrogation, phase angle and amplitude of the current to get AC impedance of the battery across a wide variety of frequencies.

Combined with the historical info collected over dozens of cycles, and a database of known behaviors of various chemistry types.

Only Gibbo the inventor, and Merlin who bought him out, know the details.

So battery voltage.

[john61ct]

funny 8-)

[NevisDog]

Originally Posted by john61ct

Voltage will never give accurate SoC, and most especially with a damaged bank... As soon as that bank dropped below 150AH, it became ... a significant safety hazard to keep on board a boat...

Okay, thanks, (sorry to take time out from Op's questions) - when you say a safety hazard, can I take it you mean they could leave me without power for the 'house' side of things (not too great a concern - I still got flares and flags after all) or is there some other danger I'm unaware of?

I thought I read somewhere (?) that when capacity drops below 10% of original then it's time to scrap them - sounds like that figure is more like 70%.

[john61ct]

Yes, industry standard is when falls below 80%, 60-70% for near-shore sailors, they decline very quickly after that point anyway.

But also fire danger increases with chance of cells self-shorting.

[mitiempo]

Originally Posted by NevisDog

Okay, thanks, (sorry to take time out from Op's questions) - when you say a safety hazard, can I take it you mean they could leave me without power for the 'house' side of things (not too great a concern - I still got flares and flags after all) or is there some other danger I'm unaware of?

I thought I read somewhere (?) that when capacity drops below 10% of original then it's time to scrap them - sounds like that figure is more like 70%.

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

[Kenomac]

I'm trying to place a good charge on the battery bank for these first four days or so, so this device can learn how to do it's thing.

[NevisDog]

Thanks for all the advice, and those links - I read the first one before purchasing the battery monitor - should have read the second one, as that Balmar SmartGauge seems to be a step ahead.

[Dockhead]

Originally Posted by john61ct

No. Proprietary AC impedance spectrography algorithms involving ​low level AC voltage interrogation, phase angle and amplitude of the current to get AC impedance of the battery across a wide variety of frequencies.

Combined with the historical info collected over dozens of cycles, and a database of known behaviors of various chemistry types.

Only Gibbo the inventor, and Merlin who bought him out, know the details.

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.

Based on a couple of years of using the SmartGauge -- which is by far the best battery monitor in the business in my opinion -- I cannot see any evidence whatsoever that it does anything but track voltage with smart damping to deal with voltage sag under load (which it deal with very well) and with some algorithm to guess at state of charge achieved during charging (which it deals with poorly).

Under light loads and no surface charge, it precisely -- within 0.1 volt -- tracks the Trojan battery open circuit voltage chart. Maybe it does something besides track and analyze voltage, but I've never seen the slightest evidence of it.

It loses all orientation when charging takes place up to only a partial charge, and cannot guess even within 10% where you get to. And starts to read accurately only after surface charge is gone. This is a shame, because I'm sure that it would be possible to invent an algorithm which can "learn" this too -- SOC must be highly correlated to voltage achieved during the absorption stage -- but the SmartGauge is not this smart.

Doesn't matter much to me because that thing which I really want to know -- when do I need to charge -- how close am I getting to needing to charge -- the SmartGauge does superbly well.

How well it works on a boat like Ken's that is often getting a light solar charge -- I don't know. I don't have solar. If it can deal with this, then that will be a big advantage over simply reading voltage from a table.


Concerning evaluating SOC of a damaged bank -- I doubt that any method can deal with this.

[Dockhead]

Originally Posted by NevisDog

Thanks for all the advice, and those links - I read the first one before purchasing the battery monitor - should have read the second one, as that Balmar SmartGauge seems to be a step ahead.

If you buy it directly from the maker in the UK without "Balmar" stenciled on it, then you will save about half the cost.

[Dockhead]

Originally Posted by john61ct

.. .

But also fire danger increases with chance of cells self-shorting.

Yes. Bad cell is bad news. Will make a 12v battery into a 10v battery, and your charger will burn up the whole bank trying to get that 10v battery up to absorption voltage needed by a 12v battery. Will boil them out and may start a fire.

[Kenomac]

After the Smartgauge settles in, I plan on synching its full charge setting with my Magnetronic and resetting the total bank capacity down to 400ah allowing for degredation. Then over the following days, adjust the total bank capacity number until it correlates nicely to the Smartgauge SOC indicator.

This should then give me a fairly good indication of amps going in and out along with the SOC.

Today, I'll bring the batteries up to the 100% indicator, then check specific gravity with my newly found hydrometer and see how the SOC correlates with the Smartgauge. I realize it's going to take 4-5 charge cycles to become somewhat accurate.

[Dockhead]

Originally Posted by Kenomac

After the Smartgauge settles in, I plan on synching its full charge setting with my Magnetronic and resetting the total bank capacity down to 400ah allowing for degredation. Then over the following days, adjust the total bank capacity number until it correlates nicely to the Smartgauge SOC indicator.

This should then give me a fairly good indication of amps going in and out along with the SOC.

Let us know how closely you can get those two devices to agree with each other. That's interesting.

If you can finely calibrate the amp-counting meter using the SmartGauge, then you might have good information (which the SmartGauge can't provide) about SOC during charging.

The problem, however, is that amps in and out just don't correlate well with SOC. That's the root problem with amp-counting meters. But my guess is that you'll still have much better information, using these two different devices.


To put all this in perspective, though, query how much you really NEED to know about SOC. I have become much more relaxed about it, with experience. The most important thing by far to know is when do you need to start charging to avoid damaging your bank. With a reasonably large bank in relation to ordinary, constant loads like refrigeration and cabin lighting, a simple volt meter read against an open circuit voltage chart (NOT loaded voltage chart -- N.B.!) is perfectly adequate for this. Even if you're using solar, this will work -- because if the voltage is above 24.4 you can't hurt your batteries in any case.

The other thing you may want to know is when you can stop charging, if you're using a generator. You can easily learn with experience, what absorption voltage you need to get to, with your particular battery charger and batteries, to get to 80% or 90% or whatever your target SOC is.

So you really don't need any battery monitor of any kind, at all, to do the essential things in managing your batteries. But the SmartGauge is still mighty convenient.