Battery Woes...

[Skip Gundlach]

Battery Woes...

Well, Dang!

I installed new Deka L16 batteries (4x370AH, bank 740AH in April 2014. They
appear to be at the end of their lives at ~30 months in. We have been
diligent in keeping them watered with distilled water, and have battery
saver caps to minimize water loss.

We charge with a Honda 2000 connected to our shore power, which feeds a
Xantrex 70A/1500W temperature-probed inverter-charger. That has a design
issue which makes it not float out well, so we transfer to our 40A
stand-alone charger for the last of it.

We monitor everything through a Trimetric battery monitor. We fully charge
once a week or more often, through, also, our 370W solar feeding a Blue Sky
6024H MPPT controller, and our KISS wind generator, and equalize once a
month (using the Honda and the Xantrex).

When we're motoring, our alternator keeps up with it, but doesn't seem to
have a good control/regulator; even though the output shows low net incoming
amps after a long while, our cumulative AH shows positive values (20-40AH
typical) which, of course, goes away the moment the engine is off, but our
battery is certainly fully charged, if not equalized.

All charge sources are fed to a single buss protected by a 500A in-line
fuse. Our typical charge is at 25-30% discharged, so the battery doesn't
work very hard. It has been to 45% discharged a few times, and once to 55%
(Hurricane Matthew, with the KISS disabled, and not much sun in the 4 days
we were off the boat).

In the last few weeks, I have gotten up in the morning to ~220AH used - less
than 30% discharged - and found voltage at 11.3. Not good at all - whassup?
So, I've been wrestling, with no solutions or even clues.

We've been fully charging about every 2-3 days of late, due to work we've
been doing which requires the Honda, and yesterday I fully charged (one hour
at 14.1V or better) and equalized (2 hours at 15.2V or better), and
immediately read the batteries with a temperature-compensated hydrometer and
also our voltmeter, at the end, while still charging, the individual battery
voltages (ya, I know - they weren't disconnected).

The 4 had divergent readings at the end of the equalization cycle: 8.0,
7.3, 7.33 and 6.68 volts. The banks/pairs are 1/4 and 2/3, and,
cumulatively, the banks had the same readings, but with very different
single readings. I suppose that could be laid to the fact that I couldn't
effectively disconnect them, but it's still pretty weird...

Temperatures were very different between banks one and two (read down each
water-fill hole; I've averaged the 3 readings per battery) immediately after
equalization:75, 98, 100, 73F - from which I gather/intuit that bank one
(1/4) got much less amperage, somehow, or there was some problem in bank 2.

Specific gravities were lousy. All the cells read in about the same range
per battery, with bank 1 faring much better than bank 2: Bank one averaged
about 1.227 and bank two, temp compensated for 8-10 added, averaged 1.220 -
but that included one cell in 2/3 - at both ends; cells 5-8 read 1.220, but
had 1.235 and 1.260 in cells 4 and 9.

None of them was better than fair, and many of the cells were in the edge of
the "charge" range - immediately after equalizing.

So, clearly, something is amiss.

Beyond just bad luck, are there any ideas of how this might have occurred,
given the above? And, my presumption, are these batteries toast?

Thanks.
Skip
Morgan 461 #2
SV Flying Pig KI4MPC

 

[capta]

If you need to replace your batteries I highly recommend you sail to San Juan. They'd be much cheaper there.

 

[Stu Jackson]

Skip,

Extremely good analysis and presentation.

Only thing I see missing is a discussion of checking every single electrical connection and what voltages at the individual batteries were when charging.

Also, what's that strange float issue with the I/C?

I'd also, if you haven't yet, post this on cruisersforum.

Good luck,

Stu

 

[centerline]

the L16 and other 6V GC batts (2, in series to create 12volts) should be charged to 14.7.... anything less and it can shorten the life of them.
normal chargers dont charge that high unless they are an adjustable unit and have been turned up to handle 6V GC batteries.
with the cost of the L16 batteries, I would be inclined to remove them and attempt to recondition them (any battery supply house should be able to do this for you) at the proper reconditioning voltage.
and then try to determine what on the boat, besides the low charge voltage may have contributed to their early demise.... it may actually be one of the batteries have gone bad and is trying to drag the other one down with it....

short of a completely failed battery, the batteries have obviously been damaged to some degree, but those L16's are tough and with a good reconditioning you may still get several years out of them with the proper charge voltage going into them...

 

[Maine Sail]

I installed new Deka L16 batteries (4x370AH, bank 740AH in April 2014. They appear to be at the end of their lives at ~30 months in.

Were the batteries ever commission charged? For batteries that are to be wired series or series>parallel I wire them in parallel then charge to 7.4V and about 0.5% or less of tail current base on the 20 hour capacity. The batteries are now "balanced" and can now be wired series>parallel. Batteries wired in series will have a very tough time "self balancing". If they are not in good balance one battery can easily become over charged while the other gets chronically undercharged....

We charge with a Honda 2000 connected to our shore power, which feeds a Xantrex 70A/1500W temperature-probed inverter-charger. That has a design issue which makes it not float out well, so we transfer to our 40A stand-alone charger for the last of it.

I am assuming by the term "charge" you are referring to bulk-charging In order to "charge" (fully charge) L-16's is going to take upwards of 8-12 hours with good equipment and correct voltages, and even longer with sub-par equipment.

We monitor everything through a Trimetric battery monitor. We fully charge once a week or more often, through, also, our 370W solar feeding a Blue Sky 6024H MPPT controller, and our KISS wind generator, and equalize once a month (using the Honda and the Xantrex).

I suspect you are putting WAY too much trust in your Ah counter. When was the last time you conducted a 20 hour capacity test and re-programmed the Trimetric for the banks actual capacity?

How are you defining "full"? Until your bank is accepting approx 0.5% of Ah capacity in charge current, at 14.7V to 14.8V, its simply not full. Many battery monitors attempt to re-set at 2% but again this is not a full battery and you're leaving sulfate on the plates.

Keeping Your Battery Monitor More Accurate (LINK)

When we're motoring, our alternator keeps up with it, but doesn't seem to have a good control/regulator; even though the output shows low net incoming amps after a long while, our cumulative AH shows positive values (20-40AH typical) which, of course, goes away the moment the engine is off, but our battery is certainly fully charged, if not equalized.

GIGO data (garbage in>garbage out) is simply unacceptable data to use. Unless your Trimetric has been painstakingly programmed and reset to 100% SOC when the batteries are actually at 100% SOC this data can be extremely misleading. The only reliable & repeatable way to determine full, on a cruising boat, is to hold absorption voltage (14.7V to 14.8V) until the net accepted current falls to approx 0.5% of bank Ah capacity or less.

Our typical charge is at 25-30% discharged, so the battery doesn't work very hard. It has been to 45% discharged a few times, and once to 55% (Hurricane Matthew, with the KISS disabled, and not much sun in the 4 days we were off the boat).

If the battery is left sulfated from chronic under charging it is still being worked hard. Shallow cycles are certainly much better for it, less sulfation created during discharge, but full charges must be attained as often as is humanly possible otherwise you will continually "walk down" the usable capacity due to PSOC (partial state of charge) use.. Low charging voltages, which can be a volt sensing issue, inadequate voltage regulation settings or alternators that reduce voltage as they heat up, and inadequate absorption duration are the two biggest hurdles most boaters deal with.

If you are only cycling to 70% SOC then you are also playing in the most charge inefficient range of the battery so your absorption voltage duration is absolutely critical in order to reach 100% SOC..

You will need to figure the correct duration out for your use and bank via SG or tail current @ absorption voltage. For a bank like that it will typically require 4-6+ hours of absorption, once absorption voltage has been attained, before float kicks in. If your charge sources do not allow an adjustment of the absorption duration, and far too many are absurdly short 1 hour or 2 hour egg-timers, then you'll want better charge equipment. For a live aboard cruiser solar simply disable float or set it to at least 14.3V with absorption being 14.7V+. If you leave the boat for extended periods re-set the float voltage.

In the last few weeks, I have gotten up in the morning to ~220AH used - less than 30% discharged - and found voltage at 11.3.

Based on what you've given us, it's pretty safe to say your bank has nowhere near the capacity that you have programmed into the monitor. Like many boaters with Ah counters you've put far too much trust in the Ah counter predicting SOC and too little attention to actual battery voltage..

This is not just for you but for all boaters.

DO NOT REGULARLY DISCHARGE BELOW 12.2V EVEN UNDER LIVE AVERAGE HOUSE LOADS

Sure on a long passage it is okay to dip towards 11.7V, but if this basic premise had been followed you'd have very quickly realized the bank was walking down in capacity and the Trimetric was fooling you. A bottom voltage is the best thing any boater with an Ah counter can incorporate. You can even set an alarm for 12.2V...

We've been fully charging about every 2-3 days yesterday I fully charged (one hour at 14.1V or better) and equalized (2 hours at 15.2V or better),

Three hours of absorption is not full and 14.1V spells murder for L-16's.....

The 4 had divergent readings at the end of the equalization cycle: 8.0,7.3, 7.33 and 6.68 volts. The banks/pairs are 1/4 and 2/3,

Not really that weird they have been under charged, likely not properly commission charged, and they have become out of balance or started life out of balance and this just got worse. This could also be due to bank interconnect wiring or trying to alternate two house banks instead of one large contiguous bank... I also have no idea what you mean by "The banks/pairs are 1/4 and 2/3,"?

Temperatures were very different between banks one and two immediately after equalization:75, 98, 100, 73F

You had one out of balance battery being pushed to 8V, and this is the equivalent of 16V, while another battery was at 6.68V which is the equivalent of 13.36V.. The bank is severely out of balance.

Put another way you have two batteries in series that have become out of balance and they look like this during charging.

Battery #1 = 8V
Battery #2 = 6.68V
Charger See's = 14.68V


Battery #1 - Being grossly over charged
Battery #2 - Being grossly under charged

Specific gravities were lousy.

Sounds like chronic under charging & sulfation...

None of them was better than fair, and many of the cells were in the edge of the "charge" range - immediately after equalizing.
And, my presumption, are these batteries toast?

I have an idea yes but we really need more information on equipment, wiring, bank use, bank wiring, alternator model and amp rating, Blue Sky settings etc....

The batteries may be toast but may recover to a suitable & still usable smaller size too. Best to conduct a 20 hour test to see where they stand. 370Ah / 20 = 18.5A constant load for a capacity test to a 10.5V cut off. If the battery only runs a fraction of 20 hours this will be the percentage in-hours, of the 20 hour rating. For example if the battery only runs for 10 hours to 10.5V at 18.5A and at 75-80F, then the bank is at 50% of its rated capacity and is pretty much done for. If it runs for 16 hours you're at 80% of rating and the bank is starting to approach the danger zone...[/quote]

 

[Franklin]

wow...that is a lot of amps. If you have to do it over, I'd suggest something simple like 400 watts of solar panels feeding 12v trojan wet cells with just 390 amp 20 hours (3 SC225). It would be much cheaper and less running a generator. That is what I do and I'm on the computer for 10-12 hours a day due to work and other stuff along with all the other stuff like frig. I rarely need to run the genset. The 400 watt wind generator helps though.

 

[Skip Gundlach]

My apologies for not having come back on these comments. I don't seem to have a notification setting and didn't know about them until I was posting our findings.

I'll come back in a bit and address them. Lots of good stuff...

 

[Skip Gundlach]

Skip,

Extremely good analysis and presentation.

Thanks

Only thing I see missing is a discussion of checking every single electrical connection and what voltages at the individual batteries were when charging.

The voltages were noted, but I hadn't said that in the new installation, the cables were burnished bright, bolted Very Tight (note scientific quantification of torque), and thoroughly 'battery-terminal-spray'ed.

During our checkouts further along, I noted no voltage drop between terminals, so if there is any imbalance, it didn't show itself.

Also, what's that strange float issue with the I/C?

I don't really know, other than the tech's telling me, at the time the second board was replaced, that these didn't do that well and that it was a reason that they were no longer available.

I'd also, if you haven't yet, post this on cruisersforum.

Actually, I have - and the followup seen here today as well. Thanks for the direction...

Good luck,

Stu

Thanks - and thanks for the followup.

 

[Skip Gundlach]

the L16 and other 6V GC batts (2, in series to create 12volts) should be charged to 14.7.... anything less and it can shorten the life of them.
normal chargers dont charge that high unless they are an adjustable unit and have been turned up to handle 6V GC batteries.

I would anticipate that my marine units are designed for this sort of service. However, I don't have the raw amperage available to me to do bulk charging quickly.

How does one 'turn up' something to handle golf carts (of which these are on steroids, twice as tall and heavy)?

with the cost of the L16 batteries, I would be inclined to remove them and attempt to recondition them (any battery supply house should be able to do this for you) at the proper reconditioning voltage.

Hm. Interesting thought. R&R is not a simple matter in these. I don't think ours can be trusted (see today's followup post), however. Should that later (next set) become an issue, I'll remember that. If it saves a set otherwise assumed dead, it's worth it. Bulges (see today's), not so much.

and then try to determine what on the boat, besides the low charge voltage may have contributed to their early demise.... it may actually be one of the batteries have gone bad and is trying to drag the other one down with it....

Short of some surprise, I have no doubt whatsoever that the issue for our current system is our refrigeration. Whether or not we can manage to make it less voracious is still to be seen, but it's definitely what drives our consumption. Based on final SGRs, I don't think I have a bad battery or bad cell (other than a bulge issue) per se, but it's clearly a bad situation...

short of a completely failed battery, the batteries have obviously been damaged to some degree, but those L16's are tough and with a good reconditioning you may still get several years out of them with the proper charge voltage going into them...

I think we're not going to be able to achieve that, unfortunately.

Thanks for the comments.

 

[Skip Gundlach]

Thanks for the comprehensive reply. I've been - suggested in another thread elsewhere - to your site and read a bit about your battery info...

Unfortunately, I don't know how to make my comments, to which you responded, show up also, but...

Were the batteries ever commission charged? For batteries that are to be wired series or series>parallel I wire them in parallel then charge to 7.4V and about 0.5% or less of tail current base on the 20 hour capacity. The batteries are now "balanced" and can now be wired series>parallel. Batteries wired in series will have a very tough time "self balancing". If they are not in good balance one battery can easily become over charged while the other gets chronically undercharged....

[/QUOTE]

They came new from the factory; I questioned their state of charge at the time, but charged them initially. Based on what I've been reading, they might never have actually been fully charged. I even had the tech out again later, but he pronounced them all 'good' and as expected, including load testing.

I have not yet decided what I'll do about a replacement, but if it's not locally sourced, getting them fully charged may be an issue. And, the local (St. Lucie Tire and Battery) outfit which provided them may not even have the right gear to do that (being 6V)...

I am assuming by the term "charge" you are referring to bulk-charging In order to "charge" (fully charge) L-16's is going to take upwards of 8-12 hours with good equipment and correct voltages, and even longer with sub-par equipment.

[/QUOTE]

Heh. Perhaps. But I nearly always was charging in the low-200s AH down, or 75-80% SOC. OTOH, based on what I've been reading, I agree with your assessment about time required being dramatically longer. A new inverter-charger may be in the offing, but it's frustrating, as we next to never use the inverter, and when we do, the 1500w is more than ample; a larger charger would come with a much larger inverter potential, at presumed significantly larger cost.

I suspect you are putting WAY too much trust in your Ah counter. When was the last time you conducted a 20 hour capacity test and re-programmed the Trimetric for the banks actual capacity?

[/QUOTE]

Probably no surprise, but so far as I can tell, never, and we've not been ratcheting down the bank size, either. I read your piece on controllers, so know that it's strictly a crapshoot as to what lower settings I should be programming, in what time periods.

So, we'll be doing our best to keep up with that moving forward.

How are you defining "full"? Until your bank is accepting approx 0.5% of Ah capacity in charge current, at 14.7V to 14.8V, its simply not full. Many battery monitors attempt to re-set at 2% but again this is not a full battery and you're leaving sulfate on the plates.

Keeping Your Battery Monitor More Accurate (LINK)



GIGO data (garbage in>garbage out) is simply unacceptable data to use. Unless your Trimetric has been painstakingly programmed and reset to 100% SOC when the batteries are actually at 100% SOC this data can be extremely misleading. The only reliable & repeatable way to determine full, on a cruising boat, is to hold absorption voltage (14.7V to 14.8V) until the net accepted current falls to approx 0.5% of bank Ah capacity or less.

[/QUOTE]

I'm operating from memory, but I think the cutoff for us was on the order of 35A for one of the setpoints (1/20th or 5% as the manual said, I think).

As to the 14+ (greater than .2 for us, typical)V, I don't know that we EVER saw that other than in equalizing. Yet, as I type now, that number is showing up regularly in the bright sun and good breeze, with a net positive amps in the 2+ but under 3 range. That, of course, is our being connected to shore power continuously, with non-sun/wind aided typical being 13.6-7 with ~1A net in.

Unfortunately, I don't think I have any metric which will tell me the net accepted current (?). The monitor only shows what's happening, not controlling anything. Those controls would be a function of the controllers for both the shore power (40A) and the solar, currently set on 'equalize' - our KISS is unregulated, our never having had an issue (or at least that was our perception) with overcharging...

If the battery is left sulfated from chronic under charging it is still being worked hard. Shallow cycles are certainly much better for it, less sulfation created during discharge, but full charges must be attained as often as is humanly possible otherwise you will continually "walk down" the usable capacity due to PSOC (partial state of charge) use.. Low charging voltages, which can be a volt sensing issue, inadequate voltage regulation settings or alternators that reduce voltage as they heat up, and inadequate absorption duration are the two biggest hurdles most boaters deal with.

If you are only cycling to 70% SOC then you are also playing in the most charge inefficient range of the battery so your absorption voltage duration is absolutely critical in order to reach 100% SOC..

You will need to figure the correct duration out for your use and bank via SG or tail current @ absorption voltage. For a bank like that it will typically require 4-6+ hours of absorption, once absorption voltage has been attained, before float kicks in. If your charge sources do not allow an adjustment of the absorption duration, and far too many are absurdly short 1 hour or 2 hour egg-timers, then you'll want better charge equipment. For a live aboard cruiser solar simply disable float or set it to at least 14.3V with absorption being 14.7V+. If you leave the boat for extended periods re-set the float voltage.

[/QUOTE]

Having to cope with the least efficient charging arena doesn't make my job easier - but my controllers don't have the flexibility for adjustment (or at least I havent' seen any), unfortunately, other than the solar to be left on 'equalize.'

So, I'll likely pay a great deal more attention to the indicated voltage, and figure out how to make it charge for longer.

Based on what you've given us, it's pretty safe to say your bank has nowhere near the capacity that you have programmed into the monitor. Like many boaters with Ah counters you've put far too much trust in the Ah counter predicting SOC and too little attention to actual battery voltage..

This is not just for you but for all boaters.

DO NOT REGULARLY DISCHARGE BELOW 12.2V EVEN UNDER LIVE AVERAGE HOUSE LOADS

Sure on a long passage it is okay to dip towards 11.7V, but if this basic premise had been followed you'd have very quickly realized the bank was walking down in capacity and the Trimetric was fooling you. A bottom voltage is the best thing any boater with an Ah counter can incorporate. You can even set an alarm for 12.2V...

[/QUOTE]

Our "low" level has shown 0.00 forever; I've not figured out how to capture it otherwise. At some point our batteries got to 15.8V, as that's what's shown as the high. However, getting anywhere near 12V (other than just recently, in these events which caused me to go to work) is a rarity. I'll have to dig deeper into my Tri-Metric instructions about that.

Three hours of absorption is not full and 14.1V spells murder for L-16's.....



Not really that weird they have been under charged, likely not properly commission charged, and they have become out of balance or started life out of balance and this just got worse. This could also be due to bank interconnect wiring or trying to alternate two house banks instead of one large contiguous bank... I also have no idea what you mean by "The banks/pairs are 1/4 and 2/3,"?

[/QUOTE]

I couldn't figure out how to post a pic of how our cabling is set up, but the 4 L16 I designate as 1,2,3,4, with those being port aft, port forward, starboard forward and starboard aft, in that order, and I count (identify) cells in the same fashion when I'm doing a SGR. So, if I consider 1&4 batteries as 'bank 1' and 2&3 batteries as 'bank 2' I can identify the two 12V pairs which parallel (one house bank only) to make my 740AH house bank.

The cables are all substantial (0, I think), but are not the same inch length. There's one pair-link which is only 8" or so, and the longest might be 2' for the parallel link, with the rest being mostly shorter, somewhat. Would that little a discrepancy be significant?

You had one out of balance battery being pushed to 8V, and this is the equivalent of 16V, while another battery was at 6.68V which is the equivalent of 13.36V.. The bank is severely out of balance.

Put another way you have two batteries in series that have become out of balance and they look like this during charging.

Battery #1 = 8V
Battery #2 = 6.68V
Charger See's = 14.68V


Battery #1 - Being grossly over charged
Battery #2 - Being grossly under charged



Sounds like chronic under charging & sulfation...

[/QUOTE]

My earlier comments might have helped, or hindered

But, the second charge was much more consistent, in order, being (at rest, with the house loads applied) 7.11, 6.82, 6.85, and 6.56, the last being the one with the bulge, and 1/4 and 2/3 pairs were pretty consistent, cell-to-cell (see subsequent update post) so that raises a question, perhaps, about cabling?

I have an idea yes but we really need more information on equipment, wiring, bank use, bank wiring, alternator model and amp rating, Blue Sky settings etc....

The batteries may be toast but may recover to a suitable & still usable smaller size too. Best to conduct a 20 hour test to see where they stand. 370Ah / 20 = 18.5A constant load for a capacity test to a 10.5V cut off. If the battery only runs a fraction of 20 hours this will be the percentage in-hours, of the 20 hour rating. For example if the battery only runs for 10 hours to 10.5V at 18.5A and at 75-80F, then the bank is at 50% of its rated capacity and is pretty much done for. If it runs for 16 hours you're at 80% of rating and the bank is starting to approach the danger zone...

[/QUOTE]

I'm not sure what info I can provide other than what's already been said, but if you'll give me some guidance about those individually, I'll do my best to respond.

We have a Xantrex 1500w/70A, a Xantrex True Power 40, a Blue Sky (using the above wattage) 2460H, a KISS wind generator, and a rebuilt-to-70A Delco 35A charger with external controller, all feeding the bank through a buss bar/post setup, with in-line 500A fuse.

We've never pulled the battery down to anything lower than 11.1; the inverter and the reefer both shut down somewhere in that range, so we don't have any readily available large loads to make it down further.

All that said, with a bulging short side to battery 4, we consider the bank dead.

 

[RonRelyea]

So ... following all this, I'd like to do a 20 hour test. I have 4 Duracell EGC2 in series/parallel totally 460 Ah. This means I need a 23 amp load. Being a neophyte, I'm at a loss for what I can use to put this kind of load on my system. Any suggestions?

 

[jssailem]

Ron, What if you turned on all the lights, fans, powered a laptop, electronics, a converter and let some ladies do their hair, heat the out doors with a space heater. Lots of options.

 

[RonRelyea]

Ron, What if you turned on all the lights, fans, powered a laptop, electronics, a converter and let some ladies do their hair, heat the out doors with a space heater. Lots of options.

John .... you know ... I turned everything on including the refrigerator and got a whopping 12.7 A ... HOWEVER, you reminded me that I do have an inverter (which I never use and is our-of-sight/out-of-mind). I ought to be able to suck up some juice with that! Thanks for the inspiration!

 

[Maine Sail]

So ... following all this, I'd like to do a 20 hour test. I have 4 Duracell EGC2 in series/parallel totally 460 Ah. This means I need a 23 amp load. Being a neophyte, I'm at a loss for what I can use to put this kind of load on my system. Any suggestions?

Ron,

I'd recommend doing a C/20 test on each pair at 11.5A... You can build your own quasi C/20 tester out of 12V light bulbs (car headlights etc.) and a PWM dimmer (Blue Sea 7508 etc.) to dial the current in or light bulbs & resistors and switches to adjust the load as the voltage drops. You can also find eBay/Chinese PWM dimmers out there but they are harder to find in 15A and over.

I do not recommend using on-board systems as your load as it is critical to the test that the applied DC load be very constant/steady throughout the 20 hour test to 10.499V...

Keep in mind that if doing this on-board the batteries should be at 75F to 80F and isolated from the DC system.....

 

[RonRelyea]

RC ... Thanks, as always, for the knowledge .... I'll get the Blue Sea 7508 and string some car headlights ...
I'm in Florida now so the 75-80 temp is not a problem ;-) and I will split the bank in two ... I have a Victron BMV 602s ... As long as I isolate the boat systems can I use this to meter load and voltage?

 

[Maine Sail]

RC ... Thanks, as always, for the knowledge .... I'll get the Blue Sea 7508 and string some car headlights ...
I'm in Florida now so the 75-80 temp is not a problem ;-) and I will split the bank in two ... I have a Victron BMV 602s ... As long as I isolate the boat systems can I use this to meter load and voltage?

You can actually use the relay port to drive an external relay to cut off voltage at 10.5V but it is overkill. Just be there to watch it and when the battery hits 10.5V stop the discharge and begin recharging...


How do I conduct an accurate 20 hour capacity test?

#1 Fully charge battery then allow it to rest, disconnected, for 24 hours

#2 Make certain battery temperature is between 75F & 80F

#3 Apply a DC load that = Ah Capacity ÷ 20 (small light bulbs and/or resistors can work)

#4 Connect an accurate digital volt meter to the positive and negative battery terminals

#5 Start DC *load and a stop watch at the same time (*DO NOT stop & start load it must be constant for the entire test duration time it so you can be there between the 10 hour & 20 hour marks))

#6 As battery voltage drops, during discharge, adjust the DC load to maintain as close to the C÷20 rate as is humanly possible. A good quality PWM dimmer can be used to dial the load in better.

#7 Immediately stop the discharge test when battery terminal voltage hits 10.499V

#8 Note the hours and minutes of run time on the stop watch and figure your percentage of 20 hours that it ran. This is your batteries Ah capacity or state of health as a percentage. For example if a 100Ah battery ran for 16 hours it's at 80% of its original rated capacity. Flooded lead acid batteries are considered “end of life” when they can no longer deliver *80% or more of their rating. (*For house loads most batteries will still work safely down to about 70% of as new rated capacity but beyond this the failure rates become quite unpredictable.)

#9 Recharge the battery immediately at the 20 hour rate. Follow this up with equalization level voltage and measure specific gravity until all cells match. (not for non-Lifeline AGM or GEL). A long slow recharge can have a slight reforming effect on flooded batteries and can actually recover some lost capacity.

"But RC isn't 10.5V bad for my batteries?"

A once yearly discharge test, done correctly, is arguably less damaging than taking your battery to 50% SOC and leaving it in that range for a day or two or the continual PSOC cycling the average boater thinks nothing of. Regular PSOC cycling is more damaging than a once or twice yearly Ah capacity test done correctly. A capacity test, done correctly, simply counts as another deep cycle. In lab testing quality deep cycle batteries can handle hundreds of cycles to 10.5V and this is because they are immediately recharged after the discharge. Cycling at 50% SOC to 80% SOC for a week is far more damaging to the battery than a single once yearly capacity test done correctly.

WARNING: The only time your batteries should regularly be taken below *12.1V, even under normal house loads, is during a capacity test. For regular house use, at your average house loads, your deepest loaded voltage should ideally not dip below 12.1V or better yet 12.2V.

Unless you are running short duration high load device such as an inverter, windlass, electric winches, thruster, water maker etc. don't let your bank voltage dip below 12.1V. For certain situations, such as an off-shore passage or open ocean racing discharging to 70-80% DOD is acceptable provided the batteries receive a proper charge as soon as you get to the destination. Discharging below *50% SOC, on a regular basis, in a PSOC environment drastically shortens battery life when compared to 50%. (*Firefly & some GEL batteries would be an exception for regularly discharging below 50% SOC.)

 

[Skip Gundlach]

(clipped, just to get MS' attention by the quote)

Hi, MS,

Well, I went to your link about the Balmar smart controller; I have that question answered (in the 'update' thread). As this thread likely will continue to areas not specific to us, but very helpful to others (like, for example, me, when I went searching for some answers when all this started), I'll hop over to the update thread.

However, I trust you saw, in my multi-segmented reply to your detailed reply here, our 4 batteries are a single bank but two pairs of 6V yielding each pair at 12V/(as new, presumed) 370AH, and that all our charge sources come to busses positive and negative; if I could figure out how to post it, I'd show you the cabling between the batteries before those single-lead connections exited the box.

Thanks for your detail. More over in the update thread.

L8R

Skip

 

[Skip Gundlach]

(clipped, just to get MS' attention by the quote)

Hi, MS,

Well, I went to your link about the Balmar smart controller; I have that question answered (in the 'update' thread). As this thread likely will continue to areas not specific to us, but very helpful to others (like, for example, me, when I went searching for some answers when all this started), I'll hop over to the update thread.

However, I trust you saw, in my multi-segmented reply to your detailed reply here, our 4 batteries are a single bank but two pairs of 6V yielding each pair at 12V/(as new, presumed) 370AH, and that all our charge sources come to busses positive and negative; if I could figure out how to post it, I'd show you the cabling between the batteries before those single-lead connections exited the box.

Oops. I think I figured it out. This is a prior installation; the cables are the same but cleaned up, and as noted, no voltage drop between batteries across them, and still brilliant when I took them off to try to swap a pair.

Thanks for your detail. More over in the update thread.

L8R

Skip

 

[Maine Sail]

View attachment 131604

Thanks for your detail. More over in the update thread.

L8R

Skip

I hope you've corrected the deficiencies in that wiring since that pic was taken...

Incorrect use of a fuse (needs to be in a fuse holder)
Incorrect location for a fuse (should be in + conductor)
Incorrect fuse type (should be ANL, Class T or MRBF to meet AIC requirements)
Incorrect location for a temp sensor (can not be on positive terminal and can not be between lug and terminal)
Incorrect lug stacking (highest amperage lug is always on the bottom)
Unequal series & parallel wiring lengths (in order to keep batteries balanced wiring should be as short as possible and equal as close to equal lengths as possible)
Massive amounts of corrosion
Open lugs with no adhesive heat shrink or even tape
Possible ferrous nuts or washers resulting in rust
Positive & negative wires physically crossing/laying on one another
2GA high amperage wiring is marginal at best for a 46 footer especially one with an inverter or windlass. A Xantrex 1500W inverter requires 1/0 wiring for a 1-3 foot circuit and 2/0 for a circuit of 6-10 feet (round trip)..

 

[Skip Gundlach]

I hope you've corrected the deficiencies in that wiring since that pic was taken...

As below:

Incorrect use of a fuse (needs to be in a fuse holder)
Incorrect location for a fuse (should be in + conductor)
Incorrect fuse type (should be ANL, Class T or MRBF to meet AIC requirements)

The fuse was removed; all leads now on single buss-type fuse with terminal posts and cover for 500A fuse ANL type

Incorrect location for a temp sensor (can not be on positive terminal and can not be between lug and terminal)

The temp sensor was removed during our current bank installation, and was put between the batteries; is that appropriate?

Incorrect lug stacking (highest amperage lug is always on the bottom)

I'm unfamiliar with the term (lug stacking), nor how to determine highest amperage lug. Assuming that our replacements likely will be the same (US L16HC-XC2) but now with L lugs, and that we're limited to that real estate, how would you cable this? The positive and negative leads are the only ones leaving the bank (though the PowerPulse connections might be on the terminals in the current installation; I forget)...

Unequal series & parallel wiring lengths (in order to keep batteries balanced wiring should be as short as possible and equal as close to equal lengths as possible)

Ah. That answered one of my questions. Even though the difference is a matter of inches, that's a significant event in the health of the bank?

Massive amounts of corrosion

The current installation is pristine. And frustrating, because physically, until I discovered the bulge on the left side of the top right battery (again, the pic is of the installation preceding the current one), they looked like new.

Open lugs with no adhesive heat shrink or even tape

Hm. Aside from that being a trivial remedy (I have it in hand, and will do that with whatever cabling goes in the new bank), what's the significance here, in an isolated environment (strapped lid on secure box)?

Possible ferrous nuts or washers resulting in rust

These are SS hardware, 1/4x20 bolts, nuts and washers, currently; I think they were in the pic, too, but as noted, it was lousy in that picture.

Positive & negative wires physically crossing/laying on one another

Ah. I wasn't aware (nor were any of the marine electricians who were responsible for the installations so far) that was an issue. As above, how would you cable this installation, both to remedy previous and this issue?

2GA high amperage wiring is marginal at best for a 46 footer especially one with an inverter or windlass. A Xantrex 1500W inverter requires 1/0 wiring for a 1-3 foot circuit and 2/0 for a circuit of 6-10 feet (round trip)..

[

Each leg is probably 3' or so; I don't know the gauge, but it's very substantial.

However, that brings another - probably expen$ive - question; given a Honda 2000 as the typical available 'shore power' what is the best inverter-charger to replace this likely-inaccurate/aging 1500/70? Or, if the real estate were available, maybe a stand-alone for each? Our inverter-alone loads are very infrequent, and are used for operating either a Stinger mini-shopvac or our heat gun for defrosting, or, even more rarely, perhaps a 60w soldering iron, so a larger-capacity inverter/charger would likely have a severe overhead redundancy in the inverter portion. We mostly have the Honda running whenever we use one of these, anyway, so COULD manage without an inverter, I suppose.

Thanks for your erudition and depth. Maybe it's possible to teach an old (72) dog new tricks...

L8R

Skip