Battery load tester

[dhays]

Balmar has been selling the Smart Gage for some time, claims better than 5% SOC accuracy measuring only voltage (no shunt). Maine Sail has tested and likes it. I believe his argument is that most boat owners will not understand, install, and calibrate a true AH counter properly, so a dumb gage is better.

For my use, SOC is of little value. I want to know how many AH I am down, which tells me how much I have used and how much I need to replace. Also current usage or replacement rate. An auto calculating SOC does not provide that information: 50% of a new 200AH battery is 100AH, the same battery 5 years later might be 50AH. The devices on my boat consume and produce amps, not %SOC.

I currently have an Ah counter but I would like a Smart Gauge as well. The reasons are just as you state. The Ah counter tells me how many amps I've used, how many I've replaced, and how fast I'm using amps or replacing amps at any given time.


However, I would like to know my %SOC as well. My Ah counter will give me an estimate of that but only an estimate. If someone wants to make a practice of only discharging to 50% SOC, how do they know when that is? If you have a new 200Ah battery, you suggest that it is at 50% when you have used 100Ah. However, is that new battery really 200Ah? What is it after a couple of years? If you draw down and replace 100Ah repeatedly, that is fine. However, if your battery was only 190Ah when new (despite what the nice sticker on the battery said), and after a couple years it lost 5% capacity each year, that battery now only has 171.5 Ah capacity. Take out that 100Ah and you have now taken that battery down to 42% SOC instead of 50% SOC. That deeper discharge will further shorten your batteries life.


Currently, I am simply guessing when I setup my Ah counter as to how much capacity my battery bank actually has. A %SOC gauge such as the Smart Gauge could conceivably, tell me what the %SOC is regardless of the actual capacity. The Ah counter would still be very useful and in some ways MORE useful.


Of course, since this deals with electricity, I pretty much don't know what I'm talking about. So give anything I say with lots of Na.

 

[DDW]

The one use for SOC is to decide when to recharge, if you have the flexibility to decide. I believe I can guess the SOC from the AH counter as well as the Smart Gage can guess it from voltage. The Smart gage doesn't tell you much about what it is doing, or how it came up with it's guess.

Secondly, the need for high accuracy for this or most other battery purposes is limited. You've decided to use 50% SOC, but the life curves are not so steep that 40% or 60% are going to change that much. If you have the capability conveniently, you should recharge immediately, and only wait for 50% when it would be inconvenient to charge (like having to start the genset or engine for this purpose only). If the SOC routinely goes to 50% before you are forced to recharge, what it is really telling you is you need a bigger bank, or better charge sources.

One thing that strikes me as I enter the trawler world from the sailing world is how bad the DC charging systems on many - or most - trawlers are. I have the QSB 5.9 (you do to?) and the alternator on it is a joke. I kept a sailboat in the PNW for the last 4 years. In that time it was NEVER plugged into a dock, and as far as I can recall the engine was NEVER run just to charge the battery. I had a modest solar array and a very strong alternator, we had either enough sun or motored enough that no shore power cord was ever needed. My little 75 Hp engine had a 7 KW (280A@24V) alternator on it, and a second 80A@24V. The 380 Hp engine on the trawler has a 50A@12V alternator (they call it a 90 or 110 or something but it will never do that). We motor it around at 1300 rpm with about 300 hp to spare, and it is hardly charging the batteries at all. We've had to run the genset to charge the batteries through a wimpy 40A charger. All of this will be corrected next spring, but this is how all of the 200 or so AT34s were delivered.

OK I guess that was a bit of a rant, but there was no effort, in an otherwise well built production boat, to make the DC system anything but shore power cord dependent. From the things I read here, this is typical so they are just meeting the competition. Not sure if a Norhavn is much better, though listening to their genset drone in anchorages I'd guess not.

 

[psneeld]

There ARE mostly off grid, solar powered, curuising, liveaboard trawlers too.

And that doesn't really matter, it's your hoat's electrical setup and use that demands specific understanding and care.

Doesn't matter if it's a single group 24 or a 1200 amp hr bank. If you need it and it fails it's mission at the wrong time, you are screwed.

 

[BruceK]

DDW, I`m surprised your engine alternator is not doing better. We have twins, but they are Lehmans with original modest output alternators,we seem to recharge ok. Input is aided by a modest solar array which will feed a fridge and at the dock keeps the batts full,without recourse to shorepower charging.
Apart from any other solar you might fit, a small dedicated regulated panel for the genset batt, which otherwise only sees charge when the genset runs, has served well.

 

[JDCAVE]

Thanks for everyone’s assistance on this. The short answer seems to be that the standard automotive load testers will not be informative. At this time, I will not be able to do the 20 hour load test.

The bank has gone through 5 summers of use. The question I have is whether I can get a year or two more out of it. It’s an 1125 ah bank, with X 10 6VDC Trojans T105s. They are requiring more water, particularly over the past summer. Because of the solar charging setup, They rarely drop below 85% SOC, based on the original 1125 ah capacity. The “rough” resting voltages are consistent with the ah used as per the monitor for the Magnum I/C.

Jim

 

[john61ct]

Depends on your needs.

They may not be in a dangerous condition, but they certainly are not as reliable anymore.

The shallower discharging is great, but the other side of the coin is have you been able to ensure they're regularly getting back to 100% Full, or just taking charge sources' word for it they're not dropping to Float too early?

Would it be a dangerous situation for you if the bank unexpectedly failed?

Are you living on the hook far from a location where you can get quality replacements at a reasonable price?

If taking increasing chances of failure does not have dire consequences, then you'd likely be OK to risk it, as most people do.

 

[dhays]

OK I guess that was a bit of a rant, but there was no effort, in an otherwise well built production boat, to make the DC system anything but shore power cord dependent. From the things I read here, this is typical so they are just meeting the competition. Not sure if a Norhavn is much better, though listening to their genset drone in anchorages I'd guess not.

It isn't a rant. I think most production boats, even boats such as the AT, have a generic setup. It won't be ideal, but will meet most of the needs of most of the potential buyers. My boat is the same. Its setup isn't too bad, but it is dependent on either the genset or shore power.


I have been pleased with my boats ability to recharge from a typical 3-4 hour run at 1400rpm. I'll have to check again to see what alternator is installed, but I have the same engine you do.

 

[O C Diver]

Back in the old days, we use to refer to that tester as the portable grilled cheese maker. Coils get quite hot load testing an 8D battery.

Regarding battery life expectancy:

Part of the reason I bought open lead acid batteries (Trojan T105), was to be able to replace them at a reasonable price as needed. Mine are now 3 years old and doing great. If I were to do a big cruise in 2021, I would consider replacing them as opposed to rolling the dice. Last time I looked t105's were around $110 each from the place I use in "no sales tax Delaware ". For $800 to $900, it seems a pretty reasonable choice if in doubt.

Ted

 

[DDW]

It isn't a rant. I think most production boats, even boats such as the AT, have a generic setup. It won't be ideal, but will meet most of the needs of most of the potential buyers. My boat is the same. Its setup isn't too bad, but it is dependent on either the genset or shore power.


I have been pleased with my boats ability to recharge from a typical 3-4 hour run at 1400rpm. I'll have to check again to see what alternator is installed, but I have the same engine you do.

Do you know that the batteries are fully recharged in 3 hours? Or just up to 80-90%? This is an important distinction if you have AGMs.

AT's literature promotes it as a boat to cruise the inland passage up to Alaska. That will involve many days on the hook, and only a few hours run time between anchorages. A 6KW NL genset is standard, the installed cost of this must be at least $15K. For $15K (and actually much less) they could have installed a DC system that would sustain the batteries indefinitely without genset runs or shore power cords. This would cost only $3-5K, a $10K+ savings (not counting ongoing genset maintenance). I'd like to see them at least offer a proper DC system as an option. I'm sure they would do what you spec'd, but most buyers would be better served with a package as they are somewhat ignorant of the issues. An AT34 we chartered for a few days as a trial, running between anchorages 2-3 hours apart, had to have the genset started every other day as the batteries were at 50% SOC. The boat we eventually bought was built for the east coast, where air conditioning is a life sustaining requirement, in that case I can see being shore power or genset dependent. But not in the PNW.

The Delco 19SI alternator we have is rated at 105A cold. No hot rating is given but figure 75% of that. Even charging at 75A it will be hot very quickly. The internal regulator has a cold setpoint of 13.4V, inadequate to bulk charge LA batteries at any sort of speed, so the actual output is low. When warm (15 minutes of charging/engine run makes it warm) it cuts back to 13.1V. That isn't even float voltage for AGMs (13.8V), and will do very little charging. AGM's need to be fully charged periodically, the only way to do that on this boat is a shore power cord, or an engine run of perhaps 10 hours or more, as the charge acceptance of AGMs at 13.1V is very small. It desperately needs a properly set up 3 stage external regulator, but if it had one, it would burn up the alternator very quickly as it would be asked to do things it is not designed to do. A decent alternator and regulator is about $2500. That could replace perhaps 200 AH in a 2 hour engine run - enough for daily consumption - and would fully charge the AGMs in a 5 hour run. A few hundred watts of solar would be icing on the cake. In normal use I'd never have to run the genset or plug into shore power, and the batteries would live longer.

 

[O C Diver]

. A decent alternator and regulator is about $2500. That could replace perhaps 200 AH in a 2 hour engine run - enough for daily consumption - and would fully charge the AGMs in a 5 hour run. A few hundred watts of solar would be icing on the cake. In normal use I'd never have to run the genset or plug into shore power, and the batteries would live longer.

A 220 amp Leece Neville heavy duty alternator is hard to beat. I paired that with a Sterling 3 stage external regulator that will do most of the battery chemistries, for around $800. If you're paying someone else to do installation, probably need to double that. Adding it as a second alternator on my engine with a second crank pulley, probably cost me less than $1,200 doing most of the work myself.

Ted

 

[DDW]

The problem with Prestolite (L.N.) is their documentation is very sparse, making it hard to know what to buy and what you are getting. The Cummins QSB has a very tight installation and a peculiar offset to the pulley, so it's tricky to fit. No opportunity for a second alternator without major changes and fabrication.

There are few good regulators around now, I'll probably stick with the Balmar as it is more configurable and I'm familiar with it.

In alternators you get what you pay for. The one on the sailboat is an Electrodyne, cost about $2500 by itself, puts out 280A@24V (so like 560 @ 12), and the only recommended service is to repack the bearing every 20,000 hours. There is a continuum of quality and service life from there down to a Delco or Hitachi for $150. You picks your point and pays your money.

 

[john61ct]

Electrodyne, cost about $2500 by itself, puts out 280A@24V (so like 560 @ 12)

Wow, what does that need for mechanical power input, like 15HP?

 

[dhays]

Do you know that the batteries are fully recharged in 3 hours? Or just up to 80-90%? This is an important distinction if you have AGMs.

Yes, as near as I can tell with my coulom counter. However, I don't deeply discharge the bank between runs in most cases. Another reason I'd like the Smart Gauge.

 

[O C Diver]

The problem with Prestolite (L.N.) is their documentation is very sparse, making it hard to know what to buy and what you are getting. The Cummins QSB has a very tight installation and a peculiar offset to the pulley, so it's tricky to fit. No opportunity for a second alternator without major changes and fabrication.

There are few good regulators around now, I'll probably stick with the Balmar as it is more configurable and I'm familiar with it.

In alternators you get what you pay for. The one on the sailboat is an Electrodyne, cost about $2500 by itself, puts out 280A@24V (so like 560 @ 12), and the only recommended service is to repack the bearing every 20,000 hours. There is a continuum of quality and service life from there down to a Delco or Hitachi for $150. You picks your point and pays your money.

The large frame Leece Neville are a commercial alternator designed for firetrucks, paramedics vehicles and other applications of prolonged output at very low RPM. The series grows in length as the amperage increases. I believe the largest 12 volt model is around 800 amps. This units are bulkier and more heavy duty than the Balmar, with the ability to handle higher outputs at lower RPMs. I have mounted one on a C series Cummins in my charter boat and one in my trawler on a 4045 John Deere. Both required a second crank pulley and an alternator bracket mounted off the motor mount engine bracket. As their market is commercial applications, a good alternator / starter repair facility is the best source for information. Don't think you will find a continuous output 200+ amp alternator that will fit on either a B or C series Cummins engine. You may find some that work and intermittently reduce output, but the design space is really too small for a continuous output alternator of that amperage.

Ted

 

[FF]

New is always expensive , you might look at a Delco 50DN.


These are used in buses for decades so quality rebuilds are sold with no core charge.


12V or 24V 250-300A .