Looking to Charge a Behemoth Bank

[jordiebsocal]

Hi all,

I own and maintain a 46' Ray Creekmore Marconi Masthead sloop named MAX.
I live aboard with my partner in life, and my partner in boat..... The eventual goal (2-3 years) is to sail MAX back around the world as she has in the past with a previous owner. She is a rather heavy displacement boat of 16 tons (32,000 dry and empty) and will have moderate to heavy energy consumption based on the projected gear that we plan to outfit her with.

We plan on being off the grid for quite a while and will be collecting most of our own energy with the occasional top off from the 200A Delco Remy 28Si Alternator.

I have just purchased and built out a containment area for (8) Trojan L16H-AC battreries. At 125#/ea, there is now an extra half ton of balast in our fair lady, MAX.

(4) sets of 2 connected in series, then in parallel

The bank will be 1740Ahr @ 20C discharge.

All battery cables will be 1/0 ANCOR tinned marine battery cable.
All interconnecting cable lengths will be the same length with ANCOR closed ended Lugs and heat shrink.
I will have a 250A Class T fuse on the Hot lead about 1 foot outside of the main battery compartment.

I have ordered and will be installing the Trojan Single Point Watering system for ease of watering as I have been told that these batteries need frequent equalizing, and therefore topping off with distilled water. (looking forward to seeing how that works out.

I will eventually be adding 750w of solar to the top of the dingy davits along with a Morningstar MPPT TS60 charge controler.

Here is the issue that I am dealing with at present.

My current charges is one of the Statpower Truecharge 40A chargers.

Trojan's Data sheet for the L16H calls for a 14.8v Absorption Charge and a 13.2v float.

Most charge controllers (xantrex included) kick back to 13.5v as soon as they hit a voltage of 14.4 at their end of the terminal. Not at the battery terminal. It will never bring the batteries up to a full charge. Well maybe in a month with no outside loads, but we are liveaboards!

So I am looking for any recommendations on chargers/charging options that are programmable (absorption & Float voltages) in order to properly charge these batteries to 100%. I realize now in this journey, big tanker batteries are really attractive when you think of all the power you will get OUT of them... When you start to understand what it will take to get the power back in, it becomes a different process.

[A potential loophole?]

The Statpower 40 (xantrex) that came with the boat has (as with most), switches to adjust the voltage of the absorption/float charge based on temperature... If I put it to Flooded/Cold the Absorption/Float voltages are 14.8/13.9.... The bulk voltage is right, but the Float is .8v too high.



What to do.... what to do....

Thank you for any advice you can give.

Best!!

[botanybay]

Great and important question, especially with such a large bank.

Most of the modern chargers have the ability to remotely monitor the battery terminal voltage rather than measuring the charge voltage at the chargers terminals. If the difference between the terminal voltage on the charger and the "voltage sense" wires becomes too large these chargers will declare an error and self protect to avoid doing something evil (i.e. the sense wire gets disconnected so the charger thinks the voltage is too low and keeps increasing the voltage to try and get the sense wire up to the desired voltage).

You can charge this bank at as much as 350 amps which would require ~6000 watts or a 50Amp at 120v shore circuit. You don't have to charge this fast but that is the maximum limit.

A small charger may exceed its internal time outs for bulk or absorption mode and assume there is something wrong and turn off. Make sure that the charger is either large enough OR that the timeouts are defeatable. (Often these are something like 10 hours). As an example, if you are 50% discharged then 870ah plus inefficiencies so perhaps 1000ah need to be replaced. With a 50 amp charger this would take at least 20 hours. If the bank does not get to 14.8v within 10 hours some chargers will kick out with an error assuming a bad battery and trying to avoid thermal run-away (yes thermal run-away is possible in a wet cell, boiling the acid and making a mess)

Also note that for equalization you will either need a large charger OR unique programming OR the ability to equalize parts of the bank at a time. I don't know what the recommended equalization rate for L16's is but if it is 8% of the capacity is required to equalize that would be 150amps @ 16V which is a pretty large charger.

I have been extremely happy with the Victron Skylla-I charger I installed on Botany Bay. Very small and very powerful (100 amps @ 24V in a ~12lbs package). However, it appears you are running a 12V system and these are only available as 24V models.

Victron's Pheonix line goes to 50 amps with a microprocessor control like the Skylla-i. At least on my system, the "storage mode" is wonderful. After a full charge it drops the voltage a bit to reduce water consumption and provides all of the house loads (I am a liveaboard also). These chargers are impressive in that even with the inverter kicking in and consuming 50-80% of the charger capacity the voltage never drops and the voltage remains in storage mode.

Once per week the voltage is brought back up to absorption levels (14.8 in your case) if it has not happened for other reasons to keep the batteries topped up.

Also, for world cruising you want a charger with "universal input", these chargers operate on 90v to 265v and will work with 50hz or 60hz power without an issue. So, just plug it into shore power and charge pretty much anywhere on the planet.

I would check with Victron with regard to paralleling more than one of these chargers. I don't see any reason it would not work correctly but they would not know about each other and so one of the chargers might decide to go from bulk to absorption or absorption to float a bit earlier. Nothing bad will happen just that one might drop out of float more quickly or get confused about if it can stay in storage mode.

There is also the "Centaur" range of chargers which are not computer controlled, do not have "storage mode", and so may be more easily paralleled. These chargers are also "universal input" (90v - 265v / 50hz or 60hz) and are available in up to 100amps at 12v. These are also heavier chargers.

I am just a very happy user of Victron equipment, no ties to the company or any distributor. I am sure there are many other options, these are the ones which I have looked into recently for my system.

[Stumble]

For a bank this large I am tempted to recommend LIFEPO4's. I looked at them a while ago but they are still somewhat in beta versions. The issue as I see it is that with a bank this large your float stage is going to go on forever. It very well may not be possible to ever get these things back to full with a normal battery charger and live aboard loads once the batteries drop below 80%. Living with batteries that never make it back to full charge is a sure way to sulfate them in a hurry, and kill the long term life of the batteries in a hurry.

LIFEPO's however would allow much faster bulk charging (though I doubt you can find that much dockside power). But more importantly would allow you to charge at bulk rates until 100%.

Secondly, I am curious why you want this large of a battery pack. With this much solar you should Be pretty much free from power worries and if you are planning on running AC from an inverter, a small generator would likely be a better option.

[Tx J]

You might consider splitting the "behemoth" bank into two or three banks. I know 'bigger bank is better', but the downsized pieces are still pretty good sized house banks for a 46' boat.

Your charge regime would become much more manageable and practical WRT input/output devices/demands, at the cost of some added complexity. But then you also gain some redundancy; so like everything, some tradeoffs required.

[jordiebsocal]

Thank you guys for the replies! I am looking into 100A chargers and splitting the bank. Two big banks I can charge is better than one big one I can not. Thanks for the insight!!!

[u4ea32]

Splitting into two banks for charging does seem like a good idea

[DeepFrz]

It might seem so on the surface but it really isn't. It is really best to keep it in one bank. Just make sure you have the charging resources to keep them well looked after.

[smac999]

weather you drain 500ah out of a 1700ah bank, 500ah out of 1/2 of a 1700ah bank, or 250ah out of each 1/2 of a 1700ah bank. you still need to put 500ah back in...

one bank. lots of chargers. the mastervolt 100a chargers are good. probably a good idea to have a charger / inverter in there too. a 2800watt magnam is a 120a charger.

what is your gen and shore power like? if you only have 30a then your charging will be limited by that. only good for 200a if you turn everything else off.

[botanybay]

Originally Posted by DeepFrz

It might seem so on the surface but it really isn't. It is really best to keep it in one bank. Just make sure you have the charging resources to keep them well looked after.

I was not suggesting running the bank in pieces, rather being able to equalize it in pieces.

Too bad the bank is not 24V, then I would recommend the Victron Skylla-i chargers as they talk to each other and so could parallel a couple of those and have about the right amount of capability.

[botanybay]

Interesting thought, the Victron inverter/chargers are parallelable. You loose the ability to have wide voltage range input (the inverter is restricting the range of acceptable voltage)

The multiplus 3kva outputs 120A per device, Three of them would provide a 360A charger which would be just about right.

The nice thing is it would provide a highly redundant inverter system as you could turn two of them off when underway and only run 3kva of inverter when needed, having two spares.

Unfortunately the internal logic keeps all three online if they are all turned on and so the idling current of the 3 units would be three times as much for a single unit.

The Quattro 5kva (12v 120v 60hz) unit has a 200 amp charger and so two of those units would get you to 400amps of charge capacity.

Each charger would consume about 3600 watts when running flat out which would be 7200 watts on the AC side. Or about 60 amps of 120V AC power.

However, a 50A 120V service could provide about 330A of charge at 15V and at lower voltage it would provide more.

For overseas, you would need to use a stepdown transformer to take 230V down to 115. The inverter will happily follow the frequency.

The nice thing with the Quattro is that it has two inputs and so if there is a generator aboard it does not need a separate transfer switch as both shore and generator are run into separate inputs. However, it looks like you are not planning on a generator at this point.