Battery Configuration

[alexandlorna]

Originally Posted by donradcliffe

Well, its not too clear what your question is, and this thread is now subdivided into at least 3 conversations...

In your case, you have two shiny new alternators on your Beta, probably internally regulated. Beta uses an Eastern European alternator and will sell you the "brush blocks" for these alternators so you can use them with external smart regulators. The voltage at the (internally regulated) alternators should rise to the 14.1-14.4 volt range soon after starting the engine, unless your batteries are seriously depleted.

The alternator outputs go to your 'splitter', which we don't know much about. The classic splitters are diode based, have big cooling fins on them, and drop the voltage about 0.6v There also some with more expensive diodes which drop the voltage about 0.3v. There are also some which are called 'combiners' which use relays and have no voltage drop. You need to measure the voltage at the alternators and then at the splitter output to see which kind you have. If you have a diode-based splitter, it will have the voltage drop regardless of the current, and you will need an externally sensed regulator in order to charge your batteries properly.

Thanks for that
I appreciate comments from anyone offering sound advice and am glad to see that my system is not fundamentally wrong wrong but simply needing tweaked in a few areas
I have a so called zero loss splitter , but definitely just dumb regulators so it seems what I need are smart regulators
I have also decided on a separate smart charger for the bow thruster bank , all as soon as the weather improves

[Charliemciver]

Hey y'all,

So after digesting the replies and a few measurements, here's my plan:

I'm going to run the bow thruster and windlass off a pair of batteries up front, on their own 'bank'. I need to move the windlass switchgear but that can be tackled on its own. I talked myself out of putting them on the starter bank because of the need to protect it, but also the current slow charge on that bank is fine but wouldn't be any longer. And I talked myself out of connecting them to the domestic circuit because it would complicate fitting the nasa battery management system because you can't get all the current in once place for the shunt. So 3 banks it is... 1 starter, 3 domestic, 2 windlass/bow thruster.

So, re charging the bow bank.... My 120A alternator currently kicks out 14.9V before going through a diode splitter and charges at the stern batteries at 14.1V. From replies here that's good enough (could be better at 14.4?). Up front though, that's down to 13.8V - not so good. If I'm putting the bow-thruster and windlass on their own bank I need to add/replace the diode splitter to get 3 banks. So I've bought the sterling power one advertised as low voltage drop in the hope it's a lower drop. Sterling is a lot cheaper than Mastervolt (what's currently fitted)!!! I'm hoping a lower drop is realised and I can get the front up to 14.1. Hope. I hope it works because I'm not sure I can bring myself to run a shore charger from an inverter, and don't really want to run the 240V wiring for that either.

The next topic is then the shore power charging of the bow bank... My mastervolt charger would likely be doing a poor job of charging the bow batteries too. It advertises that it compensates for wire loss but that sounds unlikely - how would it know how much!!!!? But it too has a setting where it can increase the voltage by 0.7V to compensate for diode drop (it currently connects direct) so I'm hoping to use the same trick.... Use a lower loss diode thing to the front battery. And the current mastervolt diode to the stern bank and everyone hopefully will be happy.

Is there any reason I can't connect the alternator AND shore charger to the input side of the diode splitter??? Nothing daft where the alternator will damage my charger flow or vice versa??

I'm torn then about which batteries to use where. I've paid slot for the 2 Lifeline AGM batteries intended for the domestic set. Sure, the safety angle says put them up front for the bow thruster/windlass to eliminate any chance of venting hydrogen into a cabin' and also they get thrown about a bit more up there... But they'll be so rarely used!!! I'm loathed to buy a 3rd to make my new domestic bank 'pure' (but would if highly recommended). The lifeline literature shows their heritage and engineering in their batteries, I hope it's not just marketing waffle. The specs on the lifeline and Numax aren't wildly different but wonder how they'll respond over time.

Any comments welcome, I'll be sure to post my progress

[nigel1]

Hi Charlie

My set up at present is similar to what you are proposing, 3 banks.
For Charging I have
Sterling Ultra 60Amp 3 Outputs
Alternator which goes to a Sterling No Loss 3 Output Splitter
Solar panels and a Blue Skys 3024 Controller
D400 Wind Geny with its own controller

The No loss splitter outputs to all 3 banks.

For the forward battery bank, the charge cables from all three sources connect to a common bus bar, and from the bus bar, a single suitable sized cable goes to the forward bank (circuit breakers and fuses are fitted along the way to protect the cables)
For the single cable going from the bus bar to the forward bank, I used 50mm2 cable.
I have checked voltage across terminals on the forward bank and compared to the output voltage from the charge source, and have no voltage loss.
I have not had any problems with the charge sources connected at a common bus bar.

For my domestic bank, all four charge sources are connected at a common bus bar.

[sailinglegend]

There's a lot of good advice on here, but I'm not sure you have taken it on board!!! Have you also searched other threads on this forum - all the answers you need can easily be found.

Originally Posted by Charliemciver

My 120A alternator currently kicks out 14.9V before going through a diode splitter and charges at the stern batteries at 14.1V. From replies here that's good enough (could be better at 14.4?).

This is your biggest mistake. Nobody here all elsewhere who knows what they are talking about will ever say "14.1v - that's good enough"! Lifeline AGMs need 14.6v - according to new advice from Lifeline. For a decent battery life you must always go with what the battery manufacturer says - not what people here say.

Originally Posted by Charliemciver

....I talked myself out of connecting them to the domestic circuit because it would complicate fitting the nasa battery management system because you can't get all the current in once place for the shunt....

Again, the can't be bothered syndrome - "it would complicate fitting the nasa battery management system..."

I have 5 batteries distributed around the boat, all with 2/0 cables of roughly the same length and all coming back to ONE bus bar which you could place be midships. Then the shunt and ALL charging goes via this busbar. I have a 120 AMP AC shorepower, 2 x 100 amp alternators, and a 280 amp DC genny. The Bowthruster batteries can then be on a manual or auto dis-connect switch - if they get used as little as you suggest the Ahs are being wasted. The windlass battery can be permanently connected to the domestic bank.

Originally Posted by Charliemciver

....So 3 banks it is... 1 starter, 3 domestic, 2 windlass/bow thruster.

Putting ALL batteries together in one domestic bank can make a huge difference, but it will take a bit of engineering. Here is a copy of a posting I did elsewhere:

One Big Bank Better Than Two Small Banks?

In the past it was often popular to have two service banks and no starter battery. It was thought a smaller bank would charge quicker. Current thinking is that it is much more efficient to have just one large service bank and a much smaller starter battery.


1. Doubling the service bank size means the life cycle is longer as the DoD is unlikely to fall so close to 50% so often. Life cycle at 50% DoD may be 1000 charge and discharge cycles. At a DoD of only 25% the life cycle may be 2500 or more.

2. Doubling the service bank size also means the “apparent capacity” is greater. Peukert’s law says that the apparent Ah size of a bank changes depending on the current draw.

A bank is designed to deliver a capacity with a current discharge that will flatten the battery in 20 hours. (The 20 hour rate)

So with a 100Ah battery, a 5A load will flatten the battery to 10.5v in 20 hours.

When drawing currents higher than 5 amps the "actual" bank size will be much smaller, so the bank will not last as long before it needs re-charging. Conversely when using much less than 5 amps the bank size will be larger and will deliver more Ah.

If a 100 Ah that battery has a Peukert value of 1.25, then higher or lower loads than 5 amps will change the actual capacity of the battery by the following amounts.

With a 10A load for 20 hours there are only 84Ah's in the bank.

With a 1A load for 20 hours there are 150Ah's in the bank.

3. Doubling the service bank size also means it will be more efficient and accept more Ah more quickly from all charging sources during the boost phase up to 80%.

It takes a bit of very over-simplified maths to prove the point, but a 100 Ah battery that is discharged to 50% may accept 20Ah in the first hour during the boosts stage, maybe 10Ah in the second hour during the start of the less efficient absorption phase, and the remaining 20Ah in another 5 hour. Doubling the battery size to 200Ah, with the same charging source of 20 amps, will accept 10Ah into each battery in 1 hour, that’s 20Ah into the bank. In the second hours it will store another 20Ah. That’s 40Ah replaced in two hours, as compared to 30Ah with a single bank. In the 3rd hour it may still accept 20 amps into the bank because a single battery in the start of the absorption phase could accept 10 amps. That’s 60Ah in three hours.The key point is that for two hours it is still in the more efficient boost stage where the battery is taking all the current the charge source can give it. Note that the initial boost charging stage has captured 40Ah in two hours, and 60 Ah in three hours. With the smaller bank it could only capture 20Ah in the first hour during boost and 30Ah after the second hour during the start of absorption. The third hour may add another 5 amps. That’s 35Ah with one batteries and 60Ah with two batteries. So a bigger bank will be more efficient and accept more Ah more quickly from all charging sources.

Since a lot of the time we are only charging up to the absorption stage which is about 80-85% then this increase in stored Ah is significant.

4. If you have a larger bank - or many smaller batteries in one large bank, it is easy when they start failing to just disconnect the bad ones and run on the others as long as you can until you can replace the whole bank. This may also allow skippers to search around and find the batteries they really want - not just be forced to buy the local "rubbish" because they are desperate.

[mitiempo]

Originally Posted by nigel1

I have checked voltage across terminals on the forward bank and compared to the output voltage from the charge source, and have no voltage loss.
I have not had any problems with the charge sources connected at a common bus bar.

I agree with sailinglegend, the advice offered hasn't been taken.

Curious question though. In the above quote what was the alternator output when the voltage was compared? Voltage drop is current dependent. What might seem to be "no loss of voltage" at float stage can be very different when in bulk charge. Try comparing the voltage difference when the forward bank is at the 50% SOC level and you will see a large difference. Voltage is pressure and the lower the pressure the slower the bank will charge.

[Charliemciver]

Sailing legend.... So I'm not lazy and will do complicated stuff if there's advantage to be gained. Thanks for the additional information about bigger bank being better - I get it.

My comment around fitting the nasa battery management device... Don't mistake complication for laziness... They're not the same! Wouldn't I need to bring all the load back to the bus-bar too. Surely it then makes the point of distributing the batteries only then one of convenience - you lose the benefit of placing load near the capacity? Or did I misunderstand?

And point accepted about 14.6 being better. I'll see what the drop over the Sterling device is and see if I can get it closer to that. I hope to be able to.

[Charliemciver]

Originally Posted by mitiempo

Curious question though. In the above quote what was the alternator output when the voltage was compared? Voltage drop is current dependent. What might seem to be "no loss of voltage" at float stage can be very different when in bulk charge. Try comparing the voltage difference when the forward bank is at the 50% SOC level and you will see a large difference. Voltage is pressure and the lower the pressure the slower the bank will charge.

The 13.8 reading was taken after a few mins of alternator charge - but these batteries haven't been charged for 3 months but also not been used much (previous owner had no charging to them).... I suspect taking moderate charge only but I need to get a meter in there.

[Charliemciver]

One more question... The lifeline manuals do seem to support charging at high voltage... So that would suggest putting my 14.9v alternator output direct to the battery for best effect. I can't find similar manufacturer data for the sealed lead acid Numax's... Will they be happy with such a high voltage too?

[nigel1]

Originally Posted by mitiempo

I agree with sailinglegend, the advice offered hasn't been taken.

Curious question though. In the above quote what was the alternator output when the voltage was compared? Voltage drop is current dependent. What might seem to be "no loss of voltage" at float stage can be very different when in bulk charge. Try comparing the voltage difference when the forward bank is at the 50% SOC level and you will see a large difference. Voltage is pressure and the lower the pressure the slower the bank will charge.

I dont think the forward bank has ever reached 50% SOC. In fact, to me, the forward battery bank is virtually wasted as the bow thruster only sees a few minutes use each year, which is why I intend to connect the forward bank to the domestic bank. That will have to wait until the batteries are ready for replacement as I do not want to mix batteries of different ages and make
To sort of answer your question, I guess the forward bank was in float charge when I tested them, but I could go back and try to run them down a bit and then compare the output voltage with the voltage at the battery terminals.

A question for sailing legend, what is the greatest distance between batteries you have.
My plan is to connect the fwd bank with the aft bank (cable run of about 9 meters), and have the domestic feed from the forward set of battereis and
the connection from ground connected to the aft set of batteries.

[sailinglegend]

Originally Posted by Charliemciver

...Wouldn't I need to bring all the load back to the bus-bar too. Surely it then makes the point of distributing the batteries only then one of convenience - you lose the benefit of placing load near the capacity? Or did I misunderstand?...

Yes bring all loads to the mid position bus bar. It's all about balancing the charging AND the loading. If the cables are big enough then neither suffers.

Originally Posted by nigel1

....what is the greatest distance between batteries you have.
My plan is to connect the fwd bank with the aft bank (cable run of about 9 meters), and have the domestic feed from the forward set of battereis and
the connection from ground connected to the aft set of batteries.

Each of my batteries are about 3 metres from the bus bar. Each battery has a positive and negative 2/0 cable (72 sqmm) connected to the central bus bar so all batteries are balanced. You are correct in trying to balance the load - but balancing the charging, where currents and therefore voltage drops will be bigger, is more important.