Charging 3 battery banks with shore, engine, wind and solar

[gpeacock]

Ive spent a bunch of time searching past threads and am now only more confused so I will ask what I thought would be a simple question.
Here is the current setup on my boat (43ft sailboat):
1 House bank (4 6V gel bats 400 AH)
1 Starter bank (1 12 V 1000 CCA FLA)
1 windlass bank (2 6V gel bats) direct connected to House Bank via 1/0 wire (50 ft return length)
1 High output alternator (100A) connected to house via bamar regulator
1 OEM 50A alternator connected to starter via internal reg
Freedom 15 charger/inverter connected to House bank
Old 5A 3 stage charger connected to Start bank

Im about to buy new AGM batteries and a bow thruster. I will also be adding solar and possibly wind. I want to keep charging simple but also maximize efficiency. Plugging in at a marina is soon to be infrequent.
Here is what Im thinking of changing:
1 House bank (4 6V AGM 440 AH total)
1 Starter bat (1 12 V AGM meant for starting)
1 Windlass/Bow thruster bank (1 or 2 12 V AGM starting or deep cycle)
2 High output alternators (100A each) connected to house via bamar regulators.
Freedom 15 charger/inverter connected to house bank
Solar/wind controlers connected to house bank with MPPT
Built in echo charger on freedom connected to Start bank

Questions:
How do I charge the Forward Bank now that I am adding a Bow thruster. (direct connect, ACR or echo/duo or sterling).
Should I consider switching the forward bank to Start Bat sype (still agm)
By charging mostly by alternator, solar and wind there are good chances of long acceptance periods on the house bank. Should I consider something different to charge the Start bank given that the Echo charger will only follow the voltage of the house.

Sorry again if this has been posted somewhere else... I cant seem to find a clear answer. Im about to spend a bunch of "doh" on batteries and I want them to last.
Thanks everyone
Gary

[DeepFrz]

You can use an echo/duo charge unit for both start and windlass batteries (from the house bank). The start battery requires very little to recharge it after a normal start. Connect both your alternators to the house bank and use current limiting setting in their respective regulators to protect them.

[ebaugh]

Deep had perfect advice, maybe more for my own clarification than anyone's...

Balmar's Digital Duo Charge does more than connect two banks for charging, it's a 30A DC-DC converter, charge relay and charge controller all in one. Had to read the specs to understand this. So one for the start battery, one for the thruster battery since the temperature and voltage drop for each requires different settings to get full charge. You can also use different battery chemistries as desired.

If you go this route, don't use the echo charge output of the freedom. All charging sources are connected to the house bank.

[mcarling]

I agree with DeepFrz and ebaugh about the Balmar Duo Charge.

I would not buy AGM batteries. I would buy lithium phosphate (LiFePO4) batteries. Smaller size, lower weight, longer life, safer, more stable voltage.

[sailinglegend]

Originally Posted by ebaugh

.........Balmar's Digital Duo Charge does more than connect two banks for charging, it's a 30A DC-DC converter, charge relay and charge controller all in one......

To be absolutely clear on this - the Balmar DuoCharge is not a multi-stage charge controller so it doesn't drop to float when the destination battery is fully charged, it follows the source voltage like the EchoCharge. The Balmar is however "Smart" in that it can set the output voltage, including the float voltage - to suit the destination battery type. I have only last week had extensive exchange of emails on this with Balmar.

[sailinglegend]

Originally Posted by gpeacock

Iive spent a bunch of time searching past threads and am now only more confused ....I'm about to spend a bunch of "doh" on batteries and I want them to last.....Gary

You seem to have done your homework but this is an incredibly complex subject, and pulling together everyone’s different ideas only makes it harder – if not impossible. Someone may tell you their setup has worked for them for 5 years – but could it have worked better and lasted longer if they had done it slightly differently? You will have seen lots of different suggestions and disagreements on these forums, and even industry experts like Nigel Calder and Mr Sterling disagree, but eventually YOU have to decide.
This difference in knowledge was highlighted yesterday for me at the boat show">London Boat show. Firstly there were only two stands offering electrical products, one a well respected battery and power solutions company, and the other a solar/wind company – with a picture of a yacht at anchor on the front cover of their glossy brochure. This company was giving a lecture on the World Cruising Club stand about power management on board – exactly the kind of questions you need answering. I approached him before the talk and started to ask probing questions about battery size and charging – he was very defensive of his ideas and questioned my set-up. After a while he refused to talk to me anymore, despite my protests. Fair enough he’s trying to sell his products, but he was not willing to help me – and I wanted to buy an MPPT regulator. He was also trying to sell Solar AGM standby batteries for Marine applications! The other Power Solutions company I spoke to with the same questions could not have been more helpful and there was nothing that we did not agree on, even some of my probing questions about regulators and charging.

So why is it so hard to get the right information at a major Boat Show?

If I could offer some brief thoughts at this stage:

1. Why do you need a bowthruster if most of the time you will be at anchor? Those batteries are only being wasted most of the time.
2. Your windlass battery could be used for the bowthruster, but would need to be big enough for both jobs. Keep it the same type as the House.
3. Combine the windlass and house batteries as your 440 Ah capacity is not big enough. If you do this then you could position the batteries all together and increase the size of your cable to the windlass. Add another the same size or replace with a 2/0 cable. Or you could keep the weight in the bow – or half way between. You could also fit a relay to disconnect the bowthruster battery when that is switch on, the rest of the time the relay will join both banks together for charging/discharge. Batteries for one bank can be placed anywhere as long as the cables are large enough to cause no volt drop when charging and discharging. The current in/out must be balanced for each batteries. This is achievable with some thought and basic engineering.
4. Get a small Odyssey or Red Flash AGM for the starter and lie on its side somewhere out of the way. Charge this with a 5 watt Solar Panel only, or use the EchoCharge if you have to, but have a switch in series to isolate the charging when YOU know the batteries are charged and could be gassing – this WILL happen after a long period at an absorption voltage – especially with a large house bank where the regulator should be set to extend the absorption time so that the batteries do not drop to float too early.
5. Make sure the AGM batteries you buy are “Marine” AGMs for deep cycle use – not a Hybrid designed as much for their starting power, or as standby Solar batteries. There are only a very few brands that are designed for falling off a three meter wave.

I hope you get some useful feedback here that allows you to come to a conclusion as to what you think would be best for your lifestyle. This could involve major re-organization of the boat and should not be dismissed as “too much work”.

[ebaugh]

Originally Posted by sailinglegend

To be absolutely clear on this - the Balmar DuoCharge is not a multi-stage charge controller so it doesn't drop to float when the destination battery is fully charged, it follows the source voltage like the EchoCharge. The Balmar is however "Smart" in that it can set the output voltage, including the float voltage - to suit the destination battery type. I have only last week had extensive exchange of emails on this with Balmar.

So it's not at all intelligent? If all it does is a fixed voltage adjustment, that's not a good solution. After several days at anchor, the aux batteries would probably get overcharged. Someone should make such a charger. Otherwise you have to use an AC charger off the inverter and that's not terribly efficient.....

Combining the banks is a good choice if there is sufficient space to do so. Buy it won't work if they are separated by any significant distance.

[mcarling]

Originally Posted by ebaugh

Combining the banks is a good choice if there is sufficient space to do so. Bu[t] it won't work if they are separated by any significant distance.

What is the failure mode if two battery banks separated by some distance are combined?

[hellosailor]

I'd expect "any significant distance" means there will be a significant voltage drop in the cables, or the cables will be so thick as to cost a bloody fortune. Aside from that you may want to fuse them at both ends, since a fire in a primary battery cable can really ruin your day.

I'd also suggest that since there is no consensus on how to charge and monitor LiFEPO4 batteries, the OP ignore them completely. The only thing anyone agrees on, at this point, is that either you need to pay lots of attention to manually supervising them, or spend lots of money on a BMS system that does. Not the way to go for someone who is asking "basic" questions about building a simple and robust system.

[mcarling]

Originally Posted by hellosailor

I'd expect "any significant distance" means there will be a significant voltage drop in the cables, or the cables will be so thick as to cost a bloody fortune.

With batteries at both ends, where do you expect the voltage drop to be manifest? The only problem I see is that the resistance of the cables would limit the speed and efficiency at which the batteries would otherwise tend to balance each other. To the extent that there might be an imbalance and the cables were thin, some of the energy would be converted to heat and wasted. However, if there is a particular distance between the power source (solar or generator or whatever) and the load (windlass, for example), then it isn't clear that locating the batteries nearer to one or the other (or even splitting them) will necessarily be less efficient. I would be more worried about increasing the overall length of the run from source to load.

Originally Posted by hellosailor

Aside from that you may want to fuse them at both ends, since a fire in a primary battery cable can really ruin your day.

Good advice.

Originally Posted by hellosailor

I'd also suggest that since there is no consensus on how to charge and monitor LiFEPO4 batteries, the OP ignore them completely. The only thing anyone agrees on, at this point, is that either you need to pay lots of attention to manually supervising them, or spend lots of money on a BMS system that does.

I don't agree that LiFePO4 batteries need any more supervision than lead acid, gel, or AGM batteries.

[Andina Marie]

With multiple batteries and charging sources, a couple of Combiners would solve the problems. The Combiner100 will handle charging sources rated up to 100 amps so one between the starting battery and house battery, plus one between the house and windlass battery would do the job for under $60 each at some retailers.

Since they are bi-directional you can leave the charging sorces as they are now.

Echo chargers and duo chargers are not needed, the sorce voltages are already regulated and all they do is limit the current available. An Echo charger can only supply 15 amps so it would take 4 to 6 times longer than a Combiner100.

You don't have to worry about resistance in long wire runs, voltage drop is not a concern because it is current that charges a battery and as the battery approaches full charge its voltage rises and the current drops. As the current drops so does the voltage drop along the wire untill the current approaches zero and so does the voltage drop. The wire resistance may add a few minutes to charging time due to slightly less current flowing.

[ebaugh]

Originally Posted by mcarling

What is the failure mode if two battery banks separated by some distance are combined?

If separated by distance, the distant bank will see both different temperatures and voltages. The OP seems to be asking how to optimally charge two separated banks and that's not possible with a long distance at 12V on a common connection. It will work... but usually the far bank won't see proper absorption voltage and never get fully charged shortening the useful life of the distant battery.

Battery chemistry won't solve the problem completely. AGM and Lead need to be fully charged. I have no experience with Gel. LiFePO4 would do better on a common connection since there is no need to ever fully charge them to prolong life and temperature is not a factor in charging, but it does pose a more complicated engineering solution.

The cheapest solution over a short timeframe, call it less than 5 years for discussion and probably longer, is to use lead acid for for everything. Since the thruster/windlass batteries won't see the cycles of the house bank, they still should last a reasonable amount of time and are relatively inexpensive to replace. It's not optimal, but perhaps practical, and uses a lot of the existing infrastructure. Just be sure to use commonly available battery sizes.

Combining them is the best answer, if the logistics allow for it. Especially since you get a bigger house bank and 4 golf carts is kinda small if there is a refrigeration system drawing on the house bank and you are mindful of the 50% discharge rule.

[ebaugh]

Originally Posted by Andina Marie

With multiple batteries and charging sources, a couple of Combiners would solve the problems. The Combiner100 will handle charging sources rated up to 100 amps so one between the starting battery and house battery, plus one between the house and windlass battery would do the job for under $60 each at some retailers.

Since they are bi-directional you can leave the charging sorces as they are now.

Echo chargers and duo chargers are not needed, the sorce voltages are already regulated and all they do is limit the current available. An Echo charger can only supply 15 amps so it would take 4 to 6 times longer than a Combiner100.

You don't have to worry about resistance in long wire runs, voltage drop is not a concern because it is current that charges a battery and as the battery approaches full charge its voltage rises and the current drops. As the current drops so does the voltage drop along the wire untill the current approaches zero and so does the voltage drop. The wire resistance may add a few minutes to charging time due to slightly less current flowing.

I think you are the person who originally designed the first automated battery combiner...so you are certainly qualified to answer this question.

Let's use this example, but make the house bank 1000Ah to emphasize my point. Assume the engine battery is fully charged and the house bank is down 20-30%. The sun starts shining and my solar controller is properly programmed for several hours of absorption charge since the charge rate is especially slow. And we soon see the proper 14.4V absorption for quite some length of time. Won't that potentially boil the engine start battery since it's already fully charged?

[donradcliffe]

KISS and directly connect the windlass batteries and house bank-- with the long separation it isn't perfect, but you will find that one big bank is better than two small ones. At the acceptance current flows, the 1/0 cable will have a very low voltage drop, so the solar/wind power will keep them topped up.

[hellosailor]

"voltage drop is not a concern because"
that could give folks the misimpression that all the 3-stage chargers that are VOLTAGE POINT based, are wrong. Perhaps better to say that within certain limits, a certain amount of voltage drop is not a stopper. That would depend on the voltages and the drops and other issues, like whether you care about a battery possibly not seeing the last 10 or 20% charge because it was "only" one or two tenths of a volt low. Wouldn't it?