Battery Banks and Charging

[cwyckham]

Originally Posted by msponer

Sorry, I don't mean to be offensive or cause a nerd fight.

Yes, calling it a relay is an oversimplification. It is of course a voltage following device.

I felt like the gentleman who was using it to mix his "AGM and VRLA batteries" is misunderstanding what the device is, and possibly doing something wrong with it (depending on what kind of VRLA battery he has), but I did not feel like going into a long and technical exhaustive explanation. My gut feeling is that if someone does not understand the manual, then I have little confidence my ability to use the right words to get them to understand it from me better. So I thought the idea of "think of it as a relay" is concise and more helpful, even if it... is wrong on another level to people who know more.

I struggle with finding the balance between communicating in a direct and concise way that is what I feel is immediately understandable to the person I am talking to while also being considered correct to everyone else who could possibly read it. I sometimes feel like the best manners are to communicate on whatever level the conversation is at, but will stop doing that here, because it side tracked the conversation and added noise.

So that's what my whole meta conversation was about, that struggle or nuance within online manners. I did not mean to be rude or anything like that, I was mostly thinking about it as a kind of funny thing, like "Oh, look at the funny direction this conversation could go next." Within the other domains I think in, the idea that there are multiple levels is taken as a given, and it's usually considered best to be at the minimal level of abstraction to solve a problem. But I was was very wrong and misjudged the problem from "try to get someone to realize they might be making a mistake" to that plus "don't say anything that could be seen as an over simplification by other people."

I also apologize for being self indulgent with tangents about the meta conversation, cognitive styles, and our evolving culture and manners online, I need to keep those discussions elsewhere and not be off topic in a sailing community. Here they are just noise, especially because the playful and dispassionate tone I intended did not come through.

So... I'm sending happy vibes. Yes. You are right.

Well, I, for one enjoyed your pi conversation with yourself. I thought it was illuminating and amusing. That probably makes me an enormous geek, but I'm ok with that.

[Dockhead]

Originally Posted by msponer

Also, Dockhead, I take exception with your idea that it doesn't matter if the starter and house banks are the same type. In almost every case both battery banks should be the same type. One needs a separate charging system for each bank to have different types of batteries.

And I also believe that a completely separate alternator and dock side charging system for the starter battery is of dubious benefit, and is a needlessly complex solution to a problem that can be solved in a much more straightforward way than doubling the amount of charging wires, fan belts, DC fuses, AC breakers, charging boxes...

Well, everyone is entitled to his own opinion -- there is no bible for any of this stuff.

If you want to charge your house and start batteries using single charger and alternator without some complicated configuration like an echo charger, then you are correct -- they need to be the same size, type, age and condition. But a house bank which were the same size and type as your starting battery would be teeny tiny. This will work only for the smallest boats with the lightest electrical loads.

My house bank is eight (8) Trojan 105ah * 12v. That would be some starting bank, to duplicate that.

So once you need a house bank which is bigger than a starting battery, then you either have to have separate charging systems, OR you have to have a good way to separate the charge. The echo charger praised by many here is an elegant solution to that problem and there aren't many others -- to efficiently charge two banks of different size and type of batteries using the same charging source is difficult. The reason why the Echo Charger is so good, is that it actually is a separate charging system, it's just powered by the primary battery bank.

So separate charging systems are not actually all that much more complicated than a good charge splitting system, and you gain valuable redundancy and maximum efficiency, as each charging system can be exactly tailored to the bank it charges.

An engine start battery, especially one used for a diesel engine, is used in a completely different regime from a house bank, and a good deep cycle house battery is not well suited for the life of a starting battery. So an engine start battery doesn't need to be charged by a complicated three-stage regulated alternator. A simple car-type alternator works perfectly for this duty. And a start battery doesn't need a high powered three stage charger -- it only needs topping up and trickle charging. So separate charging systems for your start batt will be relatively cheap and simple -- the biggest problem for most will be where to mount the second alternator.

I don't have any choice on my boat, because the house bank is 24v and the engine and generator start circuits are 12v. So my boat was originally delivered with separate chargers and alternators. I am very happy to have the simplicity of not having to split any charges. And I am happy to have the redundancy. But to each his own, of course!

[goboatingnow]

Originally Posted by msponer

The Echo Charger is just a relay. It does not adjust the voltage, so you can't use it to mix batteries of different types.

The "sealed VRLA" thing is also off, but ... I don't want to get into a recursive conversational loop on disconnected trivia. a recursive conversational loop on disconnected trivia. a recursive conversational loop on disconnected trivia. a recursive conversational loop on disconnected trivia. a recursive conversational loop on disconnected trivia.

Haha

An echo charger is just a relay, I'm still laughing. ...

[goboatingnow]

Originally Posted by mitiempo

If 1-2-both switches can cause confusion why would you want 2 of them?

I can't see any advantage to 2 1-2-both switches over 1 assuming 2 banks.

One switch feeds the domestics from either battery 1 or battery 2. How do you switch the starter circuit. ? ( why another switch)

[Viking Sailor]

Originally Posted by hellosailor

Pat-
"2 [house] banks are recommended" WERE recommended. No longer are.
The new logic is that because batteries last longer when you don't cycle them as deeply, you put in the biggest house bank you can fit/afford. One house bank. And then you discharge cycle that as gently as you can, i.e. 30% before recharging, 50% if you must.
Then you have one separate SLI battery, small, cheap, easily replaceable, as your dedicated starting battery, used only for starting.
That way your starting battery is safely isolated, and if you kill it, you've still got that whopping big house bank to start from. The starting battery is no budget killer, and the house bank gets to be one big bank instead of two smaller banks, so it is discharged only half as far, and may last twice as long.
Charge cycling your house battery bank 30% instead of 50% may double or triple the battery life, depending on whose numbers you believe. Running it to 50% instead of 80%, easily doubling ot tripling the life. You wind up being able to store and use more kilowatts per dollar spent on battery, so the "new logic" about one house bank and one starting battery makes good sense.
The starting battery can be an SLI (starting) for economy, or a deep cycle that has enough power to start your engine, is you prefer the security of another deep cycle power source.

Let's see what the Depth of Discharge (DOD) would be for single and dual battery bank(s). Assuming a daily usage of 135 Ah and a total available capacity of 450 Ah (two 8D's).

The DOD for the single bank would be 135 Ah usage divided by 450 Ah capacity equals 30%.

Where as, with two banks of 225 Ah capacity each, the logical thing to do is divided the daily usage between the two banks (switching banks at noon). The the daily usage becomes 135 Ah usage divided by 2 banks or 67.5 Ah usage per bank. The DOD for each bank would be 67.5 Ah usage divided by 225 Ah capacity which equals 30%. Thus, the total DOD remains the same for both single and dual battery bank setups.

The real difference between a single and dual battery setups is that with a single battery bank recharging must be done while the battery is under load. This requires that the charging source must be capable of providing all the load current plus the charging current while providing a high enough voltage to completely charge the single battery.

Where as, with dual battery banks, each bank can be charged unloaded which results in a more complete and quicker charge. Thus, increasing the longevity of the batteries while maintaining the same DOD as the single bank setup.

[goboatingnow]

Originally Posted by msponer

Sorry, I don't mean to be offensive or cause a nerd fight.

Yes, calling it a relay is an oversimplification. It is of course a voltage following device.

I felt like the gentleman who was using it to mix his "AGM and VRLA batteries" is misunderstanding what the device is, and possibly doing something wrong with it (depending on what kind of VRLA battery he has), but I did not feel like going into a long and technical exhaustive explanation. My gut feeling is that if someone does not understand the manual, then I have little confidence my ability to use the right words to get them to understand it from me better. So I thought the idea of "think of it as a relay" is concise and more helpful, even if it... is wrong on another level to people who know more.

I struggle with finding the balance between communicating in a direct and concise way that is what I feel is immediately understandable to the person I am talking to while also being considered correct to everyone else who could possibly read it. I sometimes feel like the best manners are to communicate on whatever level the conversation is at, but will stop doing that here, because it side tracked the conversation and added noise.

So that's what my whole meta conversation was about, that struggle or nuance within online manners. I did not mean to be rude or anything like that, I was mostly thinking about it as a kind of funny thing, like "Oh, look at the funny direction this conversation could go next." Within the other domains I think in, the idea that there are multiple levels is taken as a given, and it's usually considered best to be at the minimal level of abstraction to solve a problem. But I was was very wrong and misjudged the problem from "try to get someone to realize they might be making a mistake" to that plus "don't say anything that could be seen as an over simplification by other people."

I also apologize for being self indulgent with tangents about the meta conversation, cognitive styles, and our evolving culture and manners online, I need to keep those discussions elsewhere and not be off topic in a sailing community. Here they are just noise, especially because the playful and dispassionate tone I intended did not come through.

So... I'm sending happy vibes. Yes. You are right.

I'm the gentleman I'm an electronics engineer with 25 years design experience must of it in power electronics.

I certainly understand the concept of echo charging. ( which is simply using a battery as a charging source). You on the other hand have written mountains of verbiage and obviously haven't a clue. ( as was pointed out to you )

It is quite acceptable to use echo charging to use one battery source to charge a different battery type. Obviously they should be the same technology ie LA bit there's no issues using echo charging to use a AGM set to charge say a sealed LA ( read sterlingpower manuals for enlightenment)

And word of advise , when you know nothing just read the posts.

[Rustic Charm]

Thanks Hellosailer, that makes sense to me. I currently have four house batteries but until I pulled the battery box out it was wired up for five. So If I understand you properly, should I increase it to say six house batteries, this would be better than four? With four, and my 6 year old girl watches a video at night, we seem to run the batteries down quite a bit.
Ted

[hellosailor]

Viking, the flaw in your logic is that your comparison also requires running the charging system TWICE AS OFTEN. Unless you deplete both banks, in which case there's little reason to have two. And since putting the last 5-10% of power back into any battery takes more than a linear pecent of recharging time, charging two banks again will take more than just twice as long or twice as often.

It ain't me, it is the whole industry that has changed logic from "two equal house banks" to "one whopping huge bank plus one SLI".

Ted, yes, six would be better than four, assuming they are all the same size. DO take a good look around, because sometimes there are odd battery sizes that you won't find at the warehouse clubs, which manage to make better use of a box. Taller, thinner, whatever. Limited of course by the size of what you can lug around.<G>

With six, you can also put in 3 pairs of 6-volt (i.e. inexpensive golf cart traction batteries) or six fork lift cells (2V each and damned robust) as well as the conventional combinations.

[Kettlewell]

DO take a good look around, because sometimes there are odd battery sizes that you won't find at the warehouse clubs, which manage to make better use of a box.

That's true, and I have struggled with trying to maximum capacity in the available space, but I have also come to the conclusion it is very worthwhile on a world cruiser to use some form factor that is readily available all over the world and may even be available from other cruisers. Batteries do go bad, and Murphy's Law means that they tend to do so when you aren't near a specialist battery shop. It's also good to have your bank designed so that it is very easy to reconfigure minus a battery or two and still give you the voltage you need. Imagine what would happen if you were using two L16 6-volt batteries for your main bank and one of them went bad. Suddenly you would only have 6 volts. One advantage of using standard car-size 12-volt batteries is that I have found that it is generally easy to find something you can use almost anywhere in the world, at least on a temporary basis. I suspect golf cart sized 6 volts are probably relatively easy to get, but nowhere near as easy as standard car-sized 12-volt ones.

[Viking Sailor]

Originally Posted by hellosailor

Viking, the flaw in your logic is that your comparison also requires running the charging system TWICE AS OFTEN. Unless you deplete both banks, in which case there's little reason to have two. And since putting the last 5-10% of power back into any battery takes more than a linear pecent of recharging time, charging two banks again will take more than just twice as long or twice as often.

It ain't me, it is the whole industry that has changed logic from "two equal house banks" to "one whopping huge bank plus one SLI".

The single house battery bank is great for sailboats that spend most of their life tied up in a marina, or that run their engine most of the time on passage. There is amble shore power available for charging and there is no fussing with switches. The battery just takes care of its self. And, if something should go wrong, there is the start battery with a enough juice to get the boat back to the marina.

However, for a cruising sailboat with more constant charging sources like solar, wind, and water, in addition to the engine and small generator, it is a very bad idea. These alternative charging sources supply a lower charging current but do so over a much longer time. If these sources are connected to a battery under load, most of the current will go into the load with very little going into the battery. Not a good thing! And, if one should find themself with a failed battery a 1000 miles from shore or cruising some remote part of the world they will still have a substantial backup system available. A good thing!

I wonder who is the intended customers are for those in the industry that advocate the single bank setup. It seems unlikely that they were trying to address the needs of cruising sailors when they came up with this scheme.

What amuses me the most is that the setup I have can be configured as either a single or dual battery bank system. Yet, be one switch throw away from a redundant system.

[msponer]

Originally Posted by Viking Sailor

What amuses me the most is that the setup I have can be configured as either a single or dual battery bank system. Yet, be one switch throw away from a redundant system.

This is an interesting thought, a way to deal with AGMs that need to be fully recharged regularly. I have read anecdotes that Lifeline AGMs, at least, will eventually be wrecked if they are not fully recharged about once a month.

I agree that having a second battery as a first class backup (that can charge from any source and power any source) is a good feature, and my personal preference. This is how I setup my boats. I feel it should be more common in this modern era where people have cited "batteries not charging" as a key factor in their decision to abandon ship. We've come very far from Tania Aebi carrying her car battery ashore to be recharged, and often arriving in port with a dead battery.

But... I disagree that there is any disadvantage to simultaneously charging and using lead-acid batteries. In fact, since charge efficiency isn't 100%, but 'usage efficiency' is 100% (haha), then it gives you a free efficiency gain to run the boat off of whatever charge current is available (around 10-20%). And, as another has said (who I take back calling a gentleman, haha), you also lose charge efficiency as the battery approaches full, because a smaller bank will accept less current than a larger one.

But you are right for other battery chemistries. I looked at other battery chemistries for a large robot that has periodic high loads while being continuously charged with a low current, and found no off the shelf charger that could handle loads being places on the battery while charging. Because these chemistries do not yield the easy natural equilibrium that lead-acid batteries have-- the algorithm for finding the state of charge is time and voltage, or time and temperature, based, and placing a load on it while it is being charged will alter the variables and screw up the algorithm. I was not, at least, able to find an off the shelf solution to this problem for NiMH batteries. So we took the weight hit and went with AGMs.

But, again, if the loss of efficiency don't bother you, then I really like the overall vibe of fully functional completely redundant battery banks-- that can run any load and be charged from any source. My own style is to have a very small (single battery) backup/starter bank, and throw the rest in the primary/house bank, but of course also see value in equal sized banks.

[hellosailor]

Kettle, sticking to standards can be a good thing, you're right. OTOH if you are in any place where there is "commerce" there are fork lifts, and the 2V fork lift cells will be available as well. Everything is a tradeoff, and in some places you'll only find wet lead car batteries--if that. Has to be considered against optimizing the whole system and the chance that sure, one day you may have to limp into the next port. Hopefully you'll be out of warranty, or else you'll have to look for the same brand as well.<G>

Viking-
" If these sources are connected to a battery under load, most of the current will go into the load with very little going into the battery." You've got some unique ideas there. If there's another load besides the batteries, it won't matter what your charging source is, the power will still flow "downhill". (Replace "downhill" with the electrical principle and Law of your choice.) In fact it would be BETTER if your charing source was supplying the non-battery load, since some 10% of any power applied to the batteries will be wasted in the charging process, but another load can use that power without waste.
Sure, redundant systems have advantages. that doesn't always make them inherently better in any way, it just makes them redundant.

[Rustic Charm]

Thanks everyone for your input.

Another question I have. I am now going to add two batteries to my current four and I'm going to make sure that each lead to the battery is the same length. In order to fit six matteries into the new box I'm going to make, they will be next to each other. Is there any problem in placing the batteries immediately side by side without any space between them? Or do they need air to circulate around them? Will they build up heat?

Ted

[mitiempo]

There should be a spacer between the batteries to allow some air between them. In a tight bank the middle battery is always the hottest. If you can, try and build a box with the space to do this.

[Uncle Bob]

Originally Posted by Kettlewell

Go Boating Now, that sounds like a good approach, though I like to be able to start using either the start battery or the house bank, and to be able to run the house with either the house bank or the start bank, without having to connect the two banks directly. The reason for this is that if you get a bad cell or a bad battery in one bank or the other you can instantly cut it out of service and go with the other bank without having to move batteries around or reattach cables, etc. I have had one battery short out internally offshore for some reason, and I was able to instantly switch over to running on the other bank while I sorted out the problem.

Basicly the way I have wired my boat.
I installed 2 of the 4 position perko switches- 1 for house power selecting from either bank and another for start and windlass also selecting from either bank.
Works well for me.