Mixing Amps on a House Bank?

[john61ct]

Originally Posted by skipmac

Yes you are 100% correct that a bad battery in a parallel system can discharge all the batteries BUT the odds of this happening in a properly maintained and monitored system using reasonable quality batteries is so small that it can be ignored.

Exactly.

[Terra Nova]

A bad battery in a parallel system can easily be isolated.

[hzcruiser]

Wow, that is a most unusual approach to the rather small chance of one batt/cell going bad in a parallel setup and dragging down the whole system within hours.
Let's face it: Most boats are 12V, the bigger ones 24V, and that's all DC. And here is a kiwi that says put all your batts in series an crank up the voltage, yay! Then step it back down to where you need 12V again. Are you for real?
So what is your bus voltage, please?

Originally Posted by SteveWrightNZ

In parallel, yes.

1.) Modern solar panel controllers will put out any voltage you tell them. They don't care.

Mine does care, it only puts out 12-14.6V, no matter how long I talk to it. I could've bought a 24V one, yes.

2.) Modern lighting solutions (LED?) don't care about the input volts.

My LEDs do. They want 12V and have a constant current regulator in them. Anything higher might only create heat and waste energy until the regulator blows. Thank you.

3.) Cheap regulators down to 12V are indeed cheap - a few dollars now, so throw a regulator at anything that MUST have 12V DC.

Yes, they are, for up to 1, 2 or 5 A. I can't hook my ham radio to 24V or 32V or 48V or 96V DC, mate! It needs a good 13.8V and up to 15A. And no, I'm not going to through out every piece of electronics in order to run it off 24V or 48V DC.

4.) Modern high-power inverters are much happier at a higher LT terminal voltage. 24V or 48V inverters are cheap and easy to find.

Correct, if you start from scratch you can buy one of those in the first place. But you cannot change the existing one to a higher input voltage.

You see where I'm going with all this? Use a higher battery terminal voltage by using series rather than parallel.

An interesting approach that has been done in maybe 1 out of 1000 boats? It must be that the other 999 are all sheep, or numbnuts?


As a final note, you might be aware that DC at higher voltages is lethal, even more so than AC? Suggesting anything above 24V DC might put a lot of lifes at risk, albeit not the lifes of your batts.

[Unregistered-1]

Originally Posted by Terra Nova

A bad battery in a parallel system can easily be isolated.

It would be somewhat better if that were engineered in.

But mostly, faults from parallel batteries are noticed when its too late. Inverter has shut down, engine won't start, VHF radio won't transmit - these are usually the first hint that something has gone bad. Are you happy with that?

[hzcruiser]

Originally Posted by john61ct

Once a bank gets below 75-80% residual capacity, time to scrap it.

They all tend to wear close to the same rate anyway, and the whole point of proactive management is avoiding any surprises.

Since I'm monitoring the current in/out, temp and voltage of every batt separately and all goes into a database, I can replace the weakest batt first. This also avoids any surprises as one can see from the history how each batt fares.
In an ideal world they would wear at the same rate, yet we have seen several threads as how to actually do the wiring properly.

Personally, I prefer to use my batts much longer than their 75% residual capacity and replace them when it suits my budget or the port I'm in.

[noelex 77]

Originally Posted by SteveWrightNZ

Install series strings of identical batteries for the required capacity or to take up the available space, and THEN alter charging and inverter schemes to match terminal voltage.

Steve, you certainly have a unique way of wiring boat systems that I have never seen before on our sized yachts. Being different does not make it wrong, although doing things differently does create its own problems.

One issue is that you seem to miscalculating the AHrs and WHrs at different voltages. This may just be a typo, but it is common mistake. A simple way to think about the issue is no matter how the battery pack is wired, the totally energy storage does not change. There is no extra energy storage created by wiring the batteries differently and increasing the voltage.

I gather your system is a high voltage house bank with a combination of inverters increasing the voltage for some appliances, and DC to DC converters dropping the voltage for some appliances. There are some potential advantages, but also disadvantages. It could be an appealing option for a boat with electric drive (was this the primary motivation?).

Some more details would be interesting. What is the voltage? How many inverters and DC to DC converters are used? What systems run from 12v, what systems run directly from the higher battery voltage and what systems use the inverter ? Etc.

[Unregistered-1]

Originally Posted by noelex 77

One issue is that you seem to miscalculating the AHrs and WHrs at different voltages. This may just be a typo, but it is common mistake. A simple way to think about the issue is no matter how the battery pack is wired, the totally energy storage does not change. There is no extra energy storage created by wiring the batteries differently and increasing the voltage.

Yes, typo. Agree completely. I just couldn't be bothered fixing it, and also it would separate the thinkers from the talkers and that saved me the job.

Originally Posted by noelex 77

I gather your system is a high voltage house bank with a combination of inverters increasing the voltage for some appliances, and DC to DC converters dropping the voltage for some appliances. There are some potential advantages, but also disadvantages. It could be an appealing option for a boat with electric drive (was this the primary motivation?).

No. The primary motivation was to reduce risk and complexity, and give me what I want. However, the system does lend itself nicely to additional sources. For example, there was nothing stopping me adding a shaft generator and running it in parallel with the solar array. Also, many of these units have a dedicated wind turbine input.

Originally Posted by noelex 77

Some more details would be interesting. What is the voltage? How many inverters and DC to DC converters are used? What systems run from 12v, what systems run directly from the higher battery voltage and what systems use the inverter ? Etc.

The example is hypothetical, in that the design principle is reusable anywhere.

When I'm designing I always ignore the facts, preconceived ideas, conventional thinking, and start with two words, and those words are "I want".

So what do you want?

"I want" an espresso machine on a timer (5am to 11am), a washing machine, safety, redundancy, and serenity.

At first glance, a kilowatt of solar, 10KWh of usable storage (big cells in series), a pair of auto failover hybrid 5KVA controllers should do it. Battery system terminal voltage is irrelevant as long as it's compatible with the hybrids. The biggest problem is mounting the solar and the batteries.

All appliances will be 230VAC. Nothing is custom. It's uncomplicated and I get everything I want - like I am used to.

edit:

If I lose a cell underway, I do... nothing.
If I lose a panel, I do, er, nothing.
If I lose a charger, or inverter, I don't do anything.

If I lose ALL of the above, I do nothing. I don't touch a thing. Everything keeps working.

Cool ay.

[skipmac]

Originally Posted by SteveWrightNZ

It would be somewhat better if that were engineered in.

But mostly, faults from parallel batteries are noticed when its too late. Inverter has shut down, engine won't start, VHF radio won't transmit - these are usually the first hint that something has gone bad. Are you happy with that?

All reasons why the optimal setup has a separated, isolated start battery. Then IF something happens with house bank the engine can be started and any emergency gear like the VHF, bilge pumps, etc can run off that battery until the issue with the house bank can be sorted.

Much cheaper, easier and more elegant solution to the potential problem.

[ranger58sb]

Originally Posted by SteveWrightNZ

Paralleling any cell with another revisits the same problem.

Any problem with one cell will take down another parallel cell immediately.


You can't dodge that. Don't do it.

Easy to say, perhaps easier with a new boat being built to your specs.

But "used" boats often comes with 12VDC systems, X number of batteries in Y amount of (limited) space to feed Z 12V things, wiring all over the place sized for 12V... with maybe no room for reasonable solar...

And with separated start and house batteries... and sometimes gensets with their own start battery, so engines can run and AC appliances can work in the meantime...

(Plus, sailors can even make boats move with those fabric things they carry around...)

And even a hosed-up parallel battery system can often be fixed at the next port...

So in the grand scheme of things, when "practical" versus "theoretically perfect"... I think I'll chose "pretty good" over "painful." And I'll go boating.

And if something goes south sometime, I'll fix it.

-Chris

[john61ct]

Originally Posted by SteveWrightNZ

But mostly, faults from parallel batteries are noticed when its too late.

Again, bulldust.

As owner, I will notice from my monitoring a decline in residual capacity, longer Absorbtion time before endAmps, quicker voltage drops under load, etc

long before the bank is likely to fail.

Any faulty cells from the factory would have been revealed by the lengthy commissioning protocol, or during the breaking in period.

Proper care and monitoring systems means no surprises.

[Terra Nova]

Originally Posted by SteveWrightNZ

...The example is hypothetical...

In other words...it's a theory--you've never actually done this.

[Cadence]

I think people should parallel mix lawn mower or motorcycle batteries with 8Ds. The chemistry is the same but see how the miniscule plate size works for them. Probably work fine till the plates on the smaller one are eaten up. Hopefully only reducing it's life not shorting out the depleted plates thus shorting out the 8D. I know, a bit over stated, give it some thought.

[skipmac]

Originally Posted by Cadence

I think people should parallel mix lawn mower or motorcycle batteries with 8Ds. The chemistry is the same but see how the miniscule plate size works for them. Probably work fine till the plates on the smaller one are eaten up. Hopefully only reducing it's life not shorting out the depleted plates thus shorting out the 8D. I know, a bit over stated, give it some thought.

The problem with this example is that the max charge acceptance rate of the motorcycle battery would be grossly exceeded so of course it would be destroyed. Use batteries with similar charge acceptance specs and you won't have that problem.

[Cadence]

Originally Posted by skipmac

The problem with this example is that the max charge acceptance rate of the motorcycle battery would be grossly exceeded so of course it would be destroyed. Use batteries with similar charge acceptance specs and you won't have that problem.

If you say so?.

[tomtriad]

I didn't read all the posts, but i would contact Lifeline tech support. They are very knowledgeable and willing to share it with no bs.