Do I need to replace my batteries?

[rgleason]

IMHO don't believe that 1/10 stuff. Years ago we purchased a 14w/12v = 1.1 amp and asked specifically about getting a controller and the salesman said we did not need it. Our batteries were 24's = 140 ah.



That summer we fried our batteries (they were 3 year old batteries but still good, and we kept them topped up as best we could with the alt and hoped the PV would take care of the rest.



The first day back on the boat I could not believe that our Link was showing 20v. I then measured at the batteries and got 20v this had been happening for 2 weeks. We immediately got a controller and limped along with the batteries the rest of the summer. I am lucky nothing else was fried that I know of.

Originally Posted by SteveWrightNZ

Consider have a separate very small solar panel to float the start battery. If the small solar panel amps is 1/10th of the start battery AmpereHours, then you won't need a regulator on it, and can wire the panel directly to the start battery (small fuse for it right on the battery.)

The only time the start battery should be anywhere near the house battery is in an emergency (engine wont start - need a jump start). This is pretty unlikely however, but good insurance.

[Unregistered-1]

Originally Posted by rgleason

IMHO don't believe that 1/10 stuff. [....]

That's not a very scientific conclusion however.

I'm not saying you're wrong - I'm saying it's your opinion (and your used batteries) against well-used industry practice.

[john61ct]

If you have a cheap old battery you don't care about, sure great Science Experiment.

Otherwise always put a controller between the batt and panel.

Even a cheap Chinese $20 job is better than none.

[Unregistered-1]

Originally Posted by john61ct

If you have a cheap old battery you don't care about, sure great Science Experiment.

Otherwise always put a controller between the batt and panel.

Even a cheap Chinese $20 job is better than none.

A cheap old battery that you dont care about is no basis for any science experiment of any type. That logic is not just unsound, it's ridiculous.

As well as that, a cheap chinese $20 regulator is emphatically NOT something I would be putting anywhere near my yachts' starting system. That's daft.

[john61ct]

I completely agree.

Just countering the idea that a noobie hooking a panel directly up to a valued battery for days is a good idea.

A $120 Victron is the cheapest I would go personally

[Unregistered-1]

Originally Posted by john61ct

Just countering the idea that a noobie hooking a panel directly up to a valued battery for days is a good idea.

Countering it with what logic?

[john61ct]

Somebody stated an 800AH bank - say a newly bought one that cost $5000 before labor - could be kept topped up safely by 80A worth of panels hooked up directly with no controller.

Ridiculous on the face of it isn't it?

But a 4-yo starter at 50AH worth say $40, go for it see what happens with a 100W panel hooked up raw.

A lot less foolish, cheap lesson learned.

[Australis]

On the info you have supplied I would replace all batteries sooner than later. Three years plus is
good value with your batteries.

[ramblinrod]

Originally Posted by borzoijay

My questions are several......
1. Am I discharging the batteries too much?

Yes, 50% max, but try not to do that. Not less than 80% routinely...I recommend never discharging below 80%.

Alternate opinion.

If the goal is to replace batteries as infrequently as possible, regardless of initial cost, space consumed, and higher total life-cycle cost, upsizing the bank to maintain a higher routine SOC is valid.

However, discharging routinely to 50% SOC will give more lifetime A-hrs discharged / charged, than discharging routinely to only 80% SOC.

Example A) If a 200 A-hr battery is discharged to 50% SOC and recharged to 100% daily, in one year, it will have delivered 100A-hr x 365 = 36.5 K A-hrs. If it lasts 4 years before requiring replacement, it will have delivered 36.5K x 4 = 146 K A-hrs over its lifetime.

Example B) If that same battery is discharged to 80% SOC and recharged to 100% daily, in one year, it will have delivered 40 A-hr x 365 = 14.6K A-hrs. Even if it lasts twice as long under these conditions (unlikely) it will only have delivered 117 K A-hrs over its lifetime.

Everything else equal, assuming replacement batteries are available, and the cost to remove and replace is reasonable, 50% SOC regular discharge will generally deliver a lower life cycle cost than 80% SOC.

What's more, to discharge to only 80% SOC, requires a larger bank, higher initial battery and wiring cost, and more space, which could come at incredible cost (need for a larger boat to accommodate all of the batteries).

[john61ct]

I agree limiting to 20% discharge for a small boat where the owner does the replacement, means carrying around too much "dead lead" weight and paying twice up as much front,

And downright silly, if it turns out they're not getting longevity-coddled in all the other ways.

But if weight is **not** an issue and reliability is paramount (e.g. circumnavigating), AND the bank is of super high quality and cared for in order to get 10+ years' lifespan, then shallow cycling is a good strategy.

Moreover, if high priced labor is paid for the bank replacement process, it probably even makes sense from a strictly economic POV.

[ramblinrod]

Originally Posted by john61ct

I agree limiting to 20% discharge for a small boat where the owner does the replacement, means carrying around too much "dead lead" weight and paying twice up as much front,

And downright silly, if it turns out they're not getting longevity-coddled in all the other ways.

But if weight is **not** an issue and reliability is paramount (e.g. circumnavigating), AND the bank is of super high quality and cared for in order to get 10+ years' lifespan, then shallow cycling is a good strategy.

Moreover, if high priced labor is paid for the bank replacement process, it probably even makes sense from a strictly economic POV.

Again, everything else being equal, selecting / installing a bank for intended short cycling, will generally have a greater total cost. Size of boat or battery quality has little to no bearing.

[ramblinrod]

Originally Posted by john61ct

But if weight is **not** an issue and reliability is paramount (e.g. circumnavigating), AND the bank is of super high quality and cared for in order to get 10+ years' lifespan, then shallow cycling is a good strategy.

Reliability and longevity are really two different things.

Any which way one looks at it, shallow cycling is rarely a good strategy.

Everything else equal, a larger than necessary bank increases costs:

1. Initial battery purchase / installation

2. Initial wiring

3. Higher charging system capacity.

4. Longer charging system running time.

5. Maintenance.

6. On-board real estate consumed

7. Premature death replacement

8. Depreciation when boat is sold.

9. Lost speed / additional fuel consumption (due to weight).

The goal should always be to balance the DC electrical system storage and charging system capacity to intended loads. Needlessly increasing either is normally a waste of money.

[tomtriad]

I think your first stop should be consulting with the battery manufacturer.

I had problems with a "dead" battery bank which had discharged due to a faulty fuse in the voltage regulator controlling solar panels. I learned a LOT from talking to the manufacturer's technical support department, about how to charge and test their batteries, old and new. I use Lifeline AGM's, and wound up replacing them as I could not get them charged up sufficiently after this deadly incident. They were 7 years old and still going strong up till then.

You need to determine what voltages to charge your batteries to (for both "acceptance" and "equalization") and make sure you have the right equipment set to the correct limits. Also, when you are measuring the "resting" voltage on your batteries they should have been disconnected from everything (chargers and appliances) for several hours before measuring.

The support page on the Varta website states that this battery type is fully charged at 12.7 volts (resting) and doesn't need charging until 12.1 volts. -11.9 volts is critical. https://www.varta-automotive.com/en-...-a-car-battery. I suggest you read all of the information on the site, then call them if you have questions. I would do both.

If you have a battery isolater switch with the house bank on 1 and the starting battery on 2, you should be able to switch to "both" to get enough voltage to start your motor if necessary without resorting to the generator.

You definitely want some sort of controller(s) or regulator which monitors and outputs the correct voltage for each of your charging devices - the motor, the generator, and the shoreside charger.