Charging Issues - solar bulk charge =12.65v, alternator=14v

[john61ct]

Originally Posted by sailinglegend

I don't dispute any of the above - but go to one of the 'best gear stops charging directly based off endAmps' - like Outback and see what they say in their setup for end amps.

What would the maker of the charge source know about the needs of my specific bank?

I would not purchase a deep cycling battery where the precise spec is not clearly published by the manufacturer.

But .005C is what I would use for a default, at least when the bank is new.

Very sensitive chemistries like GEL or Fireflies may be as early as .02C.

But this is a detail, not relevant to the larger question under discussion.

> you are overcharging your batteries

I am not.

That passage is talking about constant output at a single voltage like ancient garage style chargers.

I would never use such a source directly on anything but a cheap sacrificial starter batt, which is what they are designed for.

I agree that those with VRLA chemistries need to adjust more carefully, especially GEL.

But there is no disputing that chronic PSOC is **very** common, and **very** bad for longevity, and

the only accurate measure of 100% Full is endAmps.

> You are entitled to your opinion that you are doing no damage to your batteries by staying at Absorption when the batteries are full

That is not what I am saying.

If you don't base stopping directly off endAmps, adjusting AHT is necessarily a balancing act, impossible to be precise.

I **do** say going long by a few hours occasionally is better for longevity than constant PSOC abuse.

I am not claiming that you explicitly advocate for the latter, but leaving adjustable charge sources at their default - is that really what you are advocating as a rule?

will have that result 90+% of the time.

[john61ct]

A recent MS post

http://www.cruisersforum.com/forums/....php?p=2706281

on just how harmful PSOC is IRL. Yes extreme examples, but unfortunately not uncommon out on the water, even with owners of the most sophisticated gear when left at its OOTB defaults.

[sailinglegend]

Originally Posted by john61ct

....> you are overcharging your batteries

I am not.

That passage is talking about constant output at a single voltage like ancient garage style chargers.

Since you are so set in your ways this will be my last response as you have produced no evidence that supports your position.

The passage above is under the heading multi stage 'smart' regulators....

Several paras later Calder says:

The float charge.
If the absorption phase were to be continued beyond the fully charged state, the battery would be damaged from overcharging. To avoid this, at the completion of the absorption phase, a multistep regulator trips to a lower constant-voltage float setting (generally between 13.2 and 13.6 volts). This protects the battery from overcharging during periods of extended engine-running time.

I rest my case.

[john61ct]

Again, if only occasionally, and only for a few hours, much less "damage" (reduction of lifetime cycles) than chronic PSOC.

With FLA, none at all, even frequently and longer, long as water level maintained.

But occasional checking and adjustment will prevent that anyway.

For those who think this is a major concern for their particular bank,

just get charge sources controlled by reaching endAmps, and the issue goes away completely.

[sailorboy1]

It’s a battery, on a boat. It’s senseless to over worry about it as you will spend more money and time on the damn thing than it will in either to replace when the time comes.

[Joe Okros]

LOL, reading through these replies is hilarious,- it's no wonder the marine industry makes so much money. There are so many opinionated "suckers" in the sailing fraternity.
Its quite simple mate,-Your alternator can probably output close to 100Amps depending on which one you have. AGM batteries can absorb BIG AMPS, that is their strength. So depending on how BIG and how discharged your batteries are it may take a BULK charge of 40 or 50 AMPS to get them to 14.4V.

Your alternator is capable of doing this,--your solar panel not.

Your Solar panel can only supply about 9A and will continue to do so for a LONNNNNNNNGGGGGG time to reach 14.4 V. To approximate your alternator output you will need to install 1000W of solar panels.

Everything else is just gibberish.

[CatNewBee]

Originally Posted by Joe Okros

LOL, reading through these replies is hilarious,- it's no wonder the marine industry makes so much money. There are so many opinionated "suckers" in the sailing fraternity.
Its quite simple mate,-Your alternator can probably output close to 100Amps depending on which one you have. AGM batteries can absorb BIG AMPS, that is their strength. So depending on how BIG and how discharged your batteries are it may take a BULK charge of 40 or 50 AMPS to get them to 14.4V.

Your alternator is capable of doing this,--your solar panel not.

Your Solar panel can only supply about 9A and will continue to do so for a LONNNNNNNNGGGGGG time to reach 14.4 V. To approximate your alternator output you will need to install 1000W of solar panels.

Everything else is just gibberish.

... well it depends, my solar yelds 100A charge current and 600Ah per day (1650Wp). My alternator contributes with 20 to 40A, but usualy it is not running. I prefer sailing to motoring.

[john61ct]

Originally Posted by Joe Okros

LOL, reading through these replies is hilarious,- it's no wonder the marine industry makes so much money. There are so many opinionated "suckers" in the sailing fraternity.
Its quite simple mate,-Your alternator can probably output close to 100Amps depending on which one you have. AGM batteries can absorb BIG AMPS, that is their strength. So depending on how BIG and how discharged your batteries are it may take a BULK charge of 40 or 50 AMPS to get them to 14.4V.

Your alternator is capable of doing this,--your solar panel not.

Your Solar panel can only supply about 9A and will continue to do so for a LONNNNNNNNGGGGGG time to reach 14.4 V. To approximate your alternator output you will need to install 1000W of solar panels.

Everything else is just gibberish.

Funny mate.

AGM still takes 5-7 hours to get to 100% Full from 50%, no matter if your Alt is putting out 300A or just 80A, depending on how big a bank of course.

That high CAR does not last long, and getting to endAmps is critical for longevity.

Now if you say you don't care about longevity, fine, your rig your choice, but that's what the thread is about.

And the drifted topic main point is LFP can get back to Full in an hour or less, no long trailing current issue.

https://marinehowto.com/how-fast-can...ry-be-charged/

[thomm225]

Originally Posted by Joe Okros

LOL, reading through these replies is hilarious,- it's no wonder the marine industry makes so much money. There are so many opinionated "suckers" in the sailing fraternity.
Its quite simple mate,-Your alternator can probably output close to 100Amps depending on which one you have. AGM batteries can absorb BIG AMPS, that is their strength. So depending on how BIG and how discharged your batteries are it may take a BULK charge of 40 or 50 AMPS to get them to 14.4V.

Your alternator is capable of doing this,--your solar panel not.

Your Solar panel can only supply about 9A and will continue to do so for a LONNNNNNNNGGGGGG time to reach 14.4 V. To approximate your alternator output you will need to install 1000W of solar panels.

Everything else is just gibberish.

Some of us don't even have alternators and our panels are enough.

John and some others just get too focused on the one thing. Once he/they get a boat and/or actually start sailing the one they have they will chill out a bit

My system with both PWM and MPPT seems to be doing quite well. I'm at 12.7 volts after sailing all day

[Joe Okros]

I'm not going to get drawn into arguments about battery chemistry, setpoints, SOC, Bulk, Absortion, Peukert, longevity etc etc.

The FACT is the OP was puzzled about the voltage displayed on Solar charge vs Alternator charging. Its quite simple, the SMALL solar panel does not provide enough amperage to raise the voltage vs the LARGE Alternator providing sufficient.

I'm an engineer and I'm happy to talk about these things all day long but let's start with Ohm's Law and keep it simple.

[Jon Hacking]

Originally Posted by sgtPluck

I have a bit of a mystery with my charging system for my AGM batteries. … Is there some normal circumstance that would explain why my MPPT controller would register such a low voltage as compared to the alternator? Or do I need to start troubleshooting? Thx!

Sarge, these are great questions. The short answer is things look mostly OK.

As batteries charge up, their voltage rises, & the more current they're fed, the higher their voltage. Good 3-stage chargers will start by putting as much current into the battery as it can (Bulk) until it reaches the "Acceptance" voltage (which is different for each battery type, & is also temperature dependent, so your chargers need to monitor battery temperature). Then it will hold that voltage constant until the battery is essentially full, after which it will switch down to a "Float" voltage, where the battery can sit all day without damage. As the battery becomes more charged, it requires less & less current to maintain that Acceptance voltage. A *good* charger (solar, alternator, & AC) will watch the current *into the battery* & will only switch to Float when the current into the battery required to maintain the Acceptance voltage drops to 1-2% of the Amp-hour capacity of the battery.

Unfortunately, most chargers don't monitor the current into the battery (which requires an extra connection to the shunt on the battery). Instead, they monitor the current they're producing, & it doesn't know how much of that current is going into the battery & how much is servicing house loads (fridge, lights, etc), which can lead to over/under charging. Very few chargers allow shunt connections these days (only 1 alternator regulator that I've seen, & it's not a Balmar).

Your alternator is producing much more current (typically ~50+A) than your solar array (9.4A) which is why the voltage is higher with your alternator. But I do see some issues here.

12.65v is a bit low for an AGM battery. Presumably the screen-shot is from the morning. The less you discharge your batteries, the more cycles they'll give you, which is why larger battery banks last longer than smaller ones. Try to use only the top 20-30% of your AGM's capacity, & don't take them below 50% or you'll be limiting their life.

Also, if your battery is at 14.0v & your alternator is producing 14.4v, you're losing 0.4v in your wiring & connections. This isn't a big issue, but you might consider cleaning up your alternator connections & maybe coating them in some dielectric grease to keep them from oxidizing. You might also consider using bigger wire for the output of your alternator.