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

[john61ct]

If the charge profile was set right, there is little to no current transfer once the voltage drops to Float.

IOW charging is done.

The purpose of Float is to counteract self-discharge in storage.

And for the source to be ready to feed loads as they come online, so the bank does not start a new cycle until actually needed.

If your bank is still regularly accepting over .01C at Float voltage then your Hold Absorb Time should be increased.

[john61ct]

Originally Posted by thomm225

my "bank" is two $88.00 deep cycle batteries in parallel from auto world, zone, place

No such thing. They may fraudulently have "deep cycle" printed on them, but they are not true deep cycle batts.

[Maine Sail]

solar bulk charge =12.65v, alternator=14v

This is simply the difference between the solar array's low current and the alternators high current.

With a low charge current eg; many small solar systems on boats, the bulk charge duration takes a considerably longer time to attain the absorption target voltage. On many boats bulk can literally take all day and still not get to the absorption voltage.

Even your alternator was not yet at absorption voltage, only 14.0V, so it too was still in bulk with a charge current of likely 5-6 times your PV array..

As an example a healthy AGM bank, when charged from 50% SOC, using a target absorption voltage of 14.4V & with a charge rate of .2C or 20% of Ah capacity takes about 1:15 minutes to attain the absorption target voltage of 14.4V.

The same exact battery, when charged at .4C or 40% of Ah capacity, only remains in bulk for about 20 minutes...

The amount of charge current you deliver to the battery is what determines how long it will take to get to absorption voltage.

50% DOD to Absorption @ .4C = 20 minutes

50% DOD to Absorption @ .2C = 1:15 minutes

If we figure or guess that your boat has a 400Ah bank and a charge rate of 7.5A you are charging your bank at approx 0.019C so....

50% DOD to Absorption @ .02C = a darn looooong time


This article should help shed some light on the relation ship between charge current, bulk duration & total time to charge duration.


How Fast Can an AGM Battery be Charged? (LINK)




.

[sailinglegend]

Originally Posted by john61ct

If the charge profile was set right, there is little to no current transfer once the voltage drops to Float.....

Nobody I have ever met in 10 years living aboard in the Med sets their chargers as you do.

As I have already suggested this is dangerous because if you have programmed your absorption time to last from 50% to 100% SOC then when your charger comes on when the batteries are at 75% SOC the batteries will reach 100% before your extended absorption time is reached. If it stays at absorption voltage for 2-3 hours every day when the batteries are 100% this will cause serious gassing and dry out the batteries - especially bad for sealed batteries.

Please stop posting such irresponsible ideas and making them out to be the only way to programme your chargers.

[thomm225]

Originally Posted by john61ct

No such thing. They may fraudulently have "deep cycle" printed on them, but they are not true deep cycle batts.

Whatever, it's what I'm using at the moment.

If I buy one of those small cooler size compressor refridgerators, I may have to make a change.

One thing that is certain though is that these batteries aren't like starter batteries. These two take a lot longer to charge than when I had a starter battery mixed with a deep cycle.

I'm guessing the starter battery charged up really fast and showed that higher voltage whereas the deep cycle took longer and sometimes may not have charged up totally which killed it after 4-5 years

[missourisailor]

Originally Posted by hellosailor

.... A BlueSkies unit simply tries to lead the battery voltage, by about 0.4V (iirc) and maximize the amperage it can supply. You won't see the 13.8V that a dumb three stage charger (like Balmar) wants to put out, because BS knows that the battery electrolyte will bubble less, the internal resistance will be lower, and the battery will charge about 15% faster this way.

Very, very, interesting!

Can you provide a source for this?

I've always liked and used Blue Sky's products, but never knew this.

[CatNewBee]

Originally Posted by missourisailor

Very, very, interesting!

Can you provide a source for this?

I've always liked and used Blue Sky's products, but never knew this.

The battery SOC and its resistance determines the voltage at the battery plugs. I would be happy with that reading, it shows you have a good wiring between controller and battery, little voltage drop. Your battery is simply not yet charged enough to show a higher voltage.

If your wiring would be bad, you still will measure a low voltage at the battery, but the controller will show a much higher voltage value. The difference is the voltage drop along the connection.

[conachair]

Originally Posted by sailinglegend

Nobody I have ever met in 10 years living aboard in the Med sets their chargers as you do.

As I have already suggested this is dangerous because if you have programmed your absorption time to last from 50% to 100% SOC then when your charger comes on when the batteries are at 75% SOC the batteries will reach 100% before your extended absorption time is reached. If it stays at absorption voltage for 2-3 hours every day when the batteries are 100% this will cause serious gassing and dry out the batteries - especially bad for sealed batteries.

Please stop posting such irresponsible ideas and making them out to be the only way to programme your chargers.

Anyone reading this thread wondering about changing default solar regulator settings (which is what is being discussed) would do well to dig deeper into this thread and the depth of discharge myth thread et al before believing any of that. I and many others set float voltage to the same as absorption voltage at manufacturers settings or some higher. Even then it's hit and miss getting to full charge from solar unless you have acres of panels and a small bank. From data and links in these threads not regularly getting fully charged is a major league serial bigger killer way beyond an hour or 3 sitting at absorption at full charge.

[sailinglegend]

Originally Posted by conachair

......I and many others set float voltage to the same as absorption voltage at manufacturers settings or some higher. Even then it's hit and miss getting to full charge from solar unless you have acres of panels and a small bank.......

Setting Float to Absorption voltage is OK for solar chargers but not for other chargers, which is what John61ct was suggesting.

Any changes to any default settings need to be done by people who really know and understand what they are doing - and I'm afraid that doesn't include many who just read these posts. Yes they are trying desperately to understand their DC systems but they have to be very careful what they do after reading some posts on here. Cruisersforum.com is one of the better forums.

Maybe it's better to be in the camp that changes their batteries every 2-3 years and doesn't care too much about what their inaccurate analogue voltmeter is telling them. My Lifeline AGMs have lasted 14 years of full time live aboard in the Med with only 140 watt of solar and a wind generator. Every two weeks on shore power to fully charge and/or equalise the batteries.

[john61ct]

Originally Posted by sailinglegend

Nobody I have ever met in 10 years living aboard in the Med sets their chargers as you do.

Then maybe you can start helping them make their banks last longer.

The above is irrelevant to best practices.

> As I have already suggested this is dangerous

And I have refuted your false claim several times now.

> because if you have programmed your absorption time to last from 50% to 100% SOC

That has nothing to do with my reco.

A low-current charge may not hit Absorb until 80% SoC. A high current one may hit it at 35%.

The AHT setting depends on a given setup and usage pattern, and usually needs to be adjusted as things change.

Whether it is three hours or nine hours does not matter. As long as it is enough to get to 100% Full as per endAmps, and does not too often drop to Float before then.

If your charge source has a stupid-simple egg-timer algorithm that does not auto-adjust for varying conditions, **and** your situation is not at all consistent from day to day, then the challenge is greater

but that does not change the goal, certainly does not mean you give up and just don't even try.

Maybe with a large expensive bank, it would be worth buying better quality gear?

And again, occasionally holding Absorb for a few hours too long does no harm, certainly less than chronic PSOC abuse. Assuming your voltage setpoint is also adjusted properly.

If too-long AHT is happening more than that, then your job is to adjust it lower.

And yes, your point about VRLA batts is valid, they are fussier and more easily damaged. But that is especially true wrt PSOC issues as well, which is why they very rarely last as long as quality FLA.

Definitely a point in favor of not buying sealed unless they're actually necessary.

[sailinglegend]

Your 40-50 posts a day sometimes make hard reading. What do these terms mean:

>That has nothing to do with my reco.
>The AHT setting...

But my main feedback on your posts is that you refuse to accept 'overcharging' a battery when it is full does no harm - and yet overcharging is exactly what you are proposing.

Originally Posted by john61ct

.....And again, occasionally holding Absorb for a few hours too long does no harm, certainly less than chronic PSOC abuse.....

You never offer any references to your ideas and show nothing in your profile to show who you are and whether you are now, or ever have been, even floating on the water?

Search Google and you will find numerous references to how harmful overcharging can be:

https://www.iotaengineering.com/ppli..._Batteries.pdf

'A careful margin exists between maintaining a battery’s full charge and overcharging. Like undercharging, over- charging reduces battery life, but it can also lead to a potentially dangerous situation. Preventing overcharging is another important control an owner has over battery life and safety.'

Hydrogen Off-Gas & Ventilation : Technical Support Desk

Rolls Battery Technical support group:
'1 AH of over charge will in fact produce 0.42L of hydrogen gas PER BATTERY CELL. Also for every volume of hydrogen a ½ volume of oxygen is produced. This must be considered because to remove the hydrogen the oxygen must also be removed.'

Also try many other research papers from the likes of Scania on Battery Gassing.

[conachair]

Originally Posted by sailinglegend

Also try many other research papers from the likes of Scania on Battery Gassing.

It was a report from scania which recommended staying at an absorption voltage of 15.3v because psoc was found to be much more harmful than a few extra hours before switching to float.

[conachair]

Originally Posted by sailinglegend

Setting Float to Absorption voltage is OK for solar chargers but not for other chargers, which is what John61ct was suggesting.

Reread several times , you must be reading a different thread, everything is this one is about solar. From the title onward.

[john61ct]

Reco = recommendation

Absorb Hold Time, spelled out many times.

Nothing I have written applies only to a particular situation, nor charge source category, this is basic 101-level lead bank charging, nothing in question.

Overcharging is nothing but a value judgment like "slut", no objective meaning.

100% Full is objective, via trailing amps.

Failing to get there as frequently as possible murders banks.

Default settings are insufficient 99% of the time.

Best gear stops charging directly based off endAmps - get that if you fear too-long AHT

AHT algorithms are much better than dumb eggtimers on better gear.

Do you dispute any of the above?

IMO Holding Absorb time so long it damages a bank is less of a problem on boats than meteor strikes. PSOC abuse is more common than faded brightwork.

To learn more:

Nigel Calder's "Boatowner's Mechanical and Electrical Manual", I think now up to third edition
or anything else by him

"Sailboat Electrics Simplified" by Don Casey.

Others https://www.bluesea.com/resources/536

"Electrical Systems 101" thread from MaineSail and Stu the mod
http://c34.org/bbs/index.php/topic,5977.0.html

Read MaineSail's postings across sailing forums, google precise keywords, use the site: keyword and quote his handle at that site.

Also everything electrick here, especially about charging AGM (all applies to FLA as well)

http://MarineHowTo.com

When you've realized for yourself what great value he's given us all, make a donation to help cover his site costs, https://marinehowto.com/support/

[sailinglegend]

Originally Posted by john61ct

....Do you dispute any of the above?

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.

OUTBACK
The battery is full or 100 percent SOC at the end of the Absorb stage as indicated by the current reaching a “floor” current known as return amps (a.k.a. end amps). The return amps current is typically around 2-3 percent of the Ah rating of the battery.

Originally Posted by john61ct

....IMO Holding Absorb time so long it damages a bank is less of a problem on boats than meteor strikes. PSOC abuse is more common than faded brightwork.

To learn more:

Nigel Calder's "Boatowner's Mechanical and Electrical Manual"...

This is the only book you refer to, the others are lists of books many of which are so out of date the links are not worth following. I wonder how many you have actually read?

So let me just quote Calder to verify my point that in you are overcharging your batteries.

Nigel Calder's "Boatowner's Mechanical and Electrical Manual"
Now assume a battery is at full charge. A voltage regulator setting of 13.6 volts, producing a charge rate of around 1 amp, will only minimally overcharge a battery. In practice, other losses—both internal and external to the battery—will probably prevent overcharging. But a regulator setting of 14.4 volts, producing a charge rate of 2 amps, will create excessive battery gassing over an extended period, with a consequent loss of electrolyte, potential damage to the battery-plate grids, and the drying out of gel-cells and AGMs.

You are entitled to your opinion that you are doing no damage to your batteries by staying at Absorption when the batteries are full, but I have provided many references that prove my point and you have provided none to prove yours.

So my plea is stop pushing your ideology as best practice. IMHO it is not best practice especially for sealed Leisure batteries which it would seemed many cruisers have. With expensive Gels and AGMs it is even more damaging on your pocket,.