A way To Save Charging Time

[a64pilot]

This is an article about AGM, however I think it's basically applicable for all LA banks, theoretically an AGM bank would benefit the most from a big charger, however read how much time to full charge it saved
http://www.pbase.com/mainecruising/e...on_agm_battery

[Fuss]

Originally Posted by Kenomac

Come on over, I'll show you.

2 things most likely are happening here...just roughly...

1 - if the charging time is reduced by 60% then the original charging concept was not adequate or optimised for this particular installation.

2 - im not saying your one does this but generally, battery monitors adapt their behaviour to the way you are charging, so for example, if the monitor starts seeing a low charging current of say 5 amps, it thinks the batteries are full and adjusts itself back to 100% even though the reality is really 80%, that's why you think you are able to bring your bank up to near 100 so fast. It's more than likely reading 100 when it's 80%. You should read the handbook on your monitor.

[mitiempo]

Another way of telling the bank is full is if it is accepting .5% of capacity. In other words a 900 AH bank isn't full until it is accepting 4.5 amps. Easily measured with a clamp meter.

Battery monitors typically call the bank full when it is accepting 2% of C, or 18 amps with a 900 AH bank. Not quite full but close.

[Kenomac]

Then why is the monitor showing that all the amp hours are back in place?

[Kenomac]

Originally Posted by a64pilot

This is an article about AGM, however I think it's basically applicable for all LA banks, theoretically an AGM bank would benefit the most from a big charger, however read how much time to full charge it saved
How Fast Can an AGM Battery Be Charged..? Photo Gallery by Compass Marine How To at pbase.com

I read the article. My situation/experiment was quite different as I outlined. My batteries were at 73% when I began charging and had reached 98.5% after 1.5 hours. The final 7-10 Ah required an additional .5 - .75 hour to bring the charge back to float status 100%. So yes, the last 2% took almost an hour, nearly as long as bringing the batteries back up from 73% to 98%.

But the entire process was much shorter with the additional charging capability.

[conachair]

Originally Posted by Kenomac

Then why is the monitor showing that all the amp hours are back in place?

Sounds suspect, what's the SG reading during charging?

Is it even physically possible to charge LA batteries that fast?

[Fuss]

Originally Posted by Kenomac

Then why is the monitor showing that all the amp hours are back in place?

It could be as follows.....

Lets say the monitor reads 100% when in reality its only 90%, then when all the amps are back its the amps from the 90% that are back and there is still 10% more charge that is not known about as the monitor is saying 100% which is what you want to see.

So to check if its really 100%....
Charge until all the amps are back and it should then say 100%. Now try to ensure no devices are pulling amps then see how many amps the batteries accept over a few minutes. If it takes more than 10 amps then they probably are not fully charged. If it accepts under 10, then you are right they are fully charged, but I would imagine this is unlikely given the short time to reach 100%.

So the question is, how many amps will the batteries accept when they are fully charged as indicated on the Monitor.?

[conachair]

Originally Posted by Fuss

So to check if its really 100%....

Get out the hydrometer, probably the most accurate way to determine SOC.

[sailorboy1]

Originally Posted by Kenomac

. It took only 1.5 hours to bring them back up to 97%, then I didn't feel like listing to the genset for another 45 minutes or so just to get the final 7ah back in, so I reconnected to shore power.

It takes hours to do that last few percent and it has nothing to do with how large your charge source is. If you think otherwise you are wrong.

[barnakiel]

Can someone PLS go back to that point where it is stated 'under 10A it is fully charged'?

I do not get this part. Is your bank 10000Ah deep?

I have a100Ah bat, when fully charged it accepts 0.1A.

So I do not get where the exponential factor steps in. I am likely reading something wrong.

Thanks in advance,
b.

[mitiempo]

Originally Posted by conachair

Is it even physically possible to charge LA batteries that fast?

No it is not possible.

[Kenomac]

Originally Posted by mitiempo

No it is not possible.

Tomorrow I'll run the batteries down again, then charge them up and time it again. I have an appointment next week for a Solbian consultation and possible install.

How many solar watts should I purchase? 224w, 375w or 450w?

[a64pilot]

Originally Posted by Kenomac

How many solar watts should I purchase? 224w, 375w or 450w?

As much as you can afford, fit and tolerate. I have 1KW, however many people would say, My God, how could he ruin the lines of the boat like that. That is what I mean by tolerate.
Unless your needs are very meager, and on a boat like yours I doubt that, the smaller installs will only really be useful for keeping the batteries up while your away

[a64pilot]

Originally Posted by Kenomac

Tomorrow I'll run the batteries down again, then charge them up and time it again.

Logically, you will get the same result.
I would determine by specific gravity or by acceptance rate if my bank was fully charged or not. We are betting it is not fully charged when your monitor says it is, that is apparently very common. I have never had a normal battery monitor so I can't comment from experience

[sailorboy1]

Originally Posted by a64pilot

As much as you can afford, fit and tolerate. I have 1KW, however many people would say, My God, how could he ruin the lines of the boat like that. That is what I mean by tolerate.
Unless your needs are very meager, and on a boat like yours I doubt that, the smaller installs will only really be useful for keeping the batteries up while you away

Not really true. Only on forums do boat need to become solar aircraft carriers. 8 months of cruising and still using the same 290w I had before starting and the lowest I'm seen battery charge is 78% once, normally the lowest I see is 85%.