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Old 24-08-2016, 17:15   #1
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So you think yours batteries are charged?

Thought I knew a lot about batteries and charging systems (grew up and still in automotive industry).
Recently outfitted boat for long range extended time on the hook
900 a/hr bat bank, solar, inverter/125a charger etc.
No sweat everything working great but bat voltage down to 12.4 in the am after 120 a/hr draw overnight. (Victron meter)
Read 75% SOC right? Should be 86.7 SOC
120/900=86.7%
Problem is over time the bank goes down and not starting w/100% charge.
Engine alternators set @ 13.7v
Solar 780 watts but not enough sun on cloudy days to over come usage and have a net amperage to bring the bank up to 14.8v absorption long enough.

So let's start the gen.
Charger reads the 13.7 volts and thinks the bank is fully charged so goes into float.

Long days run? Victron reads fill charge (I've tried to reset this, save for another topic),
After running for 6-8 hours bank should be charged right? NOT, only reaches 13.7 volts (alternator setting) not enough voltage to bring the bank to 100%. And if you plug into shore power at the Marina after a long run you figure I'm OK I've got the charger on, WRONG charger reads 13.7 so it goes to float!

Solar you say, if there is not enough sunlight and wattage output it will never reach absorption stage long enough to reach full charge even though you have replaced the a/hrs used.

Bottom line
At home dock no power usage (Everything shut down not living on board right now), 1 day solar back to 1% amperage charge of bank size
I.E. 9 amps @14.8v

Used 120 a/hrs last night (test run with inverter running and fans etc, to run down to 88% charge and VIOLA 12.6v in AM

So I emailed the charger co (magnum ms2800) and they told me yes! To fool the charger so it goes into absorption, turn every thing off for 2 min and wait for voltage to go below 12.7 (which may require loading batt bank, and Viola goes into absorption mode.

Moral of the story is when your net amps into the bank are 1%-2% of total a/hr capacity at the rated absorption voltage your 100%
Unless you are sulfated (check specific gravity with a GOOD tester not one of those el chepos)

Hope this helps someone, took me months to figure it out, I'm sure most of the more experienced cruisers out there already know this.
Thanks for listening
Panacea
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Old 25-08-2016, 06:24   #2
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Re: So you think yours batteries are charged?

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Old 25-08-2016, 06:48   #3
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Re: So you think yours batteries are charged?

Good post. I've run into a similar situation with my new bank and new solar. My victron would read full but my batteries were drawing down to below 12 after a night's heavy draw. Full details are over at that other thread (Battery @ 11.75v under sustained 8 amp load), but my problem appears to be a poor solar controller.

In the end I was (am) experiencing the same slow draw down problem.
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Old 25-08-2016, 06:51   #4
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Re: So you think yours batteries are charged?

Don't forget peukerts law. Google it. Taking 25% out of a house bank doesn't leave it at 75% soc. As it gets drawn down then reserve is less etc .

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Old 25-08-2016, 07:03   #5
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Re: So you think yours batteries are charged?

You should be charging your batteries at 14.4 - 14.8 volts, not 13.7 v. You will never fully charge your batteries if your alternator is set to 13.7v.
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Old 25-08-2016, 08:29   #6
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Re: So you think yours batteries are charged?

Quote:
Originally Posted by DeepFrz View Post
You should be charging your batteries at 14.4 - 14.8 volts, not 13.7 v. You will never fully charge your batteries if your alternator is set to 13.7v.
That's just the start of things. Is your alt externally regulated, and at what setting? Are your panels going through an MPPT to the banks, and at what setting? What's the specific gravity of your electrolytes in your bank? What is the resting voltage?

Have you ever equalized your batteries?

Plenty of questions before a definite answer can be given.
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Old 25-08-2016, 08:34   #7
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Re: So you think yours batteries are charged?

Thanks Panacea...
There are two things that new cruisers find out at about the 6 month to a year mark of living aboard full time.
1. They had no real idea on the amount of time routine maintenance and running the boats systems actually takes.
and
2. They realize just how little they really knew about their batteries and charge system and usually end up upgrading one or both

So it's always useful to have these posts because you are not the only one my friend to have danced this dance, nor will you be the last. When I talk to people at boat shows getting ready to cast off on their "around the world cruise" I always make it a point to ask them about their battery and charging set-up. And a good 75% + can't tell me the Amp hour size and type of their batter bank. This isn't to ding them...they just haven't realized just how important that subject it...at least not yet...
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Old 25-08-2016, 08:50   #8
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Re: So you think yours batteries are charged?

So I emailed the charger co (magnum ms2800) and they told me yes! To fool the charger so it goes into absorption, turn every thing off for 2 min and wait for voltage to go below 12.7 (which may require loading batt bank, and Viola goes into absorption mode.

When you say turn everything off are you speaking of all the charging systems? if you turn off appliances voltage would go up.
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Old 25-08-2016, 09:49   #9
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Re: So you think yours batteries are charged?

Quote:
Originally Posted by Mark Killam View Post
So I emailed the charger co (magnum ms2800) and they told me yes! To fool the charger so it goes into absorption, turn every thing off for 2 min and wait for voltage to go below 12.7 (which may require loading batt bank, and Viola goes into absorption mode.

When you say turn everything off are you speaking of all the charging systems? if you turn off appliances voltage would go up.
Meant to say turn off solar and charger part of inverter/chsrger, leave loads on so batt voltage drops below 12.7 . After 2 min turn charger back on and it should go into bulk setting first then absorption.
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Old 25-08-2016, 09:53   #10
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Re: So you think yours batteries are charged?

Quote:
Originally Posted by Dulcesuenos View Post
Don't forget peukerts law. Google it. Taking 25% out of a house bank doesn't leave it at 75% soc. As it gets drawn down then reserve is less etc .

Sent from my STUDIO 5.5 using Cruisers Sailing Forum mobile app
Victron is set for that at 85% efficiency and 1.5 on peukerts law
Tail amperage also set to 2% of 900 a/hr bank, for some reason still reads 100% will review settings, but that does not have anything to do with the charger not going into bulk or absorption.
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Old 25-08-2016, 10:00   #11
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Re: So you think yours batteries are charged?

Quote:
Originally Posted by DeepFrz View Post
You should be charging your batteries at 14.4 - 14.8 volts, not 13.7 v. You will never fully charge your batteries if your alternator is set to 13.7v.
Realize that, just don't want to spend the $ to replace regulators and the controller to make the alts play nice together.
Since most of my time is spent on the hook, I'm relying on solar and generator to charge batteries.
When running hopefully the alternators will give be a bulk charge and the solar will be able to take over and give me enough absorption time.

Best way is to check specific gravity 1275+ but quick way assuming no sulfation is to monitor amp charge at absorption and make sure it goes to 1-2% of amp/hr capacity.
Thanks
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Old 25-08-2016, 10:21   #12
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Re: So you think yours batteries are charged?

Quote:
Originally Posted by S/V Alchemy View Post
That's just the start of things. Is your alt externally regulated, and at what setting? Are your panels going through an MPPT to the banks, and at what setting? What's the specific gravity of your electrolytes in your bank? What is the resting voltage?

Have you ever equalized your batteries?

Plenty of questions before a definite answer can be given.
No internal regs.
Mppt morning star controller
Set to 14.5 I believe max setting with dip switches. Need to get to 14.8, but a good soak every month or so should be OK
These are Trojan T105RE not T105 which are suppose to be happy at that 80% SOC upgraded to the T105RE after talking to Trojan before purchase.
Specific gravity @ 1275+ when full charged all cells equal
Rest voltage @ full charge= 12.7
Batteries 1 yr old never equalized according to Trojan not needed at these specs
But I plan on doing it anyway when I'm back on shore power
Believe I have my problem solved by "fooling the charger into going into bulk mode.
PS: the newer remote controls have this option in the software mine does not,
So if you plan on buying a magnum ms with remote get the newer remote.
Thanks.
PS: all this goes away if I start gen before sun comes up when bank is below 12.7, then the gen goes into bulk stage, just don't like gen running that early. Nothing worse than sitting on sundeck with a cup of joe watching sun come up listening to wild life and then Bam someone's gen starts up I'd rather listen to some one else's than p**s of the neighbors with mine.
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Old 25-08-2016, 10:58   #13
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Re: So you think yours batteries are charged?

Thanks for interesting post, Panacea!

Very informative, although I have to admit I can just barely follow the lingo. However growing up on a farm having to deal with all kinds of machinery I have some practical knowledge and presently reading up on the theoretical stuff, as we plan to set of on our coconut milk run (hopefully all the way) next summer.

This may be off post, apologies should that be the case, however I wanted to ask you this as you say you have automotive background.

I have several friends who are car mechanics (but not sailors!) and I've had a few discussions with them regarding batteries and charging systems. Chiefly they claim that lead batteries are old tech and that most cars use some kind of Li battery these days, supplied by a powerful alternator. My objection that they may be too dangerous on a boat where, rather forcefully, put down. They claimed Lithium tech with modern BMS are at least as safe if not more so...Sulphuric Acid is no walk in the park either they claim.

So my question is; Have you given any thought to having your battery bank made up by LiFePo4 batteries? And then beefing up your alternators (we plan to buy a cat) to at least 120 A?

Could write quite a bit more her, but I've already written too much, interested in your (and others...) take on this though.

Brgds

Oddvar
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Old 25-08-2016, 11:29   #14
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Re: So you think yours batteries are charged?

The only cars with lithium batteries are electric cars. Starting batteries are still lead acid based chemistry. However many house banks are LiFePo batteries and while state of the art, are being successfully used by many on this forum.
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Old 25-08-2016, 11:35   #15
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Re: So you think yours batteries are charged?

Quote:
Originally Posted by ObiWanSand View Post
Thanks for interesting post, Panacea!

Very informative, although I have to admit I can just barely follow the lingo. However growing up on a farm having to deal with all kinds of machinery I have some practical knowledge and presently reading up on the theoretical stuff, as we plan to set of on our coconut milk run (hopefully all the way) next summer.

This may be off post, apologies should that be the case, however I wanted to ask you this as you say you have automotive background.

I have several friends who are car mechanics (but not sailors!) and I've had a few discussions with them regarding batteries and charging systems. Chiefly they claim that lead batteries are old tech and that most cars use some kind of Li battery these days, supplied by a powerful alternator. My objection that they may be too dangerous on a boat where, rather forcefully, put down. They claimed Lithium tech with modern BMS are at least as safe if not more so...Sulphuric Acid is no walk in the park either they claim.

So my question is; Have you given any thought to having your battery bank made up by LiFePo4 batteries? And then beefing up your alternators (we plan to buy a cat) to at least 120 A?

Could write quite a bit more her, but I've already written too much, interested in your (and others...) take on this though.

Brgds

Oddvar
Have never seen LI batteries in a conventional car, maybe hybrids or electric but not standard cars.

They are expensive and in MHO
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