Battery Acceptance & Link 20 / Monitor Operation

[Stu Jackson]

We've had some discussions about battery acceptance (search on "acceptance") in the past.  I thought it might be helpful to describe just what happens, step-by-step when charging after, say, a simple day sail.

The battery acceptance drops off the ability to recharge, to an incredibly low rate of charge as the bank gets fuller and nearest to full. Many times, now based on my Link 2000 experiences, it takes almost overnight to fully recharge a bank.

What goes OUT of your house bank becomes easy to learn from the Energy Budget previously discussed and posted. It's what goes back IN that most people are missing, and relates to the state of charge of your house bank in a very direct manner.

What I've seen, for example is this, from our Link 2000:

--- Return from a day sail, bank is down 15 amp hours, plug into shore power with our 75 amp charger, batteries will only ACCEPT 15 amps (360 AH house bank, they're pretty fully charged if only 15 ah down)

--- Most people will then assume that it will take an hour to replace the 15 amp hours at 15 amps of charge

--- NOT!

--- As the batteries absorb that 15 amp charge, they get fuller

--- The charge RATE goes down to 10 amps after 15 or 20 minutes and the bank is now down to 10 amp hours down

--- Now, it should only take another hour to charge those minus 10 amp hours at 10 amps -- wrong assumption again; we're now up to an hour and twenty minutes to fully charge, right?

--- NOT again, because this keeps recurring

That's why a full charge takes a LOT longer that most people expect.

What goes OUT is easy, what goes BACK takes MUCH, MUCH longer.  That last 15% to 20% takes a long time because of the REALITY of battery acceptance.

Please believe me, folks, because I see this all the time now that I have the Link 200 installed and working.

Please note that this true with alternators as well as shorepower chargers.  Battery acceptance usually "rules" the charging regimen, so even with 100A alternators or shorepower chargers in excess of 40 A, the battery acceptance will determine the amount of charge that can go back into a house bank, usually around a max of 50A for a 400 ah bank.  And it "tapers off" as the bank gets fuller as noted above.

This is why people say the BEST investment for un-knowledgeable and knowledgeable skippers alike is to buy a battery monitor FIRST. Wish I did, because I'd been chronically UNDERCHARGING my house bank, even after all the spouting I do here and on other forums!

Please, believe it!

For a parallel discussion of how much comes OUT, please see the Energy Budget topic, here:  http://c34.org/bbs/index.php/topic,3976.0.html

[Craig Illman]

Stu - I was happy with my Link 20 until I found it read .15 -> .2V lower that what two different portable multi-meters displayed for my batteries. To make matters worse, my XC3012 reads about .3V higher than the house battery bank, so it goes into Float mode too early and the Link doesn't think things are fully charged. I opened an online Tech support question with Xantrex a week ago, but still haven't heard anything from them. Replacing either of them isn't a very attractive option. I was quite surprised by this big variance!

What's a sailor to do?

[Stu Jackson]

...my XC3012 reads about .3V higher than the house battery bank, so it goes into Float mode too early and the Link doesn't think things are fully charged.

Craig - Understand your concern.  Intriguing. While I don't have answers, here are a few considerations.

1.  Link 20 Reading too Low Voltage -- That shouldn't be an issue for bank conditions 'cuz the Link calculates the amp hours based on kilowatts returned to the banks from the charging sources.  So even though it's reading lower voltages, it shouldn't affect its main reason for being.  I assume you've checked all the wiring connections.  As I recall, the wires for the voltage measurements are the really small ones that come with the bundled twisted wires or ones that you've made up yourself, so the wire size should not be a concern, so the only thing left are the connections. Connections should also include the fuse holders. and possible fuse replacement, depending on if you used those readily available el cheapo fuse holders (like I did! ).  I also assume you took voltage readings at the bank(s), at the shunt and at the back of the Link.  What's telling you the Link isn't seeing or calculating "full" banks?

2.  The XC3012 reading too high a voltage could be an issue, but please advise why you think it's gong into float too soon.  I'm not too sure how the voltage enters into your concern for the charger.  For instance, the TrueCharge 20 specifications include this description of switching from absorption to float:

During the absorption charge, the charging voltage is held constant near
the gassing voltage, and the battery gradually reduces the charging current
it demands as it attains full charge. Once the current drops below 4 Adc
for three minutes, the charger either exits to Float for gel and AGM
batteries or charges flooded batteries for one more hour.

If your charger uses the same algorithm (I don't have that manual downloaded, so please check it) then voltage shouldn't enter into the switchover to float, only amperage.

Perhaps you can qualify your concern, or report back when Xantrex replies to you.

I'm not saying you don't have a valid concern, but so far the voltage may, I say may, not enter into it.  Also, what prompted you to identify and then diagnose this problem?

Good luck with Xantrex.

[Craig Illman]

Stu - What started me on this was the Link showing XX amps drawn from Bank 1 and when the XC3012 went into Float mode, the Link wasn't showing even close to having those amps returned. I measured at the batteries and contrasted with what the Link showed and what I was getting out of a 12V adapter adjacent to my panel.

I guess on Friday I need to get the hydrometer and start sampling cells. I probably ought to top off the bank and equalize things a bit too. I seem to be dropping about 30Ah or so in a week. I don't think it's the stereo and the bilge doesn't look like it's cycling. Guess I need to install a bilge cycle counter. I do have a solid-state bilge switch. Maybe it draws more at rest than one would expect.

From the XC3012 manual it sounded like it sampled the banks at 15 second intervals to charge the bank needing charging the most. This implied to me that it was sampling voltage, that may not be the case. I also need to check the battery temperature sensor. The manual said if it didn't have a sensor functioning, it would default to hot battery mode and drop the charge voltage.

So, more stuff to check Friday, or if the weather is too nice, I'll just have to take it out sailing for the first time this season.

Thanks for the ideas.

Craig

[BOB FLEEGE]

Stu and Jon,  Thanks for all the info...Stu the reason I have 2 chargers is that is the configuration I had before my lightening strike in July...I have 2 house banks with 3 optimax each...charged with the Zantrex 40 a total of 330 amp hours when fully charged...3 are located under the setee forward and 4 under the setee aft.... one of those is the Start Opti that is connected to the Zantrex 20 amp charger...Remember my SeaPower system charges my batteries with 5000 kw of 110 power just like I am plugged into the shore power.  Jon thanks for the detailed chart on charging states...I am going to switch my Zantrex..chargers to the Flooded type instead of the AGM  type and see how they work...thanks again Bob Fleege

[Stu Jackson]

Bob, did you mean to post this on this thread???:  http://c34.org/bbs/index.php/topic,4766.15.html

Why not copy & paste it there and then remove it frorm here, kinda confusing as it is.

[Stu Jackson]

The genesis for this original post was from a parallel discussion on co.com, which continued from the concept.

It's here "Simple Battery Management":  http://forums.catalina.sailboatowners.com/showthread.php?t=105340

[mainesail]

Stu - I was happy with my Link 20 until I found it read .15 -> .2V lower that what two different portable multi-meters displayed for my batteries. To make matters worse, my XC3012 reads about .3V higher than the house battery bank, so it goes into Float mode too early and the Link doesn't think things are fully charged. I opened an online Tech support question with Xantrex a week ago, but still haven't heard anything from them. Replacing either of them isn't a very attractive option. I was quite surprised by this big variance!

What's a sailor to do?

Craig,

Meters displaying volts are often off as the wiring can have voltage drop. Even four of my DVM's do not agree with each other reading the same battery.. I would not loose sleep over it.

[Terry Forshier]

I posted awhile back about a problem I had with my Link 10 battery monitor. http://c34.org/bbs/index.php/topic,4716.0.html  I emailed tech at Xantrex and did not hear back so called. I had to wait a bit but finally got through. After several attempts and calls over a week or more it became apparent that the monitor was malfunctioning. I was offered a special price for the link pro unit they are now selling. I ordered it and am waiting for its arrival. I finally heard from Xantrex this week, 3 weeks or more after posting in a reply to my initial question. So my advice is to call them direct on the number in Xantrex's web pages under support.
My signet display shows one voltage, the link 10 showed another and the voltage at the battery with the handheld showed another. I guess this is common??
I am hoping the new monitor will work flawlessly.
(ha ha). Terry

[Stu Jackson]

Posting that three different battery measurement devices showed three different voltages is interesting.  Given Maine Sail's post, what those differences actually were is also very important.  What were the readings?  Did you have your batteries checked from your post in January, or are they new ones?

[Craig Illman]

Stu, MaineSail, etc. - Well, after thinking about it last night, (had to go sailing yesterday and didn't do battery research) I have a theory. Without going into a long story about my electrical upgrade three years ago, I attached my XC3012 leads to the positive and negative connections behind the panel. I know the factory poistive connections are less than robust and I've never been one hundred percent clear on how the negative gets to the panel area. So, I'm suspecting that the negative path is a bit marginal. I think my first little project is to run a new 6ga cable from the battery bank to behind the panel. My main engine ground runs direct on 1ga from the battery bank to the engine. I think I'll check the terminations on the existing postive cabling too. They're not in an easy space to recrimp.

Craig

[Stu Jackson]

1.  I attached my XC3012 leads to the positive and negative connections behind the panel.

2.  I know the factory positive connections are less than robust and I've never been one hundred percent clear on how the negative gets to the panel area.

3.   I think my first little project is to run a new 6ga cable from the battery bank to behind the panel. My main engine ground runs direct on 1ga from the battery bank to the engine. I think I'll check the terminations on the existing positive cabling too. They're not in an easy space to recrimp.

Craig,

1.  Specifically, where?  Why not to the banks directly?  This obviously then depends on the OEM #4 ga. red wires to charge the banks.

2.  The negative goes from the panel negative bus bar to the battery box.  On my boat I installed a NDP in the hot water heater area inside the door.  Before that it went to the battery box connected by the PO to the reserve battery, I switched it to the house bank because it (the wire from the reserve bank to the house bank) got hot when charging because it was a #4 wire.  I enlarged it to #2 between banks and #2 to the NDP.  See my wiring diagram here:  Reply #23 -- http://c34.org/bbs/index.php/topic,4623.15.html

3.   Check the crimps on the +s, yup it's hard, but if your 1-2-B switch is still working, it shouldn't be an issue and I'd do it last.  Run the new 6 ga. to the neg bus on the panel, it's on the top, or closest to you when you open the panel.  It's labeled pretty well.  You'll need to be creative about sizing the spade connectors from the wire to the small screws on the bus.  BE CAREFUL about the jumpers on the bus, because there's a small section on the top for +, too. Connect that new 6 ga. - to the battery negative line before it goes to the engine or install a Power Post or Power Post + or a bus bar to collect all your negatives so there's one wire to the battery box and another to the engine and the rest (including the bilge pump -, panel - and others) can land, even if you have a shunt for a monitor.  FWIW, Jim Moe later said he'd relocated his echo charge wiring from the back of the 1-2-B switch to the batteries themselves, so those who have charger outputs to the 1-2-B switch, thus depending on the OEM #4 reds to carry the charge, should rethink that idea.  Larger chargers may provide more amperage than the #4s can handle, since they're sized for a max of 30 amps FROM the batteries to the switch and distribution panel.  And people have installed higher amperage alternators, so if the alternator output still goes to the 1-2-B switch instead of the house bank, the #4s get too small.  That's another reason to get everything off the darn switch except battery OUTPUT TO the DP and starter from the C post.

[Craig Illman]

Stu - First off, I don't have a 1-2-B anymore. The "start battery" has a 150A circuit breaker and goes directly to the engine on 1ga. The alternator comes directly to the "house bank" on 2ga. There's a 1ga negative lead from the battery compartment to a negative bus behind the engine. The echo charger is next to the  "start battery". The On-Off switch on the panel just carries house loads. The original 4ga "Common" behind the panel carries the shore charger power to the "start battery" via the engine positive bus. The original 4ga #1 lead carries the shore power charger to the "house bank", there's a 30A Maxi fuse at the battery box. The original 4ga #2 lead connects the On-Off panel switch to the "house bank" with a 150A breaker at the battery box. If I trip this later breaker, I isolate the house circuit when I want to equalize with the shore power charger. I also have a "keyed" battery switch under the head sink to combine banks in an emergency.

Yes, I'm going to run the 6ga ground leg from the shunt in the battery box to a power post behind the panel. Then, move the negative over from the shore power charger and run a jumper over to the negative bus behind the panel. I have a newer panel, but I'm saving rewiring the rat's nest behind the panel for retirement (or unemployment). I don't recall a 4ga negative coming to the negative bus behind the panel, it's maybe an 8 or 10Ga from somewhere? More research required.

Thanks for making me think about stuff a bit deeper.

[Stu Jackson]

1.  The On-Off switch on the panel just carries house loads. The original 4ga "Common" behind the panel carries the shore charger power to the "start battery" via the engine positive bus. The original 4ga #1 lead carries the shore power charger to the "house bank", there's a 30A Maxi fuse at the battery box. The original 4ga #2 lead connects the On-Off panel switch to the "house bank" with a 150A breaker at the battery box. If I trip this later breaker, I isolate the house circuit when I want to equalize with the shore power charger. I also have a "keyed" battery switch under the head sink to combine banks in an emergency.

2.  Yes, I'm going to run the 6ga ground leg from the shunt in the battery box to a power post behind the panel. Then, move the negative over from the shore power charger and run a jumper over to the negative bus behind the panel. I have a newer panel, but I'm saving rewiring the rat's nest behind the panel for retirement (or unemployment). I don't recall a 4ga negative coming to the negative bus behind the panel, it's maybe an 8 or 10Ga from somewhere? More research required.

Craig, you have a very good setup, and it's becoming harder for me to keep track of all the great electrical upgrades many of us have done!

1.  Based on my research on the dual circuit switch, I find no reason to ever have to combine both banks.  Either one is working and the other is not, or vice versa, in which case you'd never want to combine them.  If they're both working, you wouldn't need to either.  That's my rant on your already deleted 1-2-B switch.   With a little planning, finding a way to power you house load from the reserve bank without combining the banks is something to consider.  I haven't figured that out yet with what you have, but it's gotta be easy.  Your OEM 4 ga. from the old switch that you connected directly to the charger and runs to the house bank is adequate to carry the charger input, so there's no reason to move it to the banks.  Hope I'm savin' ya some unnecessary work now that I understand your setup.  You don't need to trip that breaker to equalize, just turn the switch off.  When I equalize, I can run my house loads on the reserve bank and listen to music as the house bank bubbles away.

1a.  I'm a little confused about the (3) 4 ga. from the old 1-2-B switch.  You said 4 ga. "Common", #1 and #2.  #1 and #2 went from the switch to the two battery banks.  On my boat there were two 4 ga connected to the common.  One went to the alternator and one went to the starter.  This, I learned, was unusual, and maybe only on the earlier or earliest boats, until the factory learned they could do it with one wire and a small jumper wire between the starter and the alternator.  It sounds like you only had one.  My confusion stems from you using the common for the shorepower charger to the reserve bank.  It sounds like you just reused it and rerouted it a bit.  Am I close?  In that regard, why not eliminate that and use the echo charger to charge the reserve bank and use only one output from the shorepower charger to the house bank?  The echo charger should get the incoming current and go to the house bank first and then feed the reserve bank.  It's a little unclear in your description (although not asked for, but thanks for the details) because you say the echo charger is close to the reserve bank.  Just a piddly little detail because I've discussed the wiring of combiners and echo chargers with many folks who believed their reserve bank needs the charge first, which is not the case.  Location does not mean it's wired that way, of course.  The description makes sense, ya did good!

2.  The wire from the negative bus is probably OEM 10 ga., understandably meager.  Did I say 4 ga.?  I've found using the Power Posts to be useful closer to the batteries, so you can probably use a less expensive bus bar to do that behind your panel, if it fits.  I follow your reasoning about connecting them, since it sounds like your shunt is kinda like a NDP for you.  What monitor do you have?  Just check before you do this about your grounds:  sketch a diagram of the grounds and the wire sizes and how they all connect, more easily done say on a floor plan of the boat like my wiring diagram and John Gardner's, and make sure there's a reasonable continuity in power directions through the wire and wire sizing.  Short runs of smaller wire will work on the whole ground circuit wiring gorilla!  (NOT guerilla - thanks, Captain Ron! )

Given my condition, this is much appreciated (for my sanity) and I enjoy getting into the details.  

[Craig Illman]

Stu - Wriing diagram.

Yes, it's a bit redundant to have the echo charger and have a direct, albeit long, leg from the shore power charger to the start battery.

Equalization, yes others have said it doesn't bother the stereo. I don't always feel so lucky.

Craig