SU469 House battery duration questions

[virtualburton]

Hi all, I've seen lots of good info on here about batteries and I know there are some real experts here so I'm hoping someone can help me figure this out.

I have a 2013 Sun Odyssey 469. It has 7 new (1 year old) AGM House batteries, wired in parallel like this:



I got the boat in June and after my first couple of trips I found the house bank drops below 10.5-11 volts within about a day and a half. I was quite surprised at this so decided to buy a battery monitoring system. I selected the Simarine system and installed a SC503 shunt as indicated above. I also installed a seperate SCQ25T which has 4 25A digital shunts so I can further break down what's using the power.

I installed them on the weekend and configured them. Looking at the diagram above, 5 batteries are on the starboard side under the bed and the other 2 are on the port side. I configured the Simarine Pico monitor like this:

7 batteries, all the same, here is the label:



They are all 12V, c20 rating is 115 amps, C5 is 96 amps. Configuring the Simarine I calculated total amp-hours of the house bank as:

Total C20 - 7 * 115 = 805 amp hours, Total C5 - 7 * 96 = 672 amp hours. I mailed Simarine to confirm and they said this is correct. Is it?

They appear to be wired together in parallel properly. After configuring the system I turned off the charger at about 10:30 am. By 18:00hrs the same day the bank was down to 10.2 volts and the schemer/Jeanneau panel low voltage alert had gone off. I turned the charger back on. The submarine Pico panel showed this at about 15:00 hrs, after only about 5 ½ hours running. (99 is the percent remaining, SC503[1522] = 6.88A is the total amp draw at that moment, Refrigerator is one of the digital shunts and was off at that time, 6d 07h is saying the bank should last 6 days and 7 hrs at current draw, 796.98ah is the remaining amp-hours, 18.4 degrees is the temp of the battery).



Now what I'm trying to figure out is why the bank is dropping so fast - it's like it only sees 2 of the batteries or something...

I watched the shunt most of the day while the charger was off and about the max current draw was 9.8 amps. The rough breakdown is the fridge uses about 5-6 amps when it cycles on, the rest is approx 4 amps and that's lights, the stereo, the scheiber panel, etc.

Can anyone offer some advice on what I've shown here, what your experiences are with your house batteries and based on the digram I made after tracing all the battery cables, is there anything wrong with the way they're wired that would not make them work properly in parallel?

As always, Thanks in advance.

David

[sitara]

David, Should your shunt be wired into the negative side? between the battery and the ground buss. It is in my system (a different brand). Other than that the wiring looks right. (positive in one end of the bank and negative at the other end). This does not explain the quick discharge. Your current draw ~9 amps looks about right. My questions: are the batteries charging fully? and have you got a faulty battery?

I have about 300 amp hours storage in my boat and with refrigerator, lights, TV  etc I loose about 10-15% capacity overnight.

Hopefully some others will have more answers.

Rob

[virtualburton]

Hi Rob, thanks for the info. I asked Simarine about that. I wanted to install it in the negative side but the wiring was much harder so that's why I put it there.

Appreciate the help and info...

David

[moonshadow]

A few points from my experience with my 469.
My battery areas are full with three on Stb side and two on port side the rest of my batteries are not house, they are engine start and genset start and wired separately. I’d like to see where you fit the rest, I could always use more battery power.
The Sheiber panel never sees real voltage. It is installed way downstream and I think for battery status it’s best ignored.
But… a 10.2 volt reading is very suspicious for a dead cell in one battery. In order to check this you should test each battery separately while totally disconnected from everything. If one battery reads 10.2 v I would disconnect it from the system and see how that works.
I never had good luck with Wet or AGM batteries. I switched to firefly carbon foam and I’m a lot happier. Worth reading about.
I am not familiar with the monitor you have. But every one I am familiar with needs the shunt on the negative side. From reading various sources it seems that improper installation is the main cause of monitor problems. So I would go back and check that.
I have about 400 w of solar panels on my boat and the batteries are fully charged mid way through most days running fridge and freezer. I don’t often use shore power to charge. As days get shorter this will not keep up with both fridge and freezer so they need some additional charge every few days.
And if you have the two Cristec chargers I would read that manual and double check with a volt meter that you are getting what you want. The diagram of the dip switches is not very good. Hard to tell if “on” is up or down.
Good luck. This was a frustrating learning area for me and it took some time to get it all figured out.
Paul

[rxc]

You need to recharge the batteries again, and take a bunch of measurements with a voltmeter, at the terminals of the batteries. Use a real voltmeter, not the battery monitor.

As the batteries are charging, what is the charging voltage at each battery? What is the voltage at the ends of the string of batteries? Take this several times, as the batteries are gradually charged. Make sure the leads are on the battery posts, themselves, not the wiring connectors.

When you decide that the batteries are charged, and disconnect the charger, what is the voltage on each of the batteries and the entire string? Measure this with the entire bank disconnected from the loads. Also, make sure that the battery charger is disconnected, because it might have something going wrong and be an attached load.

Wait an hour with no load at all,and then do the voltage measurements again.

If you can, wait a few more hours and measure the voltages again.

With that information, you should be able to determine (1) Whether the battery charger is working and charging up to the float limit for AGM, and then whether each of the batteries is being charged properly, and whether the entire string is connected properly.

[virtualburton]

Thanks... I am guessing I would have to disconnect each battery as I measure the voltage because they are currently all wired together so theoretically I should get the identical voltage anywhere in that "string"...

The charger is an interesting thought... I agree I should isolate it from the house bank before doing these measurements... perhaps it is drawing them down?

Thanks for the advice and info. I'll report back once I've had a chance to do this.

One other question: In the SO469/479 schematic, it shows the house batteries in parallel (5 of them, I have 7) but the main cables FROM the parallel bank that go to the loads BOTH come from the last battery in the series. On my boat, someone has wired the positive from the POS on the first starboard battery and the negative from the NEG post on the last battery. Why would they do this? it seems unnecessary to me and makes the POS wire very long and hence very large (4/0 wire). Taking it from the last battery like the NEG would be much shorter... any ideas as to why?

Thanks/merci,

David

[Don Reaves]

Sept 17, 2021 19:46:32 GMT virtualburton said:

Thanks... I am guessing I would have to disconnect each battery as I measure the voltage because they are currently all wired together so theoretically I should get the identical voltage anywhere in that "string"...

The charger is an interesting thought... I agree I should isolate it from the house bank before doing these measurements... perhaps it is drawing them down?

Thanks for the advice and info. I'll report back once I've had a chance to do this.

One other question: In the SO469/479 schematic, it shows the house batteries in parallel (5 of them, I have 7) but the main cables FROM the parallel bank that go to the loads BOTH come from the last battery in the series. On my boat, someone has wired the positive from the POS on the first starboard battery and the negative from the NEG post on the last battery. Why would they do this? it seems unnecessary to me and makes the POS wire very long and hence very large (4/0 wire). Taking it from the last battery like the NEG would be much shorter... any ideas as to why?

Thanks/merci,

David

The reason for taking the positive from one end of the bank and the negative from the other end is to ensure that each battery sees the same length of cable in the entire circuit. This keeps them balanced. Remember, the cables themselves are not perfect conductors and offer some resistance.

If you have a dead cell, that battery would probably get quite hot as the others try in vain to charge it up to 12+ volts. It's worth noting whether any batteries are warmer than the others.

[sitara]

David I believe your battery wiring is the optimum way to do it. It is what I have. I have seen this recommended somewhere but am not sure of the reason.

Rob

[virtualburton]

excellent info - Thanks guys.

[zaphod]

So to be clear, did Simarine say it was OK to put the shunt on the positive?

Assuming you don't have any connections to your batteries that aren't shown on your diagram it is very likely you have a bad battery causing the bank to discharge.

When you isolate the bank and turn off your charger, what voltage do you see? Does that voltage drop over time?

Definitely take the time to disconnect and test each battery.

[NZL50505]

Agree the most methodical (although time-consuming) way to isolate the problem here is as follows:

1. Confirm charging profile of your charger is set correctly to batteries. Don’t overlook this step. You need to check actual product spec brochure for your brand of batteries to confirm correct V for Bulk, Absorption and Float phases. Then ensure your charger is within spec. This does not just mean setting your charger to AGM or Lithium as these are generic settings that might differ from your battery manufacturer’s requirements materially such that you are undercharging or overcharging your batteries (in a way that could be killing them). I know this from bitter & expensive experience and killed a brand new house bank of AGMs in just 9 months because my charger was 0.3-0.4V out of spec. I had to replace my charger because my old one did not allow customised settings for Bulk / Absorption / Float to reach the required V profile.


2. If you now believe your charger is operating correctly then fully charge each individual battery one at a time (min.12 hrs and take note of final float V) ensuring battery has no other wires connected.

3. Disconnect fully charged battery from charger (and all other wires) and allow to sit ‘on the bench’ for 24hrs. Test unloaded rest V after 24hrs and it should be in the range 12.6 - 12.8v. Anything lower is suspicious. If any battery fails this test then you might have found the culprit already.

4. But if after putting each battery through this process they are all behaving normally then you might still have a problem that can only be identified via a load test. For this you probably need to hand turn over to a pro electrician who can do a proper load test for each battery to identify the culprit.

If you do find you have one dud battery but the others are still OK then you might try just removing it from the bank and see how the rest perform without it - seeing as you already have a pretty decent total bank capacity as-is. Just trying to save you the cost of buying another battery if not immediately necessary.

Good luck!

[virtualburton]

Sept 17, 2021 22:17:11 GMT zaphod said:

So to be clear, did Simarine say it was OK to put the shunt on the positive?

Assuming you don't have any connections to your batteries that aren't shown on your diagram it is very likely you have a bad battery causing the bank to discharge.

When you isolate the bank and turn off your charger, what voltage do you see? Does that voltage drop over time?

Definitely take the time to disconnect and test each battery.

Yes, they said it was fine. I actually sent them that diagram - that's why I drew that up.

when I isolate that bank the voltage holds steady, but I didn't wait long enough. I will try in a day or so and will disconnect the charger and then disconnect it and see if it holds for 4-6 hrs. I will also check voltage on each battery.

Thanks!

[virtualburton]

Sept 17, 2021 22:59:01 GMT NZL50505 said:

Agree the most methodical (although time-consuming) way to isolate the problem here is as follows:

1. Confirm charging profile of your charger is set correctly to batteries. Don’t overlook this step. You need to check actual product spec brochure for your brand of batteries to confirm correct V for Bulk, Absorption and Float phases. Then ensure your charger is within spec. This does not just mean setting your charger to AGM or Lithium as these are generic settings that might differ from your battery manufacturer’s requirements materially such that you are undercharging or overcharging your batteries (in a way that could be killing them). I know this from bitter & expensive experience and killed a brand new house bank of AGMs in just 9 months because my charger was 0.3-0.4V out of spec. I had to replace my charger because my old one did not allow customised settings for Bulk / Absorption / Float to reach the required V profile.

~ ~

Good luck!

Thanks for all of this. The charger is the standard Cristec - my boat has 2 of them, one for house and the other for the thruster batteries. 

I checked that the dip switch was set to AGM, and it was, but did not see the other settings... I will investigate. It seems to float at 13.6v.

Thanks again for all the help, much appreciated.

David

[NZL50505]

Ok looking at the product spec for those batteries it looks like for a voltage controlled charger (which I presume your Cristec is) then your Bulk / Absorption voltage should be 2.45V per cell (6x2.45v = 14.7v). And then for float it should settle at 2.27V per cell (6x2.27v = 13.6v).

You said you are seeing float at 13.6v which sounds good but have you observed what the peak V is when you start charging the batteries after they are discharged and what is the highest you see it get to as it reaches end of Bulk and enters Absorption phase? Because according your battery spec this should be 14.7V. This is on the high side but happens to be exactly the same as the AGMs I have in my boat. And I found that the Cristec charger that my boat came with could not get up to this, it peaked at about 14.3-14.4V and that shortfall of only 0.3-0.4V during the important Bulk & Absorption phases was enough to kill the batteries after 9 months (build up of sulphation that could not be re-conditioned away even using a big equalisation charger). I had to replace the batteries and of course replaced the aging Cristec with a programmable Victron charger unit that I calibrated to achieve the 14.7V level I needed for Bulk & Absorption (and I also happen to need 13.6V for float). No problem since then.

[virtualburton]

wow, great info. I did not notice the specific voltage when I started re-charging, but will check it again. It was over 14v but sure how high.

I'll report back - thanks a ton,

David

[NZL50505]

For this critical test of your setup do not trust the voltage readout of your display (even if recently calibrated). Instead use a voltmeter to measure the voltage directly at the battery terminals to eliminate any other inaccuracies.

[moonshadow]

You said your chargers were set up very differently from mine. I would check that. My two 30 amp chargers are basically set up in parallel to charge the house bank at 60 amps. There is a charge divider for the engine and gen battery, and the bow thruster batteries are charged via a 12-24 v step up transformer. (Four 12 v batteries in pairs for 24 v thruster). If your two chargers are set up this way also perhaps they are not set up with the same settings and one is seeing the voltage from the other and not providing what you need?
Not that I fully understand all this, but this setup makes sense. No reason for a charger in the back of the boat for the bow thrusters in the bow. And they really don’t draw down batteries very much, just short bursts of a lot of current.

[rxc]

Lots of good advice. To address the matter or disconnecting batteries from one another, don't do that right away. Just measure each battery, with a voltmeter leads touching that actual battery terminals on each battery, one at a time. You are looking to see if any of the voltages are different. This is the first, simple test to identify a bad battery in the string. Taking the readings several times will give you some indication that the bad battery is drawing down the others.

If you find a suspect battery, disconnect it from the string and do the test again.

The comments about the battery charger are very important. You have to measure the voltage that the BC is putting out (1) at the nearest point close to the charger, and (2) at the ends of the battery string, to see whether there might be a bad connection along the way.

One last thought. You have all these batteries - how far apart are they, in terms of wiring distances, inside the boat, and how large are the wires between the batteries? If you don't know, post a photo. If they are too small and/or too far apart, the batteries might be suffering from too large a voltage drop.

[virtualburton]

Great information from all you guys and I really appreciate it. What a great group and site. Thanks everyone.

Here's the starboard bank of 5:



And here's the starboard 2:



The only really long cable is the Positive from the outboard end of the starboard side.

I have a friend staying on board this weekend so had to put the bed back together. I'll continue Sunday once he's left and will post my findings of the voltage measurements. I also need to look into the Charger configuration and connections. There is a battery isolator - you can just see it in the bottom photo on the left. I need to trace those wires because I have found the wiring in this boat doesn't follow the schematic exactly, and TBH the schematics are quite poor.

Thanks,
David

[NZL50505]

My final additions before you start testing stuff on Sunday:

1. Agree with previous comment to test the output voltage of the charger at the charger itself - and compare with voltage at nearest battery in circuit. This is to confirm any voltage drop between charger and battery. The best chargers have a voltage feedback wire from the battery bank back to the charger so if necessary the charger can increase its output voltage to compensate for voltage loss, in order to achieve the target V at the batteries themselves.

2. If you have really got 2x chargers jointly charging this bank then things become more complicated again. In theory this setup could work OK if everything calibrated and operating correctly but… if something isn’t working right this makes it much harder to isolate and correct.

[rxc]

Ahhhh... magic words - battery isolator. Depending on how this is hooked up, it may have a significant voltage drop thru it, leading to your batteries being undercharged. That is why it is important to measure the voltages carefully, with a voltmeter, and putting the probe on each battery terminal coming out of each battery - not on the lug for the wire. You should also measure the voltage at the terminals on the battery isolator to see what the voltage drop is. It can be on the order of 1v, which would be huge for charging purposes.

Oh, and battery isolators are know to fail, and un-isolate the batteries, so that will need to be checked, as well, if you decide to keep it. I prefer a voltage sensitive relay, rather than an isolator with diodes, but that is a personal preference.


Your wiring looks good - appropriately large (probably 2ga). And nice to see the battery fuse.

Where is the engine starting battery? (I don't know the SO469)

[moonshadow]

On my 469 the engine start battery is in the engine compartment. Lots of room in there so it’s a good distance away from anything Hot.

[virtualburton]

Thanks for the tips guys.

My engine starting battery is under the stairs ahead of the engine in the engine compartment.

Also a clarification - there are 2 chargers on my boat, but charging different banks, one for the house bank and the other up forward under the bed charging the thruster bank. They are not interconnected in any way.

Thx, David

[NZL50505]

Sept 19, 2021 18:51:37 GMT virtualburton said:

Thanks for the tips guys.

My engine starting battery is under the stairs ahead of the engine in the engine compartment.

Also a clarification - there are 2 chargers on my boat, but charging different banks, one for the house bank and the other up forward under the bed charging the thruster bank. They are not interconnected in any way.

Thx, David

Ok that makes it easier. What are your thruster batteries, btw? Are they behaving OK?

[moonshadow]

My thruster batteries are four 12 v AGMs under forward berth forward of the water tank. 24 v thruster.