Batteries charging daily but still decreasing charge overnight

[ohgary]

Also look for phamtom loads. SO much of modern electronics have wall warts and they draw power even when not powering devices.

A snap on current meter is good for AC lines

[Locquatious]

Remove the loads from the batteries and let them recover in the no load condition for say 15 minutes. Then measure the battery voltage.

[hellosailor]

Terah-
The only way to actually solve battery mysteries is to auger a chicken and then sacrifice a goat.
Although, some may prefer the relentless application of logic, which is a foolish way to do things, isn't it?

You need to start by finding out the manufacture date of the batteries. It is stamped on each one, usually hidden under the top inch of the label on one of the sides. You may need to call Zenith to decode it.
That won't tell you if they have been abused or are being mischarged, but if they are 6 to 8 years old...they're just OLD and ready to go.

Then you need to find out exactly what voltage Zenith specifies, for those exact batteries, for bulk charge and float. And ideally, your charger is temperature compensated as well? There's a number for that, too.

Then you go about measuring the actual charger output, the actual state of the batteries, the actual load that is being put on them during the day and night. You run the numbers.

Since cheap multimeters are often off by a significant number (like 0.2 volts, which is 20% of a charge) you're best off buying a calibrated Fluke multimeter for $100-150 because it will last you a lifetime and it will not deceive you. Even when you add a power monitoring system later on, the Fluke can be used for reality checks.

And if you are lucky--they just need replacement, because you can't "expand" an old battery bank, you need to replace it all with *matched* new batteries. Expanding it is just a waste of the good new battery, which will be busy trying to save the old ones instead of expanding your bank.

Sound too complicated or too long?

Then you go back to augering the chicken and sacrificing the goat.

[a64pilot]

A lot of well meaning advise, unfortunately a lot of it will lead you down dead ends.

Look here and read
https://marinehowto.com/category/electrical/batteries/

Believe what you read here, not what you hear on this or any other internet site with well meaning individuals.

First you have to have a three stage battery charger, if you have an old single stage, I'm afraid it's worthless, although it can be argued they worked for decades, well they worked, just not very well.
Any good charger will tell you it's output in voltage and amps, subtract your house load and you can tell what the battery is accepting, worst case you should be able to turn the battery selector off and see how many amps the battery is accepting.

Read Maine Sails articles, digest them and you will be a whole lot more informed than you are now, and then you will know what questions to ask and can understand better.

Trust me, this whole battery thing is as complex as your willing to make it. Some say heck with it, Ill just buy new batteries when the old ones go dead, no need to obsess over cheap batteries, and you know, that works too. Just they buy more batteries, but save themselves from all the worry, depends on what is important to you

[a64pilot]

Then here
What Is A "Deep Cycle" Battery? Photo Gallery by Compass Marine How To at pbase.com

[a64pilot]

And here as well
Installing A Marine Battery Charger Photo Gallery by Compass Marine How To at pbase.com

[BruceS]

The reported low voltage could be when the freezer & fridge are both on?
When it reports 11v, turn EVERYTHING off for an hour & THEN read the voltage.
But I agree 50% is 180. (NOT 130Ahr)
180 over night running your 'stuff' will drain it.
Turn off your freezer ASAP.

[senormechanico]

But first, eat all the frozen food.
We don't want to hear about any deaths from food poisoning !


<sarc>

[Stu Jackson]

In addition to Maine Sail's website, which is excellent, there's this I put together with many links to his contributions beyond his own 'site.


Electrical Systems 101


You figure trailing amps by turning off your charger and then turning it back on to get back to absorbtion voltage and read the amperage. When that amperage is < anywhere from 2 to 0.5% of your house bank amps, it's full.

[hzcruiser]

Originally Posted by a64pilot

[...]First you have to have a three stage battery charger, if you have an old single stage, I'm afraid it's worthless, although it can be argued they worked for decades, well they worked, just not very well.
[...]

The OP mentioned he has a Victron 100/50, which I'd say is state of the art. He later also posted a screenshot of his phone.


I agree with others, the load seems too high for the remaining capacity of the batts. And yes, if you can turn off the freezer, do that ASAP.

[mitiempo]

First, the load is too high for the bank size. Battery condition - nobody knows.

I agree you have to replace the entire bank at the same time with a larger bank - do not mix old and new.

Battery monitor like a Victron BMV should have been one of the earliest purchases. You need to know your consumption. A Smartgauge will not show this but can be a nice addition later if desired. My guess is your consumption is very high.

As long as you are on the boat with loads - freezer, etc - turn float off. Batteries do not charge at float voltage so you are wasting good sun by having float kick in before a full charge. Easiest way is to change float voltage to bulk/absorption voltage. The batteries will never be over-charged as the loads are ongoing.

[noelex 77]

The voltage reported by the Victron of 14.2 is a puzzle. If absortion was set at 14.4 the controller should have been reporting this as the maximium voltage.

I suspect the Victon was set with an absortion voltage of 14.2 not 14.4v.

Changing the absorption voltage to 14.7 from even 14.4 (or likely14.2) as you have done will make a huge difference to the charging rate

Your considerable solar input Is not keeping up with demand so your consumption must be relativly high. This in conjunction with a small battery bank is not a good combination, but the first step is sort out the charging. Your previous 14.2v is not enough to reach a reasonable state of charge in a solar day.

[Frugal]

If you suspect one of your batteries a quick way to test is to run an inverter on each battery with a fixed load ( toaster - 1,000 watt or microwave 900 to 1200 watt ) for a fixed time, say 1 minute. Check the starting and finishing voltage of the battery. The heavy draw of around 100 amps on the battery will show a drop in voltage or if a dud will probably disconnect from low voltage.
I check my 10 by 100 a/h VRLA batteries annually by this method and have replaced three over the last five years.

[terah]

OK, wow. Lots of suggestions. Lots to try. I've started to read some of the links provided but there's a fair bit to process, will need to come back to it.

Last night we were on shorepower and I stop/started the battery charger to keep it in absorption. I had also changed the settings on the SmartSolar to absorption 14.7v and float 13.7v. The SmartSolar this morning reported max V as 14.56v. I'm not sure if that difference is due to cycling the battery charger, or the solar controller change. We'll be anchoring out tonight so will see what happens tomorrow.

I've started to put together an energy budget based on @Stu Jackson's - I'm just using values off the ammeter on the electrical board so it's not precise, but is something to get started on until I can pick up a battery monitor.

I've also done a quick check by disconnecting all power sources and isolating the house bank from the boat and from each other. Immediately after disconnecting I get:

Batt 1 12.92
Batt 2 12.61
Batt 3 13.04

Then after 30 mins:

Batt 1 12.80
Batt 2 12.10
Batt 3 13.04

I only have enough equipment to test a small load on Batt 2 (a little power brick charger), but it immediately dropped to 11.71v. I assume from the above that Batt 2 is goosed, and has probably been bringing down the other batteries?

For now we have:

1) Eaten all the ice lollies in the freezer and sacrificed the green beans
2) Turned the freezer off
3) Removed Batt 2 from the bank

[noelex 77]

Originally Posted by terah

I had also changed the settings on the SmartSolar to absorption 14.7v and float 13.7v. The SmartSolar this morning reported max V as 14.56v

Is the temperature compensation on?
Is controller in a hot area.? What is the battery temp?

Yep. Bat 2 is toast. The voltage difference between Bat 1 and Bat 3 is not promissing, but I think you are doing the right thing for the moment ditching Bat 2 and resetting the charge parameters.