Batteries charging daily but still decreasing charge overnight

[mystic_voyager]

Ideally your battery bank and charging system should be a balanced match. I used to have more batteries than I should have had given my charging system. I recently reduced my battery capacity to better match my solar and wind charging systems and amp hour usage. (I hate running the auxiliary engine to charge batteries, so I don’t even factor it into the equation.) The new reduced size battery bank functions better, with the refrigeration batteries dropping to as low as 85% on a overnight without wind and reaching 100% during sunny days. The house bank rarely goes below 95% on the same night.

A Battery Monitoring System is a must have item. Checking just voltage can be totally misleading. With a BMS you see the deficite or charge in terms of amp hours on a real-time basis.

An energy audit is key. I replaced every incandescent bulb with LEDs. I better insulated and reduced the size on my frig. I replaced all of my old navigation electronics, including radar, with modern low current models. I checked all wiring for corrosion.

I run three battery banks: House - Trojan T-105s, Refrigeration - T-105s, Starting - group 31.

I have a little over 300 watts of solar and very theoretical 400 watts of wind that rarely reaches more than 10-15 amps. My engine alternator is the original 35 amp unit that came with the Yanmar.

Many people prefer AGM to flooded lead acid batteries. I’m okay with the Trojan T-105s. I find them very reliable and more economical in the long run. I installed a Flow-Rite Pro-Fill central battery watering system that makes flooded lead acid battery maintenance very easy.

[wingssail]

Originally Posted by terah

In Athens now. 6 x T-105's ordered, will have them tomorrow. 1000 euros delivered, which seems pretty comparable with UK prices.

I think that is a good choice. Simple, strong, reasonably priced. We're on our third set (after 20 years) and they are getting weak, but I will replace them with similar this fall.

I think you will find a big improvement because it looks to me that your charging system is adequate but that the previous batteries had reduced capacity (probably just old). It doesn't matter how much charge you try to put on the batteries, if they are only going to hold, and put out, 100-150 amp hours once you reach that point during charging they won't hold any more. At night, when solar shuts off (4:00PM?), if you are taking out 8-10 amps you will exhaust that capacity in 12 -14 hours. This is what you are reporting, so it sort of matches.

By installing 6 new T105's you should now have 675 amp hour house bank capacity and you should be able to use over 300 amp hours. Your solar capacity should allow you to resupply at least 200ah per day and with that you should be able to run your refer and freezer, assuming efficient systems.

[john61ct]

You can have as huge a battery bank as you like compared to the solar panel daily power input.

The only ratio the really matters is that you only discharge 80-90% of what is going in each day.

But you need the right gear and knowhow to track those numbers.

Too small a bank means DoD is too high, shorter lifetime.

The downsides with "too large" a bank is the extra weight carried, and the extra upfront cost, offset by extended longevity.

The upside with extra capacity is the ability to ride out cloudy weather longer, but you do in the end need an on demand dino juice charge source to give getting SoC back up a boost so solar only needs to handle the long tail.

[curtis742]

Charge the battery bank during the day late in the evening disconnect all the positive battery jumpers and measure the voltage of each battery. This will show any weak battery in the bank. Turn your freezer off or fill it with water bottles. An empty freezer runs a great deal more than a full one. Last, at sundown disconnect the solar panels from the system to see if the voltage is leaking back through the panels. After all is said and done and no problem is found get a bigger bank or go to bed early. Also you can charge your bank from shore power and take all the batteries to an auto parts place and have them check each one with an electronic load tester. Most place will do this at no charge in the hopes of smell you new batteries. Just be sure the batteries are fully charged before taking in for testing.

[terah]

OK, so the batteries are all in place, despite the sparky helping me telling me repeatedly I've bought the wrong batteries (these must be vented outside, he has much better sealed ones I should have bought).

I'm just working out how to set all the chargers now. The data sheet for the T-105's says @ 25 degrees C bulk should be 14.82v and float 13.5v with 5mV/deg C variation. The SmartSolar app has temp compensation but doesn't specify which temperature the voltages are set at. Is 25 degrees standard?

[mitiempo]

Yes 25c or 77f.

[Pete7]

Originally Posted by terah

despite the sparky helping me telling me repeatedly I've bought the wrong batteries

Well yes you have, you need to buy the older el-cheapo sealed batteries he can't off load on anyone else and are now likely to spend their 2 second winter sitting on a shelf without a maintenance charge.

Pete

[terah]

The data sheet for the T-105 (https://www.trojanbattery.com/pdf/da...ata_Sheets.pdf) says the temperature compensation should be 0.005 volt per cell for every 1°C above 25°C

So 3 cells per battery = 15mv/C

The SmartSolar input for temperature compensation has a message:

"Coefficient is in mV per degree Celsius for the whole battery bank, not per cell"

By 'whole battery bank' does that mean per battery, per paired batteries, or the entire bank? The max value it lets you set is 30mV/C. The current value is also -ve - is that right?

[terah]

Originally Posted by Pete7

Well yes you have, you need to buy the older el-cheapo sealed batteries he can't off load on anyone else and are now likely to spend their 2 second winter sitting on a shelf without a maintenance charge.

Pete

No el cheapo nonsense here - they were 'MARINE' batteries...

[Wolfgang.Schau]

You said you have a refrigerator, freezer plus none-LED lights. I think this easily can add up to 15A.
Please bear in mind, a 360Ah battery will give you only 180Ah before it drops below 11V.
How old are your batteries? They usually last only 4 years, depending on the amount of cycles. Go 100% LED, including your navigation lights, this will save a lot - and turn the freezer off if not needed.

Also, you will get only enough power from your panels between 9am and 3pm, i.e. the remaining 18h you may already start depleting your battery.

I use a power monitoring center from Sterling, with 4 inputs. The 4th channel has an Ah counter which will tell you the truth.

[john61ct]

Originally Posted by terah

No el cheapo nonsense here - they were 'MARINE' batteries...

I hope a joke, right?

[john61ct]

Originally Posted by terah

The data sheet for the T-105 (https://www.trojanbattery.com/pdf/da...ata_Sheets.pdf) says the temperature compensation should be 0.005 volt per cell for every 1°C above 25°C

So 3 cells per battery = 15mv/C

The SmartSolar input for temperature compensation has a message:

"Coefficient is in mV per degree Celsius for the whole battery bank, not per cell"

By 'whole battery bank' does that mean per battery, per paired batteries, or the entire bank? The max value it lets you set is 30mV/C. The current value is also -ve - is that right?

Really bank voltage, if 12V then 5x6=30mV

[Wolfgang.Schau]

If you believe a 360Ah battery will give you 360Ah - you may as well believe in Santa Claus. The battery type and the load current have a complex relationship what you really get out of it.
The advantage of Marine batteries is they don't go bad when deep cycled. A normal car starter battery, once deep cycled (below 9V) you can probably throw away. A Marine battery should recover.
Anyway, making a sound design, you should never plan on discharging more than 50% of the Ah of the bank. Also, after several hundred cycles, your battery will lose capacity, no matter what the age is. You will experience your starter battery (I hope you have a separate on) will last longer in years compared to your domestic battery. If you intend to charge separate banks with on set of solar panels, use a battery separator like a BS160, not Diodes.

[terah]

Originally Posted by john61ct

I hope a joke, right?

Yes. Though the guy seemed quite serious.

Originally Posted by john61ct

Really bank voltage, if 12V then 5x6=30mV

Brilliant, thanks!

Originally Posted by Wolfgang.Schau

... If you intend to charge separate banks with on set of solar panels, use a battery separator like a BS160, not Diodes.

So this is where it gets complicated. I have three separate banks and three separate charging systems.

Bank 1: 1 x Banner P100 44 - engine starting
Bank 2: 3 x 2 x Trojan T-105 - house
Bank 3: 2 x Optima Redtop AGM

Charger 1: Cristec CPS2 with outputs for each bank
Charger 2: Mastervolt alternator + Alpha Pro which connects to all banks via a battery isolator
Charger 3: Victron SmartSolar 100/50 which connects only to the house bank

The issue with the CPS2 and the Alpha Pro is that they can only be set to one battery profile for all banks. The CPS2 also only has fixed options selectable by dip switches.

The T-105's have a detailed spec sheet which says 14.82v for absorption and 13.50v for float, and temp compensation as above. I've not found exact values for the other batteries other than a vague 14v - 14.8v recommendation for the Optima's.

The current setting on the CPS2 is listed in the manual as 'Lead Sealed', but is the closest to the T-105 requirements with absorption 14.3v and float 13.6v (the only setting higher is 15.1v and 14.4v). I haven't measured the current values of the Alpha Pro but the book has the defaults as 14.25v and 13.25v.

The SmartSolar is now set to 14.82v, 13.50v and -30mV/C for temperature compensation.

Does it make the most sense to leave the CPS2 and Alpha Pro at their current settings? The other banks seem fine and the solar should push the house bank up for the difference.

A final question is how do the various chargers interact with each other? I assume there's no issue form a voltage point of view but is there a risk of overcharging due to absorption times being out of sync? Say the shore power is on from 2am to 8am so the batteries get 6 hours in absorption, we then leave the dock as the sun comes up and the solar gives another 6 hours absorption, then at 2pm the wind dies so we start the engine and the Alpha Pro gives nother 6 hours in absorption.

[john61ct]

What I would do

All charge source direct to House, use its needs to adjust / optimize each's profile.

Starters less in need and less important, as they need replacing over time match the House batts, or at least same chemistry, similar profile.

Connect from House to each of the others with a simple but robust VSR / ACR, like Blue Sea, ampacity to match largest current through that connection, this being best but pricey

https://www.bluesea.com/products/762..._-_12V_DC_500A

Some decent ammeter, keep an eye on possible overcharging (min absorb too long) but really NBD with FLA as long as you keep water topped up.

More usual is the opposite problem as MaineSaile dubbed premature infloatulation.

____
Of course if House is getting to 100% via endAmps every day, you could always keep a charge source dedicated to its own isolated Starter batt.

But conditions change, the "put everything to House" scheme is really a sound default.