Did Victron BlueSolar Kill My Batteries?

[john61ct]

Originally Posted by zstine

I turned the solar charger back on (it was off/disconn for 2 weeks) and I could not recreate the problem. The batteries were at 11.2V and the charge controller was reading only 0.2V higher, fine. I allowed it to charge for 30 minutes and the voltage difference was never more than 0.2V.

Zach, was Justin able to help?

[Captain Bill]

Originally Posted by zstine

OP here. I did some more checks to determine why the Solar Controller and actual voltage at the batteries was different by over 2V. Before disconnecting the old batteries, I turned the solar charger back on (it was off/disconn for 2 weeks) and I could not recreate the problem. The batteries were at 11.2V and the charge controller was reading only 0.2V higher, fine. I allowed it to charge for 30 minutes and the voltage difference was never more than 0.2V. So I removed the old batteries and checked resistance from the controller through the breaker to the battery terminal and found 0.51ohms. Half an ohm sounds fine. All connections were tight and free of any visible corrosion. I put 3 new house batteries in....
My current connection is both the load and negative is connected to the center battery (as is the charger). I believe John is saying that the optimum set up is to have the load and negative on far opposite ends of the bank. (See attached drawing). I can/will rewire it that way if optimum, but having it wired with load connected on the middle of the 3 batteries should not cause a 2+V difference in what the charge controller sees. At this point, I could not recreate the problem with the controller, but I do not trust it while not on board and have emptied the refrigerator and turned everything off... not ideal. Sorry I can't post to the forum on my boat via my android phone b/c of redirect issues at login and couldn't get real-time advice from you guys.

Actually .51 ohms is a lot in this situation. Power= Amps squared times resistance. in this case if you are trying to push 25 amps through that wire you will dissipate about 318 watts as heat instead of power going into your batteries. How much solar do you have to spare? You have resistance in that wire equivalent to about 1250 feet of #6 wire. You have a bad wire. You should have only .4 ohms per 1000 ft of #6 wire and you have 25% more than that in 3 feet. It's possible that the problem is in the breaker, but that is your problem. At low currents you might not see much of a voltage drop, but you will if your try to push 25 amps through it.

[zstine]

Originally Posted by john61ct

Zach, was Justin able to help?

I did hear from Justin before I went to the boat last weekend, but not after the results. I think the 0.2V is due to the 0.5 ohms in the line. I will rewire the batteries this weekend to put the negative and positive leads on opposite ends of the bank, vice them being on the middle battery. When I do that, I will poke around a bit more with the multimeter.

Originally Posted by Captain Bill

Actually .51 ohms is a lot in this situation. Power= Amps squared times resistance. in this case if you are trying to push 25 amps through that wire you will dissipate about 318 watts as heat instead of power going into your batteries. . .

I think you have over simplified this b/c that is not what I'm seeing. The monitor is showing basically the same charge as the charge controller. I think ohms law applies to a complete circuit. I don't think you can just consider 1 resistor out of a complicated circuit with multiple power supplies and loads. what you are saying is the same as stating the voltage drop (V=I x R) would be 12.5V in that line at 25Amp charge & 0.5ohms. As I stated before, the monitor to controller delta is only 0.2V. However, I will check the breaker, though I was not able to find a resistance spec on the Tocas 50Amp breaker to see what is expected... perhaps that is too high...?

[zstine]

After reading pbase article (Keeping Your Battery Monitor More Accurate Photo Gallery by Compass Marine How To at pbase.com ) I’m left with some questions specific to how I use my batteries and why they may have failed so early. pbase speaks to people discharging to 50% SOC as a cycle and b/c error in their monitors, they are really discharging too far. I pretty much never discharge anywhere near that far. Typically on a weekend I will discharge to 85-90% SOC Friday night, fully charge via solar, then discharge 85-90% SOC Saturday night, recharge and the boat sits for the week with no load on the battery, but charger still on every day. I have an oversized solar array and battery bank in prep for live-aboard when I will run a watermaker, refrigeration in tropics, etc. But I only got 4 years out of my batteries and that’s less than 200 cycles, most of which were cycles less than 80% SOC based on full AH rating.

Q1) Is it better to discharge to 75-80% SOC and then recharge on Sunday, vice ‘short cycling’ with 2 recharges in 1 weekend? In other words, is it better for battery life to load the battery for a few days and then recharge, cycling fewer times, or is it best to recharge every day and have many more small cycles (assume never discharge below 50% SOC)?


Q2) My boat sits without load all week, but the solar charger turns on at sun up and goes into a short absorption, then float charge all day every day holding 14.4V. Is this charging taking life out of my batteries compared to turning off the charger when I leave the boat or is it good to have them topped at 14.4V everyday?

[john61ct]

Originally Posted by zstine

After reading pbase article
…
pbase speaks

Note that is Maine Sail, pbase is just a temporary free web host, and all that content is being moved to his new site.

Originally Posted by zstine

people discharging to 50% SOC as a cycle and b/c error in their monitors, they are really discharging too far. I pretty much never discharge anywhere near that far. Typically on a weekend I will discharge to 85-90% SOC Friday night, fully charge via solar, then discharge 85-90% SOC Saturday night, recharge and the boat sits for the week with no load on the battery, but charger still on every day. I have an oversized solar array and battery bank in prep for live-aboard when I will run a watermaker, refrigeration in tropics, etc. But I only got 4 years out of my batteries and that’s less than 200 cycles, most of which were cycles less than 80% SOC based on full AH rating.

Assuming those SoC readings were accurate, the bank was quality true deep cycling batts, and you were otherwise taking good care of them, then yes, you should have got a lot more life.

The likely culprit IMO was having the bank miswired as discussed above.

Originally Posted by zstine

Q1) Is it better to discharge to 75-80% SOC and then recharge on Sunday, vice ‘short cycling’ with 2 recharges in 1 weekend? In other words, is it better for battery life to load the battery for a few days and then recharge, cycling fewer times, or is it best to recharge every day and have many more small cycles (assume never discharge below 50% SOC)?

Depends. Lots longer life (more cycles) from averaging 20% DoD than 50%. Between 10% and 20% not so much.

Originally Posted by zstine

Q2) My boat sits without load all week, but the solar charger turns on at sun up and goes into a short absorption, then float charge all day every day holding 14.4V. Is this charging taking life out of my batteries compared to turning off the charger when I leave the boat or is it good to have them topped at 14.4V everyday?

Best to just hold at float if no load.

A good controller will let you set Absorb = Float voltage for while you're not cycling.

With the usage pattern you describe, you may get by with no solar at all, just recharge on shore power after the weekend?

[Maine Sail]

Originally Posted by zstine

Q1) Is it better to discharge to 75-80% SOC and then recharge on Sunday, vice ‘short cycling’ with 2 recharges in 1 weekend? In other words, is it better for battery life to load the battery for a few days and then recharge, cycling fewer times, or is it best to recharge every day and have many more small cycles (assume never discharge below 50% SOC)?

Shallow cycles mean longer life but shallow cycling takes almost just as long to charge to 100% as deeper cycling. In many cases there are simply no enough solar hours to get to 100% SOC every day. There is no problem with going below 50% DOD, on occasion, but it is best to follow a deeper discharge with a 100% SOC re-charge asap.

Originally Posted by zstine

Q2) My boat sits without load all week, but the solar charger turns on at sun up and goes into a short absorption, then float charge all day every day holding 14.4V. Is this charging taking life out of my batteries compared to turning off the charger when I leave the boat or is it good to have them topped at 14.4V everyday?

14.4V is not a float voltage and will damage batteries if they are getting this every day. A float voltage would be between 13.2V and 13.8V and without knowing what batteries you have it is impossible to help you set the system up correctly..

Battery brand & model #??

[zstine]

Originally Posted by Maine Sail

Shallow cycles mean longer life but shallow cycling takes almost just as long to charge to 100% as deeper cycling. In many cases there are simply no enough solar hours to get to 100% SOC every day. There is no problem with going below 50% DOD, on occasion, but it is best to follow a deeper discharge with a 100% SOC re-charge asap.

arrg... I'm still not clear on this. you say "shallow cycles mean longer life", then "it is best to follow a deeper discharge with a 100% SOC re-charge". So in my case, I pull 50-60AHr out each night on a 465Ah rated bank. My solar charge puts out 25amps to 30Amps max and is usually in 'float' by 11am when I charge every day. If I turn the charger off, pull ~110Ah and then turn it on Sunday, I may not get all the way to 100% SOC that day, but certainly I get back to 100% by Monday. So what is better, 400 cycles to 88% SOC or 200 cycles to 75% SOC?

Originally Posted by Maine Sail

14.4V is not a float voltage and will damage batteries if they are getting this every day. A float voltage would be between 13.2V and 13.8V and without knowing what batteries you have it is impossible to help you set the system up correctly..

Battery brand & model #??

You are correct. My mistake. 14.4V is the constant absorption voltage and the controller is at 13.8V for float. The batteries are made by East Penn, qty 3 of Duracell Ultra 12V golf Cart batteries rated at 155Ahr each. So when I leave the boat with no load for a week or 2, is it best to turn the solar controller off or leave it on, which puts a 14.4V charge on for a short time, then holds 13.8V all day?

[foggysail]

Originally Posted by john61ct

The issue is not voltage drops. It is that in #1, very common but doing it wrong, the electron flow is "exercising" some units more so than others, so they get imbalanced, wear out very unevenly and the whole bank dies prematurely, at the rate of the weakest link.

Of course it is an issue of voltage drop! BAtteries on a bus are held to the same voltage when no current is flowing on the bus....regardless of the bus wire size. For charging and assuming all the batteries have the same effective internal resistance and state of charge, the current would be distributed equally if the bus had zero resistance. This remains true as long as the voltage seen by each battery is the same but that voltage will not be the same because the voltage will diminish as current progresses down teh bus, Vdrop= I X Rbus.

The Vdrop is easily controlled by reducing Rbus, i.e LARGE BUS WIRE.

Hey, this is basic circuit stuff taught in Elementary Circuit Theory 1.

[john61ct]

The issue here is the incorrect wiring **pattern within the bank**, and would not be improved by larger gauge wires.

And it results in permanent damage over time, like combining old worn out batts together with new ones to try to create a single bank.

[foggysail]

Originally Posted by zstine

The batteries are made by East Penn, qty 3 of Duracell Ultra 12V golf Cart batteries rated at 155Ahr each. So when I leave the boat with no load for a week or 2, is it best to turn the solar controller off or leave it on, which puts a 14.4V charge on for a short time, then holds 13.8V all day?

Curious, have you monitored your battery fluids? I have East Penn's Dura Cells 6v golf carts rated at 215AH. I set my float at 13.4 to minimize gassing. I did check with East Penn for charge settings, have their recommendations at my boat but I think they recommended 13.6 for mine. I would rather minimize the number of times they require water and set the floats to lower voltage.

[foggysail]

Originally Posted by john61ct

The issue here is the incorrect wiring **pattern within the bank**, and would not be improved by larger gauge wires.

And it results in permanent damage over time, like combining old worn out batts together with new ones to try to create a single bank.

Hey, I am not going to argue with you. Do as you wish but rest assured, bus wire size can balance the voltage seen by the batteries under charge. Consider getting an an elementary circuit theory book for your spare time reading

[john61ct]

I'm not saying wire size isn't important in general.

I'm saying the wrong-pattern issue - again, nothing to do with voltages; the **amps** flowing through the bank unequally is the issue here - is not helped by bigger wires.

You can see for yourself, do a full charge wired like OP used to (I hope, fixed by now?) long Absorb, down to .005C, then equalize.

The batts near the termination end bubbling away, the ones "ignored" sit there dead quiet.

Leave wired like that for a year and do a 20-hour cap test, wildly different.

None of the above having anything to do with voltage diffs, not that kind of imbalance issue.

[foggysail]

Originally Posted by john61ct

I'm not saying wire size isn't important in general.

I'm saying the wrong-pattern issue - again, nothing to do with voltages; the **amps** flowing through the bank unequally is the issue here - is not helped by bigger wires.

You can see for yourself, do a full charge wired like OP used to (I hope, fixed by now?) long Absorb, down to .005C, then equalize.

The batts near the termination end bubbling away, the ones "ignored" sit there dead quiet.

Leave wired like that for a year and do a 20-hour cap test, wildly different.

None of the above having anything to do with voltage diffs, not that kind of imbalance issue.

I give up! Still suggest an elementary circuit theory book for casual reading. You cannot ******** physics

[CatNewBee]

Batteries eventually die and in a bigger bank they'll kiil their neighbors too.

[john61ct]

Are you trying to say "only use single batt bnks?"

Obviously most follow the advice to have all bank batts match each other in age.

And banks should be replaced when AH capacity has walked down by 25-30%.

This is long before there's much risk of the kind of catastrophic failure you're talking about.

A properly managed and monitored bank should very rarely give any surprises.