Charge controller recommendation

[rvpopeye]

IIRC many batt mfgs use 77* as the default on spec sheets.
But it's battery temp that matters , not the controller...? Skuh kuh kuh kuh kuh

Might not apply to all battery chemistries either.

A batt temp sensor probe is included on some controllers and optional accessory on others or not at all on the rest..

[Roadtripp]

I think a internal temperature sensor is standard even on cheaper units so if the charge controller is in the same temperature environment as the batteries it should adjust the voltage fairly accurately (higher voltage when cold). If one or the other is in a conditioned space it could be a recipe for disaster as far as battery life is concerned. That scenario calls for a temperature sensor placed on the batteries. 
 I’ll stick with Made in USA programmable controllers on my a big system or expensive battery. It’s a energy system and I am my own power company and I take that seriously. On a small system why not try the cheaper units

[sternwake]

In 2007 I bought a Bluesky SB2512i MPPT charge controller.....25 amps max and limited to 12v nominal panels.  The SB2512ix  model was about 35$ more expensive at that time, and in addition to a few extra features I would never use, it had the option of adding a battery temperature sensor.

While I am usually in a fairly mild climate and temperature compensation is not as important compared to one with more wild temperature swings, that 35$ I 'saved', back in 2007,  is one of my biggest purchasing regrets.

I can say my SB2512i does not have any ambient temperature sensing, as absorption voltage and float voltages never change despite ambient temperatures well outside of 77F.

My other charge controller, The old discontunued version of the 20$ model  on special closeout Renogy charge controller I use in my workshop, does have a battery temp sensor, I can easily see it adjust  absorption and float voltage with battery temperature.  I just taped the sensor to the top of the battery case, but it is likely being eaten away by the acid that this battery is now continuously spitting up whever it is being charged, even though the battery is on a slight angle  with the leaning slab on which it resides, and the sensor uphill of the caps.

My opinion is that the ability to change a solar charge controller's  absorption voltage, and its duration are the single biggest factor in achiving good lead acid battery life, and of those two, the ABSvoltage and its duration, the duration is more important, especially as the battery ages and it takes longer and longer to actually achieve full charge once the solar has gotten it to absorption voltage.

Premature float is the biggest Lead acid battery murderer out there, so the charge controller which can be forced to hold  and aged battery at ABSV for 4 hours, rather than be stuck to two, will pay for itself with additional battery life and less frequent battery replacements.

One person's 'good enough' is another's woefully inadequate.  I just urge readers to understand that 'good enough' when the battery is new and healthier IS woefully inadequate once a few hundred cycles have accumulated, and the charge controller which does not allow for lengthening the duration of the absorption voltage stage will have battery performance jump off the proverbial cliff, when it could instead  walk slowly down the  nearby switchback trail enjoying the view.....deteriorate at a much slower rate, had longer absorption durations been employed.

it is a shame when a 95% charged battery is dropped to float voltage early afternoon, as less than 1/3 the amps wll flow at 13.2v compared to 14.4v+, and even 6 more hours of float will likely  not do what ~45 minutes more of 14.4v could have. 

 This is the main  compromise of the  cheaper un adjustable Solar  controllers, and really any automatic charging source....Premature dropping to float voltage before the regularly deeply cycled  lead acid battery is indeed fully charged.

The deeper the depth of discharge the more important it is to reach true full charge regularly, and the more aged the battery, the longer and longer it takes to get from 80% charged to 100%.  50 to 80% takes a bit longer too but not nearly to the same degreee as 80 to 100.

[Ddarnell]

That is so true and why i say if youre new just get $50 walmart starting batteries because all you can expect is 6-12 months either way.

[sternwake]

Well any newbies reading on the topic should be less likely to destroy batteries through ignorance. But buying the cheapest battery and using the warranty once is a valid strategy for some too, as long as getting a warranty replacement is not super inconvenient at that time.

I used to dread that part when i was new to living on 12 volts dc and was deep in Mexico more than once when the battery lost most of its ability to retain capacity. No Mexican Wal-Mart's within several hundred miles and I had to be stingy with a single incandescent light no steroe or computer for weeks until I crossed the border and could warranty the battery.

That sucked,and was part of the motivation to learn all I could about the proper care and feeding of lead acid batteries.

[tx2sturgis]

Just clarifying a previous post about the fact that I am not using temperature compensation on this new Renogy Controller:

I have it set for lithium, and it is charging a BattleBorn 100ah lifepo4 battery (using a 100 watt panel) and I also use a shore powered lithium charger. It says on the BattleBorn website and several other websites, that temperature compensation should NOT be used, or, if possible, it should be disabled.

Since the Renogy controller is set for LI, that may be why the readout seems 'stuck' at 76 degrees. Kinda makes sense, actually. At any rate, the controller and the battery are in the same cabinet.

I agree with Sternwake that lead-acid batteries SHOULD be charged using a temperature sensing and compensating charge source, and two of my other solar chargers for lead-acid batteries are operating with temperature compensation and sensors.

[justjim]

I want to add that some of the internal temperature sensors in the lessor charge controllers are not there for the battery but rather the controller itself. The Eco-worthy 20 amp MPPT controller has a internal sensor but it protects the controller from overheating, not adjust the voltage to the battery for different temperatures.

[Wayne49]

Try taping the sensor to the side of the battery instead of on the top.

The sensor for a Trimetric has hole to attach to the negative pole. That would give a reading from the plates.