float voltage

Don

Whatever controller you use, make sure the TC agrees with what the batteries expect. The Morningstar and Lifeline don't agree in extreme temperatures and there isn't a way to customize the TC as far as I can tell.

Phil, at -40 I will need temperature compensation.

pianotuna wrote:
However the RV will be in storage from november 20 to march 10 and the Solar will be floating the bank.

Don, what BFL13 says above makes a lot of sense.

It sounds like what your AGMs REALLY NEED is a two-stage-output charger and a two-stage-output solar controller (both of those being temperature compensated). The two stages would be 14.XX volt temperature compensated range for initial fast(er) charging and a lower 13.6 volt temperature compensated range for combination long term taper-charging and floating.

I don't know much about available solar controllers, but good luck finding a temperature compensation two-stage charger except for this one - which you and BFL13 are aware of:

http://www.bestconverter.com/4455TC-ParaMode-with-TempAssure_p_164.html#.Vcv2t3GCb21

Here's it's voltage output curves showing it's two output stages .... with a wide value-range for each stage as each stage is adjusted for temperatures surrounding the battery as reported by it's probe:

https://bestconverter.3dcartstores.com/assets/images/Parallax/4400/4455%20Voltage%20Curves.pdf

Get a cheap controller that has adjustable voltage such as the Solar30 (about $35) and only hook it to one panel or how many it can handle. Since it is just for storage amps, you don't need the full array and big regular-use controller.

Measure the voltage at the battery posts to confirm the controller's setting in case of an index error on the controller's setting. Bit of trial and error time to get it right (1/2 hour?) Most of those have their temp comp on the controller itself, so mount it with the batteries for same ambient.

If you only have 24v panels, the Solar30 can do that if the batts are 24v. You could wire them for 24v while you are away too since you won't be needing any 12v then.

Hi Phil,

Possible charging sources are a Magnum inverter/charger than can do up to 125 amps, a pd 40 amp that can do 14.4, 13.6, and 13.2 volts, plus the Blue Sky.

However the RV will be in storage from november 20 to march 10 and the Solar will be floating the bank.

Don,

I guess you want to use solar, only, for floating them?

Do you still have a good old 13.6 volt converter? If so, use it for floating your AGMs as much as you can when not able to use solar.

As you know, I use a 13.6 volt converter for months on end to both charge and float our RV's AGM battery bank - but our AGMs have a 13.6 - 13.8 volt float voltage range specified by their manufacturer.

I'd leave it there until the total bank hour amps came down to 1/2% of total bank hour current flow, or just less, at 13.5-13.6V, at least for my battery. Once there, I'd rest it 24 hours and see what the OCV is, and then I'd hit it with 14.0V until the percentage is the same. Rest 24 hours and then I'd hit it with 14.4V on the third go round to 1/2% of total amp hour capacity, and call it good.

To fine tune your float storage system, wait a month or two then apply ABSORBSION voltage, and see how close to fully charged status the ammeter declares. (Needless to say) For example if three percent of total bank amp hour current flows for 20-minutes, how would you handle it?

You folks are good enough to puzzle this out...

Yes, but some disassembling will be required.

2oldman wrote:
Can't adjust your voltages?

Can't adjust your voltages?