Boost Voltage charging time?

[fabieville]

How long should a charge controller remain at the Boost Voltage before switching to float charge mode?

I have a charge controller which is set at 2hrs default and then afterwards it goes into float mode.

I have (2) epever 40ah mppt charge controllers which are charging 2 different battery banks which the default time is set to 2hrs for both of them to remain at the boost voltage mode. I have (2) SLA deep cycle battery bank. One is 12v at 380ah 14.4v boost and the other is 24v at 380ah 28.8v boost.

Should each controller remain at the 2hrs default for the boost voltage or how much time would be the recommended time to remained at the boost voltage before going into float mode?

[Umpa]

I have just bought an Epever 40amp CC, so I would like to know the answer too. Anyone with one of these have the answer or would like to take a guess, or report on your experience ??

[Sunking]

As long as you can make it. It is impossible for a Solar System to ever fully charge a battery as there is not enough Sun Hours in a day.

[PNjunction]

If this use is cyclic with frequent daily use, with irregular solar exposure, your best bet is to just keep your batts at CV/absorb/boost until the sun sets, rather than go into float too early.

In other words, most controllers with the 2 hour absorb/boost timeout, are doing so out of an abunduance of caution, and not knowing whether the user is doing cyclic, or just weekend-warrior duty. So they assume some sort of solar doing a backup service, and not daily cyclic and the batts never get a decent charge and walk themselves down in capacity.

Ideally, with an agm, one stops the CV/boost/absorb when there is no *change* in CV current for about an hour, and I've only seen a few higher priced controllers that will do this. This is the real timeout period that takes into account the real-world aging issue.

So - when doing solar with agm's, and if you get serious, you gotta' keep an eye on things. It's hard to get it truly right - so we just make the best compensation tricks we can, knowing that it is most likely we'll murder an agm sooner than later.

And, know that even if you DO finish a boost stage properly, with agm's it takes ANOTHER 8 to 16 hours in float to truly achieve a full charge for that last 1 percent. If you don't you'll walk it down in capacity - slowly enough that it creeps up on you when you think all is good.

If you can afford the downtime once a week, or month, or whatever, ensure your agm's have gotten a full CV/boost/absorb stage finished, and then let it sit all day on float. Or find some other mechanism like AC charging at float or whatever once in awhile to get that last 1 percent charged.

[Mike90250]

The other way to complete a full charge cycle, is early morning, 5am, start your genset and get thru BULK with the generator, and then let the solar handle absorb and float all day. In BULK, you are using your genset most efficiently .