Originally Posted by btrayfors
I take slight exception to that rule
, RC. In my experience, recommended charging/float voltages are very conservative and not necessarily to be followed exactly.
For example, I have floated my T-105 Trojans, and now my CR235 Crowns, at 13.8VDC. That works very well. I also charge them at 14.8 - 15.0VDC in the absorption phase, and from the float level kick them up to the absorption level periodically -- in my case, every other day for a half-hour.
I have found this to be beneficial to the batteries.
In my discussions with Concorde engineers, I was told that higher float voltages for their AGMs are a good thing.
What I can tell you is that the higher float voltages work well, and do not result in extra bubbling or water
loss. And, hopefully, they result in less sulfating because batteries will continue to sulfate if kept at the lower float voltages.
You and I are not really in disagreement. The problem however is quite complex. Three days ago I had lunch with a well know marine
author, a battery engineer/inventor, Bruce Schwab & a marine electronics
blogger. The subject of problems with charging & the failings of the charger manufacturers to work in concert with the battery makers, certainly came up.
One issue is that almost none of the charge sources out there will provide a long enough absorption cycle to bring the batteries to 100% SOC before dropping to float. We are trying to finish charging in the marine industry by using float and this is simply a poor practice.
Even programmable models often lack the ability to extend or customize the absorption time or when or how to transition to float. Good ones do allow this, medium ones allow custom voltages only and $hitty ones have dip switches
& egg timers
offering a; you get what you get
If the batteries are charged correctly to begin with, then a higher float, than what the manufacturer recommends, is not entirely necessary and can actually be detrimental to some batteries. The engineer
I had lunch with on Tuesday is adamant
that 13.2V be the absolute max float and he would ideally prefer no float at all
. He does however recognize that in off-grid, marine & RV applications parasitic loads result in the need to float.
As it sits I just got off the phone
(& text) with a consult customer who has destroyed a set of Trojan batteries way sooner than he should have. Last week he had a thermal runaway event on one battery and another battery, Batt #1, with an SG imbalance he thought he could save by EQ, just went that way too about two hours ago.
And this was after it had been isolated and cooled down a bit. Murdered far too soon due to poor charging....
When I finally dug into his system with him I found out that he has 500W of solar
with an absorption of 14.1V with a maximum absorption time of two hours regardless of SOC.......
Yep, murder for Trojan batteries and his particular MPPT controllers are not programmable.
We certainly have some leeway with flooded batteries & foat but less so with sealed GEL or AGM batteries and this varies by battery manufacturer.
But it all comes down to the question of; why bother paying good money
for a dip-switch/egg timer product when you can buy better products that allow customization so your batteries can actually charge they way they should??