Bulk-Absorb-Float what are we missing?

Re: Bulk-Absorb-Float what are we missing?

Thanks, that leads to a number of options. For example, the Morningstar TriStar controllers.

I wonder how much difference in battery life there is between exactly implementing the Trojan 3 stage recommendation and the approximations of the 2 stage profile that are typically possible?

Re: Bulk-Absorb-Float what are we missing?

jonr wrote: »

Are there charge controllers where the desired (you might get less) output voltage is easily set by another micro-controller? An Arduino with a voltage and a current sensor (Allegro ACS758 200A Hall Current Sensor?) could implement a proper/safe charge profile and provide the additional benefit of tracking DOD and turning off my inverter when it gets too low. Or maybe it's easier just to do the whole thing.

With (evidently) only one company getting it "right", I have to say that I am disappointed in the state of charge controller engineering.

jonr,

Regarding charging batteries from RE power sources, there seems to be a world of opinion, and ideas, but there seems to be few cookbooks of exactly what one should do, without access to Grid power.

One person's opinion of what or who has done it "right", is just that -- one person's opinion.
AND, in a short time, that one person will have a different opinion.

There is no one right answer. It "all depends". Battery manufacturers are generally not giving advice on just how to charge batteries from PV power sources.

We all do our best. As mike mentioned, Constant Current Bulk is normally NOT available from PV sources of any reasonable size.

The neat thing, is that nothing needs to be perfect, and perfection is a matter of opinion. We all do our best to do our best. Most of us who try to pay attention to our batteries all seem to have more questions than answers -- ala vtmaps and stephe
ndv.

Flooded batteries are very forgiving, particularly for those users that are paying attention to them.

The MidNite crew seems to be listening to the RE Community, and making innovative products that are open to users who want to extend functions. They have my vote.

The MN WhizBang Jr is a battery current monitoring device that is tied to the Classic and KID CCs. This U$ 45.00 device is a great addition to a MN CC, just keeps getting more functions added over a short period of time. The WBjr is NOW being bundled with every Classic CC. It is NOT being bundled with Classic Lite CCs. There may still be some Classics in distribution, that do not have this WBjr bundled ... for any new orders for Classics, check at the time of purchase for exactly what you are buying ... as I read it.

There is a lot of NOISE in the area of what is the correct way to charge batteries, particularly from PV-based systems, IMO. Most of us seem to be experimenting, a bit. FWIW Vic

Re: Bulk-Absorb-Float what are we missing?

I see that Hawker (CYCLON/Genesis) writes:

"Our tests have shown that for the IUI profile to be effective, the inrush current must not be less than .4C10".

Rolls recommends .25C20 for an AGM IUI profile. Trojan (lead acid) IUI was .1C20.

This leads me to ask if there is any merit to some type of rotation system where every day, one battery is removed from service and given a charge exactly matching the recommended profile - while the others get what ever is left over. That should make finding a charger that implements the profile easy. It even makes longer time periods possible (by drawing from the other batteries).

Re: Bulk-Absorb-Float what are we missing?

jonr wrote: »

I see that Hawker (CYCLON/Genesis) writes:
"Our tests have shown that for the IUI profile to be effective, the inrush current must not be less than .4C10".

Careful - I've been down that road following Enersys / Hawker / Cyclon docs from 1998 onwards. Note that we are speaking about the pure-lead, or TPPL design here. Genesis currently has a general purpose line that is not tppl, and is in fact more like a standard Yuasa agm.

Still, the IUI profile was prominent in 1998 for the EV market with the Genesis / Odyssey line, and the power-tool market for the Cyclons. The example they give (circa 1998 ) was for EV's, which cycled at 60-100% DOD, and needed to be recharged within 6-8 hours instead of 16. The goal was to reduce the float time, and the last "I" helped accomplish this. Thanks a pantload Mr. Peukert! However, the 0.4C minimum was needed to also overcome the heavy sulfation at those deep DOD's.

As the years progressed, the IUI profile was less prominent, and when mentioned it was to call an engineer for additional support. The latest applications manuals may or may not even mention IUI any more.

The reason here is that most of us have adopted the 50% DOD as the cyclic cutoff point, whereas in the past, 80% DOD or more was a typical EV selling point.

So, with 50% DOD, you may be able to reduce that requirement to 0.3C, and not need the last elevated voltage "I" in the IUI profile. Enersys engineers should be consulted on this if this is a critical app for you.

However, that leads us to more float time if you want to play it right. Unfortunately, most solar CC's that are based on time may switch out of absorb to float too early, or you just have unreliable solar-insolation during the absorb period, and lack of sunlight shuts it down before it even gets a chance to go to float.

This is the LONG (sorry about that) way of me saying that for TPPL batteries in a variable solar application, I think the best "recipe" if you will, is to just set your absorb and float voltages to the same value. The extended period of absorb before darkness hits help make up for the lack of 8 hours or so of float desired by these types of batteries. Of course if you actually do finish absorb and hit float 30 minutes into your normal solar-insolation period, then perhaps one doesn't want to have an extended absorb.

I have no experience with Rolls or Trojan on their implementation of IUI in a solar environment.

Vic has it right - one needs to go with what they are comfortable with. I go the KISS route with tppl and extending absorb voltage time. Treating my system like an EV from 1998 made my head hurt.

Re: Bulk-Absorb-Float what are we missing?

Optimal for the Enersys line says to NEVER go above 15v, which the IUI of old would do. But that's for 60-100% DOD, which nobody should be running these days in a cyclic application.

That .3C minimum is easily doable for the Cyclons, but yes, it is kind of a pain for large banks of Odysseys. It would be interesting to get some real feedback from an Enersys engineer about what the real requirements are for a 50% DOD worst case, cyclic solar application, and not the usual motive power / standby situation.

They harp on 16+ hours of float (no less than 13.6v!), and one alternative in the Genesis application manual suggests just staying in absorb for 8 hours. With solar I still don't have that much time, so I bite the bullet and just give it as much as I can by keeping my absorb and float voltage the same.

I do this with my Optimas (in the tppl family) too.

Re: Bulk-Absorb-Float what are we missing?

Vic wrote: »

jonr,

Regarding charging batteries from RE power sources...

very good post, Vic, as always ...;-)

I promptly let what you say, and I agree with you.
the batteries issue, in RE applications, is something new that we are characterizing and defining in this moment. because although the technology of the batteries is really old, no clutch the use we make of them is still so new.

the truth is that there are so many schools with this. since some are for the most aggressive side, and some one are also the most conservative practices, we're all making sure that the batteries endure more than conservative believe, and also enduring less than the most aggressive think ... ;-)

we all hope that in the future, new technologies are affordable soon, but meanwhile, with the subject of the batteries will be no free of controversy.