T105s-what's bulk vs absorbtion?

[sailcrazy]

following. We run 6-T105s for a house bank, and augment with 4-80 watt panels and a Victron solar controller, a windgen+controller, and a 80-amp alternator when we run the engine. We also have a ProMariner ProMatic 50-3 batt charger... that we turn on every time we run the genset(daily, as we cook with electricity and our refer system is 230v AC). The batts seem to do OK, but trying to decide what to set the controllers at has been a real challenge, since nothing lines up with the Trojan published numbers.

[Flatswing]

Can't speak to the other charge sources, but the ProMariner, If it is the ProNautic series (not Pro Matic) has customizable settings you can put in whatever parameters you choose

[Jon Hacking]

One of the "problems" with newer battery types is that they can be killed very quickly by overcharging. We destroyed a $3,000 bank of Sonnenschein Gels in about an hour, due to thermal runaway.

So make very sure that your MorningStar has temperature compensation for your battery, as the Absorption voltage (especially) is quite temperature dependent. My Gels were "overcharged" at only 13.8v, a full volt below where you're planning to take yours.

Having said that, as a general rule, the older (flooded) battery types can take more abuse (at a cost of not lasting for as many cycles). Boiling a flooded battery for a few minutes now & then just stirs up the electrolyte (acid) which is good for it. But don't take Gels, AGMs, or LiFePO4 to that point.

As has been pointed out, the best way to know when the battery is full & the charger should switch to Float is when the current required to hold the battery at the Absorption voltage drops down to 1% of the Ah capacity of the battery. So, for your 450Ah bank, your charger should switch to Float when only 4-5A is going into your batteries.

For this to happen, your charger needs to monitor that current, usually by tapping into the shunt you have for your Amp-hour meter. If you don't have an Ah meter, you should really consider it. It's essentially a fuel-gauge for your battery, one of the best ways to tell how much charge is really in your battery at any time.

Unfortunately, the vast majority of chargers do NOT look at the current going into the battery. Instead, they simply hold the Absorption phase for a certain length of time. This is patently silly, as the charger has no idea if the bank is severely discharged, or if it's almost full!

With LiFePO4, this isn't as big a deal. But with lead/acid batteries, your Bulk stage will probably be over pretty quickly, & most of your charging will happen in the Absorption phase. A "smart" charger will look at the current into the battery to figure out when the battery is full. Time-based chargers are not smart. Unfortunately, I suspect your MorningStar falls into the 2nd category, something you might want to think about if/when it comes time to look for another MPPT.

[Stu Jackson]

Originally Posted by jpendoley

Flatswing-thanks for that graphic-it was helpful. Stu-I've read Calder and Casey and some of Mainsails stuff-that link you shared was fantastic. I think some of the confusion is casued by the manufacturers themselves and the sometimes confusing marketing language they use. That, and some of us are just electrically challenged
All the advice is deeply appreciated.
Jim

Jim,


I thought of that particular MS article because of two things:


1. Exactly what you mentioned about confusion. [His point to begin with, I believe.]


2. Which was in addition to a very good, simple, plain language description of how batteries get charged. [It's really simple, but some people make it too complicated.]


Thx

[jpendoley]

Jon,
Excellent point about the "smart chargers". My morningstar has a baterry sense wire that reads voltage and a temperature sense wire, but thats not the same as an amp counter. It seems to set charging periods based on time intervals independent of current acceptance. At least thats what I believe it does-still studying that. What they have for a work around in the custom settings, is to allow extension of the absorption or float stages if the charging drops out of the said stage before the preset time is reached (in this case 2 hours), So if I was in absorption, the reefer came on and it dropped to bulk, on the next cycle it would extend the next absorbtion cycle by 30 minutes. I guess after some number of cycles it would result in a pretty accurate custom profile. At least thats how this english major understands it.

And Stu, speaking of English majors, liberal arts types like me are electrically challenged because we don't think like engineers. It behooves us to remember we can still burn our boats down though just like everyone else Thats why I ask endless questions. If it was not for this forum and the willingness of others to chime in my boat would be a distant glow on the horizon. Thanks for all the lessons.
Jim