When Amps taper to 0.5 @14.7v, on my almost 13 month old 100Ah Northstar group31 TPPL AGM, with about 100 deep cycles on it, I lower voltage to 13.6v, the recommended float [email protected]
77f battery temperature..
0.3 amps still flow at this voltage at this stage on the adjustable voltage power supply. Many hours later my Ammeter reveals amps have tapered to 0.0x @ 13.6v, but it cannot read amperage below 0.05 amps.
if at this point I crank voltage back upto 14.7v, amps jump to about 1.7 then quickly taper down below 0.5, then down further to 0.0x.
So yes the Float 13.6v voltage allowed, after the recommended 0.5% of Ah capacity at absorption voltage is attained, additional charging does still occur.
When older, the amps do not taper as low at float or absorption voltages. They seem to hit a bottom and then start rising at absorption voltage and simply quit tapering at float voltages, post absorption stage.
Trickle charge means a lot of different things to different people. I consider it to be a charger limited to 2 amps output or less regardless of the voltage limitations, if any, imposed by the charger. Many larger older batteries, 2 amps will not be able to achieve 14.5v plus, no matter how long the charger is left applied and some so clled 'trickle' chargers have 2 amps available shoould the voltage delta be large enough, but will max out at 13.8v.
new and OLD batteries amperage acceptance, at different voltages differ wildly in my experience, with the older batteries requiring much longer at preferably slightly higher voltages to reach true full charge, and at lesser voltages simply cannot ever have their specific gravity max out, or amperage taper to prescribed levels which would indicate full charge.
Cycle an Odyssey/Northstar to 50% state of charge, and feed it only 2 amps for the likely 24hours+ needed to even approach full charge, assuming the 'trickle' charger is even seeking 14.7v, and it is not going to be a happy AGM, or at least not as happy as if it had been fed Odyssey's minimum 40% charge rate, in deep cycle duty. the high amperage charge rate forces electrolyte migration theour the glass matting and deeper into the dense, but thin plates, at least on TPPL agms. A true deep cycle AGM like lifeline still recommends no less than 20 amps per 100Ah of capacity in deep cycle usage, and they say more is better and that one could theoretically feed a 100Ah battery 500 amps without issue, as long as voltage is limited to 14.4v.
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But few here seem to deep cycle their batteries, intentionally anyway, and more here prove that knowing the amperage flowing at any given voltage is even less important to them compared to colorful lights.
A battery in deep cycle usage will age differently than one cycled shallowly and living slightly undercharged 100% of the time as well, and exactly how they differ in their aging would require lots of experimentation and data gathering and observances of trends and tendencies as the batteries age/accumulate cycles/deliver KWH with the inevitable result that the battery becomes useless, the variable being how soon it becomes useless.
Odyssey and Northstar are top $$ TPPL AGM batteries, and highly capable in both the CCA and in deep cycle duty, when recharged properly, but some seem to think they are a super battery that immune to chronic undercharging or that any old charger will do 'just fine'.
Dismiss the recommended 40% charge rate in deep cycle duty, at your own peril, and don't blame the battery for not living upto expectations. The claimed cycle life and life expectancies, assume LAB quality recharges, meaning a true and full charge promptly applied after the prescribed level of dischare is applied. Little correlation to a lab cycle and a cycle in the real world, whether deep cycle or starter only duty.
The high amp recharge from a well depleted state is how I return my Northstar to expected performance, after many cycles not reaching true full charge, OR reaching true full charge, but at a slower initial amperage rate, or when it is cycled deeply after a week+ of sitting at the correct float voltage.
In these three scenarios, a discharge to 50% and a high amp recharge returns expected performance whether judged by voltage maintained during engine cranking, or on lower loads applied for longer, like refrigeration and powering lights and fans and a laptop a dremel and soldering iron.
I'll deep cycle the battery , even when i don't need to, because a week at float seems to make the battery lazy, and even if treated absolutely perfectly, it will not last forever, so might as well cycle it even when it is not required, as long as it can receive the recharge parameters which make it happy, meaning high amperage from a well depleted state until it reaches 14.7v, and amps taper to 0.5 per 100Ah of capacity, and then if possible, float at 13.6 until amps taper to zero, or somewhere just above that.
Don't confuse a float voltage applied after a proper time at absorption voltage, with a float voltage applied from a well discharged state, which is what most chargers described as 'trickle' will do.
All the New TPPL AGMS I have acquired, have performed significantly better in the full charge resting voltage, and voltage retaining under load department, after a relatively quick discharge to 50% State of charge instantly followed by a high amp recharge unitl 14.7v is reached, and then 14.7v is held until amps taper to 0.5 per 100Ah of capacity. A 13.6v float voltage held for many hours after that point will also squeeze in a bit more. If one wants to achieve maximum performance of a TPPL AGM, and ignore their recharge preferences, then one is wasting their money, depending on how much bragging rights mean to the individual consumer, at least initially, before the performance level dropping off prematurely becomes noticeable.