3 stage charger for true deep cycle battery (Trojan T-1275)

Hahahahahahahahahahahahahahahahahaha...

Your question made my day. Been a sore point since Xylophone Tonkatoy purchased Trace*. You need to set the length of time spent at 14.8 as well.

Take a look at the MEGAWATT manual charger and set the voltage to 14.8. Use an INTERMATIC 4-hour spring wound timer to adjust time. The Mega WILL equalize at 16.2 volts but at not more than 20 amps max. Get the 36 amp model. I use multiple 36 amp Megawatts rather than charge incorrectly.

An old old TRACE 2500SB inverter charger is the best battery charging device ever built. good luck finding one.

Closest converter is IOTA. Otherwise I recommend a Morningstar solar controller that most definitely can be programmed to exactly those voltages and adjust for temperature. Temperature compensation coefficient is also adjustable so get that from Trojan also. Only trouble might be winter snow and sun issues.

And it's Friday the 13th... The T-1275, due to it's shape and proportions, is a bugger to get fully charged. It takes a lot of time to get it top charged. It's shaped more like a car jar.

If you are serious and want the least amount of effort to get as near as possible to fully charged while camping, I would suggest a pair of Trojan T105 GC2 6V batteries, and wire them in series for 12V. They are much less effort to bulk charge, absorption charge and top charge, as well as equalize. They are the proper, most efficient shape and relationship of lead plates to battery acid, hands down.

Just saying, as I have some hands on experience with a couple of T-1275's. Great batteries, powerful batteries, but it takes a long time to get them fully charged, or equalized, not the best attribute when camping with them with running a generator and solar panels. And if you are hooked up to a pedestal, you really don't need GC-2's or a T-1275.

Both Xantrex and Magnum make Inverter/Chargers that are fully adjustable to those voltages.

Victron also makes the short list for adjustable charge rates--but be prepared for sticker shock.

I really prefer AGM jars as there is little maintenance required. Look into used surplus acid telcom 12 volt.

Trojan bumped their EQ voltage from 15.5 to 16.2?

Perhaps they've been reading the Rolls Surrette User Manual

I thought the Megawatt topped out in the 15.3 to 15.5v range?


To be fair to the T-1275, both detailed reports we have on charging these beasts are from those who got them after they have been worked hard and heavy in a golfcart, then relegated to RV duty whose owners performed lengthy conditioning charges to get some more life from them.

Perhaps they might not fight that last 5% of charge so petulantly when newer and given their 14.8 absorption voltage for as long as needed from the start, as the OP seems to want to try and attempt. But agree on the t-105s being superior, if 232Ah is needed.

The capacity retention of my AGM seems dang impressive since I check all its boxes during most every recharge.

I use a Modified Meanwell rsp-500-15 to recharge it on the grid. 40 amps delivered at any voltage between 13.12 and 19.23.

Never got the spring wound timer for it, but I would choose a 6 hour version. 80 to 100% takes 3.5 hours on my 90AH northstar AGM. A whole 18 AH returned in 3.5 hours with 40 amps available.
But but but.....

This interesting writeup on a Lifeline gpl-31t shows just how long it takes to recharge a battery, even when the charging source holds the proper absorption voltage for a slong as it takes:

http://www.pbase.com/mainecruising/effect_of_charge_rate_on_agm_battery

Put the Chambers Bros recording of "TIME!" at 110 db and let it blast for 24 hours.

Getting to 14.8 volts is only 1/1000000000000000000000000000th the objective. It has to stay at 14.8 volts until current drops to a proscribed level then defaults to float voltage.

Small chargers can do this successfully (during which your grandchildren grow to adulthood.) At rationally fast rates of charge, manual timing is essential.

And as far as general charging exists.....dream on. I've have an RV park about three miles from here. I have played with the Wizard chingadera Iota and I have played with the Boondocker.

Conclusion?

These things charge lead acid batteries LESS INCORRECTLY than standard converters.

But for generator charging, long-term, they fail to do the job anywhere near correctly. unless you like 12 hour generator recharge run time.

For these types of batteries, a charger has to go to 14.8 volts and stay at 14.8 volts a lot longer than any of these over-priced gizmos can be programmed for.

TEN THOUSAND DOLLAR chargers are regulated at 14.8 volts, programmed to the size of the battery for timing shut off.

These converter boys are afraid to let people think and calculate for themselves.

No one, not Trojan, not Rolls, not me, can argue with the protocol the US Navy and BuShips tested for submarine batteries. Battery Council International adopted it. Battery equalization voltage is 16.0 not 15.6 or 16.3.

Trojan got cute and got their fingers burned. Now they're up to 16.2
God forbid if they get caught recommending the rote of 16.0 volts.

Landy there is NOTHING WRONG with adopting 14.6 volts for short-term charging an AGM. Nothing. Try it and see how much time it reduces the 80-100 transition. Feed that Northstar as much amperage at 14.4 volts as it takes to maintain 14.4

When amperage drops, bump the charger to 14.6 but no higher. See the difference now?

NinerBikes wrote:
The T-1275, due to it's shape and proportions, is a bugger to get fully charged. It takes a lot of time to get it top charged. It's shaped more like a car jar.

Actually the T-1275 is a smidge bigger than a Group 31.

NinerBikes wrote:
If you are serious and want the least amount of effort to get as near as possible to fully charged while camping, I would suggest a pair of Trojan T105 GC2 6V batteries, and wire them in series for 12V. They are much less effort to bulk charge, absorption charge and top charge, as well as equalize. They are the proper, most efficient shape and relationship of lead plates to battery acid, hands down.

This is EXACTLY the kind of feed back I am looking for !

However, looking at the spec sheet for the T-105, when placed in series, they show the same voltages for charging as the T-1275 !

What are YOU using as a charger !

landyacht318 wrote:
Trojan bumped their EQ voltage from 15.5 to 16.2?

Yep !

Looking at the spec sheet for the T-105, when placed in series, they show the same voltages for charging as the T-1275 !

Trojan got caught with their shorts down around their ankles. This is why I am so steadfast in not finagling with reality. Cyclable batteries develop heat when charging or discharging. The active mass involved versus the radiation square inches determines a manufacturer's charging recommendations. Plate thickness determines the characteristics of a battery - are the plates on a T-1275 the same thickness as the T-105? I believe Trojan only upgrades the paste on their industrial elecro-motive batteries. The 105 and 1275 should have the same paste formulation applied to them.

At 50%SOC total current to achieve 14.8 volts would tell the story.

It is extremely necessary when first charging a battery at "VMAX" for cell to cell temperature and cell variance monitoring. A 1c/min rise must be monitored closely and current reduced if the cell temp achieves 40c.

I'll throw n a tidbit. Charge rejection high impedance is the mark of a poor quality battery. This is a somewhat complex calculation involving weight, plate thickness, and ampere hours at the 20 hour rate. Two evenly matched contenders, the one with the lower impedance will be the winner. But hidden things like plate count can obscure the test. Par for par, a Trojan T-105 will charge easier than a US Battery, Johnson Controls battery or Deka. Such is the nature of deciding which is the bigger inhibitor to marketability: Price or Performance.