Trojan T-1275 Trouble

I had a pair of T-1275s in a past set-up. Great batteries for RVing!

What you need is to charge the battery at 14.8v or so to get the SG up. I suspect the charger you had them on was only a 13.x voltage charger.

Right now you have the acid at the bottom of the battery giving you that 13.1 volts, and the hydrometer is not getting at it. You need proper "gassing voltage" to get the electrolyte mixed from bottom to top.

Make sure the solar controller's high set point is 14.8 volts too, or else it will happen again.

The built in system will not charge that well at all

T1275s will be my next battery purchase. Nothing but good reports.

Trojan charging specs are different than any other flooded lead acid battery.

I do not know of ANY off-the-shelf battery charger that will do the 14.8/13.5/16.2 Bulk/Float/Equalize that Trojan recommends.

You can do it "manually" with a decent 30V, 10A lab power supply that has both constant voltage and constant current, but it is a pain.

theoldwizard1 wrote:
Trojan charging specs are different than any other flooded lead acid battery.

I do not know of ANY off-the-shelf battery charger that will do the 14.8/13.5/16.2 Bulk/Float/Equalize that Trojan recommends.

You can do it "manually" with a decent 30V, 10A lab power supply that has both constant voltage and constant current, but it is a pain.

Yes you do. I have posted before about this one that is adjustable from 13 to 16.5 volts. Works great. Not very costly either! You can get these LKs in various amp "sizes" from 35 to 120 amps.

https://www.boatandrvaccessories.com/products/powermax-pm3-60lk-12-volts-60-amp-power-converter-battery-charger-w-led-light

BFL13 wrote:
I have posted before about this one that is adjustable from 13 to 16.5 volts. Works great. Not very costly either! You can get these LKs in various amp "sizes" from 35 to 120 amps.

Powermax LK Series manual

These instructions are not very clear to me.

ADJUSTING FIXED VOLTAGE : The unit is on the three stage charging mode firstly. 1. move the switch A to "Adjust Fixed Voltage", move switch B gently to adjust voltage from 13~16.5V, and get a fixed output voltage. 2. make sure the voltage as 14.6V, move the switch A to " Three stage charging", then the unit back to standard “Three Stage Charging”, run 14.6V almost 0.5 hour, 13.6V almost 12 hours and then to 13.2V. The voltage value of 3 stage charging will be changed with fixed voltage changed when the unit on “Three stage charging”.

Switch A appears in fact to be a switch. Switch B appears to be a small adjustable resistor.

How does changing the "Boost" (Bulk) voltage setting affect the "Normal" (Float) setting ? Also, this charger does NOT have an Equalization mode.

Yes it is sort of complicated till you do it in real life. Switch A makes it a typical three stage converter and if you monkey with the pot with the switch set to the left, it will change all three voltages at once. You can restore that to original though.

The real benefit is as a singe voltage manual charger with switch A to the right, set to any voltage you like with the pot B.

This means you can set it to say 14.8 and leave it there till the battery is charged, then drop that voltage to 13.6 or whatever float voltage you want and leave it there. Or when the batts are done at 14.8 just switch A back to the left and it will be in three stage and do that float voltage.

You can equalize by first charging the batts at 14.8 till full, then crank the voltage up to 16.2 and do your equalize, then crank the voltage back to whatever.

It is a pain to use a little screw driver in that hole B to change the voltage, but you don't have to do it often. I much prefer the model with the pot knob on top you can just dial around, but those models cost way more for the privilege.

You really need a voltmeter you can see while operating this thing and an ammeter too if you are trying to tell when your AGMs are down to accepting 0.5a per 100AH of battery after charging at that chosen single voltage using pot B that matches your AGM battery specs for charging. I have my Trimetric for that. You can get by with other meters though.

It is no worse operating an LK like those than setting voltages with an inverter/charger that has fancy options. the big thing is that you can match your charging to the specs of any battery you might have and they vary a lot. Even AGMs have all different levels of charging voltages.

Thanks for the responses! More would be welcome too.

The Schneider controller is configurable to the Trojan battery profile. And I think that I did that correctly, although it might be a good idea to double check. But I did have that problem with the solar panel connector that wasn't letting the battery charge. So I've decided to try the Schneider again, but instead of powering it with the solar panels I'll feed it with an adjustable power supply set at the same voltage that the solar panels provided. BFL13, you make a good point about the electrolyte being different at the top than the bottom. That sure explains the difference between the voltmeter and hydrometer readings that I was seeing. I plan to do an equalization charge in the hope that that will mix things up a bit.

There is such a thing as supplying an MPPT controller with a DC power supply and use the MPPT controller's charging profile. That is because the controller is a "buck converter". You need to organize that power supply to have an appropriate input to get the MPPT controller output you want.

I am not clear that you can do that at all with a PWM controller, so you will have to look that up if your controller is PWM.

You can confirm the output voltage of your controller with a multimeter. It should be 14.8 at 25C, or as adjusted for temperature from that. It should stay at 14.8 long enough to get the job done, and not drop to 13.6 too soon. Some have a built-in two- hour time limit at the 14.x and then drop to their 13.x. "Too soon" is before the SG is back up to 1.275