Need 12V battery help

[Mozencrath]

Hi all - Im new to the forum, am an electrical engineer, but am stumped!  I have 4 batteries, all are 12v: 110AH SLA, another 110AH SLA, and 2 x 10AH gel cell's.  I bought one of those blue chargers from Walmart and that thing would crank out 16.1VDC so I immediately took that back and ordered a well reviewed Duracell 2A/8A/15A charger from Amazon. It's a 3 stage charger and will max out at about 14.5-15.7VDC. However, my problem is that no matter WHAT battery I charge, the ending voltage after the battery has sat for 24 hours is 13.0 to 13.3VDC at rest....Clearly this is not normal and Im wondering what the deal is. Any advice or knowledge is appreciated. Thanks!

[boB]

If this 13.0 to  13.3 volts is after the charger has been disconnected for a while,  that voltage sounds ~about~ right...

Maybe eve a wee bit high for a 12V battery at rest.  14.5 V charge is probably a good compromise for the
SLA and Gel batteries, too I think.

As long as the batteries haven't been sitting around discharged for a long time and sulfated, they should be OK.
Sounds like you've already "equalized" them with the previous charger.

Let's see what the others say about this, but I think you may be OK.

boB

[Halfcrazy]

Agreed. The 14.5 volts is a controlled over charge if you will. As soon as the charger is removed the battery should drop pretty rapidly down to say 12.4 volts or so at rest.

[TomW]

If this 13.0 to  13.3 volts is after the charger has been disconnected for a while,  that voltage sounds ~about~ right...

Maybe eve a wee bit high for a 12V battery at rest.  14.5 V charge is probably a good compromise for the
SLA and Gel batteries, too I think.

As long as the batteries haven't been sitting around discharged for a long time and sulfated, they should be OK.
Sounds like you've already "equalized" them with the previous charger.

Let's see what the others say about this, but I think you may be OK.

boB

I would have to agree with boB here.

Disclaimer...

Do not mistake me for any kind of expert, I am just a guy who has been doing this stuff for awhile.

Tom

[Vic]

Another factor in resting voltage is the temperature of the battery.  Perhaps the battery(ies)  with highish resting V are cool.

Cooll batts have higher V,  warm one lower V.

Seems to me that the resting V of a 12 V  LA battery should be about 12.7V at 77 degrees F -- 25 C.

For sealed batteries,  a charger with a temperature sensor would be ideal,  although rare for portable chargers,  generally.    Vic

[Mozencrath]

Another factor in resting voltage is the temperature of the battery.  Perhaps the battery(ies)  with highish resting V are cool.

Cooll batts have higher V,  warm one lower V.

Seems to me that the resting V of a 12 V  LA battery should be about 12.7V at 77 degrees F -- 25 C.

For sealed batteries,  a charger with a temperature sensor would be ideal,  although rare for portable chargers,  generally.    Vic

I've been working with SLA batteries for many years and this is the first that I've seen where a group of different batteries all are resting at such a high voltage...I know that gel cells can oft be resting in the 12.9-13.1V range but I've never seen a standard 12v SLA battery resting this much over 13v....The charger works in this fashion:

Stage 1 - High amps (15a on the 110AH batteries) and low voltage (about 11.9-12.3
Stage 2 - High amps and voltage around 13.2-13.8
Stage 3 - Amps taper off and voltage up to 14.7

The batteries are in a climate controlled room at 70F

[Vern Faulkner]

Query: are you measuring the voltage with the controller, or a digital multimeter? I had some voltage concerns, and it turned out the Classic was reading 0.2 volts low ...

[niel]

the voltages do sound a tad high for the agms, but may be good for the brand you have for they do vary a tad. the gels are extremely voltage sensitive and i don't think you should run that charger to them at all unless you can verify that they can take the voltage the charger puts out. gels are also sensitive to high currents as well as many should be charged at roughly a 5% rate. do verify the agm charge specs too as you would not want to slowly fry them.

many of those chargers out there are putting out far too much voltage for many of the batteries used in renewable energy. many times i think it may be better to buy an unregulated high current autocharger, filter it heavily, and feed it into an mppt controller. i will not condone anybody doing this. this voids the controller warranty and you should not trust the autochargers as i blew a controller many years ago when the transformer in the charger internally shorted and sent 125vac down the line. it was a cheap pwm so it could've been worse.

[Mozencrath]

Just depleted and charged again and now the final resting voltage after 24 hours is a whopping 13.45VDC ! This is a 110AH SLA 12V diesel battery 185RC Group 31

[niel]

stop using that charger until you find the specs for charging your batteries. that voltage should not be and it may has outgassed. what batteries do you have, make and model number?