Charging 12V Battery while powering Charger

[spicoli82]

Does anyone see a problem if I was charging my 12v 7a battery while the battery was powering my charger and the charger was charging a battery?

I just want to make sure I'm not going to damage my charger or power panel.

[vintage1]

I've actually done it.Befire I got a 13v power supply..

MOST chargers will be fine, but one or two may not like the higher voltage and the ripple.

[spicoli82]

I just looked at my 12V charger and the output is 12V 2A so that is less power than the battery supplies which is 12V 7A. Maybe it will be ok.

[Peter Khor]

I just looked at my 12V charger and the output is 12V 2A so that is less power than the battery supplies which is 12V 7A. Maybe it will be ok.

fwiw the stated parameters on the charger is a little misleading; a 12V SLA will be up around 14.4V terminal voltage @ fully charged. If you measure the open ckt voltage of the charger, it will be much higher (not to mention the big ripple voltage!)

Still, using the SLA as a 'buffer' shouldn't be much of a problem.

[spicoli82]

Hi Peter,

I'm by no means an electronics expert so if you don't mind, would you please spell out SLA and ckt and also explain what you mean by using the SLA as a 'buffer'?

Thanks much!


fwiw the stated parameters on the charger is a little misleading; a 12V SLA will be up around 14.4V terminal voltage @ fully charged. If you measure the open ckt voltage of the charger, it will be much higher (not to mention the big ripple voltage!)

Still, using the SLA as a 'buffer' shouldn't be much of a problem.

[Rodney]

SLA stands for "sealed lead acid", a typical makeup of many batteries. And yes, using the SLA as a buffer will work fine with the charger hooked up at the same time. The SLA acts just like a large capacitor smoothing out the ripples comming out of most chargers. If in doubt, put an oscilloscope on the terminals while using it and see if you have any large ripples in the voltage, if you do, do not use it in that manner.

[spicoli82]

Thanks for the explaination Rodney.

I was planning on hooking up my power panel AND charger directly to the battery to make for a cleaner installation/setup to hide wires and such. In this scenerio, does the battery still act as a buffer?

Also, since I'm using a sealed battery, does it matter if it lays on it's side instead of upright?

[Chippie]

SLA charging is similar in charging lipos, they need a constant current constant voltage type charger...a car type battery charger is not good for them...

[Rodney]

Chippie, I'm pretty sure you meant "LIMITED" current, not constant current, right? You want a constant voltage but you must limit the current to approximately 0.1C; i.e. a 7 ampere hour battery should not be allowed to charge at a current higher than 700 milliamperes yet you want the capability to hold the voltage to 2.28 volts per cell, 13.7 volts max. to charge a 12 volt battery. These numbers will change slightly as temperature varys but the stated ones are a safe value for most environments. If you watch the temperature, you can go slightly higher than 2.28 volts per cell.

[Chippie]

Rodney, yup quite right, current limited...I shouldnt drink while on the forums.. ;)

the charge rate should be limited to .1C, but there seems some variation in volts /cell when it comes to the charge voltage...I've seen it as high as 2.3-2.4volts..I guess this depends on the type of sla battery and the duty it is required to serve..