Electronic – Battery Nominal Capacity

batteriescapacitycurrent

I was wanting to buy a 12v battery that could supply 8A for around an hour. I thought I knew what I was doing and so ordered the following 12v 10Ah Deep Cycle battery.

Yuasa REC10-12 BATTERY Deep Cycle Cyclic SLA 12V 10Ah

I chose deep cycle as from my understanding, they cope better with running the battery down low. And I chose 10Ah as I thought that meant it could supply 10 amps for up to an hour.

However, upon testing this, it lasted about 10 minutes 🙁

Having done a little more research, I have found out the the 10Ah stated is not as simple as I thought it was, and you have to consider the Nominal Capacity specs to figure out how long you'd actually get.

When I look at other battery data sheets, they specify this data clearly, for example here :

http://www.power-sonic.com/images/powersonic/sla_batteries/ps_psg_series/12volt/PS-1220_11_Feb_21.pdf

Nominal Capacity

 20-hr.    (125mA to 10.50 volts)      2.50 AH
 10-hr.    (220mA to 10.50 volts)      2.20 AH
 5-hr.     (400mA to 10.20 volts)      2.00 AH
 1-hr.     (1.5A to 9.00 volts)        1.50 AH
 15-min.   (4.5A to 9.00 volts)        1.13 AH

But having looked at the datasheet for the battery I bought, it doesn't show the Nominal Capacity? could anyone help me to understand from the datasheet, how I would work out the expected runtime at 8A?

Best Answer

With the information you added in the comments of your question, I'm pretty sure now that the charger you used killed the battery by overcharging it.

It says "Please note - Not suitable for AGM batteries" in its description and you've got a relatively low capacity AGM battery. The charger probably kept the battery at a voltage of more than 14V for the whole night, overcharging it dramatically.

Edit: The description of the charger also says that it's "not suitable for long-term connection", indicating that it does indeed just keep pumping current into the battery even when it's full.

You should use a 16Ah deep-cycle 12V battery with a suitable charger. You also shouldn't let the battery charge over night but stop the charging immediately when it's full. (Or get a charger that does this for you)