I'm trying to replace two Data Safe NPX-35, 12V, 8.5Ah SLA batteries. When I called support to figure out what to order (before pulling the actual batteries out) they said that any 12V 9Ah SLA would work...

So, should I go with the 12V 9Ah or just get the exact 12V 8.5Ah SLA?

Thanks for your help!


closed as off-topic by user17592, Leon Heller, Matt Young, placeholder, Daniel Grillo Sep 5 '14 at 17:55

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Amp-hours is a measure of the battery's capacity, and more is better. The 9Ah battery can supply, for example, 1A for 9 hours while the 8.5Ah one can only supply 1A for 8.5 hours. The important thing is to match the voltage of the battery, which in this case is the same at 12V.

So there's no reason not to get the 9Ah battery -- it's the better one.

  • \$\begingroup\$ Well explained. The only other thing to consider (since I guessing these batteries are for a UPS), is the maximum discharge current. This needs to be the same or higher. Since UPS' tend to discharge batteries over a short period of time, a battery with a high internal resistance might not be up to the job (or be liable to overheat). More info: en.wikipedia.org/wiki/Battery_(electricity)#C_rate \$\endgroup\$ – Oliver Sep 5 '14 at 14:37
  • \$\begingroup\$ This is actually for a piece of audio equipment--the Beacon BEA-7500 PA system. I will make sure I look into that when ordering. Thanks! \$\endgroup\$ – Anton Rasmussen Sep 5 '14 at 14:51
  • \$\begingroup\$ In which, you'll be fine. Googling that PA suggests that the battery will drain over 7hours or so. I was worried about you discharging it over 10 minutes. \$\endgroup\$ – Oliver Sep 5 '14 at 15:11

For such a small difference, putting the higher capacity battery into a unit designed for a lower one should cause no harm.

With a large mismatch, and if the unit contains a charger for the battery, a battery with significantly higher capacity may not get charged properly. But again, the difference between 8.5 and 9.0 Ah is too small for that to matter.


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