Understanding Reserve Capacity vs. Amp Hours: Which Specification Actually Matters?
Battery specifications confuse most buyers. Reserve capacity (RC) and amp hours (Ah) seem to measure the same thing — yet give very different answers about which battery is better for your application.
What Amp Hours (Ah) Means
Ah measures total electrical charge. A 100Ah battery at C/20 delivers 5A for 20 hours before reaching end-of-discharge voltage. But Ah depends on discharge rate — the same battery at C/5 delivers approximately 90Ah, at C/1 only 60-70Ah.
What Reserve Capacity (RC) Means
RC measures how long a fully charged battery can sustain a 25-amp load at 25C before reaching 10.5V (for a 12V battery). A 120-minute RC battery delivers 50Ah at that high discharge rate.
When to Use Each
| Application | Primary Spec |
|---|---|
| Electric vehicle (traction) | Amp hours (C/5 rate) |
| UPS backup | Reserve capacity (minutes) |
| Solar cycling | Amp hours (C/20 rate) |
| Engine starting | CCA |
FAQ
Q: Which is better — higher Ah or higher RC? A: Depends on your application. For solar: Ah. For UPS: RC.
Q: Why different C-rates for Ah ratings? A: Different battery designs favor different discharge profiles. Always check the C-rate.
Need help? Contact CHISEN’s technical team.
Email: sales@chisen.cn | WhatsApp: +86 131 6622 6999 | www.chisen.cn
