Presario 1500 laptop battery replacement

I replaced a battery in HP Presario 1500. For some reason the computer does not see the battery. If I start computer on power supply, than remove adapter, computer will stay on and use the battery power, but if I want to start computer using battery power only, it will not turn on.
When I charged the battery it would charge to let say 15% and stop charging, I had to remove and reinsert it to start charging again.
I got it to 100% charge this way. That’s what battery monitor indicate.
When I was at about 30%, I turned on monitor, removed AC adapter and checked a discharge time on battery monitor, let it discharge and time to do that corresponded with what monitor was showing, so that part is OK.
I checked HP site, but no luck. Any idea what could be wrong? :confused: