Hi all, I have an issue with my AGM deep cycle batteries.

jimmytg1

I charge them and they seem to be charged but don’t run for long at all. they are being used in an electric lawnmower and after sitting over the winter with the charge connected the whole time( this is what the manufacturer requires) they work once. but the next time I use the mower it start cutting out after about 20 minutes of use. I’ve charged the batteries and the float voltage is 13.17 Volts and I tested them with a Ancel Ba101 tester. the tester reports that the health is around 40% the voltage is 13.17 and the resistance is 6-7 mohms. everything I read on the web seems to indicate that they are good with the exception of the Health condition being 40%. does anyone know somewhere or someone who knows what might be the issue? the batteries are only a year old and no visual indications of any problems. I even did a load test on them with a full charge and loading them to Approx. 220 Amps for 15 seconds they read between 10.5 - 11 volts. they are rated for 75Ah.

VatrerPower

Despite your AGM batteries showing a good float voltage of 13.17 volts and seemingly passing a load test with voltage drops to 10.5-11 volts under a high load, the key detail here is the battery health reading of only 40% from your Ancel Ba101 tester. This indicates significant degradation, likely due to sulphation or loss of active material inside the batteries, which is common in lead-acid types like AGM after periods of disuse or improper charging.

Given that the batteries are only a year old but have been through a winter connected to a charger, it’s possible that they might have been overcharged or undercharged during this period. Both scenarios can lead to premature battery wear. AGM batteries generally require precise charging voltages, and any deviation can reduce their lifespan.