It sounds to me that you may have 1 or more bad cells in that battery. I'm no expert, but i suggest that you leave that battery to rest for a couple of days after a long slow charge and see if it still copes with a load test.
Assuming you're using them in parallel (connected for 12v), you could leave out the dubious battery. you may find that he remaining batteries work a lot better without it.
no offense, battery-recon UK, but I've yet to see any 'independent' proof of the effectiveness of the pulse desuphators. As chrisb says a long slow charge seems to be the most reliable way to bring a battery up to it's full charge.
No offence taken Mab. However, if everyone thought that new technology wouldn't work we would still be riding around on horses and fighting of Dick Turpin!
I have been in the electric vehicle business for 20 years and as stated above I have met many modern day Dick Turpin's trying to convince people that there are all types of liquids, serums and old wife tale potions that can 'refurb' batteries.... and they were driving a car much more expensive than a G-Wiz.
I came across my machine in the US. It is called the BATT RECON and was developed by a company in the Aerospace industry. I can assure you the machine DOES work, it can be used as an annual preventative maintenance tool to remove annual sulphate removal (same as changing oil on a petrol/diesel engine) or it can be used to bring 'graveyard' batteries back to life, providing the plates are not warped, shorted or damaged. 70% of batteries all scrapped batteries can be rejuvinated.
When working the BATT RECON 4800 AGC along with the latest CADEX CA12 battery tester, we can prove that the BATT RECON works. As an example: I desulphated a battery pack today on a golf car using Trogan T105r batteries , the run time of the batteries before sulphation removal was 74 minutes at 95% charge.
Following desulphation removal and re-charge, a discharge to 97%, the run time was increased to 107 minutes.
The time taken was 35 minutes with 3 hours charging using the golf car standard Delta Q solid state charger.
I can provide the before and after print out along with the reduced impendence mOhms. Impenance increases in the battery as sulphates form.
As stated the new Cadex battery tester proves that the BATT RECON really does work, I would not have invested £6000 on the machinery and alot more to be the UK distributor.
If you look at my website, customgolfcars dot co dot uk (newbie, so the site won't let me post my site details) and batt recon dot com, you can see for yourself. The machine can desulphate a motorbike battery, auto battery and up to fork lift batteries.
If you would like a demo or further details call me, numbers on the website.
BATT RECON UK