Numax battery

[Gramas]

Bought 110ah numax battery 2nd hand assured it worked etc on getting it home and charging it I've found it ain't charging fully only to about 80%
Usage will be to turn over 90hp yam outboard then to run VHF , fish finder, garmin GPS !
My thought n worry is will it be ok to run these for 4/5 hrs if charge is only 80%
I have a backup engine (5hp) so if needed & lost power I'd be able to at least make a very slow route inshore but that is only worst possible case!
Your thoughts please

[Nos4r2]

How do you know it's only taking 80% charge?

[Gramas]

Showing on the charger mate , I'm newbie so bout charger with charge state leds

[Nos4r2]

How long did you leave it on?

Is it sealed and if not, does it need topping up with deionised water? If it's got a dry cell it could cause you problems.

[Gramas]

Left on couple days as slow charge but gradually gain charge then stopped at 80%

[TRevor Lawson]

I would (depending on where bought) take it back and ask for money back as you were poss misled on condition? and buy a new one ,i know they are expensive but out in the boat its not a worry you need.

[Hightower]

I bought a "as new" battery a few years ago from a RIBnet member. He promised me that he'd not used it as it was bought for a project that he never built. I paid me money and took it home. Was flat as a pancake so I tried charging it as you have done, just wouldn't hold a charge. Luckily he'd bought it from a local suppliers so i took it there for replacement, but they couldn't supply me as they had stopped stocking that make over a year before

They did however offer to ship it back to the manufacturers and that's how I found out what happened to it.

If you leave a discharged battery for a length of time then the plates inside get sulphate oxide on them. This ruins your battery and kills your battery for good.

My advice is to never buy a used battery and suggest you give the seller a chance of replacement or a full refund.

[Exe treme]

Hi Gramas

This might be obvious but just a thought: Is your charger rated to 110ah? I had a charger that was only rated to 70ah so would only show about 80% on my 90ah battery. The consistent 80% you are getting sounds similar.

[simsy]

Measure voltages on battery 12.65 volts is 100%. Then load battery with a bulb or 2 of known wattage, confirm this with a current meter. Run a test for hours at his load and see if it holds voltage as it should.

E.g. A 10 amp load should last around 10 hours and run battery to it minimum voltage of around 11.89 volts..

The only way to test battery, except specific gavity...

[doggypaddle]

Test it with a hydrometer if its a flooded wet battery.
1260-1280SG on all Cells. I wouldn't trust LEDs on a charger.
If its sealed then you will need to test the capacity.
best way is with a load that should discharge it in 10-20 Hours that way you can find the 10-20 hour rate. It will only be an approximation because of voltage drop causing the load current to fall, but roughly speaking say a 55 watt headlamp bulb should hold over 10.8 volts for around 24 hours.
if the voltage drops to 10.8 then work the capacity from there. IE 10.8 volts after 6 hours = 6 x 4.5A 27Ah.
a few charge dischaarge cycles may bring any lost capacity back.