NASA BM1

[sailaboutvic]

Hi Vic
First things is ignore the 104% charge. This is almost always wrong - by a long way. Ignore this screen completely!
I expect your fridge will take a lot more than 3A. Mine takes 6.2A and I expect your is similar to mine.
9.7A at midday when the battery voltage is 13.7v sounds about right to me when the fridge is running.
What solar controller do you have? Mine is a Victron MPPT controller that was new earlier this year so the latest version. It charges my sealed lead acid batteries to 14.4v then drops down to a float and absorption voltage of about 13.3v. The time from 13.7v up to 14.4v is quite long as the batteries can only take a diminishing current.
My BM1 will show %age charge at 104% long before reaching full charge, then if really at 100% and the fridge cuts in it will drop quickly to 90% or 80%. The %age charge screen should really be ignored for all practical purposes.

Thanks for that info , my fridge uses around 3 to 3.5 A , its keel cool and I have check it .
I agree with you you can't take any notices of the % on the BM1 .
My MPPT isn't as good as your it's a Solar although I do find it pretty reliable on reading .
Just check it agin as I writing this , charge or 2.7 and the BM1 saying discharge of .07 that because the fridge kicked in and we have some charging of PC going on .
Good to hear you agree with my sum at less I know it working about right .

 

[lw395]

Yes, I would say your batteries are shagged. But before you replace them, try renovating them with one of those smart chargers that zaps them with alternating current to break off the sulphating on the lead plates. I renovated mine three years ago and they are still like new.

What device did you use?
I'm interested in your experience here.
I have played around with 'desulphators' of various sorts, TBH the best I have got is restoring batteries from 'pretty damned dead' to 'moderately useful for testing and odd jobs'. Nothing seemed to come near restoring original capacity. Maybe I have only started with batteries that were too far gone?
I was mostly playing with batteries I got for nothing, making them run a few lights in my lock-up.