For Sale: Mastervolt batteries

[fieldmedik]

We have 4 Mastervolt 6 volt 400 ah AGM batteries for sale. They are a little less than 2 years old. We went to a different system. We are in Sarasota, Fl. They are $600 each new. Asking $600 for each pair. They are heavy so shipping would probably not work well.

[john61ct]

Have they been load tested for remaining AH capacity / SoH ?

[fieldmedik]

I don't know what that means. They were great batteries but we decided to go with lithium. I did take them to west marine to have them checked because they had been sitting a while. They said they were good. Not sure what test they did. They kept the batts overnight if that means anything.

[john61ct]

You will get a higher price from them by measuring State of Health, % of original AH capacity remaining.


Only way without thousands of dollars worth of lab grade equipment is called a

20 Hour Capacity Test:

An accurate AH counter can be used, but not necessary, just an ammeter and a stop watch.

#1 Benchmarking to 100% Full is straightforward, hold Absorb until trailing current drops to endAmps. If not mfg spec'd I use .005C, .5A per 100AH.

Then equalize if appropriate, and allow the batt to rest disconnected for at least 24 hours

#2 Make certain battery temperature is between 75F & 80F

#3 Apply a .05C load = Ah Capacity ÷ 20 (small light bulbs and/or resistors can work)

#4 Connect an accurate digital volt meter to the positive and negative battery terminals

#5 Start DC load and a stop watch at the same time

#6 As battery voltage drops, during discharge, adjust the DC load to maintain as close to the C÷20 rate as is humanly possible

#7 Immediately stop the discharge test when battery terminal voltage hits 10.499V

#8 Note the hours and minutes of run time on the stop watch and figure your percentage of 20 hours that it ran. This is your batteries Ah capacity or state of health as a percentage of the "rated" capacity. For example if a 100Ah battery ran for 16 hours it's testing at 80% of its original rated capacity. By industry standards lead acid batteries are considered “end of life” when they can no longer deliver 80% or more of their rating. They can still work beyond this point but are considered **less safe** and can be less predictable.

#9 Once you hit 10.499V recharge the battery immediately at the 20 hour rate. Once the battery is full, follow this up with equalization if appropriate

A long slow recharge (20 hour rate) can have a slight reforming effect on batteries and can actually serve to recover some lost capacity. It is not uncommon for a battery to have **more capacity** after a 20 hour test than it had going into it.

Credit to Maine Sail, https://marinehowto.com/programming-a-battery-monitor/

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