Question 1

Could this meter be used to test a 24v lifepo4 battery for 280 ah rating? would mah be coverted to ah measurement?

Accepted Answer

Depending what kind of test you want to perform, yes, it could be useful.  You could test the voltage of the battery when charged and discharged.  You could test the current the battery outputs with different loads.  And you could measure AH and WH output by the battery in different configurations.  I don't know if it will display AH if it gets that high, but of course you can convert mAH to AH by dividing by 1000.  A 280 AH battery sounds pretty big, possibly able to feed more than 100A, which would exceed the specs of this meter.  So either keep the loads under 100A or else get a different version of this meter with a different shunt bar.  If all you want is a simple "good or not good" battery tester, there may be better products than this.

Question 2

Will this read all the amh (675) from six 6v/225amh series/paralle set up? Or just the amh from the bat it is connected to?

Accepted Answer

If you run all negative current for all batteries through the one shunt then it would read for those batteries.  Because my two banks of batteries are wired separately, I'm going to put in one meter for each bank. Meters are cheap enough, though wiring may be a pain either way you choose.

Question 3

Will this tell me how long my batteries will last under the current load?

Accepted Answer

Amp Hours of the battery ÷ current draw = time
Should give you an idea of how long. The output voltage helps, but varies with discharge rate. 
The anp hours are likely rated over a 20 hour period. You won't get that at higher draws.
For better battery life, don't go lower than 50% depth of discharge in amp hours.

Question 4

Does this unit display live amperage, either plus or minus amps going in or out of the battery? Not a cumulative total over a time period like most?

Accepted Answer

It displays live amperage, always positive, regardless of direction.  And it displays cumulative AH, WH, and runtime.

ASIN	B07W7XXKVF
Best Sellers Rank	#206,186 in Automotive ( See Top 100 in Automotive ) #176 in Battery Testers
Brand	MNJ Motor
Brand Name	MNJ Motor
Color	0-200V Voltmeter Ammeter
Customer Reviews	4.2 out of 5 stars 852 Reviews
Included Components	LCD Display DC Battery Monitor
Item Dimensions	5.12 x 3.74 x 1.38 inches
Item Weight	0.25 kg
Item dimensions L x W x H	5.12 x 3.74 x 1.38 inches
Manufacturer	MNJ Motor
Maximum Operating Voltage	200 volts
Measurement Type	Voltmeter
Model	FBA-UK2025147N
Number of Items	1
Part Number	MNJ-BT-028
Power Source	Battery Powered
Specification Met	Energy
Style	Industrial
Style Name	Industrial
Unit Count	1 Count

DC Multifunction Battery Monitor Meter, 0-200V 0-100A LCD Display Digital Current Multimeter Voltmeter Ammeter for Cars Rv Solar System

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