In line meter....What do these two readings mean?

Blindowl1234 · March 2016

Ok I've got an in line meter on my small 125 watt solar setup. It reads panel volts, watts, amps, watts peak, amps peak I'm doing that from memory so I think that is right. It also at the end of a bright sunny day like today, it shows 144 Wh and 8.70 Ah. I'm not sure how to interpret these last two readings? I'm guessing it's 144 watt hours into the battery bank (two 12 volt batteries). If that's correct I'm using 18 watts for 10 hours each night, so I'm drawing 180 watts. If I'm doing any of this correct this means I'm using more than I'm putting back in? I know this is simple for the rest of you lol, but I'm lost. Thanks!

vtmaps · March 2016

Tell me more about this meter (brand and model)... does it count the current into AND out of the battery? Do you reset it to zero every day (before it counts up to 144 Wh)?

'amphours' does not tell you how much energy is put into or removed from the battery. An amphour at 12 volts is not as much energy as an amphour at 13 volts. If you are seeing 144 watthours corresponding to 8.7 amphours, that suggests the battery voltage was 144 ÷ 8.7 = 16.55 volts. That's a very high voltage for a 12 volt lead acid battery.

Blindowl1234 said:

I'm using 18 watts for 10 hours each night, so I'm drawing 180 watts.

No, you are drawing 18 watts. The energy you have drawn over a 10 hour period is 180 watthours.

--vtMaps

Blindowl1234 · March 2016

It looks just like the Renogy 150 amp wattmeter...it's a knockoff of it anyway. Yes I reset it everyday first thing in the morning. I check the batteries in the morning and at the end of the day with a DMM. Battery voltage never goes above 14 volts and is usually about 12.5 in the morning. I've got the meter hooked up so it should be reading the measurements from the panels rather than the batteries. Hope this helps.

scrubjaysnest · March 2016

If these are flooded lead acid, FLA, then 14 volts is not high enough to get a complete charge; unless that is a resting voltage under no load for about 4 hours. 12.5 volts under resting no load conditions, again for about 4 hours indicates a battery very close to 50% state of charge. Again no enough information to give more then a general answer which could be completely wrong. Since you reset the meter each day this implies you are putting in 144 Wh per day. It's possiable the Ah reading is a peak value trapped at some part of the day.

vtmaps · March 2016

scrubjaysnest said:

If these are flooded lead acid, FLA, then 14 volts is not high enough to get a complete charge

I agree.

scrubjaysnest said:

12.5 volts under resting no load conditions, again for about 4 hours indicates a battery very close to 50% state of charge.

I do not agree with that. 12.5 volts (resting) is very near full charge (assuming flooded lead acid battery). If course, near full charge is not good enough... If you only achieve 98% SOC (state of charge), after awhile that 98% becomes your new 100%. In other words, 98% of 98% of 98%... pretty soon you will have a battery with permanently diminished capacity.

--vtMaps

Blindowl1234 · March 2016

Thanks guys yes they are flooded lead acid. Well it's working good so I'm ok with that. Was just curious what the readings were that I couldn't figure out. Thanks for the ideas and info.

BB. · March 2016

I do like a second meter to confirm basic voltage and current measurements... This Sears AC/DC Current clamp DMM meter is "good enough" for most of our debugging needs at ~$60 in the USA.

Current clamp meters (that support DC for solar panels and battery based systems) makes current measurements very easy and safe.

-Bill

In line meter....What do these two readings mean?

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