Midnite Solar MNBCM Battery Capacity MeterWrite a review

I have used the MidNite battery monitor for several years now and it is quiet good for what it does. It gives me a quick check on the state of charge for the 20 KW battery bank in my solar system. If one wants to really check their battery system their isn
t any monitor for that job. It must be done with hands on at the battery bank.

This review is iIn response to Travis A
s review of Midnight Solar
s MNBCM Batter Capacity Meter. I too have one of these meters and I
m mostly happy with it. This particular meter is meant to monitor a battery at
rest
, i.e. not charging and not discharging. One might consider that a drawback, but at _$70 you
re not going to get a meter that provides accurate SOC while in a charging/discharging state. Having said that, I monitor my batteries with the MNBCM after the sun has set and the batteries are in a mostly static (no load) condition. I usually allow an hour for the battery to achieve that
resting
state. That
s how battery SOC is most accurately tested. Likewise, when doing a specific gravity test, you don
t do it when the battery is charging or discharging, you do so when the battery has been in a resting state for a specified time.

If you want a meter that will give precise readings of your batteries
condition, this is not the meter for you.

Like any meter that works solely off of battery voltage, it will give different reading at different load levels. It
s simply because batteries read a lower voltage under load due to internal resistance.

For example, if it reads 80% at 8:00 pm with just a few CFL lights on, you likely have a good charge. If it reads 80% at 8:00 pm with the freezer running, you likely have a great charge. If it reads 40% at 8:00 pm with the freezer running, you likely have a good charge and it will go up into the 70%-80% range when the freezer shuts off. If it reads 40% at 8:00 pm with just a few CFL lights on, It
s time to fire up the generator and recharge, before damage is done.

With my refrigerator, freezer and computer all running simultaneously I have seen readings as low as 20%. 20 minutes later, when the refrigerator, freezer and computer are turned off, it went back up to 90%. The reason was the heavy load and the internal resistance of the batteries. No worries there. But, an unexplained 30% means getting out the volt meter, the hygrometer and checking everything!

Once you learn how your particular battery bank works with your power usage patterns and particular charge controller and panels, this meter will help you spot variations from the norm. This won
t do it for you like the $400 meters.

The most useful feature is the
Time since the last full charge
indicator. It keeps track of how long it
s been since the batteries have had a good full or equalizing charge. It resets the timer when it senses a full charge. A week later it goes to yellow and then after another week it goes red. It remembers when we tend to forget.

In short, it
s a
quick and dirty
way to keep track of your battery bank. It
s best mounted someplace that you will see it often like over the kitchen light switch or over the TV. Batteries don
t make any noise useful in keeping track of how they are doing and you can
t see electricity. This is the cheapest way to keep tabs on the general, but not the detail, condition of your batteries.

Do not buy this for a solar/renewable system. This thing is correct twice a day just like a dead clock.

It has no delay when discharging. It will fall like a rock and won
t display anything even close to the truth.

When charging it is even more worthless if that is even possible. It reports a battery as fully charged at 12.7 volts. They didn
t even try.

I posted on their forums (they deleted) and the Ryan the technical support manager said it was designed to show how long since the last full charge and that its not designed to show state of charge.

This would be fine for an RV or boat but is beyond worthless in a PV system.

I bought this meter to tell me the SOC of my battery. It was at 100% when I hooked up a small tv. It went to 70% in about 2 seconds. I unpluged the tv and it went back to 100%. I need a meter to tell me the correct % so that I will not damage my battery. This is not that meter. I guess you get what you pay for