Mecer 720w Inverter with 200ah gel battery issues

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hmartens

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Last weekend I bought a Mecer 720W Inverter and a 200ah Sun God gel battery. I am using the battery cables that came with the inverter.

Today during loadshedding I tested it with running the xbox and tv and after about 1h30 the inverter started beeping for low battery but the inverter shows there are 3 bars battery left and my usage is only on 1 bar. While it was beeping, it showed two bars left, basically 50%, but then I switched off the xbox and it showd 3 bars power left and stopped beeping.

I have an Xbox One S, 48" curve tv and a soundbar plugged into a surge protection plug and then into an extension cable into the inverter. I also have a macbook air plugged into the inverter.

This is what I'm running on the inverter:

- 2015 Macbook air: 36w
- 48” Samsung curve TV: 135W
- Xbox One S: 90w
- Soundbar with subwoofer: 50w
- 27” Samsung monitor: 36W
- 21” LG Monitor: 24W

Based on my calculations, my battery should be lasting a few hours unless I am missing something. Why would my inverter start beeping for low battery after 1h30 when the inverter shows 3 lines left on the battery and only 1 line of load?

Thanks for any help/feedback/guidance
 
Last edited:
hmartens said:
Last weekend I bought a Mecer 720W Inverter and a 200ah Sun God gel battery. I am using the battery cables that came with the inverter.

Today during loadshedding I tested it with running the xbox and tv and after about 1h30 the inverter started beeping for low battery but the inverter shows there are 3 bars battery left and my usage is only on 1 bar. While it was beeping, it showed two bars left, basically 50%, but then I switched off the xbox and it showd 3 bars power left and stopped beeping.

I have an Xbox One S, 48" curve tv and a soundbar plugged into a surge protection plug and then into an extension cable into the inverter. I also have a macbook air plugged into the inverter.

This is what I'm running on the inverter:

- 2015 Macbook air: 36w
- 48” Samsung curve TV: 135W
- Xbox One S: 90w
- Soundbar with subwoofer: 50w
- 27” Samsung monitor: 36W
- 21” LG Monitor: 24W

Based on my calculations, my battery should be lasting a few hours unless I am missing something. Why would my inverter start beeping for low battery after 1h30 when the inverter shows 3 lines left on the battery and only 1 line of load?

Thanks for any help/feedback/guidance
Click to expand...
using all those devices at the same time you are looking at 29a so in a perfect world you should be able to use the devices for almost 3 hrs 25min

but we don't live in a perfect world normally deep cycles are rated to deliver its capacity over a 20hrs period ie max amp draw of about 10a anything more than that you have extra peukert losses obviously the more you are over the higher the losses

so with peukert losses you will most likely only get 2.4hrs until 50%soc
i used the 1.1 peukert number the calculator defaults to would have to find your battery specs to get a more accurate calculation


the cheaper the battery normally the higher the peukert number

in the below graph you can see with a high load of 29A the outlook looks bleak with a high peukert number


and also
you do experience voltage drop due to load, the battery SOC bars uses voltage to estimate how full your battery is, so trying to estimate this while in use is problematic as voltage drop will mess with your estimates

hence why the change when removing load
 
hmartens said:
Last weekend I bought a Mecer 720W Inverter and a 200ah Sun God gel battery. I am using the battery cables that came with the inverter.

Today during loadshedding I tested it with running the xbox and tv and after about 1h30 the inverter started beeping for low battery but the inverter shows there are 3 bars battery left and my usage is only on 1 bar. While it was beeping, it showed two bars left, basically 50%, but then I switched off the xbox and it showd 3 bars power left and stopped beeping.

I have an Xbox One S, 48" curve tv and a soundbar plugged into a surge protection plug and then into an extension cable into the inverter. I also have a macbook air plugged into the inverter.

This is what I'm running on the inverter:

- 2015 Macbook air: 36w
- 48” Samsung curve TV: 135W
- Xbox One S: 90w
- Soundbar with subwoofer: 50w
- 27” Samsung monitor: 36W
- 21” LG Monitor: 24W

Based on my calculations, my battery should be lasting a few hours unless I am missing something. Why would my inverter start beeping for low battery after 1h30 when the inverter shows 3 lines left on the battery and only 1 line of load?

Thanks for any help/feedback/guidance
Click to expand...
I think this is a perfect case of why one should ignore the bars and get a voltage display.
 
leon.davibe said:
using all those devices at the same time you are looking at 29a so in a perfect world you should be able to use the devices for almost 3 hrs 25min

but we don't live in a perfect world normally deep cycles are rated to deliver its capacity over a 20hrs period ie max amp draw of about 10a anything more than that you have extra peukert losses obviously the more you are over the higher the losses

so with peukert losses you will most likely only get 2.4hrs until 50%soc
i used the 1.1 peukert number the calculator defaults to would have to find your battery specs to get a more accurate calculation


the cheaper the battery normally the higher the peukert number

in the below graph you can see with a high load of 29A the outlook looks bleak with a high peukert number


and also
you do experience voltage drop due to load, the battery SOC bars uses voltage to estimate how full your battery is, so trying to estimate this while in use is problematic as voltage drop will mess with your estimates

hence why the change when removing load
Click to expand...
Why do the bars show 50%?
 
leon.davibe said:
using all those devices at the same time you are looking at 29a so in a perfect world you should be able to use the devices for almost 3 hrs 25min

but we don't live in a perfect world normally deep cycles are rated to deliver its capacity over a 20hrs period ie max amp draw of about 10a anything more than that you have extra peukert losses obviously the more you are over the higher the losses

so with peukert losses you will most likely only get 2.4hrs until 50%soc
i used the 1.1 peukert number the calculator defaults to would have to find your battery specs to get a more accurate calculation


the cheaper the battery normally the higher the peukert number

in the below graph you can see with a high load of 29A the outlook looks bleak with a high peukert number


and also
you do experience voltage drop due to load, the battery SOC bars uses voltage to estimate how full your battery is, so trying to estimate this while in use is problematic as voltage drop will mess with your estimates

hence why the change when removing load
Click to expand...
Thanks for the explanation, what you say makes sense although I only got 1.5 hours before it started beeping. he first time it was beeping and showing low battery, it was flashing 3 lines for battery. I then unplugged the xbox and it showed then I still had 3 lines of battery. I then tested it again and plugged in the xbox and it's fine for a few seconds and then it started beeping again and showing 2 lines of battery left. Unplugged the xbox and it went back to 3 lines of battery left.

That's what I don't understand. Like you said, I should get atleast 2.5h until battery is 50%. I wonder if it's a cheapskate battery but how do you tell a good one from a bad one except the price? Is the weight always the definitive tell whether a battery is good or bad?
 
wingnut771 said:
Very possible to have a DOA battery also.
Click to expand...
I have emailed the supplier and will see what they say. It was rather cheap, R3500 and only weighing 32kg, but I don't know anything about batteries or inverters and I just don't know what is good and what is bad.
 
Is it ok for me to plug the inverter into a surge protector then into Eskom power? Also,, is it ok that I have my TV and Xbox plugged into a surge protector and then into the inverter? I then also have a 20m extension cable running to another room for my two pc monitors.
 
hmartens said:
Thanks for the explanation, what you say makes sense although I only got 1.5 hours before it started beeping. he first time it was beeping and showing low battery, it was flashing 3 lines for battery. I then unplugged the xbox and it showed then I still had 3 lines of battery. I then tested it again and plugged in the xbox and it's fine for a few seconds and then it started beeping again and showing 2 lines of battery left. Unplugged the xbox and it went back to 3 lines of battery left.

That's what I don't understand. Like you said, I should get atleast 2.5h until battery is 50%. I wonder if it's a cheapskate battery but how do you tell a good one from a bad one except the price? Is the weight always the definitive tell whether a battery is good or bad?
Click to expand...
From what i understand(still educating myself on this)

The peukert number is an indication of the degredation of capacity under load

To get this degradation curve the battery has to be tested at at least two different rates
ie lets say 20Hrs and 5hrs to discharge its full capacity

Then this number is used by calculations to estimate how it will behave at different current draws to determine how much of the capacity you will get after losses

The 2.5hrs is based on a peukert number of 1.1

If you look at the graph if your batteries peukert number is different you can expect less usable capacity

ie the calculator gives me
at 1.2 1hr 45min
at 1.3 1hr 15min
At 1.5. 38min

At best you will get a rough estimate and this calculations should be taken with salt

But you can see if you have a higher peukert number it changes things drastically

Lithium isn't prone to the same peukert effect

So based on your load of 371w and 1.5hrs runtime of your battery

You would probably get the same runtime from a 50ah lifepo4 than the 200ah deep cycle

For loadshedding imo a person should only buy lithium
Especially if pulling anything more than a tv

Your peukert number reduces as you have less load

So unfortunately with the lead acids you have to sacrifice devices or have a way bigger bank to get the peukert effect lower

ie to pull through with your load in a 2hrs you would need in lead acid bank probably 300ah and for a 4hrs 600ah

Lithium you would probably need at least 72ah per 2hrs

Only an estimate so buying slightly bigger may be a good idea
 
Last edited:
hmartens said:
I have emailed the supplier and will see what they say. It was rather cheap, R3500 and only weighing 32kg, but I don't know anything about batteries or inverters and I just don't know what is good and what is bad.
Click to expand...
industry doesnt have a standard on weight because different compositions make for different weights but a lead antimony battery is usually 18 kg min per 100 amp .but if you have a thick casing it screws with the formula as does a thin casing .
 
also remember all the googled junk ,laws ,formulas etc mean nothing in the real world and batteries dont read google ,chinese manufacturers work according to their rules not some funky formula on google .drop your consumption untill you find a happy medium ,make sure the charger is right for the battery formulation and live with what you have untill you can get a better formulation or an upgrade .the antimony batteries we fit to ups systems weigh 44kg per 150 amp .and last for years because each battery has a built in bms and are made in Canada to international specs not China Export (C E ) specs
 
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also your battery discharge will probably be over 10 hours and not as googled .so i would say a max of 3 amp per hour over a max of 10 hours ,would be realistic .
 
hmartens said:
That's what I also wonder...
Click to expand...
the bars is voltage based and naturally the way each brand chooses to use the bar indicator may vary

ie 2 bars could mean anything between 25-50% or it could mean anything between 50-75%
dependant on design choices

ie my shoto will light up 2 lights ie over 50% capacity left but not the 3rd light even though my soc is 70% ie i don't have 75% capacity left and thus the 3rd light will only light up once over 75%

but some could choose to have the indicators to indicate that you are in that bracket ie show 3 bars/lights because between 50-75% and then 2 bars for between 25-50%

so how is 45% shown and 55%?

2 bars 3 bars?

also the bars is voltage based so a higher load will see voltage drop showing a lower soc than actual

example axpert inverters will use different cut-off voltages based on load ie under heavy load they will switch of at a lower voltage than at lower load to compensate for voltage drop to try and switch off at the same soc
 
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