AlphaJohn

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For comparison:

1634330456825.png

That is with a Media PC, 2 x Pi's, a NAS and 2 Wifi's + Alarm on
Batteries Floating at 13.7V
 

MrR030TZA

Member
Joined
Aug 9, 2018
Messages
25
Not bad. Disconnect them and let them rest for an hour then check again before doing jumper cables. If still the same then what is the load you're running?
Hi, so tested the voltage again today, all disconnected before waiting an hour and got 12.95 V on the one and the other 13.44 V, and after waiting an hour or more, the 1st one is now 12.94 V and the 2nd is 13.30 V. The load of what I'm using is around 290-300W. You think I still need to balance the batteries?
 

wingnut771

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Feb 15, 2011
Messages
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View attachment 1168204

I installed a small voltmeter
Nice!, Now install another 2 12V ones so you can monitor balance.
Hi, so tested the voltage again today, all disconnected before waiting an hour and got 12.95 V on the one and the other 13.44 V, and after waiting an hour or more, the 1st one is now 12.94 V and the 2nd is 13.30 V. The load of what I'm using is around 290-300W. You think I still need to balance the batteries?
Yeah, I would. :thumbsup: Try turning the brightness down on the TV, it helps a lot. 300W is cutting it fine for 50% after 2.5 hours.
 

MrR030TZA

Member
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Messages
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Nice!, Now install another 2 12V ones so you can monitor balance.

Yeah, I would. :thumbsup: Try turning the brightness down on the TV, it helps a lot. 300W is cutting it fine for 50% after 2.5 hours.
Ok thx, excuse the stupid question but when connecting the jumper cables, I connect positive to positive and negative to negative, correct?
 

wingnut771

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Ok thx, excuse the stupid question but when connecting the jumper cables, I connect positive to positive and negative to negative, correct?
Correct (like when your car battery is flat and you mate brings his car and you connect jumper cables, + to + - to -), then the current will flow from the 13.4V battery to the 12.9V one. That's why jumper cables get warm as there is some big current moving when there is a big voltage difference.

Obviously this is when they are 2 standalone batteries and are disconnected from series and inverter connection first and not just connecting jumper cable to your setup as is.
 

mikewazar

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Jul 23, 2021
Messages
91
Sitting at 50W pulled from wall right now. I'm concerned about how precise these voltmeters are. Comparing to my decent one it shows 27.4 versus the blue LED one showing higher voltage.
 

wingnut771

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How large a difference in voltage should I be concerned about?
Maybe more than 0.1V or 0.2V? It's important they both get to 14.1V (28.2V) before it floats. The inverter charger is just seeing one 24V battery. So you could get one battery overcharging (15V) and the other undercharging (13.2V) but still read the same 28.2V. The point is they should be similar.
 

wingnut771

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Sitting at 50W pulled from wall right now. I'm concerned about how precise these voltmeters are. Comparing to my decent one it shows 27.4 versus the blue LED one showing higher voltage.
Is there not an adjustment pot on the back?
 

MrR030TZA

Member
Joined
Aug 9, 2018
Messages
25
Correct (like when your car battery is flat and you mate brings his car and you connect jumper cables, + to + - to -), then the current will flow from the 13.4V battery to the 12.9V one. That's why jumper cables get warm as there is some big current moving when there is a big voltage difference.

Obviously this is when they are 2 standalone batteries and are disconnected from series and inverter connection first and not just connecting jumper cable to your setup as is.
Ok both batteries are now connected in parallel with the jumper cables since this morning, will leave until tomorrow morning, then connect back up and test. I just checked now via watt meter, bought on Takealot that with 3 x Monitors, Desktop PC, router, Fibre box, I'm drawing max 260, see screenshot and according to the battery size calculator I should get 3 hours with 50% remaining.

So now question is, if after all this and I don't get 3 hours and only get say an hour or less, I'd assume the batteries I screwed or is it perhaps the inverter not charging, please advise what can I check after all is connected and fully charged?

And or how does one know if the battery is actually screwed, what can I check...is it something to do with how long it can hold a certain charge for (in volts) until it drops to a very low charge /volts as I also have other batteries I'm not using, checked voltage on them and one is just over 10 V and the other is just over 13 V?
 

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wingnut771

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Ok both batteries are now connected in parallel with the jumper cables since this morning, will leave until tomorrow morning, then connect back up and test. I just checked now via watt meter, bought on Takealot that with 3 x Monitors, Desktop PC, router, Fibre box, I'm drawing max 260, see screenshot and according to the battery size calculator I should get 3 hours with 50% remaining.

So now question is, if after all this and I don't get 3 hours and only get say an hour or less, I'd assume the batteries I screwed or is it perhaps the inverter not charging, please advise what can I check after all is connected and fully charged?

And or how does one know if the battery is actually screwed, what can I check...is it something to do with how long it can hold a certain charge for (in volts) until it drops to a very low charge /volts as I also have other batteries I'm not using, checked voltage on them and one is just over 10 V and the other is just over 13 V?
I'm just a layman but I would assume that if you get full voltage then the inverter is charging properly and if during the load test the voltage drops to 50% quicker than it should then I would say the batteries are poked. Only thing else to check in my mind are the cables. Are they warm? Keep them as short as possible. Are the connections good quality? Don't put a washer between lug and battery for example.

Also, bear in mind that the calculator doesn't factor in the power factor of the inverter and inefficiencies. Apparently the power factor is the difference between VA and W, so Mecer 2400VA is 1440W = 1440/2400=0.6 power factor so your 260W is actually taking (260/0.6) 433W in theory out of the battery. Some people say 0.6 power factor isn't accurate and should work on 0.8 instead.

Another thing to consider with lead acid is their discharge curves look like this:
1634387661370.png

So the best thing you can do is lower your load.
 

TheChamp

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Feb 26, 2011
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Ok both batteries are now connected in parallel with the jumper cables since this morning, will leave until tomorrow morning, then connect back up and test. I just checked now via watt meter, bought on Takealot that with 3 x Monitors, Desktop PC, router, Fibre box, I'm drawing max 260, see screenshot and according to the battery size calculator I should get 3 hours with 50% remaining.

So now question is, if after all this and I don't get 3 hours and only get say an hour or less, I'd assume the batteries I screwed or is it perhaps the inverter not charging, please advise what can I check after all is connected and fully charged?

And or how does one know if the battery is actually screwed, what can I check...is it something to do with how long it can hold a certain charge for (in volts) until it drops to a very low charge /volts as I also have other batteries I'm not using, checked voltage on them and one is just over 10 V and the other is just over 13 V?
Yes, it's mostly about how long it can hold a charge, some will show good voltage but fail under load.
 

RedViking

Nord of the South
Joined
Feb 23, 2012
Messages
41,820
Check those batteries mecernites. (<< that a word?) , Eskom is vibing with the government again. Stage 2 affair.
 

now05ster

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Dec 8, 2011
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2,058
Sadly our LS is only on midnight tonight for two hours. Then in the early morning hours on Monday.

EDIT: Wait, is that midnight today or tomorrow.
 
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