question

rvreallydoingthis2 avatar image
rvreallydoingthis2 asked

Voltage drop - battery life

Fighting the South Florida heat!. I find myself solely relying on my solar system for weeks at a time. My system is a 24v system (components listed below) the battery bank was with 8 - 100 amp Battleborn batteries. My batteries would go from 100% charged at say 10pm and by 6am they would be down to 18-20% and the volts would drop low enough to shut they system down with a low battery alarm. (Just as the sun would start coming up) (yes, I am attempting to run 2 ac units to keep the 45 ft RV somewhat cool)

I figured adding a few more batteries would get me the extra time needed for the solar panels to start charging the batteries again. I added 2 more batteries, wired them in 2 seperate 12v strings of 5 batteries wired in parallel and then connected to the other string of 5 in Series to get the 24 volts needed. I was thinking that would be 1000 amp hrs.? (Which is what I changed the battery settings in my smartshunt too)

10-batteries.jpg

*Correct image updated

Now it seems I have plenty of battery life in the morning about 50% but my volts are now dropping off by morning enough for the multi-plus's to shut off with a low battery alarm.

I am hoping that I'm just not understanding something (or a lot) and I have a setting, or two, or three wrong.

Any educated assistance would be greatly appreciated I would also love to find someone on the southeast coast of Florida who could look at the system.


System:

2 - Victron Multiplus 24v/3000/70amp -- Split phase 180.

2 - Mppt 150/100/TR ve can.

10 - battle born 100 amp batteries. 2 seperate 12 volt strings of 5 batteries wired in parallel and then connected in series to make 24 volts.

8 - 330w solar panels (2640 W) wired series/parallel and broken down 2 arrays of 4 panels

Smartshunt 500A/50mV.

Cerbo GX with touch 50

Orion 24/12-70

Generator - Onan 5500

Auto transformer 120/240/100 amp

system designbattery capacityvoltage drop
10-batteries.jpg (53.8 KiB)
10-batteries.jpg (53.8 KiB)
1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

rvreallydoingthis2 avatar image rvreallydoingthis2 commented ·

10-batteries.pngOops, I actually attached the wrong image for the battery configuration. *correct image

0 Likes 0 ·
10-batteries.png (26.9 KiB)
3 Answers
mvas avatar image
mvas answered ·

1) Note: Your schematic diagram actually shows 10 batteries connected in series! Not the "2S5P" configuration that you stated. But I do understand that you have 2 battery banks wired in series, with each bank having 5 batteries wired in parallel = 24 Volts. Correct?

2) Can your Solar Panels actually produce enough Watts-Hours = ( watts x number of hours sun ) to run your daytime loads AND to fully recharge this larger battery bank?

3) You changed from a 24 volt x 400ah battery bank, to a 24 volt x 500ah battery bank. No, you do not have a 12 volt x 1,000ah battery bank

4) Is you new larger battery pack at 100% SOC at sunset? What is the final / highest charge voltage at sunset?

2 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

rvreallydoingthis2 avatar image rvreallydoingthis2 commented ·

Thank you for your response. I actually attached the wrong photo showing the battery wiring. I uploaded the correct one. To answer your questions. Yes, on most days I have no problem reaching 100% soc during the day before sunset. I reduce my load needs by only running 1 ac to keep the RV at about 82 degrees. If it's cloudy and I am not at 100% by sunset I run the generator for a bit to get me to 100%.

I would like to have solar take on more of the load and use the battery bank less but was leaving that question for another post. Lol

0 Likes 0 ·
mvas avatar image mvas rvreallydoingthis2 commented ·

1) What is the actual final / highest voltage at sunset, when your system "thinks" battery is at 100% SOC ?

2) What is your cut-off voltage? And what is the % SOC per the system.

3) Did you change your settings to 24v 500ah? ie not 1000ah

0 Likes 0 ·
klim8skeptic avatar image
klim8skeptic answered ·

@Rvreallydoingthis2 your 10 batteries gives 500Ah @ 24v.

4 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Alexandra avatar image Alexandra ♦ commented ·

Yes this ....

This is a common miscalculation.

You have 1000AH at 12v but 500Ah at 24v

12V x 1000ah is 12, 000wh or (12kWh)

24v x 500ah is 12, 000wh (12kWh)

So still the same energy stored, just at different system voltages.

The battery diagram is definitely incorrect.

0 Likes 0 ·
rvreallydoingthis2 avatar image rvreallydoingthis2 Alexandra ♦ commented ·
Thank you for your response. I realized I posted the wrong photo of my battery bank wiring. I uploaded the correct one.
0 Likes 0 ·
kevgermany avatar image kevgermany ♦♦ rvreallydoingthis2 commented ·
Maybe I'm missing something, but looks like 12V to me in the corrected diagram.
0 Likes 0 ·
mvas avatar image mvas kevgermany ♦♦ commented ·
Diagram looks like a 2S5P battery bank = 24 volts
0 Likes 0 ·
kevgermany avatar image
kevgermany answered ·

What is the power consumption of each AC, fridge etc.

Need to calculate total energy consumption overnight, then make sure the battery capacity is double that or higher.



2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Related Resources

Additional resources still need to be added for this topic