24v battery bank vs 12v

[Jacotenente]

I currently have my solar set up with six, deep cycle marine batteries wired in parallel (12v). The Kid (at max output) puts out 30 amps/around 430 watts in my configuration.

What are the benefits of wiring my batteries to a 24v system?

My inverter is a 12v PowerBright 3500 watt...would need to change that out also.

Thanks.

[xsnrg]

depending on your PV array, you may want to go 48v, using the 4 best batteries in a series string.  This would move you from 6 in parallel, which is a pretty tough setup to having 4 in series, which is easier to manage.  You are already looking at swapping out the inverter anyway.

Gains from going to 48v (or any higher voltage) are: 

Less power loss in the wires due to voltage drop:
* smaller wires can be used. 
* due to less amperage for the same watts

Ability to handle more wattage with the KID:
* 30 Amps is max at 12v, but is also max at 24v and 48v.  That is, 48v nominal * 30 amps = 1440 watts that the KID can handle
* If you have less than 1400w of panels, the KID will run cooler as it will be handling less than 30 amps

This all depends on your solar array.  You will want an array 70v or greater to be able to eq your bank with a 48v bank, so you might have to do some re-configuring there too. 

[Jacotenente]

Thanks. I am running 10 Renogy 100D panels (1KW). I have them wired series-series-parallel (60v) system. Two strings of five panels. I have found that the Kid seems to "like" higher voltages. Open circuit (Kid turned off) solar panel voltage is about 109v with these 10 panels. With the Kid on, it varies from 72-100v when operating with the sun. Pretty happy "over-paneling" this Kid...if that is what it is called. The positioning of my panels is not ideal and there is shade (see pic). However, due to HOA guidelines, codes, and "prying eyes" I had to mount them on my backyard pergola.

A lot of people I talked with who have experience with the Kid, Classic, Classic Lite, and others (and who have seen my You Tube videos) say they rewired their battery banks to 24v and really think it helped. As for the inverter...yep, need to go to a "pure sine wave" at 24v input. The one I have installed is a beast at 3500w and works great...but, kinda overkill.

Just thought I would drop this forum a line for everyone's thoughts.

Thanks again.

[kf4hzu]

Hi Jacotenente!

I'm relatively new here too, but thought I'd comment since I am also using the same Renogy 100W panels.

I run a 12V battery system and it seems to work well. Everything that has been said about higher voltage battery systems is true, but I picked 12V because I have so many 12V devices, connectors, etc that it works best for my needs.

One comment I'd make; the shading of that tree is going to hurt your entire array if it is in series (I think it is). If you can't trim back the tree to eliminate the shading I would change the array design to reduce the impact of the shading. Edit: Not sure how to improve it. Maybe someone more knowledgeable can suggest something if trimming the tree isn't possible.

I'm still new and learning, so do some more research, but I know trees in my yard shade my array in the early morning and evening causing a significant voltage drop which reduces overall power generation to almost useless.

[vtmaps]

I run a 12V battery system and it seems to work well.

Huh?  Then, what's all this about?
http://midniteforum.com/index.php?topic=2310.msg21789#msg21789

I think some of your problems stem from your choice of a 12 volt system, and that you would be better off reconfiguring into a 24 volt system.

--vtMaps

[Jacotenente]

Thanks all. Appreciate it.

1. As for the shading of the trees. Yep, they are going to get trimmed
2. 24v battery bank/inverter - Yep, that needs to happen
3. Utilized the Midnite Solar Classic Sizing Chart (see attachment). Looks like a Classic 150 would better suit my needs
4. Also worked with Midnite Solar to get a baby breaker box and correct breakers.
5. PV current at max is lower with two strings of five (10 panels total). Feeder cable run acceptable w/n limits

[xsnrg]

Hmm, seems to be a few parallel threads saying the same things, but to summarize, if you are staying 12v then yes, a classic would be a better fit, if you are going to re-configure your battery bank, then the KID still fits with your array.  Higher voltage means the KID handles more wattage, and you can use appropriately smaller wiring.

[Westbranch]

So going back a bit , you mentioned 12V Stuff that needs 12V.  Is that going to change or  do you still need a 12v source?  There are a few different ways of doing that...

[Jacotenente]

Westbranch - Not really needing a 12v source...just practical with my old 120v A/C - D/C charger. Looking like the Classic 150 will be first on my list...then working on the battery bank/inverter to 24v.

Chris

[kf4hzu]

Huh?  Then, what's all this about?
http://midniteforum.com/index.php?topic=2310.msg21789#msg21789

I think some of your problems stem from your choice of a 12 volt system, and that you would be better off reconfiguring into a 24 volt system.

My problems are not due to the voltage of the battery bank but the design (4 12V AGM in parallel). I won't be switching to a 24V system, but when I do buy new batteries they will be 4V or 6V (or 3.2V LiFePO4!) in series to significantly reduce the balance issues I have now.

This is the wrong thread to discuss this anyway.