Powering lights a long distance from a battery bank?

[mwatson]

Hey guys, I've been using a few 115 Ah deep cycle batteries to power various 12v LED lights and 12v fans in a fairly spread out area (150'x150' square). In the past I've been using a Honda eu2000i to charge them as they deplete, but I'd love to figure out a good solar solution that would allow me to charge the batteries during the day so I can run the lights for 6-10 hours each night.

I've been trying to figure out how to distribute the power to the various places I need. Currently I disconnect the batteries and move them to the generator as needed, and I thought I could continue to do this with solar but removing the need to move them would be even better. I know a 12v system wouldn't work for long distances as the voltage drop would be too high at a distance of 50-100', is there a recommended way to power 12v devices off of 48v? Am I better off just moving the batteries?

Am I right in thinking that using four 115Ah 12v batteries in series would reduce their capacity to 115 Ah at 48v?

The lights and fans I'm using are about 260w total, so my demand at a minimum would be 1560-2600w per night. The panels will be used in a desert area so exposure should be good for most of the day (8-10 hours).

Thanks in advance!

[lkruper]

Hey guys, I've been using a few 115 Ah deep cycle batteries to power various 12v LED lights and 12v fans in a fairly spread out area (150'x150' square). In the past I've been using a Honda eu2000i to charge them as they deplete, but I'd love to figure out a good solar solution that would allow me to charge the batteries during the day so I can run the lights for 6-10 hours each night.

I've been trying to figure out how to distribute the power to the various places I need. Currently I disconnect the batteries and move them to the generator as needed, and I thought I could continue to do this with solar but removing the need to move them would be even better. I know a 12v system wouldn't work for long distances as the voltage drop would be too high at a distance of 50-100', is there a recommended way to power 12v devices off of 48v? Am I better off just moving the batteries?

Am I right in thinking that using four 115Ah 12v batteries in series would reduce their capacity to 115 Ah at 48v?

The lights and fans I'm using are about 260w total, so my demand at a minimum would be 1560-2600w per night. The panels will be used in a desert area so exposure should be good for most of the day (8-10 hours).

Thanks in advance!

You can go 100 feet with a large enough wire. There are tables for this. What is the watts at 12v for one leg for how many feet?

[mwatson]

Rough draws per wire:

• 6 12v LED strands @ 30w each (180w) - 100'
• 1 12v LED strand @ 30w (30w) - 120'
• 1 12v LED strand @ 30w (30w) - 120'
• 3 12v LED bulbs @ 3w (9w) - 60'

I could potentially run one larger wire to a central point (the 6 12v strands) and then run a few smaller wires from that point to the other lights if that would help reduce cost some.

Currently the solar panels can't move much closer to the lights, but I'll see if I can reduce the distance a bit. What type of wire and plugs are typically used with DC voltages over that distance?

[lkruper]

Rough draws per wire:

• 6 12v LED strands @ 30w each (180w) - 100'
• 1 12v LED strand @ 30w (30w) - 120'
• 1 12v LED strand @ 30w (30w) - 120'
• 3 12v LED bulbs @ 3w (9w) - 60'

I could potentially run one larger wire to a central point (the 6 12v strands) and then run a few smaller wires from that point to the other lights if that would help reduce cost some.

Currently the solar panels can't move much closer to the lights, but I'll see if I can reduce the distance a bit. What type of wire and plugs are typically used with DC voltages over that distance?

Here is one table: http://www.solar-electric.com/wire-loss-tables.html

If you convert 30w to amps @ 12v, you get 2.5 amps. You can transmit 4 amps 133 feet with #6 wire.

[Sunking]

If you convert 30w to amps @ 12v, you get 2.5 amps. You can transmit 4 amps 133 feet with #6 wire.

That would require 270 feet of wire that cost 80 to 90-cents per foot.

The answer is higher voltage, or much lower power. Take your pick.

[Mike90250]

Rough draws per wire:

• 6 12v LED strands @ 30w each (180w) - 100'
• 1 12v LED strand @ 30w (30w) - 120'
• 1 12v LED strand @ 30w (30w) - 120'
• 3 12v LED bulbs @ 3w (9w) - 60'

I could potentially run one larger wire to a central point (the 6 12v strands) and then run a few smaller wires from that point to the other lights if that would help reduce cost some.

Currently the solar panels can't move much closer to the lights, but I'll see if I can reduce the distance a bit. What type of wire and plugs are typically used with DC voltages over that distance?

180w @ 12V = 15a 100' x2 = 200'
My spreadsheet shows:
Total Resistance
AWG Feet Ohms Panel (Volts)
6 200 0.079365 12
(Amps) Voltage drop Voltage drop %
15.00 1.19047 9.9%
#6 may work, but it will be costly

Am I right in thinking that using four 115Ah 12v batteries in series would reduce their capacity to 115 Ah at 48v?

Not reduce but the amps don't change. Still 115ah
Batteries in SERIES, voltage adds, amps stay the same
Batteries in PARALLEL, volts stay the same, an amps add

[SunEagle]

Besides needing larger wire to run dc voltage to power your loads your batteries are too small to maintain that 1.56 to 2.6 kWh daily.

The best a 12volt 460Ah or 48v 115Ah system can produce at 100% DOD is 5.5kWh.

If you need to run 2.6kWh then you have to increase you battery system and if you still want to run DC a long distance then go with a 48volt 230Ah system using 8 x 6v 230Ah batteries.

To charge them you are going to need 800 - 1000 watts of solar pv and a 30Amp MPPT CC for that 48volt battery bank.

Then get a 48volt to 12volt DC to DC power supply and put it as close to your 12volt loads as possible.

Oh and keep the generator in case you run into a couple of days without sunshine.

[mwatson]

Thanks for the responses that helps a lot. Could I run two sets of four 12v batteries in series in parallel to get 230Ah at 48v instead of the 8x 6v?

Any suggestions on where to buy batteries? Am I putting myself at risk if I buy cheaper ones?

[SunEagle]

Thanks for the responses that helps a lot. Could I run two sets of four 12v batteries in series in parallel to get 230Ah at 48v instead of the 8x 6v?

Any suggestions on where to buy batteries? Am I putting myself at risk if I buy cheaper ones?

You can build a 48volt 230Ah battery system out of 8 12volt 115Ah batteries but first; each of them will be very heavy and hard to move around and second; any time you wire batteries in parallel you increase the chances of not discharging or charging them equally which tends to push one or two batteries to an early death. The best way to build a large Ah rated system is to use lower voltage high Ah rated batteries and wire them all in series.

For your first set you can try using Interstate which make a 6volt 232Ah battery but while they are labeled deep cycle they really do not have the lifespan and cycle count of true deep cycle like a Trojan.

Again you can go cheap but as they say you get what you pay for. In the case of someones first battery system I actually encourage them to not go with the most expensive because the chances are pretty high the first set will be ruined during the learning curve.

[mwatson]

You can build a 48volt 230Ah battery system out of 8 12volt 115Ah batteries but first; each of them will be very heavy and hard to move around and second; any time you wire batteries in parallel you increase the chances of not discharging or charging them equally which tends to push one or two batteries to an early death. The best way to build a large Ah rated system is to use lower voltage high Ah rated batteries and wire them all in series.

For your first set you can try using Interstate which make a 6volt 232Ah battery but while they are labeled deep cycle they really do not have the lifespan and cycle count of true deep cycle like a Trojan.

Again you can go cheap but as they say you get what you pay for. In the case of someones first battery system I actually encourage them to not go with the most expensive because the chances are pretty high the first set will be ruined during the learning curve.

Thanks for the info SunEagle, that helps a lot. That would mean if I want to upgrade my battery bank in future I'd likely have to replace all of the 6v batteries with a higher ah down the road correct?

It's sounding like this may be a bit out of my immediate budget, but definitely a project I can work on over the next year. If I'm willing to charge the batteries individually using an mppt cc that can handle 48v to 12v would it be alright to use two 300w panels and swap my current 12v 115ah batteries out as they reach full charge? I think this would be the cheapest option for me to get some benefit from solar without the high upfront battery costs.

[SunEagle]

Thanks for the info SunEagle, that helps a lot. That would mean if I want to upgrade my battery bank in future I'd likely have to replace all of the 6v batteries with a higher ah down the road correct?

It's sounding like this may be a bit out of my immediate budget, but definitely a project I can work on over the next year. If I'm willing to charge the batteries individually using an mppt cc that can handle 48v to 12v would it be alright to use two 300w panels and swap my current 12v 115ah batteries out as they reach full charge? I think this would be the cheapest option for me to get some benefit from solar without the high upfront battery costs.

Using solar panels and a CC to individually charge a "small set" of batteries to be swapped for the "next set" usually takes a lot of time and results in not getting all of the batteries equally charged. Even if you have multiple panel/charger/battery sets you won't be able to get all of the batteries up to the same level.

You also have to size the charging amps from the panels to the Ah of the battery system so that you are around c/10 or using 1/10th the of battery Ah rating to charge.

Then there is a big chance that all of them batteries will not be truly "equal" in voltage and can cause sparks when you try to recombine them into one system.

Each cell of each battery in the system needs to be charged and discharged equally at the same time. If not then you start to over or under charge individual cells and batteries creating a "weak" link in the system. Resulting in an earlier death than anticipated.

I wish it was easier or less costly but using and maintaining batteries is expensive and high maintenance if you do not know what you are doing.

A solar/battery system need to have every part properly sized and matched for the daily needs. Once you have the system you can't add to it without getting a total new set of batteries.

[mwatson]

Would I have an issue if I treated each battery as its own system?

Currently I use the batteries in isolation (one 12v battery powers one area of LEDs) and then recharge them when they get near 50% with a generator. I agree it would be a lot of work to constantly swap batteries out from the charge controller, but it sounds like I could avoid the equal charging issue if I only ever have one battery connected at once. I know this isn't the best way to go about solar, but it's sounding like I'm going to need new batteries when I move to a proper battery bank anyways.

Really appreciate your help, other people I've talked to about this have said "that should be fine", but it's much more beneficial to understand the damage I could potentially be doing to the batteries. Thanks!

[SunEagle]

Would I have an issue if I treated each battery as its own system?

Currently I use the batteries in isolation (one 12v battery powers one area of LEDs) and then recharge them when they get near 50% with a generator. I agree it would be a lot of work to constantly swap batteries out from the charge controller, but it sounds like I could avoid the equal charging issue if I only ever have one battery connected at once. I know this isn't the best way to go about solar, but it's sounding like I'm going to need new batteries when I move to a proper battery bank anyways.

Really appreciate your help, other people I've talked to about this have said "that should be fine", but it's much more beneficial to understand the damage I could potentially be doing to the batteries. Thanks!

You can build individual systems that contain a battery, charge controller and solar panel. You just have to match them up so that you get enough charging amps our of the panel/cc to get the battery back to 100% SOC each day. You also need to make sure you do charge the battery too quickly because that can hurt them. So pay attention to what the battery manufacturer recommends in charging/discharging speeds.

For example; a 12volt 115Ah FLA battery with a C/10 charge rate will need about 11 amps of charging. You can get that from 2 x 100 watt panels with a Imp = 5.5amps wired in parallel to a PWM 15amp CC.

But it still depends on the equipment you have (solar panel, CC, battery) and how much "usable" sunlight you during one day.