Battery life and brightness should be about the same either way.

 

Battery life will be longer with a 24v setup. The more amps you draw the lower the reserve capacity.

 

I'm gonna go with OBG on this one.

 

That is what I was thinking OBG. Thanks for confirmation.

 

Only real advantage to running 24v is it allows you to use smaller gauge wire

 

I think this is the chart OBG posted on a similar thread after a similar statement.

 

It gets tricky because discharge rate affects battery reserve capacity. The reason I think run time will be the same is because there are 2 batteries involved in this case and discharge rate per battery will be the same 12 or 24.

 

Yes it is tricky, and yea the batteries will share load, but paralleling makes them one cell and will not be even so to speak. I think that was the chart you posted, no big deal. It just there are distinct advantages to going 24v over 12v.
As he stated paralleling 2 batts vs 2 batts for 24 v, the 24v has half the amp draw, and the parallel batteries have twice the capacity. If you look at the 31 series on the chart. An amp draw of 20a (the 12v hypothetical) has a minute capacity of 299 min, at 10 amps(24v hypo) it has a min rating of 704 minutes.
299 x 2 batteries =598
704(2 in series capacity = 1 batteries rating)=704

Now you could take half the LED and put on one 12v batt and the other half separate on that battery and get about the same discharge time, but not as the OP asked.

 

I still have to go with the same run time since there are 2 batteries involved-I'm thinking discharge rate per battery will be the same?

 

Hopefully they discharge the same, but if one of the battery circuits has a bit more wire connecting it, that slighty changes that circuits resistance...regardless the 12v is still pulling twice the amps from the all the cells of the battery, parallel or not, its the increase in amps that lowers capacity not how much capacity is available.

 

:cf:
ok, sorunning a series 12 you say will last longer. if im going to run two sets of 24v batteries, should I run a 24v system that is using 4 batteries, will this make my setup run better than running two 24v systems with only 2 batteries each. which would be bette. Mike

 

I run my four batteries together at 24v. Didn't figure lights without troller or vice versa would do me much good.

 

Ive run mine 12 and 24 and saw no difference in run time or brightness. I think go with the bigger wire run 12 instead of 24 and use the 2 batteries hooked together for a single cell 12 volt and get more run time jmo.

 

I still have to go with no difference-it's the same lights using the same amount of current from the same 2 batteries

 

I see what you are saying and it makes sense but it doesn't jibe with the chart....

The chart is clearly stating an increased battery efficiency at lower amp rating. If thats the case, there is a clear advantage to running at 24V. Taking the 10A vs. 20A as an example, across the board the time listed is approx 215% [at 10a vs 20a] instead of 2x or 200%. I don't know enough about how all this works to question the charts and how accurate they are.......I assume they test this?

 

Its not the same amount of current, its the same watts used.

 

I probably should have said it's the same lights using the same amount of electricity from the same two batteries.

 

Yes same light same amount of power consumed, but at 12v you are pulling twice the amps, which will lower the reserve capacity of a battery. The "harder" the acid and lead reaction happens the greater the losses, losses like you see in converters/inverters, or like when you jump on the gas your MPG goes down.
This relationship between 24v vs. 12v we are talkin about here is why we use 120 volts AC in our houses. Cause it'd take a 100 amps of 12v to run your toaster every morning.
I realize OBG we have crossed swords in the past, I apologize, and wish to no longer continue with that, it helps no one.
good day

 

Ok please don't crusify me for this. I have worked in industral industry for a long time. On AC(i understand it isn't the same as DC) you can take a 5hp motor running on 110volts and its drawing approx 12 amps now remove that motor and put one that is 220 volt and it draws only around 6 amps(witch is more efficent) and you lower the amount of kilowatts per hr used. It would seem that if you run the same light at 24 volts it would be more efficent and draw less power. If this isn't the case then why would these light be made for 24 volts?(you can't buy 24 volt batteries that i know of) Anyway what mkes DC voltage different that it doesn't give a longer run time on 24 volts vs 12, or are you limited by the batteries compasity?

 

I don't see a difference in efficiency between 12 amps @ 120 volts and 6 amps @ 240 volts. Seems like they both are equal to 1440 watts. Not saying that a 240 volt motor can't be more efficient than a 120 volt motor just that in the particular instance you mentioned power consumption is the same.

Yes same light same amount of power consumed, but at 12v you are pulling twice the amps, which will lower the reserve capacity of a battery. The "harder" the acid and lead reaction happens the greater the losses, losses like you see in converters/inverters, or like when you jump on the gas your MPG goes down.
This relationship between 24v vs. 12v we are talkin about here is why we use 120 volts AC in our houses. Cause it'd take a 100 amps of 12v to run your toaster every morning.
I realize OBG we have crossed swords in the past, I apologize, and wish to no longer continue with that, it helps no one.
good day

Ain't no biggie and I'm not trying to argue about it. Two minds are always better than one when it comes to figuring stuff out. I understand about discharge rate effecting run time. My point is that in a two battery system running the same load, discharge rate per battery will be the same whether the load is 12 or 24 volt. It just doesn't add up any other way. If I had a d/c led I would clamp 2 batteries and run it both ways just for grins but I only have a 100 watt a/c led which is no use in this case.

 

Ok i see the wattage is the same i was thinkin amperage is what you went by not watts. since you go by watts why would you even go thru the trouble to rig a 24 volt set up?

 

Here's a good reason stated above:

Only real advantage to running 24v is it allows you to use smaller gauge wire

 

I'm no expert by far,ain't pretendin to be either,with 10
27w lites there was no noticable diff. Between 12 or 24 v.
With 15 lites,24 v mo better,period.
Prolly cuz I skimped and tied in too many lites on too small a
wire. Anyway I go 24 volt now.
Silent bowfishing is the shiat!

 

We are talking apples and oranges here. The reason for your issue is you put too many watts on that size wire at the lower voltage, this has nothing to do with battery capacity at different voltages. Nice to hear confirmation of you liking those LEDS since I have some comin....sweet


I appreciate the commentary OBG and Istickem.

It appears Stickems MPG example is exactly what the battery amp chart shows, so it makes sense to keep your amp draw as low as possible so you can pick up another 15-20% efficiency [or call it slightly longer run time]

Personally, I'm still running a size or two larger on the wire dia because I know when the bigger badder lights come out I won't want to rewire the whole mess.......

 

I though that that running the batteries in parallel essentially doubled you capacity. If that is the case, you double your AH rating which should give you more run time. Correct? So 24 would be better than 12 for run time.

 

series doubles voltage, capacity stays the same.

parallel doubles capacity, voltage stays the same.

 

Except when you pull 20 amps from 2 batteries in parallel the current doesnt stop and say hey you 10 amps come from this battery and us 10 amps will come from that battery. They both produce 20 amps, and the chemical reaction in the batteries that achieves this IS what lowers reserve capacity.
It has nothing to do with discharge rate and everything to do with amp draw.
Also if you parallel 2 batteries, and your feeder wire comes off one battery post and that jumper leads to the other battery, the battery with extra wiring from the load will have a higher resistance and it WILL draw less amps changing the discharge ratebetween the 2 batteries. Its physics.

 

Let's pleasantly agree to disagree on this one.lol

 

I will also note that one can not "see" a difference, LEDs will run until the driver hits low voltage shutoff. Batteries are notoriously inconsistent. This is kinda like comparing optics, there really is no measurable trait to really prove a case but we know the euro optics are best. This is also why you see such different values used by battery manyf, CCA,MCA, amp hours, reserve capacity, etc etc.

 

I'm not seeing wiring length from battery to load on 2 batteries in parallel being any different than 2 batteries in series.

 

If the wire lengths are the same and one leg goes to one battery and the other leg to other batt yea it will even out, but Id bet very few wire it that way, not to mention the internal resistance of two batteries is highly unlikely to be the same causing different discharge rates.
Look at the chart it lists a 185HC battery, its got about twice the capacity as a 31 series, so in effect same as 2 31 batteries in parallel. Notice it still has a much lower reserve capacity when the amps are doubled.
Same capacity as this example of 2 batts in parallel.

 

"If the wire lengths are the same and one leg goes to one battery and the other leg to other batt yea it will even out, but Id bet very few wire it that way, not to mention the internal resistance of two batteries is highly unlikely to be the same causing different discharge rates."
This is true and will be true whether it's wired in series or parallel.

 

I absolutely agree with the chart in that a battery will not last as long at a higher discharge rate as it will at a lower discharge rate.

 

This is great info guys! keep it coming. I have my LED's on 24volts. and I was wondering the same thing.

 

Okay. dumb question. Do these lights come equipped to switch from 12v to 24 volt, or do I need to decide to buy 12v or 24v before I buy them