is it possible to pull 24V off of two 12v 7amp acid batts in series at the same time as pulling 12V 7 amps off each individual battery in the series?
I just dont want to fry anything.
Thanks
Yes, you can (sometimes called "center tapping").
However, does "7 amp" mean "7 A-h" (seven amp-hours)? If so, drawing 7 amps from each individual battery, plus whatever 24V draw you have, is a high rate for that battery capacity. Don't do it for very long.
A run of thumb for lead acid batteries is "C10", meaning the rate of charge or discharge for the entire capacity (7 A-h) over ten hours (0.7 amp). It is OK to exceed that rate for several seconds, or even a few minutes, but it degrades battery life. Also, in general one should not discharge below 50% full charge for good battery life.
Yes it is 7amp hours. I am using to run 7 solenoids @ 1 amp plus 7 shift brights with led satellites.
http://docs.macetech.com/doku.php/shiftbar
http://docs.macetech.com/doku.php/satellite_module_001
thanks for the reply
Well I tried to hook up the 7 solenoids and a shiftbright with one satellite. The solenoids run fine but the shift bright got fried. It should run fine between 5.5 and 17 V the battery was giving me 12.9V. Which BAtt is the upper battery? Can ou tell me if the shifbrights were plugged into the upper batt this would make it get fried?
The shiftbrights use up to 450 mAmp and the LED are a max of 1 amp.
All these are being triggered for only a brief second 80ms or so.
Heres the schematic for the batteries. the solenoids and the shift brights could be switched the other way though.
Thanks
ok sorry,
the solenoids use this circuit. There are 7 of these in parallel and are connected to the 24V out on the batteries. These pull 24V @ 1amp randomly for 80 ms each.
the shiftbars are wired like this and there are 7 of them. The Shiftbars can pull up to 450 mAmps and the LED modules can pull up to 1amp all with 12V. The first shiftbar was the one that fried.
Both circuits are being run off an arduino.
I dont have the circuit in front of me but taking a good look at the shiftbar diagram i showed you I realize that I had not terminated the last shiftbars + and - terminals by connecting them back to the power source. I had only connected the first shiftbar to the power source.
Could this be why Im frying the shiftbar. Please explain .... why does this happen?
also what would the voltage be if I drew power from these terminal?
thanks
I can't see how. That would "starve" the boards with not enough power, not fry them.
But that is how the circuit is shown in this diagram. I got this off the manufacturers website.
U R Awesome thanks!!!!
big ups dood. This is exactly what I had. The problem I think happened when I tried to run 12v from the two different sides into the 12v LED array. Oops.
I understand now... I thought that both 12V batteries, when connected in series, could also supply 12V. Ive been pulling 12V out of the first battery in the series and I guess this is why I fried the shiftbar.
Can you explain to me why, then, does my multimeter read 14V when hooked up to the first battery in the series if its not actauly supposed to give me anything?
thanks again.
Great know iknow. Thanks all for the help u rok.
Could you charge this setup through the lower battery's + and - with a 12V charger?
What do you mean by a big 4 pole connector? Can I see an example?
I have a question about voltage drop for the setup.
Using 24V batteries and 6AWG wire the voltage drop over 30 feet while pulling up to 4 - 5 amps would be about .19 V. When I test the battery, the voltage is 25.5 V and we are using 24V solenoids so that voltage drop should be fine, yes?
Also I have to come off the circuit with 22 AWG for about a half foot then switch to 6AWG. How is this going to effect the voltage drop?
ok so after actually thinking about the setup a bit I have figured that I will actually be pulling about 2.5 amps not 4-5 amps. Below is a drawing of the setup. Basically there will be a power station at the bottom of a tree. The solenoid and led will be at the top of the tree which will both be driven by an arduino at the bottom of the tree. The thing is is that the terminals coming of the arduino shield I have made are not big enough for a 6AWG in need to prevent the Voltage from dropping too much. So I was hoping to switch from the the 22AWG I currently have to a 6AWG to provide power up the tree 30 feet.
Are you saying that its the weakest link because it may not be able to handle the Amps or because it will increase the voltage drop too much even if it just used for a half foot.
yes AND yes. What's the point of having the Alaska Pipeline if you can only feed it through a garden hose?
Putting the transistors up near the end of the circuit is not an option. Im using TIP122's, 7 of them in parallel with each solenoid triggered by a single transistor. So each solenoid (thus each line only handles 2.5 Amps) will be pulling about 2.5 amps @ 24V for only about 80 millseconds. I want to use the 6 guage just so I jet as little voltage drop over the 30 feet as possible not because thats what the amperage demands.
So I dont think amperage is the issue here I think the voltage drop over 30 feet of 22 gauge will be too much and I will not be able to power it properly. Therefore, I have to step up the wire to 6 gauge.
Question: Does it take more amps to go over long distance or just voltage?