Electrical Question (different!)

[DGhost]

Ok... so... i'm working with something that has an approximately 24v internal power system, with the battery power being provided by two 12v batteries in series... I have a device that utilizes 12v power and was curious... if it is attached to a single battery (preferably the first in series), will it receive 12v of power even when the batteries are receiving power and recharging?

sorry if it is sketchy and poorly worded, it's been a while since I've done electronics/electrical systems...

thanks...

[LvR]

Yes it will, but you are going to have a problem and its this:

Because the 2 batts are in series, the same charging current passes through both the batteries.

Most chargers rely on the detection of voltage - so if the top batt for example is fully charged ito voltage levels, the bottom batt may still require some/a lot of charging to get it to a charged state - it will therefore dictate the sum of the voltages of the 2 batts in series, and because of this the top batt is going to get fried in the charging process.

[SitFlyer]

Yeah, it would be better to use a regulator to get your 12 volts from the 24 volt system

[DGhost]

well... the system itself is a pre-existing design and fairly reliable. I am not concerned about the batteries (the ones I am thinking using to splice off of are acctually redundant and in theory should never be used). as far as using a voltage regulator only problem is it would have to be capable of bumping out ~ 66Amps @12v to not be a limitation. simplicity wins out. the bad thing is that supposedly it will shutdown at around 16 +/- 1 Volts.

oh well, i know it has been done before. just wasn't sure about the specific voltage you would get if you connected it straight to one of the 12 Volt batteries while it is still in the 24v circuit.

[LvR]

it would have to be capable of bumping out ~ 66Amps @12v to not be a limitation.

In that case its definitely NOT the answer.

My guess is a dedicated switch-mode supply is going to be the answer - nothing simple there..................

[cjolley]

Exactly what kind of stereo are you planning to put in that Bradley?

[DGhost]

Originally posted by cjolley
Exactly what kind of stereo are you planning on putting in that Bradley?

lol, who said anything about a stereo?

[LvR]

Originally posted by DGhost
lol, who said anything about a stereo?

NO! - not another person with a 8 track and a valve-job in the car!

[DGhost]

rofl. it's all for the neon baby!

[DGhost]

strangely enough, it appears to have worked flawlessly. didn't get too much of a chance to test it though. mmm....

[Chrono_Wanderer]

maybe voltage divider?

[rylan]

up to 66A @ 12v? Dude thats almost 800w!
Anyway yes it should work, as you'd be drawing off the one 12v battery for whatever this thing is, while the rest of the system draws off the two batteries. The first one will drain faster however as its supplying more current.

[Chrono_Wanderer]

LOL didn't see the 66amps part. Nevermind what I said

[DGhost]

up to 66A @ 12v? Dude thats almost 800w!
Anyway yes it should work, as you'd be drawing off the one 12v battery for whatever this thing is, while the rest of the system draws off the two batteries. The first one will drain faster however as its supplying more current.

to clarify - the 66A is well beyond the load it is likely to incure, however it is inline with a max sustained load. if i were going to be attempting any additional power regulation circuitry (say, to enforce 12v) i would want it spec'd out to handle around that much. max load that i could ever see it drawing is half that, and even that is unlikely.

anyways, it's been a while since i went through electronics/electricity courses and i wasn't too positive. the only problem that i could see would be the fact the batteries also charge - and i was not too positive what it would do to the specific numbers. i am going to bet that if i were to find a reasonably heavy duty multimeter it would measure out as having a steady voltage but an increased current.

aaanywho. it seems to have worked fine. it will take more testing later to see for certain.