Loading one Battery in a Parallel Circuit
Loading one Battery in a Parallel Circuit
(OP)
I have what may seem like a dumb questions but I am going to ask anyway. If I have a parallel circuit with two 12v batteries. So positive and negative are connected on one side while the positive and negaive are delivering 24v from the remaining two terminals. If I install an item that draws 40 mA directly to one battery (12v) will this cause a problem if so what and why?






RE: Loading one Battery in a Parallel Circuit
Secondly, you shouldn't have a problem with a 40mA load hooked to one of those batteries. I would suggest you hook it across the lower battery. That's the one that has the cable running off to somewhere from it's negative terminal.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Loading one Battery in a Parallel Circuit
Bill
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"Why not the best?"
Jimmy Carter
RE: Loading one Battery in a Parallel Circuit
RE: Loading one Battery in a Parallel Circuit
I did this on a cross-counrty bus with a large 24V battery. We needed 12V to run the 1 kW inverter for the team's X-box, TV's and refrigerators. The inverter amp draw was more than I liked on the one battery so we rigged some voltmeters to monitor each battery's voltage and had a plug arrangement to swap the inverter between batteries safely every few hours. The bus engine alternator/charger could only sense and charge 24V so we had to watch the voltages and electrolyte levels to avoid overcharging one battery. It worked well enough to complete the 3 week trip.
In an old aluminum plant one switchgear lineup was 250VDC control and the newer one was 125 V. 20 years later, the two lead calcium battery banks were replaced with a single bank with a center tap for the 125V loads. Each half of the bank had it's own 125V charger. That worked well for another 15 years.
RE: Loading one Battery in a Parallel Circuit
That is IF that's what these are..
Keith Cress
kcress - http://www.flaminsystems.com
RE: Loading one Battery in a Parallel Circuit
RE: Loading one Battery in a Parallel Circuit
RE: Loading one Battery in a Parallel Circuit
You mentioned a battery isolator. Is this a manual disconnect? How sure are you that this is actually being used?
Are 24 volt transmitting hour meters available? Any chance of disconnecting it for a planned idle period as a test? Sometimes batteries self discharge at a greater than expected rate. In my experience, heavy equipment batteries do not usually give long service life. You may get better service from another brand.
RE: Loading one Battery in a Parallel Circuit
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Loading one Battery in a Parallel Circuit
RE: Loading one Battery in a Parallel Circuit
Further, the hour meter should be powered only when the equipment is running and charging.
If you want to leave an hour meter connected to a battery 24/7, you may do better with a calender.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Loading one Battery in a Parallel Circuit
I'd disconnect the fully charged batteries and insert your DMM set to DC amps. This is with nothing turned on of course. That will show you how much, if any, drain normally, or abnormally, is occurring. If you see something you can easily track it down with the ammeter in place.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Loading one Battery in a Parallel Circuit
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Loading one Battery in a Parallel Circuit
I'd never thought that placing the battery on concrete would damage it, but your explanation makes a lot more sense, and also explains the inference of concrete damaging batteries.
RE: Loading one Battery in a Parallel Circuit
We moved a couple of 8 Ds that were working well. They are heavy and awkward and had to be tipped to remove them from their normal positions and again to replace them. They were not dropped, but there were a couple of jolts against hard surfaces. From that day the two batteries would not hold a charge. If you have ever taken an old car battery apart you will be familiar with the layer of debris from the plates that accumulates in the bottom of the case.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Loading one Battery in a Parallel Circuit
As far as the hour meter being energized while the machine is off the hour meter part is not on just the radio which is listening for the data accumulator which is mounted on a roving vehicle. These devices are set to transmit once per hour then they sleep. Which draws approx 40mA.
Question, If an 8d is rated at 255 ah and you have two in series you should get 510ah of capacity correct? So if you have a draw of approx .340 amps or (340mA) that should give an approximate 100% discharge time of 62.5 days ((510/.340)/24).
Part 2 if the above is correct in order to discharge 20% or use approx 102 ah of capacity it should take approx 12.5 days ((102/.340)/24).
Does this reduction in capacity translate directly to a reduction in CCA? If a vehicle requires 800 CCA to start and you reduce the AH of a Battery System capable of producing 1000 CCA by 25% would you be left with approx 750 CCA of cranking power? Thus not being able to start the vehicle? I am just trying to fully understand the relationship between the AH and CCA.
Thanks
RE: Loading one Battery in a Parallel Circuit
No, it remains a 225 A/h system, albeit at a higher voltage. if you wish the higher A/h rating then the batteries need to be placed in parallel.
RE: Loading one Battery in a Parallel Circuit
Keith Cress
kcress - http://www.flaminsystems.com
RE: Loading one Battery in a Parallel Circuit
(Please see that when you divide 116 AH by 5, we get 116/5 = 23.2 amps, which is very close to the defined rate of discharge in RC, i.e. the number of minutes the battery is delivering 25 amps until the terminal voltage drops to 10.5V.)
I know that once, battery manufactures rate batteries on a 5-hour validation test period. Later, manufactures used 1-hour basis for simplicity in marketing. Other ratings basis are the 8-hour, 10-hour and 20-hour.
Since CCA is the amount of current that can be drawn from batteries (at 0 - minus 18 deg F) for 30 seconds before the battery voltage drops to 10.5 volts (for 12-volt batteries), dividing the approximated RC by 2 (two, thirty seconds in one minute) and adding a little ampere-hours to account for the non-linearity will give AH values very near the rated AH. Other automotive battery manufacturers just approximate AH = RC x 0.6. (AH = 200 x 0.6 = 114, in the example).
Still, I don't use these formulas and just brought these up here for people to comment.