PeachParts Mercedes-Benz Forum - Why are NiMH batteries 1.2 volts?

PeachParts Mercedes-Benz Forum (http://www.peachparts.com/shopforum/index.php)

- Off-Topic Discussion (http://www.peachparts.com/shopforum/forumdisplay.php?f=16)

- - Why are NiMH batteries 1.2 volts? (http://www.peachparts.com/shopforum/showthread.php?t=206352)

Quote:

Originally Posted by OMEGAMAN (Post 1686807)

What is the maximum charging voltage with a 16 volt battery. I'm guessing you use 16 volts instead of 12 to start high compression engines?

The max charge is 16.9v. Their are many advantages in moving to a 16 volt system in racing applications. As for the starter, it cranks faster. Electric fuel pumps and coolant pumps turn faster. Most 12V systems will run at 16 volts thus farther from the drop off voltage. You also get a hotter spark from your MSD ignition. 16 volt systems are very popular in drag racing and NASCAR.

I like those 16v batteries. When you say "maximum charge" do you mean maximum input or output voltage? I would think the battery would actually have a 17.2v design voltage (8x2.2) and be charged with something like 18.5v or so. Are they re-charged in the car or do you have a separate charger?

I'm considering using one for my hobby turbine engine. All the components (fuel relay's , etc...) are 24v but they will run on 12. I'd like the 16v to run the starter and spin it up faster. I don't want to use 24v because of the weight and too, all the gauges and whatnot are 12v.

Quote:

Originally Posted by KarTek (Post 1687418)

I mean the output of a fully charged battery. Here are some typical 16V battery specs.

Number of cells........................8
Open Circuit Voltage...............16.9VDC
Length........................................10.3”
Height.........................................7.22”
Width...........................................6.4”
Weight.........................................33 lbs. (15 kg)
Terminals...................................3/8”-16 threaded
*Amp Hour Rating....................30Ah
16VDC Cranking Amps...........500A
**Reserve Capacity @ 25A.....50 min.
Max Charging Voltage.............19.0VDC

So your 18.5v charge voltage sounds correct. Some racers use 16V alternators some use chargers. A lot of drag racers won't add the alternator because of weight or drag on the engine. The 16 volt gives them plenty of time to stage, race and drive back to the pits before they get below 12V.

I'd be interested in knowing more about your turbine project. I dabble in that stuff too.
Adam

Quote:

Originally Posted by Whiskeydan (Post 1685939)

Has anyone heard the myth about setting car batterys on concrete? Old rumor says the need to be placed on a wood pallet otherwise they will be damaged.
I ask an oldtimer about this once. He said it was true when the battery cases were made of wood and had dovetail joints along the sides. The jolt of setting them on solid concrete would loosen the dovetail joint.

FWIW, C&D (or R&T, can't remember which) just addresses this in their tech questions... said it was pure bunk. They noted no ill-effects from storing a battery on concrete.

Quote:

Originally Posted by cmac2012 (Post 1686954)

I've noticed that the NiMH AA batts are not that much use in my digital camera. It will only use alkaline AA until they get down to about 1.4 volts, then it does the "Oopsie, closing down now" thingy. I then use the same batts in my little French made strap on miners' headlamp thingy. They fade out at around 1.2 volts.

Dang, I like my digital readout voltmeter.

The NiMH AAs last for a handful of shots in the camera before they're over the hill. Perhaps I'll use them in my headlamp only.

I gave up on all batteries except rechargeables for the camera shortly after I got my first digital. None of them were worth the money. Rechargeables are cheap, only way to go. On a recent trip a friend had some expensive batteries that were made for a camera, maybe lithium. I don't think they were rechargeable but they lasted a long time.

News from the 18v dewalt cordless tool arena, the new lithium batteries cannot be charged in the old chargers but the old batteries can be charged in the new charger. The new batteries will be compatible with the old tools.

Quote:

Originally Posted by cmac2012 (Post 1686954)

I then use the same batts in my little French made strap on miners' headlamp thingy. They fade out at around 1.2 volts..

Ah, a Petzl! You're official Eurotrash! :D

Just to make things interesting, the lithium-Ion battery in your cell phone produce 3.6V open circuit per cell.

The old Pretolites

Quote:

Originally Posted by Chas H (Post 1685963)

Old battery cases were from glass, not wood. Individual cells could be replaced by cutting the loose tar that sealed the top and swapping in a fresh set of plates.

in Model Ts were wood cases.

Quote:

Originally Posted by Kuan (Post 1685878)

Can anyone answer that for me?

chemistry. If you wanted to have a nickel battery deliver 1.5V it would need to be a different (larger) size. What is critical to its use is amp/hour rating (how much current it can deliver for how long.)

The older designs (zinc-acid) had different RED-OX reaction states. I can't recall the reaction right now but 33% of an electrical physics test in college was just that. It was a three question test that took and hour.