Old car battery

[LewisM]

Changed the battery on my car today - 4 years old and at peak recharge shows 11.63 V. It would recharge every drive but was getting bad.

Would this be ok for powering dewheaters, or not going to last the night?

[raymo]

At 11.63v it is certainly bu....ed for motoring use, but if you are looking
at powering a single dew heater for an 8" scope, or a couple of small ones for a 4" for example, it would probably last for an imaging or viewing session. I run my HEQ5, 1100D, and a single dew heater for my 8" Newt
with a worn out car battery. It lasts about 7.5-8 hrs, bearing in mind
that the HEQ5 is pretty power hungry.
Nothing to lose, anyway, so give it a go.
raymo

[ZeroID]

Be a bit careful with dying batteries. If one cell has degraded then when in use it will be sulfiding and putting out some nasty fumes, the kind that is not good for silvered or aluminised surfaces. If there is ANY sort of sharpish acidic smell coming from it get rid of it ... fast !!

[LewisM]

Thanks for the info guys.

Might try it and see. No acrid stench discernible as yet.

Tried recharging it over the weekend - now down to 11.3 V, and the charger would not progress past the CHARGING indicator, so yes, the battery is stoofed.

[raymo]

If your battery is stuffed, go down to your local auto electrics shop, and
see if they have an old battery that is still usable. They can load test it,
and will usually be happy to give it to you, as it's one less they have to
dispose of.
raymo

[ZeroID]

At 11.3 volts it is definitely 1 cell down. If you are going to use it keep it on a long lead away from your gear, 4-5 meters at least. The dud cell will sulfate when you put a load on the battery. If you've got some longish jumper leads use them to connect to reduce resistance back to the mount. Just run a couple of lighter gauge wires to the heater system for the last few meters. I've seen what fumes do to metal and it ain't pretty.

[ZeroID]

85 cents per kilo from the recycler over here Raymo, maybe he could swap them, dud for good and maybe a few beers. :thumbsup:

[raymo]

I use sealed car batteries, so corrosive fumes are not a problem.
raymo

[The_bluester]

Regards using an old car battery for heaters, the likes of the Kendrick controller cut off at above 12V so you would not be able to use one of them on it.

[raymo]

I don't use a controller, mine's connected directly to the battery. In many cases simple is good. I've never had a problem with
my power arrangements.
raymo

[LewisM]

It's being used as a garage door stop for now :) It is a sealed battery, so shouldn't be an issue - I replugged the over-flow vent.