Free portable 12V power supply.

[mikerr (Michael)]

There have been a lot of posts lately about powering dew heaters, drives, hairdryers etc in the field.
For years I have used second hand car, tractor and four wheel drive batteries. These may be obtained free of charge from your local Auto battery Dealer as they have to pay to get rid of them and that charge has already been passed on to the previous owner of the battery.
When an Auto battery will no longer reliably turn over the starter motor to start a vehicle it gets replaced. This does not mean that the battery is useless or has no capacity left in it. It just can’t supply the required huge “Cold Cranking Amps” (CCA) necessary to start an engine, which is the toughest job it has to perform.
The capacity that still remains can certainly run all your accessories for probably days at a time and then can be recharged again, with a low cost car battery charger from Super Cheap Auto or similar.
The more modern/common “Maintenance Free” batteries are best as they do not usually spill if tipped over. Simply give the outside of the battery a good wash with mild soapy water, rinse, allow to dry and you have a new power supply for free.
The bigger the battery the longer it will provide power in one session, but they also become heavy to carry. Try to pick one with inbuilt handles.
Jaycar and others sell an adaptor which has two alligator clips on one end and a car type cigarette lighter socket on the other. You can also build a box for the battery and add whichever sockets, fuses and switches take your fancy.
I hope this information proves useful if it has not already been discussed previously.

Michael

[IanT]

Michael
I like your thinking.
Thanks
Ian

[mswhin63 (Malcolm)]

Not bad, never thought of the internal resistance failing before capacity is lost. Weight and gassing is the only concern but as long as it is not charged inside the car should be fine. Would have to be careful that the old battery hasn't sulphated up too much though, this may restrict some of the benefits.

Nicely thought of

[mikerr (Michael)]

Thanks Ian. Malcom, most of the batteries I see now use the newer Calcium additive technology which greatly reduces the sulphation problem. Internal Resistance, as you say, reduces the Cold Cranking Amps (CCA) capability.

The good thing is that you can always just grab a couple more if one does not perform as you wish.

Always remember to remove the charger once the battery is fully charged. Very few chargers have the smarts to properly maintain a battery if left connected, without overcharging and destroying the battery.

Michael

[mithrandir (Andrew)]

The usual reason I've had to replace batteries is a dead cell. You'll need to check that is not the reason it got replaced.

Calcium batteries need a Calcium/GEL charger. The older lead acid chargers will not bring them up to full voltage.

[mswhin63 (Malcolm)]

I generally found the problem with batteries is cold cranking, never had a dead cell. I will remember to keep them in the future.

[oosh (Jason)]

What a great idea! Thanks Mike!

[tonycynic]

Solar panel charger for the day, never need to leave the site.