can one battery charge another?

[Chris]

I don't yet have a charger for the small battery that come with an Aqua-Vu. They are cheap enough but time is a factor. I have a fully charged auto battery and was wondering if it would harm it if I connected it together for a while, at first I thoght this would be a nice gentle way to charge it but now I am wondering if it is in fact harsher than with a battery charger,..any ideas? I also have a 2 amp trickle charger but don't know if that is wise either. Not had any experience with these sealed batteries,.wouldn't like one to explode.

[Randy]

I am not familar with the battrey that is in the Aqua Vu, however, here are some facts:

Lead acid batteries, Gell cells, nicads and metal hydride batteries
are all different in charging requirements and cell voltage.

Assuming the Aqua Vu uses a deep cycle lead acid battery here are some
specific facts:

Two batteries of the same voltage will not charge one to another or
equalize there voltage.

You can ruin a battery by over charging, to much current for the size of the battery.

For more info go to this website:


http://www.marine-electronics.net/techarticle/battery_faq/b_faq.htm#4

Hope this helps!

[REW]

Yes and no,

All that a battery is - is a source of electrical voltage and current.

If one battery has a higher potential or voltage than the other battery, the voltage from the higher battery will flow to the battery with the lesser voltage.

In order to get a reasonable charge rate - or current flow, it is to the advantage of the battery charger - to have a potential or voltage greater than the highest potential voltage for the battery to be charged. i.e. if you are charging a typical 12 volt car battery - you generally use a voltage source of 14.4 volts.

A 12 volt lead acid battery is considered fully charged when it reaches 14.4 volts. thus, if you charge with a supply voltage (battery charger) of 14.4 volts - when the battery under charge rises to 14.4 volts, the charging current will fall to 0. Thus the battery doesn't get overcharged.

To directly answer your question - can you use a car battery to charge your little battery? Yes you can. However, it would be a good idea to put a .1 ohm resistor between the battery to limit the current, under the initial charge. If your little battery is quite low, it is possible to souce several hundred amps out of your car battery, and that might be explosive for your little battery. By using a .1 ohm resistor between the batteries, your initial charge current would be limited to a reasonable level.

Your final charge state of your little battery will be no better than, and no worse than, but in fact equal to the state of charge of your charging battery. However, because you are going to be charging with a 12.6 volt source, rather than a 14.4volt source - after the initial charge spike, your charging current is going to fall to a low level, and you might have to charge for a couple of days to get a full charge on your battery.

Take care

REW

[Chris]

Great answers, thanks guys!!!

[JCarp]

If your battery is a sealed 12 volt 7 AH you need a charger with the following specs: Plug-in Power Supply Class Two Transformer INPUT: 120VAC 60Hz 8.57W OUTPUT: 12VDC 500Ma. That's straight off the charger for a ZERCOM battery. I had an Aqua-view and compared chargers and batteries - the specs were identical. You do not want to exceed 500 milliamps (0.5 amps).

Reed's delivers fast. Gander Mt. has charger/batt combos for $20. Any battery store should be able to provide a charger. I'm 99% sure you can find motorcycle chargers at auto supply stores with identical specs for less than $15.00.

BTW - In case it's not obvious to you and weight isn't an issue - you can run the aqua-view off any 12 volt battery including your auto battery.

[Rickk]

Thank you also. I decided you wait and get a proper charger,...I have wondered though what happens to the gas that occurs in these batteries if you have a fast discharge/charge cycle? How can these be sealed? Don't all auto batteries have vents?

[JCarp]

This will address most of your questions. Jump to paragraph/Section 4.2.2., then 6.5 through 6.9.

www.marine-electronics.net/techarticle/battery_faq/b_faq.htm

Someone prev. posted it here and I thank them. It's titled Deep Cycle Frequently Asked Questions.