Trickle charger .... from 12V to 6 volts ???

I have a tiny little motorbike battery here, only about 3x3x4" in size and it is a 6 volt battery with a 2 amp rating. I have three questions ...

1) Would an automotive battery charger for 6 volt 2 amps be too much for this little battery? Maybe OK if a guy only charged it for a short while?

2) I do have a 12 V trickle charger of 1 amp. Is there any way I can step the voltage down to 6V without changing the amperage output of the charger too much?

3) What sort of voltage should this little battery show when sitting at rest for say a day after charging?

Question #1: An automotive charger would work if it is regulated and will not over-charge. Watch it carefully!
Question #2: Do not us a 12 volt charger. You'll smoke the battery.
Question #3: A six volt battery fully charged will voltage test with a meter at about 6.3 volts.

The thing to understand about conventional battery chargers is they really aren't voltage regulated. They rely on the battery itself to limit the voltage. So if you hook any conventional charger to a battery long enough you'll overcharge the battery. And of course the smaller the battery the shorter the time before it's overcharged.

Your "2 amp" battery is actually a 2 ampere-HOUR battery. Meaning that fully charged it can theoretically source one amp for about two hours. (Actually not, but let's not go down that rabbit hole.) So, it's probably safe to charge it with your six volt 2 amp charger as long as you don't leave it on the charger for too long. A couple of hours is probably fine, but leave it charging overnight it's likely to get overcharged. The safest way is to monitor the battery voltage with a meter and take it off the charger once the battery gets up around 7 volts (while under charge).

There's no simple way to drop the voltage of your 12 volt trickle charger. If you install a resistor in series with the battery, it will drop the voltage but as the battery's charge increases the voltage drop across the resistor will fall, which is exactly what you don't want. You could put a 7 volt zener diode in series with the battery, but you'd need a zener capable of dissipating about 7 watts. (The <a href="https://www.ebay.com/itm/10-PCS-1N5342BRLG-1N5342B-1N5342-5-Watt-6-8V-Zener-Voltage-Refulators-Diodes-/291868103564">1N5342 zener diode</a> is a 6.8 volt, 5 watt zener; give it a shot and let us know how it worked.)

I have a 50 year old Shumaker with 1 amp setting, seems to work fine.

I use a little six volt battery on one of my trail cameras. What I did was look around and found one of my old chargers from a old rechargeable drill or phone or whatever. Many different voltages on those chargers but happened to have a six volt that delivers a few millamps and I use that. It is slow but gets the job done to over 7 volts in a day or so. Have been using two batteries, rotate them, for at least three years now.

Good questions:

1) Would an automotive battery charger for 6 volt 2 amps be too much for this little battery? Maybe OK if a guy only charged it for a short while?

A 6 Volt 2 amp battery charger (subject to design) likely wouldn't be too much PROVIDED as you say use it short periods.

2) I do have a 12 V trickle charger of 1 amp. Is there any way I can step the voltage down to 6V without changing the amperage output of the charger too much?

While in theory you might be able to do that its NOT my recommendation

3) What sort of voltage should this little battery show when sitting at rest for say a day after charging?

A full charged lead acid 6 volt battery at rest and stabilized should be around 6.3 volts subject to temperature

PS in years of farming and a used tractor dealer I (in a pinch) used small low amp 12 volt chargers to charge bigger 6 volt tractor batteries USED SHORT TIMES KEEPING AN EYE ON WATER AND VOLTAGES and never had a problem. HOWEVER with such a small battery much more care and caution and short time periods would be necessary, yet for the record, Im NOT recommending it.

Hope this helps

John T

I don't know the answer to what I am about to suggest, but would it work to use the low amperage 12 volt charger if the little battery were put in series with another 6 volt battery?

> I don't know the answer to what I am about to suggest, but would it work to use the low amperage 12 volt charger if the little battery were put in series with another 6 volt battery?

Unless the two batteries are of the same capacity and at the same initial state of charge, one battery will become overcharged and the other will be undercharged. Which may not be much of an issue.

Paul, sure its possible (subject to many factors) to charge two 6 volt batteries in series (with a 12 Volt Charger) and the current would be the same in both. However, current may be limited as dictated by ONE of the batteries and the other may or may not get the proper charge. Sooooooooo even if it may "work" I don't see it as the absolute "best" alternative. When connecting multiple batteries its best if they are matched identical is brand and type and design and even age to better achieve load and charge balance.

John T

When choosing a charger you use 1/10 the ampere hour rating to charge.