Trickle Charger Question

[PaulH]

We all know that the wall-wart chargers that come with our eqipment suck. My question is: Does anyone know of a good slow (C/10) charger that can sense when the pack is full, then go to a trickle (C/20) mode?

Better yet, does anyone make a charger with multiple (4-8) outputs?

[Teej]

What are you using for batteries?

With the use of a 2400mah pack on my helis, the stock charger _IS_ a trickle charger for that guy...although I haven't upgraded the tx pack yet.

[PaulH]

The stock wall-wart chargers do not have any kind of cut off or adjustment. They can actually kill packs by over-charging them. If it's providing much less than C/10 current, then there is a good chance that it will never charge the pack.

I want something that I can set the voltage and current, wait for it to sense that the pack has been fully charged, then shut off.

There is something called the Ultimate Charger. According to the maker's web site, it's not being made any more. I like his idea, but I don't really need anything as fancy (or expensive) as what he made. The Mini-Ultimate Charger is closer to what I'd like, but his model didn't have enough settings for the current.

I'm thinking of using a pair of LM317 regulators wired in series. The first would be a voltage regulator providing 6 v (1.5 v / cell * 4 cells) and the second a current regulator providing C/10 mA. Couple this with a timer and you have a basic charger. Add a volt meter that sample the pack periodically and the charger could shut down early if the pack was not completely drained. Even better would be if the circuit would wake up every day for an hour and perform a C/20 charge to keep the pack topped off.

Now multiply that circuit by the number of NiCd and NiMH battery packs needed to operate several large birds.

I know this can be done easily. I could go all-out and use a microcontroller and a PWM power supply to charge packs, but that's overkill for what 90% of us would ever need.

- Paul

[Teej]

A simple vacation lamp timer works well enough for me.

Used it 15 years ago when I was in RC last time, and it still works great. :)

[PaulH]

Yup, that would be perfect! Multiple chargers plugged into a power strip with a vacation timer on the other end would be an effective "burp" charger.

- Paul