Im trying to figure out the best method to charge my 4000mah and 5000mah 2s lipo batteries. I been useing my Onyx 245 and chargeing everything at 5amps. But it only has setting for 0.8amps, 1.5amps, 3amps, or 5amps. What if I charged a 4000mah battery at 3amps would that be better for it? And is it hurting anything charging the 4000mah at 5amps?

Depends on the battery if you can charge higher than 1C or not. There's never any risk charging at less amps though, it'll just take a bit longer to charge.

As WP says, depends on the Lipo. If it can handle 5C charge (C meaning the number with you multiply the amount of mAh to calculate the maximum safe charge current) you would be able to charge a 4000 mAh lipo with 4000 x 5 = 20000 mA so 20A. If it can handle only 2C, the maximum safe charge is only 8A, etc.

If you want a more direct answer, you have to post a picture of your lipos.

Meanwhile, get to know more a bout lipos, as treating them safely is the key yo prevent one day your car, or even your home catching fire. Lipos are to be treated with respect:

http://www.rcgroups.com/forums/showthread.php?t=1287041

Whats a good ac/dc lipo charger that can charge 4s batteries? I had the x1 for a little while but it kept stoping in the charge to display a "battery vol err cell connect" message. So now that was returned Im looking at the Dynamite Passport Ultraforce 200w ac/dc, or the Thunder Tiger tp610p. Anybody got any goods and bads of these chargers?

Don't know if you still have me blocked, but these seem like beefed up versions of the Imax B6. The B6 is an excellent all round charger, but standard version it's limited to 50 watt output, limiting charge current at higher cell count. Up to 3S it can still reach it's 5A max current, but on 4S and higher max current is lower. So a 200 watt version should do much better.

However, do you have 4S packs, or want to charge 2 2S packs as one 4S? If I recall well you've got a Slash, and wouldn't that be too fast on 4S?

Keep a eye out for this useful little catalog sitting on your local hobby stores counter top. It's full of good info for anybody trying to understand the electric side of the hobby.

Could be useful, although possibly the same do's and don'ts are already on the internet and likely also contained in FAQs on this very forum.

Is it the same as this?

http://www.dynamiterc.com/Articles/A...ArticleID=2350