Beginner battery and charger questions

[Slippin3]

Hey Everyone,

I am new to the hobby, and just bought my Gravel Hound about 3 weeks ago. The 4hr AC charger that came with the kit, just wasnt enough, and I am going through batteries quick with my new 21t motor.

So I went on eBay and bought a Duratrax Piranah DTXP4000 and 3 batteries as a package. The batteries are 2x Conrad Energy 2400mah batteries and 1 Racers Edge 1500mah pack.

Questions are:

1. This charger says it will go up to 2000mah, what happens if I bought some 3300mah packs? Would they only charge to 2000mah?
2. The charger keeps flashing (meaning trickle charge) well after the 45mins it says it takes to charge. I guess it does not auto shutoff?
3. The 1500mah pack seems a bit quicker. Is it a higher quality pack? I guess this is why 1500mah packs range in price. I thought they would almost all be the same.

Thanks in advance!
-John

[Duster_360]

1. Yep, quits at 2000mah. The way I understand it, due to resistance, it takes higher and higher voltage to deliver more input to the charging batt. This is handled by the chargers internal power supply. DT has chosen to go with an internal power supply that enables you charge to 2000mah. If you put a 3300mah on there, you might see more than 2000, but you wouldn't get close to 3300.

2. Only directions are on the box, but this came from Towers ad for your charger " When fast charge is done the LED flashes, indicating the TRICKLE charge has begun. There Is No Separate Instruction Sheet."

I would guess no auto shutoff, just stays on trickle until you disconnect.

3. Maybe - it could be that the individual cells in that pack are "closer" together as far as their cell voltage and output that the cells in your other pacs. If the 1500 cost a little more in relationship to its size, then poss they are higher qual cells. Theres a lot of diff cell suppliers out there and I would expect therer to be some diff in grades available.

Know you don't want to hear this, but a better charger would have been the digitial peak Piranha charger - doesn't have the limit and offers more flexibility in setting up charges for $15 more -

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCLD5&P=ML

[tadium54]

you have the pirahna peak charger. its a decent unit, but you could get a pirhana digital peak and be safe for a while with chargers. i still use mine(as i have many batteries to charge).

1. i think the only 3300s are nimhs, and your current charger wont charge them without signifigant modification.

2. nope, no auto shutoff.

3. the 1500 is faster than the 2400 packs? im guessing your false peaking. considering your batteies exceed the chargers limit, its probably the case. either that, or theyre bad cells.

[Slippin3]

If I have the 2400mah pack in and gun the car it chugs along.... like if the battery was dead. If i squeeze the trigger slowly and ease it up to speed its fine. Thanks for the help on chargers guys. I paid $40 for the 3 batteries and the charged. :)

-John

[tadium54]

that doesn't sound normal. find a buddy or something with a digital peak charger that can cycle the pack. that might give you an idea of what the problem is

[Slippin3]

LOL.... I am new, and none of my buddies are into this :) Just one guy I know, and hes into nitro. If I could sell this charger locally I would, maybe I'll talk to the :HS when I am in next. See if they know anyone

-John

[tadium54]

you could build a bulb discharger and keep repeating the cycle

[guver]

It sounds as if the charger is stopping too soon on the 2400 batt. It should be chargeing around 30 minutes or so (with solid lite)

The actual capacity of the charger is kinda irrellevent, but is around 3300 for a 6 cell batt. I just multiplied 4.5 amps by .75 hours = 3.75 mah (3750) It will be lower for a 7 cell and 8 cell, if I remember corectly when the 7 cell is selected the rate goes a bit higher and it doesn't quite get to the 4.5 rate. Even at 4 amps it would be 3000 mah.

I say it's irrellevent because if it shuts off it can simply be restarted to charge a 6000 mah battery , get it? The one problem I see is that it is a nicad setting for charge termination and will slightly overcharge any nimh batts. nicads are 2400 and less.