Battery Charging Question

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mike - 22 Nov 2004 04:07 GMT

Hi People,

I'm a novice at this electric stuff, so I'm looking for some pointers
regarding charging my batt packs. I'm using Venom 3000 mah nimh packs and a
Propo Supernova 250 charger.

OK, I'm charging the packs just fine, what I'm wondering is whether I can
use the readout on the charger for determining which pack is the best (I
have four). What I'm doing after each race meet is doing a discharge (I know
that this is not necessary, but read on) and then a full charge. At the end
of the charge, the charger gives a readout of the voltage (eg 8.4) and the
mah (eg 3301). So, questions:

1. For racing, should I be favouring packs with higher voltage on the
charger or packs with higher mah on the charger?

2. Or is the mah on the charger an indication of how much current was forced
into the pack to get it to its current voltage. In this case, would a
*lower* mah reading indicate a pack with lower internal resistance and
therefore a better pack?

Can anyone help me make sense of what these readout on the charger mean?

Thanks

MIKE

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kenji - 22 Nov 2004 04:31 GMT

> Hi People,
>
[quoted text clipped - 22 lines]
>
> MIKE

What motors and what kind of racing do you do?

Reply to this Message

mike - 22 Nov 2004 06:37 GMT

Hi,

Quite right, I should have mentioned that I am doing 2wd off road racing
using stock 27 24deg motors. At present I am using Trinity P2K2 motors in an
RC10B4 . I will shortly be also racing an RC10T4 using a Team Orion V2

Mike

> > Hi People,
> >
[quoted text clipped - 24 lines]
>
> What motors and what kind of racing do you do?

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kenji - 22 Nov 2004 14:39 GMT

For the stock motors and racing I'd favor the higher voltage packs. For
the V2 and the truck I think you might be hard pressed to see any
noticeable difference in your race position because of batteries. FWIW,
I have a few of the venom batteries and I also have some 1.16v GP
3300's. For 5 minute races runtime isn't an issue (mah), but there is a
noticeable increase in punch and top speed when using the 3300's
instead of the venom 3000.

What I have found in off road racing is that if you are crashing and
needing to be marshalled a lot your batteries aren't what is going to
keep you from winning races. Once you are consistently not crashing
better batteries can help you win and place better in races.

For my son the rookie racer I actually see him do worse in races when
he uses 3300 packs. What happens is that he loves speed and punch. But
because he can go faster and jump farther he crashes more. A lot more.
He can get an extra lap in a 5 minute ( aprox 14 lap kinda track for A
Main racers) race if he uses the 3000 cells.

Slow is fast in off road racing.

> Hi,
>
[quoted text clipped - 38 lines]
> >
> > What motors and what kind of racing do you do?

Reply to this Message

Dean - 22 Nov 2004 16:05 GMT

>For the stock motors and racing I'd favor the higher voltage packs. For
>the V2 and the truck I think you might be hard pressed to see any
[quoted text clipped - 3 lines]
>noticeable increase in punch and top speed when using the 3300's
>instead of the venom 3000.

Voltage is indeed king in stock class racing.

BUT, the pack with the highest PEAK voltage on your charger is not likely to be
your best pack. This is due to IR (internal resistance). In reality, your BEST
pack will have the lowest peak voltage on your charger, because it more readily
accepts the 5 or 6 amps you are charging it at. That has always been my
experience.

Any MAH rating over 2000mah doesn't really make much difference, that is about
all you will use in a 5 minute heat of stock racing. BUT, higher capacity is
better overall, because then the voltage stays higher throughout the run since
you will not go so far down the discharge time/voltage curve of your pack.

>What I have found in off road racing is that if you are crashing and
>needing to be marshalled a lot your batteries aren't what is going to
>keep you from winning races. Once you are consistently not crashing
>better batteries can help you win and place better in races.

Exactly. 1 crash is usually the difference between 1st and 2nd place in an
A-main around here, our racing is very competitive.

>For my son the rookie racer I actually see him do worse in races when
>he uses 3300 packs. What happens is that he loves speed and punch. But
[quoted text clipped - 46 lines]
>> >
>> > What motors and what kind of racing do you do?

---
Losi XXX KE <the racer>
Losi XX "CR" <the basher>
Associated RC10GT <the other basher>
http://ripperd.com
email: dean (at) the above domain

Reply to this Message

Jim Banks - 27 Nov 2004 15:42 GMT

> <snip>
> BUT, the pack with the highest PEAK voltage on your charger is not
[quoted text clipped - 3 lines]
> amps you are charging it at. That has always been my experience.
> <snip>

Absolutely, dead-on correct!

Signature

Jim
-----
www.onandaga.com

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Model Forum / Radio Controlled / Land Models / November 2004

Battery Charging Question