SkyRC B6AC V2 Carger and Discharger

Support Other Pololu products
1

I just purchased from Pololu both the SkyRC B6AC V2 Battery Charger and a number of your different rechargeable batter packs including the 32/3NiMh and 42/3NiMh.

I set the current on the charger to .4A since each of the battery packs is rated at 350mha, and used a cycle of 2 and peak recharge of 2. I noticed with both of the above battery packs that at the end of the charge, the charger listed for the 32/3NiMh 4.40V and a capacity of under 300mha, and for the 42/3NiMh the charger listed 5.92V and a capacity of 299mha.

Right after the chargings, I then tested out the charger’s BATTERY METER and for both battery packs it listed voltages below what it just listed after the charging! For the 32/3NiMh it listed 4.04V and for the 42/3NiMh it listed 5.66V. As I did not understand why the same machine would provide lower voltage readings for both battery packs than what it listed right after charging the same battery packs, I measured each of the packs with my VOM and the VOM readings closely matched the BATTERY METER readings of the charger, that is 4.10 for the 32/3Nimh and 5.56V for the 42/3Nimh.

A few questions regarding the above:

  1. It seems that neither of the battery packs achieved a full voltage/capacity charge of 4.5V (350mha) or 6.0V (350mha). Is this a problem with the charger, batteries, or both?

  2. Does the fact that the final voltage listed on the charger’s screen differs significantly from the actual voltage as accurately measured by both the charger’s BATTERY METER as well my VOM, indicate that there is a problem with the charger?

  3. The brand name of the batteries in the packs is covered by the pack casing. What brand of batteries are these?

In advance thank you for your assistance

2

Hello.

It sounds like you are using our 4×1 2/3-AAA and 3×1 2/3-AAA battery packs. These are generic NiMH batteries, so the nominal voltage for each cell is around 1.2V (not 1.5V like an Alkaline battery cell). This means that the 4-cell pack should have a nominal voltage of around 4.8V and the 3-cell pack would be around 3.6V, so your voltage measurements look reasonable for these batteries. The voltage shown at the end of the charge might be the voltage used to charge the battery; the battery itself will have a voltage close to that immediately after charging, but it will rapidly start dropping closer to the nominal 1.2 V per cell.

As far as the capacity you are seeing, I believe the values seen at the end of the charge process are how much capacity the charger has added to the battery. Since you are seeing a slightly lower value than what these batteries are rated for, it is likely that the batteries were not fully discharged. Also, you might try lowering your charge rate (maybe to somewhere between 1/10×C to 1/2×C). It is common to slow charge NiMH batteries the first time they are charged. Cycling them a few times might help as well (a typically discharge rate is around 1C).

-Brandon