ALC 7000 Expert - Battery Charger

Because I planned to build a battery pack for my Minolta DiMAGE 7Hi, I had to get a charger that can handle battery packs instead of a charger for individual cells. I ended up with the ALC 7000 Expert and I am happy with it, although it has certain restrictions described in the details section.

Summary

The ALC 7000 Expert can handle NiCd, NiMH and Lead-Acid cells or cell packs with a nominal voltage from 1.2V to 24V and provides a maximum charge current of 3.5A. It has 4 channels available, but several restrictions apply. These will be described in the details section below.
There are six service programs available: Charge, discharge, discharge/charge, test (charge/discharge/charge), cycle (charge/discharge until there is no increase in capacity, then charge) and refresh (try to revive dead batteries/packs). Charge control is done by voltage/current monitoring and a safety timer based on the selected capacity. There is no temperature sensing with this model, so ultra-fast charging with 1C or above is not recommended.
The charger is available with RS232 interface and software to record current/voltage/capacity during operation. With the software you can also control the charger from your PC.

The ALC 7000 Expert is built by ELV (http://www.elv.de/), a German company. Although the instructions are in German and English, it is worth mentioning that the front panel and the custom-made LCD are labeled in German only (as a warning for lingua-phobics).

The ALC 7000 Expert has a retail price of 199.50 Euro for the ready-to-use version including RS232 interface and software. It is also available without RS232 interface and software (172.50 Euro) and as a kit including RS232 interface and software (155.50 Euro).

There are three different charging adapters available as kits at 19.95-30.65 Euro each: 8×AA, 4×AA and 8×AAA. The 8× adapters have a switch to split them into 2×4 adapters.

The price may look high at first glance, but my two Ansmann PowerLine 4 chargers cost 49.95 Euro each and all they can do is charge/decharge 1-4 AA cells individually. And I almost ended up buying a different brand of charger with only one channel, 14.4V maximum nominal voltage and 2A maximum charge current but for the same price!

Because the availability of the ALC 7000 Expert may be limited outside of Germany, especially overseas (attention: 230V only), I would be interested in whether there are chargers available in your area that can compete with this model.

ALC 7000 Expert In Action

The ALC 7000 Expert and the charging adapter holding 2 sets of 4 AA cells.
Channel 1 is in discharge mode and reads a voltage of 4.06V at a discharge
current of 1.285A and a discharged capacity of 0.03Ah (empty set).

Details

Although all four channels can be connected at the same time, channels 1 and 2 work sequential. If one channel finishes its job, the other will start its job. This means that only three channels can be active at the same time. This is done to maximize the available charge current with the given power supply.

Channels 1 and 2 are designed as high-current channels. Up to 8V nominal voltage the maximum charge current is 3.5A (1-6 NiCd/NiMH cells or lead-acid batteries with 1-4 cells). From 8.4V to 12V nominal voltage the maximum current is 2.4A (7-10 NiCd/NiMH cells or lead-acid batteries with 5-6 cells). From 13.2V to 24V nominal voltage the maximum current is 1.2A (11-20 NiCd/NiMH cells or lead-acid batteries with 7-12 cells).

Channels 3 and 4 are designed as low-current channels. They can charge packs with up to 12V nominal voltage (1-10 NiCd/NiMH cells or lead-acid batteries with 1-6 cells) and share a maximum current of 1A. This means that for parallel use and the same charge current for both channels you have a charge current of 0.5A per channel available. But this is enough to charge two sets of 2000mAh AA cells even during a short night.

Although the charger tries to detect the nominal voltage of the pack, it is best to set it manually. This is done by selecting the cell type, then the voltage can be increased and decreased in the appropriate steps (1.2V or 2.0V).
You always have to set the capcacity and the decharge and charge currents. This can be done with the (+) and (-) buttons, but with the arrow left button you can select any digit to speed up the adjustment. The capacity can be selected in a range from 0.01Ah to 99.99Ah in 0.01Ah steps, the currents can be selected in 0.001A steps (1mA) up to the maximum current for the selected voltage.

The charger does not support temperature sensing. Charge control is done by detecting the voltage drop for NiCd/NiMH cells and monitoring voltage/current for lead-acid batteries. In addition to that it has a safety timer based on the selected capacity which will cut off after charging with 150% of the selected capacity. Therefore it is important not to enter a lower capacity for low-current charge to enable full charging and not to enter a higher capcaity for high-current charge to prevent overcharging.

The software allows to build a database for your rechargeables where you can store the parameters and remote-control the charger. I don't like the idea of leaving the PC up and running as a remote control for the charger, but it's a nice feature.

One special detail and the only thing I really don't like about the charger: It is equipped with a temperature-controlled fan, obviously the cheapest model available. I think I'm going to replace it with a better one, but at such a price it should be equipped with a decent fan in the first place.
Besides that it is equipped with a 230V power supply instead of a voltage-free switching power supply, so you can't use it worldwide.

Nearly Unlimited Use

If you come across an unknown cell pack you can count the cells which will give you the nominal voltage. Then you can start with moderate charge/discharge currents and capacity. Based on the capacity measured during discharge you can do further test programs or cycle programs. Like this I was able to revive the cell pack in my cordless drill with built-in battery pack and broken charger. If the cell pack doesn't have acceptable stamina (which is most likely for NiCd cells after some years), I just have to buy new cells of the same size, but maximum capacity and have a brand new cordless tool.