From: Per Elmsäter Subject: [BC] Maha C777PLUS-II review Date: Tue, 25 Nov 2003 00:39:22 +0100 Message-ID: <1475457389-1463792382-1069717076@boing.topica.com> [This message has been edited and resubmitted by Per Elmsäter.] Due to input from the bikecurrent mailing list I bought a Maha MH-C777PLUS-II charger recently. One of the reasons I chose it was because it was capable of charging up to 12 cells which is something I wanted due to the simple fact that I have 12 cells in my battery- pack. I am primarily using it to charge these 12 NiMH cells to 4500 mAh according to their specs. Thanks to the digital readout I can see that this is what I'm getting. I can do a discharge cycle where it will automatically continue by charging at 800 mA. This shows that I receive between 5100 - 5200 mAh. This of course is a higher number than I receive at discharge, 10-15% according to Maha, and seems quite normal. When full I can also do an analyze cycle which then discharges the full battery at a rate of 300 mA. I have not done this yet on my bicyclepack, since discarging at this rate takes a very long time. Charging is usually 420 minutes from empty. Another feature apart from the digital readout is of course several diffferent means of detecting a full charge. - Negative Delta V - Zero Delta V - Delta Temperature - Timer. ( It always cuts off after 13 hours ) If you have more than 13*800 mAh = 10.4 Ah you can start a new cycle after 13 hours and it will then detect a full charge by one of the other three methods, according to the manual. So far only the Negative Delta V has terminated my charge. It will also charge all NiMH, NiCd and Lithium-Ion, Lithium Polymer chemistrys. 1-12 cells of Ni and 1-4 cells of Li. It will however not discharge a single cell. You must have a minimum of two or three cells. I forgot which. My simple Sigma Mirage lighting system is now the brightest system in our forest. My 20% overvolted 20W beam definitely feels bigger and brighter than for instance a Niterider Blowtorch. The 5W beam is plenty enough except when going fast. I get a max of 9 hours and a min of 2.25 hours. Having a button by my thumb makes it easy to switch down to 5W as soon as I hit a long climb for instance. So I figure I can easily stay out 4-5 hours and have all the light I need, or commute for 9 hours. Thankyou all on the bikecurrent mailing list that guided me to this solution. I am as of now not using a LVR but it will come as I refine this setup ;) What I am doing now is running two packs of six cells each in parallell. This gives me 9Ah and 7.2V. Ie 20% overvoltage. Of course it's way over 8V when I start out but the bulbs haven't blown yet. When charging I connect all the cells in a series to avoid problems. This is of course done automatically by how the connectors to the batterypacks are bridged. When I connect the lights to the four pole connector coming out I get a parallell connection and when I connect the charger to the same four pole connector I get a serial connection. Very simple actually. The bridging is done on the incoming connectors. Out of the batterypack I just have two plus and two minus on a four pole connector that know nothing of each other. Now to the criticism. Well it wasn't the cheapest charger around but I believe it is worth it's money. Especially since I can use it for many other appliances also. The temp sensor is on a very short cable, about 15 cm to be precise. This makes it awkward sometimes when charging something except cellphone batterys and other small stuff. I think this is what they had in mind when designing it since there are plenty of small springy contacts on top, makin it easy to connect all sorts of small batterypacks. Plus a short cable with alligator clips on it. However : Here comes my biggest cause of concern. The charger does not easily detect what kind of batteryconfiguration you are hooking up unless you connect it to the naked minus and plus poles. Then all you need to do is tell the charger if it is a Li or Ni cell you are conecting. The manual states that when using the charger directly on a charge connection that is protected with a diode, rather than a discharge connection, then the charger cannot detect polarity. They continue by saying that all you need to do then is figure that out manually and switch it over if needed. There is a polarity switch on the charger. Well I thought, no problem I have a Voltmeter. So I connected straight into my Cateye Ellipsoid bikelight where the original charger goes in. It is 5 NimH cells and they supply a 9V charger with a 300 mA current. Well the Maha charger started out reading something around 6 V but after only a few seconds it went straight back up to 22 V. It was no time before my bike light was smoking ;( Well you win some and you lose some so I figured there was just too much electronics inbetween and decided that the next time I'd see if I could get a voltage reading first, before I started. This time I tried an electric screwdriver and measured 3.55 V. I connected the Maha charger. It showed 3.55V for a few seconds, then it went straight up to 14V. This time I was a little quicker and I think I saved it. Anyways it is still functioning even though it smelled quite a bit of plastic. This is actually too bad since many times it is quite a hazzle getting hold of the naked poles without any electronics inbetween. I could really appreciate a manual override where you could tell the charger how many cells are there when needed. But, for the batterypacks that I build myself it is absolutely super and I can surely recommend it. Also for cellphones, digital cameras and such of course. I analysed my wife's cellphone battery when she complained about it going dead as soon as she talked a minute. The digital readout told me it would only hold a 25 mAh charge so we didn't have to wonder any more. I must say I really appreciate this simple digital display.