Edits in red colour
I would like to give a review on the 24volt frog style battery sold by GM.
I’ve been using lead-gel batteries for the last winter on this bike and therefore have something to compare with. I can assure you that my expectation was high as the price was way over the lead batteries due to the weak Swedish currency. Now when I’ve shopped my economy to trashes on e-bike things, the Swedish crown is stronger than it has been for a very long time.
The first thing I noticed was that it was made for a much longer seat pole than I have on my 28” wheeler, so I mounted it backwards inside the triangle on the extension of the seat pole. It took some of the adjustment away from the rear wheel so I had to find a half link to the chain. This is because I have a 7-speed hub gear and therefore a fixed chain tension.
The battery pack has a key to switch all current off and also to release the battery from the mounting device. It’s just to turn the key a little bit more and lift the battery pack in its handle. To put it back isn’t quite as easy since I have to find the exact position to turn the key back. It should’ve been when the battery was distinctly in the bottom position but it wasn’t. I’ll probably drill the holes up an mm or so as it shouldn’t matter if they are a little bit larger than the locking pin. A cone on the pin is a better solution, but more difficult to achieve without dismantle the whole package.
The charger is proportionately large and therefore has to be carried along separately. This gives a slender look though, and after all a little inconvenience as it is still possible to charge it mounted on the bike.
The tests I’ve been doing so far are the ability to retain the voltage under load when it’s cold. Due to the youth of the winter I haven’t been able to test it in the lowest temperatures it will be operational in, but -11°C is probably enough for most of you. The lead batteries drooped already in -5°C and were nearly worthless in -25°C. This is most likely depending on the batteries quality and can vary a lot between different brands. The GM battery pack haven’t showed any lack of performance yet, even when I had it in the fridge for some time it just gave me the same power as before.
When I drove it in a healthy weather before the winter had arrived I could feel the difference in the hill climbing ability. With the lead batteries it was impossible to ride up the steep street behind my house without pedalling but now the bike does it easily. The batteries are 6 kg lighter which helps, but there has to be more power too for this kind of improvement.
I haven’t done a real distance test yet as she mainly just take me to the work. The difference to the lead batteries is obvious though as I can take a turn into town on the way home even if it is cold. The speed sensor for the CA is too far away from the magnet so I can’t measure speed or distance yet. I have mostly focused on the voltage under load, which seems to be extremely important for the efficiency. This is really something I like to now before I buy my next battery, the voltage under load in different temperatures. It’s amazing that this 250 watt motor take nearly 600 watt up the hill, and this is probably the answer for the increased performance. Even if the lead batteries could deliver the same current, the performance decreased due to the voltage droop.
A truly magnificent thing is that I managed to fit the controller and all of its cable in the mounting device which I didn’t expected. I wonder if this space is meant for the controller or if I just have very deft fingers. It gave a neat looking installation and very short battery cables.
All in all I am sincerely satisfied with this battery pack even if I have to adjust the holes for the locking pin. One thing to take in consideration is the amount of current it can deliver as I only have the mini-motor on my winter bike.
Peter
