arnoA

OK, so I intend to build a Li Ion battery inside an original battery pack that had either Ni Cad or Ni MH cells installed, I have both available. Initial measurements lead me to believe that I can get a 7S6P array of 18650 cells in a casing with some room left over for a BMS, wiring and packing. Perhaps a bit ambitious but hey, what are targets for? Then we come to deciding what cells to use. My thought at the moment is to use Samsung 30Q 3000mAh cells with a peak output of 20A. In a six parallel array this should give a possible 120A before too much voltage sag. My guess is that the peak instantaneous demand from the bike would be somewhere in this region but this is still to be determined. I can probably get higher capacity cells but 18aH should be more than enough and I suspect the higher output cells will be more robust both in terms of load performance and longevity. But, what is the load demand? Just how much power does the motor need? I have been unable to get hold of a service manual and even if it gives a specification of the motor, I know from experience that the figure quoted is "nominal". It has to be really. So, what I intend to do is this. I have made up a simple SLA battery pack with a capacity of 5Ah and I have fitted is with some instrumentation wiring connected to a battery powered data logger. With this I can record the current a voltage output of the battery whilst riding under a variety of conditions. If I am able I will try to post some useful graphs when I've done it. Now, many will say why bother? The bike is known to have a 250w motor and a 24V battery so the current must be no more than about 10A. It happens that during my career, I have been involved in battery powered motor system design for people and products that are well known and successful. The success was not accidental, it was design and technology that worked - ask Elon Musk. I will obviously need to see the real time measurements recorded on the bike battery motor but from experience I would not be surprised to see peak currents in the range of five to ten times the quoted demand. It will very much depend on the controller sophistication. OK, these current peaks may be very short term and could probably be ignored without seriously compromising the performance of the bike, but, they will have an impact in response times and efficiency, certainly noticeable and possibly significant. I'll post some more when I get a bit more detail on this but for now I have a question. I find this sort of thing fascinating and love the research involved but know that many find it unutterably boring. So, readers, are you interested? Should I post more detail and discuss the findings? I won't be offended if the general opinion is that I'm a BOF, it would never do for us all to be the same.

Hi! Yes, I do now see that photo's would have been helpful so here is at least one. The connector has four small blades, two for charging and one for a temperature sensor. I did consider replacing the connector early on but it's actually less easy than it appears at first glance. The original is rectangular and comes flush to the surface it's mounted to. Then there is a folding handle on the battery that comes down to cover it with very little clearance. There is an internal 2A fuse in the battery pack. As well as this, if possible, I would prefer to keep the bike as original as possible. Since it seems to have survived intact for 20 years, it seems a shame to butcher it. Part of the attraction was that it is rather cute! A fiend of mine has a later Yamaha bike that has had a generic battery grafted on to it and although it works very well, it does tend to look what it is.

Thanks! On reflection I can see the benefit of pictures so I'll try to post some later. I can see that building my own battery is probably not the most cost effective but one reason for buying the bike was to explore the technology myself. What better or more relevant starting point than to build a battery? I will post a bit more about the design process I intend to follow in the technical forum.

Hi! I've purchased an elderly but apparently unused Yamaha XPC-26 Pedelec which has a few problems. Any help would be very useful. The first problem is that the battery pack is beyond recovery. I've managed to get three spare battery casings and made a 24v 5Ah SLA battery which works albeit with limited range and intend to make a 20Ah Li Ion battery over the next month or two. The batteries I can do but my problem is that the bike came with no battery charger. I can even do chargers but the sticking point is the connector for the battery pack input. The battery pack has a four blade male connector which looks to be vaguely generic and requires the corresponding free female that would have been a part of the original charger. Does anyone know that this connector is, where I might be able to get two or three or have a redundant/broken charger I can cannibalise? The second problem is that I have zero documentation. Ideally I would like to get hold of a full service/repair manual so I can get a better understanding of the mechanisms and circuits but anything would be better than nothing. Can anyone help? The third problem is that the front basket originally supplied with the bike is missing. I'm sure I can make something suitable but it would be nicer to get one of the originals. Anyone? That's it for now folks!

I guess the title says most of it... I'm a semi retired engineer who has taken the Covid19 opportunity to have a play with electric bikes. I'm dipping my toe in the water by purchasing an elderly broken bike to experiment with. The idea is to reduce the use of my car for local trips, motivated by environmental consciousness and parsimony. Unfortunately significant surgery prevents me from using pure pedal power in my slightly hilly home area. The bike I have purchased is a Yamaha XPC-26 that appears to have never been used and parked in the dry. However, unsurprisingly the battery is beyond redemption and, there is no charger with it. I've temporarily grafted in a 24v SLA battery and pumped the tyres up and it seems to work. Now I need to remedy the ravages of time on the fittings but more importantly convert it to a Li Ion battery. For the battery, I want to convert the existing casing to accept a 7PS6 array of 18650 cells which looks like it would fit and give plenty of range. I have managed to get hold of three spare battery cases so for the time being I am making a 5Ah SLA unit until I can sort out the more complex version. Any advice would be welcome, particularly if anyone has a workshop manual.