Thanks thats a helpful summary. I do have two 120ah leisure batteries kicking around so I might try that route first, just as its cheap for me. I have been looking at putting LION cells together. My cousin has actually put together a 3.6kw battery doing this in his garage! Only weighs about 25kg apparently. Overkill for me, but it was interesting! If the leisure batteries don't cut it though, I think I will do as you suggest and get another 48v battery for direct charging.

Another route is the large LiFePO4 cells from CALB and others, 4 of them for a nominal 12V battery. Plus a BMS board of course. They are tolerant of deep discharge, and half the weight per Ah as lead, which means for usable capacity, about a quarter the weight. Also only 4 big cells to connect rather than a large number of li-ion 18650 or 21700. And very high cycle life, 2000 is not uncommon.

HARSH! No swear words, no picking on anyone in particular, just general terms.....If you feel picked on, you read that into it all on your own.

You should read some of the replies I get from people who could not find their pwn backside if given an hour or so to do it!

Some Pedelecers are more of a study for other people wanting to learn more, first hand, about the "Dunning Kruger Effect".

I wish you again, a great day.

Andy

Awesome! I'll take that as a no!

I do have two 120ah leisure batteries kicking around so I might try that route first, just as its cheap for me.

As you've got the batteries, for what you want to achieve, I'd just do that too. As [mention=34503]matthewslack[/mention] points out it's not the most efficient, but it is a cheap, robust, safe solution that works.

 

For my 2 x 10.4Ah 36v ebike batteries, I've done it with an old 100Ah van starter battery, a cheap 100w panel, £20 solar controller off ebay, and a £40 sine-wave inverter. The (mobile) problem I had was the modest panel size/limited daylight time to recharge, but in a static/shed/garage situation, you have far more scope. Obviously, as you've already discussed, you're going to need something a little beefier for what you want to achieve, but given you already have at least the majority of the parts you need kicking around, it seems a no-brainer to me.

 

Good luck!

Thanks thats a helpful summary. I do have two 120ah leisure batteries kicking around so I might try that route first, just as its cheap for me. I have been looking at putting LION cells together. My cousin has actually put together a 3.6kw battery doing this in his garage! Only weighs about 25kg apparently. Overkill for me, but it was interesting! If the leisure batteries don't cut it though, I think I will do as you suggest and get another 48v battery for direct charging.

Just a small point, leisure batteries are really not for bikes anymore (were maybe used 20 years or so ago), far too heavy for the energy they store.

 

Until something better comes along, we are all stuck with Li-ion chemistries. But there are some interestiing developements in store over the next 10 years or so.

 

The trick to staying safER(!) with Li-ion Batteries are basically as follows:-

1) protect them at all times from physical damage and shock.

2) If not a well trained electrical engineer, do not "play" with them at all....

3) Always buy best quality cells in your Batteries. I myself like panasonic, but other good makes come to mind. "No name" batteries are to be avoided completely. Buying from shops that resell them can be fraught.....

4) Therefore always buy directly from the manufacturer....

5) If you decide anyway to try and make your own battery, or recell one you have, get 1st class cells, all from the same manufacturer, all of exactly the same type, all made on the same day, and all sorted by the manufactuer for exact compatability, charge all cells to exactly the same level before welding them together. YES, buy a battery spot welder to assist with the build.

Doing all that will usually reduce size/difficulty of some of the problems you may encounter.

This may prove instructive:-

I myself decided LONG ago, to only buy finished new high quality batteries, as I like the fact that I can count to 10 on all fingers and thumbs still!

regards for a great day

Andy

PS. As a test for anyone, do you all fully understand the difference between a battery and a cell? As I see some people dangerously mixing up the terms here on Pedelec!! As if they cannot get that right, what else are they mixing up?

If some of the troublesome BMSs have volatile memory which erase with loss of power, or some other method of resisting battery pack cell replacement - is a rapid switch (Schottkys) to an alternative power supply or battery pack viable, while the original battery pack has it's cells replaced? It's something I'd consider trying, if I owned an otherwise irrepairable Bosch ebike battery.

Edited April 3, 20224 yr by guerney

https://www.chroniclelive.co.uk/news/north-east-news/first-kind-grid-e-bike-23464163

My style of "Floating".....

I used to set my caravan charger max voltage at 70% of the rated battery capacity, for say a 12 volt nominal battery, that would be somewhere around 13.2 volts. Different manufacturers specify different levels.

Also, I cut the load at around 11.6 volts...

 

So do you happen to know what was the original Watt/hour maximum potential of your battery (maybe quoted by the manufacturer?), and then what was the actual usable Watt/hour figure that you were getting when you used your method to extend its life ?

 

I suspect your method does work, but one would want to know how much actual usable capacity you are sacrificing, so one could then calculate how much extra capacity to factor in when initially purchasing a battery.

Just a small point, leisure batteries are really not for bikes anymore (were maybe used 20 years or so ago), far too heavy for the energy they store.

 

Until something better comes along, we are all stuck with Li-ion chemistries. But there are some interestiing developements in store over the next 10 years or so.

 

The trick to staying safER(!) with Li-ion Batteries are basically as follows:-

1) protect them at all times from physical damage and shock.

2) If not a well trained electrical engineer, do not "play" with them at all....

3) Always buy best quality cells in your Batteries. I myself like panasonic, but other good makes come to mind. "No name" batteries are to be avoided completely. Buying from shops that resell them can be fraught.....

4) Therefore always buy directly from the manufacturer....

5) If you decide anyway to try and make your own battery, or recell one you have, get 1st class cells, all from the same manufacturer, all of exactly the same type, all made on the same day, and all sorted by the manufactuer for exact compatability, charge all cells to exactly the same level before welding them together. YES, buy a battery spot welder to assist with the build.

Doing all that will usually reduce size/difficulty of some of the problems you may encounter.

This may prove instructive:-

I myself decided LONG ago, to only buy finished new high quality batteries, as I like the fact that I can count to 10 on all fingers and thumbs still!

regards for a great day

Andy

PS. As a test for anyone, do you all fully understand the difference between a battery and a cell? As I see some people dangerously mixing up the terms here on Pedelec!! As if they cannot get that right, what else are they mixing up?

 

Thanks Andy, I will take that on board. I do want to go the cell route as one of the reasons im doing an ebike conversion is wanting to enjoy a project. It is the journey as much as the destination for me. I have got a "can do" attitude that gets me in trouble sometimes, but I will take on board what you say and watch a ton of videos before I start.