I am a new member , and have only been back into electric bikes for about a week , having bought an old Powabyke with lead acid batteries . Although heavy , it works well and has to be the bargain of the year at £85 . The batteries are the original ones ,and under test gave a no pedaling range of 13 miles on the flat . I bought it with a view to replacing the batteries . As a newbie , I am reading all the old threads .[yes , I know i need to get out more .] New lead acid batteries are likely to cost around £80 . I have been looking at newer battery types , and decided that NiMH batteries are a better bet than Lithium . With a 1 year guarantee , Lithium looks to me like a poor gamble . I found an old thread about home made NiMH battery packs using AA cells . that was from 2007 . However , on Ebay today you can buy D cells at £2.80 each . so 30 x £2.80 is £8.40 , so not much dearer than lead acid and about one third of the weight . The cells are 1100 milliamp hour . Then of course we have to charge them . For lead acid , I have built my own chargers up to 48 volts by rewinding old microwave transformers . Yes I know you would have to measure voltages and temperature . Would appreciate any feedback/opinions .
NiMH Batteries Today
- Thread starter neptune
- Start date
Welcome to the forum.
I am not sure if home made NiMh batteries are worth it. Also you are going to want more than 1100mah. That will barely get you a few miles!
What about some of more beefy Sub C NiMh 3700 + mAh ready made 12v packs * 3 connected in series. You need to ensure that they can take the higher discharge rates though. Charging WILL be a pain.
Alternatively I myself use these
They are A123, 3.3v, 2300mAh (LiFeP04 2000+ charge cycle life) cells made up into 6s1p packs and then connected in series with a fuse for 12s1p pack. Very safe and can take 80amp discharge. They can be bulk charged with a cheap 36v PB charger, though you may need to balance them sometimes.
Cost about £60-70 to make. I carry one or two packs depending on how for I go. Here is my build thread.
Then again if you are looking for a large range with no pedaling and given your original heavy bike, replacing with lead acid may still be the cheapest/favourable option.
Regards
Jerry
I am not sure if home made NiMh batteries are worth it. Also you are going to want more than 1100mah. That will barely get you a few miles!
What about some of more beefy Sub C NiMh 3700 + mAh ready made 12v packs * 3 connected in series. You need to ensure that they can take the higher discharge rates though. Charging WILL be a pain.
Alternatively I myself use these
They are A123, 3.3v, 2300mAh (LiFeP04 2000+ charge cycle life) cells made up into 6s1p packs and then connected in series with a fuse for 12s1p pack. Very safe and can take 80amp discharge. They can be bulk charged with a cheap 36v PB charger, though you may need to balance them sometimes.
Cost about £60-70 to make. I carry one or two packs depending on how for I go. Here is my build thread.
Then again if you are looking for a large range with no pedaling and given your original heavy bike, replacing with lead acid may still be the cheapest/favourable option.
Regards
Jerry
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Hi Neptune, i think you may have meant 11000 mAh, not 1100 mAh as posted, i.e. 11 Ah.
I think it's a risky proposition, since these cheap cells are often not very consistent. Those doing it previously, including myself, usually overbuy so that a reasonably matching set can be chosen by testing. It's very important with NiMh that the cells match to avoid the rest of the pack destroying any weak one. One reason why battery manufacturers were so keen to get out of NiMh into lithium was this, the high expense of matching and only using cell groups from single production batches of cells.
The other factor is the discharge rates. Claims about NiMh cell capability in this respect are often spurious, the fact being that manufacture of the best grade D cells virtually disappeared with the adoption of lithium. Most D cells now have true continuous rates of around 5 Amps, too low for your powerful Powabyke motor which can have a peak demand of just over 16 Amps. This sort of current draw will lead to very short cell life if inadequate cells are used.
So there's the risks for your £84 and labour, you might be lucky, but if it were me I'd stick with the SLAs for the convenience and performance and not bother about the weight.
I think it's a risky proposition, since these cheap cells are often not very consistent. Those doing it previously, including myself, usually overbuy so that a reasonably matching set can be chosen by testing. It's very important with NiMh that the cells match to avoid the rest of the pack destroying any weak one. One reason why battery manufacturers were so keen to get out of NiMh into lithium was this, the high expense of matching and only using cell groups from single production batches of cells.
The other factor is the discharge rates. Claims about NiMh cell capability in this respect are often spurious, the fact being that manufacture of the best grade D cells virtually disappeared with the adoption of lithium. Most D cells now have true continuous rates of around 5 Amps, too low for your powerful Powabyke motor which can have a peak demand of just over 16 Amps. This sort of current draw will lead to very short cell life if inadequate cells are used.
So there's the risks for your £84 and labour, you might be lucky, but if it were me I'd stick with the SLAs for the convenience and performance and not bother about the weight.
Flecc I have never heard of or ever seen a 11Ah single D cell!
As we say probably best to stick with SLAs
Regards
Jerry
As we say probably best to stick with SLAs
Regards
Jerry
Hi guys . This forum is brilliant as regards the quality of technical info available . I did in fact mean 11000 milliamp hours . I will study the info about the Radio control cells this evening .I will probably choose lead acid in the end , because it is hassle free , and I ride on the flatest roads in the world , the fens ,so weight is not really an issue . This area is so flat that there are NO contour lines on the local Ordnance Survey map , apart from the local village of Amber Hill , which towers a vertigo inducing 8 FEET above the surrounding fen . Used to be so peaceful until all these base jumpers started turning up ... Thanks again guys .
Just to add my experience as I tinkered with this a year or so ago. I bought 10Ahr D cells mad by Ansmann which are expensive and good quality and they struggled to deliver the current and I think flecc is right (as usual) about the current delivery and matching of cells. sub C cells as used in the model world do perform very well but are limited to about 4.5Ahr and are very expensive. I also made a pack up from loads of 4/5subC's but it was time consuming, heavy and a pain to charge.
Personally I'm a convert to Lithium and with the right battery they are easy to charge and last many years but of course many 100's of £.
Personally I'm a convert to Lithium and with the right battery they are easy to charge and last many years but of course many 100's of £.
9 and 10 Ah D cells were common for NiMh e-bikes, the 11 Ah claims appearing after e-bikes changed to lithium.
Damn, I had no idea that a single D cell could pack an 11Ah capacity. I think I was getting confused with cell size. Of course you need 30 because they are 1.2v and that would make a pretty large sized pack.
Regards
Jerry
Regards
Jerry
Last edited:
Yes, eZee's 9 Ah battery used 30 x D cells as six vertical columns of five cells each column inside their standard case. Weighed a brutish 5.5 kilos!
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