Yamaha PAS NiCd to Lithium

[NeilP]

Hi all.

I have been asked to re-pack a pair of these old Yamaha bikes.
The gentleman is fully aware that cost is likely to be more than the bikes are really ‘worth’ and he does have a pair of folding SeaGo bikes too, but they have had them for 18 or so years and very fond of them. He has not blinked at a cost of £500-£600 to do them, ... a wealthy elder gentleman, and collector of vintage Rolls Royce cars... he knows what he wants, and has the funds to achieve it. So although many may think this a ‘waste of money’ he and his wife like their little Yam’s and want to keep using them.


So, original pack is
20 cell NiCd
D-cells probably 5ah
Fused output to 30 amp

So, a NiCd pack... what would it’s voltage range be..,?
I see the charger has a 26 volt refresh mode. So controller must be good for at least 26 volt

LVC... NiCd. 1 volt per cell? So 20 v

Not been able to source new NiCd D-Cell, do NiMh... or go Lithium.

But Lithium... 6series or 7 ?

The old battery pack will be able to comfortably hold a 7s6p pack with a BMS. With Samsung cells at 3ah, that would give an 18 Ah pack as opposed to original 5ah. Already have quotes from LiTech in China of £420, shipped to UK for two packs and two chargers. So well within the gentleman’s thought of £500.

These are my thoughts, ..
7 series Hot off charger of 29.4 hmmm don’t want to cook the controller and let the magic smoke out.

But if I went 6 series, top end hot off the charger will be good at 25.2
But the bottom end... if the controller has LVC of 20 volts... how much capacity will I loose... probably very little, that will take the lithium down to 3.3 volt per cell. Since the overall pack capacity is still massively more than the original pack, probably not a consideration at all at 6s I can fit 7 parallel. With Samsung cells that is a 21ah pack . Even if I lost 30% capacity due Controller LVC cutting in before the pack discharged, I’ll still have a 14ah capacity ... as opposed to NiCd pack of 5ah.

Think I have convinced myself 6 series is the safer option.... but opinions please...

Thank you

 

[Nealh]

The controller most likely will be 30v+ rated or there about's (opening up might confirm), 24v can be as much as 7s so should be ok.
My 2nd Swizzbee had 24v nimh cell pack and I made and used a pair of 7s lion packs without issue and could have gone as far as 8s if an appropriate BMS could have been sourced.
You will likely be clobbered for duty as well form China and may have VAT as well to pay.
For a re-cell Jimmy at ebikebatteries/BGA Reworking will be a very good call.

 

[NeilP]

Ok, yes, getting controller open to check caps and MOSFETS is priority. Am going to try and get a bike from him this week

If it were mine I’d shove 7s on and cross my fingers, but can’t really do that with a customers bike

Duty and VAT, ... thanks had forgotten that, but being in Jersey our GST rate is 5%, and no idea what an import duty might be. Our GST threshold is I think £230 for the consignment, Have to pay the GST on the total cost, including postage

Have mailed the owner to arrange bike collection next week