String Winder ?
Aug 11, 2018 9:22:46 GMT
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Pickers Ditch and lonelyjelly like this
Post by Stevie on Aug 11, 2018 9:22:46 GMT
Apologies for what follows...
"Batteries". Whoa!
There are many issues surrounding Li-ion. Both over charging and letting the charge decrease too much both lead to cell damage and in the worst case, fire which does not need oxygen for sustenance. Just ask Boeing with their Dreamliner fires. (The Boeing BarBeQue!)
That said, we all use these lithium batteries in our 'phones, but that's partly due to the fact that they are single celled power sources (3.7 volts) and not batteries. With single cells you only need to monitor the voltage. With battery packs you need in addition to control balance between the cells which is a whole other issue. Whilst companies such as Makita have the whole lithium thing well under control, I would encourage further investigation before going for lithium battery packs. Motors in string winders are likely to need more than the 3.7 volts that a single lithium cell provides.
Generalisations:
NiMh cells are not as good as NiCad in energy density.
The so called memory effect is nonsense. "Memory effect" problems are more likely to be related to one or more cells in a pack being dragged reverse voltage by the other stronger cells as you deplete them.
I have found that old Mil Spec NiCads (with the arrow insignia) are extremely robust.
The self discharge phenomenon affects all cells to one degree or another, whatever the chemistry.
Murphy's law:- rechargeables will be flat when you need them!
If you want to go rechargeable AND only use them very infrequently, I would suggest going for Sanyo "Eneloop" (or equivalents from Sony and others.) I think they're NiMh based technology. The latest ones will retain a good 85-90% of their charge after twelve months of storage or non-use.
If you must go for lithium, give strong consideration to LiFePo4 cells which alleviate many of the fire risks at the small price of a little reduced power density over LiPo cells and slightly higher initial cost.
I apologise for the post, but there are issues surrounding the deployment of Lithium cells. I keep my allegedly lower risk LiFePo4 pack in flame proof charging bags inside an old German ammunition box. I take no chances!
e&oe...
"Batteries". Whoa!
There are many issues surrounding Li-ion. Both over charging and letting the charge decrease too much both lead to cell damage and in the worst case, fire which does not need oxygen for sustenance. Just ask Boeing with their Dreamliner fires. (The Boeing BarBeQue!)
That said, we all use these lithium batteries in our 'phones, but that's partly due to the fact that they are single celled power sources (3.7 volts) and not batteries. With single cells you only need to monitor the voltage. With battery packs you need in addition to control balance between the cells which is a whole other issue. Whilst companies such as Makita have the whole lithium thing well under control, I would encourage further investigation before going for lithium battery packs. Motors in string winders are likely to need more than the 3.7 volts that a single lithium cell provides.
Generalisations:
NiMh cells are not as good as NiCad in energy density.
The so called memory effect is nonsense. "Memory effect" problems are more likely to be related to one or more cells in a pack being dragged reverse voltage by the other stronger cells as you deplete them.
I have found that old Mil Spec NiCads (with the arrow insignia) are extremely robust.
The self discharge phenomenon affects all cells to one degree or another, whatever the chemistry.
Murphy's law:- rechargeables will be flat when you need them!
If you want to go rechargeable AND only use them very infrequently, I would suggest going for Sanyo "Eneloop" (or equivalents from Sony and others.) I think they're NiMh based technology. The latest ones will retain a good 85-90% of their charge after twelve months of storage or non-use.
If you must go for lithium, give strong consideration to LiFePo4 cells which alleviate many of the fire risks at the small price of a little reduced power density over LiPo cells and slightly higher initial cost.
I apologise for the post, but there are issues surrounding the deployment of Lithium cells. I keep my allegedly lower risk LiFePo4 pack in flame proof charging bags inside an old German ammunition box. I take no chances!
e&oe...