Charging with a cc/cv bench supply

[wireman]

I’m thinking of buying a Tenma 72-2550 bench supply in order to do partial charging of my 10s 41.8v Volt Pulse battery..I would still use the Volt charger for cell balancing from time to time.
I understand this would be okay but do I need a cut-off timer between the supply and the battery?
I have looked at the Luna smart charger but the cost of shipping (60$) and import duty and VAT/handling charges would make it rather expensive
Any advice would be welcome.

 

[vfr400]

Why do you need a timer if you're partial charging?

 

[wireman]

Why do you need a timer if you're partial charging?

I don’t know that I do. Just clarifying. I’ve just noticed the thread about tweaking the Sans charger for a partial charge. That looks interesting, and much cheaper than the Luna charger.

 

[Nealh]

The Sans mod is free and cheap esp the venting holes to dissipate heat build up. Once done the voltage pot can be trimmed as and when needed without ever opening the case again.

 

[wireman]

The Sans mod is free and cheap esp the venting holes to dissipate heat build up. Once done the voltage pot can be trimmed as and when needed without ever opening the case again.

I agree Nealh. I’ve read your post about that mod. I love that sort of thing.
It looks like the way to go.

 

[Nealh]

Over the years I have acquired a few San's and have them set up all for differing V's.
1 X 38.5v, 1 x 41v, 1 x 42v and one for 12s at 50.2v.

 

[wireman]

Over the years I have acquired a few San's and have them set up all for differing V's.
1 X 38.5v, 1 x 41v, 1 x 42v and one for 12s at 50.2v.

Well, I have just bought my first Sans 42v 3A charger. After battling to turn the ghastly little self-tappers and remove them( they won’t be going back in) I have just tweaked it down from it’s original 41.9-42v to 41.3 for now. Totally arbitrary.
My voltages are measured with two Fluke dvms (model 29 and 75) that actually agree in their readings!
To be honest, my Volt Pulse battery at three years old, only charges for 2hrs and probably needs all the charge it can get. I did an 18 mile jaunt up and down the gently climbs from Braintree to Finchingfield in Essex, but I had to put in a good effort on the climbs. I was quite sweaty afterwards. I’m 62 years old, and weigh 12.5 stone but I am a fairly strong cyclist. To be honest, I think the battery has a high internal resistance, judging from the way the voltage would sag so much from an early stage.
I’ve got one of those cheap power meters on order so I can perhaps get a figure on its actually remaining capacity.

 

[vfr400]

Charging an old saggy battery to less than 100% isn't going to end well. How are you going to ballance the cells? Have tou checker the present balance state?

 

[wireman]

Charging an old saggy battery to less than 100% isn't going to end well. How are you going to ballance the cells? Have tou checker the present balance state?

I agree. I’ve still got the original Volt (ST) charger unchanged. I’ve no idea what the state of balance of my cells is at the moment.
To be honest I see this bike and battery, only as a interim measure. At the moment, this whole ebike thing is mainly a fascinating hobby, but I am hoping to move to Shaftesbury in Dorset soon, in which case an ebike could be useful for the surrounding hills.
Maybe it wil be time for a crank drive or a Big Bear then.

 

[WheezyRider]

I agree. I’ve still got the original Volt (ST) charger unchanged. I’ve no idea what the state of balance of my cells is at the moment.
To be honest I see this bike and battery, only as a interim measure. At the moment, this whole ebike thing is mainly a fascinating hobby, but I am hoping to move to Shaftesbury in Dorset soon, in which case an ebike could be useful for the surrounding hills.
Maybe it wil be time for a crank drive or a Big Bear then.

The cold weather isn't going to help either with an old battery. Charging to less than 42V is done to help extend the life of a new or nearly new battery. For one that is on it's last legs, it's not worth the bother. Also, as vfr says, you should make sure the cells are balanced initially if you are going to charge to less than 42V.