How to determine the state of charge of a NiCD battery when charged via a Bench PSU?

Thread Starter

Rahulk70

Joined Dec 16, 2016
521
I’ve a bunch of Sanyo Cadnica cells of various capacities in my possession. Though they are a bit old they have never been used and are NOS. I’m currently trying to charge a KR-FH 7000mAh cell. As per the label on the battery(please see picture below) it says at 700mA it should be charged 14-16 hrs and at 233mA for trickle charge.

I’ve two questions:

1. Currently the battery voltage is 0.89V since it sat in storage for like 5-7 years. So, I assume I can set the bench power supply to 700mA current and voltage to 1.45V. My power supply is CV type. But what if the battery was around let’s sat 1.09V or something like that where it’s not fully discharged? I’m aware a fully discharged cell is 1.0V usually.

2. Is the tricky stage mandatory at 233mA after completing the 14-16hr charge at 700mA?

I’ve never manually charged a NiCD or NiMH cell. Only Lead Acid batteries so far. Usually the NiCD and NiMH batteries I’ve used at the AAA, AA and C type cells that have either it’s own automatic chargers. I do not have a charger for the 7,10 &20Ah cells. So manual charging is my only option for time being until I find something.

I’m hoping to get some expert opinions from you guys.
 

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Bernard

Joined Aug 7, 2008
5,788
Best guess is to review Battery University. On an old project , lightning in a bottle, I turned it upside down to see charging information; 4 AA Ni-Cd , about 800 mA hr. charge to 5.76 V @ 100 mA. It is still working & gets a charge every year or so.
 
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lotron

Joined Jan 31, 2020
1
NiCd accumulators are charged until voltage grows, because there is maximum voltage, that after reaching full charge start drop. NiCd can be overcharged. Accumulators should not be discharged under 1.1 V.
 

crutschow

Joined Mar 14, 2008
27,756
To answer your post title question, there's no way to determine the state of a NiCd battery's charge by any measurements.
 

AlbertHall

Joined Jun 4, 2014
11,506
My power supply is CV type.
Does your supply have an adjustable current limit?
You really need this for that job.
Set the current limit to 700mA and the voltage to 1.45V then the cell will be charged at 700mA until the voltage reaches 1.45V and then the charge current will reduce to keep the cell voltage constant.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
521
Does your supply have an adjustable current limit?
You really need this for that job.
Set the current limit to 700mA and the voltage to 1.45V then the cell will be charged at 700mA until the voltage reaches 1.45V and then the charge current will reduce to keep the cell voltage constant.
Yes, my supply can be set to 700mA. I’ve currently set it to 700mA and voltage to 1.45V for charging. Since the battery is fully discharged I should be able to charge it straight for 14-16 hrs.
 

andrewmm

Joined Feb 25, 2011
1,757
Can I just highlight the possible danger here,
NICads , if you are careless at charging, they can go "pop"
and fling burning Cadmium around,

Make your own charger at your own risk !
 

AlbertHall

Joined Jun 4, 2014
11,506
Can I just highlight the possible danger here,
NICads , if you are careless at charging, they can go "pop"
and fling burning Cadmium around,

Make your own charger at your own risk !
The best I have ever seen is that they blow some electrolyte out of the self-sealing vent. That wouldn't do the cell much good, but it isn't going to harm bystanders.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
521
The best I have ever seen is that they blow some electrolyte out of the self-sealing vent. That wouldn't do the cell much good, but it isn't going to harm bystanders.
Usually NiCd’s are good at absorbing over charge and don’t heat up that quickly like an NiMH. From what I’ve read NiMH tends to blow up if overcharged as the reaction is exothermic, while the former is endothermic. Mostly I would be really worried about blowing up only in smaller cells like AAA and AA. The bigger ones would take a lot to blow up, especially like the ones I’m using above which is twice the size of a D size cell.
 
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Thread Starter

Rahulk70

Joined Dec 16, 2016
521
I have seen vents/caps blown a few feet and quite hot.
Well on such a large cell the likelihood of it blowing up is quite less if charged at the rated 700mA unless left on charging for more than 24 hours. Of course things would be different if I attempted to fast charge it at 1A or more.
 
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