trickle charging cordless batteries?

Geo-TH,In

Well-known Member
I would like to start off by saying there is a lot of info about cordless batteries. Which is the best battery, type of charger, which have memories, which don't, self discharge rates, effects of temperature. Look long enough and you will find a ton of info and you won't know what to believe anymore.

I can say first hand cold temps play havoc with both my Li-ion and Ni-MH batteries. Try to use one when it's been left in truck at 0 degrees and like other batteries they don't work well. So I've been warming them up in the house before charging.

Then I decided to do a little experiment this morning. Make a trickle charger that charges battery at 0.1% of C. Connected trickle charger to a fully charged battery on workbench in unheated barn. I'll post back in a few days with my findings. Has anyone used a trickle charger on their cordless batteries 24/7 to keep batteries up to speed in a cold environment?
trickle charging
 
(quoted from post at 12:27:37 01/18/16) I would like to start off by saying there is a lot of info about cordless batteries. Which is the best battery, type of charger, which have memories, which don't, self discharge rates, effects of temperature. Look long enough and you will find a ton of info and you won't know what to believe anymore.

I can say first hand cold temps play havoc with both my Li-ion and Ni-MH batteries. Try to use one when it's been left in truck at 0 degrees and like other batteries they don't work well. So I've been warming them up in the house before charging.

Then I decided to do a little experiment this morning. Make a trickle charger that charges battery at 0.1% of C. Connected trickle charger to a fully charged battery on workbench in unheated barn. I'll post back in a few days with my findings. Has anyone used a trickle charger on their cordless batteries 24/7 to keep batteries up to speed in a cold environment?
trickle charging
ctually, C/1000 ?
 
Well, you may keep battery charge topped off, but cold battery will still show weak output. If you are charging it enough to warm battery, you are charging way too hard and courting disaster.
 
Read the article, 3-5% of C is normal for trickle charging. I'm starting out at 0.1%, very conservative don't you think? Self discharge rate is anywhere from 1%-10% per day depending on source you read?
 
Hello Geo-TH In,

Hey George you knew I was going to chime in right?
If by trickle charging you mean to charge a discharged pack no problem. You will get get the fullest charge in your packs. HOWEVER do not trickle charge after charge is terminated! My NiCad's do just fine in the cold. Used this pack last week and this morning, 30 to 40 screws. It is in the unheated garage,

Guido.
 
Guido, did you read article about trickle charging Ni-Mh battery at 3-5% 24/7? Also self discharge rates on all Ni batteries ranging from 1-15% PER DAY? I don't see any harm charging at 0.1%. May even boost it a little at a time. Post back with findings after battery is on cold barn over night.
 
Ted in NE-OH,
Good question. 1-3% in 24 hrs, so charging at .1%/hr = 2.4% per day right? This is an experiment, be interesting to see what I find. More interesting to see if battery will work in below freezing temps tomorrow morning.
 
Hello Geo-Th,In,

No did not read the article. Common sense to me. If you charge a battery pack, at a lower rate of self discharge all is well. Unless both the above are the same though, your pack will eventually self discharge. Hard to match the discharge rate, to keep the pack at 100% capacity, with these new Lithium or Metal Hydride cells. Trickle charge is usually a slow way to charge-maintain a battery that is designed to support that way of charging. I trickle charging a pack, Usually when new cells are added, or a brand new pack. This method brings all the cell up to the same level of charge, there fore equalizing the pack as well. Fast or rapid charging a pack, will only achieve 70% charge-saturation. That is why when you trickle charge your packs you will notice an in creased run time. Trickle charging will charge-saturate the cell to the max! Again, topping off with a trickle charge after fast charge is terminated? That is a NO NO, for Lithium based cells, and Nickel Metal Hydride. as well,

Guido.
 
Hello Ted in NE-OH,

I told him too! Hard to balance gain and loss. If you loose more then you gain......

Guido.
 
Hello Geo-TH,In



Here is what you need. There are fakes out there though. That one came from SKY RC. will do 15 sub c cells.
Lithium battery as well as Lead acid. It is rated at 30 Volts 5 Amps. Available in AC or DC models. It will also rate you packs, check pack resistance and more. It can be used in conjunction with a temperature probe. Slap a timer on it and your done!

Guido.
a211874.jpg
 
Hello Geo-TH,In,

Self discharge rate has so many variables. You really should just check yours. College of hard knoks! I trickle charge at 1/14 of capacity, and time the charging so I am there towards the end of the cycle. 3000 Mah totally discharged battery will then be fully charged after the 14 hrs. If charged at a rate of 214 Mah.

Guido.
 
Guido, with out buying anything tell me how can you measure the discharge rate of cordless batteries, just use COMMON SENCE. I'll need a few more days to collect data. Post back with my simple common sense idea. Once I know discharge rate, then I can design a trickle charger.George
 
Hello Geo-TH,In,

Simply monitor voltage drop, it will show what is the self discharging rate for that pack, and hopefully the trickle charger will do the trick. I doubt it, way to many variables. The charger stops charging when peak voltage is achieved or set. each pack WILL have a different self discharging rate. each cell has a different capacity. Temperature will be a factor in the capacity. How much power draw will have an effect on run time. Way too many variables. Like I stated I would strongly advice to be there when the battery is charging, especially towards the last hours. Voltage is what I use to monitor battery state of charge.

Guido.
 
Guido - love your use of the magnets for connectors, does the coating need to be intact or is Neodymium itself electrically conductive?

I hate the way my NiMh Ryobi 1 stuff won't run or charge below 40*f

What are you building the trickle charger out of?
 
Hello gears,

No that is not me. George is on a mission I guess. I have a Lab grade power supply I can use for charging. Also the Imax works great. That is the blue thing in the picture with the magnets. I now use A 4" clamp now. The magnets are good for charging only. Recycled from a hard drive. I load test the battery cells at 6 to 8 amps each, so a thigh connection is a must, here is the clamp,

Guido.
a211943.jpg
 
I found a trickle charger won't help cold
batteries. Need to keep them warm to use
and charge. What I read and confirmed is
Both NiCe and NiMH can self discharge up to
20% in 24 hours. Within 10 days another
10%. Bottom line, NiMH can handle
recharging without worrying about memory,
unlike memory in NiCd. So I'm keepin some
batteries in house, some in trucks floor.
When I'm driving it only takes about 10
minutes on truck's charger to warm up and
top off. May take a warm battery with me to
use first.
 
Guido,
Perhaps because you don't have a dewalt smart charger that can handle all 3 types of batteries, you can't see a common scene way to tell that our Ni based batteries have a large self discharge rate, up to about 20% for the first day, 30% in 10 days. My smart charger looks at battery temp to shut off. It may also look at the voltage bump and currents. I'm not an engineer, just someone who experiments.

Well Li-ion batteries have a great shelf life, very little if any self-discharge. So if I put a charged Li-ion battery in my charger, charger will do nothing but indicate it charged. On the other hand, put a Ni-MH battery in charger after it's sat for a day, and charger goes to work.

I drained all 7 of my Ni-MH batteries to 12v using a 18v dewalt flashlight. It took all 7 batteries an average of 50 minutes to come up to full charge. My conclusion, each minute of charging time put 2% of charge in battery. So by timing how long charger works on batteries that sat over night, I found sure enough all my batteries lost between 11-22% of charge.

The battery I left outside on my trickle charger was dead because of the cold. So much for trickle charging thinking battery will work in cold. I'll admit, bad idea. Good idea is keep batteries warm and drop them in charger before you use them.

Do your NI-Cd like being topped off or do they like to be run down because of memory issues right?

As for me, I'll carry a few batteries in truck on floor to get warmed up and then top off with 12v dewalt charger while I'm driving.

So much for trickle charging, experiment was a bust.
 
Hello Geo-TH, In,

My NiCad's sit in the drill box till needed. They have a very low self discharging rate. I gave one pack away, now I have just two. As you found out,
you can either keep the pack warm, or time a charger for when you need them,

Guido.
 

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