Rechargeable batteries

[gil sonsino]

For years I've used NICD batts of all sorts of brands and sizes sucessfully in my boats with no problems .

Now I received one NIMH 4.8v 650mh and in its label there is warning saying to not use NICD chargers!

As its size it's half of conventional nicd's with double of power I inttend to substitute my old ones but would like to know what's the problem using a good NICD charger/recycler?.

I do know that this subject is more appropriate in the eletric site but would like to hear of yours experiences in this field.

Thanks

Gill

 

[ClayGlover]

Hi Gill. I believe that refers to the older NiCd-only peak-detecting chargers. Due to the different cell chemistry, the peak voltage is different (?) between nickel cadmium cells and nickel metal hydride cells. You can use a regular NiCd charger as long as you monitor the battery temps and don't let the NiMH cells get hot. I'm not a battery expert, but I think a safe NiMH charge amperage rate is .3C. In otherwords, 1/3 of the battery capacity as the charge current level. A slow charger (.1C or 1/10 capacity) for NiCd's will be fine to use on the NiMH cells, it's the higher current chargers you gotta watch out for. NiMH's hate high heat and it will reduce their life greatly. Slightly warm is fine. If you don't get them hot, you'll be OK. A benefit is they aren't supposed to have the memory buildup like NiCd's tend to have, as well as the additional capacity.

You may want to get one of the newer peak chargers available that do both NiCd and NiMH. They are a great investment.

 

[gil sonsino]

Hi Clay your input is the same I've heard from some electric airplane guys , I mean I have to follow the charging avoiding the NIMH battery to reach high temps.I have a recycler that works great but to keep trouble free I prefer to get a new dual cycler used for both types of batt's.

Thanks

Gill

 

[Joe_Knesek]

I've been using the MRC Super Brain charger on NIMH for a couple of years with great results. @ around $50.00, you can't beat this charger.

 

[Preston_Hall]

I think somebody here posted a link a while back that had pictures of what happened when a NiMH was severly over charged. It went off like a grenade. But I don't think you will have any problems, especially if you use a charger compatable with NiMH.

 

[gil sonsino]

Yes......... I had this bad experience time ago with a sealed field batt 12volts /7Amps that put my field box out in pieces and took me a day to clean all that mess hehe!.

Gill

 

[Don Ferrette]

Here's something right off the Batteries America site where I've been buying for years............

Q: What rate should a Nickel Cadmium or Nickel Metal Hydride battery be charged at?

A: The "ideal" Slow-charging rate for Ni-Cd (Nickel Cadmium) or Ni-MH (Nickel Metal Hydride) batteries is 1/10 of the rated capacity of the battery pack. If a battery pack is 700mAh in capacity, the ideal charge rate is 70mA for 12-16 hours (12 hours for "constant current" chargers - which are relatively expensive, and 16 hours for "tapering current" chargers, A.K.A. wall warts/wall cubes, which are usually low-cost). Charging Voltage should be equivalent to the # of batteries in the pack X 1.5v. A 4.8volt pack (made of 4 cells) gets charged normally at 6 volts. “Smart” chargers usually set the charge Voltage automatically; wall cubes have a pre-set output voltage, and that output can vary from product to product. Furthermore, the POLARITY of the chargers vary from product to product, so GREAT CARE must be taken to confirm that the wall charger being used is the proper item for a particular battery pack.

Batteries will usually last longer if you Slow-charge them. In fact, almost ANY rechargeable battery will last longer if you can Slow-charge them. If a battery is constantly fast-charged, it WILL be ready for use quicker, BUT it will probably wear out faster (i.e. it will lose the ability to store current; i.e. it will stop taking a charge).

http://www.mrnicd-ehyostco.com/

 

[mike]

I have been using the MRC Super Brain 959 for a season and a half, the lowest rate on it is 500 ma, but it only charges for an hour or so. There have been no ill effects so far, am now wondering if the charge rates are too high??, the trickle charge rate is 100 ma, although I usually take it off the charger as soon as it beeps.

One thing to be wary of is that charger defaults to 3 amps when the power is disconnected for a short period of time........

mike

 

[gil sonsino]

Ok I charged this NIMH pack yesterday night using my recycler at 50mha for 13hours and today checked it with a meter that showed full charge of 5,4v and the battery was slighly warm something normal after charging.

I guess this charger will fit my needs but ordered one specific for nimh batts.

Thanks for your replies.

Gill

 

[Mike G]

I charge 1650 mah NiMH's at 750 ma some packs are over 2 years old and have never given me any troubles.