receiver battery for open outboard

[chriscarbon]

the previous tunnel that i have been running for the past 3 years i used 2000 sub c 6 volt packs. this is what others were using however with the size of the pack it was located outside the radio box. the weight was needed up frount so it was weight put to good use. with the new hull i am working on there is room for a 4/5 6 volt pack or a aa nimh pack on the inside of the radio box. is there enough power to operate two quarter scale servos and two regular servos for this application. the charger that i have can be updated to charge the nimh. also what amperage do you charge the nimh. in other words what are you using and how are you charging. i have heard that the nimh don't like heat.

thanks

chris carboneau

 

[izitbrokeyet?]

Chris,

I charge my NIMH at around .5C (for a 2000mah pack that is 1 Amp). If you don’t have a charger with Peak detection and if you want a full charge you should discharge your battery then recharge to C (capacity) by charging at some R(rate) X T (time) = C (capacity of your cells). At .5 C you are pretty safe and don’t need to be too concerned about heat. If it’s a new set of batts you might consider a “break-in” charge of .25C with a couple of cycles. If you want to start using rates around 1C you will start to develop some heat and will have to account for heat loss in your total charging time.

Or you can do it the easy way and get a peak detection charger (I won’t do without one) hook it up and go mix a tall drink.

 

[chriscarbon]

kevin,

thanks for your reply. i am gathering that a 5 cell pack of aa 2000 mah NIMH will work for my application. a friend is going to charge my batteries while i send my charger in to have it up dated to charge the NIMH batteries.

1. initial charge .25c or .5 amp for 2 cycles.

2. the cells can be charged at .5c or 1.0 amp without hurting the cells.

note: i charge my batteries over night as a general rule but like to know how high you can charge a pack with out hurting it when you forget to plug the charger in for the boat you are going to race in the morning. i will be putting the battery pack together monday evening. i hope to test boat next weekend.

chris

 

[izitbrokeyet?]

Hi Chris,

What’s the rate of your charger?

You can figure out just how long to charge a discharged battery given the rate of the charger.

Given C=T x R (Capacity is equal to Times multiplied by rate (at low rates that dont need to account for heat))

If you want to charge at high heat rates then you'll increase your times by 10% (or multiply x 1.1)

For example:

Given Capacity of 2000 MAH and a charger that charges .250Amps (250MA)

C=TxR rewrites as T= C/R

T(time) = 2000MAH/250MA

T(time) = 8H (hours)

If you were using a rate near C then you would multiply your time x 1.1 to account for approximated heat loss.

Have fun dudes,

 

[chriscarbon]

kevin,

i have a futaba charger that came with one of my radios. the charger is one of the slow type. i checked the rates and reads as follows 9.6 - 50ma the second lead is 4.8 - 50ma. the fast charger that i use is a older tekin bc 112A charger. i can send the tekin in to have it updated to charge the NIMH batteries.

chris

 

[chriscarbon]

kevin,

the tekin charger that i have has an adjustable rate from 0 to 10.0 amp. the charger also has a charging time mode that goes from 0 to 1hour and 59 minutes.

chris

 

[izitbrokeyet?]

On the Futaba charger the rate is 50 ma. Unfortunately that Futaba charger will not charge your 5 cell pack since you need 6v to charge 5 cells (5cells x 1.2v/cell). It sounds like you’ll still be able to charge your transmitter with the Futaba charger.

It sounds like your Tekin charger is a solid charger with peak detection. If that’s the case, you just select the maximum charge rate, and it will do the rest. As long as you use a rate below C (2a for your 5 cell pack) you should be fine. At a rate near .5 C you’ll probably see the best results on your packs. Just remember that NIMH cells will need to be cycled a few times and charged gently before they start acting right.

 

[boaterbill]

Just a reminder. Do not leave NIMH batteries on trickle charge as they will start discharging. When they are fully charged take them off the charger. New pack, cycle it at least three times. My 2 cents worth.

Bill