Question for EE, how much of a difference is there between 600 mAh and 800 mAh?

[sillymofo]

I forgot what the formular was, but this is to calculate full charge time for rechargeable batteries.

 

[Splork]

Sorry, I couldn't resist...

200 mAh

-sp

 

[SpazzyChicken]

Originally posted by: Splork
Sorry, I couldn't resist...

200 mAh

-sp

Rimshot........

 

[amoeba]

I am EE and I don't understand the question......

 

[FoBoT]

you don't need an EE to do basic arithmetic :frown:

 

[amoeba]

The charge time should be linear.....thus the 800mA should charge it 8/6 or 33% faster

 

[sillymofo]

Originally posted by: amoeba
The charge time should be linear.....thus the 800mA should charge it 8/6 or 33% faster

Some one paid attention in school, thank you amoeba. Do you happen to know the formular so I don't have to ask this question again? I know the diffences won't do any damages.

 

[Chumpman]

Originally posted by: cr4zymofo

Originally posted by: amoeba
The charge time should be linear.....thus the 800mA should charge it 8/6 or 33% faster

Some one paid attention in school, thank you amoeba. Do you happen to know the formular so I don't have to ask this question again? I know the diffences won't do any damages.

Yeah they paid attention in pre-algebra

 

[ClueLis]

Originally posted by: cr4zymofo

Originally posted by: amoeba
The charge time should be linear.....thus the 800mA should charge it 8/6 or 33% faster

Some one paid attention in school, thank you amoeba. Do you happen to know the formular so I don't have to ask this question again? I know the diffences won't do any damages.

He did say the charge time was linear, that should be enough for you.

 

[amoeba]

I still think you aren't being too clear on what you are asking. And the difference would do damage. If a part is designed for only so much current, and you send a higher than expected current through, it could burn circuit elements.

 

[KMurphy]

Charge time is most definitely not linear.

The initial charge for a dead battery is known as the "bulk charging" phase and is mainly dependant on the supply side current delivery. From there, current drops down exponentially untill it reaches the float charge level which is enough to feed the recombination cycle.

The difference in charge time between 600-800mAh batteries will be negligable. If you are keeping the same charger, there won't be any issues.

 

[KMurphy]

Originally posted by: amoeba
I still think you aren't being too clear on what you are asking. And the difference would do damage. If a part is designed for only so much current, and you send a higher than expected current through, it could burn circuit elements.

This is not true. You can't send a device more current than it will accept. All he has to worry about is if the voltage is the same. The load will draw the same current regardless of battery capacity as long as it is the same cell type/number/configuration (voltage).

 

[silverpig]

Doesn't it also depend on the type of battery? I've seen current curves for all different types of batteries and they're certainly not the same.

 

[KMurphy]

Yes, it does depend on battery type. NiMH, Li, NiCad, etc. have different voltage per cell. The original poster needs to post the two cell types, charger type and application. I assume from the original post, the only difference was going to a larger capacity.

 

[Ameesh]

depends on the battery, the batteries you are using conform to a formula fitting arctan(x) + ln(x)^-1

good luck figuring out when to take them off the charger! <evil>bwahahahahahha</evil>

 

[MrDudeMan]

Originally posted by: Ameesh
depends on the battery, the batteries you are using conform to a formula fitting arctan(x) + ln(x)^-1

good luck figuring out when to take them off the charger! <evil>bwahahahahahha</evil>

that is why good chargers trickle charge

and the charge time is most definitley NOT linear. my PPC charges from 0-85% in a matter of 20-30 minutes, and another 10 minutes to go from 86-100%. the best RC car batteries (4400mAh) charging at 4 amps while charge almost as fast as an 1100mAh at 2 amps. do the math.

 

[sillymofo]

Originally posted by: KMurphy
Yes, it does depend on battery type. NiMH, Li, NiCad, etc. have different voltage per cell. The original poster needs to post the two cell types, charger type and application. I assume from the original post, the only difference was going to a larger capacity.

The battery is the same (12 V Lead Acid, motocycle battery for my R/C starter). The intended charger was 12V, 600 mAh. I have made some home made chargers for my NiMH battery pack and it worked fine (using a Radio Shack selectable transformer, which output current is 12V, 800 mAh), and I'm planning to use the same transformer for the Lead Acid battery. If it's linear charging, then it just a matter of simple mathematics.

 

[MrDudeMan]

Originally posted by: amoeba
I still think you aren't being too clear on what you are asking. And the difference would do damage. If a part is designed for only so much current, and you send a higher than expected current through, it could burn circuit elements.

you are full of sh!t if you think we are to believe you are EE. but if you are, then make note for all the graduating seniors to not go to your school for that program. really? you think by putting a bigger battery on something it will overdraw current and fry it?

ever heard of a resistor? you think you could put different types of battery in an automobile if one would fry it because it has a higher capacity? i dont think so. let me guess, i am a moron and dont know what im talking about?

sorry to sound rude, but dont fill peoples minds with garbage if you dont have a clue.

 

[sillymofo]

Originally posted by: MrDudeMan

Originally posted by: amoeba I still think you aren't being too clear on what you are asking. And the difference would do damage. If a part is designed for only so much current, and you send a higher than expected current through, it could burn circuit elements.

you are full of sh!t if you think we are to believe you are EE. but if you are, then make note for all the graduating seniors to not go to your school for that program. really? you think by putting a bigger battery on something it will overdraw current and fry it?

ever heard of a resistor? you think you could put different types of battery in an automobile if one would fry it because it has a higher capacity? i dont think so. let me guess, i am a moron and dont know what im talking about? sorry to sound rude, but dont fill peoples minds with garbage if you dont have a clue.

Thanks... but I'm also aware of the resistors...

 

[MrDudeMan]

Originally posted by: cr4zymofo

Originally posted by: KMurphy
Yes, it does depend on battery type. NiMH, Li, NiCad, etc. have different voltage per cell. The original poster needs to post the two cell types, charger type and application. I assume from the original post, the only difference was going to a larger capacity.

The battery is the same (12 V Lead Acid, motocycle battery for my R/C starter). The intended charger was 12V, 600 mAh. I have made some home made chargers for my NiMH battery pack and it worked fine (using a Radio Shack selectable transformer, which output current is 12V, 800 mAh), and I'm planning to use the same transformer for the Lead Acid battery. If it's linear charging, then it just a matter of simple mathematics.

what type of RC car do you have? i have used several kinds of 12v batteries, but i just ended up buying a real car battery lol.

do you do onroad or offroad racing? not sure how into the hobby you are, but i assume you have something better than a POS radio shack or walmart RC car...something like traxxas, hpi, team associated, etc.

 

[Gibson486]

Originally posted by: cr4zymofo

Originally posted by: MrDudeMan

Originally posted by: amoeba I still think you aren't being too clear on what you are asking. And the difference would do damage. If a part is designed for only so much current, and you send a higher than expected current through, it could burn circuit elements.

you are full of sh!t if you think we are to believe you are EE. but if you are, then make note for all the graduating seniors to not go to your school for that program. really? you think by putting a bigger battery on something it will overdraw current and fry it?

ever heard of a resistor? you think you could put different types of battery in an automobile if one would fry it because it has a higher capacity? i dont think so. let me guess, i am a moron and dont know what im talking about? sorry to sound rude, but dont fill peoples minds with garbage if you dont have a clue.

Thanks... but I'm also aware of the resistors...

I am only in my third week of circuits and i even agree with MrDudeMan

 

[KMurphy]

Originally posted by: cr4zymofo

Originally posted by: KMurphy
Yes, it does depend on battery type. NiMH, Li, NiCad, etc. have different voltage per cell. The original poster needs to post the two cell types, charger type and application. I assume from the original post, the only difference was going to a larger capacity.

The battery is the same (12 V Lead Acid, motocycle battery for my R/C starter). The intended charger was 12V, 600 mAh. I have made some home made chargers for my NiMH battery pack and it worked fine (using a Radio Shack selectable transformer, which output current is 12V, 800 mAh), and I'm planning to use the same transformer for the Lead Acid battery. If it's linear charging, then it just a matter of simple mathematics.

Charging time is NOT linear (3rd time in this thread)

A 12V lead-acid battery charges at ~14V. Not much will happen if you try to charge it with 12V.

The mAh rating of the small DC power supply you mention is it's maximum current supplying capability; not what is injected into DC devices powered from it. That will not be an effective charger for many reasons. There is a lot more to this than what's in my post, but my advice to you is to buy small trickle charger for marine batteries (trolling motor).

If you try to bump the voltage on your DC supply to 15 or more volts, you will blow it's internal fuse at the very least. You could blow the battery up if you try to charge it with a supply with balls. Please buy the right tool for the job.

 

[sillymofo]

Originally posted by: MrDudeMan

Originally posted by: cr4zymofo

Originally posted by: KMurphy Yes, it does depend on battery type. NiMH, Li, NiCad, etc. have different voltage per cell. The original poster needs to post the two cell types, charger type and application. I assume from the original post, the only difference was going to a larger capacity.

The battery is the same (12 V Lead Acid, motocycle battery for my R/C starter). The intended charger was 12V, 600 mAh. I have made some home made chargers for my NiMH battery pack and it worked fine (using a Radio Shack selectable transformer, which output current is 12V, 800 mAh), and I'm planning to use the same transformer for the Lead Acid battery. If it's linear charging, then it just a matter of simple mathematics.

what type of RC car do you have? i have used several kinds of 12v batteries, but i just ended up buying a real car battery lol. do you do onroad or offroad racing? not sure how into the hobby you are, but i assume you have something better than a POS radio shack or walmart RC car...something like traxxas, hpi, team associated, etc.

I do on road competitive R/C 10 scale racing, I used to run HPI (my first cars), and had a Serpent 705 (crashed, eBayed <- officially a verb ). I'm thinking of getting the new R-40 from HPI, considering costs and maintenance, if not probably the 710 from Serpent (yikes, parts cost). The battery is for the starter.

 

[sillymofo]

Thanks for all answers, I think I got it, spend some money on a charger.

 

[KMurphy]

Originally posted by: cr4zymofo
Thanks for all answers, I think I got it, spend some money on a charger.

Thanks. Just FYI, I am a EE too.