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Use AGM Real Car 70amp 12v Battery to Field Charge ?

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Use AGM Real Car 70amp 12v Battery to Field Charge ?

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Old 08-07-2019, 12:09 PM
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Default Use AGM Real Car 70amp 12v Battery to Field Charge ?

Hello

I will travel away for two days
Tent in Nature.
I have brand new AGM 70Amp 1/1 real Car 12v Battery.
I will only use this Battery to Charge my RC Cars lipos there.

I have
with me two rc cars and couple Lipos
4pc 5000mah 2s 7.4v lipos
2pc 5000mah 3s 11.1v Lipos

I have B6 Quattro Charger.

How many times can i Charge my Lipos without Destroy the 70Amp AGM Battery?
3s will need more power than 2s ? even if they are 5000mah all ?

How to Calculate this ?

I need Charge all Four 2s lipos atleast twice
and the same with the Two 3s

Is this okey? Can i Charge them more also ?

I dont want take out all of my AGM. i will have it lasting many years.

Right now i have also Charge this AGM 70a to Max. and this is brand new. Very expensive Battery.
I did have AGM 120 amp before when i was camping longer time. That Battery got destroyed after about 6months, i was camping alot in nature before and have my RC cars with me then.
I did always charge this to bottom, untill chargers not work anymore. This was okey like 10times. then the battery died totally. I try push it with 20-50amp, nothing did help. I did kill that AGM battery.
Im little worried doing the same again.

Need help fast please.
I have multimeter is this helps and is needed also. What is the lovest voltage i can go to , and keep the AGM safe ?
I will go Camp Saturday
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Old 08-07-2019, 05:34 PM
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Deep cycle marine batteries are designed to be run down to low voltage and then recharged without issues. I don't think agm batteries are designed to work that way. For an agm battery you might want to get a solar charger to keep the agm battery topped off while camping.
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Old 08-07-2019, 06:06 PM
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a deep cycle battery is best .but you will get away with using the agm a few times. I was in a jam and used mt sealed lead acid battery for 1 event I ran 4 -2 cell lipos 5000 mah 1700 put back in each battery was charged 4 times. battery was then put back in my truck and got me home 250 miles away. lasted 3 years in truck.
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Old 08-10-2019, 10:21 AM
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hi

you have right
deep cycle batteries is better.

i did think AGM was that.
I had wrong

there are special Deep Cykle AGM batteries for boats and things. I have just normal AGM to car

okey then i will only charge out 30amps
so i have more than half left. 40 amps


how many 5000mah 3s lipos you can charge if you use 30amps, with 12v car battery,
lipo charger is one 200w lipocharger for 4 lipos , quattro b6 imax charger.
i will charge 4 pc 5000mah 3s lipos sametime.

for an example.
i like to know this

how you calculate this correct?
what is the answer?
how many packs can i charge ? use 30amps
i will charge at 5 amps. 5000mah. 3s lipos
4pc of them same time with a quttro 200w lipo charger

wish i had 12v carbattery amp meter, se how much is left after charinging once
i dont have

can this be calculated someway matematically?

please help me
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Old 08-11-2019, 07:57 PM
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All batteries including lead acid deep cycle have a capacity. It is in or can be connverted to mah. The sum of charges (in capacity) for all the batteries has to be less than the maximum recommended discharge for the lead acid, chargers arent 100% efficient so a 5000 mah battery charge might be 5150 at 30 amps or 5100 at 20 amps. Your best bet is to find a battery with the ratings or do the test and record how many batteries you can charge before dropping 1 volt and then multiply that by the difference between the minimum recommended discharge voltage and max voltage. That will tell you safe capacity and efficiency. You should probably charge higher voltage batteries before lower voltage.

For example
20000mah lead acid
(3)5000 mah lipos
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Old 08-12-2019, 08:36 AM
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Hmmmm okey

is there any way i can see how many amp my battery have left after charge 1 time ?

AMP meter to 12v car battery ?
does these exist?
something i can calibrate to 70 amp that my battery is. and then get the new amp result left out of these 70 after i charge couple lipos ?
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Old 08-12-2019, 08:12 PM
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Originally Posted by HardBash View Post
Hmmmm okey

is there any way i can see how many amp my battery have left after charge 1 time ?

AMP meter to 12v car battery ?
does these exist?
something i can calibrate to 70 amp that my battery is. and then get the new amp result left out of these 70 after i charge couple lipos ?
First do a google search and see if the mah is published. If the mah is not published look for a minimum safe voltage the battery can have without damaging it. The minimum safe voltage might not be published either but if its a deep cycle any other battery that is a deep cycle and has a recommended minimum wil apply.

I assume your charger keeps track of MAH that you use per battery charge. Do that allot of times until the voltage reaches the recommended minimum voltage and add up all of the charges to the lipos that resulted in the deep cycle reaching the minimum voltage.

Some batteries have a group code. There is published data on the group codes with generic ranges in mah. You can also use that. The longer it takes to charge the Lipo the more efficient the charge will be so once you find the minimum amps you can change at stick to that and the capacity of the deep cycle will be consistent.
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Old 08-14-2019, 11:53 AM
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Originally Posted by Bry195 View Post


First do a google search and see if the mah is published. If the mah is not published look for a minimum safe voltage the battery can have without damaging it. The minimum safe voltage might not be published either but if its a deep cycle any other battery that is a deep cycle and has a recommended minimum wil apply.

I assume your charger keeps track of MAH that you use per battery charge. Do that allot of times until the voltage reaches the recommended minimum voltage and add up all of the charges to the lipos that resulted in the deep cycle reaching the minimum voltage.

Some batteries have a group code. There is published data on the group codes with generic ranges in mah. You can also use that. The longer it takes to charge the Lipo the more efficient the charge will be so once you find the minimum amps you can change at stick to that and the capacity of the deep cycle will be consistent.
Thank you RC Friend for trying help me.
Now anyway , i dont understund nothing

What do you mean?

I AM SCANDINAVIAN
sorry
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Old 08-14-2019, 01:46 PM
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You have to calculate in Wh

70Ah x 12v = 840Wh, but when voltage will drop you are probably at 700-750Wh

5000mah 2s 7.4v lipo -> 5Ah x 8.4v = 42Wh
5000mah 3s 11.1v Lipo -> 5Ah x 12.6 = 63Wh

So every time you charge a battery it will take 42 or 63Wh you can take it off of the total available Wh.
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Old 08-14-2019, 09:40 PM
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Can't explain the math, but I'd suggest looking at a small solar panel to recharge your lead acid battery during the day. I bought an inexpensive one for a passenger car that didn't get driven much - worked well and would recharge a pretty low battery in an afternoon.
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Old 08-15-2019, 08:38 AM
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Back in the early 80's we ran onroad in the back of a strip mall. There was no electricity, so we always charged off our full size car batteries. Of course back then we were running 1200 mah nicads and we never even came close to discharging a car battery. I can't remember even one time of someone not being able to start their car at the end of a long day of racing.
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