Possible to charge one battery to another battery?

Generaly you can charge "empty" battery with the same "full" one.

But question is not about empty (or discharged) battery against full (or fully carged) battery.
You write: "if in our one battery dead" - if you mean empty (or discharged) then you can. Even you do not need charger or any electronics in betwen two batteries. You connect those batteries and energy will flow itself. Only you need to control  when current isstill flowing fron new to old... If it stops, you need to disconnect - chcrging would not be possible anymore. At that time you need to charge your new one to be able give energy to old one.

Efficiency will not be good, but you can. More effective way is to replace one battery (empty one) with another (full one). Is it possible to physically change them?
Hovewer different situation is if the battery is really dead. Then it will not work. Old dead battery would not be able to recieve any energy, and then you cannot charge it in any way. Then replacement is only way.

Easy way is imagine it as two bottles: full one is able filling empty one. But any full one is not able fill broken (dead) one.

Hello Pavel Simon,

Thank you for your reply!!!!!

"The requirement is if in our one battery dead then we might be not able to connect charger because we don't have AC plug at all places."

Ans:- the fully dead means  battery voltage is  23 V or 20 V and already integrated BMS circuit inside

Que:- my question is would need any isolate or protection circuit need between two batteries?

for an emergency - no, but you need to control energy flow...

for regular use - of course, yes

so many other details are there:

1. are there load in the process?

2. any "strange" condition - humidity, temperature (high,low), ... - involved?

3. value of devices in load?

All of them is important in an estimate of protection. But really general are two rows of the beginning of this answer.

A good system would not attempt to charge the empty or failed battery  from the back up battery(which will always waste energy and in the case of a failed main battery will not work at all).

You should arrange a system to switch from the main battery to the back up battery when required.

Since your system is using a main battery with 5.6MJ capacity you need to get this circuit designed by someone who knows what they are doing  - ie who has experience and test equipment etc.

A 7s24p lithium ion battery is a serious bomb waiting for an excuse to explode and must be treated with due respect !

What is the application of this system ?

MK

hardik.jani you are trying to swim upstream, it really doesn't work well. Case in point take my Smartphone and the battery pack. When I notice that the cellphone is at 50% I hook the small battery to the phone but that only prolongs the fact that the charger will lose power while the phone loses power. LOL

Try this get a 12-volt car battery and run an inverter off it. This will work for a long time. then recharge the car battery.1667.contentimage_3.png

Hello All,

Thanks for your reply.

Let me clear more details. Basically we have made AGV for industrial application and it has 60Ah li-ion battery.

So Thought point behind this requirement is some how battery dead or Under voltage protection is active because protection circuit and battery not able to provide power to our load. (This will be worst case scenario)

at this situation we would like to have one battery in other word power bank that can transfer power to our main battery.

Apart from Protection in our main battery we have BMS and it have enough protections.

Pavel.Simon Load will be disconnect during this charging mode.

Hope you all understand our requirement.

Hi Hardik,

What you describe is possible. We use a technique like this everyday when we use a backup battery to recharge our cell phones. In the case of a cell phone charger there is a DC to Dc converter circuit that takes the backup battery voltage and boosts it up to a charging level voltage for the cell phone battery.

One of the problems with this technique is that we are dealing with quantities of energy and efficiencies of transfer that limit what can be done. If you have two batteries of equal energy (mAhr rating) it will be impossible to transfer a full charge to a depleted battery from the backup. The fact that there are losses of energy in the transfer as well as the limitation on how much energy can be removed from a battery before its voltage drops below a usable level creates this limitation.

If you were able to swap the identical batteries as suggested by Michael you would have 100% of the available energy in the new charged battery to use. If you use a converter to produce a charging level voltage and use the backup battery to recharge the origin you will get some percentage, perhaps 60% of the backup battery energy back into the original battery. If possible swapping batteries is the best method.

The other possibility is to bring a backup battery with 2 or three times the mAhr rating of your original battery and this with the use of a converter to raise the voltage to a charging level will allow you to fully charge your original battery.

John

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