Can one battery charge another one

Hi Uche,


I'm a master power electronics engineer and I specialize in DC-DC converters, solar charge converters, DC-AC Inverters, Power Supplies, and battery chargers. Yes, you can charge a battery from another battery, if that's what you're asking. I don't know why you need it isolated. However, I've got to agree with D2113F with reference to your other replies to this post. To me, it sounds like a perpetual motion machine wheras you have two batteries that are each connected to relays that can switch the individual batteries to either a load or to a a charging circuit fed by the other battery. Here is the problem. Battery-1 is connected to a load and is discharged to the point that you want to rechage it from the other battery that's been idle. Battery-2 recharges Battery-1 thru a dc-dc converter with a control to ensure that it's not overcharged. Now, Battery-2 is discharged and Battery-1 is charged, therefore, the relay or relays setup the circuit such that Battery-1 recharges Battery-2 and now Battery-1 is again discharged. Hopefully, you see where I'm going with this. It's an (almost) endless loop of the batteries charging and discharging each other. And if you powered a load first, discharging Battery-1, then recharged it with Battery-2, Battery-2 is now discharged and you can power the load only one more time with Battery-1. But now, you can no longer recharge Battery-1 with Battery-2 since Battery-2 is discharged, The only way around this is if you have some additional power from another Battery, or a Solar Cell, or from an AC-DC Power Supply to put the lost energy back into the system.


One of the first things you should have learned in physics is that there is no such thing as a perpetual motion machine. Since you used the energy in Battery-1 to power the load and the energy in Battery-2 to recharge Battery-1, and since you used-up the energy in Battery-1 again powering the load after the recharge, you are out of energy as both Battery-1 and Battery-2 are discharged. Does this make any sense to you? I hope so, but if not, please feel free to reply here or send me a message using the Element-14 internal messaging system.


Best regards,

Kamran Kazem

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