### Author Topic: Help with modifying a Li-Po charging circuit.  (Read 512 times)

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#### WesBur13

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##### Help with modifying a Li-Po charging circuit.
« on: January 06, 2017, 04:13:35 am »
So I have a single cell lithium polymer charger called the Hitec x4. The thing works like a dream and charges at up to 1 watt, but only does Li-Po. I am looking to switching to lithium high voltage batteries. The only difference charging wise is Li-Po batteries charge to 4.20v and Li-HV charge to 4.35v. There are no Li-HV chargers that work like the Hitec x4.

So here is the real question, could I possibly use resistors to trick the charger into thinking 4.35v = 4.20v? I would never get close to the 1 watt limit, but would I be able to charge the battery using the voltage divider?

#### vealmike

• Regular Contributor
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##### Re: Help with modifying a Li-Po charging circuit.
« Reply #1 on: January 06, 2017, 08:56:39 am »
No, you won't be able to use resistors to trick your charger.

There is nothing wrong with charging a Li-ion to a lower voltage than it's maximum fully charged voltage. You won't loose much capacity by terminating charge .15V early. You'll also extend the life of the cell, especially if the cell is left fully charged for long periods.

You need to check a few things to see if your charger is compatible with your cell.

1/ Trickle charge current for a fully discharged cell. Charger must be =< Cell maximum.
2/ Charger Change over point from trickle charge to constant current. Charger change over V must be >= cell requirement.
3/ Charger constant current must be =< Cell maximum charge current.
4/ Charger termination voltage must be <= Cell maximum voltage.

Smf