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I have bought a battery charge up board as here. It provides two modes on the EN pin:

1) ground EN pin, the board will charge up the battery from 5V charge source only.

2) float EN pin, the board will charge up the battery from 5V charge source and the battery will drain (provide power) at the same time.

Now, I would like to use this board as a UPS. I have connect a relay at the EN pin, when there is electricity at the 5V charge source, the relay switches to GND. When there is no electricity at the 5V charge source, the relay switches to float.

However, the relay uses a split second to switch from one side to another, making the devices restart at the split second.

Anyway I can switch the EN pin without interrupting the devices? Thanks!

EDIT: I'm powering boards like Ardruino, 5V input, max. 2A

MW_hk
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  • How tolerant of voltage changes is the device your're powering and what sort of current does it draw? – PeterJ Jun 07 '14 at 03:00
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    And how long an interruption can it tolerate? – Ignacio Vazquez-Abrams Jun 07 '14 at 03:25
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    Also, why can't you just leave it enabled all the time? – Ignacio Vazquez-Abrams Jun 07 '14 at 03:35
  • Could you use a better relay? Could you put another battery (with the correct protection) on the device to power side so that when the relay switches that your device will be powered by the battery for a split second? – Kinnectus Jun 08 '14 at 21:31
  • @Ignacio Vazquez-Abrams : Draining and charging the battery the whole time, would that reduce the battery's life span? I'm hoping to use it for at least 2 years.... – MW_hk Jun 09 '14 at 01:13
  • @Big Chris : I need to charge up the battery after it has been used.... – MW_hk Jun 09 '14 at 01:14
  • http://electronics.stackexchange.com/questions/113243/charging-li-ion-batteries-while-having-a-discharge – Ignacio Vazquez-Abrams Jun 09 '14 at 01:40
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    Also: http://electronics.stackexchange.com/questions/112963/charge-a-lipo-with-only-constant-current-stage – Ignacio Vazquez-Abrams Jun 09 '14 at 01:41
  • According to the second article by Ignacio, you can keep the battery charging pretty much indefinitely if you don't charge it to its maximum voltage. You could use this to make a simple circuit where you could use a li-ion battery to provide charge to your circuit during the relay split-second propagation delay. What I'm trying to get at is that because you have some time where power is cut you need to either use a faster relay or have an alternative supply to continue providing power, such as another battery or a large capacitor that drains slowly, but provides enough current at the same time – Kinnectus Jun 09 '14 at 05:58
  • @IgnacioVazquez-Abrams I think I will leave it enable all the time, thanks! – MW_hk Jun 16 '14 at 01:34

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