20 Ah Battery for low power application at 5-6v

Thread Starter

Edwarddim

Joined May 2, 2019
2
Hi,

I feel this should be an easy problem but I haven't found anything.

I am using an ESP32 in a remote application and it needs to last 5 years and to do this I need to utilize the sleep mode which uses 20 micro amps. I have a D-cell battery of 20 Ah but it is 3.7V and I need 5-6V for the PCB I am using. I can't use a step down because it will use at least 1mA during sleep mode.

Does anyone know of a high capacity battery option for 5-6V? I only have room for a d-cell battery or maybe at a squeeze 2 d-cells.
 

Thread Starter

Edwarddim

Joined May 2, 2019
2
Primary Lithium cells are the usual choice for that sort of thing. I can’t be sure fo your calculations concerning total life but if anything is going to work, these are it: https://www.batteryspace.com/primary-lithium-thionyl-chloride-battery-d-size-3-6v-19-ah-er34615-saft-lsh20-non-rechargeable-68-4wh-200ma-rate-un-38-3-passed-5-7.aspx
That is precisely the battery that I have. Problem is that it doesn't quite run on 3.6V and 7.2V is too high if I had 2 in series. If I use a step up or step down because that uses at least 1mA during sleep.
 

Yaakov

Joined Jan 27, 2019
1,612
You are going to have to change your specifications in some way. You are up against the physical limitations of battery chemistries.

You might be able to create a clever circuit that uses a secondary battery to manage the sleep-wake operation based on something like a supercap that charges from the main cells, and a buck converter that is turned on by the sleep-wake management only when needed.
 
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