Fungus Prevention : Low Cost Dry Storage With Mini Dehumidifier

[Hardwarezone]

Mini dehumidifier cost about $16 online.
Most buyers incorrectly use at open space bathroom or bedroom , fully saturated in 1-2 days.

Visible silica gel beads go from orange , purple grape , greenish , pinkish , transparent.
The internal heater element runs about 3/4 the length , no heat injury to fingers as it feels like full boil egg.

On the first heating recharge session it took 5 hours to fully dry it back to bright orange.
For cool down it took 3 hours in the covered steel pot for cool until room temp.

First problem was this freshly recharged device too strong for the dry cabinet.
Running into the low 30s % RH , had to open the cabinet door a few times per day to exchange humid air in.
Lower isn't better , too low into 20% or less RH can cause adhesive / lubricant / paint coating to detach.

Next recharge sessions I tried heating 2.5 hour and it was sufficient. Cool down times remain fixed at 3 hour.
Cycle between 50% to 40% RH measured at the lowest corner of dry cabinet. The cabinet's built-in digital hygrometer takes reading at top which is 7% lower.


Charging in unwanted steel pot to insulate the heat



green to bright orange after 5 hours



cool down horizontally in the pot for 3 hours , put a pot lid to stop air exchange



The heating session consume about 22 watt for most of the duration and gradually lower to 18 watt at 5 hour.
No auto-cutoff function.
Electronic dry cabinet runs at 3 watt normally to hit 45% RH and 0.5 watt when lowest setting to only run the hygrometer display.



At this scenario I tried to simulate a storage tub holding a 6 inch SCT OTA (17.5cm diameter) , used a dummy 20cm diameter cylinder.
My green plastic tub's internal size cannot fit 8" SCT. With 6" SCT there may be 2 to 4cm leftover in Length.
Tub's edges are terrible with open gaps on the top lid as it wasn't designed to be airtight seal.

After 2 run ending at approximately 10-11 days each, I received a bigger airtight tub with silicone o-ring seal to test 3rd time.

Conclusion : normal tub lid unsuitable with air gap leak , viable low cost drybox or plastic bag solution if airtight.

green tub with gap at lid edges


airtight tub , listed as 80L with 63.5cm external , I measured 53cm internal length.




28% RH climb to 51% over 65 days


Did another test on a cracked tub that I repaired , brand new fresh dehumidifier + 5 hours heat recharge
It drop to less than 10% RH overnight. Verified with digital and analog hygrometer , drop 65 to 25% rh within first 3 hours.
This is too dry and potentially cause damage.

[Hardwarezone]

From S____e online shopping platform , price vary widely as different seller like to chop carrot on the odd desperate buyer.

For local option can buy from the JiJi brand , airtight - big - affordable mid $20s , but the seal ring is EVA foam not silicone. I got rid of many eva foam stuff in my home since they start to breakdown little particles when nearly 10yr old.

[Hardwarezone]

Updates after 5 months of usage of the airtight plastic tubs.
Works ok , bouncing between 40 to 50% RH. More usage = more recharge effort.

Bought the 40L Hercules tub from local brand Citylife. Available on shopping platform S____ and L_____
Not an advertisement post , I paid full price for my items.
Internal length 42cm x 31cm width. Bottom is flat without raised wheels so it get more support from the floor for heavier item.
Can stack ontop but cannot nest multiple within each other when unused storage. Vertical walls.
I recommend disassemble the silicone O-ring and wash everything with soapy water to remove any manufacturing oil.
Initially the O-ring tend to drop out , weeks after it's holding fine inside the groove.
4 side latches flip flop around block lid closure on single try , minor annoyance. 2 Bigger latches no issue.

Performance of this 40L tub is roughly the same as the above reviewed 80L tub , difference is November month much more rain than March-April.
Without opening the 40L tub , 25% climb to 40% RH takes 20 days.

Sold in 1 , 2 , 3 quantity. The 2pack is the most value. After stacking coupon and "app points" it's possible to get the Hercules 40L tub under $10 each.
I suggest skip the 26L smaller size unless you only use binoculars.

The $2 plastic hygrometer can be adjusted with a flat screwdriver at the rear opening. Take it out of a well referenced dry box and quickly adjust in 1 stroke. I received a few that were off by 15-25%.

[Hardwarezone]

Did a search just now and was surprised this xiaomi deerma mini dehumidifier have been discontinued by the handful of parallel import sellers at $15 price range. Only the official lazada channel is selling it at $21.

I bought the $6 bottle of orange silica gel (470grams net weight) to DIY a beanbag with a towel or sock as additional drying mass to reduce the heat drying frequency. Haven't done it yet , just future plans. Will attempt to heat the DIY beanbag by placing it ontop or wrap around the mini dehumidifier.
The mini dehumidifier weighs about 600+ grams and I estimate there is about 400-500grams of silica gel beads inside , the price difference is the convenience of heating element and casing as a finished product.
In mid 2024 I increased the heating duration from usual 4-5 hours to 7-9 hours and it works better as more residual moisture is expelled from the silica gel , increasing it's effectiveness and extend the heat recharge interval. Do note to not run heating device unattended as fire hazard.

For the above mentioned Hercules 40L tubs , I knew earlier the seller discontinued the 2 pack value combo and only sell 1 or 3 quantity , price quite steep compared to normal generic plastic tub without silicone seal.
There is a bigger 55L size currently at $5 more. https://s.lazada.sg/s.1gNnq?cc
Estimated internal length at 51-52cm , this may fit C8 sct or maksutov 6. Caution the plastic floor is thin , better to lay flat sheet support material for heavy items with small footprint if the tub is to be lifted.

Through my usage of the 40L version , I noticed improvement when additional weight or another tub is stacked ontop to press down on the silicone seal.
I have a scope tub with 2 mini dehumidifiers inside , stacked another accessory tub 4kg ontop , it went very slow from 25% RH to 40% at 100 days until I had to use the scope and interrupt the record. The default clamping power alone have air leakage.
With caution as the plastic and silicone may deform or damage under excessive weight.

For tubs without added weight ontop, I use plastic dust cover with elastic loop to extend the shield against indoor airflow hitting the lid and silicone seal.
It looks similar to shower cap and is a disposable product meant to cover aircon unit during renovation.

My dry cabinet finally broke down at the 11 year mark and fully transitioned to these silica gel products.
It was powered-on around 9 years throughout it's life. No light response on the internal module or hygrometer LCD screen , I assume it's the power supply failure. There was high pitch coil whine during the final year.

The $2 analog hygrometer have around 15% deviation between each other when I bought 3 pieces more. I placed them into the dry cabinet to take reference from 1 specific older hygrometer , after 4 tries at taking them out quickly to tune the rear slot with screwdriver I was able to get the 3 pieces to move in unison. There remains a 5% gap or responsiveness delay compared to the older hygrometer.

Found this replacement mini dehumidifier , around same price only 10% less weight. Select collection point for free shipping.
This same seller used to parallel import the xiaomi deerma design.

[akdwivedi]

Thanks for sharing. This is very important in our weather conditions.

How do you heat silica gels, can we use microwave oven. I m thinking of getting silica gel and just heat them every month.

[Hardwarezone]

Thanks for sharing. This is very important in our weather conditions.

How do you heat silica gels, can we use microwave oven. I m thinking of getting silica gel and just heat them every month.

I have not attempted to heat my raw silica gel beads yet. No experience.
My original plan to piggyback it ontop my heating mini dehumidifier cannot proceed as it have "do not cover vent" warning.
I will eventually (years later) heat it in unwanted electric water kettle with thermo knob at lowest or try those $9 small electric pot for cooking 1 pax instant noodle.
Silica gel beads can split open if the temperature stress is too rapid.
Pan-fry on low heat might be OK according to some online webpage.

The blue/orange type was more common until the bad press about the blue dye being carcinogenic and shouldn't be heated in kitchen microwaves or heating oven.
Green/orange dye type is common now and only about $1 increase per bottle. About carcinogen most online webpage are OK with green dye , some still call it unsafe.