DIY Solar Charger Battery Inverter Box

[Ian]

I got a good deal on a 100W solar panel and 3000W full wave sine inverter a few months ago, so thought it may be fun to build a DIY portable power bank. I could do with something that could provide mains power when camping or using the telescope outside, so it does have some practical use as well as being really fun .

I've mostly build an aluminium frame with plywood panels, here's a quick CAD drawing of the trolley without the panels attached. You can see the reinforced base for a 100aH deep cycle gel battery, plus a 2nd level for the 3000W inverter. There's a hinge opening on the front to access the inverter plug sockets, plus 2 handles on the top to help manoeuvre it. All of the other areas will be enclosed with 6mm plywood (painted grey):

Here's the actual build so far (partially deconstructed!):

I've got a battery meter (that uses a shunt resistor), some 25mm&35mm cable, indicator LEDs, isolator switch and several USB sockets. I'll get a panel attached to the top that will include all of the switches and displays.

I was wondering if anyone had thoughts on wiring considerations for this build. My thinking was as follows:

• Battery is full isolated via isolator switch - can't be charged, power the inverter or any of the smaller displays without being enabled.
• Shunt battery meter to get active voltage reading under load (always active so I can monitor for undervoltage)
• 2 x MC4 solar connectors with 1m cables bundled behind panel, so that I can quickly charge battery from solar panel/controller.
• Backup mains charger for keeping battery topped up over winter
• 100A fuse after isolator switch (lower than max inverter output, but I never want to go anymore than half load as I'll be using mixed inductive/resistive loads).

If anyone has any thoughts on something I should implement, please do let me know .

 

[He who knows]

Some pretty generic suggestions:

Verify that it really is a true sine-wave inverter.

Use tri-rated fine stranded cable for resistance to vibration damage.

Use an intelligent battery charger such as a Ctek. Not cheap, but not as expensive as a new battery.

Don't rely on just one fuse on the output side of the inverter - also use MCBs on each, or each group of, outlets.



Can I ask what framing system you've used, and how you rate it? I'm looking for something to use to make pull-out storage racks under my stairs.

 

[Retired]

Hi,

Looking good Ian.

The only thing springing to mind was preventing battery overcharging but He who knows has already beaten me to it. Good look.

Kind regards, Colin W.

 

[Ian]

Thanks for the comments folks .

Yep, it's a true sine-wave inverter (bargain from ebay) and I've got some good flexible cables for the chassis . I went for a "noco" intelligent battery charger, which seemed to rate highly and was reasonably priced. I did buy an MCB, but I cheaped out and bought one from Amazon that didn't look like it would support the rated current when it arrived, so might get a better one online and use that if you think it's worth adding that too .

Can I ask what framing system you've used, and how you rate it? I'm looking for something to use to make pull-out storage racks under my stairs.

I used 2020 aluminium extrusion, bought from Misumi (https://uk.misumi-ec.com/vona2/detail/110302683830/?HissuCode=KHFS5-2020-1000#). It used to be free delivery and was excellent value, but because of covid19 there are increased delivery prices which mean it's only worth ordering from them for large orders. There are a few UK suppliers of it though, so may be possible to get locally. The ends can be tapped so that you can join the profiles together with m5 button head screws.

 

[He who knows]

Thanks.

Looks neat, but probably overkill to make some trundly frames to fit under the stairs.

 

[He who knows]

(bargain from ebay)

Hmm.

For me, that combination alone would be enough to make me want to check the output, particularly under load.

Or was "bargain" second-hand, and a reputable make which you could research for tests and reviews, rather than a cheap product from China?

 

[Ian]

Hmm.

For me, that combination alone would be enough to make me want to check the output, particularly under load.

Or was "bargain" second-hand, and a reputable make which you could research for tests and reviews, rather than a cheap product from China?

It is a Chinese-made one, but it's a second hand one that rates well from the reviews I've read - I will check the output though, just to be sure. I'll try a few inductive loads on it and see what happens.

 

[He who knows]

Yup - deffo put a 'scope on it and see.

 

[He who knows]

Thanks.

Looks neat, but probably overkill to make some trundly frames to fit under the stairs.

This type of system will be perfectly OK for me:

25mm Square Tube System

25mm square tube in painted steel or anodised aluminium plus steel cored plastic coated 90-degree corner joints to create rigid heavy-duty bespoke structures

www.tradesystems.co.uk