Home-Made Secondary Battery Setup

[AA1PR]

nice clean install

however my fear is venting of the battery, I've heard terrible things about the fumes

[djthumper]

I have an AGM battery back there.

[TBYODA]

nice clean install

however my fear is venting of the battery, I've heard terrible things about the fumes

Aren't today's batteries sealed?

[AA1PR]

nice clean install

however my fear is venting of the battery, I've heard terrible things about the fumes

Aren't today's batteries sealed?

one would hope so

[Trail X]

I've never had an issue, it is not an AGM, but I don't recall if its sealed. I think it is, its a marine battery.

[Shdwdrgn]

I was going through old threads yesterday and this one caught my eye. Having a dual-battery setup for the inverter would actually be pretty handy, and it just so happens I've been working with different small computer chips lately, including the ATtiny85.

I'm curious if there's still any interest in a delayed-timer board? I think I could put these together for around $15 in parts (including the changes below), so how does that price compare to other available solutions?

If I were to make these, there would be some changes...

The 7805 is horrible inefficient, and it converts all that wasted energy directly into heat. I can get a nice DC-DC converter with a fixed 5V output that will work reliably with an input between 6.5V and 26V.

I would use a small rotary switch to provide an easily-adjustable timer between 0-7 minutes

An LED could be added to blink while the timer is waiting, then go on solid. This could be helpful for troubleshooting?

Output would go through a transistor rated for 1A, which should be more than enough to drive the relay.

With all that, there is still one more available pin free on the chip. This could be used as a secondary input trigger, or to drive another output. I could use it as another line for the rotary switch, and allow timing between 0-15 minutes. If used as another output, it could be set to 1/2 or double the timing of the main output, or it could be set up to trigger X minutes after the main output turns on. The nice thing about programmable chips is that it's so easy to change what is being done.

Any thoughts on this?

[v7guy]

I'd be mildly interested, but I don't see this as a common mod at all.

[Shdwdrgn]

Yeah I agree, probably nothing worth ordering a set of circuit boards for. If I get around to building one, maybe the best bet would be doing a write-up and posting the code so others can build the same thing. You can get the computer board for about $3 on ebay which has a USB port to program it... the only difficult part is soldering the parts together, and installing the software on your desktop needed to program the chip.

[Trail X]

You mentioned secondary inputs, makes sense. The only thing I wish I could do is trigger mine to turn on manually on demand, because no matter what, I have to wait 5 minutes for mine to operate. A momentary switch to allow you to trigger it on early would be helpful I think, if not used often.

[Shdwdrgn]

That's actually a really good idea... and the momentary switch could even be set to turn it on and off.

If < 5 minutes; toggle between on/waiting/off
if > 5 minutes; toggle between on/off

Add another transistor, and the LED line could also run a 12V light in the momentary switch so you have a visual on the dash.

[Trail X]

Yeah, my indicator light is in my control switch, but it really is just a switch position indicator, not a charging state indicator.

[Reyansh02]

The FET isn't really a relay, you're right, but for explanations-sake, it's a close likeness... at least to an ME.
story saver
The FET we used had a heat sink on it, we tested it for steady-state heat dissipation, and seemed fine in the lab.

In SQL Server, views with numbers in their names can cause issues because object names starting with a number are not directly supported. To avoid errors, name your views starting with a letter or underscore, followed by alphanumeric characters or underscores. This ensures compatibility and smooth operation within SQL Server databases.