Dead trickle charger controller

400bird

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May 23, 2020
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756
I've got a Battery Tender 5 watt battery maintainer/trickle charger.

It isn't much, but it did keep the batteries in the truck charged between uses.

Well, the integrated controller died.
The led flashes yellow/green, which isn't in the manual for this version. On newer models that means it doesn't detect the 12v battery.

It's only 5 watts, but should I be worried about it overcharging the sealed starting batteries in the truck?

I was considering making a poor man's excuse for a charge controller by adding a diode to prevent reverse current flow (battery to panel) and a zener diode to limit PV output to 14 volts.

Thoughts? Am I miss representing what a zener diode is capable of?


Here's the zener diode I was looking at:
 

400bird

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May 23, 2020
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756
To expend on my potential (MacGyver) plan:

The zener diode would go from PV+ to PV-, so that when system voltage exceeded 14 volts, the avalanche voltage is exceeded and shorted back to the panel.

Then on the battery side of the zener, I'd need to add a diode, so the charging system (alternator) doesn't reach the zener diode. Ideally, I'll remember to pull the panel off the dash before starting the truck, but I'm not reliable enough to count on that.
 

Substrate

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Instead of MacGyvering it, Battery Tender sells a stand-alone 5-45 watt controller if you can get to the panel leads. Screws on each end of the unit to make sure of a good connection.

I suppose I'd try disconnecting and reconnecting the original unit obviously. Still, with thin wires, I suppose with a lot of flexing you may lose conductivity. That's why for these applications, I like the outboard Deltran controller and my own panel.

And decent cabling. No speaker-wire please. :)
 

400bird

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May 23, 2020
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756
I saw that that controller, but this panel is "rated" at 3 watts, that controller probably won't work.

The sticker on the back of this panel is for the entire system (including charge controller), not just the panel. But it says 12v @ 270 mA

I haven't measured short circuit current.
The bare panel open circuit voltage was about 23 volts.
So, the sticker is a lie. If it's sunny today, I'm hoping to measure short circuit current.
 

400bird

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Joined
May 23, 2020
Messages
756
I just test and verified the short circuit current is about 260 mA.

I don't necessarily need max output from this panel. The truck uses about 26 mA constantly. So I just need to make up for that, and I don't need to do it daily.


Any yes, obviously not speaker wire 🙄
That stuff's too expensive! I've got some old sold 24 awg twisted pair phone wiring! 🤣
 
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