DC to DC charger installation issue

[Buce15]

I have a 20a Renogy DC to DC charger connected to two 12v 35aH AGM batteries which connect to a 400W inverter set up in my 16 Honda Pilot. I mostly use it to charge my laptop. Last night, while the car was running I noticed my laptop battery died while plugged in. I checked the house battery voltage and got 11.2. The battery seems to be charging albeit slowly while the inverter is off. Any ideas why my battery isn't charging while my car is on and my laptop is plugged in? I'd be happy to bring it to someone to look at but no mechanic I've brought it to has any clue how to diagnose or fix the issue. Any help at all is appreciated

 

[Buce15]

Ok... So it seems as though the charger isn't actually charging my batteries. Wires are secure, D+ is connected to the ACC fuse via fuse tap. Green and red light are on on the charger (I think red means low voltage?). Something is up... Getting 14.1V on input and output shows 11.3, been running my car for the past hour or so and the 11.3 hasn't moved. Is my battery bad? Are the DIP switches wrong? They're all set to On per https://www.renogy.com/content/files/Manuals/Renogy DC-DC Battery Charger Manual.pdf. Using 2 12v 35aH batteries from harbor freight.

Called mechanics and RV service shops and nobody thinks they can fix it. Any advice at all is appreciated!

 

[B and C]

What is the voltage of your engine battery? Idling an engine to run the alternator is probably not the best solution. Check the paperwork of the DC to DC charger and see if your engine battery voltage is above what the charger requires. I got a car charger for my laptop, much better. I don't remember the last time I turned my inverter on.

Welcome. Mosey over to the newcomers corner and introduce yourself to get a proper welcome.

 

[Elbear1]

Ignition relay connected?

 

[gapper2]

With the engine running what voltage do you read at D+ at the back of the charger?

 

[Buce15]

Thanks for the replies -

Engine battery voltage is 12.94 idle, 14.20 running.

Ignition relay is connected, getting 13.8 volts. The charger is on, it has power. Perhaps it's an issue with the DIP switches... From what I read, the batteries warrant all switches being in the ON position (see: https://www.renogy.com/content/files/Manuals/Renogy DC-DC Battery Charger Manual.pdf Page 20-21).

The batteries I'm using are 2 of these: https://www.harborfreight.com/12-Volt-35-Amp-Hour-Sealed-Lead-Acid-Battery-64102.html

Are the DIP switches set wrong?

Edit: Doesn't show much of note, just the lights being on: https://photos.app.goo.gl/NDmKsepuiuNacezy9

 

[Elbear1]

Manual said something about 12.5% charging. IDK. flip DIP's and report back.

 

[B and C]

With the blue light on on the DC DC charger, what are the voltages on the engine battery side and the house battery side of the charger, engine running? The blue light has to be on for it to work.

 

[gapper2]

On my Sterling B2B charger when I first was installing and changing profiles the microprocessor was locked   into a confused “state” .  After DISCONNECTING both input and output power,  I shorted input + and - with a wire and drained internal charge.  Then after reconnecting everything and rereading the manual it worked hunky Dory. 

 

[Buce15]

The 12.5% is another optional input signal which I did not connect. I double-checked to make sure the input went to D+ not "LC" - you can barely see it in the photo - the green wire.

I think the "blue light" is actually the green light. With the engine running, input is 14.2, output is 11.3. I'm measuring from the metal terminals on the charger where the wires come in.

I'll try what gapper said - I'll disconnect the battery first, then disconnect the charger completely and short it out. I'll see if that helps.

If not, I'll mess with the DIP switches as a last resort.

The manual is unfortunately not very helpful, I've read it a few times and think I followed all the steps. I'm not positive the DIP switches are in the correct position.

 

[gapper2]

Dip switches all on looks good to me. If resetting the microprocessor and all connections are good, time to call Renogy tech support with your info.  Sounds like defective unit.

 

[highdesertranger]

those are Sealed Lead Acid(SLA) batteries not AGM(Absorbed Glass Mat) batteries if that makes a difference. I don't know if you care but that is a very inefficient way to charge your laptop. highdesertranger

 

[Buce15]

Dip switches all on looks good to me. If resetting the microprocessor and all connections are good, time to call Renogy tech support with your info.  Sounds like defective unit.

gapper2 you're a god send! I unplugged everything, "shorted" the input by running a wire between the two input terminals, put it all back together and BOOM! POWER! Thank you so much for the advice =D
Possibly coincidence and putting everything back together and re-tightening everything was all that was needed but I really think your tip saved me. I owe ya a beer

 

[Buce15]

those are Sealed Lead Acid(SLA) batteries not AGM(Absorbed Glass Mat) batteries if that makes a difference.  I don't know if you care but that is a very inefficient way to charge your laptop. highdesertranger

Hmmm I thought they were AGM - I'll look into it and see if the charging profile should be changed, thanks for pointing it out! I know it's inefficient, but I have other reasons to have the 400W inverter, it just happens that the thing I use it for most is charging/running my power hungry gaming laptop.

 

[wayne49]

Look on eBay or Amazon for a DC charger for your laptop.
Alternately, see what your AC charger is putting out in VDC and amps and look for an electrical match that has the same physical output plug.

 

[gapper2]

Disconnecting all power and let unit sit long enough, eventually it will drain internal charge on its own.  Easier to just disconnect power and short input.  Learned the "Hard Way".  Like others have suggested much more efficient to charge with laptop dc charger.  But heay, you're building a system.

 

[Tom_M]

those are Sealed Lead Acid(SLA) batteries not AGM(Absorbed Glass Mat) batteries if that makes a difference.

The description and label both say AGM.

 

[B and C]

The picture you linked to for your battery, the last line on the left of the label says sealed lead acid. You evidently bought something different.

 

[Tom_M]

The picture you linked to for your battery, the last line on the left of the label says sealed lead acid.  You evidently bought something different.

AGM batteries are lead acid. From Wikipedia:

"A valve-regulated lead-acid battery (VRLA battery) sometimes called sealed lead-acid (SLA) or maintenance free battery.
There are three primary types of VRLA batteries, sealed VR wet cell, absorbent glass mat (AGM) and gel cell. Gel cells add silica dust to the electrolyte, forming a thick putty-like gel. These are sometimes referred to as "silicone batteries". AGM (absorbent glass mat) batteries feature fiberglass mesh between the battery plates which serves to contain the electrolyte and separate the plates. Both designs offer advantages and disadvantages compared to conventional batteries and sealed VR wet cells, as well as each other."

 

[Elbear1]

AGM batteries are lead acid. 

BOOM. lol