Dual Battery Solar Setup - Start Batt Not Charging

[dmilamj]

So I have recently added a Solar/Dual Batt setup to my camper van and am having an issue with charging of the start battery.

Here's the setup in my 2004 Chevy Astro:

100 AHr Universal SLA house battery
150W Renogy solar panel
EPEVER Tracer 2215BN 20A MPPT Solar controller
BlueSea SI-ACR and battery switch
Standard SuperStart flooded start battery

There is 4 gauge wire between all components except for (and this might be my problem) the connection from the SI-ACR/switch to the Start battery which is 8 to 10 gauge (I didn't install this part, it was installed by Colorado Camper van to connect the house batt to the linear actuators). This connection is about 8 feet in length.

The system powers the linear actuators for the pop top, lights, (future) fridge, stereo

Now, when the battery switch is "Off" and the systems are separated, the house battery gets a proper charge from the Solar and is sitting at 12.85 to 12.9 Volts after a sunny day. The next morning this has not really changed.

When I switch to "On" and allow the SI-ACR to connect the Start and House batteries, when Solar is applied everything looks reasonable, I get charge voltage on the house battery.

The problem is I'm not getting a decent charge on the start battery through the SI-ACR. At the end of a sunny day with no loads, I'm sitting at what looks like full on the house battery. But the start battery will be at 12.2 or so. The next morning, the two batteries will have equalized until the SI-ACR cuts in and separates them, and will both be at ~12.4 - 12.6 Volts.

I pulled the start battery and it tested good. I charged it with an external charger and it seems to be holding the charge. It does look pretty old though.

My concerns:
1) Start battery is standard flooded, House battery is SLA, they charge at different voltages. Am I foolish for trying to combine them into a dual setup?
2) Is the voltage drop along the low gauge wire to the start battery the problem? I feel like even with some voltage drop, I should be able to charge the start battery reasonably well, but maybe I'm wrong. If I upgrade, what gauge should I use?
3) The solar controller is very close to the house battery (12 inches) but far from the start battery (8 feet) and the start battery needs a higher charging voltage. Am I screwed or can I get a decent charge on the start battery?



Thanks,


Dave

 

[dstock]

Did you have the start battery load tested? Also, after being charged up, does it hold the charge overnight with no loads attached?

I would also check for drains on the start battery, perhaps you have a short on the Astro. Regardless, I would swap out the low gauge wire to at least match the 4 gauge wire used everywhere else.

 

[Bbasso]

FYI I used 0 guage cable between the ACR and starting battery. But I have two starting batteries and two house batteries with a lot more juice than you.

As for the problem, sounds like the ACR might be hooked backwards? But that's a poor guess.

 

[Joe917]

Just as a matter of interest why are you trying to charge your starting battery with solar?
The starting battery should hold a charge for weeks without needing solar. Keep all your house loads on the house battery and forget about it. If it does not hold charge, the battery is bad or your charging system is. Either way charging with solar will only mask the issue.

 

[dmilamj]

You are correct there is no backwards on that ACR, so I know that's not a problem.

I measured the voltage, and I'm getting a voltage drop of about .11 to .13 volts along the length of the charging cable during operation. It seems like I should be able to get an okay charge with that voltage drop...

When I say switch "on/off" I mean using a bypass switch to either "Off": disconnect the solar system/house battery from the start battery, "On": allow the ACR to do its thing, "Combine": Force the two batteries to be connected, regardless of voltage/load (effectively bypass the ACR).

Fwiw, there is no "backwards" with that ACR.
Whenever either battery achieves threshold voltage, combining or separation occurs.

As far as voltagedrop on that 10awg, I dunno.
Its not really long considering its maximum current from solar cant exceed 11amps or so & in real life likely much less.
Looks like you need to accurately measure voltages whilst in operation.

Further, I dont understand your switching "on-off" comments. ACRs are supposed to be "automatic" afterall.
I realise they may have manual overides for various reason, but usually not something one regularly actuates.

 

[dmilamj]

Just as a matter of interest why are you trying to charge your starting battery with solar?
The starting battery should hold a charge for weeks without needing solar. Keep all your house loads on the house battery and forget about it. If it does not hold charge, the battery is bad or your charging system is. Either way charging with solar will only mask the issue.

That's true. I figured my van might be sitting for weeks/months at a time during non-camping seasons, and I wanted to be able to keep the battery topped up.

I had the start battery tested at Advance Auto and they said it was good. I then put it on a smart charger, and the charger thought it had charged it.

So, after the charger, the battery was at 12.85 or so volts. In the morning, with no load applied, the battery just sitting in my garage, my multimeter said 12.45 volts on the start battery. That doesn't seem right, does it? Probably an aging battery.


After I installed the battery, I could hear a relay click in the engine bay, and suddenly voltage dropped to 12.1 volts.

I'm probably overthinking this and just need to get a new battery. I'm concerned about the voltage drop after I hook up the battery though. I'm afraid there might be some type of fugitive load...

 

[dmilamj]

Did you have the start battery load tested? Also, after being charged up, does it hold the charge overnight with no loads attached?

I would also check for drains on the start battery, perhaps you have a short on the Astro. Regardless, I would swap out the low gauge wire to at least match the 4 gauge wire used everywhere else.

Advance Auto did a load test and said the battery was okay. But as mentioned above, it doesn't seem to be holding charge with no load, so I guess that is my (obvious) problem...

What's a good method for checking for current drains on the start battery? I guess I can hook my multimeter up inline and check current flow with everything on the van off... Not sure how to track down the problem after that, but I'll cross that bridge when I come to it.

 

[Joe917]

Advance Auto did a load test and said the battery was okay. But as mentioned above, it doesn't seem to be holding charge with no load, so I guess that is my (obvious) problem...

What's a good method for checking for current drains on the start battery? I guess I can hook my multimeter up inline and check current flow with everything on the van off... Not sure how to track down the problem after that, but I'll cross that bridge when I come to it.

You've got it. Use a multi meter see if there is a draw and if so pull fuses till you find the right circuit.
The battery is bad if it can't hold voltage overnight. Battery voltage will drop from the time you disconnect the charger until the charge is absorbed into the plates. It takes about 4 hours after charging (or discharging) for battery voltage to stabilize, this is why voltage readings are of little help in a working system. Voltage is a very good way to read state of charge only in a rested battery.

 

[dstock]

Advance Auto did a load test and said the battery was okay. But as mentioned above, it doesn't seem to be holding charge with no load, so I guess that is my (obvious) problem...

What's a good method for checking for current drains on the start battery? I guess I can hook my multimeter up inline and check current flow with everything on the van off... Not sure how to track down the problem after that, but I'll cross that bridge when I come to it.

If it's not holding a charge with no load, it's toast. I'd start by replacing it before looking for drains as you likely don't have any abnormal drains, just a bad battery. As Joe917 mentioned multimeter is the way to go.

 

[IdaSHO]

Agreed, if it isnt holding a change and is discharging rapidly without any load, its toast.


Also, I've learned over the years that load testers are not the end all to battery testers.
I've had more than a few batteries that tested fine, not be fine.