Battery Drain with Espar D5?

[barrel47]

I have a three year old SMB (Sprinter) and have a battery question. I keep our van in our driveway in Utah and the solar seems to keep the battery well charged. Lately, though, I've noticed something new. I've driven up to ski several times (30 minute drive), and when I arrive I turn on the furnace and notice that the battery seems to drain quickly. Today, for instance, when I got in the van, the battery was around 13.7. After parking and turning on the furnace, the battery was down to 12.4 within about 25 minutes. Nothing else running. No direct sunlight at this time. In the past, I've run the furnace all night when boondocking and didn't seem to have any battery challenges. Is this likely a battery issue, or is the battery maybe just not well charged (overnight, cold, short drive)?

[REF]

It is normal to see lower battery voltage on your display when the furnace is running, just because of the immediate draw. What are you reading with everything off including the furnace?

[marret]

Yeah, when you turn off the heater, what does the voltage go to? I know with my Planar, the initial draw to fire up and get up to operating temperature is a fair amount higher than with it running after that.

[jonyjoe101]

I would check to make sure the solar is fully charging the battery. Measure the voltage at the battery terminals to make sure its 12.4 volts and not lower. Also when charging with solar make sure the battery terminals are reaching 14.4 volts. In winter with the sun lower in the horizon the terminals might not be getting to 14.4 volts. And like you mention on a short drive, the alternator won't fully top off the battery.

[1der]

Batteries - Lithium or AGM or ??
Battery location - inside or out?
Outside temperature - ??
Inside van temperature -??
How many watts Solar?
Voltage when you first get in the van before starting the engine?

[barrel47]

Thanks for the replies. Here's a little more info:

Batteries - AGM
Battery location - Outside
Outside temperature - 20
Inside van temperature - 45 (when furnace started)
How many watts Solar - 230 (if i recall)
Voltage when you first get in the van before starting the engine - 12.7 (this morning, don't know about yesterday when I noticed this)

From recollection, after a short drive the voltage was at 13.7, when I started the furnace, the voltage fell to around 13.1 and then slowly (over 20 minutes) fell as low as 12.4 at which point I turned the furnace off and the voltage stayed at this level and began slowly re-charging.

It's early morning now and just checked the voltage, shows 12.7. So, maybe it's not fully charging during the day? I'll check at the terminals per the suggestion.

Thanks for the advice.

[1der]

I forgot to ask:
What is battery capacity?
Rigid or flexible panel(s)?
And a picture of your roof showing solar and other stuff that might be up there?

3 yr old AGM, resting voltage (no charge since solar is probably not getting sun, and nothing is on in the van except maybe the CO2 and other sensor) after sitting overnight is 12.7 and the battery temperature is 20F - that battery is holding very near 100% charged - see the chart jonyjoe101 included.

Lots to cover here:
In short, it looks to be operating as expected.

During the day the van is getting some solar charging but not much due to time of year, maybe shadowing. 230w (likely something else because 230 is not a typical#) might provide a total of 20 amps at this time of year.

Driving 30 minutes will add maybe another 20 amps.

You are seeing 13.7 because the running alternator (and solar, if sun is on the panel) is charging. Better would be 14.4 to 14.6 in Absorb, Float will be 13.7 / 13.8.

Stop the engine and no solar will see the voltage quickly drop towards 13.1 and then towards the 12.7.

Turn on a load such as the Espar, which is using around 10 amps at start up, and battery voltage will drop further as others have said. Once the Espar fan and fuel pump slows you should see the voltage move back up towards 12.6 ish.

Keep in mind that your battery Amps capacity is reduced by 1% per degree Celsius. The battery rating is given for a battery that is at 25 deg C (75F). 20F is -7C. 25c to -7 C is 32% drop in capacity. If you have a 200 amp hour 25 deg C AGM, then in 20F it is a 136 Amp hour battery.

Hope that helps.

[arctictraveller]

My current batteries (lead acid) are beginning to loose capacity. They will start out at 12.6 resting volts, and drop to about 12.2 when starting my diesel heater. Once the glow plug turns off and it gets to operating temp, it climbs back up to about 12.4, and then slowly drops to 12.2 after a couple hours. This is less capacity than when they were new, but in winter they dont' get a full charge from the solar (300W) and they are getting old. It's possible your batterys are not getting a full charge, and suffering a bit from aging or both.

[barrel47]

Thanks for the replies. With your input, it seems that this is a combination of a less than full charge and operating temperature. I don't use shore power today (solar generally has worked fine), but I may do this now to get a full charge over night and see if this makes the difference I need. I really only need 60-90 minutes tops operation for this use case. Thanks again.

[Kelp]

Make sure your inverter is off or turn off the AC breaker