diy solar

diy solar

Camper Trailer Solar/Lith upgrade (WF-8740 Power Center)

The DCC50S looks like a cool product that could manage the charging from multiple sources a little cleaner.
There have been a lot of problems with it reported on the forum.
Renogy support can't even decide how its supposed to work.
 
WF8740 does not max out at 13.6vdc.

It has a 14.4 volt bulk mode and 13.2v float. It's not inherently unusable with lithium as such, and does not do equalization.

This is all in the manual.

It is definitely better to upgrade to the lithium version though. I'm debating doing this for mine.
I have a WF8945 in my camper and I have never seen it put out 14.4 volts during normal operation. The unit will only activate "boost" mode if the voltage sags below 13.2 volts while plugged into shore power. In order for this to happen, I have to put at least a 40 amp 12v load on the system. Only then does it switch to 14.4 volts.
 
I have a WF8945 in my camper and I have never seen it put out 14.4 volts during normal operation. The unit will only activate "boost" mode if the voltage sags below 13.2 volts while plugged into shore power. In order for this to happen, I have to put at least a 40 amp 12v load on the system. Only then does it switch to 14.4 volts.
Do you have lithium batteries? If you do, pulling #4 wire in the charging loop will sure help.
 
I have a WF8945 in my camper and I have never seen it put out 14.4 volts during normal operation. The unit will only activate "boost" mode if the voltage sags below 13.2 volts while plugged into shore power. In order for this to happen, I have to put at least a 40 amp 12v load on the system. Only then does it switch to 14.4 volts.
If you're plugged in then the battery voltage isn't really necessary to keep up at 14.4+.

In fact it isn't necessary at all to charge that high honestly.

If you have solar, the scc should make up the difference with ease. When the wf unit sees the higher voltage coming it will stop trying to charge the battery, the voltage will not sag because the scc is supporting it, and your battery will charge the rest of the way. If you're out using that power then it's kind of moot and you get what your panels give.

Or, realize that 13.6v is 3.4v per cell which is rather very close to max charge due to the fun curve that cells have and that trying to go out of your way to charge to 14.2 or 14.4 volts is kind of a waste of effort and ultimately the lower charge will extend life a bit.

I suppose you could make the argument that you want to fully charge it in your driveway or a one night campground site rental before boondocking, but it's only a few percent of capacity being missed out on.

But if you absolutely must insist on 100% charge vs ~97% charge then you should buy the lithium version from them. Just remember that slightly less than maximum charge makes them last longer.


Of course if anyone can point out a flaw in my logic I'm all ears. I've been wrong before.
 
Of course if anyone can point out a flaw in my logic I'm all ears. I've been wrong before.
The only issue I know is when expecting a fast charge from a generator. At 40+ amps the voltage applied to the battery can sag a few tenths through the oem wire and connections. So then you are at 13.2/13.4 at the battery and the amps start to sag.
 
The only issue I know is when expecting a fast charge from a generator. At 40+ amps the voltage applied to the battery can sag a few tenths through the oem wire and connections. So then you are at 13.2/13.4 at the battery and the amps start to sag.
Eh. Yeah. Kind of.

But with a smallish battery at 12v it may be the difference between running the generator for one hour or 70 minutes to get the same amount of power back into it.

Typically a negligible concern.

But if it's putting 40+ amps (or whatever your panel of choice is, mine is 25a) into the lithium battery then it should kick into the 14.4v bulk mode anyways and the problem sorts itself out.

I don't have my lithium pack yet to test this theory with my WF panel though. I would suggest OP tries it out before trying to spend money on the lithium version of the thing.
 
Do you have lithium batteries? If you do, pulling #4 wire in the charging loop will sure help.
No, I've got FLA deep cycles.

Like you mentioned, the main problem with the WFCO charging behavior is I have to run the generator for a very long time to mostly charge the batteries.
 
No, I've got FLA deep cycles.

Like you mentioned, the main problem with the WFCO charging behavior is I have to run the generator for a very long time to mostly charge the batteries.
I'll repeat that "mostly" charging them is very nearly fully charging them.

It's not as linear as a lead battery.

13.6 volts / 4 cells is 3.4v per cell.

Take a look at just how full that is based on this chart (and many others just like it).
These things drop a couple tenths of a volt very quickly then remain fairly stable until they suddenly drop off again at the end.

At 3.4 volts per cell you're certainly >97% full with most charts and posted results indicating its actually >99% full.
LiFePO4-discharging.png

Take this user's measurements for example.

At 3.38v per cell they are reporting 99% SOC. That's 13.52v if each cell is perfectly balanced.

Much to do about little to nothing if you ask me.

Regarding charging speed, if your panel is putting its rated 40A into your system then that's all it's got. Increasing the voltage from 13.6 to 14.4 will speed it up slightly, but it's not going to be a dramatic improvement.

Further, if it is putting that into the battery (the lithium should have no trouble "pulling" it) it should automatically switch to 14.4v anyways, but again this is something I'd need to test out - and I will do so in the next month or so hopefully.

If it does do that then using the lithium specific one will not improve that unless it's rated for more current, it will just improve the charge quality a bit.
 
My WFCO converter will float at 13.6v for two days. Then drops to 13.2v.
I can trigger it back to 13.6v using the manuals check procedure.
1. Turn off your loads to prevent damage
2. Turn off your converter breaker or camper AC.
3. Turn off your battery. I have a circuit breaker switch.
4. Turn on your converter breaker or camper AC.
5. Check for 13.6v from converter.
6. Reconnect battery. Recheck voltage, climbing from 13.2v to 13.6v
7. Turn loads back on

BTW: I never saw the WFCO go to 14.4v. I think the 6awg wire length is too long to get enough current to trip to bulk mode.
 
BTW: I never saw the WFCO go to 14.4v. I think the 6awg wire length is too long to get enough current to trip to bulk mode.
I could get my WFCO to go 14.4 by hitting the inverter-microwave for about 20 seconds. Drops the converter well below the 13.2 trigger and voila 14.4 volts. My converter/charging loop is about 25' upgraded to #2 wire.
 
I just installed a battery monitor with a shunt in my camper with a WFCO 55 amp power center. Just to get a baseline, I installed a single group 27 faux deep cycle flooded lead acid battery and drew it down to 60% SOC (12.3v rested). After plugging into shore power, my WFCO is charging the battery with a whopping 2.6 amps at 13.7 volts over 4 feet of 6 awg wire. It will probably take a few days to get a full charge.
 
Following up... After two days the WFCO dropped to 13.2 volts and according to the battery monitor, the group 27 lead acid battery is still 15 ah short of being recharged.

I didn't have time to measure specific gravity this morning, but I hooked up my little automotive charger and it was pulling the full 4 amps it can put out. The WFCO is no bueno for charging lead acid batteries.
 
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