Micro Minnie 2108DS "rapid charger"

tinglett · 10-01-2022, 09:55 AM

In the past I posted my 2108DS upgrade with two 100A Battleborn lithium batteries which included a charger update. See:

I learned a lot doing this upgrade and the solution has worked very well for us. But one thing that has bugged me is how slow charging goes. At best I get about 30A into the battery from the PD4655LIV charger. The charger is capable of 55A, and I proved it was voltage drop over the 6AWG cables by connecting a battery direct to the charger with short 4AWG cables and it did get close to 55A.

Here's a photo prior to this "rapid charger" upgrade for some context. All the gear is in the street side storage bay and pretty accessible.

I don't really need "rapid charging" when I'm connected to shore power, but I do want the process to go faster when running the generator. For 30A charging, my generator isn't even producing 500 watts so I'd really like to crank it up.

I had thought about "upgrading" my cables, but what a nightmare that would be. Someone on this forum, sorry I can't recall who, suggested I connect an external charger when using a generator. Then the cables can be short. But I decided to go two steps further! Instead I added a 2nd charger next to the battery and connected into the 115v AC. I'll try to show what I mean via photos, and then in a second post I'll show how it works (spoiler alert -- it works very well!).

If you go back to my lithium battery install, you'll see I put the batteries in a box within the street-side storage area up front. I have a 2019 model so it's just a little bit different than newer 2020-22 models. In this bay I mounted an additional PD9160ALV 60 amp charger as you can see here:

The charger is mounted with bolts and fender washers through the cabinet above which is on the street side of the bed. This won't work for newer models, but I'm sure something could be rigged up. Note on the left side of the photo is a new 115v AC outlet I added. I tapped this outlet into the bed-side outlet about 2ft away.

The idea is that I normally will not keep this charger plugged in (as it is in the photo). I'll unplug it when on shore power, but I'll plug it in if I want faster charging when I connect the rig to my Honda EU2200i.

I took the opportunity to organize terminal blocks just inside the murphy bed access space as shown in the following photo. Again, this is very different in newer 2108DS models.

Now I have a nice place to join up all my charging gear. In addition to the two chargers, I have a solar charger. All three are set to a lithium 2-stage charging profile so they don't trick out each other and do stupid things.

Finally, here's a photo with everything in place. Again, this is in the street side storage bay looking forward. I really only lose storage space in this little area alongside the street. The main storage area remains completely open.

I'll make another post in a few minutes with some results. I was able to take it out on a boondocking trip so had an excellent opportunity to try it out.

tinglett · 10-01-2022, 10:17 AM

Here are some results on my first boondocking trip with this dual charger setup. We had stayed for a few days within heavy tree cover so solar was producing pretty much nothing. We were down to 31% SOC so I thought it was time to fire up the generator and try it out.

Here's what the Honda EU2200i looked like in my practice run at home with a kill-a-watt meter. Here I used a Y adapter for power, but my new install gets rid of that mess.

Note that the setup is drawing 1323 watts. The generator can easily produce this, and in fact the ECO mode lets it settle down to a little quieter running.

Straight away my Victron BMV monitor was showing some good news!

Yes, that is 83.5A of current going into the batteries! I have two batteries and Battleborn assured me it is just fine to pump as much as 100A into them when they are together like this. I'm kind of wishing I had gotten an 80A charger instead, but the price point was quite a jump over the 60A that I'm using.

To be clear, the PD4655LIV 55A charger under my refrigerator and the PD9160ALV 60A charger in the storage bay were working together to produce this 83.5 amps.

I charged for a total of 2hr. The current dropped quickly to 75A after about 5 minutes and then slowly dropped to 60A over those 2 hours. At 2 hours I decided I had run long enough as I was up to 91% SOC. In those 2 hours I put in 130Ah.

Not bad. And I have a couple observations. First, the generator was louder than I thought until I realized I had left my absorption fridge in "auto" mode. Doh! That was easy to switch back to gas. The 60A charger got pretty hot to the touch during the run. It's not hot enough to scorch any wood or create a fire, but I think I'll add some 1" spacers to allow a bit better airflow over the top.

All in all, I'm pretty happy with the results. The charger cost about $290 which was pretty high, but I got my charging done in 2 hours instead of 6. This was a one week trip and so we only needed to charge once mid-week. I thought that was pretty nice since I could keep the generator tucked away locked in storage.

RocknRoll · 10-02-2022, 05:16 AM

Nice work Todd. You've turned a nice install into a great one.

Marine359 · 10-02-2022, 09:40 AM

Bravo Todd. Engineering mastery.

Fred 2106DS · 10-02-2022, 04:20 PM

Nice work Todd! When's the inverter install?

thataway4 · 10-06-2022, 04:59 PM

Great Work. One suggestion is to put a small computer fan, with a thermal snap disc to turn the fan on at 100* (or what temp you desire) with a port to increase the flow of air and cool the charger.

Many users of the LiFePO4 batteries cycle them between 80% and 20%. As you try and get those last 10 t0 20 amps, it is a diminishing return on generator time. Solar, or mains power can bring the batteries up all of the way when desirable.