Controller/charger recommendations?

**nateritter** · 02-25-2022, 07:58 PM

So we are upgrading as we boondock and find bottlenecks. I started with 3 lithium batteries (no solar, everything else stock) to replace the 1 lead acid that was dead when we bought the rig (2021 GD Reflection 31MB 5er).

Been boondocking for 3 nights previously with no issues. We used the gas generator (3500) only to power enough to try an instant pot dinner (not doing that again for a while). Granted I didn’t see us drop less than 80% levels on all 3 batteries during that time, and didn’t check it before we left the site.

We went boondocking last week, though, and I knew we would need to recharge my laptop and maybe other things. So I bought a small inverter (750w) that would alligator clip to a battery. I ran a long extension cord through a gap in the slide and subsequently drained our battery array somehow to 40% by the next day. (Only draw would be the inverter itself and the LED in the extension cord that indicates it has power since we unplugged everything that evening).

I unhooked the inverter and thought ok, we will just last on this for the night and have no problems because we will leave the next afternoon and be on shore power for two days.

Strangely, we went to zero during the next day (different issue I will have to troubleshoot later). I broke out the generator and got enough power to pull in the slides and retract the gear so we could get to the campground.

At the campground at 50a shore power for 2.5h we only got up to about 40% on all 3 batteries.

The reason I’m mentioning all this is because I believe we need to swap out the charger (or converter, I still don’t quite understand the difference since sometimes they are all in one - inverter, converter, charger).

Ok, so here’s the ask.

1. What’s the difference between a charger and a converter?

2. I assume I have both, and both are stock units in my rig. So which (or both) should I replace to be able to charge faster and more effectively when on generator/shore?

3. Any specific recommendations for charger/converter replacement with my battery setup and rig? Not interested in Renogy products.

4. I have no idea where mine is located, how do I find it? And any resources for how to replace the stock one in my specific rig?

5. Any gotchas or things to watch out for when replacing it?

Thanks everyone. This has been the best community for this type of diagnosis and help. Really appreciate it.

**FT4NOW** · 02-25-2022, 08:32 PM

1. What’s the difference between a charger and a converter?

Essentially the same thing, a converter converts 120v to 12v, any excess current not needed by 12v system charges the battery.

2. I assume I have both, and both are stock units in my rig. So which (or both) should I replace to be able to charge faster and more effectively when on generator/shore?

Should only be a single unit

3. Any specific recommendations for charger/converter replacement with my battery setup and rig? Not interested in Renogy products.

Progressive Dynamics 9160AL is a good one designed for lithium batteries

4. I have no idea where mine is located, how do I find it? And any resources for how to replace the stock one in my specific rig?

Probably behind the false wall in basement.

5. Any gotchas or things to watch out for when replacing it?

Check your existing converter rating, probably 55 or 60A and keep it the same or ensure your wiring supports a higher output converter.

Your charging you described sounds correct. Assuming you are not drawing a load on the 12v system and you have a 55A converter, you would ideally supply 165A to your battery bank which is a little more than half. In the real world there are 12v loads you cant turn off and there are some electrical losses. Either way, if you have a WFCO converter designed for lead acid, a new converter wont hurt. The speed of charging is limited by converter output and wire size, most important, make sure your wires are not undersized for fire safety.

Keep in mind while running an inverter (inverts 12v to 120v) you will use about 10x more amps on DC than AC. For example, a 3A AC load will use almost 30A DC while going through an inverter.

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**nateritter** · 02-25-2022, 09:16 PM

Wow. Couple things in there I had no idea about.

Thanks for the reminder on the wire size. Definitely forgot about that.

And I had no idea about the 10x AC. That explains a lot of what happened yesterday!

I assume the inverter itself takes some decent amount to run when on too, right?

**Ynot4me2** · 02-26-2022, 05:47 AM

Originally Posted by nateritter

Wow. Couple things in there I had no idea about.

Thanks for the reminder on the wire size. Definitely forgot about that.

And I had no idea about the 10x AC. That explains a lot of what happened yesterday!

I assume the inverter itself takes some decent amount to run when on too, right?

Cheaper inverters will require more power to run. Called power efficiency or sometimes power factor. Good ones run just above 90%. Which means you loose 10% of DC power. Every electric device uses watts. Watts law is Watts = volts x amps. So a device that needs 1200 Watts like a microwave let's say will need 10 amps on regular AC or 100 amps on DC. 1200w = 12v x 100a. Your inverter will require 110 aDC to generate that 10 aAC. Some cheaper inverters have much less power efficiency. So you can see the impact.
Chargers charge the batteries, they can either run off of AC or DC, in RVs they run off of DC and have different charge profiles depending on the SOC of the battery. Converters convert AC power to DC power. Inverters are the opposite, they turn DC to AC.
As mentioned above, be carefull when upgrading any electrical devices or adding. Cable size comes into play, length and fuses might/should be used with inverters.

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**Scott'n'Wendy** · 02-26-2022, 06:08 AM

Originally Posted by Ynot4me2

Called power efficiency or sometimes power factor.

Some companies might use the term power factor but it has nothing to do with the efficiency of an inverter.

**Ynot4me2** · 02-26-2022, 06:25 AM

Originally Posted by Scott'n'Wendy

Some companies might use the term power factor but it has nothing to do with the efficiency of an inverter.

Agreed but in order to keep it simple it's still lost power (absorb by the device).

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**xrated** · 02-26-2022, 08:23 AM

Originally Posted by FT4NOW

1. What’s the difference between a charger and a converter?

Essentially the same thing, a converter converts 120v to 12v, any excess current not needed by 12v system charges the battery.

2. I assume I have both, and both are stock units in my rig. So which (or both) should I replace to be able to charge faster and more effectively when on generator/shore?

Should only be a single unit

3. Any specific recommendations for charger/converter replacement with my battery setup and rig? Not interested in Renogy products.

Progressive Dynamics 9160AL is a good one designed for lithium batteries

4. I have no idea where mine is located, how do I find it? And any resources for how to replace the stock one in my specific rig?

Probably behind the false wall in basement.

5. Any gotchas or things to watch out for when replacing it?

Check your existing converter rating, probably 55 or 60A and keep it the same or ensure your wiring supports a higher output converter.

Your charging you described sounds correct. Assuming you are not drawing a load on the 12v system and you have a 55A converter, you would ideally supply 165A to your battery bank which is a little more than half. In the real world there are 12v loads you cant turn off and there are some electrical losses. Either way, if you have a WFCO converter designed for lead acid, a new converter wont hurt. The speed of charging is limited by converter output and wire size, most important, make sure your wires are not undersized for fire safety.

Keep in mind while running an inverter (inverts 12v to 120v) you will use about 10x more amps on DC than AC. For example, a 3A AC load will use almost 30A DC while going through an inverter.

Sent from my SM-G950U using Tapatalk

I'm not necessarily onboard with that. Lots and lots of "Lithium" chargers produce boost/bulk voltages (14.6 volts) that are simply not necessary in order to achieve a full SOC of the LFP battery. If you take that 14.6V and divide it by 4, which is what each cell in the battery is charging to, that is 3.65V per cell. That is the MAX voltage that the cell should ever be subjected to and in fact does shorten the life of the cell and the battery in general. It is generally accepted that a cell will be at full state of charge when the voltage of that cell is 3.45V.....or 13.8 volts for the battery. The 14.6V is used to help reduce the time that it take to charge the battery, which is great....BUT....at what cost? Lots and lots of folks that have adjustable chargers, via a programmable setup, will limit the bulk/boost voltage to around 14.2V....and many times a bit less. Yes, this slows the charging process somewhat, but it also helps with longevity of the battery and the cells within the battery.

Personally, I do not want a Lithium based charger profile charging my "to be built" LFP batteries, so I'm not going to change out the OEM WFCO 9855 converter/charger that came in my trailer. That one is supposed to be 14.4V bulk, then drop down to 13.6 absorption, then finally down to 13.2 for the float voltage. Several folks have told me "good luck" with getting that to actually go into bulk mode (14.4V) because that model just seems to not want to transition from absorption to bulk. If it ends up staying the absorption mode (13.6V), that is not very far off of approx. 95% SOC for a LFP battery.

It will be an experiment for me, once the weather gets better and I'm ready to assemble and deploy the LFP battery. I can very likely live with a battery that has reached a 95% State of charge (SOC), but time will tell in a few months.

**FT4NOW** · 02-26-2022, 08:48 AM

@xrated I agree with what you said. The OP asked for recommendations and I gave one based on my experience with a converter I installed in my 399 when I swapped to lithium batteries. If I recall, I said it wont hurt to change out the converter, but I didnt say it was necessary.

There have been numerous discussions on this and I think the consensus is that you can use the lead acid charger and it wont hurt the lithium batteries, but on the other hand if the OP is looking to charge his bank faster he will need a higher amp converter.

Either way, we can all state our opinions on the subject, and it's up to the OP on what route he chooses since there are many options. I think the important choice is to make sure the wiring is matched for whatever route he chooses.

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**xrated** · 02-26-2022, 12:19 PM

Originally Posted by FT4NOW

@xrated I agree with what you said. The OP asked for recommendations and I gave one based on my experience with a converter I installed in my 399 when I swapped to lithium batteries. If I recall, I said it wont hurt to change out the converter, but I didnt say it was necessary.

There have been numerous discussions on this and I think the consensus is that you can use the lead acid charger and it wont hurt the lithium batteries, but on the other hand if the OP is looking to charge his bank faster he will need a higher amp converter.

Either way, we can all state our opinions on the subject, and it's up to the OP on what route he chooses since there are many options. I think the important choice is to make sure the wiring is matched for whatever route he chooses.

Sent from my SM-G950U using Tapatalk

Agreed.....I just think that most people assume that they have to change out the converter/charger, and that putting a charger in that has a specific lithium profile is always the best way to go. I actually thought that very same thing when I first started my LFP journey several months ago, but have since changed my mind. Who knows, I may end up with something that is a LFP charger, but it certainly won't be my first choice if I can make something else work. I just wish it was much simpler than it is.

**traveldawg** · 02-26-2022, 01:32 PM

I kind of want to 'weigh-in' on the which converter to use discussion.

I would recommend that your battery manufacturer can tell you what the absorption and float voltages should be. I'd try to match those specs to whatever converter/charger you purchase. Of course - this assumes one buys a Lithium battery versus building one themselves.

Some converters only provide 2 stage charging. I would recommend a 3 stage charger (bulk, absorption, float).

For example: I went to Progressive Dynamics site and looked at what they suggested for Lithium batteries; it came up with their PD9160ALV. But the specs don't necessarily say 3 stage charging. This is what they said:
Input: 105-130 VAC 50/60 Hz. 1000 Watts
Note: Units manufactured after August of 2020 have 2 stages. This applies to the PD9160ALV only. The second stage drops the voltage to 13.6 after The battery is fully charged.

Then I looked at a Victron Skylla-IP65. Wow - not cheap!! But they allow programmable charge current(s) as well as float and absorption voltages. This would be my choice.

I have a Xantrex Inverter/Charge that is programmable and set it to what the manufacturer (LifeBlue) recommends on the label on their battery(s).

There likely are other programmable charges. Given the price of Lithium batteries I would think one would want to invest good money in a charger too in order to preserve the longevity of their battery(s).