Saturday, April 1, 2023


Why do four new 100 Ah lithium batteries only charge to 13.6V?

Dear Dave,
We just installed four Battle Born lithium batteries, as the flooded batteries would not last more than about 16 hours running the residential refrigerator and even a limited 12-volt load. The RV came with no solar or solar prep. It has a Progressive Dynamics charger/2000 watt inverter and an Eclipse touchpad that controls everything.

The touchpad only has settings for flooded, gel and AGM batteries. It used to have a setting for up to 400-amp batteries, but for some reason that is disabled. I’ve set it to AGM batteries but the most it will charge is about 13.6 volts, then drop back to around 13.2 volts, where it tends to stay when plugged into shore power.

Any ideas how I can program it for lithium batteries to take full advantage of them? Unfortunately, Progressive Dynamics has not responded to my emails. —Tony, 2022 Winnebago Inspire 34T (Forza with wheelchair lift)

Dear Tony,
Winnebago uses NAPA brand lead acid batteries as standard equipment on most of their units. From what I can tell, you had four 12-volt marine/RV deep cycle batteries as standard equipment in the passenger side compartment in the back of the unit. I just got confirmation from Winnebago that they were four group 31 batteries, so you should have had almost 500 ah total. With lead acid, you can only use 50%, but that is still 250 ah. However, your 16 cu. ft. residential refrigerator will draw them down fast as the inverter is the weak link. It draws twice as much battery power as a 12-volt compressor driven model.

MagnaSine inverter by Magnum

According to the website wiring diagram and 3D drawings, the unit came standard with a 2000W inverter part number 175386-02-000. According to my Winnebago source, that was a MagnaSine inverter by Magnum, not Progressive Dynamics. If you do have a Progressive Dynamics model, it must have gotten swapped out by Winnebago’s Specialty Vehicle Department or the dealership. With the supply chain shortage we saw the last few years, anything is possible! I do not see an inverter/converter (battery charger) available on the Progressive Dynamics website, so I sent an email to my contact there to see if they have anything like that.

However, from what I can tell of the spec’s, the Magnum and the PD version are designed for lead acid or absorbed glass matt (AGM) batteries and not lithium. The initial charge stage of these and other converters/chargers is 13.6 volts until the battery bank reaches 12.6 volts. Then it goes to a maintenance or float charge of 13.2 volts, which is the point a battery will not accept a charge.

Eclipse touchpad

I’m not sure what you are referring to as the Eclipse touchpad. However, my contact in the Specialty Vehicle Division at Winnebago took a picture of what is in the unit in their shop currently.

If this is lithium compatible, you will be able to change the Battery Option to Lithium or Custom and set the voltage that the Battle Born Batteries require as well as the charge time. I would suggest contacting Battle Born to get these specifications. They will also be able to verify what converter/charger is recommended. Most lithium batteries require 14.6 volts for approximately 1.5 hours.

You cannot just replace lead acid batteries with lithium batteries without doing some research, although I hear about it all the time. Unfortunately, you will get the wrong information from some of the companies selling the lithium batteries. Battle Born, which also sells the same battery as Dragonfly in the OEM market such as Keystone, does try to educate consumers. However, I would assume you did not buy directly from them, rather a distributor who did not provide the education you needed.

If your MagnaSine 2000W power inverter/converter has a bulk stage, it might put out 16 volts to desulfate the plates and this would ruin your lithium batteries! If you can only program it to 13.6 volts maximum, then it will only charge the new batteries to about 75%, so you are losing the capacity of one whole battery!

Here is an update from Tony just received.

Hi Dave, and thanks for the response. You are correct that it has a Magnum MS2000 inverter charger.

The Eclipse touchpad I believe is made by Vegatouch and there seems to be no way to adjust any parameters.

I purchased the batteries directly from Battle Born and they’ve been somewhat helpful. After sending them pictures of my battery bank today, they suggest that I re-route the cables so all the negative leads are on the first battery and the positive ones all are on the 4th battery. Somehow this is supposed to allow the lithium batteries to synchronize better.

I find it hard to believe that a new RV would not use a charger capable of fully charging lithium batteries. Our old Itasca had a ten-year-old Xantrex inverter/charger with a lithium setting.

Below are pictures of the current battery setup, which is the exact way Winnebago had the four Napa batteries wired, the top of the original battery, the VegaTouch screen and the inverter/charger.


Here is the response and next step.

What is weird is that my stepdaughter’s fiancé runs the Specialty Vehicle Division and stated they only use the touchscreen of the picture I sent, not the Eclipse. However, your unit is at least a year old when there were some supply chain issues, so I never say never!

I have heard about several issues with the Vegatouch having problems communicating with the converter. One thing that jumps out is the 16.5v DC output rating on the label of the converter. This is a bulk charge designed to boil the lead acid batteries and break up sulfation, which will kill a lithium battery. However, I believe your Battle Born batteries have a Battery Management System which will not allow that to happen. It will also not provide a charge if the temps dip below freezing, which can also ruin these batteries.

Winnebago uses the Magnum inverter/converter as it is the best for lead acid batteries. Not everyone wants to sink $4K into lithium if they do not boondock! Plus, most boondockers will add solar, which will help top off the batteries that can only reach 13.6v, as you have found.

I’ll do a little more research on the Vegatouch. However, I would suggest adding a portable solar pack that can easily be wired with a controller in the battery compartment. That way you do not need to try and fish something from the roof.

Winnebago was puzzled why there was no pre-wire for solar, as this is something they typically do. I’m heading to Orlando, FL, this morning, but I think the first step is to see if you can manually set the voltage on the Vegatouch to a custom 14.6v. Maybe Battle Born is familiar with this, although they typically partner with Victron.

 You might also enjoy this from Dave 

Can I just swap my RV’s Interstate batteries with lithium?

Dear Dave,
Can I just remove my RV’s two Interstate 12-volt batteries and install 2 new lithium 100 Ah batteries? —Paul, 2018 Cedar Creek Hathaway 5th wheel

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


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1 month ago

Dave, I am impressed by the time and effort you put into answering the questions. Really look forward to this feature. Thanks!

Michael J Kidd
1 month ago

The Magnum MS2000 can easily be programmed to properly manage lithium batteries. The Vegatouch system is your limiting factor here. I’d suggest buying a Magnum remote control panel and plugging that into the MS2000 to set the proper values. The different remote versions enable different flexibility and settings, but even the ME-RC50 has battery type ‘custom’ which permits you to set the voltages manually for each charging stage.

Note you’ll need to unplug the phone cable from the remote port in the MS2000, then plug in the new remote. Only one control device can be connected at a time, otherwise they cause conflict.

Last edited 1 month ago by Michael J Kidd
1 month ago
Reply to  Dave Solberg

Thanks Dave!

1 month ago

So what happens when you have lithium house batteries and lead acid chassis batteries both charging off a lithium charging profile? Can’t be good for the lead acid batteries. I don’t believe a BIM is going to help unless there is a more specific kind that allows programming a chassis battery charging profile. ???

1 month ago
Reply to  Spike

Great question, hope we get an answer.

Kyle Petree
1 month ago
Reply to  Spike

They do make BIM’s specifically for this use case. Usually just referred to as a “Lithium BIM”

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