MK200 Lithum Upgrade Problem

[epearce]

So... just when you thought it would be straight forward...

• Upgraded the stock 8555 inverter to a new WFCO WF-8955-AD-MBA auto sensing main board
• I got two 12 V 100 Ah Renogy LiFePO4, replaced the two Interstate lead acid batteries.
• Turned it all on, actived the two Renogy batteries (they had already seen the charge current and activiated)

Everything was fine, disconnected from shore power, to see if I could draw the batteries down and how the solar (still the stock Furrion MPPT 25A) would do. Had the occasional problem it would revert to "Sealed", but managed to get the Lithium setting to stick with a factory reset. Now it was flashing green saying it was charging, but who knows.

Ran the RV overnight with about a 5-6 A load, was expecting it to pull the batteries down about 10-15% overnight. In the morning, everything was still alive and well.

Now, I just went out the the RV, and everything was dark. The batteries had shut themselve down, and when activated were reading only 10.5 V. When I plugged in shore power, the main breaker trips in about 20 s. Its back on solar. with the breaker reset, with the shore power unplugged, and the Furrion solar controller saying its charging (blinking green), but the voltage at the battery terminals is still only ~11.4 V.

I'm stumped.

[TucsonJim]

Eric,

Something must have been activated after this morning to draw them down so fast. Are the AC, electric water heater, etc. turned off? Are there any high current DC draws?

When they got ran down so hard and fast, it may have triggered the battery management system. I'm not sure how to get past that on a Renogy battery, so some research may be warranted.

Jim

[epearce]

I got the batteries re-activated, there is a little dongle with a button on it that plugs into an RJ-45 on top of the battery. They now appear to be charging with the solar, the voltage is almost back to 12 V, up from 11.4 V.

I really don't know what "everything was fine" would mean this morning--the lights were still on. I still don't have my Victron Smart Shunt installed, waiting on Amazon and some 2 AWG cables tomorrow. The Smart Shunt would help figure this out.

So, I'm wondering, I replaced that little Bussman resetable breaker. Is it polarized (the terminals are color coded), and allow the Converter to push more than 30 A back to the batteries?
Or, is the full drained lithium batteries and the new converter just pushing more current and would have popped the old Bussman part, or my new manually resetable Marine breaker?
Or, do I have something really wrong?

[Country Campers]

One thing I will mention is to fully charge the Lithium batteries separately before connecting them together. This makes sure that they are both fully charged and will discharge and recharge at the same rate. I would guess that the batteries are "pulling" more than the 30 amp bussman resetable breaker will handle. This is one of the reasons that it is better to get the charger/converter right beside the batteries, also keeps voltage drop down with shorter wires. There have been some recent issues with the auto detect WFCO converter/chargers also, posts are here on this site.

Brian

[howson]

epearce -- can you be more specific about the "main breaker" opening? Which breaker and what is it's rating?

[epearce]

It's the 30 Amp Type III marine breaker (https://a.co/d/8g4AQNV) I replaced the OEM broken Bussman Short Stop with. Electrically its in the same location as the OEM Bussman was, right between the battery and the 12V+ distribution.

I suppose given the fact that the converter is rated at 55 Amps you have to wonder why the original Bussman short stop ever worked, unless its polarized, or the OEM converter just never actually put out more than 30 Amps. The OEM wiring had the converting coming into the load side of the Bussman.

[howson]

...or the OEM converter just never actually put out more than 30 Amps.

Remember, too, that lead acid batteries like to recharge slowly, so even if the old converter could output more the charge profile is such that it never calls for it.

According to https://wfcoelectronics.com/product/wf-8955-mba-ad/ output power can be as high as 950W during Quick Charge mode (14.4V). 950/14.4=65A (!). A clamp meter that can measure DC current could confirm this theory. Unfortunately, if all that turns out to be the case, the OEM wiring won't handle the board's output.

How to fix? Assuming the wire from the Power Distribution Panel (PDP) is a discrete (single) wire, first option I'd look at is if it's possible to substantially upgrade the wire and breaker, since moving the WFCO is not really an option (the board is mounted internally in the PDP, right?).

Remember--breakers and fuses protect wires, not devices.

[epearce]

howson These RV upgrades are always a bit of a "Moose and a Muffin" story... Yes, the converter is mounted internally to the PDP. Yes, at 55 Amp continuous, it should be a 6 AWG (at least) from the converter to the battery. The cable on the converter itself is only 8 AWG, it looks like the OEM wiring out to the battery is probably more like 10 AWG. Its a bit a a fundamental flaw to have a 55 Amp converter in the PDP, instead of converter closer to the batteries. That will be another $50 of wire, some 6 AWG lugs, ...... I've been intending to put a small 300 W AC inverter in the cabinet, so at least I can re-use the otherwise abandoned and undersized OEM wires for that.

At least on the breaker side, that's easy, and all the individual circuits are protected by 30 A inline fuses, so upgrading that to 60 A should not be an issue.

I'm surprised no one else updating the GD to a two-lithium battery upgrade has not run into this problem, or do that just have the Bussman tripping and resetting down on the tongue and never even know.

[acoleman43]

epearce I literally LOL reading your post.

In my adventures in modifying the electrical components in an RV I have found the same thing as you are finding. minimum, minimum, minimum standards. when I added/replaced with lithium batteries I ended up re-doing most of my electrical system and oversized wires/cables for very low voltage drop. That was not cheap.

I think Howard has you in the right direction. He's a smart dude.