Lithium battery in Lil Snoozy

[Fallon]

Originally Posted by CarlD

Doug,
I re-read your original post and have one concern regarding the 300 amp fuse. Because the battery can deliver high currents does not mean you should base your fuse size on it. The purpose of fuses, in most cases, is to protect the wiring from overheating and burning up...

You are so very correct. Fuses (and circuit breakers) protect your wiring, not anything plugged into or connected to that wiring. Always fuse based on the smallest piece of wire in a given circuit. Otherwise there is the potential for that wire to turn into a red hot heating element catching everything on fire. Going a size, possibly 2 higher for wiring is always a good idea (and use a fuse for the next size down). Less risk of any problems & less voltage drop due to the smaller & higher resistance wire turning it into heat.

I have a Trimetric & associated SC-2030 charge controller in my rig & it works great. You can put in custom charge profiles for all sorts of batteries, including lithium. I use a suitcase solar panel for now, but intend on replacing that with a hard mounted charge controller this year for convenience. If you have a dumb converter, you can upgrade it to a smart converter without replacing it by running it's 12v output through the SC-2030 or similar charge controller. It will tend wet cell batteries better, or do lithium as well.

I have a 20ah hour LiFePO4 battery for a ham radio & networking go box along with a Epic PWRgate to act as a UPS & charge controller. Works well and rated to 40@ so within the usage range for our Casita, but not quite setup for RV usage. I wanted a bigger battery with thoughts of putting it in the Casita as well, but it was just to expensive.

[gordon2]

Originally Posted by Fallon

...If you have a dumb converter, you can upgrade it to a smart converter without replacing it by running it's 12v output through the SC-2030 or similar charge controller. ...

I had the same thought some time ago, and decided against doing that. See:

http://www.fiberglassrv.com/forums/f...put-76442.html especially the links in post # 10.

Tell me, have you done it that way, or know of someone who has? My electrical engineering knowledge is a little shy of sufficient to fully understand the issues of a PWM power supply feeding a PWM charge controller.

Also, I have the Trimetric and companion SC-2030 solar controller and I agree it works well. But I am confused about your statement that you have a SC-2030 solar controller and:

Originally Posted by Fallon

I use a suitcase solar panel for now, but intend on replacing that with a hard mounted charge controller

I have a suitcase (portable) panel that feeds the SC-2030 which is mounted inside the trailer. Thats is to say no controller in the suitcase. So where is your SC-2030? Is it used with the suitcase panels, panel(s) on the roof, or what? Just wondering...


73

[Air Doug]

Originally Posted by Fallon

You are so very correct. Fuses (and circuit breakers) protect your wiring, not anything plugged into or connected to that wiring. Always fuse based on the smallest piece of wire in a given circuit. Otherwise there is the potential for that wire to turn into a red hot heating element catching everything on fire. Going a size, possibly 2 higher for wiring is always a good idea (and use a fuse for the next size down). Less risk of any problems & less voltage drop due to the smaller & higher resistance wire turning it into heat.

One of the reasons I posted was to get feedback from other folks with different experience from me and a different set of eyes on what I did. I really appreciate the feedback and you have caused me to re-think my fusing.

As I said in an earlier post, the wiring for all the trailer loads is protected by a 30 amp automatic circuit breaker that came with the trailer and that I incorporated into my system. I looked at the wiring sizes and think that it should be fine. The only questionable one was from the charger/converter and both the unit and the wiring has now been upgraded.

Which brings me to the 300A fuse on the battery. My goal was to protect the system from a dead short across the battery or the charging wiring. The wire from the charger converter is about 7 feet of 6 gauge wire. It is oversized for the 60A capacity of the charger. But what about the fuse? The charger/converter has its own current limiting circuits and reverse polarity fuse protection. So I was really worried about the wire itself.

But I watched this video and used the 300 amp fuse because of it. My wiring is marine rated 6 gauge.

https://www.youtube.com/watch?v=y3gzhep8w4A

Relooking at the ampacity charts, maybe I should have used something less than 100 amps. That would protect against a partial short.

So plenty for me to think about. Thanks again for the thoughtful input.

[Fallon]

Originally Posted by gordon2

I had the same thought some time ago, and decided against doing that. See:

http://www.fiberglassrv.com/forums/f...put-76442.html especially the links in post # 10.

Tell me, have you done it that way, or know of someone who has? My electrical engineering knowledge is a little shy of sufficient to fully understand the issues of a PWM power supply feeding a PWM charge controller.

Also, I have the Trimetric and companion SC-2030 solar controller and I agree it works well. But I am confused about your statement that you have a SC-2030 solar controller and:



I have a suitcase (portable) panel that feeds the SC-2030 which is mounted inside the trailer. Thats is to say no controller in the suitcase. So where is your SC-2030? Is it used with the suitcase panels, panel(s) on the roof, or what? Just wondering...


73

The charge controller is mounted in the converter compartment. I have a pigtail with Power Poles that will reach the hatch. I put the standard MC4 solar connectors on the end of a heavily insulated former power cord about 20' long. That stays permanently connected to the Renology suitcase panel as there is room for it between the panels when folded up & the MC4 connectors are a pain to separate. Power Poles on the other end. The power Pole connection is made inside the hatch for security & as they aren't sealed or weatherproof.

Generally you want your charge controller to be as close to the battery as possible to avoid voltage drop. There is voltage drop between the panels & controller, but that's at a higher voltage & dropped down by the controller anyway.

My suitcase setup works good, but is a bit of a pain to always setup & tear down. Im planninh to hard mount a panel on the roof so it's always there & maintaining the battery with no effort on my part. I know full well it will be in the shade more than the suitcase setup. But half my intent is maintaining the battery when not camping as much as when we are. I'll likely leave my power pole pigtail there so I can run both panels if need be. I'll keep the suitcase rather than sell it. I c as n use it for some of my HAM radio field stuff.

[gordon2]

Originally Posted by Fallon

The charge controller is mounted in the converter compartment. I have a pigtail with Power Poles t...

I have done similar except the solar controller, shunt for the Trimetric, etc are in the front hatch under the sofa (front sofa model Scamp), so that the wire run to the battery is a short length of 8 gauge. At the far end of the suitcase wires I have MC4 connectors and then a pigtail with MC4 on one end and a 30 amp Trolling motor plug on the other. A trolling motor socket is installed in the camper's body near the tongue. That way it takes two seconds to plug the panels in, and I can switch out the 100 watt suitcase for a 50 watt flex, or any other panel(s) by using the MC4 connectors on the pigtail (about a foot from the camper). BTW, I found that if you use all MC4 connectors from the same manufacturer they are easier to use. At least that is true for Renogy brand MC4 which I can do by hand (with the tool). I switched out any non-Renogy MC4 for Renogy ones.

Sorry to go off topic, but maybe this will be good info.

[Bill Lindenfelser]

Doug,
I also recently upgraded our 2015 Trillium electrical system. We managed to kill deep-cycle, Pb/acid, 80A-hr batteries about once/year, and were constantly on the edge of dropping below the minimum 11.7V required by the Dometic electrical fridge. (Nominal power: 40W.) The other significant load is probably the sound system, an after-market car device with a power-sucking bass capability. Lights are LEDS throughout.
Joe at backcountrysolar.com set us up with a BB 100A-hr LiFePO4 battery, and a 160W Zamp portable solar panel. We also added a 30A Zamp digital solar controller. We left the original 80W solar panel on the Trillium roof and simply wired it in parallel with the socket for the 160W portable.
The initial run with this setup was on our annual late-winter trip to the Southwest, where all performed flawlessly over 7 weeks. The portable panel only got used when we found that odd camping spot under towering Ponderosa pines.
The key difference was the BB battery. Only once did the voltage drop to 12V. The Zamp controller was the first time that this retired EE had a chance to see the electrical system performance in near-real-time.
I did not change out the Wfco lead/acid charger, given assurances from BB that it would do no harm. And because we never did plug in on that 7-week trip, it was never a concern. And, frankly, I had not considered the possibility of back-charging the car and therefore did not put in isolation, or, better, a DC-DC booster. Thanks for that suggestion.
We'll be doing some outings in the Northeast, where insolation is a bit less than in AZ and NM. Let's see what happens there.
These little plastic boxes are projects, aren't they?
Regards,
Bill

[Air Doug]

Bill,

It is good to hear your experiences in the southwest as I am now in the midst of the solar panel upgrade. Please do let us know how your system performs during your northeast trip.

Yes, these are projects, which I find to be a lot of fun.

Doug

[Banjo Bob]

Thanks to all who contributed to this thread. I've sold my tent trailer and I'm awaiting the Snoozy. I've never hooked up to power so I'm interested in being able to remote camp for 4 - 5 days and taking some power with me. My house is solar powered so I have some basic knowledge. I've got a lot of reading to do.

[Air Doug]

Originally Posted by Banjo Bob

Thanks to all who contributed to this thread. I've sold my tent trailer and I'm awaiting the Snoozy. I've never hooked up to power so I'm interested in being able to remote camp for 4 - 5 days and taking some power with me. My house is solar powered so I have some basic knowledge. I've got a lot of reading to do.

We just got back from a week-long trip with the Snoozy. Longest stretch without power was 45 hours. We used the fan for about 15 minutes and the water pump only for flushing. Lights were used at night but generally only to prepare for bed. The fridge was the main load. Temperatures were 90's day and 60's night. Total power used was 59.5 Ah. The average draw was about 1.3 amps/hour.

On the five hour drive home, with the fridge still on, the truck recharged the battery 30 Ah.

[buff30]

Doug,
I want to thank you for the information in this thread. It has completely changed my battery plan for my camper. I am planning to construct my own bank out of 4 individual LiFePO4 cells. And a separate battery management system.

I have a question about your DC to DC converter. Have you measured the voltage at the input of the Converter? Or the voltage at your vehicles battery when the alternator is changing. I am curious about the voltage drop in your setup.

[fofobraselio]

Replace the stock 12 gauge charger/converter wiring with 6 gauge so you can charge at up to 60 amps.

You'd think they would wire it properly. Thanks for this tip. I'll have to do that with my converter for sure

I have also installed a Li battery in my trailer and am going to charge via TV battery with the TBCM-40A.

I am also very pleased that you can put this battery on its side.

Sent from my ONEPLUS A3000 using Fiberglass RV mobile app

[Air Doug]

Originally Posted by buff30

I have a question about your DC to DC converter. Have you measured the voltage at the input of the Converter? Or the voltage at your vehicles battery when the alternator is changing. I am curious about the voltage drop in your setup.

I measured voltage at the battery then went to measure input and output at the DC/DC converter. The battery was easy but the converter would have required me to uninstall the wires and put in jumpers, which was more work than I wanted to do. But when charging on the road with a partially discharged battery, the 9 amp rated converter charged at 8.5 amps, so I figured voltage drop was not an issue with my setup. Remember that I doubled the 12 gauge wire in the trailer, from 7-pin connector to the converter. I hope this helps.

[Air Doug]

Originally Posted by fofobraselio

You'd think they would wire it properly. Thanks for this tip. I'll have to do that with my converter for sure

Fiberglass RV mobile app

Well, the Snoozy wiring was for a lower amperage rated charger/converter, so it didn't need the 6 gauge wiring for the 60 amp charger I installed. But I agree, Snoozy undersized the wiring - 12 gauge is too small for the WFCO 35 amp charger that came with it.

[buff30]

No worries thanks for the help.

[John in Santa Cruz]

3 feet of 12 gauge at 60 amps would have a 0.3 volt drop. Note the charger is only outputting its max current when the battery is heavily discharged, as the battery charge voltage rises, the current drops so that voltage drop reduces proportionally... 6 gauge is probably total overkill, I bet 10 ga would have been sufficient here, unless you've got a long run form the charger to your battery.

[Air Doug]

Originally Posted by John in Santa Cruz

3 feet of 12 gauge at 60 amps would have a 0.3 volt drop. Note the charger is only outputting its max current when the battery is heavily discharged, as the battery charge voltage rises, the current drops so that voltage drop reduces proportionally... 6 gauge is probably total overkill, I bet 10 ga would have been sufficient here, unless you've got a long run form the charger to your battery.

John,

I do have a long run from the charger to the battery; Lil Snoozy puts it on the other side of the RV, so it runs about 7 feet. The Blue Sea Systems ampacity chart I used says to use 6 gauge for a run of 7 to 10 feet, for 60 amps, with a 3% voltage drop. It actually says to use 6 gauge for 0 to 6 feet also. Here is the link to the site I used:
https://www.bluesea.com/support/arti...r_a_DC_Circuit

So maybe they are too conservative but when my battery is pretty depleted, the charger is putting out 59+ amps and the 6 gauge wire is warm. It continues to put out over 50 amps for much of the charge cycle because the charge curve of the Li battery is so flat until it is almost charged.

Doug

[John in Santa Cruz]

ah, cool. yeah, 7 foot run, and its actually running 60 amps most of the charge? I retract whatever I said...

hey, is the lithium charge controller monitoring the temperature of the lipo? those things get WARM when they are being charged, and if the temp gets too high, the charger really should back off, or they can go BOOM.

[Air Doug]

Originally Posted by John in Santa Cruz

hey, is the lithium charge controller monitoring the temperature of the lipo? those things get WARM when they are being charged, and if the temp gets too high, the charger really should back off, or they can go BOOM.

Battle Born says each individual cell is monitored for charge and high and low temperature. The BMS is built in to the battery. I think that is the "drop-in replacement" part of their claim -- I don't need a separate battery monitoring system, including temperature.

Also, to clarify, 59.5 amps is the highest I have seen and it doesn't charge at that the whole time, it does drop off. But is stays in the 50s for a long time. I really love that about the battery because it is totally charged in a couple of hours.

[buff30]

I discovered another solution to the problem of charging lithium from an alternator.

https://battlebornbatteries.com/ster...ttery-charger/

Sterling Power offers several models depending upon system needs. It is a step up DC to DC constant current battery charger. I believe it it can also act as a battery isolator separating the tow vehicle charge system from the campers system. I am still trying to figure out if it accomplishes this through solid state or a standard relay.

I think this model would fit the bill for most of us however they have lower and higher amp rated models.

Sterling Power battery to battery charging system - battery to battery charger, marine grade DC powered charger

[buff30]

Doug,

For what is worth from my training and years of experience as an aviation electrician I believe you have designed an effective system. Like others have voiced I would definitely change out your main 300 amp fuse and this is why. Starting with the BB 100ah battery, it's max Continuous discharge current is rated as 1C or 100 amps. It has a 2C, 200 Amp Surge Current (30 Seconds) and 1/2 second surge for higher loads. That being said you should never be drawing much over 100 amps from the battery. So a 1000 watt inverter is the max you could run off this battery, depending on efficiency and load it would draw about 100 amps DC at full load. The BB-100's internal BMS is designed to disconnect the internal battery cells from the external battery posts if the load is between 101 to 200 amps for more than 30 seconds and 201 or greater amps for .5 seconds. That all being said the safest thing for the battery is to never subject it to the overload conditions. As long as the electronic BMS does not fail or malfunction it should provide a level of safety from an overload or direct short to ground. I personally know that even the best design and manufacturer electronic circuitry is subject to failure. In the aircraft industry and I am sure other industries they design levels of redundancy to mitigate the risk of failure of critical systems. In this case a properly sized fuse can act as a level of redundancy for this function of the BMS. A 125 to 130 amp fuse connected directly to the positive terminal of the battery would allow you to use a little of your overload capacity before opening keeping your expensive battery far away from its damaging over load range of 200 amps.

As far as protecting the wires between the battery and the loads-charging sources I can only speculate as I have not seen a schematic of your system. From studying the posts I will explain how I pictured myself setting up your system. This advice is only valid if your system is wired exactly as I describe. If you have a sketch I would be happy to take a look.

From the 125 amp fuse mounted directly on the positive post I would run 6awg duplex cable, positive wire to the 60 amp charger and negative wire directly from your negative bus near the battery to the charger. The 125 amp fuse is at the max for this wire size but is in the safe range. Also from the 125 amp fuse you need to connect your DC loads. You said your loads were protected by a 30 amp circuit breaker. This needs to be placed as close to the main 125 amp fuse as possible as any length of wire between the main fuse and the 30 amp breaker will not be protected unless it is also 6awg or larger. If your new battery is not in it's original location you would need to ensure the wire supplying the panel is still sufficient. I am not sure where your DC-DC converter is connected to the system but if it's mounted right next to the battery with a short direct run or wire, a separate fuse between it and the battery may not be required. If that is the only connections to the positive side of the battery I think you would be good. Where is your main disconnect switch located? Negative or positive side?

I will write a separate post about your charge rate.

This is only constructive criticism and not intended to be an internet arm chair expert one upper. Like I said before I appreciate the contributions that this thread has brought to our little community.