Lithium battery in Lil Snoozy

[buff30]

As far as the ideal charge current I cannot find a single spot on Battle Born's web site where they specify the recommend charge rate or max charge rate. I am pretty certain BB doesn't manufacture the cells they place inside their batteries as I am not aware of a source outside of China for LIFEPO4 cells. Cell manufacturers normally publish this data on a spec sheet. I know they use cylindrical cells from a YouTube video were I could see their batteries being assembled in the background. So I will use the common 10ah 3.2 V cell for discussion. And industry standards for LIFePO4 in general.

http://www.batteryspace.com/lifepo4-...-3-passed.aspx

This cell recommendeds a charge rate of 2C, and a max of .5C however it does alow a rapid charge of 1C.

IEC standard for LiFePO4 state the cell should last for > 2000 cycles and retain 80% of initial capacity of the cell when changing at a 0.2C rate.

Most manufacturers list their charge rate at .25C to .5C. Following theses guidelines would give us a 25 to 50 amp charge rate on a 100ah battery. Staying within these parameters would likely result in the best longevity. However depending on the individual requirements of a particular system, a shorter charge time my be more important than long battery life. If I was designing a 100ah LiFePO4 I would go with a 30 to 40 amp charge rate.

This doesn't mean a .6C rate is unsafe if the manufacturer doesn't forbid it as most LiFePO4 allow up to 1C charge rate.

[John in Santa Cruz]

the chinese are *terrible* on specs and documentation for electronics and software.

[buff30]

I did some more research and found out lithium cells are actually produced in several countries. I think I got confused when I read that China was one of the largest producers of lithium as a raw material. I found this article about cell production interesting.

(Edit- This doesn't refer to LiFePO4 cells specifically. Just lithium-ion.)

Lithium-ion batteries – How they are produced and forecasts of a fast-growing industry – North American Graphite Mine – Mine de graphite nord-américaine

[Glenn Baglo]

I hear the US will soon be introducing batteries made of coal.

[Air Doug]

Originally Posted by 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

Gene,

I looked at the Sterling also. The reasons that I went with the Victron were:
- $65 Victron vs $290 Sterling
- 9 amp charge rate Victron vs 30 amp Sterling (smallest models of both). With my tow vehicle and trailer wiring through the 7-pin connector, I don't think I can support much more than 10 amps. I didn't want nor need a dedicated charging wire from the alternator to the trailer.
- The Sterling is complicated to set up and has features I don't need, like regenerative braking features. Simpler is better for me.
- I called Battle Born and they discouraged me from buying it because of it's complexity. I can't find that they sell it any more, even though you can find info on their website about it. They used to sell it.
- Battle Born's Q&A on it recommends the Sterling it for a system of 300 Ah or larger.

Anyway, the Sterling may be perfect for some setups but I felt more comfortable with the Victron.

As always, thanks for your input.

Doug

[Air Doug]

Gene,

Thanks for your thoughtful analysis of my system in post #40 and for taking the time to comment. I will be making at least one change as a result. Responses to your points and questions follow. Let me know if I missed something.

I still can't figure out how to post pictures, or I would have already, including a simplified wiring diagram. I'll try again.

- One thing not obvious in my description is that the main cutoff switch is a 2-way switch mounted close to the battery. One input is the 6 ga wire from the charger. The other input is 6 ga wire from the battery. Output is 8 ga wire to the 30 amp circuit breaker. I run the switch set to 1+2, so I can charge and run the loads from both simultaneously. I can isolate the battery or the charger from the loads by selecting 1 or 2 individually. Fourth position is "off."

- Thanks for explaining the main fuse situation so clearly. It cleaned up my fuzzy thinking on it. I will be replacing the 300 A fuse with a 125 A asap.

- Your vision of my system is about right. I wish you could see the diagram but you seem to have figured it out.

- The main fuse is on the positive battery post.

- 6 ga wire goes from positive battery terminal to main cutoff, then to charger.

- 6 ga wire goes from charger to the shunt and then the negative battery terminal. Ground bus is connected to shunt about 2" away.

- I moved the 30 A circuit breaker for the loads from dangling in the air as installed by factory to the bulkhead next to the battery. About 5 " of 8 ga wire goes from the main cutoff to the circuit breaker. As stated above, the rest of the wiring from the positive terminal or charger is 6 ga. You were recommending that I should make this 6 ga. But for such a short run, 8 ga should easily carry hundreds of amps (protected by my new fuse - thanks!). Am I thinking about this right?

- Battery is in the factory location.

- DC/DC converter is wired on the positive side with 7" of 12 ga wire and an in-line 10 A fuse.

Again, I really appreciate you taking the time to think through my system and offer your advice. As I stated in my original post, I am a geologist, not an electrical engineer, and lie awake at night thinking through this stuff trying to make sure I get it right enough to be safe. Input from you and others is why I joined this forum.

Doug

[Air Doug]

Gene,

Your post #41 on charging rates expresses very well a persistent worry of mine. Yes, you are right, I value a faster charging rate over longevity. Ultimately I am okay with the charge rate I have from the Progressive Dynamics charger as it limits generator run time.

A related issue is how much to charge the battery. Battle Born states that they limit the voltage in the battery to 14.6 volts in order to assure 3000 to 5000 cycles. In my experience, 14.6 volts is where mine tops out.

BB says on their website (discussing chargers):

The bulk and absorption voltages typically vary between 14.0 and 14.8 V and the float can vary between 13.2 and 13.8 V. The 12V Battle Born batteries sit comfortably right in the middle of these ranges. We recommend a bulk and absorption voltage of 14.4V. A float is unnecessary, since Li-ion batteries do not leak charge, but a floating voltage under 13.6V is fine.

14.6 volts is the rated limit of the Progressive Dynamics charger, which Battle Born sells. I would prefer that it stop at 14.4 or so and only saw recently that they can set that at the factory for something other than 14.6. Had I known that, I would have done that. I am surprised that BB doesn't custom order PD chargers set to 14.4 volts. When I can, I turn off the charger when it reaches 14.4 volts or so. In the end, I decided to stop worrying about it and trust the design and internal BMS of the battery.

Doug

[fofobraselio]

As far as charging from the TV goes, there is always this guy http://atkinsonelectronics.com/manuf...s/TBCM-40A.asp
The charge level is too low to depend on it solely as your battery charger but I feel with its low draw it may not be considered harmful for a Li battery.
I haven't used it yet but Ill gladly throw down some numbers when it's in full swing.

Sent from my ONEPLUS A3000 using Fiberglass RV mobile app

[buff30]

Anyway, the Sterling may be perfect for some setups but I felt more comfortable with the Victron.

Doug,
I don't think their is anything wrong with the Victron I was only searching for more options. Once I decide on the size of my battery bank I will select the appropriate DC to DC converter and wire size from my alternator. And I think I strive for complexity sometimes.

[buff30]

But for such a short run, 8 ga should easily carry hundreds of amps (protected by my new fuse - thanks!). Am I thinking about this right?

Just running it through my circuit calculator says no, max fuse size to protect 8 gauge wire is 60 amps and I guessed that your wire had the highest insulation rating available. That all being said if it is only a 6" run and the chances of it shorting to ground are essentially zero based on where it is installed I would not worry about it. It is almost impossible to protect every inch of wire. I will have a 4 foot section of 6awg that will be un fused as my system design prohibits it. I will ensure it will not be able to come into contact with ground and I will probably protect it in non conductive conduct or nylon braid.

What is the insulation temperature rating on your heavy gauge wire? Did you say your charging wire gets hot?

[Air Doug]

Originally Posted by buff30

JThat all being said if it is only a 6" run and the chances of it shorting to ground are essentially zero based on where it is installed I would not worry about it.

What is the insulation temperature rating on your heavy gauge wire? Did you say your charging wire gets hot?

The wire is in a secure spot but I will move the wire a bit and add a wire anchor to make sure it can't reach ground. Thanks for the analysis.

6 gauge wire is 600V marine wire rated at 105 Celsius. It doesn't get hot. It gets a little warm to where you can tell, but no more than that.

[buff30]

Doug,
In reply to post #47.
"Out of the Battle born manual.

For your Bulk/Absorption stage, the ideal voltage is between 14.2v-14.6v. This range will allow the battery to fully charge any higher then this and the built in BMS will send the battery into a protect mode.

All Battle Born Batteries come with a built-in battery management system (BMS). Our BMS allows us to create one of the safest LiFeP04 batteries on the planet. To help us keep our promise that our batteries will last for 3-5000 cycles, our BMS will put the battery into a protect mode in the event the battery falls outside of one of the following parameters.
High voltage: 14.7v-15.0v
Will not allow any more current into the battery."

So 14.6 volts are within their charge specifications. I would not worry about it as long as your BMS is not disconnecting the battery on a regular basis. The real issue is not the total voltage applied to the pack but ensuring individual LiFePO4 cells don't go over 3.65±0.05V. Their will be four strings of batteries connected in series in your battery so 3.65 +3.65 +3.65 +3.65 = 14.6V.

Standard charging: first charged by constant current of 0.5C, then by constant voltage up to 3.65v, and when the current falls down to 300mA, then stop the charging. On the - side 3.6v per string would give you an overall voltage of 14.4. The top end of the charge range of 3.7v per string would give you a pack voltage of 14.8v. If the BMS disconnected at 14.7 pack voltage it still leaves you a .025v per cell margin of error. But remember the BMS monitors individual string voltage and will disconnect the whole battery if a single string is out of tolerance. All these specs are based on a different LiFePO4 cell that I have access to the data. I wonder what cell BB uses in their packs?

http://www.batteryspace.com/prod-specs/7493.pdf

All in all I think you are probably ok. If you really wanted you could probably send your charger to Progress Dynamics for adjustment.

Doug if you want to PM me I can pass you my direct contact information.

I am far from an electrical engineer, I have just fixed and installed hundreds of millions of dollars of electronic and electrical equipment in my day.

[buff30]

#48
Today, 09:19 AM
fofobraselio
Join Date: Jun 2015
Posts: 111
As far as charging from the TV goes, there is always this guy http://atkinsonelectronics.com/manuf...s/TBCM-40A.asp

. This is not a booster so it will not increase the voltage. This is useful if your vehicle doesn't have a charge wire that disconnects when the vehicle is shut off or you want to increase the current carrying capacity of the trailer charging circuit.
I believe the Sterling includes this disconnect circuitry and a boost converter to increase the voltage. I still need to research it.

I have used this product in the past on an overland vehicle dual battery system and was very pleased with the results. It is similar in operation to Atkinson.

Isolators | Combiners | Solid State Relays | Hellroaring Products

[Air Doug]

I finally finished everything and tried it out for 2 1/2 weeks in July. Everything worked fantastic.

Main additions since my initial post are a Victron 100/30 MPPT charge controller, a 30 amp circuit breaker for the solar input, and a 30 amp fuse between the MPPT controller and battery. We have a 100 watt solar panel with 25 feet of 10 gauge wire - Anderson PowerPole connectors on the Snoozy end and MC4 on the panel end. I also moved some wires around as suggested by commenters and changed my main battery fuse to 125 amp.

The Victron DC/DC converter assured that we were at or near full battery capacity every night that we were on the road. We often were at camps with hookups but we didn't use the electric hookup unless we wanted to use the AC or hot water. We boondocked for 6 days in Montana and parked under a huge cottonwood that shaded the trailer except for a couple of hours in the morning and 45 minutes before sundown. I moved the solar panel to face the sun when I was around. We used an inverter to run a cellular WiFi hot spot and charge computers. We ran the generator for 30 minutes when the charge dropped below 50% although we easily could have not done that. I was mainly checking out the systems.

There is a picture of the wiring in the album Terragrin that I will try to link here. No guarantees of success.

[buff30]

The system is looking real nice Doug!

[Air Doug]

I have done a little more work and also finally have a wiring diagram to post.

We added a second Battle Born battery to give us more flexibility on boondocking without the generator or rainy/shady days.

Another benefit of going to two batteries is that maximum charging rate from the 60A Progressive Dynamics converter goes from .6C to .3C without sacrificing any reduction in amp-hours gained per unit of time.

We also added a second charger. This one is a little 3A unit and the output goes to the terminals of the PD charger for simplicity. Both chargers are plugged into an outlet in the basement of the Snoozy. The outlet is wired with split plugs controlled by a 1-off-2 switch near the control panel inside the trailer. From the factory, the Snoozy charger is running whenever you are connected to shore power, unless you physically unplug it. That is fine for float charging lead acid but I wanted to be able to easily (with the flip of a switch) stop charging the Li battery at less than full capacity for battery longevity. The 3A charger is also easier on the batteries if we are not in a hurry. It is about enough to keep up with the TruckFridge too, which is the main power hog in the trailer.

I think I am done with the wiring diagram, too. Hopefully no mistakes.

[CarlD]

Doug, I have a question regarding the 30A fuse in line with the solar panels. I also have a fuse in this location, but I installed it blindly because the manufacture recommended it. I may be missing something here, but what scenario will cause this fuse to blow? The solar panels have a current limit that, I assume, is less than fuse value, so there is no scenario there that could blow the fuse. Is there some kind of back feed mechanism in the MPPT charger that could feed battery current to the panels? Do you have any insight?

[Air Doug]

Carl, I have a 30A circuit breaker/switch combo on the feed into the controller because the manufacturer recommended it - same as you. Its a 30A controller so that kinda makes sense. I also wanted a switch so that I can make all the panel connections first then switch on the controller and the switch/breaker was a good way to get that. I never thought about it much because with 205 watts of solar panels we rarely approach 10A output from the controller. I've never measured input. I might add another panel or two some day, but still that would be below 30A. But thinking about it now, I guess if you had enough panels you could get near 30A, but you would need a bunch considering the panels' higher voltage. The 25 feet of 10ga wire we use between the panels and controller would handle 30A at 12V, more at higher voltage. Maybe that is what the manufacturer is thinking.

[Jon Vermilye]

Many solar controllers require the battery to be connected to the controller BEFORE connecting the solar panels. A switch, breaker or fuse between the panels & the controller is a good idea since you would otherwise need to disconnect the controller from the batteries at night or cover the panels.

I have a 30 amp breaker on each side of the solar controller.

[CarlD]

Jon,
My solar controller (Renogy) stated this also 'battery first', which is why I installed a 2 pole switch for my battery disconnect. It disconnects the solar panels at the same time as the batteries. I also have a switch just for the solar panel circuit. The conundrum with fusing the solar panels is the same as fusing a current limited power supply. If it will put out 10 amps and you would like to use it a full capacity, you would have to fuse it for more than 10 amps. The fuse would never blow. Here is how I wired my trailer.