Converting to Lithium - Fiberglass RV



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Old 05-23-2019, 05:23 PM   #1
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Converting to Lithium

I've started documenting the move from a pair of 6V lead acid batteries to a pair of 100 amp hour Battleborn lithium batteries in my Escape 21. This will also involve the changing of the charging section of the converter, a new battery monitor & solar controller.

I will be adding to the page as the conversion continues. If anyone has questions, I'd be glad to try to answer them.

Changing from Lead Acid to Lithium Batteries.
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Old 05-23-2019, 05:58 PM   #2
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Jon,


I read your blog and everything looks ok except that the Battleborn LFP should be charged at 14.6 volts. The BMS will disconnect just below that value when fully charged.


Also, if you intend to charge the battery from your tow vehicle you will need a DC-DC converter. I am using a 9 amp isolated victron model. I see Renogy has a 20 amp charger which might be suitable. Set it to the same voltage as your Progressive Dynamics power supply. The battery will take care of itself.



So far my Lil Hauley build has been working great with the above design parameters. Last weekend I parked the trailer for a day with the TruckFridge 130 running in 60 degree ambient and it consumed 20 ah in 16 hours.
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Old 05-24-2019, 09:39 AM   #3
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Thanks for doing this Jon. We will be following your progress.

Richard
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Old 05-24-2019, 12:51 PM   #4
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Jon,


I read your blog and everything looks ok except that the Battleborn LFP should be charged at 14.6 volts. The BMS will disconnect just below that value when fully charged.


Also, if you intend to charge the battery from your tow vehicle you will need a DC-DC converter. I am using a 9 amp isolated victron model. I see Renogy has a 20 amp charger which might be suitable. Set it to the same voltage as your Progressive Dynamics power supply. The battery will take care of itself.



So far my Lil Hauley build has been working great with the above design parameters. Last weekend I parked the trailer for a day with the TruckFridge 130 running in 60 degree ambient and it consumed 20 ah in 16 hours.
While 14.6 is acceptable, Battleborn recommends charging at 14.4V & when full, a float of 13.6V.

One possible concern - if the Battleborn BMS disconnects the batteries when full, the solar controller will effectively be disconnected from the batteries, but still be connected to the solar panels. This is not recommended by Victron or most other solar controller manufacturers. Any thoughts?
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Old 05-24-2019, 03:09 PM   #5
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Would it be possible to install a relay in the line between the controller and the solar panels that would open upon loss of power to the battery's BMS, in order to open the circuit to take the solar panels off the controller until the power comes back on?
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Old 05-24-2019, 04:04 PM   #6
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Would it be possible to install a relay in the line between the controller and the solar panels that would open upon loss of power to the battery's BMS, in order to open the circuit to take the solar panels off the controller until the power comes back on?
I may be over thinking this. I don't believe the battery would completely disconnect from the trailer wiring since that would shut down the 12V system. I think I'll give Battleborn a call since this would be likely to happen with most systems. A diode in the BMS would seem to solve the problem...
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Old 05-24-2019, 08:43 PM   #7
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Many controllers require the battery be connected before the solar cells to prevent damage to the unit.
Loss of 12 volts to the controller with the solar panels hooked up could be a bad thing indeed.
Way back the systems had a "dummy" load to absorb the excess power in this case,
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Old 05-25-2019, 06:24 AM   #8
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I do not own any battle born batteries but it seems to me like you are overthinking this as well. The BMS should only disconnect the incoming power from the charge controller, not disconnect the battery from the entire system. Like a cell phone being charged, once the phone is full, it no longer accepts any more charge but it is still operable when plugged into the charger. The phone doesn't shut off.


If you have a Victron MPPT charger, you can also customize the charge parameters to match the parameters on the battle born batteries BMS. This way the charge controller and the battery BMS are going to run through the same charge operations at same time under the same voltages.
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Old 05-28-2019, 07:33 AM   #9
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I have been away for a few days swatting mosquitoes in Canada. For me the Progressive Dynamics charger and the solar system are mutually exclusive. I only use the solar panels if we are boondocking and use the Progressive Dynamics charger when we are at a campground or at home.



I am aware of the warnings in the Renogy MPPT controller manual regarding connection of the battery prior to connecting the solar panels, but do not fully understand why. If you have a battery it can source and sink current to a system, where as a power supply will only source power. If the MPPT controller only requires a power source on the battery side then it should not be damaged by having a power supply connected without a battery. This is a good question for Renogy.



The BMS is internal to the battery and disconnects it from the circuit when fully charged, however the power supply or solar controller would still be connected and supplying the load. The moment you turn off the power supply or solar panel the voltage drops and the battery turns on. I have watched this in my system. It seems to me that the voltage settings of the MPPT are important so that it does not cause the battery to turn off if the voltage gets to high, as it could potentially damage the MPPT controller. My Renogy Rover has a Li setting for the battery, so I assume they have a design that properly charges the battery but not damage the controller when the battery is fully charged.
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Old 05-28-2019, 11:54 AM   #10
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Originally Posted by CarlD View Post
I have been away for a few days swatting mosquitoes in Canada. For me the Progressive Dynamics charger and the solar system are mutually exclusive. I only use the solar panels if we are boondocking and use the Progressive Dynamics charger when we are at a campground or at home.



I am aware of the warnings in the Renogy MPPT controller manual regarding connection of the battery prior to connecting the solar panels, but do not fully understand why. If you have a battery it can source and sink current to a system, where as a power supply will only source power. If the MPPT controller only requires a power source on the battery side then it should not be damaged by having a power supply connected without a battery. This is a good question for Renogy.



The BMS is internal to the battery and disconnects it from the circuit when fully charged, however the power supply or solar controller would still be connected and supplying the load. The moment you turn off the power supply or solar panel the voltage drops and the battery turns on. I have watched this in my system. It seems to me that the voltage settings of the MPPT are important so that it does not cause the battery to turn off if the voltage gets to high, as it could potentially damage the MPPT controller. My Renogy Rover has a Li setting for the battery, so I assume they have a design that properly charges the battery but not damage the controller when the battery is fully charged.
I talked with Battleborn, and this is pretty much what they said. As long as the solar controller is set for 14.4V bulk/absorption & a float of 13.6V, and the absorption time is set for 1/2 hour per battery, the battery will not see an over charge & the BMS will not disconnect the battery. If your controller has a "never exceed" voltage setting, set it for 14.7V.
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Old 05-28-2019, 05:49 PM   #11
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[QUOTE=CarlD;743189


Also, if you intend to charge the battery from your tow vehicle you will need a DC-DC converter. I am using a 9 amp isolated victron model. I see Renogy has a 20 amp charger which might be suitable. Set it to the same voltage as your Progressive Dynamics power supply. The battery will take care of itself.

[/QUOTE]

I also use the 9 amp Victron DC/DC converter to charge a Battle Born battery while driving. Something to consider if using a bigger one is: Can you even attain 20 amps from the vehicle using the stock wiring through the 7-pin connector to the converter in the trailer? It is typically a long run of small wire and may not have the ampacity to safely handle 20 amps. I can charge at 9 amps but not sure if I could go higher - I just don't know.

Also, the Victron isolated DC/DC converter charge voltage can be adjusted with a tiny screw. I set mine to 14.2 volts. I used a lead acid battery to charge and a clamp meter to check the amperage.
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Old 06-03-2019, 01:25 AM   #12
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There's also some risk to the car's alternator, although at 20A it should still be fine. They're not really intended to run at a high enough output long enough to do things like charge a 200Ah+ battery bank, so overheating is possible. More of an issue in marine applications where large battery banks are common and directly connected to the alternator via large-diameter wiring, but worth keeping in mind if you start going nuts with wire sizes and DC-DC converters to maximize charge from the tow vehicle.
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Old 06-03-2019, 01:46 AM   #13
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Looks like the official minimum gauge on the charging wires on the 7-blade connector is 12AWG (or 10AWG for "heavy duty vehicles"), but I vaguely recall having to call around to find a shop that would use 10AWG instead of 14AWG to turn my 4-pin connector into a 7-blade. 14AWG is only good to about 10 amps, but 10AWG is good for 30A or so depending on distance (assuming 10% voltage drop is OK rather than the typical 3% thanks to the DC-DC converter)

You could go larger than 10AWG, but I'm not sure what the connector itself would handle above that. SAE wants $81 to find out what (if anything) the J560 standard says about it.

So, fine at 10A. Might be OK at 30A if the wiring's right. Above that, you're probably looking at some sort of custom separate power/ground connection for charging.
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Old 06-03-2019, 10:37 AM   #14
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14 AWG in a cable is good for 15 amps. The 9 amp DC-DC converter will draw more than 9 amps on the vehicle side due to conversion inefficiencies and voltage boost. I would estimate a 11 amp draw on the vehicle with a 9 amp converter. Also, if you mount the converter near the battery you don't have to be concerned with the voltage drop in the wires because the converter will compensate for it.
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