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Old 04-03-2021, 12:54 PM   #1
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DC to DC for lithium battery

My tow is a 2013 Silverado 1500 and I recently replaced my dead trailer batteries with one 100W BattleBorn Lithium, which I am totally happy with.

However, now I am hearing that I may need to add a DC to DC charger/converter? in the trailer to protect my Silverado's alternator from burning up when on the road from excessive lithium charging. Is this right? Does my Silverado have an overcharge protection or must I simply pull its fuse going to the 7 pin?
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Old 04-03-2021, 02:13 PM   #2
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We have a Chevy Tahoe, which is built on the Silverado frame, and have heard the same thing.

I would speak with the your dealership’s Service Department Manager. They are very open to discussing all issues involving towing & electrical.

Speak with Battleborn. They can explain it to you. Also, since you bought their battery, they will probably sell you a DC-Dc at a discount. Also, if you belong to the Escapee tt club, they may give you a bigger discount.

I’m currently installing a solar system. I plan to research DC-DC Chargers prior to embarking on longer trips.
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Old 04-03-2021, 02:18 PM   #3
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Lithium’s ate a different breed and require different chargers. Do it wrong an you could ruin the battery or have some other problem (Fire).
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Old 04-03-2021, 03:05 PM   #4
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Fire?

No worries about fire. Lithium batteries (most) have a battery management system that ensures no over-charging, and no fires.
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Old 04-03-2021, 03:17 PM   #5
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The ones I have for tools, the management is in the charger. Just Sayin.
that is why he needs to get the information from the battery manufacture.
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Old 04-03-2021, 04:03 PM   #6
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For the BattleBorn I upgraded my WFCO 8955 with the Progressive Dynamics PD4655 LMBA Wildkat replacement converter main board. I switched to a Morningstar MPPT-15L solar controller.

I currently employ 200 watts of portable solar and will add another 190 watts on the roof. So far everything's kicking ass so no concerns until I hook up and start travelling again, and wonder if the tow alternator is gonna fry down the line.
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Old 04-03-2021, 05:15 PM   #7
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Simply go to the Battle Born site and find their charging voltages. They have a simple paragraph that tells ideal voltages, typical voltages and what is acceptable. You'll see they match up well with normal smart chargers in every way except the charger shutting off when charged. The float voltage of the Ram is fine for Battle Borns, the float voltage of a GM should be measured to find out what it is, and then compared to the chart.

All alternators have controllers on them that provide typically 14.2-14.5 volts to the vehicle battery. Rams go to a float charge when the battery is fully charged.

The Ram smart charging program in their charging systems matches the Battle Borns very well. Fords don't match as well. Don't know about GM. But either way, the Battle Born BMS protects the battery and shuts off charging when the battery is charged. After charging, Battle Borns can either sit at a float charge of about 13.2, or they can have charging current turned off completely.

You will not burn up your alternator. I think you mean you installed a 100 AH battery, not a 100W battery.

I really wish Victron would not have posted a misleading video on burning up an alternator. What they show is probably impossible in the real world of charging a trailer battery from a tow vehicle, but it has managed to scare a lot of people into thinking the sky is falling. The idea that a lithium battery has the ability to "suck" more power from an alternator than it can normally deliver is pretty ridiculous. Next they'll be telling us a swimming pool can suck more water out of a garden hose than a bucket can.

I put three 100 AH Battle Born lithiums in an Oliver about two years ago, with no DC-DC charger, and with Battle Born's blessing, and it has been working perfectly ever since.

Nothing wrong with a DC-DC charger. Probably the best thing it will do for you is disconnect the charging system from the battery when the lithium is charged, instead of relying on the battery BMS to do it. It will also prevent the truck battery from being discharged. I think this function is accomplished by not allowing any power through below a certain threshold of about 13.2 volts. When you start your truck, the voltage immediately goes to 14.5. This allows charging of the trailer battery too. The DC-DC charger does not know if the truck battery is charged or not, it only knows the threshold voltage is above 14, which it is as soon as the truck starts.

Alternators do not just run wild, they are precisely controlled at all times to charge batteries.
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Old 04-03-2021, 06:07 PM   #8
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Renogy DC-DC MPPT Controller

I have just completed the install on the Renogy DC-DC MPPT Controller. I ran 4GA welding wire to a bumper mounted Anderson 175 connector and aduplicate connector at the hitch on my Casita. The controller is inside near the battery bank, and seems to do what its intended and provides up to 25A at 12v and only allows this if the TV battery is fully charged. (13.2 v) works pretty good, and keeps my 4-105ah Lion lithium batteries charged . I would be afraid to try and charge my batteries with my TV alternator without a controller. Hank W Baltimore OH.

Quote:
Originally Posted by MyronL View Post
My tow is a 2013 Silverado 1500 and I recently replaced my dead trailer batteries with one 100W BattleBorn Lithium, which I am totally happy with.

However, now I am hearing that I may need to add a DC to DC charger/converter? in the trailer to protect my Silverado's alternator from burning up when on the road from excessive lithium charging. Is this right? Does my Silverado have an overcharge protection or must I simply pull its fuse going to the 7 pin?
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Old 04-03-2021, 07:33 PM   #9
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Quite right, Raspy - senior mistake - it is the 100Ah 12v LifeP04 deep Cycle battery. And as regards my tow alternator burning up because I have lithium? - It did sound like quite a stretch.
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Old 04-04-2021, 11:05 PM   #10
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The alternator burnout issue with LFP batteries is mostly for boats, where the alternator is in an enclosed space with the engine, the battery bank is fairly large, and there's a short large wire between them. For a travel trailer, the voltage drop through the long and relatively small connection wire is large enough to limit charging to around 10A, which is no problem for an alternator.
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Old 04-05-2021, 07:16 AM   #11
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While many lithium users do not add a DC to DC converter between the tow vehicle & trailer, there are a couple of reasons to consider one.

To fully charge a lithium battery, a charge voltage of 14.4V - 14.6V is necessary. The combination of modern vehicles quickly lowering alternator voltage as soon as possible to improve mileage and the undersized charge wiring in both the tow vehicle & many trailers end up with well under 14.4V at the trailer battery. A DC to DC converter can be set for what ever voltage you desire. Located close to the trailer battery, it will provide full charging voltage.

While unlikely with a trailer (as Elliott notes), a lithium battery has a very low internal resistance, drawing what ever the alternator can produce. This could lead to overheating, particularly in motorhomes & vans where the wiring distances are short. The DC to DC converter limits charging current to its rating.

The trailer's lithium battery is close to 14V fully charged. If the tow vehicle battery is less than that, a directly wired charge line will draw from the lithium trailer battery & attempt to charge the tow vehicle battery. A DC to DC converter is a one way device and will prevent this. Not a major problem, but something to consider.

The one way feature of the DC to DC converter brings up another consideration. If your break away switch or power tongue jack is powered by the charge line, and the DC to DC converter is between that connection & the trailer battery, you will no longer have a connection to the trailer battery. You may need to add separate wiring to support those devices.
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Old 04-10-2021, 06:40 PM   #12
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DC to DC converter

I found this helpful. I have just added the DC to DC converter (30amp) to my F150 to my deep cycle battery back on my camper while I drive. This link is an even better option as it has BOTH the DC to DC convert and an MPPT controller built in. This link explains the system and is very informative.





Love battleborn, one day.....
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Old 04-15-2021, 11:34 AM   #13
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Pardon my lack of knowledge on this but I thought that the issue with charging a LiFePo4 battery in your RV straight off a vehicle's electrical system wasn’t that the RV battery can draw too much current, but rather that the vehicles alternator is made to support a continuous load. The issue being that when the Lithium battery reaches a full charge the BMS cuts out charging instantly and the alternator voltage regulator can't shut off completely, which will damage it.



After watching a few dozen Will Prowse videos along with a few dozen others, the info is all jumbled...
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Old 04-15-2021, 02:34 PM   #14
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Actually the lithium batteries that are usually used (4 X 3.2 volt cells) charge at a constant voltage of about 14.6 volts and while the charging does cut off at the determined high voltage point it does taper as it gets closer to the cut off voltage limit.
The alternator really is capable of regulating quite well as it als0 has a battery as a buffer so I don't this the sudden shut off would matter any more than turning off your head lights.
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Old Yesterday, 07:33 PM   #15
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JD,

I agree.

The tow vehicle alternator has a regulator that is always monitoring the tow battery and is adjusting the charge accordingly. The trailer battery is connected to the tow battery, not directly to the alternator. Alternators do not just run away, or charge in an uncontrolled manner. They are precisely controlled, all the time.

If the lithium BMS cuts off the charging to the house battery, it is the same as the headlights being turned off. Just a change in the load. There is no surge that will damage the alternator.
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Old Today, 05:10 PM   #16
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Quote:
Originally Posted by MyronL View Post
My tow is a 2013 Silverado 1500 and I recently replaced my dead trailer batteries with one 100W BattleBorn Lithium, which I am totally happy with.

However, now I am hearing that I may need to add a DC to DC charger/converter? in the trailer to protect my Silverado's alternator from burning up when on the road from excessive lithium charging. Is this right? Does my Silverado have an overcharge protection or must I simply pull its fuse going to the 7 pin?

The concerns identified in the Victron video are valid given their setup, however, your setup is completely different. They are charging at 65 amps, while you are charging at 10 amps or less through the charging wire on your 7 pin connector.

As pointed out in the Victron video, a LifePO4 battery can draw far more power than a lead acid battery during charging. In the case of the Battleborn 100 ah battery, the BMS allows up to a 50 amp charge rate. Some other LifePO4 battery brands allow a much higher charge rate, e.g., the Lion Energy UT 1300 105 ah battery allows a 100 amp charge rate. If you had three Battleborn 100 ah batteries AND sufficient gauge charging wire, you could overwhelm the alternator. In that case a battery to battery charger might make sense to use.
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