Sunday, January 29, 2023


Will a ‘trickle charge’ ruin lithium batteries?

Dear Dave,
I replaced my lead acid batteries with two Ampere Time 200-amp-hour lithium batteries. I replaced the converter with a Progressive Dynamics converter, and 14.6-volt output that goes down to 13.6 when charged. The manufacturer says not to trickle charge them. Any advice would be great. —Rodney, 2022 Twilight Signature 3100

Dear Rodney,
The Progressive Dynamics converter is a good move as it will provide the 14.6 volts that the lithium batteries want. When the batteries are fully charged, the converter should go down to 13.6 volts, which is the level that a fully charged battery will not accept a charge.

Trickle charge vs. float charge

There is no “trickle charge” that I am aware of, but rather a float charge that is a specific voltage applied. The battery is free to accept current or not, depending on the state of charge. That is why you want to pair a converter that is designed for lithium batteries with your new batteries.

What manufacturer stated “not to trickle charge”? Was it the battery company, Progressive Dynamics, or the RV company? What brand of batteries did you put in?

This is the Progressive Dynamics model we installed for the 2015 Thor Challenger that we put in the same battery array as you described. We used the Expion360 brand, as I felt they had the utmost in quality and components. There are a ton of cheap lithium batteries flooding the market these days.

Another consideration is the distance your converter is from the batteries and “line lose” or voltage drop you might experience. Ours was installed under the bed and was about 25’, which meant our 8-gauge cable was insufficient and we would not get a full 14.6 volts.

I would suggest you contact Progressive Dynamics and talk with their technician, as he is the most knowledgeable when it comes to the batteries and distance.

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Jim Rodan
1 month ago

The Progressive Dynamics converter goes down one more step to storage mode. For example:
BOOST MODE: If the voltage drops below a preset level the output voltage is increased to approximately 14.4 VDC (28.8 VDC for 24 volt models) to rapidly recharge the battery.
NORMAL MODE: Output voltage set at approximately 13.6 VDC (27.2 VDC for 24 volt models).
STORAGE MODE: If there is no significant battery usage for 30 hours the output voltage reduces to 13.2 VDC (26.4 VDC for 24 volt models) for minimal water usage. In storage mode, the output voltage increases to 14.4 VDC (28.8 DC for 24 volt models) for approximately 15 minutes every 21 hours to help prevent sulfation of the battery plates.

Last edited 1 month ago by Jim Rodan
Left Coast Geek
1 month ago

re voltage drop over long run cables… there’s no voltage drop when the charge current drops to low values once the batteries are fully charged. at 0 amps, there’s 0 voltage drop on any amount of wiring.

1 month ago

I think Dave referred to the 14.6v pretty clearly…

Left Coast Geek
1 month ago
Reply to  bill

he wrote, “Another consideration is the distance your converter is from the batteries and “line lose” or voltage drop you might experience. Ours was installed under the bed and was about 25’, which meant our 8-gauge cable was insufficient and we would not get a full 14.6 volts.”

Thats true at 50 amps or whatever, but as the battery approaches fully charged, the current drops, and when the current is zero, the voltage at the battery will be the full 14.6V of the charging source. My 412 AH of Lithium is maybe 3 feet of heavy gauge wire from the PD4655, it bulk charges at about 50 amps around 13.5V (at the battery) until its almost fully charged, then the current drops quickly, and the voltage levels off at 14.6V

1 month ago

Morning Dave, wondering why you suggested for Rodney to call Progressive Dynamics about batteries & distance. He didn’t ask about that! Actually you never answered his question about to “not to trickle charge them”

Rodney Lacy
1 month ago
Reply to  Snoopy

Actually he did answer my question. He said 13.6 volts continually won’t hurt the batteries. The converter goes to 13.6 when charged and that is what lithium batteries want. 13.6 is float, not trickle.

1 month ago
Reply to  Rodney Lacy

Ok your right, I went back re-read his reply!
PS, very nice up grade!

1 month ago
Reply to  Snoopy

Also, Progressive Dynamics techs are super knowledgeable and the most reliable source of info on their product’s usage.

Bob M
1 month ago

He did say he put in Ampere Time batteries.

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