Re: [electricboats] Maximum input voltage for outboard?

LiFePo "12v" batteries typically reach 100% capacity with about 14.4v (e.g. this one:  https://batteryevo.com/battery-evo-12v-28ah-lifepo4-battery-ef1230-360wh-solar-rv-golf-cart/ )

 

And so, 4 of these in series ~ 57.6v.  Ones with built-in BMS often allow charging voltage to be as high as 16v (internally bypassing or otherwise limiting the charge voltage on the cells).  So, it seems normal to see about 58v in your case (or 3.6vpc) and would be close to 100%SOC.

 

If instead you charged to just 3vpc (for 48v total), you probably only get to 2-3%SOC: https://www.powerstream.com/lithium-phosphate-charge-voltage.htm

 

Now, if you need to limit to 55v, that would be 13.75v per battery or about 3.44vpc.  This still should be about 99%SOC, so you should be good.

 

I recommend you reduce the CHARGE VOLTAGE from your charger if possible.

 

-Myles

 

 

From: electricboats@groups.io [mailto:electricboats@groups.io] On Behalf Of James Jones
Sent: Tuesday, September 13, 2022 9:55 AM
To: electricboats@groups.io
Subject: [electricboats] Maximum input voltage for outboard?

 

Hi all,
I've just completed building an electric-powered boat, and upon wiring up the batteries found that the voltage at the end of the line (electric outboard power plug) is higher than expected.
My battery bank is four (4) 24v / 75 Ah lithium ion (LiFePO) batteries, wired with two pairs of batts each wired in parallel, and then series connecting the pairs, which should produce a nominal 48 volts output. The meter however reads 58.3 volts, which is higher than the combined "fully charged" voltage "should"(?) be. Since my outboard (Karvin 6800) has a maximum input voltage of 55 volts, this creates a puzzle. Am I missing something? Do I need to add a component to reduce the output voltage of the batteries? Etc...

Any advice much appreciated,
Jim