Chassis voltage never hits 14.4

[mburns884]

I have a lithium battery bank I would dearly love to charge with the alternator. I do have a BIM to support Lithium (precision circuits 225)

Yet when driving down the road (even in multi day trips half way across the country), the chassis voltage never exceeds 14.3. The specs on the BIM say it will not change the house batteries until chassis voltage reaches 14.4. Since I never reach 14.4, the BIM never makes the connection.

If I push the switch to manually join the house and chassis batteries everything works fine and I can see the house batteries begin to change just fine. But as soon as I take my finger off, the BIM ready the chassis at 14.3 or less, and charging stops.

My RV is a 2020 Hurricane - 29M.

Could this be the chassis battery showing age?

[DavidEM]

I have always wondered why the Li-BIM 225 waits until it sees 14.4 V on the chassis side before connecting. Many OEM fixed voltage alternators are set closer to 14 volts and it sounds like yours is one of them. So it will never connect as you have noted.

How big is your Li battery bank. If it is 200 amp hours or less you really don't need the protection of the Li-BIM 225. You can replace it with the BIM-160 which is what you probably had originally. But then it will only charge to the alternator's voltage set point and that may be too low for best Li battery charging.

The other solution particularly if your battery bank is bigger than 200 Ah (and as a result will put too high of a load on the alternator) is to replace the Li-BIM 225 with a 30, 50 or similar sized DC to DC charger.

These have their own problems and will not allow the aux start switch to work. But they will charge your lithium batteries well. Vicron, Renogy and Redarc make them.

David

[mburns884]

Thanks David!

Battery bank - 520, watts, so the 160 is definitely not an option

I’ve thought about the DC to DC but I prefer the BIM for the reasons you listed.