Thread: Bought a 100Ah Lithium for $399

At 14.37 V, the charger is limiting current to hold at that voltage.

Ahh, thank you. I hadn't thought of that. It's on float now and the battery terminal voltage is 13.65V - the spec sheet says 13.6V float.

Hi Ron and hate to ask the obvious, but are the lithiums already fully charged or it a decent discharged state.

Just like Lead Acid batteries, once a lithium battery is fully charged, regardless of the voltage being applied by the solar regulator, the battery governs how much current it will draw.

The batteries need to be discharged down to at least 75% SoC or they may not draw the full current available from the solar regulator.

The reason I ask is that you stated you were seeing full voltage but lower than expected current.

Lithium batteries in a lower that fully charged state, will draw full CURRENT but cause the solar regulator ( any brand ) to run at a lower voltage.

This is not what you are seeing.

Thanks Tim.

When I got the battery I'm sure I saw something about it not being fully charged but I can't find it now.

The battery has been on the solar charger for a few days and seems to have topped out with an input of 46Ah.

That would seem to indicate it was at roughly 50% capacity when I brought it home.

The discharge curve is pretty flat, is it accurate enough to determine SOC like one does with a lead-acid battery? This curve is from their spec sheet.

Lithium Discharge Curve.JPG

Compared with your lead-acid SOC chart:

dt90-soc-tablem_med_hr-3-300x209.jpeg

I didn't know if I could/should use my Traxide SC80 with this set up.

As a side note, when I bought the lithium, the full retail was $899. I looked at the Jaycar website a few minutes ago to download the spec sheet. New price is now $949.

Hi again Ron and the CHARGE graph is for a DC/DC device or 240vac Battery Charger or a Solar Regulator.

These three charging devices are known as CONSTANT CURRENT chargers.

Alternators, because of the very high current output, are Constant VOLTAGE charging devices.

If you charge directly from the alternator, via your SC80, you will have a totally different charge curve.

Looks like you did well on the price!

Also note, that charge graph does tell the whole story.

Where the graph peaks at the end, your lithium battery may still only be about 85 to 95% charged and the last section of the charge ( the Absorption stage ) could easily take many hours to get your LITHIUM battery to 100%.

Originally Posted by p38arover

Ahh, thank you. I hadn't thought of that. It's on float now and the battery terminal voltage is 13.65V - the spec sheet says 13.6V float.

The charger should not drop to a float voltage with a lithium battery. It should hold at 14.4. A lower float voltage is for lead acid battery charging.

Originally Posted by Red90

The charger should not drop to a float voltage with a lithium battery. It should hold at 14.4. A lower float voltage is for lead acid battery charging.

Yes, the battery label shows the float voltage at 14.6V.

The DC/DC charger Charging Voltage Limits section shows 14.5V charging and 13.6V float.

I'm confused.

The correct way to charge a Lithium battery is to bulk charge to the Absorption stage and then once the lithium battery is fully charged, turn the charging totally OFF.

This applies to good quality 240VAC battery chargers and Solar regulators.

But with DC/DC devices, it is pretty well irrelevant because, unlike 240VAC battery chargers and to a lesser extent,Solar regulators, where they can be charging for many hours, DC/DC device charging time is limited to the actual drive time of the vehicle.

Having a DC/DC device go into FLOAT mode is not going to harm a lithium battery while driving, but when a DC/DC device is being used as a Solar regulator, not so sure I would be all that happy, but it still shouldn’t harm a lithium battery, just not best practice for lithium battery charging.