Updated: Dec 27, 2022
Most LiFePO4 RV batteries have a built in Battery Management System (BMS) that will shut the battery off if they discharge too far. This means the battery goes to zero volts across the (+) and (-) terminals. This protects the battery from the damage caused by an over-discharge. There are some Li batteries that don’t have a BMS, and you will quickly ruin them if you discharge them too far.
This creates a dilemma for many of the cheapo solar charge controllers that you find on the internet and on portable solar charging systems. They require a battery voltage in order for the charge controller to turn on. Since the Li battery voltage goes to zero when the BMS disconnects it, these cheapo charge controllers don’t see a voltage, and will not turn on, even in full sunshine! Your Li battery is essentially useless. that is, until you find a way to “wake up” your sleeping Li battery. This is actually a bit more complicated than it seems. Unlike Sleeping Beauty (or should I say Sleeping Battery), a kiss from a prince (or princess) won’t wake up a lithium battery, even if the battery is your one true love. Most modern battery chargers are “smart chargers” and won’t turn on the charging voltage until they see a battery voltage. Hence they won’t “wake up” a sleeping Li battery. In the good old days, battery chargers were “manual” chargers that always had a voltage output, but it is very hard to find one these days, this is the only one on Amazon that I could find. We have industrial grade Li chargers that are completely compatible with all LiFePO4 RV batteries, and will wake them up.
There are a couple of tricks to waking up a sleeping Li battery (none involve kissing):
1) Attach a manual battery charger, or Li compatible charger to the battery.
2) Run jumper cables from your car battery to the Li battery. That will wake it up, but not really charge it very well. But at least your cheapo solar controller will turn on and start to charge.
3) Connect your solar panel directly to the Li Battery, bypassing the cheapo charge controller. Beware that after the Li battery has 10-15 minutes of charge, you need to add the cheapo charge controller back in, or the direct connected solar panel will over charge your battery, possibly damaging it.
Many of the portable solar panels on the market don’t have the correct cabling to allow you to bypass the cheapo charge controller. Most of our portable panels are designed to make this easy to do. We deliberately developed a cable system that allows you to direct connect the solar panel to a battery, or a solar generator, or an RV with a “solar ready” port.
So how do you know if your cheapo charge controller will wake up your LiFePO4 battery? The first thing to look at is the minimum battery voltage it requires to turn on. That is often 9V or so. If it requires any voltage to turn on, it won’t wake up a sleeping LiFePO4 battery. If it is a 12/24V compatible controller, it requires a battery voltage well above zero for it to turn on. So it won’t wake up a LiFePO4 battery either. If it doesn’t have lithium settings, it probably won’t wake up a lithium battery.
Here are some examples of charge controllers that won’t wake up a LiFePO4 battery
1) Zamp Solar ZS7A Solar Charge Controller, and most of the Zamp controllers that are not Li specific
2) most of the older Go Power charge controllers, although some of the new ones do
3) most of the older Renogy charge controller, although some of the new ones do
4) almost any cheapo charge controller you buy on Amazon won’t wake up a Li battery
Here are some examples of charge controller that will wake up a Li battery:
1) Any of the Victron Blue Solar and Smart Solar Charge controllers
2) The more expensive Renogy’s that are Li compatible
3) The Rich Solar MPPT charge controllers (but not the PWM charge controllers)
At Leisure Solar, we often chat with people and help them figure out how to connect and use their portable panels, solar generators and other electrical stuff. We design and build custom cable systems that can make almost any solar system work. Give us a call to discuss your needs. But don’t ask us to kiss your battery, we are nice but not princes.