Charging 12v Lithium Batteries.

[PPrep]

This is a heads - up about the risk of damaging some cheap charge controllers when charging lithium batteries.

I bought a couple of 12v LiFePO batteries some time ago. At first was mystified in that there was no trickle effect as in fully charged lead acid batteries, but the charge current completely cut off when the lithium batteries were full. I was using a clunky but highly reliable old home-made analogue charger.

In 12 or 24 volt solar charges systems, I've discovered that cheap charge controllers may fail if the battery is not connected before connecting the solar panel (not the hard way, fortunately!). In any case it's better to lay the solar panel face on the ground or away from the sun before connecting it to avoid surges, if possible. This might not apply to solar generators, as they're integrated. All the same, it may be worth checking.

12 volt lithium batteries have a battery management system (BMS) inside to apply balancing to the four cells, and over and under voltage and low temperature protection. When the battery is charged, the BMS will as a rule effectively disconnect the battery from the solar panel, so endangering some charge controllers. High - end controllers such as Victron are largely immune to this problem. Although there's a lot of debate about this, the only safe way to be sure is to carefully check the manual for the particular make and model of charge controller that you use.

Lithium batteries will outlast lead - acid batteries as a rule. Lithium batteries can safely be discharged to 85%; maximum safe discharge is about 65% for lead acid. Not exceeding these limits will help maximise the life of the battery. Lead - acid batteries like to be kept topped up; lithiums are best stored at about 60 to 70% full charge.

It seems possible to charge a lithium battery from solar panels without a charge controller. This is not recommended as if the BMS malfunctions, the battery could overcharge. Note that lithium batteries are prone to catch fire if abused.

Lithium batteries are likely to be as vulnerable to a coronal mass ejection or electromatic pulse as general electronics because of the BMS inside the case. These are normally sealed in.

[Yorkshire Andy]

Cheap solar charger units are a fire waiting to happen by all accounts should see the heat sink on the back of my renology mppt 20 controller it's huge...


Lithium iron phosphate batteries are safer than lipo as in the thermal run away isn't as violent but in the event of them overcharging due to a fault off gassing they released far more hydrogen than other technologies as with older lead acid charging in a well ventilated place is never a bad idea

Match the charger to the battery in terms of max charge current and voltage and charge pattern lithium generally don't like lead acid chargers

All power storage needs to be treated with respect.. the boss dropped a Makita lipo drill battery off some ladders .. he wanted it putting out ... I just stepped back it was outside on concrete no risk to anything just let it burn out then once cool sweep it up

[PPrep]

The heatsinks and dump loads on my home - made analogue controllers are very large. Although outdated and not as efficient as MPPT charge controllers, they're safe and the old 1980's bipolar technology is more resistant to lightning or other EMP than most modern kit . (This brings to mind the interesting but complex subject of surge protection using varistors and TVS diodes. These are relatively cheap and easy to use for smaller 12v systems and 240v mains spike supression). Analogue charge controllers cannot harm lithium batteries and are fully tolerant of the BMS switching off the battery when fully charged, or for any other reason.

I agree that there are some dangerous battery chargers on the market!

I posted twice in error, as I didn't get the "Post has been successfully submitted.....need to be read by .....moderator" etc, message. This was, I think, because this is my 11th post (and some restrictions are lifted), and thought I hadn't submitted the post on the first attempt.