This is a contentious subject, and to be fair tons of conflicting advice on the web.
Simple answer: to get the most out of your battery it should be charged correctly.
There is a “suspicion” that some battery sellers state that no change to charging equipment is necessary just to get the sale. There is an equal suspicion that sellers of chargers argue that a lead-acid charger damages a LifePO4 battery so they can sell you a charger.
We “prefer" that you should consider changing your chargers. If not then some chance of damage to your battery, and an almost certainty that you will get less out of your battery. It’s a bit like buying a 5-bed house and never using the 5th bedroom because you don’t have the key. A LifePO4 charger should charge faster and put in more SOC, and you can still configure things to make the battery last a long time (many cycles).
The waffle:
Lithium batteries prefer/require a Constant current/Constant voltage (CC/CV) charge type with simple Bulk, Absorption, Float stages. Many lead-acid chargers have desulphation and equalisation stages built-in, which will pulse high voltages of 15.3-15.8V into the battery. This is not suitable for LiFePO4 batteries. The thinking is that it can heavily reduce the life of the cells due to regular over-voltage charging or cause irreversible damage to the battery. So: desulphation and equalisation probably should be avoided. Firstly because it could damage the battery and secondly because it could cause the BMS to cut charging again and again during the process.
Another concern is that if you have a charger capable of above 14.6v it makes the BMS the first, last and only line of defence. The Daly’s we use are brilliant and so far we’ve only ever had one faulty unit (but we think the person connected it the wrong way). But still … good practice to have at least two lines of defence.
A lead-acid charger may never get your battery fully charged. That in itself may be a good thing … making your battery last longer. But practically a few customers have found that they don’t get enough into their LifePO4 battery to justify the investment. One customer bought five of our batteries and was dissatisfied until he changed his charger - then he was happy. He is a heavy user though and needed as much capacity as possible.
The charge profiles have different "return to boost" behaviour. One of the most frustrating problems with using a lead-acid charger to charge a LiFePO4 battery is the pre-set voltage settings in the charge algorithm for re-start the bulk charge stage. As a lead-acid battery is full at 12.7-12.8V, almost all lead-acid chargers won't trigger bulk charging to re-start until it drops below around 12.5-12.7V as it doesn't need to recharge until it drops in voltage a small amount from full. By using this charger to charge a LiFePO4 battery, it won't re-start bulk charging until the LiFePO4 battery has dropped to around 20-25% state of charge at that same voltage as the lead-acid battery. You have to use almost all of the LiFePO4 batteries capacity before a lead-acid charger will start charging again. A LiFePO4 specific charger will trigger the bulk stage to start re-charging at typically 13.1-13.2V ensuring it starts charging again when it is still at high states of charge, not very low states of charge when it is going to be too late.
