The greatest majority of problems faced when using a Daly BMS come down to two main issues, activation being the greatest of issues. There are multiple ways to activate the BMS, but what may seem obvious at first is not necessarily so simple.
Before trying to activate the SmartBMS, we recommend double checking the following items:
- Check the cell voltages with a Digital Multimeter. They should be between 2.8v and 3.65v for LiFePO4. If any cell is out of range, use an appropriate charger or resistor to bring the cells within range. We highly recommend top-balancing your cells to 3.6v prior to building your pack & hooking up your BMS.
- Check the voltages between adjacent pins on the balance harness. They should match the cell voltages. This step may seem pointless if you are certain that all of the wires are properly connected, but if you have a break or poor connection in any of the balance leads, you will find it when preforming this test.
- Ensure the “NTC” probe is plugged in even if you do not desire low-temp protection. If this probe is missing or damaged, then the BMS will read a temperature of -40°C and prevent activation.
Note: This method will not work with some “smart” battery chargers that must see battery voltage on their output terminals.
When the BMS arrives to you, before you hook it up to your system, it seem obvious that the BMS is de-activated because it is not connected to any batteries. The balance header is seeing 0 volts on each cell, which is far below the low voltage disconnect. Why are we stating the obvious you may be asking?
In this state, the BMS must not only see a cell voltage on the balance header that is within range, but the internal shunt in the BMS must see charge current flowing into the batteries before it will fully activate. When the BMS is in a low-voltage disconnect, the BMS will ONLY allow charge current to flow into the battery, and will not allow current to flow out of the battery, which is why this will not work for “smart” battery chargers which wait to be connected up to a battery before they enable charge current…for safety reasons. I’m sure by this point you can understand why this makes activation of the BMS complicated and/or confusing.
Tl; dr: If your charger is not too smart for its own good, turning it on will pass power into the batteries activating the BMS on the way.
As mentioned in Mothod #3, some “smart” battery chargers and Inverter/chargers are unable to turn on if they do not have battery voltage present on their output terminals. A workaround, and why this section is noted as “Advance Users Only” is to briefly bypass the BMS. This is a 4 step process:
- Turn on the charger, it will likely flash an error saying “no battery” or something similar.
- Using a piece of wire, bypass/jumper from the blue B- terminal to the black P- terminal of the BMS, which will allow the charger to see voltage from the batteries.
- At this point the charger should have kicked in, which you can typically observe from fans running, or indicator lights saying “charging”
- Remove the jumper wire shortly after the charger has started. The charge current will now re-divert through the BMS, activating it. The system now is ready for use.
This process may need to be repeated if the BMS goes into a low-voltage disconnect state, because the only way to recover from a low-voltage disconnect state is to charge the batteries. We highly recommend using Method #1 instead as it is far safer and easier to repeat.