Drop-in Internal Balancing

[Ampster]

Have a few questions about these.

I have read a few times on this forum that you have to be careful not to exceed the shunt balances very small current handling usually around 1A max.
So how do manufacturers get away with allowing all kinds of charge currents at those high voltages of 14.4-14.6V? Mine allows up to 0.4C max constant charging rate. And when those voltages are reached the battery looks to be still taking in alot of current, alot more than 1A.
So if you hold the absorb voltage at these higher voltages for a while can it damage the balancers?

The shunts are not wired in series like the batteries. When they are on they reduce the current for the cell whose voltage is above the set point. Because when the shunt is on, it is actually in parallel with the cell. Therefore it will only bleed off the current that it was designed for. Review Ohms law for a more detailed explanation.

Finally I keep reading balancers kick in at 14.3-14.6V range, and that they are prone to killing the battery. If one stays low at just 13.8V then does that mean the balances can't kill the battery? I think not as these things do more than balance, like constantly monitor cell voltage. Agree or not?

A good Battery Managent System is not cheap. The ones I have used to balance lithium packs cost over $500. All those are programmable and the solid state relay circuits are designed to fail in the open position. That is not the case with less expensive BMSs. The BMSs that I use are programmable and I set the balancing voltage according to the chemistry that I am using.

Some people even suggest you don't need a BMS for a system as simple as 4 cells in series. In either event it is recommended that you initially balance the cells by placing them in parallel for a few days before assembling them into a pack. That way your pack should start out balanced. One of the benefits of using a BMS is the monitoring so I agree that that their usefulness is more than balancing. Remember you can be the BMS and all you need is a good multimeter to measure the voltage of each cell..

[Mike90250]

The Balancers with simple bleeder shunts are mostly designed to interact with the charger, when the 1st shunt activates, it also commands the charger to reduce amps. Most solar chargers don't have this ability and then batteries blow up or the BMS goes ape. That's why many factors have to be designed/engineered for a system to work well for years. Throwing a mishmash of parts together seldom works right, but so many folks nowadays never got a chance for hands-on learning and are finding out the hard way, it's not all book learning or test taking skills.

The other way balancers kill batteries, is the bleeder shunt fails, and discharges a cell. That's poor BMS design.

The more complex a system becomes, the more failure points are in it.

[Jman]

Have a few questions about these.

I have read a few times on this forum that you have to be careful not to exceed the shunt balances very small current handling usually around 1A max.
So how do manufacturers get away with allowing all kinds of charge currents at those high voltages of 14.4-14.6V? Mine allows up to 0.4C max constant charging rate. And when those voltages are reached the battery looks to be still taking in alot of current, alot more than 1A.
So if you hold the absorb voltage at these higher voltages for a while can it damage the balancers?


Finally I keep reading balancers kick in at 14.3-14.6V range, and that they are prone to killing the battery. If one stays low at just 13.8V then does that mean the balances can't kill the battery? I think not as these things do more than balance, like constantly monitor cell voltage. Agree or not?

thanks