BMS16C - does it really balance cells?

You are going through a "Sweat equity" DIY Enginer kit........for cheap.

 

Just to be clear, the BMS16C does NOT do any balancing except during charging, and only when the highest cells exceed a certain threshold, usually 3.8V. The balancing method is current-bypass, but only a small amount can flow through the sense wires. If a cell is more than a few amp-hours undercharged with respect to the rest of the pack, it could take numerous cycles before that lowest cell converges to fully charged. JeffreyDV's data from last month shows a situation where a few hours of manual balancing would resolved the issue. The BMS16C does an excellent job at preventing overcharge and fatal discharge.

Installers and DIYers alike should take the time to manually balance the cells at the time of installation.

 

A charge balancing system it is essential and expensive. Mine works very well because it actively balances all the time. But it is expensive It runs about 50 dollars per battery.

The hook up formula Is "N - 1" Where in n is the number Of batteries The amount of charge it can transfer is limited so icant take a few days if the batteries are way. Out of balance.

Right now on my Zenn, I just exchanged Two of my 6 Lead acid batteries. So i am currently working matching the new ones with the 4 old ones.

It is a bit of a hassle. What i am currently doing It is discharging them to approximately 80 percent then recharging them 4 30 minutes. Unplugging to let them 4 30 minutes so they can balance.

 

A charge balancing system it is essential and expensive. Mine works very well because it actively balances all the time. But it is expensive It runs about 50 dollars per battery.

The hook up formula Is "N - 1" Where in n is the number Of batteries The amount of charge it can transfer is limited so icant take a few days if the batteries are way. Out of balance.

Right now on my Zenn, I just exchanged Two of my 6 Lead acid batteries. So i am currently working matching the new ones with the 4 old ones.

It is a bit of a hassle. What i am currently doing It is discharging them to approximately 80 percent then recharging them 4 30 minutes. Unplugging to let them 4 30 minutes so they can balance.

 

For the Enginer system, active balancing is entirely unnecessary since it is an auxiliary battery pack. If you don't get maximum discharge because one cell was undercharged to start with, the only consequence is slightly less MPG. I would describe the BMS16C as a balance maintainer; it won't cure cells being significantly out of balance except over a large number of charging cycles, but once a string is balanced, it will stay that way for weeks, months or longer. And it does perform its essential duty perfectly, preventing over-discharge.

 

Hello Everyone,
I have taken lots of data from several systems using both the DB8s and the BMS16Cs. From my observations I have a pretty good idea of how the BMS16C operates.

Do not take information given in this thread or similar forums as gospel. I see some errors in the statements here.

However I do agree with Scott on this comment.

I am very pleased with my BSM16C and I have not needed to do any balancing charge for a long time now.

Thanks,
Dan

 

Hello Overlap,

First let me suggest that you go to the Enginer forum and request to be granted "USER" status. You will get information from more knowledgeable people that what you see in PriusChat.

I am ruining 2 systems and collecting data. I am confident that the system with the BMS16C does better than the system with no balancer. I clearly see this in the data. I suspect that you gave up on the BMS16C when it had only done 1/2 of the job it was working on.

Thanks,
Dan

 

Yes. The BMS protects the lowest cell against over-discharge, but if that lowest cell is several amp hours undercharged to begin with, having your pack switch off before reaching your destination means some miles at lower MPG. As opposed to an EV or RC aircraft, where early cutoff has much more serious consequences.