Balancing capability of Neptune15 Smart BMS

[GaryTheGolfer]

Hi,

I ended up here directed from Speedict.com's website (?)

My questions relate to using a Neptune 15 to balance an old 10s/2p 36v 360W ebike battery.

Theoretically ebike battery BMSs should balance/rebalance ebike batteries but in practice it seems they only keep a fairly balanced battery in balance. I have a battery that has a variation of about 0.7v across the cells (eg 3.4v to 4.1v). The current cheap BMS can't cope with (rebalance) the cells. (no surprise). The cells have been stored badly for months (even before I got them)

I am considering a 10s balance charger or a Neptune15 Smart BMS. The balance charger may be able to properly balance the cells (assuming they can be saved). The Smart BMA is a much more elegant solution. The Balance Charger is much less convenient. Both solutions would cost about the same. The battery will often have to be left for many months at a time (hopefully, at storage voltage). So rebalancing may be a frequent requirement.

I cannot see from the Smart BMS makers website what range of imbalance the Neptune can deal with. Simply knowing, via bluetooth/app, what the cells voltages are is of no help if that BMS can't fix a badly out of balance battery.

Does anyone know what real range of imbalance the Neptune can correct?
Does anyone know of any other brand/model of Smart BMS CAN correct such a wide range of cell voltages?

Thanks in Advance for any help/suggestions

 

[john61ct]

The most important spec is Balance Current.

In this case 1A would be enough, but most devices it's far less.

I've seen up to 6A.

An important qualification, is it passive, where the actual current rises and falls with the degree of "delta" difference between cells?

Or active, which maintains the spec current as the gaps close, much faster.

___
Next is, at what voltages will balancing start and stop.

Ideally any, so bottom (LVC) or even middle (storage) balancing is supported, not just top while charging.

Certainly should be user adjustable if not.

As with the target delta, for stopping balancing.

Reporting voltages is a nice feature, via comms even BT to phone app.

And of course voltage accuracy and build quality / longevity is important.

 

[amberwolf]

here's a different question, rather than what would keep them balanced, that might be useful:


what do you need the cells to do for you?

if they are that badly unbalanced, they are likely of greatly varying condition (or type), and badly mismatched cells (groups) will not operate very well, or very long at a time; each one will have different amounts of voltage sag, and internal heat generation, etc.

so unless you don't need them to supply very much current, relative to their original specifications, and/or not run very long before recharge/rebalance, relative to their original specifications, their condition may make them unusable for you.


if you need them to run the ebike itself (or anything else requiring more than minimal output for minimal time), it's probably a better use of money to replace the battery itself than to purchase things to keep it going.

 

[flat tire]

Under most foreseeable scenarios that would cause such an imbalance your battery is in trouble and should be replaced.