[electricboats] Battery Recommendations

Thanks for comments on ePropulsion and GrenerPower batteries. The Spirit Plus battery is only specified as Lithium Ion Polymer. The BMS may be working well in that it senses a problem cell, but could it also be that it failed to provide the cell balancing function which would produce that problem cell? There is no communication between users and ePropulsion; the dealers are our only option and finding a responsive one is elusive. I joined the ePropulsion group on Facebook and did see posts from others experiencing sudden shutdowns, but the group is moderated by ePropulsion sales and marketing, so technical help is scarce. The only dealer I have found that would address the shut-down issue claims there can be three possibilities - corrosion at connections, failed BMS, or cell failure. Corrosion is not likely, but narrowing down between BMS and cell(s) requires shipping and testing and confirmation videos, etc., - not something I want to do – nor pay to have done. An excerpt from the manual regarding storage and self-discharge:

 

Before long time storage, ensure the battery charge level is 60% around, store the battery in 15°C ~ 25°C (59°F ~ 77°F) ambient temperature. 

If the battery level is larger than 60% for more than ten days without activity, the battery itself will discharge with a small current around 100mA until it reaches the 60% battery level.

• Battery will actively discharge to 75% after 20 days without charging or discharging.

• If battery level is low for a long time, it will enter sleep mode. Charge to wake it up.

• During long time storage, activate the battery every 3 months by a charge condition and keep the battery charge level at 60% around. This activation is very important and it can help to keep the battery in good condition.

• After long time storage, fully charge the battery before use.

 

From my self-discharge data, there is evidence that the mentioned 100mA load is applied which increases the self-discharge rate for a short period. It does not quite reach the 60% level before continuing at a lower rate. It's the sudden drop I don't like. I plan to test with bollard pull soon to determine whether this occurs under load and, if so, whether shutdowns repeatedly occur at the same charge level.

 

 

I previously used the term sudden loss of charge (SLoC), but from subsequent charging, it appears that the battery does not suddenly lose 40% of its charge. It just becomes unavailable due to shutting down. See charge plot:

 

Note that I have the Spirit 1.0 Evo Remote which has a permanently fixed remote throttle and display panel. When the battery is removed from the boat, there is no integral charge level indication. I purchased the ePropulsion Battery Activator that displays charge level. I now have a grid charger and solar controller for nominal 48V LiFePO4, so might try the GrenerPower battery again and hope for one at normal shipping charge condition.