Many thanks to the community for comments on my first post.
We have started building our 52’ ocean cat and looking to finalize electrics. Have taken on board previous comments and researched options. Our goal is to achieve a fully electric sailing boat with minimal weight.
We are keen to decentralize batteries into two banks, one each hull, adjacent the highest loads - electric motors. This design reduces overall weight by reducing heavy cabling, improves weight distribution & provides redundancy in event one bank fails.
Was previously concerned about managing and balancing individual banks. I believe the solution is to link the banks with a common charge cable. I understand that electricity, like water, will find its way to the lowest point (voltage) and flow until all voltages on system are balanced. With some extra switches, this charge “tie” cable could also be used to power up equipment on a failed bank from the working bank.
Main parameters are listed below. We have sized banks and gen set to provide short term (say 30mins) power for max. elec propulsion after which we are happy with 50% continuous via 16kw gen set.
Main parameters & equipment:
- Propulsion and galley services all electric.
- Motors 2 x 15kw (DC 48V), Input Voltage range: 25.2v – 60v
- 2 x 48V 10kwh battery banks - (HE Lithium 24V 200A x 2S) one in each hull adjacent elec motors. HE batteries preferred as highest energy/kg density. Although note voltage discharge profile comment below.
- 2 x Lynx Ion 400A BMS,
- House loads DC - 24V (peak 2.3kw) – Orion-Tr 48/24-16A (380W) x 6P. Input Voltage range: 40v – 70v
- House Loads AC 240V (peak 4.8kw) - Phoenix Inverter 48/5000w. Input Voltage range: 38v – 66v
- Gen set 48V DC 16kw (continuous, water cooled alternator) – located in port hull.
Have attached a Schematic showing concept.
Have attached a Victron HE Lithium Battery – 24V 200A discharge profile that I stumbled on.
My questions for the community:
- Will the charge cable from charge bus linking Charge inputs of each bank’s BMS also balance voltages between banks as I hope?
- “Allow to charge” outputs from Ion BMS’s can be used to manage charge input circuits to charge BUS ie one to solar & one to gen set. 2 BMS signals to one solar input should work if balance principle in 1. applies.
- “”Allow to discharge” outputs from BMS’s can be used to manage loads. Not yet sure of configuration but guess a NO contactor in load circuits.
- Elec motors have regen function which can be activated while sailing. This comes back to batteries via motor load cable. Not sure how BMS handles this – maybe a manual monitor situation when regen operating or is BMS smart enough to read this?
- HE Lithium discharge profile. I understood Lithium battery voltages stay relatively constant during discharge except at the tail ends. The attached graph which purports to be a Victron HE 24V discharge profile shows a fall in voltage proportional to SOC%. Our planned equipment appears to be fairly tolerant on DC Input side so maybe a non-issue?
- Orion-Tr 48/24-16A (380W). This appears to be the largest 48v DC:24v DC converter available from Victron range and can be a paralleled up. It is isolated which is good for voltage spikes in event of primary/secondary break down but not as efficient (around 89%) cp to non-isolated at 93%.
- Inverter function of Phoenix & Multiplus are equivalent, weight same and cost difference marginal. While not planning to use 240V grid hook up maybe worth the investment to use a Multiplus & have this option in future?
- Assume DVCC via CCGX / Venus GX will be able to monitor and manage all this great equipment?
Would be truly grateful for any comments, suggestions & feedback.