Electric sailboat conversion - 2 steps forward 1 step back

[SV_Stray_Cats]

Which REC BMS? The Q? I looked at different BMS this morning and while the REC Q seem to have more clear/clean wiring than the Orion, I didn't find the price price, self consumption, info on how it controls relays or other details.

I don't have a CAN charger, but may connect the BMS to my Sevcon Gen4 motor controller. I'm not exactly sure what it would do - advisory request to reduce power? I know BMS theory is supposed to use controls and not alarms, but there could be times when I would decide to destroy the battery bank to save the boat. I haven't thought it all the way out, but I'd like low voltage disconnect, only when I'm not on the boat, and then maybe excepting the bilge pump....unless it's having a problem cycling the same water with a clog...

They only thing I need to figure out with them is I need two shunts instead of the 12v and 48v bank sharing one. Also noting that a boat always has common ground...

I think that would depend on if/how the two battery banks are connected. If they are completely separate except sharting the same definition of 0V/ground, I think you need two BMS and two shunts, two chargers, two everything. If the 12V bank is charged from a 48V charger powered by the 48V bank, I think a 48V shunt would capture all energy use, but not in realtime of its use. Well realtime from the 48V bank's perspective.

 

[luckybeanz]

Which REC BMS? The Q? I looked at different BMS this morning and while the REC Q seem to have more clear/clean wiring than the Orion, I didn't find the price price, self consumption, info on how it controls relays or other details.

I'll use a Q for the 48v Bank and an Active for the 12V. Here is a link to the Q manual which should provide the info you are looking for http://www.rec-bms.com/datasheet/UserManual_REC_Q.pdf the price will depend on what accessories you choose, such as their pre charge system and lcd screen.

I don't have a CAN charger, but may connect the BMS to my Sevcon Gen4 motor controller. I'm not exactly sure what it would do - advisory request to reduce power? I know BMS theory is supposed to use controls and not alarms, but there could be times when I would decide to destroy the battery bank to save the boat. I haven't thought it all the way out, but I'd like low voltage disconnect, only when I'm not on the boat, and then maybe excepting the bilge pump....unless it's having a problem cycling the same water with a clog...

Interesting thoughts. I am going to be using it with a Curtis 1232e controller. I'm also wondering what exactly it will need to communicate... I'd like to set the controller cutoffs to slightly above and below that of the BMS to ensure battery life, but as you say there may be times when one would want to kill the battery to save the boat... Bilge pumps, anchor lights etc are one of the reasons I went for a separate 12v bank. It means I can run my engine bank down to my set min getting into an anchorage and still be comfortable whilst waiting for it to charge up again... We spend most of our time at anchor, and I've more than doubled the capacity of the house bank with this conversion even though I seldom ran the AGMs down more than 80%

I think that would depend on if/how the two battery banks are connected. If they are completely separate except sharting the same definition of 0V/ground, I think you need two BMS and two shunts, two chargers, two everything. If the 12V bank is charged from a 48V charger powered by the 48V bank, I think a 48V shunt would capture all energy use, but not in realtime of its use. Well realtime from the 48V bank's perspective.

Correct, this is what REC have suggested. I've been struggling with how to display the battery info on a single screen, but think I am hitting a square peg into a round hole and should just have two of their LCD screens displaying each battery info.