Recent content by migs

A rough estimate for the average daily energy from a solar panel can be made by dividing the panel’s nominal power output by four i.e. a 120W panel will produce about 30Ah per day (on a 12V system during a Northern Europe summer). However, first of all minimise your fridge’s energy consumption...

The link to the article in post #1 is now closed. My thanks to those who provided constructive comments.

Here's our response (in advance) to the howls of anguish. Got to go sailing now - that's quite enough of enough of this armchair stuff for the moment... ************************************************************************************************************************* Ah that's better...

Somebody hasn't read the article... we don't use a disconnect switch at all - for all the reasons above - plus the explanation in our submission. 'you explain that they [the cells] are in balance but you don't know' Surely a system that always runs with a cell balance of <20mV and has a...

By introducing a disconnect switch, lithium systems have actually taken a giant step backwards compared to lead as: * Battery current delivery is throttled and the battery's source resistance increased * A single point of failure has been added to the boat's primary circuit (no doubt relying...

Thanks, GHA and noelex for your explanations.

'the batteries get back up to the same SOC pretty much every day as bulk cuts off towards fully charged' 'The regulators go back to bulk if the voltage drops whatever the figure is below float, doesn't happen very often' How does bulk cut in every day if it is triggered by the battery's...

'250A or 300A mrbf fuse for each pack' Surely each BMS must protected with a 200A fuse as anything bigger could overload your 200A BMS. However, if you are pulling 220A and one pack goes down, you will immediately lose the other one. With a 2P4S configuration you will get 1,120A (for 30s) -...

For GHA: It seems like setting a charger 'float' voltage of 13.35V is effectively using the charger in 'power supply mode'. Clearly this approach works in practice, but over a period of time, surely the total charge in and out won't balance and the batteries SOC will become unstable. I guess...

'It took me 2 weeks to rewire my boat for lithium. We have numerous charging sources that were all configured for the lead batteries. Lots to change' It took us 2 hours to rewire our boat for lithium. We have numerous charging sources that remained configured for lead batteries, but there was...

For a disconnect relay (or mosfet switch) failsafe is an interesting dilemma: a) Fail-open and you lose all of your boats electrical equipment b) Fail-closed and you could damage the battery by discharging it completely Take your pick...

'At a 260A rating you are at the top end of many 35mm2 cable (cool/outside conduit) and some connectors (e.g. Anderson 170A) hence why they sensibly suggest 50mm2. What size cables do you have?' In a circuit, the cable size is determined by the fuse protecting the cable. All components in the...

"That relay looks interesting. I cannot find any quiescent current on the datasheets so I assume its near zero." Here's an explanation for non electronic geeks: a bistable (or latching) relay's contacts are held either open or closed by strong magnets. The contacts are flipped from one state...

geem, knock it off, you know what Zing means - you're better than this ;)

'Nice write up @migs. Got any more details on your BMS and relay/contactor used?' Thanks for your comment. There are a couple of reasons why I haven't posted details of the BMS on github yet. One is the (faint) hope of licensing the design to an enterprising manufacturer; the other is that...