How to: Lithium batteries, alternator and dc-dc converter.

[CaptainRivet]

Originally Posted by HeinSdL

When I bought my boat it came with a starter battery and 4 x 120Ah lead acid batteries. Probably weighing around 120kg. There was a Septor managing the connection between engine and house battery.

On the load side the main consumer was/is a 40A water maker, without running that the boat consumes about 80Ah on a typical day. This set up did not really work for me. The engine would barely charge the house batteries (sending an anaemic 10A on when it was feeling in the mood) if the Septor actually did its job which was also an issue.

So I installed a Simarine system which now allows me to monitor every current everywhere which has proven to be absolutely great. And it has showb the alternator was doing very little in terms of charging.

So I took out the Septor and made it a manual on/off switch. At least I knew the connection was good but the moment the sun came out (now also have solar) then alternator would fade away again. All in all pretty frustrating especially not being an electrical engineer. But I am a mechanical engineer and so I thought: pump! And hence the 30A dc-dc charger was installed. Worked great! Finally the alternator was beginning to get a bit stressed and I could almost run the water maker without draining those stupid lead acid batteries which were supposed to be damaged at 70% SOC??

And now this year I am moving to lithium. 1 x 300Ah LiTime, maybe another one in the future. The shore charger is a 110-240V input 50A 12v Victron charger, Solar 100/50 delivering max 30A and the 50A XS dc-dc is there when I need to have the alternator do some work too.

And the 'old' 30A dc-dc I will keep to potentially charge a small lithium battery for the dinghy which has a weird looking electric outboard.

For my boat I am done for the time being. All lights are LED, standard NAV equipment and one 500W dc/ac converted to run some kitchen appliances now and then.

This will work for me. It can always get better but gosh I now understand everything. Which is a big improvement on 5 years ago and which annoyed me. $$/sanity-wise, I have gained even though the path was not a straight line.

Fully agree thats thats the standard install with very little changes to the ship. Dc2DC, drop in LI batteries, adjust your solar and shorepowerbcharger to lithium and you are good. Maybe BMV712 instead your simarine, which is great too.

What people don't realize when getting drop ins or mosfets BMS lithium batteries, can you use your house as emergency starter or can i run the windlass via them?
Just yesterday took 2 JBD BMS out of an install at my pontoon and showed the owner was i expect to see was true. 100A version and 2 batteries with each 280AHEVE in parallel. On both BMS from 8 mosfet 3 on one and 5 on the other where already burned, both still worked but won't for long anymore. I expect surge current of the windlass and/or power whinch blew them. Windlass has around 120A so surge must be in 300-400A range when eg you pull out an anchor (yes you shouldn't but happens more often then you think) or its stuck. A starter on a 3 or 4 cylinder between 20 and 75hp is in the same range 180A and peaks to 300-400A. The 200A and around 500A peak from both BMS together seam to be enough but for the first millisec if you are unlucky the whole current goes to the weakest mosfet that turns first on and blow it and then the other of the parallel mosfets array take over. This because they are not matched and calibrated...you cannot offer BMS for 100-150 Euro for this price with calibrated and matched mosfets, impossible or you bankrupt soon.
The cells can do this easily but the BMS is the limiting factor. Thats why you need 2x200A BMS here, the rating of these chinese BMS need to be equal to the surge currents, then you are safe.
Well and in drop like LITIME i highly suggest to do the same that continuous discharge is equal to surge peak current expected.

[HeinSdL]

Originally Posted by CaptainRivet

Fully agree thats thats the standard install with very little changes to the ship. Dc2DC, drop in LI batteries, adjust your solar and shorepowerbcharger to lithium and you are good. Maybe BMV712 instead your simarine, which is great too.

What people don't realize when getting drop ins or mosfets BMS lithium batteries, can you use your house as emergency starter or can i run the windlass via them?
Just yesterday took 2 JBD BMS out of an install at my pontoon and showed the owner was i expect to see was true. 100A version and 2 batteries with each 280AHEVE in parallel. On both BMS from 8 mosfet 3 on one and 5 on the other where already burned, both still worked but won't for long anymore. I expect surge current of the windlass and/or power whinch blew them. Windlass has around 120A so surge must be in 300-400A range when eg you pull out an anchor (yes you shouldn't but happens more often then you think) or its stuck. A starter on a 3 or 4 cylinder between 20 and 75hp is in the same range 180A and peaks to 300-400A. The 200A and around 500A peak from both BMS together seam to be enough but for the first millisec if you are unlucky the whole current goes to the weakest mosfet that turns first on and blow it and then the other of the parallel mosfets array take over. This because they are not matched and calibrated...you cannot offer BMS for 100-150 Euro for this price with calibrated and matched mosfets, impossible or you bankrupt soon.
The cells can do this easily but the BMS is the limiting factor. Thats why you need 2x200A BMS here, the rating of these chinese BMS need to be equal to the surge currents, then you are safe.
Well and in drop like LITIME i highly suggest to do the same that continuous discharge is equal to surge peak current expected.

I considered this for a good while. The 300Ah Litime battery has 200A continuous discharge rating. I have a 1000W windlass so I thought for a looonnng time about water maker and windlass running together, nominal 120-130A. Throw in some peak load and you might get to 200A. Throw in the reviews of some Litime batteries on youtube and they seem to be pretty robust even with the occasional spike at 300A. Now I also have one electric winch for halyard work so I do need to make sure we don't haul in anchor, raise the main and run the water maker with the engine off, etc. But I can probably handle that....

Currently I have two fairly good Exide 120Ah AGMs on board and they will stay on board. Two functions: back up, disconnected, when the lithium is in use (so if the Litime kicks the bucket because it turns out to be crap after all) and fully in use when the boat is dormant. So with the boat dormant the lithium will sit disconnected at 50% for a couple of months and the AGMs will be trickle charged by solar and will drive the bilge pump etc. To switch between lithium and AGM is one lead moved across.

And if I like the setup I will indeed put a second Litime alongside with 400A total continuous discharge current which will convert the boat into a floating power palace compared to what I used to sail in Round Britain and Fastnet races in the late 80's and early 90's. What a palaver running the engine every day with no clue what was happening in the batteries. But we got by. Just didn't use any electricity except for the Decca, later GPS, and nav lights. As for windlasses, electric winches and water makers... pffff.

[HeinSdL]

.... And in a way I do start feeling a bit nostalgic. Next step electric cooking and the boat will be a buzz of electronics and currents wizzing around and I mght start considering, why not rip out everything and go back to just some nav lights, a handheld GPS and a night light above the chart table...

I presume most have heard the story about the man in some pleasant country somewhere, spending his morning fishing providing for his family and spending the remaining part of the day enjoying time with his family? Until approached by a western tourist/capitalist? Happy to tell if there is demand and Jedi allows the thread drift.