Boat Re-Wire

[Lovey80]

A little bit of an update.

have just spent the last two days fishing in the Sandy Straights. Probably 50/50 usage of outboard for some 30 minute runs and stop start fishing while drifting for whiting and around 4 hours a day at spot lock. The salt water pump is by far my biggest draw and it running WOT draws a staggering 25amps. The weather has been pretty good and I don’t think I’ve seen more than about 1.6amps being drawn from the 55Lb trolling motor. Which BTW I’ve been very impressed with.

Total amps used each day was just over 20Ah. Getting back to camp and throwing the 15A charger on both batteries separately saw both cycles completed all the way to float (0amps) in well under an hour. I probably didn’t need to go as large as 163Ah house battery but it’s so small and light I’m glad I did because now I know I have a ton of redundancy.

I hope my little project helps someone else that may be heading down the same path and if I have any major issues I’ll be sure to update the thread accordingly.

[Monza]

VSR bought and going in tomorrow. Are you able to answer the current draw between the two?

If you’re using Lithium as both start and house battery, a VSR could cause issues. Most VSRs simply use relays to join the batteries in parallel once the starter battery exceeds 12.8V. Charge current then goes to the battery with the lowest charge. But as you correctly note, if the house battery is nearly empty it will draw current from the starter battery as well as the alternator.

Lithium batteries have very low internal resistance which means (subject to the batteries BMS) they can draw or absorb huge currents. Hope your batteries, VSR and cabling are up to the task as the house battery could draw huge currents from the starter if almost flat. A lot of VSRs have an inbuilt connect or disconnect delay, so after 15 seconds or so, if the current is too big and the starter voltage drops too much, it will disconnect and try again later.

The other issue is the connect voltage of VSR is 12.8V. This is fine for lead acid as it represents nearly 100% charge, but for a lithium this resting voltage may only be 20% charge. That means most of the time the VSR will be active to both batteries, perhaps even at rest.

For the above reasons I’ve gone away from VSRs for lithium and use diode or FET type isolators instead. This ensures the batteries are never connected and alternator charge is distributed evenly to the lowest charged battery. Just make sure you don’t run both batteries flat. I also have 2 manual switches that can direct the house or starter to either battery.
https://www.outbackmarine.com.au/pow...tery-isolator/

[Lovey80]

I actually cut the little red wire in the back of the VSR and wired it into the ignition so that the VSR will only attempt to do its thing when the outboard is running. Wired in the standard configuration, once I charged the starting battery above 13.4v both batteries were in parallel constantly as neither was ever going to get to the 12.8v cut off.

The most I’ve seen difference in voltage was about half a volt. 13.48v on the little start battery and 12.99v on the house. Intentionally drew down the house battery over night. When starting the outboard on the muffs the cables that connect them remained cold, though I only ran the outboard for 15minutes.

With my usage I can’t see a scenario where the house battery uses more than 10 amps or so between outboard starts when the VSR kicks in. That’s about 25% of the start battery’s capacity that could flow across to the house. Not too worried about that.

[NAGG]

Thanks for the input Darren.

I’ve just installed an Enerdrive 40 Dc2DC in the truck as it has a solar panel and it’s working great so far.

The strange thing about the boat set up is the Victron charger (lithium profile) charges at 14.2v with reducing amps on the absorption phase then knocks back to 13.5amps on float. So after a night of charging the batteries are sitting on 13.5v. On the Victron forums on FB they’re telling me the batteries are at least north of 95% after this charge profile is complete and to not think of the SOC in terms of voltage in the same way as you would a lead acid or AGM.

The outboard is putting out 13.8v to both batteries. Day 1 I did very little running of the outboard (under an hour) and day 2 got about 2-2.5hours worth. The shunt accounts SOC as purely the Ah used since the 100% reset and was telling me the house battery was at 60%. This doesn’t account for any charging done by the outboard. So for the 163Ah battery I’d used 65Ah over the two days. Yet it only took 2 hours on the 15A charger to finish the full charge profile and be on float. This tells me the outboard has put in somewhere around 30-35amps over the say 3 hours of outboard run time. Which lines up pretty closely with what Suzuki says the outboard has available after running itself (11.5a).

I’ll be as religious as I can about charging both batteries on 240v each night and hope I don’t fry the stator.

I've been using the Victron chargers in my barcrusher to charge my 2 LiFePO4 batteries & what you said about the 95% is spot on . That is one of the cool things about Lithium & the use of proper Lithium chargers like the Victron blue smart. You can can pump in the full 25amps up to the 95% before the charger reduces the charge input. My recent trip to Crowdy head saw me spotlocking in pretty marginal conditions for about 6 hours solid - when I got back to camp & hooked up the gennie it took just over 2 hours to hit "absorb" (125amp batteries) .... 95% Now when you are off grid - the less time you need to run a generator , the better

As for having such a large battery capacity ...... you've done well - There are going to be days that when you spot lock you could be running 8s on your leccy & pulling some serious amps (particularly with that type of hull) - secondly it means that if you can have big sessions & not worry about running out of juice . I just did an upgrade from 100 to 125 amp ... a modest increase but enough to give me a full days spot locking - something to appreciate if I'm doing a trip up to the Whitsundays or Lucinda and manage to get out to the reefs.

Anyhow it sounds like it came together nicely for you

Chris

[Lovey80]

Just a bit of an update on this thread. When I did the original re-wire I stuffed something up. By bolting my TM and Start battery parallel negative wires straight to the negative on the house battery, it completely bypassed the smart shunt. That meant any charge from the outboard and draw from the TM weren’t being recorded. So back to square 1 on what I can expect as far as draw etc. I’ve added a couple of dual stud terminals after the shunt and now the only thing between the negative on the house battery and the shunt is a 100a Daly BMS. I’ve also wired in a Heltec 5A active balancer in parallel with the BMS.

The balancer is one of the ones Power Paul Australia had heltec make specially for him. They turn on one once each cell hits between 3.4 and 3.43v. This is perfect for LifePo4 profiles as this is the start of the steep part of the charge curve when unbalanced cells (or cells with lower capacity) really start to run away. The house battery up until this point had no BMS or balancer. After maybe 10 fishing trips and a year or so after install (I top balanced the cells at the start). The cells got to 50mv deviation before I plugged the balancer in and it had them balanced to less than 5 mv in about 5 minutes. Something the Daly BMS had no hope of achieving and at $30 was a great investment. I wired them into a sealed plastic box on the outside of the battery box. I’ll add some pics of how it ended up later and will give another report on the power usage.

AE4E1B8D-E62F-4BB8-BE5D-D75FBDBA6591.jpg

I did a bit of a test to see what would happen if I had a situation like I was worried about earlier in the thread with paralleling batteries with vastly different states of charge. With a full 163ah house battery and a start battery at about 25% SOC. The max I could see going between the house and start was 12.8amps and it dropped off fairly quickly to 8 amps after about 5 minutes. I had the Victron shunt and the clamp meter running next to each other and they were almost identical.

for those interested. The little Suzuki 60hp outboard puts in 3.5amps charge at idle and 13.5amps 3000rpm. I know that’s not a huge deal but considering my trips inside the great Sandy straights have quite a lot of engine running time and more remote trips. Any length of time I don’t have to run a generator to charge boat batteries will be a bonus.

[ranmar850]

I'd love to participate in this, or any thread, but the forum is still screwing me around. Yes, I have cleared all cookies, logged out/ logged in, done all the things suggested-- it required a lot of in and out to get my House Battery thread more or less done, haven't been able to do anything but lurk since. Edit---- I posted this from my phone, no problem. Then I opened the site in Edge , and it seems OK.