Pearson Boats - Common Systems > Electrical Systems & Electronics
Modernizing a 40+ Year Old 12v System. GROUP DISCUSSION
Valor:
I'll start this off by saying this topic might go sideways at some point because there is a lot in it but let's give it a shot. I'm sure there are older posts about this if a search is made but I am trying to make this a current post discussing modern/current 12v tech.
The more stuff we add to the boat, the more of a demand we place on our 12v systems. Looking to modernize some aspects of it and to create a more efficient charging/12v system. Listed below are just a few of the options I have been researching and I was curious if anyone has any current experience with this topic so far. All of this leads into solar panels and some other stuff I would like to add next season. I am doing all of the leg work now to have the plan in place. If anyone has a component to add they had good luck with please add it to this list and we can start a discussion on it. Please try to keep the tech discussed current.
Has anyone replaced the existing circuit panel with a newer one? Did you go bigger? Custom? Etc?
Has anyone added an additional panel to the existing board? If so where did you put it and what is it for?
Does anyone use a DC-DC charger to charge multiple banks?
Does anyone use a Agro FET battery isolator?
What MPPT charge controllers is everyone using?
Battery monitor? Which one's are you currently using and do you like it? Accuracy?
Batteries- How many and where did you tuck them away?
Anyone using 6-Volt in series house banks?
Alternators? Stock or larger Balmar etc?
ACR's?
Let start here and see where this takes us. The goal here is for everyone to benefit from the information gained. Thanks in advance and Happy Easter/Passover and whatever else.
Dolce_Vita:
Wow! What a huge topic! But one near and dear to my heart, as i am currently approacking a long-considered overhaul of my 12v system.
Here's answers to a couple of your questions:
What MPPT charge controllers is everyone using?
I am using a Midnite Solar "KID" MPPT controller, with two 100W panels in parallel, soon to be upgraded to two 200W panels. The KID can handle up to about 600 watts on a 12V system.
I was originally given BAD advice by Midnite Solar regarding the need for their optional "WhizBang Jr" current sensor. Their experience seems to be more focused on off-grid type installations with separate charge and load busses, and they don't really understand the unique needs of a marine installation. At any rate, the lack of a proper battery current sensor virtually guaranteed that I would consistently overcharge my batteries because the charger couldn't distinguish between the current charging the battery and the current being consumed by the boat's house loads such as refrigeration. The end result was that I destroyed an expensive pair of Gel Cells in two years when the previous pair had lasted me ten years! I am in the process of adding a WhizBang Jr sensor which will allow me to program the charger to terminate the acceptance phase when the battery's charge current drops below a specified limit instead of using an arbitrary timer.
Battery monitor? Which one's are you currently using and do you like it? Accuracy?
I installed the Xantrex LinkPRO battery monitor years ago, and I use it constantly while we are out cruising. The interface is somewhat cumbersome, but it works. I tested the voltage calibration against two different high quality DVMs and all were in agreement. Have not tested the current reading accuracy but have no reason to question it. If I were doing it over today, I might pick the Victron.
Alternators? Stock or larger Balmar etc?
I replaced the Mando 55 Amp alternator that came with the boat with a 110 Amp Amp-Tech alternator. Because of the low speed that my Atomic 4 engine spins its alternator, I will never see 110 amps of output. When starting cold into a partially discharged battery bank, It briefly gets up to 60 amps, then quickly comes down to a bulk charge rate of about 40 amps. This is to be expected. The benefit of the larger alternator is that it is not running anywhere close to its maximum output and runs cooler and will last longer. I use a Balmar MC612 external regulator to control it. The Balmar is almost infinitely programmable, but has the same flaw that plagued my Midnite Solar installation: No battery current sensor! Thus, there is NO possible combination of settings that will always fully charge without frequently overcharging! Flooded batteries can tolerate this, if they are kept well watered, but Gel Cells cannot! They incur some permanent damage each time they are overcharged. (And Lithium's are even worse, suffering catastrophic failure if they are allowed to overcharge.) Again, if doing it over, I would consider the Wakespeed WS500 alternator regulator, as its the only one I have been able to identify that uses a battery current sensor.
Batteries- How many and where did you tuck them away?
Saved the biggest item for last.
The house bank currently consists of two 100 amp-hour Group 31 deep cycle Gel Cells (NOT AGM!) wired in parallel. A separate 32 amp-hour U1 gel cell is used for a starter battery. All three batteries are located in the port-side cockpit locker. This provided a house bank of about 200 amp-hours. But since you should not discharge lead-acid batteries below 50%, this means that there is only about 100 amp-hours of usable capacity. Further, since the last 20% of charging is the acceptance phase, which can take hours, it means that unless I plug into shore power, I rarely have the batteries up to more than 80% after the first night. In effect this means that I really only have about 30% (60 amp-hours) of usable capacity!! Since the refrigeration consumes most of this, I have to charge whatever I can with solar during the day, and make up any shortfall by running a small 1000w Honda generator which powers my 40 amp shore charger.
Although this worked, I would really like to to be able to go several days on available capacity, as well as harvest more solar power (hence the panel upgrade) so as to not regularly need the generator.
And so, I am in the early stages of coming up with a complete redesign incorporating Lithium-Iron-Phosphate (LiFePO4) batteries. The batteries will be built up out of four separate 280 amp-hour prismatic cells. There will be two separate batteries, each protected by its own battery-management-system (BMS) board, for a total raw capacity of 560 amp-hours. Because LiFePO4 batteries can be safely discharged to around 20%, and remain in bulk charging almost all the way up to 100%, this gives a usable capacity of about 80% or close to 450 amp-hours!
Because LiFePO4 batteries have a 150 deg F operating limit, and the locker adjacent to the engine gets too hot when the engine runs, I am considering moving the batteries to the space occupied by the storage bin under the nav station. Each battery will occupy a footprint of aprox. 7" x 11 1/2" and stand 8" or 9" tall, so they should fit there, with room for the required bus bars and BMS boards.
But I need to warn you (and anybody reading this) that I really have gone down the rabbit hole on this one! The engineering required to do this right is significant, and there are no commercial products out there that get it all right, requiring a high degree of custom design. Don't believe a word of it when anybody tries to convince you that there is a "drop-in" lithium battery that can replace your lead-acid ones. It just isn't true. These installations will work great, in the short haul, but will not last and will destroy your expensive investment long before its promised life. A proper LiFePO4 battery has to be part of a system, including the BMS, the solar charger, the alternator & regulator, and the shore charger. ALL must conform to the unique charging requirements of Lithium batteries, and cooperate in the task. There's a lot of information and cautionary tales on this topic at Compass Marine (https://marinehowto.com/lifepo4-batteries-on-boats/) and Nordkin Design (http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/). If you're at all considering going down this route, I strongly suggest you read it all.
Valor:
If I was a betting man, my money would of been on Ed to reply first.
Great great info Ed. Regarding the MPPT controller Kid you are using. I to have had conversations with Midnight Solar and to me it really didnt seem they new marine applications at all. I have spoken with a few different tech people and received 3 different answers to the same question. So for me I moved on from them.
Ideally if I could use the same brand for as much of this build as possible, then tech support cant blame someone elses product installed in the system if it doesnt mesh properly.
Regarding the battery monitor, I currently don't have one. I am steering towards the Victron 712 smart. All of the parameters are visible via bluetooth to an app on your phone and its around the same price as the others. From what I have read, it covers a wide range of battery systems.
Regarding the Alternators, many if not all of the Alternators today are smart meaning they work with a vehicles onboard computer system to regulate output. Our boat have the old school dumb tech where the Alternators are regulated by regulators that usually do not have the batteries best intrest in mind. Our low rpm engines also add to the problem because the Alternators are not rotating at a speed to maximize the charging. The way around this is to increase the speed of the Alternator by swapping out to a smaller pulley on the Alternator and overdrive it. I have done this to a few classic cars I have owned that spent a lot of time sitting and i was able to really drop a charge onto the batteries safely. The regulator will keep everything in check as long as it is programmed properly. The principles are the same to any engine.
Also a thing to consider is adding a dc to dc charger. The idea of it is just a great concept. Under power your house bank gets charged off of your starting battery. The starting battery is charged by the alternator. The charger views the house bank not as batteries but as a load on the starting battery i.e a string of lights or a fan. By doing this it will push more amps to the starting battery which offsets into the house bank through the charger.This offset is based on which charger amperage you buy i.e. 20 amp 30 amp etc. Unlike your regulator the charger will act like a true 3 stage ac charger. It will continue to call on the Alternator to push amps into your system to counter the load placed on the starter battery until the voltage across the banks is 80% then floats then maintains. It is highly used in the rv world and has carried over to the marine market. It is considered the best way to rapidly charge a 12v bank to almost 100% with an Alternator. Based on how you described the damage to your gell batteries from over charging. I am almost certain a dc dc charger will correct that issue because the charge considerations are place on a charger and not a regulator.
Regarding batteries. I love the lithium plan you are working on and would love to see what type of system you come up with. Im torn between 2 6v batteries in series or 2 4d batteries parallel. Both would give me 400+amphrs total and about 200 usable.in regards to placement, what ever batteries I go with will be mounted in the v berth within each side compartment. I know the battery cables are going to be uber expensive for such a long run but there is waaay to much weight on the ass of these boats. The amount of squat under power is already too much. I think the weight on the bow will help the stern come up a little.
Thanks again for kicking this off Ed. Great start!
Dolce_Vita:
More Commentary.
Does anyone use a DC-DC charger to charge multiple banks?
I don't currently have any experience with this, but I'm leaning towards incorporating one in my new design. I plan to hava a small lead-acid battery for the starter, and a DC-DC charger seems like a good way of handling charging of two different battery chemistries. There are two options.
* Let the alternator charge the lead-acid starter battery, and use a hefty DC-DC charger to get the alternator's output to the LiFePO4 house bank.
* Let the alternator directly charge the LiFePO4 house bank and use a small DC-DC charger to keep the lead-acid starter battery charged.
Each has its advantages and disadvantages.
Option one avoids the dreaded "load dump" that can happen when using an alternator to charge LiFePO4, where the BMS disconnects the LiFePO4 battery to protect it, and the alternator output spikes violently, burning out alternator diodes and expensive boat electronics. In this option, the lead acid battery is always there to load the alternator output. The disadvantage is that you need a fairly hefty DC-DC charger to take advantage of the alternators full output for charging the LiFePO4 house bank.
Option two takes better advantage of the alternator output because it goes directly to the house bank without incuring the losses of a DC-DC charger. It also can use a smaller, les expensive, DC-DC charger to keep the lead acid starter battery topped off. One of the disadvantages of option two is that it will require a battery-current-sensing alternator controller, such as the Wakespeed WS500, to properly charge LiFePO4 batteries. Another is the "load dump" problem. This problem may be mitigated by the load that the DC-DC converter always presents to the alternator, but I wouldn't want to bet the farm on it.
My current thinking is that option two is the way to go. DC-DC converters are notoriously inefficient, and I'd rather incur that ineficiency loss on the small charging that the starter battery would require than on the big house bank's charging. As for the "load dump" problem, my approach is a threefold "belt & suspenders":
* Use the DC-DC charger as a constant load on the alternator
* Construct the LiFePo4 house bank as two separate, paralleled, 12V batteries, each with its own separate BMS. This greatly reduces the chance of a load dump as now both batteries need to go offline at the same time. Each battery + BMS must be sized to handle the maximum current draw of the system independently in order to avoid a cascading failure mode.
* Install a Sterling Alternator Protection Device on the alternator output to absorb any spike from a load dump
Valor:
Ed,
--- Quote ---Let the alternator charge the lead-acid starter battery, and use a hefty DC-DC charger to get the alternator's output to the LiFePO4 house bank.
--- End quote ---
Option A sounds like a good plan. It doesn't need to be a hefty charger. You can parallel many smaller DC-DC chargers you want to bump the amperage. By doing so you are also creating redundancy. If one of your chargers in parallel fail you still have another. If you have 1 hefty charger and it fails you have nothing. Also, if anything would take a hit it would be the cheaper, easily replicable lead acid battery on the front line instead of the expensive lithium's. B sounds like a great plan as well, but it seems there would be a few more moving parts and the fear of spiking a Lithium would be looming if you drain them deep enough. You could always start the boat and run the house from the house bank if something happened to the starting battery. You wouldn't be able to do that so much on just 1 starting battery.
This is from the Victron site:--https://www.victronenergy.com/dc-dc-converters/orion-tr-smart-non-isolated
This is the spec sheet:-- https://www.victronenergy.com/upload/documents/Datasheet-Orion-Tr-Smart-DC-DC-chargers-non-isolated-360-400W-EN.pdf
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