Adding batteries to R27

[wincrasher]

My boat has the AGM battery upgrade. 2 house batteries, 1 engine and 1 thruster, all on the port side like every other R27.
I also have the deisel generator option. I believe these batteries are all group 27's.

Of course, I get that slight list to port like all the other boats with this amount of batteries and a generator.

I happen to have 3 fairly new Group 31 deep cycle batteries. I was thinking of mounting these in the starboard cockput locker and run 4/0 cables to connect this bank to the existing 2 battery house bank.

Not ideal, as the batteries would be a little mis-matched. But the cost is minimal since all I need to buy is the cabling and some mounting hardware. I may also alleviate my little list problem. Downside is it takes up some valuable space.

Good idea? Bad idea? Suggestions? Thanks.

 

[knotflying]

I would first ask myself if I really needed all that amp hour. I have an R-27 with all group 27 flooded batteries. I have the thruster battery joined to the house. I can comfortably spend three days on the hook.
I think adding batteries to alleviate a listing issue is not a good use of space. You may want to think of what heavy items can be stored on the starboard side.

Now for mixing battery types. The charge rate for AGM is different than other battery types so if you use the AGM setting you will be compromising your deep cell.

If you still want to add the batteries I would isolate them via a switch on/off from your current charging system and with careful monitoring either a) let them get recharged via the alternator when under way or b) install a separate charger for that bank. You will have to always remember to turn the switch on or off depending on the situation you are in, on the hook or on shore power.

To me the upshot is sell the batteries and redistribute existing weight as best you can.

 

[wincrasher]

All my batteries are AGM. That's probably why it was a $900 option, which is beyond ridiculous for 4 lousy batteries.

Switch is a great idea. Yes, I'm not crazy about adding weight overall. But there really isn't alot you can put on the starboard side to equal all that weight on the port, but I try.

I'm of the mind you can't have too much battery capacity, especially if you want to use the inverter. Ideally, I'd go all lithium and save a ton of weight, but it's more than I want to spend at this time.

 

[Scuffy]

We have the same setup. We carry a bunch of bottled water and seltzer under the starboard side of the berth. I keep a 65 quart Engel cooler on the starboard side in the cockpit as an extra seat and for the stuff I'm not allowed to up refridge space. You know like wine beer etc. The dink motor on the starboard side of the cockpit and the dink rolled up next to it. I keep all my tools etc. in the starboard cockpit locker. Seems ok now. I weigh a lot more than my wife so I stay on the starboard side when in the cockpit. I like the idea of the lithium batteries. They have come down a lot in price but not enough to suit me either.

 

[wincrasher]

It's not just the cost of the batteries. You may have to change your battery charger and your solar controller to ones that either can be programmed constant voltage charging (CV Profile) or have a built-in custom profile.

 

[stwendl]

If you look for leaf, yes the car, lithium battery sales you may be able to find 64ah 16v modules for about $80+ on eBay.

However I am not quite sure if all the electronics can handle that higher voltage. And it has already been mentioned that you will need a different charger, including the alternator on the engine. It would probably not be could for those batteries to be overwhelmed with the voltage assault of an engine alternator🙂. So we are talking about a new battery management system to not only keep the batteries healthy but also you safe.

 

[wincrasher]

If you look for leaf, yes the car, lithium battery sales you may be able to find 64ah 16v modules for about $80+ on eBay.

However I am not quite sure if all the electronics can handle that higher voltage. And it has already been mentioned that you will need a different charger, including the alternator on the engine. It would probably not be could for those batteries to be overwhelmed with the voltage assault of an engine alternator🙂. So we are talking about a new battery management system to not only keep the batteries healthy but also you safe.

You don't just by modules and bolt them together. A BMS is a required component. Most of the packaged batteries you can buy come with this and it includs high and low voltage cutoffs. Most I seen, and the ones I've purchased in the past, have a cutoff limit of 15 volts and they need constant voltage charging at 14.4-14.6 volts. That is where most alternators are as it is. What can damage the lithiums, and the jury is still out on whether this happens or not, is to continue putting voltage to them after they are fully charged. Most battery chargers would cut off when amperage approaches zero, but an alternator does not. So if you were travelling under power for days on end, would that situation damage the batteries? No one knows for sure. In RV duty, I've not had any such problems.

As far as "danger" goes, there is none with LiFEPO4 batteries we are talking about. The hoopla a few years ago was with LiPo batteries on aircraft (and in these hoverboards and laptops and some electric cars). Those are a different chemistry altogether and can get quite hot under discharging and charging. A Tesla has an integrated cooling system on it's batteries. The deep cycle LiFEPO4 batteries for boats and RV do not get hot at all, but they can be damaged (and your $ down the drain) if they are baked in a hot engine compartment, or you try to charge them in below freezing conditions. So some care must be taken on placement and control of charging.

 

[knotflying]

All my batteries are AGM. That's probably why it was a $900 option, which is beyond ridiculous for 4 lousy batteries.

Switch is a great idea. Yes, I'm not crazy about adding weight overall. But there really isn't alot you can put on the starboard side to equal all that weight on the port, but I try.

I'm of the mind you can't have too much battery capacity, especially if you want to use the inverter.

You can have too much battery capacity if you never need it. I would add up all your anticipated Amp hours needed and then determine if you need the additional amp hours. If you don't need the amp hours then redistribution of weight will give you what you really need to compensate for the listing.

Quite frankly I rarely use my inverter and since you have a generator, additional amp hour capacity is highly unlikely. If it were me I would redistribute my weight and use the boat for a while to determine if you really want the additional weight and need the additional amp hours. After 5 years of using my R-27 I rarely went below 80% state of charge when anchored.

 

[NewMoon]

If you travel faster than 6 knots or so very much, unnecessary additional battery weight is not good.

If you think it could be helpful, I could email an Excel spreadsheet that I used to calculate amp-hour requirements for our 26-foot cruiser. Document on how to use it as well. Since it usually takes a number of iterations to get to an AH estimate that seems pretty good, doing the arithmetic by spreadsheet makes the process a lot easier.

Knowing AH requirements between recharges let me make a good decision on the size of my battery bank, and also on my alternator. I replaced our stock one with a more robust externally-regulated one, and a Balmar MC-614 multi-stage regulator. Pretty much essential if you have or need a large house bank.

Another way to figure your AH requirement is to install a battery AH monitor, such as the older Link 10 or Link 2000, or the more current Victron BMV-700.

 

[wincrasher]

After all this, and discovering that the ProMariner charger will do lithium, I've decided to switch the AGM's out to LiFePO4 batteries.

I'm not increasing the count, but with the ability to draw down to lower SOC, I'll have more battery capacity available.

Each will be 125AH. So at 90%, that gives 225AH available on two batteries, 337.5 AH if you tie in a third.

Weight savings will be 152 lbs on the port side. Another nice side effect is that these can sit in storage when the boat is not being used, as there is no appreciable self-discharge. They are rated for less than 1% in 12 months sitting idle.

 

[NewMoon]

Hi wincrasher,

You may want to read through MaineSail's articles on LiFePO4 batts before dropping a wad of cash.

http://www.pbase.com/mainecruising/lifepo4_on_boats

Among many other cautions, he suggests that you MUST have the proper charging equipment, including an externally regulated alternator, and a charger, that allow 100% custom programming.

A simpler less financially risky approach might be to replace your AGM's with Firefly's carbon-foam AGM's.

 

[wincrasher]

I couldn't find in that link where he talks about alternators.

My charger is programmable and will cut off at full charge according to the correspondence I've had with ProMariner. The acceptance rate on these batteries is well above the output on the alternator, and the BMS will control voltage spikes. I would like to install a way to cut off charging from the alternator - the Balmar may be the way to go (haven't gotten that far). Optimized systems generally include big charging currents to get those fast recharge times. In my application, I won't be doing that at all. Low current charging does add to the safety of the system and durability of the batteries. I've seen first hand systems putting 300+ amps into a battery bank (in RV applications) - it's pretty impressive to say the least.

Our chargers put out 20A theoretical. The alternator maybe has 80-100 A to give unless there is a breaker or relay limiting (which would not be surprising considering lead-acids have a fairly low acceptance rate). The solar is 7 A tops.

I see my usage generally as put some charge in, take some out. Not endless charging plugged in or motoring for extended periods (days). My solar controller will most likely need to be changed out - I don't see that our Morningstar supplied unit has a CV profile.

I was concerned that Ranger would have supplied two different types of batteries for house and engine/thruster, but apparently they are all deep cycle type.