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Old 19-08-2012, 03:13   #1
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Help a Newbie With Some Battery Problems (+LiFePO)

Hello everyone!

I have a somewhat selfish request to make... I'm basically a complete newbie to all things electrical and mechanical but I moved on to a sailboat a few months ago so I'm trying my best to learn as quick as possible. My problem right now is I was counting on the dated equipment on board to last me long enough for me to learn what I needed in order to replace and upgrade things but that's not working out. Several systems are having major problems and my 12.5 hour night shifts make doing the research tough and right now my head is spinning trying to figure out what to do with my batteries. I was hoping to throw myself on the mercy of the forums and see if someone could maybe just spell a few things out for me.

First thing... my house battery is shot... done. It's so dead that even plugged in to shore power it couldn't even run a few lights. I jerry-rigged my engine start battery to do double duty and that worked for a little while but now that battery is starting to do the same thing. Plugged in to shore power, I tried to turn on my water pump and everything on board went dark. No tripped circuits or anything, just as if someone pulled the plug. I just bought 2 Group 31 AGMs that I planned on using in parallel as a starting bank with a big reserve capacity. My thought was this would give me a good back up if my house bank dies while out on the water (as it did last week) and I need to do a quick ghetto rig to run lights and radio (as I did last week). Would there be any problem, theoretically, with using these to pull double duty as house and starting batteries until I get my actual house bank figured out?

I'm worried that there could be something wrong with my battery charger since the battery I've been using is now also starting to die, but that battery is also really old so I think it's pretty likely that that's the real issue. However, my boat did flood a good bit a few weeks ago (a story for another time) so it's possible that the charger got damaged then. I have a Sentry G120-3NL. I tried googleing to find a user's manual or something for it but was unsuccessful (I am stuck using my phone though...) Is there some way to check the charger and make sure it's working properly?

Next issue... I'm planning on replacing my house batteries with LiFePO and I've been reading all the info I can find on here about those and I think I'm just starting to get a handle on the fundamentals there. I'm trying now to figure out how much capacity I can fit and where I can fit it so I can start to price that out. I didn't get a chance to do a survey of my average power usage since I hadn't even gotten everything working before my house battery died. My goal is to eventually be able to live off-grid, so does anyone know of a good way to get at least a rough estimate of the capacity I'll need?

Then I obviously have some more research and work to do on how I'm gunna set up my LiFePO bank but I think there are a few fundamental things I need to figure out ASAP.

I don't think my current charger will be suitable for the LiFePOs so I've been thinking about how to replace it. My current best idea is to have 2 separate chargers, one for the LiFePO house bank and one for the AGM engine bank, and have shore power and the generator run both of them. That way, I can easily set up the charging regimes for the different chemistries, have some redundancy in case of emergency, and run the generator off the AGMs without worrying about running them down. (The generator was wired to run off the house batt before, which seemed silly to me...) Then I'd have the engine alternator also hooked up to the AGMs. Is there anything wrong/stupid with this idea? Would it cause a problem when I want to add solar/wind/whatever?

And then just something that's in my mind is that I'll also need to add an inverter at some point but I'm not sure if this is really an important consideration right now or not.

Sorry for the long post and especially for requesting the bit of spoon-feeding but it's been so hard to find info for complete beginners. The info I've found has been great but it really makes my head spin and for every question it answers I have 2-3 new ones!

Thanks so much!

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Old 19-08-2012, 03:35   #2
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Re: Help a newbie with some battery problems (+LiFePO)

Sounds like you are overwhelmed and it is very easy to do with all the marketing that goes on in the marine electrical (and many other) marine products. My suggestion is go simple--at least at the beginning. AGMs are expensive and fussy. Golf cart batteries are simple and cheap and reliable. Get a competent multi stage shore charger that can handle two sets of batteries of different types (most can) and then a simple battery monitor (Linklite) so that you know what is happening--otherwise you will be chasing your tail and buying stuff without knowing what is really going on in your system. Seems to me you have been lured into the swamp of complexity by the marketers, when what you need is simplicity. Read Nigel Calder on electrical systems--he isn't selling anything. In a disciplined, sequential way, go through each piece of your system to ensure that it is adequate and functioning and go to the next. Stabbing away at your faulty system by installing fancy products will probably not have the desired outcome.

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Old 19-08-2012, 04:28   #3
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Re: Help a newbie with some battery problems (+LiFePO)

I agree with Ray keep it simple. Are you living on the boat on your own? I suspect the flooding has killed the original batteries.

Those two type 31s you have just bought, are they engine starting batteries? if so any chance of taking one back and swopping it for a house bank battery like a Trojan T105 if it will fit, then buy another to give you a 225 AH x 12v house bank. This will do quite nicely as a house bank for the moment.

You won't need 2 x 31's for engine starting on that boat and in an emergency you could use the house bank. Next sort out the charger, either it works or it doesn't, so repair or replace. Now you have a simple system that works and you can live on board and give yourself time to sort out the long term plan.

Keep it simple.

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Old 19-08-2012, 05:22   #4
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That's a lot of questions...assuming you are plugged into shore power, even the really old batteries should run the lights and misc DC loads, especially since you don't have an inverter.

The first thing to do is find out of the charger is charging. You should see a voltage rise above 13V with it turned on. If it has AC power and is cabled to the batteries and you're not seeing that, it's not working.

I think you need to get the basics worked out, then worry about the long term. If the charger is faulty, some of your dead batteries may come back to life.
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Old 19-08-2012, 06:46   #5
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You did remove the old dead batteries. Connecting new to old is not good. When you cmbined the start to house the bad house bank sucked the life out of your start battery. when using many batteries for a large bank one bad one will bring the whole thing down. You have to remove the bad before you add the new. Best start with all new. Get nigal calders book or other on boat electrical systems.
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Old 19-08-2012, 07:23   #6
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Re: Help a newbie with some battery problems (+LiFePO)

you have your priorities a bit reversed, You only need one good battery for engine start. house batts. should be on one other system. engine altenator will keep start battery up. How you charge house batteries is up to you. Shore power operates charger which also runs all 12volt on boat except starting. matching charging system to amps use is not a simple thing. get some knowledgeable help there.

good luck
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Old 19-08-2012, 08:00   #7
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Re: Help a newbie with some battery problems (+LiFePO)

Try to keep it simple. The batteries are likely shorted inside, that is why they don't keep the charge and die. Chuck them and get new ones, we second the poster above who suggested golf cart ones. Also, make sure you don't parallel the starting batteries with the house bank. The old shorted batteries will start taking the new ones down if not. The engine alternator should then keep the starter battery healthy.

With new batteries in place you can check it the charger works. Again, as the poster above, beg, borrow or steal Nigel Calder's Boatowner's Mechanical and Electrical manual and read it cover to cover. You won't regret it.
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Old 19-08-2012, 08:48   #8

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Re: Help a newbie with some battery problems (+LiFePO)

I agree with all the above.
I have LiFePo4 batteries and absolutely love them, but you are not ready for them yet.
They're great, but way too spendy to risk on a system with the problems you currently have.
If you want to go LifePo4 batteries in the future, make SURE your system is perfect to start with and have a good monitoring system in place.

In other words, don't start with a Ferrari when you have your learner's permit.
Good luck and keep us posted on your progress.
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Old 19-08-2012, 19:56   #9
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Re: Help a newbie with some battery problems (+LiFePO)

Read this -

It is a good primer on battery and charging systems on-board. Chapter 10 is great as it has some typical setup ideas depending on your needs.

Some great advice here - In summary

- Do not invest in expensive/fancy batteries until you know how to take care of them.
- Start small and simple - $500 or so should get you sorted for the time being
- A good charger/inverter combination will take care of your short term and maybe long term needs while you have plenty of shore power
- A start battery G31 is plenty and should be isolated from the house (a simple 1-2-all switch is fine)
- As you already have 2 new G31 use the second for a single battery house for now

- Wiring the alternator charge and sense lines is a bit fussy and you should read Calder's book for details. Basically you want to make sure that the charge and sense wires are connected to load regardless of the isolation switch position.
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Old 19-08-2012, 22:24   #10
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Thanks everyone for your replies!

I actually have Calder's book ordered and I'm just waiting to get it in, so I'll be sure to study that when I get it.

I'm really trying not to get to far ahead of myself, it's just my hand is being forced a bit since things are failing. I really want to avoid buying a bunch of stuff now then end up shelling out more money in the near future to get the higher end stuff I really want. I understand that it'd be a bad idea to buy the expensive batteries without first learning how to care for them, but I've actually been looking at LiFePO for a while now. I actually started researching them before I even got the boat. My plan all along was to put some in as a house bank, I just expected to have more time to get everything else figured out. It might not be as urgent as I originally thought though.

It looks like my battery charger is not working. I haven't had a chance yet to check for small, easy-to-fix problems yet like breakers or fuses but even if I need to replace it that's relatively simple if that's all it is. Then I can definitely use some combo of the batteries I've got for a while until I figure everything else out. The main thing I'm worrying about is making sure that as I fix up my short term, good-enough solution, any new purchases will work with my future system. I think in my first post I sounded like I was trying to run out and buy all this new stuff when it's actually the opposite. I'm trying to buy as few things as possible right now but I've just got all this other stuff in the back of my mind that I'm trying to keep in consideration.

So hopefully for the short term all I need is a new charger. What do I need to look for in a charger to get a nice quality one that will: 1, be able handle my AGMs and LiFePO for the future; 2, work with shore power and the generator and to whatever extent necessary alternative sources like solar; and 3, anything I might be forgetting, lol? Things like SOC monitors and whatnot are gunna be completely separate from the charger, right?

Thanks again!
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Old 20-08-2012, 03:43   #11
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If you need a charger, I've found it's usually cost effective to get an inverter/charger if you want 100A or more of charging capability. Finding one that will work well for LiFePO4 requires either a MFG charging profile or user customizable profile for lithium. Two that come to mind are the Magnum MS Series with the ARC50 (not RC50) remote. The MS series inverter charger needs the latest firmware, so you will want to verify before you buy. The other is the Victron MultiPlus series and remote.
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Old 20-08-2012, 08:19   #12
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Re: Help a newbie with some battery problems (+LiFePO)

Most of the above posts are spot on! I just want to add a comment or two regarding chargers/batteries.

There are many thoughts pertaining to chargers! I have both styles on board, one provides charging, a Xantrex 1250 (or 5012??) which is a 3 stage charger that will accommodate 3 different batteries. My second a charger/inverter is a Freedom 1000 that I use for a house inverter along with charging my 24vdc battery bank.

Personally I do not recommend a combo even though I own one. Think about it. If either section fails, you risk losing everything.

As other suggest, keep it simple!!! A smart charger, 3 stages minimum is essential. Purchase a reliable digital multimeter, it will help you with voltage measurements and more as your skill increases. The Trojan T105 is a fine battery although it can be very pricey depending where you are located. I opted for similar batteries, Penns from Sam's Club, 230AH for $88 each whereas the 105s in my area sell for over $200 each.

You do not need batteries with pedigree papers.

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Old 20-08-2012, 12:02   #13
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I have 2 inverter/chargers. So they are redundant. And when they both work, I use the charge function of both. The latest ones allow you to parallel the AC side too, but mine are different ages and manufacturers.
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Old 20-08-2012, 12:28   #14
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Re: Help a newbie with some battery problems (+LiFePO)

The problem with LiFePo4 and TPPL batteries is that they really need chargers that are far larger than are readily available. They can take HUNDREDS of amps but alternators and generators just aren't big enough. If you don't take advantage of there amazing fast charge capability then their huge extra cost is maybe not worth it.

Give the electric car industry a few years to develop the technologies and they may then be worth looking at. Everything we think about batteries will change soon.
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Old 20-08-2012, 12:54   #15
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LiFePO4 is not hugely expensive compared to other sealed batteries. A theoretical 1000 AH requirement can be satisfied by a 1200 AH lithium bank. With AGM, it would require a 2000 AH bank. If your charging systems are compatible, the cost is roughly the same these days. If the cycle life claims pan out and the lithium outlast AGMs, the cost over time is less. There is no necessity to charge lithium at maximum rates, but it is an advantage.

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