Battery charger

Submitted: Sunday, Nov 30, 2014 at 08:54
ThreadID: 110290 Views:2105 Replies:6 FollowUps:4
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Hi all,
We have a set up in our boat, with a 120amp deep cycle battery mounted in the bow, to run a front mounted minkota, and the marine battery for the start battery (50hp four stroke Yamaha)mounted in the stern.. Not sure of the size off the top of my head. At present, I use an older style charger, which I climb in the boat, and swap from one battery to the other, just looking to find a better/ more inefficient way of doing it, think the old charger is 6amp, with a fast and slow charge switch, is it possible to have a charger, which will charge , then float both batteries together, if so, what brand and size should I be looking at.. Any help and suggestions would be great. Thanks. Odog
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Reply By: Notso - Sunday, Nov 30, 2014 at 09:06

Sunday, Nov 30, 2014 at 09:06
Plenty of chargers that will do the job. If you use EBay Search for Smart Battery Charger.

Don't buy the really cheap ones you'll find. Ctek, Redarc are two good brands.
AnswerID: 542363

Reply By: Member - bbuzz (NSW) - Sunday, Nov 30, 2014 at 10:12

Sunday, Nov 30, 2014 at 10:12
Hi Odog,
I have a two battery setup in my Quinny.

I mount a 2amp? solar panel (not a milliamp one) on the roof of my carport and run a lead to both batteries.
I have attached a cigarette lighter socket to each battery and mounted them on the outside of the battery box. A wine cork stuck in the socket keeps the moisture out.

When I am home I plug the leads into the sockets and let the solar take over. It is usually a week at the least, between using the boat, and if I have charged the batteries (like you with the older charger) as a starting point, then I find that that the solar can keep the charge up.

Climbing in and out to charge the batteries is easy as it is only a matter of plugging in.

Works for me and has been for a few years.

Bill B

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Follow Up By: Member - Odog - Sunday, Nov 30, 2014 at 10:27

Sunday, Nov 30, 2014 at 10:27
Hey Bill,
I find it a bit of a pain, climbing in and out to change the charger from one battery to the other, it's not that much of a hassle , but having to nearly totally remove the boat cover (cats bed) each time... It can be months between use, I thought I might be able to get a smart charger that is basically hard wired to both batteries, and will fully charge and then maintain them between use.
I just had a look at cetk, but looks like one charger for each battery? Which I don't really want to do, maybe like you, I may have a look at solar.. Thanks Bill. Cheers Odog
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Reply By: gbc - Sunday, Nov 30, 2014 at 10:20

Sunday, Nov 30, 2014 at 10:20
You'll need to supply details of how the batteries are currently interconnected. A 50 hp (17a) should pretty much keep up with your power supply needs depending on how much you run around. The start battery should already be hooked up to the alternator on the engine? Yes?
A marine VSR after the first battery connected to some heavy cable up to the bow would control the charging of the second battery.
My boats have generally had manual battery isolators with positions for battery a, battery b or both, so to charge two batteries I'd spin the dial around to both when underway, or when hooked up to a bigger charger.
A vsr makes the process more automatic, but only allows flow in one direction without ignition switching (unless you get something really smart like a ctec 2500) which will mean that charging a deeply discharged deep cycle battery which has been running the leccy motor will mean the vsr clunks in and out for ages and is fairly inefficient. For just keeping them topped off the vsr will do the job perfectly well, but if you aren't charging the deep cycler whilst underway it is going to be pretty hungry by the time you get home.
Spend more money and get a ctec 2500 or other smart isolator which flows both ways and when you get home you just hook up the deep cycle battery to the charger and walk away. Once it is charged it will back charge the start battery as well which is nice. you still have to get a battery charger on top of that for at home. When underway the ctec works the other way round, looking after the start battery first, then the deep cycler when it can.
These units will also handle a solar panel so if away for a while in the boat or leaving at home for a while, the panel will replace an electric charger for all but flat battery duties.
My home charger isn't overly expensive. It is a 5 stage 15 a unit by AC Delco. Cost me maybe $150 at tradetools. I wouldn't want to go much cheaper or smaller than that for booting your batteries at home.
I've tried a few times in the past to save money on this stuff but there really aren't any short cuts to doing it right. I hope this helps?
AnswerID: 542366

Follow Up By: Member - Odog - Sunday, Nov 30, 2014 at 10:45

Sunday, Nov 30, 2014 at 10:45
Thanks gbc.
The start battery is charged off the engine while running, but the trolling battery is totally on its own, we usually head up to jindabyne or eucumbene for day, or weekend trips, get to where we want with the main engine, then troll..
When down the coast, usually only use the main engine, (have a quick release for the minkota, so it stays home) but even then, we launch usually, off an ocean ramp, so don't need to travel to far for a feed.
So both batteries don't get all that much use, except if doing a weekend up the mountains, but work gets in the way, so don't do it as often as we would like.. Last time took the ct instead of the boat.. So the boat spends a lot of the time sitting and waiting.. For retirement.. Lol.. Cheers
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Reply By: swampfox - Sunday, Nov 30, 2014 at 10:35

Sunday, Nov 30, 2014 at 10:35
U could run the dual battery similar to a car.
The best performance would be if both batteries are the same eg century N70M--100ahr,charge the same from the out board depending on its output if any .
A Projecta Procharge [multi stage automatic ] either the 16 amp or the 21 amp
This charger has different battery types and multi outputs
[140- 180 online ]
A deepcycle can either be an AGM or wet cell type . Require different charge profiles
Wet cell 10% of capacity fast charge rate in amps
AGM 20% of capacity fast charge rate
These rates are a guide from century
In reality a 4x4 N70z is ok to be charged at slightly higher rates . A multistage cycles the power down if not needed.
I charge with a matson 24 amp charger

AnswerID: 542368

Follow Up By: Frank P (NSW) - Sunday, Nov 30, 2014 at 10:48

Sunday, Nov 30, 2014 at 10:48
Hi swampfox

Agree with you, except

"A multistage cycles the power down if not needed."

That's not quite right. A multistage will provide its full current until the battery reaches absorption voltage. That full current may be more than the battery should have, so the OP should choose chargers with max amps suitable for each battery.

Once the battery reaches absorption voltage the charger will hold the voltage and the current will taper down until it reaches a certain low level where it changes into float mode. Perhaps that's what you meant.

But as you pointed out, for best life and performance not all batteries can take all the current that a large charger can pump out.


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Follow Up By: swampfox - Sunday, Nov 30, 2014 at 11:16

Sunday, Nov 30, 2014 at 11:16
HI Frank,

Agree with you ,situation may well be based on the charger and the batteries state of charge 90%full .The charger enters diagnosis mode then starts on the typical bulk absorbtion float process etc . Therefore due to its SOC I imagine the charge profile is taillored heavily.
A battery with a reasonable state of discharge will probably be different .

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Reply By: The Bantam - Sunday, Nov 30, 2014 at 11:01

Sunday, Nov 30, 2014 at 11:01
There are a cople of issues.
I assume you want to chage the batteeies with the cover still on the boat whaile it is in the garrage.

I'd be concerned aboiut the ventilation issues, charging batteries ( of any type) in an enclosed space especially over an extended period of time.

That said there are two chagring approaches.

1/ fast turn arround charging to get the trolling motor battery back up to charge for a following days fishing.

2/ maintenance charging bothe batteries while the boat is in storage.

If you want to turn the trolling motor battery arround in as little as 8 hours you will need at least a 15 amp battery charger.

that is ssiue 1/

To maintain a battery over a long idle period you do not need anywhere near as big a charger.
One as small as 3 amps may do the job.

an issue of concern is the long term reliability of multistage chargers.......none of them are smart....nothing like it.....they are dumb as dog ####.......they simply follow a fixed set of charging rules and cycles....AND they can be fooled by a number of circumstances.

I do not recomend long term unsupervised charging with multistage chargers.
You need to be checking on the battery to ensure nothing unhappy has occured.

Now none of thins needs to be very hard.

If a battery is healthy and isolated from all sources of drain, it should maintaine a good state of charge for at least a month if it was properly charged before it was put away

It would be wise to give each battery a bit of a tickle up every couple of weeks.

Many of the multistacge chargers come fitted with a plug at the end of the charging lead, where either a clip tail or a screw down tail is fitted as required.

My recomendation for you is this.
1/ provide some ventilation so that any hydrogen generated can escape from under the boat cover......remember bantams fart rule.....if you farted under there how quickly would the gasses escape.

2/ set up a charging panel at the rear of the boat, where the charger/s could be connected on plugs......the charger cables would remain peremanetly connected to the would also be good to have 1 or 2 voltmeters on this panel so you can see at a glance the condition of the batteries.

3/ buy chargers as you choose....there are many good ones about.

AnswerID: 542370

Reply By: tonysmc - Sunday, Nov 30, 2014 at 11:38

Sunday, Nov 30, 2014 at 11:38

Minn Kota make 2 types of on board battery chargers.
One is DC to DC which is basically the same as a car dual battery system, charging both batteries from the engine alternator, however its waterproof.
And the other type is 240 volt which is mounted in the boat and you plug it in when you get home, which sounds like what you want.
They are quite big and heavy units however they are made for boats and are saltwater protected. I have 4 batteries in my boat and utilise a Redarc dual battery isolator and the Minn Kota DC to DC charger.
The best set up for you IMHO would be an Anderson plug mounted in a place easy to reach going to the main battery and then a Redarc isolator between the main battery and the second battery. This way your second battery is being charged by the motor when running and when you get home you can plug your charger into the Anderson plug and it will charge both batteries. The only issue you can get is if the Redarc is connected to your ignition, because if you turn on the ignition at home you will be clocking up engine hours without the engine actually running. I put in switches to by-pass the ignition at home. I also mounted the Redarc isolator inside a clear Tupperware container to protect it from water.

Cheers Tony
AnswerID: 542374

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