charger questions/recommendation

[ferret30]

Hey brats,

I'm getting close to finished with my shore power install. I want to install a charger now, but I'm having trouble picking one. I'd like to keep the cost under $150, and I'm fine with lower amp models (i.e. 5 amp). The boat has a Blue Sea ACR, so I only need a single output charger.

Some people have mentioned the need for a temperature sensing charger. Does this mean the charger has a probe on the battery, or that the charger is monitoring its own temp? The lower end Guest and Xantrex models I downloaded manuals for didn't appear to show an external lead for temp.

Also, how important is battery temp sensing? Can't a good charger regulate current and voltage?

Here are the ones I'm looking at:

http://www.defender.com/product.jsp?id=131403
http://www.defender.com/product.jsp?id=758332

[Discovery]

Ferret30,

Personally I would shy away from Guest. Get a smart charger that decreases the charge as the battery fills. One that then trickle charges and has the capability to also desulfate with a high charge. I bought a charger that was designed to recharge trolling motor batteries. I bought a Tracker fishing boat in 2002 and bought this type of charger.... 2 bank at 10amps/bank. I keep it plugged in whenever possible, 24/7 if the boat is at home. I have never had to replace the batteries yet. 10+ years and still going on 3 group 31 Interstate batteries. The brand is Dual pro and it was around $200.00. Saved a bunch on batteries I didn't replace.

http://www.batterymart.com/p-dual-pro-se-12-24v-20a-battery-charger-2b.html

Brent

[Robert H. Wilkinson]

Hi Ferret, I would agree with Brent - money spent on a good charger will pay for itself by increasing the life of your battery bank.
Low amperage charging results in "stratification". It does not keep the electrolyte mixed. Ideally the charger should put out an initial "bulk" charge of around 20% of the banks capacity. (a 100amp bat. should get a 20 amp charge to start) That amperage should be maintained untill the voltage reaches around 14.4 volts. Then the amps should taper off while maintaining 14.4 volts for an "absorpion" period of about 2 hours. It should then go into float mode (around 13.2 volts). A float mode above 13.2v will result in fluid loss. A good charger should also be capable of providing an "equalizing" charge (15-15.5v). This feature is normally used about once every 25 charge/discharge cycles. Or every time that the fluid levels are topped up.

The temperature probe comes from the charger and taped(2 sided tape) to the middle of the battery and the middle battery(in a large bank). It adjusts the voltage of the charger to compensate for the temp. of the battery. I havn't seen this on a marine charger - maybe because they are normally only used during the warmer months. My home system does have this probe tho (I have lived "off the grid" since 1979).

A good charger should also be capable of "keeping its cool" while putting out its full rated amperage. This is why most alternators are not designed to charge discharged batteries. They heat up and either burn out or the amperage drops to a fraction of their rated output.

A good charger should also be programable to match it to the battery bank it is charging.

I guess by now I have either helped or totally confused you!!
Anyway----like Brent said, buy a good charger.
Regards, Rob

[Aurelia]

It would be good to know what batteries you need to charge (size) and also how you plan to discharge them and how quickly you need to recharge and by what input (generator, shore power).

These are worth considering with the last one being the smartest and one if my favorite types. I also tend to steer away from guest units but that is based on some older experienced that may be outdated at this point.

The ultimate output of the charger needed may be small depending on your specific situation and the type of charger.

I run a 5 amp model to handle three batteries with total 265AH capacity and it does perfect but there is a 300 dollar DC to DC charger doing important middle man managment of the larger bank.

http://www.batterystuff.com/batteries/promite5.html

http://www.batterystuff.com/battery-chargers/12-volt/marine-chargers/RS1.html

http://smartercharger.com/battery-chargers/#CTEK Multi US 7002 or a smaller unit

[jep111]

I'd like to caution that even with the ACR a single output charger is only appropriate if both batteries are the same type, mfr, age, etc.

While an ACR is a great compromise to split a single outboard's charging to two batteries, it is far from ideal for a starting battery and a deep-cycle house battery, and a terrible choice if those batteries are of different chemistries (e.g., wet-cell and AGM). If your intent is to use the charger for storage/maintenance, a dual-output charger that has independently configured and monitored outputs is far preferable...

Cheers!

John

[Aurelia]

John is right and that is why we need to know what batteries in which configuration to provide the best advice.

Greg

[ferret30]

Both the batteries are Interstate SRM-24, deep cycle/starting, and are the same age (6 months). They are isolated from each other by the Blue Sea battery switch which connects house to house batt and engine to start batt independently, but with one control.

In our case the ACR should be fine for charging from a single source. Our boat is in a marina with power at the dock. For the next few years we are only planning on day cruising and occasional overnight trips, mostly to destinations with power.

If/when we start doing longer trips or anchoring overnight, we will reconsider our setup, but for now I am looking to keep things simple.

Thanks for the input so far!

[thataway]

Some temperature sensors attach to a battery post. Mostly temp sensors are found on larger chargers (for example my RV has a 130 amp charger--which does have a temperature sensor, and a "computer" to control the output, float, bulk etc voltages.

For most boats our size, the 5 /5 works fine. I carry a 30 amp charger which also can charge at lower rates (15/10), and has tempature compensation. plus has a 75 amp boost if necessary for starting. I can use this with the generator for a "quick charge when on the hook for a few days, when not running the engine. Our experience is that even the 16 amp alternator on the Honda 90 (2006--newer ones have alternators in the 47 amp range), was plenty to keep the batteries on the trips we did this summer. We ran the generator once, when at the same place for 5 days--probably not essential, but I always like to keep the battery voltage more than 12.2 volts.

We have found even with longer cruises of 6 weeks, where we may be on the hook for 2 or 3 nights and then one night back at a marina, the 5/5 works fine. If you are doing most day trips, the batteries should be prettily well charged at the end of your trip--and you don't need a big charger.

[Aurelia]

Thanks for the response and I stick with the original recommendations of a smaller unit. I got a multistage 5amp unit for 50 bucks for our current boat and it may not last forever but will be easy to swap out if it fails down the road. The DC to DC charger is more sophisicated and trustwrothy (I hope) to manage the more expensive set of trolling motor batteries with a feed from the starting battery.

It is a day boat so less critical for us.

[jep111]

Hello ferret30,

With the same Interstate batteries, a single charger will work fine, and since you are in the PNW, you can dispense with worrying about temperature sensing. TS is really about compensating for charging due to heat, not cold...

I like the waterproof Battery Tenders, meself... simple, epoxy-potted, intelligent.

Cheers!

John

[ferret30]

[jep111]

[Da Nag]