TheSamba.com :: View topic - Guest 6 amp Battery Charger

Thu Dec 06, 2012 1:10 am

Going to run a single aux battery bank. Is this charger ok? http://www.marinco.com/product/6-amp-single-battery-chargepro-charger It has some nice reviews, has a small footprint, and seems to fit the bill. However...

I was reading the spec sheet and it listed the maximum recommended amp hours of the battery at 72 AH. I plan on either installing a Trojan 105 AH or 225 AH system, so I am exceeding what's recommended. Is this OK? I don't need the 10 amp dual bank charger, and I don't really want to spend the extra dough on a larger system. I don't plan on plugging into shore power much, but want the option.

Any advice appreciated.

Thu Dec 06, 2012 2:52 am

It'll work just fine - it'll just take a bit longer to charge the battery up.

Simply, if you're charging at 6A, it'll take 12hrs to fully charge a 72Ah battery from pancake, and 20hrs to charge 120Ah. Not that quite simple, since an intelligent charger adjusts the charge rate to suit the battery, and you won't (or shouldn't...) ever take the battery anywhere near flat.

Apart from charge time, the only other thing you might want to consider is "gaining on it" - if you're using 7A, but charging at 6A, then you'll be discharging the battery slowly, not charging it, whilst a 10A charger would have enough headroom to still put 3A towards charging.

Thu Dec 06, 2012 8:05 am

6 amp should work just fine. When do you see yourself needing a faster charge when you're plugged into shore power anyway? The rest of the time you're driving right? That should be able to give your battery a good charge in an overnight situation.

Thu Dec 06, 2012 9:11 am

That's what I thought, but with electrical stuff, my head sometimes explodes. Thanks for the advice.

Thu Dec 06, 2012 9:22 am

BetaVan wrote: That's what I thought, but with electrical stuff, my head sometimes explodes. Thanks for the advice.
Yeah.. PDXWesty has it right.
An onboard charger is just compensating for on board electrical use.
So you really only need to replace charge for what is spent running lights, laptops etc. WHILE plugged into shore power.
Otherwise, the charger should just be trickle charging.. like in the case where you have it parked in your garage between trips.

As noted.. your starter battery is isolated (should be in a system like what you are creating).. and in worse case scenario, you start your engine and the alternator now charges the enitre bank.

Unless someon makes a mistake and leaves an appliance on.. you'd seldom be charging a dead battery.
6 amps should be fine. And you can always upgrade to 10 later.. or more even.

Thu Dec 06, 2012 9:30 am

:bay_blue: Well all I can say is I have a 140 watt solar panel 7 amps and it will keep both batteries charged and run my TF 49. So 6 amps from any place should do the job. :D

Thu Dec 06, 2012 9:53 am

I have that charger. I installed it last winter and I use it often, I really like it.

I bolted it to the metal on the drivers side of my engine compartment, down low. I ran the charge output wire to my alternator and the AC plug wire is routed to the license plate door. It's the easiest way to go. It works well with my sure power 1314 separator, charging both batteries just like the alternator does.

I use it to top off my batteries all the time. I also use it when I pack up the edgestar fridge the night before a camping trip.

It's so easy, I just fold down the license plate and plug in an extension cord from an exterior outlet on my house. You can leave it plugged in as long as you want without worry because its a smart charger.

Thu Dec 06, 2012 10:27 am

Thanks for all the sage advice. I am in the process of gathering all the parts needed to build my aux battery system. I am starting from scratch, and want to do everything to a pretty high standard while keeping the install neat and clean. I'm shooting for something as clean as PDXWesty's, but doubt it will compare.

Thu Dec 06, 2012 11:25 am

That charger will no doubt work with enough time.

But, most battery manufacturers have a prescribed method for best recharging their battery for maximum performance and longevity.

These recommendations are not easy to adhere to 95% of the time.

For Example Crown says to recharge their batteries at 12 to 18 amps per 100 amp hour of battery.

I just yelled at my alternator and other charging sources and showed them this PDF:

http://lib.store.yahoo.net/lib/wind-sun/Crown-safety-first.pdf

I doubt they listened.

I'd personally go with a higher amp charger, just because I notice that my batteries perform better overnight when the initial charging currents are higher. Like if I drive early in the morning, my alternator feeds 230 amp hours of batteries with 54 to 90 amps for the first few miles, and then after engine shutdown, the solar can take over and top them off, they then hold more voltage the next night than if I did not drive and just let the solar slowly bring them to full and then top them off later in the day.

Battery recharging is kind of a 'whenever you can' type of thing. Many times I've had super low batteries, and only an hour to plug in to charge. My two chargers and solar are capable of close to 40 amps, and after an hour, when I start the van, the alternator goes right up to 50+ amps and only slowly tapers as the voltage rises to 14.5, then the amps taper to the low teens to hold that voltage.

My point is healthy depleted batteries are thirsty devils and it is good to quickly quench their thirst when the opportunities arise. If they do not get too thirsty then a small charger should be fine, but if they are thirsty and your time with grid power is limited, then a 25 amp or higher charger will quench their thirst better and possibly later take some strain from the alternator.

Many state that slow charging is best, and this is a fact, but it is worse for a battery to spend time undercharged than it is to be charged quickly to the above 80% threshhold, in my opinion.

I am going to replace my two grid powered chargers totaling 33 amps with a 55 or 60 amp converter/charger like Iota 55 or Progressive Dynamics pd9260. Only rarely will these ever be required to output their max amperage, but I want that capability for my usage.

Also the cooling fans should be silent overnight when powering my fridge and mattress heating pad and charging the batteries.

Thu Dec 06, 2012 12:20 pm

I should mention that the guest 6a isn't my only charger. I use a die hard platinum charger to recover from deep discharges or condition my house battery periodically. The 6a built in is just to maintain charge or replace what my fridge or furnace are using. Plus, it's built in so I always have it when I need a charge.

http://www.sears.com/diehard-platinum-microprocess...ockType=G2

Thu Dec 06, 2012 12:28 pm

Thanks for all the great response everyone. I drive my van almost everyday, and when I set the system up with Yandina, my aux system will stay topped off quite regularly. I will most likely add solar in the future, but I'll wait on that for a bit. Weekends are going to be the longest I'll be away for the time being (1st baby due in February), and I am sure my house bank will allow for my current needs (no pun intended!). From past experience, when I park and camp somewhere where there is power, I am plugged in for more than 12 hours, so I think any extra capacity will be wasted in the end. Plus, I love how compact the 6 amp Guest is, and it has pretty good reviews. To boot, if it fails out of warranty down the line, I am not out a couple hundred.

Thu Dec 06, 2012 12:35 pm

nocreditnodebt wrote:
For Example Crown says to recharge their batteries at 12 to 18 amps per 100 amp hour of battery.

my alternator feeds 230 amp hours of batteries

I am going to replace my two grid powered chargers totaling 33 amps with a 55 or 60 amp converter/charger like Iota 55 or Progressive Dynamics pd9260.

You're talking about a motorhome sized system with these kind of specs and equipment. For most of us with only one extra battery, we don't need anything near that big. The Guest 6 amp is really fine.

Thu Dec 06, 2012 12:55 pm

IrideWheelies wrote: I should mention that the guest 6a isn't my only charger. I use a die hard platinum charger to recover from deep discharges or condition my house battery periodically. The 6a built in is just to maintain charge or replace what my fridge or furnace are using. Plus, it's built in so I always have it when I need a charge.

Why not just fit a built-in that'll condition? Our Ctek (5amp) does - and Ctek's site "recommends" it up to 110Ah or 160Ah for maintenance.