battery chargers

wet cell derek

The 20 amp Smart Charger or 30 amp Smart Charger will be perfect.

These units have adjustable output.

Projecta have just released a new catalogue with some nice looking chargers but I have not read the specs yet.

Sorry about the quality of the scan. These are due in April.

Repco, K-mart, Etc.

sandman,

The charger i have is for wet cell (lead acid) batteries. It will boost charge to 80% capacity @ 10amps, then automatically switches to float charge, which is @ 2amps until battery is fully charged. It will then only maintain the battery, giving it only what it needs to keep it up to scratch. I suppose you would call it a 2 stage charger, i am not realy sure. It seems like a fair unit, just not sure if it is big enough to put back 30-40 amps a day without running genny for 5 -6 hours. If it works the way i understand, a 10 amp charger should put back in 10 amps per hour shouldnt it. Would these assumptions be true:
1. 150 amp hour bank - daily use of 40amp = 110amphour remaining
2. charger charges @ 10amps upto 80% capacity, in this case is 120amp hour. So if i have 110 amphours left,my charger will charge for one hr @ 10 amps. It will then do the remaining 30ampshours @ 2 amps which would take 15hoursto fill the rest.

if this is right would i be better off
1. getting a bigger charger
2. useing current charger and only charge up untill it hits float. which might mean 4 hours per day of genny running

Freezer,

Wouldn't a larger charger reduce the Bulk charge time [1hr]? It wouldn't affect the Float charge time, looks like 80% is it for DC batts using your intended method[unless you intend to run the the genny for yonks!]

eng

I wouldn't wast my money on a fancy charger. Just go for the one with the most raw grunt i.e. a 20 amp job. You're not likely to run the genni for long enough to have all the fancy modes (i.e. equalize, float charge) activate. That is if you only want to use it for camping. If you also want to use it at home, different story. You may still be better off buying a lower current "fancy" one and just a "raw" high current one for use with the genni.
Cheers

Hi Freezer, before you spend another cent, just try what you have and see if it works for your needs.

If you have a problem, then look for a solution but I think you will find the charger you have will be more than adequate for most of your requirements, as you posted in the other thread, so until try it out and you know if you actually need anything else.

Cheers

Sandman, that BM140 you mentioned - is it effectively a 3 stage charger? I saw one in Kmart but there wasn't enough info for me to figure this out. I just cooked a Trojan leaving it on a basic charger and I'm a bit sensitive about stuffing another battery but I don't want to spend $300 on a fancy 3 stage charger if I don't need to.

"If it works the way i understand, a 10 amp charger should put back in 10 amps per hour shouldnt it."

Yes, charging time is usually determined by charging current, but -

- if it is a Wetcell Deepcycle, you should keep charging currnet to less than C/4 (150/4= 37amps in your case) for long batttery life.

- the battery's ability to accept charge will reduce as it aproaches full charge.

- btw - it's 10 amphours per hour of charging

So if you are taking 40 amphours out of the battery every night, then yes, you will reduce charging time by increasing your charging ability to 20 or 30 amps.

WOK

yes 80 % charge would be the most you would bother with on the 10 amp charger i have already. The first night would be a quick 1 hr charge and from then on in it would be 4 hours. Might be worth getting the 20 amp and cutting this time in half.

Nifty1,

The BM140 utilises a 2 stage charging algorithym to first "bulk charge" a battery then maintain a float charge.

Hi Freezer, unfortunately doubling the size of the charger won’t half the charging time. It will probably speed it up a little.

Not knowing your batteries, I haven’t the exact charge slop figures for you but a very rough slop will still give you some idea.

Wet cell batteries will not charge as quickly as other types of batteries so the charge time is going to be slow even if you put a large capacity charger on them.

During the first hour or so, depending on the output current AND VOLTAGE of the charger, and the state of discharge of the batteries, the batteries will probably take everything that your present charger will put out but after this initial stage, the charge being absorbed by the batteries will taper off over a period of hours and it wouldn’t matter if you had a 1,000 amp charger, your batteries will rule how much current they require.

So having a larger charger will help in the first hour or so but the rest of the time the batteries will draw less and less.

Again, as posted above, save your money for now and try using what you already have and see if there is any real short fall.

Cheers

BTW Freezer, if you do a google search and find the manufactures web site for your batteries, you will most likely find the exact charge slop for your batteries.

Cheers

call me stupid but what is is "slop"
freezer

Hi Freezer, I will not call you stupid because it’s a fair question.

Basically the charge slop is a graph ( and this may sound like double dutch ) that sets out the amount of current that the battery of a given size can absorb based on the start of charge of the battery and the charging voltage being applied at a given temperature.

Now that should make a lot of sense NOT!

The best way to find out about the charge slop for your batteries is as I posted, to go to the web site for your brand of battery.

Once you look at the slop all you need to do is get a rough idea of how your battery is going to charge and this can give you some idea of whether you need a bigger charger or that the charger you have will be fine.

Remember, these graphs are based on results gained in laboratory conditions, using new batteries for the tests and only have a slim resemblance to what happens in real life, so just view them as a guide.

Cheers

Geoff - I agree, if you have a 10 amp charger and the fridge draws 5 amps (most probably worst case), you will get much faster charging if you power the fridge off 240 volts rather than 12 volts.

Mike