Charging a whole bank in 8hrs

[DeanS]

Hello

If I ran a gennie, and wanted to charge one battery to 100% it could take 8hrs.

If I want to charge 6 batteries to 100%, should I connect 3 chargers, each going to 2 batteries.

Will this speed up the charging process overall, ending up with the batts having a larger individual charge than trying to connect a single charger to all 6 over an 8 hr period. Basically I have a gennie, and want to charge all 6 batts as much as possible over an 8hr period. My charger is only sized for 220AH batteries....but if I had 3 small chargers, I could do it.

 

Please dont tell me to buy a big charger. Got no cash. Just bought gennie. Easier to buy another small charger for now (which will give me 2) and another next month (which will give me 3). Gennie is 2.8kw

 

Alternatively, what will happen if I just connect the 12V output from the gennie onto all 6 batts for a few hours?

 

Thx.

 

 

[bizzard]

Hello

If I ran a gennie, and wanted to charge one battery to 100% it could take 8hrs.

If I want to charge 6 batteries to 100%, should I connect 3 chargers, each going to 2 batteries.

Will this speed up the charging process overall, ending up with the batts having a larger individual charge than trying to connect a single charger to all 6 over an 8 hr period. Basically I have a gennie, and want to charge all 6 batts as much as possible over an 8hr period. My charger is only sized for 220AH batteries....but if I had 3 small chargers, I could do it.

 

Please dont tell me to buy a big charger. Got no cash. Just bought gennie. Easier to buy another small charger for now (which will give me 2) and another next month (which will give me 3). Gennie is 2.8kw

 

Alternatively, what will happen if I just connect the 12V output from the gennie onto all 6 batts for a few hours?

 

Thx.

I think you would need to disconnect the batteries and connect them into 3 separate pairs to do this otherwise why not.

 

Charging the whole bank with your boat would be forbidden under Cart regs, it makes big V shaped dents in it and it would disturb all the wildlife living in it.

Edited April 12, 2013 by bizzard

[bottle]

Hello

If I ran a gennie, and wanted to charge one battery to 100% it could take 8hrs.

If I want to charge 6 batteries to 100%, should I connect 3 chargers, each going to 2 batteries.

Will this speed up the charging process overall, ending up with the batts having a larger individual charge than trying to connect a single charger to all 6 over an 8 hr period. Basically I have a gennie, and want to charge all 6 batts as much as possible over an 8hr period. My charger is only sized for 220AH batteries....but if I had 3 small chargers, I could do it.

 

Please dont tell me to buy a big charger. Got no cash. Just bought gennie. Easier to buy another small charger for now (which will give me 2) and another next month (which will give me 3). Gennie is 2.8kw

 

Alternatively, what will happen if I just connect the 12V output from the gennie onto all 6 batts for a few hours?

 

Thx.

 

 

Zilch (technical term ) for almost nothing, the output on the generator is not for charging batteries, it is for running 12v dc equipment up to the amperage of the output.

 

You could use more than one charger but the bank would have to be split, I would still like to know how your charger knows the size of the bank it is charging.

 

I am sure you have been directed here before What size charger

[Chris Pink]

Hello

If I ran a gennie, and wanted to charge one battery to 100% it could take 8hrs.

If I want to charge 6 batteries to 100%, should I connect 3 chargers, each going to 2 batteries.

Will this speed up the charging process overall, ending up with the batts having a larger individual charge than trying to connect a single charger to all 6 over an 8 hr period. Basically I have a gennie, and want to charge all 6 batts as much as possible over an 8hr period. My charger is only sized for 220AH batteries....but if I had 3 small chargers, I could do it.

 

Please dont tell me to buy a big charger. Got no cash. Just bought gennie. Easier to buy another small charger for now (which will give me 2) and another next month (which will give me 3). Gennie is 2.8kw

 

Alternatively, what will happen if I just connect the 12V output from the gennie onto all 6 batts for a few hours?

 

Thx.

 

This has been covered many many times. There is no shortcut, 15 gennies, 15 chargers will still take 8 hours to get to 100% (whatever you decide that means).

 

What you can do by upping the capacity of the chargers is cut down the time to around 80%, the bulk stage.

 

The absorption stage will take however long it takes no matter how big your charger.

 

There is no difference between having 2 20A chargers or 1 40A charger except that 2 20A chargers are likely to be cheaper than a 40A one.

 

Alternatively there is an argument for splitting your bank into 2 and using one while the other, over a period of days, is charged to 100% and the one in use is charged to 80% each day. This is mooted as being the most economical way to use batteries when you factor in battery cost.

[nb Innisfree]

 

Alternatively there is an argument for splitting your bank into 2 and using one while the other, over a period of days, is charged to 100% and the one in use is charged to 80% each day. This is mooted as being the most economical way to use batteries when you factor in battery cost.

Need to consider that the bank in use is only half as big as it was so gets heavier use and therefore has a shorter life.

 

But I think you already know that.

[smileypete]

Might be best to try to schedule together and run big mains loads off the gennie directly, and while doing so use whatever charger you have to charge the batts as much as poss.

 

You can certainly use chargers in parallel, up to the power limit of the gennie, but the smaller <=1kW gennies can't power much in the way of charger load. And the small car type chargers probably won't offer good value in terms of cost vs amps output.

 

ETA: I think a few people have one of these, and it should be OK on all but the smallest gennies.

 

http://www.ebay.co.uk/itm/130839531150

 

ETA2: This supply should do the same job, for half the £, but it's supplied from Asia and a lot less user friendly to connect up:

 

http://www.ebay.co.uk/itm/380618776577

 

cheers, Pete.

~smpt~.

Edited April 12, 2013 by smileypete

[smileypete]

Need to consider that the bank in use is only half as big as it was so gets heavier use and therefore has a shorter life.

 

But I think you already know that.

 

By using DC-DC converters and picking a light use day, I think you could get half the bank fully charged and equalised in 6-8 hrs without too much impact on the other half, before connecting both halves of the bank back together.

 

The only other options AFAIK are running genny or engine for ages, or having a big solar array and waiting for a nice sunny day.

 

cheers, Pete.

~smpt~

[Chris Pink]

Need to consider that the bank in use is only half as big as it was so gets heavier use and therefore has a shorter life.

 

But I think you already know that.

Examination of cycles versus DOD for traction batteries show there's not much economic benefit in running to 30% SOC over 50% SOC and given that batteries are only storage, ie power out has to equal power in, so certainly with traction batteries I think running them hard in two banks one on slow recharge to 100%, one on fast 80% charge is likely the most economic way to run an off grid system.

 

Though with cheapo batteries you are probably right.

[DeanS]

so if I have a 2.8kW gennie...and I split the bank into 2...and run a charger on each.....then at the end of the day, I would have more battery charging done, than running a single charger on the entire bank. Is that correct? Logic would seem to say yes.

 

My charger has a limit written on the back...which may relate to the length of time it can run at max amps before getting too hot etc.. Also...it would make a lotta sense to me to run 6 chargers on 6 batteries for 8hrs, and walk away with 6 fully charged batts.....but the gennie probably wouldnt cope

 

Regarding the question about connecting the gennie 12V to charge batteries...I only asked because the gennie actually says ..."for recharging batteries"....but we all know that you need more than 12V to charge batts, so I didnt give it much real consideration.

[Chris Pink]

Your logic may say yes, physics he say no.

 

Go back and read my earlier post.

 

This question, unsurprisingly, comes up again and again. Why can't I get a trillion amp charger and charge in 10 seconds?

 

The answer is the same. It's the battery that determines the rate of charge not the charger.

 

Asking the same question one more time just ain't going to change the laws of physics.

[Arthur Brown]

Depending on their resting state of charge, you should be able to get a significant improvement in the bulk charge in two hours BUT the absorbtion and float charge sectors are critically long time low amps sectors.

 

Multiple chargers will assist charging separated batteries, but it's not certain how they would react given a connected bank.

 

Adding load (chargers) gradually could be good for the generator as some generators will not take a step load being applied.

 

It's likely that your engine alternator has a good charging profile for the batteries -maybe better than a cheap charger.

 

The 12v output on most alternators is poorly regulated and very small in power, usually it works for recharging a small starter battery for the generator's engine. It's power input into your bank is insignificant..

Edited April 13, 2013 by Arthur Brown

[smileypete]

Just a thought, if you have a high power alt and 600Ah bank and say a 30A charger, why not run the eng until charge current drops to 30A then if you want to do a FULL charge run the genny for longer until it drops to 12A.

 

You don't need to do a full charge each and every day, but at least once a week seems to work best for most liveaboards. Forget the split bank thing for now. The charge output from the gennie is likely to be just a few amps for topping up a start batt.

 

cheers, Pete.

~smpt~

[DeanS]

I think I might not have explained myself clearly.

 

My question was...by splitting a battery bank into 2 for example, and using 2 battery chargers...1 for each....would this not achieve more within a certain time period, than not splitting them, and using a single charger.

[bizzard]

I think I might not have explained myself clearly.

 

My question was...by splitting a battery bank into 2 for example, and using 2 battery chargers...1 for each....would this not achieve more within a certain time period, than not splitting them, and using a single charger.

I understood Dean. 2 or three cheap chargers would probably be a lot cheaper than one big super dooper highly expensive one but I would expect the charging times would be similar.

[smileypete]

so if I have a 2.8kW gennie...and I split the bank into 2...and run a charger on each.....then at the end of the day, I would have more battery charging done, than running a single charger on the entire bank. Is that correct? Logic would seem to say yes.

 

Yes, but only from having 2 chargers instead of 1; you'd get just as good a result running both chargers on the one unsplit bank.

 

cheers, Pete.

~smpt~

Edited April 13, 2013 by smileypete

[dmr]

OK Dean.

Charging your batteries is a bit like a barmaid serving up some pints of Guiness.

If the tap works quickly then the firstt half of the glass will fill quite quickly, but then it gets that head on it and getting the last 20% into the glass takes forever, no matter how many bar staff are working on it, and no matter how many pints are lined up, it takes just as long to get that last 20% in.

 

.............Dave

[Taslim]

OK Dean.

Charging your batteries is a bit like a barmaid serving up some pints of Guiness.

If the tap works quickly then the firstt half of the glass will fill quite quickly, but then it gets that head on it and getting the last 20% into the glass takes forever, no matter how many bar staff are working on it, and no matter how many pints are lined up, it takes just as long to get that last 20% in.

 

.............Dave

Wonderfully put.

[jelunga]

OK Dean.

Charging your batteries is a bit like a barmaid serving up some pints of Guiness.

If the tap works quickly then the firstt half of the glass will fill quite quickly, but then it gets that head on it and getting the last 20% into the glass takes forever, no matter how many bar staff are working on it, and no matter how many pints are lined up, it takes just as long to get that last 20% in.

 

.............Dave

Super analogy. If I knew how to give you a Greenie from my iPod I would ....

[Peter Reed]

Super analogy. If I knew how to give you a Greenie from my iPod I would ....

I have happily given him one of my greenies in your stead.

[sueb]

I hope I never moor near you. I've run my engine for two hours for the first time for a fortnight. Electricity is over rated on boats.