TiggerToo
Well-Known Member
What is better (all other things being equal):
one battery rated at 200Ah, or two batteries in parallel rated 100Ah each?
one battery rated at 200Ah, or two batteries in parallel rated 100Ah each?
Better Batteries
- Thread starter TiggerToo
- Start date
Refueler
Well-Known Member
Personally two ... if one goes down - cheaper to replace ..
sailorman
Well-Known Member
& easier to handle
a 110Ah is 30 kg
a 110Ah is 30 kg
Ruffles
Well-Known Member
Forget plates and electrolytes. The most important part of 110Ah batteries is the carrying handle. Especially if the boats on the hard and you've got to take them home.
sailorman
Well-Known Member
/forums/images/graemlins/laugh.gif
i have just changed 4 of them /forums/images/graemlins/blush.gif
i have just changed 4 of them /forums/images/graemlins/blush.gif
AIDY
Well-Known Member
Sorry your wrong /forums/images/graemlins/grin.gif most important thing about the battery is will it keep SWMBO fridge cold 24/7. It's more important than running navigational equipment and nav light /forums/images/graemlins/laugh.gif
William_H
Well-Known Member
So the weight really dictates the max size of battery. You can get 2x100AH 12v in parallel or 2x6v 200AH in series.
I think I would go for the 2x6v in series. You can still replace one if necessary.
Batteries in parallel can present problems in that a dud cell will reduce the voltage of the battery which if wired in parallel will then pull down the voltage of the other ie discharge it. For the most part parallel batteries seem to work OK but they must fail eventually and this is where the whole bank will come down unless you divide the batteries and treat as individuals. IMHO
Ultimately it is probably a question of price and the 12v would be cheaper being more popular in vehicles. Check around. good luck olewill
I think I would go for the 2x6v in series. You can still replace one if necessary.
Batteries in parallel can present problems in that a dud cell will reduce the voltage of the battery which if wired in parallel will then pull down the voltage of the other ie discharge it. For the most part parallel batteries seem to work OK but they must fail eventually and this is where the whole bank will come down unless you divide the batteries and treat as individuals. IMHO
Ultimately it is probably a question of price and the 12v would be cheaper being more popular in vehicles. Check around. good luck olewill
A
Anonymous
Guest
[ QUOTE ]
Batteries in parallel can present problems in that a dud cell will reduce the voltage of the battery which if wired in parallel will then pull down the voltage of the other ie discharge it............ they must fail eventually and this is where the whole bank will come down unless you divide the batteries and treat as individuals.
[/ QUOTE ]The same applies to batteries in series, of course. As you say, two banks is the safest way. I had two large 220Ah Sonnenschiens wired in parallel and noticed from the ammeter that the charge wasn't falling off....stayed up at 10A or so. When I looked at the batteries I found that one of them was very hot to touch. Had to physically disconnect it with a spanner.
Batteries in parallel can present problems in that a dud cell will reduce the voltage of the battery which if wired in parallel will then pull down the voltage of the other ie discharge it............ they must fail eventually and this is where the whole bank will come down unless you divide the batteries and treat as individuals.
[/ QUOTE ]The same applies to batteries in series, of course. As you say, two banks is the safest way. I had two large 220Ah Sonnenschiens wired in parallel and noticed from the ammeter that the charge wasn't falling off....stayed up at 10A or so. When I looked at the batteries I found that one of them was very hot to touch. Had to physically disconnect it with a spanner.
Teetime
Active Member
I am surprised that some expert has not told you tiggertoo that 2 100 amp batteries have a higher useable capacity than one 200 amp battery. There is a technical reason for this something I think to do with Peukarts (spelling?) law. Not easy to understand but I am pretty sure that 2 100 amp batteries in parallel have a capacity of 220 amps.
pvb
Well-Known Member
[ QUOTE ]
I am surprised that some expert has not told you tiggertoo that 2 100 amp batteries have a higher useable capacity than one 200 amp battery. There is a technical reason for this something I think to do with Peukarts (spelling?) law. Not easy to understand but I am pretty sure that 2 100 amp batteries in parallel have a capacity of 220 amps.
[/ QUOTE ]Don't know who told you that, but it isn't true!
I am surprised that some expert has not told you tiggertoo that 2 100 amp batteries have a higher useable capacity than one 200 amp battery. There is a technical reason for this something I think to do with Peukarts (spelling?) law. Not easy to understand but I am pretty sure that 2 100 amp batteries in parallel have a capacity of 220 amps.
[/ QUOTE ]Don't know who told you that, but it isn't true!
aluijten
Well-Known Member
Actually it can be true...
The capacity of a battery is always expressed at a certain discharge rate depending on the capacity of the battery. The Peukert function tells you that a battery has less capacity when discharged at a higher rate. By using two batteries in parallel you reduce the current for each battery. As the Peukert relation is not linear this might actually lead to a longer discharge time compared to the single battery with double capacity. I'm not sure if you will find the difference noteworthy in practice
Arno
The capacity of a battery is always expressed at a certain discharge rate depending on the capacity of the battery. The Peukert function tells you that a battery has less capacity when discharged at a higher rate. By using two batteries in parallel you reduce the current for each battery. As the Peukert relation is not linear this might actually lead to a longer discharge time compared to the single battery with double capacity. I'm not sure if you will find the difference noteworthy in practice
Arno
pvb
Well-Known Member
No, it isn't true. Batteries are rated at a "20hr rate", so a 100Ah battery will theoretically deliver 5A for 20hrs. Similarly, a 200Ah battery will theoretically deliver 10A for 20hrs. Let's assume someone has a 200Ah battery which they discharge at 10A and find it lasts 20hrs. If they replace that battery with 2 x 100Ah batteries in parallel, and apply the same 10A discharge, each battery will deliver 5A, and will last 20hrs.
If you discharge a battery at a lower rate than its 20hr rate, its theoretical capacity will increase - but this applies equally to a 200Ah battery as it does to a pair of 100Ah batteries.
If you discharge a battery at a lower rate than its 20hr rate, its theoretical capacity will increase - but this applies equally to a 200Ah battery as it does to a pair of 100Ah batteries.
aluijten
Well-Known Member
I stand corrected /forums/images/graemlins/grin.gif