2 banks of batteries or just 1 big one?

[Ben Plant]

Hi All,

First off apologies if this is already covered but every search I do keeps freaking the forum out, producing no results and instigating flood control.

 

Apart from that its going very well.

 

I've just bought 4 x 230AH 12v Monolith Semi traction Batteries. I intend to eventually hook up Solar power and I intend to get a smart alternator regulator, probably the alternator regulator first.

 

Something like this:

http://www.shop.sterling-power.com/acatalog/ProSplitR.pdf

 

Solar panel wise I hope to get 2 x290W panels with a 60A MPPT controller.

 

Am I better off having 2 banks of 2 x 230AH 12v Batteries or 1 bank of 4 batteries.

 

Everything on the boat is run off 12V. i have an inverter but don't would only have to use it once in a blue moon.

 

I had originally thought of having 2 banks. the first for essentials and the second for luxuries.

 

Essentials:

Bilge Pump

Water Pump

Shower Pump

2 x 12V lights

Headlight

Horn

 

Luxuries:

12V Fridge (in summer)

12V TV

laptop via 12v car charger

USB Phone Charging

Car Stereo, Amp and Sub

Additional Lighting

 

Having 2 banks I feel like I can run down my luxury bank without worrying about whether I can have a shower in the morning, but another mate suggested that with a big enough bank I'd be less likely to run out in the first place.

 

Another suggestion was that having a fall back system is always good on a boat, maybe i should just put both banks on one of those big switches that lets you use 1,2 or both.

 

I've a sneaking suspicion I've just answered my own question, but I've typed it now so never mind

 

Any thoughts would be much appreciated, particularly a link to a wiring diagram for 3 banks (Starter battery is a 110AH sealed battery), a 12v switch, a 3 output alternator regulator and an mppt controller.

 

Cheers,

 

Ben

Heron

 

[by'eck]

Your mate is right - just one bank will maximise use of batteries.

[ditchcrawler]

I think the general wisdom that has come out on here in the past is that one large bank is more efficient than 2 smaller ones

[OldGoat]

Two points to note:-

1. Don't over complicate matters - you'll always get it wrong.

2. If you have two banks of batteries you have the challenge of:-

a. distributing the loads sensibly - especially as the demands will vary from season to season (etc)

b. How do you ensure that both batteries are kept charged a 1 - 2 switch is really intended for a domestic and starter banks (IMHO). You may forget to use the switch.

 

Always remember the KISS principle - use 1. above.

 

[Keeping Up]

Definitely one bank rather than two smaller ones. Try searching this site (or elsewhere) for "Peukert" for the explanation.

[nb Innisfree]

Because of the Peukert effect amphour consumption with one bank will be more than double than that bank divided into two.

[OldGoat]

Peukert?

That's a bit abstruse isn't it?

After all the OP hasn't mentioned anything about actually measuring his consumption and recharge cycles?

 

Very few battery management reporting systems actually use the-aforementioned-gentleman's exponent do they?

 

Mine does (fnar fnar) but too complicated for my battery setup.

 

Just interested; not seeking to create an argument.

[nb Innisfree]

Peukert?

That's a bit abstruse isn't it?

After all the OP hasn't mentioned anything about actually measuring his consumption and recharge cycles?

 

Very few battery management reporting systems actually use the-aforementioned-gentleman's exponent do they?

 

Mine does (fnar fnar) but too complicated for my battery setup.

 

Just interested; not seeking to create an argument.

Well Peukert effect is there whether we like it or not, wish it wasn't, it would make life simpler. Just pointing out the effect on capacity by dividing a bank, up to the OP how he uses that info.

[Guest]

http://www.smartgauge.co.uk/splitting.html

[Tony Brooks]

Peukert?

That's a bit abstruse isn't it?

After all the OP hasn't mentioned anything about actually measuring his consumption and recharge cycles?

 

Very few battery management reporting systems actually use the-aforementioned-gentleman's exponent do they?

 

Mine does (fnar fnar) but too complicated for my battery setup.

 

Just interested; not seeking to create an argument.

 

 

It's Peukert who showed that a high rate of discharge on a given bank size will result in less Ah being delivered that if it was a small discharge. What it means in practise is that a large bank will give more effective Ah capacity at any given load than a smaller bank. So one large bank at whatever the discharge is will maintain its state of charge longer than a smaller bank in Ah terms.

 

This is getting confusing because logic says that a small load will discharge a battery more slowly than a large load but that is not what I am trying to say. A 100Ah battery discharged at 1 amp will deliver that one amp for more than 100 hours where as a 100 amp discharge will be delivered for less than 1 hour to the same level of discharge.

 

There could be a case for two separate banks if one bank was dedicated to feed an absolutely vital piece of kit like (say) some medical equipment but if a piece of equipment just failing to operate will only be an inconvenience then its one large bank every time. However you do need to get the charging right.

[Ex- Member]

I was recently tempted to have a 2 engine batteries in parallel for the engine so we would always have some back up power in an emergency for the boat. I was going to rig the pair so we could isolate one to use for the boat leaving a fully charged one for engine.

 

At the end of the day though it's easier to switch stuff off like fridge & TV than spend time and money on back up batteries. Now having been on the water for just under 2 months though, we've really had no power issues at all, with a 700 amp B/B and 500w of solar, we've only needed to charge batteries using engine or generator fo 5 hours. We've just had 2 pretty sunny days as well and batteries are again fully charged and we're in float mode.

 

A single bank is definitely the way especially at the right size for your needs and a decent input from solar.

 

It's my opinion that solar needs to be around 10% of your your B/Banks amps into solar watts. So our 700 amp bank will be getting 740 watts, just over 10%. We're pretty sure now that 740w will almost definitely supply all of our power needs from all March to end October.

 

As mentioned this 3rd panel will go up by this weekend and will be be able to tilt fully to any low winter sun, so how much we'll glean will be very interesting.

 

Of course this relates to our usage, but to give an idea here's a list of our day to day usage.

 

A+ Washing machine Once a week

A+ rated fridge 240v 24/7

Hand blender 240v occasionally

Dab Radio 12 or 240v few hours a day

32" LED TV 3 hours per day

2 x lap tops one all day other 6 hours per day.

30 LED bulbs av 4 running at a time.

Oven fan + occasional 1 amp

other boat fans 1 amp 24/7

Central heating pump 240v winter only

Charging of numerous items, batteries phones, Nintendo DS, torches.

 

Solar power is the Dogs Wosnames

 

OHHH forgot the usual water pump shower pump LOL

Edited October 9, 2013 by Julynian

[OldGoat]

Ah; nb Innisfree and Tony Brooks - I'm obliged to you both!

 

I was thinking about Peukert's Exponent - have to put more in than you get out, rather than his effect - batteries are more efficient at lower rates of discharge.

 

Now I understand the reference

 

 

[ditchcrawler]

I was recently tempted to have a 2 engine batteries in parallel for the engine so we would always have some back up power in an emergency for the boat. I was going to rig the pair so we could isolate one to use for the boat leaving a fully charged one for engine.

 

At the end of the day though it's easier to switch stuff off like fridge & TV than spend time and money on back up batteries. Now having been on the water for just under 2 months though, we've really had no power issues at all, with a 700 amp B/B and 500w of solar, we've only needed to charge batteries using engine or generator fo 5 hours. We've just had 2 pretty sunny days as well and batteries are again fully charged and we're in float mode.

 

A single bank is definitely the way especially at the right size for your needs and a decent input from solar.

 

It's my opinion that solar needs to be around 10% of your your B/Banks amps into solar watts. So our 700 amp bank will be getting 740 watts, just over 10%. We're pretty sure now that 740w will almost definitely supply all of our power needs from all March to end October.

 

As mentioned this 3rd panel will go up by this weekend and will be be able to tilt fully to any low winter sun, so how much we'll glean will be very interesting.

 

Of course this relates to our usage, but to give an idea here's a list of our day to day usage.

 

A+ Washing machine Once a week

A+ rated fridge 240v 24/7

Hand blender 240v occasionally

Dab Radio 12 or 240v few hours a day

32" LED TV 3 hours per day

2 x lap tops one all day other 6 hours per day.

30 LED bulbs av 4 running at a time.

Oven fan + occasional 1 amp

other boat fans 1 amp 24/7

Central heating pump 240v winter only

Charging of numerous items, batteries phones, Nintendo DS, torches.

 

Solar power is the Dogs Wosnames

 

OHHH forgot the usual water pump shower pump LOL

I cant see you doing that lot on 60ah/day especially in the winter with the pump on unless its one of those fancy very low wattage ones. Do you think you will get enough solar power in a couple of months time?

[Hawkmoth]

Can I hijack this discussion please.

I've just about got my head around all the in and outs of batteries, most of it gleaned from this forum.

For historical reasons we have two domestic banks. One is 6 full traction cells, giving 900 amp/hr @c5. The other is 440 amp/hr of Lifeline AGM.

As the experts on here will know, the charging routine is different for the different batteries. Because of this I charge the tractions from the combi and the Lifelines from the 12V alternator, with a Sterling controller.

After that ramble, what I would like to know is, can I link the two banks using my 1-2-both switch or is that a no no?

Cheers

Bob

[Ex- Member]

I cant see you doing that lot on 60ah/day especially in the winter with the pump on unless its one of those fancy very low wattage ones. Do you think you will get enough solar power in a couple of months time?

 

You clearly didn't read the post properly.

 

As mentioned this 3rd panel will go up by this weekend and will be be able to tilt fully to any low winter sun, so how much we'll glean will be very interesting.

 

The CH pump is very low wattage, can't remember the make but 0.4 amp I recall.

 

We've managed for 2 months with just 5 hours of generator use, if we had had the additional panel from the beginning that 5 hours wouldn't have been used and probably wouldn't need to be until end October.

 

Even with just the 500 watts today we've been gleaning up to 27 amps in clear sky, and the panel can't fully tilt vertical to the sun on this array. The new panel will though, so hopefully we'll do well on the sunnier days, as I said though we'll see.

 

Not too worried though our generator should be ready soon should we need some good bulk charging.

[ditchcrawler]

 

You clearly didn't read the post properly.

 

As mentioned this 3rd panel will go up by this weekend and will be be able to tilt fully to any low winter sun, so how much we'll glean will be very interesting.

 

The CH pump is very low wattage, can't remember the make but 0.4 amp I recall.

 

We've managed for 2 months with just 5 hours of generator use, if we had had the additional panel from the beginning that 5 hours wouldn't have been used and probably wouldn't need to be until end October.

 

Even with just the 500 watts today we've been gleaning up to 27 amps in clear sky, and the panel can't fully tilt vertical to the sun on this array. The new panel will though, so hopefully we'll do well on the sunnier days, as I said though we'll see.

 

Not too worried though our generator should be ready soon should we need some good bulk charging.

Sorry Have you tried the pump in anger yet, I know it been warm for the time of year and if so are they as good as they say?

[Ex- Member]

Sorry Have you tried the pump in anger yet, I know it been warm for the time of year and if so are they as good as they say?

 

No it's still summer here LOL

 

We did test run the heating a couple of weeks ago, it hardly registered on the ammeter, having said that our fridge only registers 1 amp when it decides to run, so we're unsure as to it's accuracy but it seems to tally with a clamp meter we bought a few weeks ago.

 

The lowest our batteries have been is 11.9v we've never actually run out of power, if the batteries reach 11.9v we just run the engine for 1 hour which will get us through an evening. The alternator puts in around 65 amps continuously during that hour dropping to around 61 amps at the end of it. It does have a sterling charge controller attached. I did run the engine for 2 hours one day but Lynn did a wash in the new washing machine and there was no sun.

[Tony Brooks]

Can I hijack this discussion please.

I've just about got my head around all the in and outs of batteries, most of it gleaned from this forum.

For historical reasons we have two domestic banks. One is 6 full traction cells, giving 900 amp/hr @c5. The other is 440 amp/hr of Lifeline AGM.

As the experts on here will know, the charging routine is different for the different batteries. Because of this I charge the tractions from the combi and the Lifelines from the 12V alternator, with a Sterling controller.

After that ramble, what I would like to know is, can I link the two banks using my 1-2-both switch or is that a no no?

Cheers

Bob

 

 

I think, and am happy to be corrected that you could parallel them up as long as you set the charging voltage for the set with the lower voltage. If they are modern AGMs they may require a higher than optimum for the traction set but as they are probably wet open cells they will put up with modest over volting as long as you keep them topped up. However as 900Ah @C5 is considerably higher at C20 I suspect you could run into charging time problems. Maybe best to stick to what works. That is one very large bank!

[Hawkmoth]

 

 

I think, and am happy to be corrected that you could parallel them up as long as you set the charging voltage for the set with the lower voltage. If they are modern AGMs they may require a higher than optimum for the traction set but as they are probably wet open cells they will put up with modest over volting as long as you keep them topped up. However as 900Ah @C5 is considerably higher at C20 I suspect you could run into charging time problems. Maybe best to stick to what works. That is one very large bank!

Sorry you misunderstood my question, I wasn't clear. I know about the charging, and have dealt with that in how I do it. What I would like to know is what are the negative implications of drawing from both types in parallel.

Cheers

Bob

[Tony Brooks]

I am not sure there is one. One type may start from fully charged with a higher voltage but that type would give up more current than the lower voltage set until both set's voltages were the same. Then they would stay i sync.

 

We really need Gibbo to give us chapter and verse on this. One type may well have a different internal resistance but how this affects the performance I would not like to say.

 

I fell that if there is to be a problem it will be in the recharging, especially if one type has to be charged at less than the recommended voltage.

[Arthur Brown]

Ben- that's one massive bank be sure to keep it fully charged, but keep it as one bank, your "reserve" is the engine starter battery -reun the engine to recharge.

 

Bob- You could parallel rested charged batteries for their discharge but should charge them separately- lots of remembering to switch them.

[Hawkmoth]

.

Bob- You could parallel rested charged batteries for their discharge but should charge them separately- lots of remembering to switch them.

Thanks for that, I always thought it wouldn't be good to parallel them up. I'm glad I asked. Yes I am careful about the charging, I can very quickly tell if I've forgotten to select the right set up.

Bob

[DeanS]

1 bank.

 

from someone who has often told the forum he's splitting into 2 banks.

 

I was wrong.

 

 

 

there. I have confessed.

[ditchcrawler]

1 bank.

 

from someone who has often told the forum he's splitting into 2 banks.

 

I was wrong.

 

 

 

there. I have confessed.

I thought it was 4

[nb Innisfree]

1 bank.

 

from someone who has often told the forum he's splitting into 2 banks.

 

I was wrong.

 

 

 

there. I have confessed.

You will feel better now.