TWO DOMESTIC BATTERY BANKS ?

[tangledfooted]

Hello

At the moment I have a 4x86Ah 12v Yuasa sealed lead acid battery bank - they are about 4 years old. They are charged by a bit of Solar and a 3.7kW generator through a 40A mastervolt charger with room for 3 battery banks. I want to add more capacity but cant get more of the YUASA batteries and would like to fit some TROJANS T125s - I've got the space to fit another bank and don't want to ditch the Yuasas yet.

I can set up a new bank of Trojans and charge them from the spare slot on the Mastervolt charger.

How best should I incorperate them into the existing system?

Assuming all the Neutrals joined together including the starter battery.

Should i just join the two positives leads from both banks together? Thats in parrellel right? would that make 24V? would that effect charging? would that be generally stupid or

Should I add a change over switch and manually swap banks when one has droped too far?

Are there any good wiring diagrams for this set up?

How can I use the solar to charge both banks?

Most of the power ends up going through a 1 kW inverter. I hope to replace the inverter soon with a 3KW / 65A Combi - not sure how many banks the combi will support its at bimble solar under 12v inverters - but if only one then I could use the Mastervolt 40 for the other bank - I've got enough kW on the generator .

I should say that this is a live aboard and we only really take to boat out to get water, pump out etc. We never run the engine to charge the batteries and don't cruise but use the generator and solar. Its fitted with a Adverk AAR but Im not sure its working and this goes through a split charger to charge starter and domestics. I can probably live without worrying so much about charging both domestic banks with the engine

Any thoughts?

[Ex- Member]

I recall asking the same question a couple of years ago. It turned out that running 2 battery banks in my situation was wasteful and following some advice from members we abandoned the idea and went for a larger new battery bank using US2200 6v trojan like batteries.

 

There were some pro's & con's I can't recall all the con's. But basically a bigger reservoir of stored energy worked out more efficient than 2 smaller ones. Smiley Pete and some others will have a much better answers than mine though.

[magnetman]

I asked this years ago when Chris W was on the forum and he said something about a chap called Puekert and not being worth having two batt banks.

 

Sounded convincing enough

 

I still like the idea though

[ditchcrawler]

I do wonder as one bank how they would charge and discharge with one half being open wet and one half sealed with the higher recommended charge voltage for the Trojan.

[Ex- Member]

That's the begger (Peukert's law)

 

Yes I remember now, there was a recent thread somewhere too.

 

I do wonder as one bank how they would charge and discharge with one half being open wet and one half sealed with the higher recommended charge voltage for the Trojan.

 

 

I think natural discharging was another issue too as well as one poorly charged bank drawing from fully charged bank.

Edited January 30, 2014 by Julynian

[tangledfooted]

But what if you think about it as a main domestic bank and a reserve bank. If I treated the Trojan bank 6V 225Ah x2 x2 = 450 Ah 12V and then have a reserve bank of 310 Ah. I mean it would be silly just to discard the Yusua bank. Then I could use the 40A charger for the reserve bank and the 65A charger for the main bank and with a manual changeover switch use each bank one at a time or both at once. Not sure how the Peukert effect effects two banks more than one?

[BEngo]

In general terms you will get more energy out of a single battery bank than out of two smaller ones of the same total size because the discharging is more efficient. Gibbo's smartgauge site explains the why. As magnetman says, it's Peukert's fault....

 

However when the two banks are made of different types of battery and there is only one battery charger one set is going to suffer from sub-optimal charging. The Trojans will charge at a higher voltage than the Yuasa batteries because they are open wet lead acids rather than sealed. With separate banks it will also be easier to tell when the Yuasas have finally expired.

 

If you common all the negatives ( which is OK) and then join the positives from the Yuasas and the Trojans you have not established a separate bank. All the batteries in parallel this way will give you 12V and will charge from the single mastervolt output that is already feeding the Yuasas or from the solar. Adding a connection to the third charger outlet will have little or no effect.

 

To establish a separate bank you need to common the negatives and arrange a separate positive, through a master switch, to the load. The load for the two banks must also be separate. Your idea of a changeover switch could do this, provided it's in the right place. You will need to changeover when one bank gets down. When exactly is best to changeover depends on what your charging regime is in detail. You could then use the third Mastervolt outlet to charge the Trojans. Whether the solar can charge two banks depends on what controller you have. If it has two or three outlets you will be OK.as each outlet can go to one bank.

 

With separate banks it is good to not leave one bank in a part discharged state- this just encourages sulphation and loss of capacity. Even for as little as 24 hours. Again, your charging regime will be a factor.

 

I don't know the mastervolt charger. Can the outputs be adjusted for charging voltage independently? If so set the third one up to suit the Trojans. If not then you will not be able to get the best charging set up for the Trojans The question then is how does the new bank get connected to the load- if you just add a new positive cable from the new bank to the inverter without changing the existing setup this is electrically the same as connecting the positives together and you have not established a separate bank.

 

 

It might help if we can understand why you feel you want more capacity, and how you want to use the existing inverter and new inverter/combi. For example It might be best to leave the existing inverter, charger and batteries on some loads and the new combi and batteries on some other loads, but that may not be feasible, depending on the 240V distribution in the boat. Is there much of a 12V load- lights fridge lappy chargers etc?

 

 

Fortunately we can ignore the engine charging as it's not doing enough to worry about.

 

Sorry it's more questions than answers.

 

N

[tangledfooted]

Thanks N

So As things stand and as its January we run the 3.7kW generator for 11/2 to 2 hours in the morning before work and then for 3 hours at night.

The 40A charger can be set for only one type of battery for all three banks. It has 4 hours Absorption cycle so never gets to float. [ I realise we should try to get to float once a week or so but I have to admit it just doesn't happen - and i wonder sometimes if its worth it because, having eventually got to float stage you really need to keep it there over night to do much good and that isn't practical ? right?]

 

Solar 510 W through a 60A not MPPT CONTROLLER

 

12v pumps, LED lights

 

240v TV , Fridge, DVD Laptops phone chargers Sewing machine Kenwood Chief curlers hairdryer From April to September the solar are great and we only run the genie in the morning for my partners hair dryer: We gave up on the fridge in late September and brought out the gas fridge which we are using now. We also have a washing machine. This will not work directly of the generator so I run it off a Mastervolt 2kW mass sine inverter with the generator running. Works OK up to 30 degrees. The Mastervolt Inverter died last Novemeber and has been in for repair since then. Im pretty sure its buggered. So we have managed with a 1kW PSW inverter as a back up since. So no washing Machine and no fridge at the moment.

 

Most evenings my partner loves her box sets and once I turn off the generator at about 8.30 pm she's got maybe 2 hours before the inverter alarm goes off, certainly by the morning we are normally down to 11.8V. If we forget to turn off the inverter.

 

Any thoughts about curtailing our comsumption are like water of a ducks back as my partner Angela would consider it a blatant infringement of her human rights and probably take me to court. So I need lots of power.

 

So this year my thoughts are that it would be nice to have the fridge working all year and I want to get the washing machine back in service and for my partner to get through series 1 of the Walking Dead in one sitting. AND to run the generator less often.

 

My thoughts 1. More batteries - maybe 4 6v T125s in a new bank alone side the one bank in some form or another.

2. A more powerful charger to run alone side the 40A charger I already have - maybe to charge the new bank.

3. A new inverter 2 - 3kW

4 more solar or maybe a wind turbine [ we are on a CRT mooring so can put it on the land]

 

Obviously cant do all of this in one go so I thought I'd start with the batteries. Whoops Im running out of laptop battery and the inverter has turned it self off . Were down to 11.6v - better go and start the Yanmar ...... Will

[nicknorman]

Sounds like the Yuasas are pretty much knackered, due to undercharging and excessive discharge, if not just old age. It might be best to dump them and have a large bank of new batteries all the same type. If you do want to keep the Yuasas it would be best to have separate charging arrangements due to the differing charging voltage needs. I would have a 1-2-both switch to determine where the charging voltage went, and another 1-2-both switch to determine which bank is being used to power the boat.

 

If you want the Trojans to last you need to charge them at 14.8v with the capability of doing an equalise charge from time to time. Consider doing a long charge each weekend so that they get to 100%.

[bottle]

 

Sounds like the Yuasas are pretty much knackered,

 

My thought as well.

 

 

Bite the bullet, scrap the Yuassa's get some decent batteries and treat them with TLC, adjust or change the charger to one that is adjustable to give an absorption charge until batterries float.

 

Or scrap the Yuassa's but some cheapy batteries, treat them with TLC,adjust or change the charger to one that is adjustable to give an absorption charge until batterries float.

 

or

 

either of the above, forget the TLC, abuse them, change them when knackered, probably the same time scale.

 

 

ps. take the Yuassa's to the scrap yard, it will be worth the trip.

[WotEver]

... AND to run the generator less often.

 

That will require more solar (not an awful lot of use in Winter) or reduced consumption. It wouldn't matter if your bank contained 100 batteries - you still have to put back what you use.

 

Tony

[bottle]

 

you still have to put back what you use.

 

Plus a bit more, innefficiencies, don't you know. ....

[BEngo]

Almost all your load is the inverter. Therefore you want the biggest bank you can afford/ fit in for that, especially if you want to go to a bigger inverter.

 

The yuasas are knackered but will probably soldier on doing just the lights and the pumps for a good while.

 

Whatever you do you need to get a better charging regime. Tou have to put back more than you have used. If you don't the batteries will go flat and get killed simultaneously. That means either a shed load more solar, to deal with winter, or using the generator more.

 

If you don't re-charge them the best batteries will die just as fast as cheap crap.

 

I would suggest:

 

Buy a new battery bank and connect it only to the inverter, charging it by solar and the 40A charger set up for the batteries.

 

Use the existing YUASAs for the 12v loads, charging this off the generator's alternator, if it has one. Uprate the generator alternator if it's not at least 55A. If not charge it off the mastervolt but accept that the batteries ain't gonna like it ( but the batteries are lifex anyway and you may be able to open the tops up to be able to add water which is what they will need.). Split the charge between the generator starter battery and the yuasas with a relay not a diode.

 

Enlarge the new battery bank when you can afford it. Then scrap the yuasas and put the 12V on the new bank

 

Buy some more solar when you can afford it- start with a good MPPT controller. Spend money on solar not wind turbines- it's much better value. Small wind turbines are very ineffective.

 

Run the generator so as to get at least to float once a week. ( at the weekend?) See if you can up the 4-hour absorption period to more nearly match the absorption time of your new batteries. Ideally you want it to switch to float just after the battery starts to gas. You can probably calculate the time crudely by looking at the battery characteristics. Then when it gets to float the batteries will be pretty well full and the solar will be in it's element. If it's not adjustable just switch it off when it gets to float and switch it back on again. That'll give another absorption period. When the battery is pretty full it will rapidly switch to float. If you get the absorption done there's no need to spend a long time in float, though the solar will do that for you if the sun shines.

 

 

N

Edited January 31, 2014 by BEngo

[Robbo]

 

That will require more solar (not an awful lot of use in Winter) or reduced consumption. It wouldn't matter if your bank contained 100 batteries - you still have to put back what you use.

 

Tony

Although if you have a charger that does too many amps for your current battery capacity in bulk mode then getting more battery capacity will shorten the generator time. Edited January 31, 2014 by Robbo

[WotEver]

 

Plus a bit more, innefficiencies, don't you know. ....

 

It's all down to that geezer Pugh Kirk innit?

Although if you have a charger that does too many amps for your current battery capacity in bulk mode then getting more battery capacity will shorten the generator time.

 

By minutes only. Bulk is by far the shortest time of the charging curve.

[Robbo]

 

It's all down to that geezer Pugh Kirk innit?

 

By minutes only. Bulk is by far the shortest time of the charging curve.

 

 

It's a bit more than minutes, but I'll be going from 450 to 900ah capacity with 75amp at bulk to 120amp when I get more Trojans, and the efficiency of my generator will increase (due to having more load nearer to the 75% mark). Increasing capacity also means you extend the periods where you need to start the generator, in summer this means you may use the generator less due to you more likely getting a sunny day (and having the battery capacity to take it).

[tangledfooted]

I've had a chat with the misses and we think we can afford 6 x T105'S. I've check the battery box and they will fit if I remove the YUASA'S. Im going to load test them over the weekend to make sure there finished. If any have some life in them I might well put them on the 12v pumps lights only. [ l Like that idea]

 

The large inverter is a combi - with a 65A charger which we can get next month. Then I could use the 40A charger for the YUASAS and the 65A for the Trojans.

 

I've been thinking about more solar or wind - just thinking that wind might be better in the winter - the solar sort of holds up in the summer. Ill look into that.

 

One problem though. There is only 143mm space above the TROJANS which will make topping up a real chore - any thoughts about automatic top up systems - I can't find anything on google.

 

And finally - yes OK I've been lax - ill need to follow a proper charging regime with a t least 1 weekly float session. So Ill check out the 40A charger to see if I can adjust the variable. With the new batteries - I will. Cheers all for your help - as always.

Will

[Robbo]

I've had a chat with the misses and we think we can afford 6 x T105'S. I've check the battery box and they will fit if I remove the YUASA'S. Im going to load test them over the weekend to make sure there finished. If any have some life in them I might well put them on the 12v pumps lights only. [ l Like that idea]

 

The large inverter is a combi - with a 65A charger which we can get next month. Then I could use the 40A charger for the YUASAS and the 65A for the Trojans.

 

I've been thinking about more solar or wind - just thinking that wind might be better in the winter - the solar sort of holds up in the summer. Ill look into that.

 

One problem though. There is only 143mm space above the TROJANS which will make topping up a real chore - any thoughts about automatic top up systems - I can't find anything on google.

 

And finally - yes OK I've been lax - ill need to follow a proper charging regime with a t least 1 weekly float session. So Ill check out the 40A charger to see if I can adjust the variable. With the new batteries - I will. Cheers all for your help - as always.

Will

 

With a 65amp charger (it has a temperature probe that fits on the batteries?) and 675ah capacity your Trojans won't gas much and therefore won't lose that much water. But here's Trojan's Watering system.... http://www.trojanbattery.com/products/hydrolinks-watering-system/

 

You could put the Trojans on pull out drawers?

Edited January 31, 2014 by Robbo

[BEngo]

 

 

You could put the Trojans on pull out drawers?

oo-er missus!

[smileypete]

Might be worth trying 4xT105 initially, otherwise you're going from ~160Ah Yuasas to 660Ah Trojans, and by the sound of it the Yuasas are probably a fraction of their rated capacity.

 

If you get a DC clamp ammeter, Unitrend UT203 or Mastech MS2108A, £25 online or £40 from Maplins it'll make it very easy to do a power audit and work out what you actually do use.

 

Plus you'll want some sort of ammeter so you can pamper your ££££ Trojans!

 

cheers, Pete.

~smpt~

[tangledfooted]

Oh er ...pull out drawer .. well its not impossible and probably cheaper than a watering system. -In fact definitely cheaper - the Trojan Hydro link system come in at 299 Australian dollars - these days - that's quite a lot. Cant find a UK supplier?

 

Turns out i had a word with a friend at the marina locally and he can get me [ T105'S AT 100GBP each which means I get 675 Ah for 600 pounds] and they are good batteries right? So as long as I can charge em OK - it makes sense. Probably another 50GBP for copper cable although he suggested beating flat 15mm copper pipe and drilling holes and rounding the edges to connect the batteries? Can any one see a problem with that?

 

Ill definitely get the ammeter clamp - really useful and Im looking for a hertz meter with volts and hours to monitor the generators. I've got a Yanmar 3.7 diesel and a 3.5 Susuki converted to LPG and I hope to compare costs over the next year. Im paying 37GPB for 19kG LPG and 78p a litre for red diesel just now.

[nicknorman]

For all the cost of a bit of proper cable, I wouldn't want to have inflexible copper pipe connecting my batteries. Lots of exposed + and - metalwork to provide plenty of opportunity for a disastrous short circuit, and probably contrary to BSS which I think requires conductors to be insulated.

[ditchcrawler]

For all the cost of a bit of proper cable, I wouldn't want to have inflexible copper pipe connecting my batteries. Lots of exposed + and - metalwork to provide plenty of opportunity for a disastrous short circuit, and probably contrary to BSS which I think requires conductors to be insulated.

Vibration would be my worry

[smileypete]

Oh er ...pull out drawer .. well its not impossible and probably cheaper than a watering system. -In fact definitely cheaper - the Trojan Hydro link system come in at 299 Australian dollars - these days - that's quite a lot. Cant find a UK supplier?

 

Try a forum search for 'battery watering', here's one of them:

 

http://www.globalbatteryshop.com/stealth-float-valve-kits-371-p.asp

 

Worth checking they'll fit your Trojans OK.

 

cheers, Pete.

~smpt~

[Alan Saunders]

I've had a chat with the misses and we think we can afford 6 x T105'S. I've check the battery box and they will fit if I remove the YUASA'S. Im going to load test them over the weekend to make sure there finished. If any have some life in them I might well put them on the 12v pumps lights only. [ l Like that idea]

 

The large inverter is a combi - with a 65A charger which we can get next month. Then I could use the 40A charger for the YUASAS and the 65A for the Trojans.

 

I've been thinking about more solar or wind - just thinking that wind might be better in the winter - the solar sort of holds up in the summer. Ill look into that.

 

One problem though. There is only 143mm space above the TROJANS which will make topping up a real chore - any thoughts about automatic top up systems - I can't find anything on google.

 

And finally - yes OK I've been lax - ill need to follow a proper charging regime with a t least 1 weekly float session. So Ill check out the 40A charger to see if I can adjust the variable. With the new batteries - I will. Cheers all for your help - as always.

Will

How will you load test the Yuasas? If you run them down to 1.75V per cell (10.5V) this will further reduce their capacity. If you can provide a constant current you could take measurements at, say, ten minute intervals and extrapolate a graph. Your batteries are sulphated; as well a losing capacity they are much more inefficient to recharge. Even if you replaced them with similar batteries you would be likely to find charging time reduced by 25% to 50%.

 

You do not need to understand Peukert; look at the data sheet for your preferred replacements Trojan Dataheets:

225Ah @ 20hr rate, 185Ah @ 5hr rate, 207Ah@ 10hr rate 250Ah@ 100hr rate. This applies equally to 2V cells in series in a battery or, e.g., 6V batteries in series.

I tend to think that a battery discharged at a higher rate will recover when rested and I am not convinced that it will be less efficient to recharge.

 

I know that I have previously failed to maintain my batteries properly so I replace them annually. My new (cheapest) batteries need a two or three hour daily charge; the knackered ones need three or four hours.

 

HTH, Alan