Solar panels batteries & charge controllers

[Ex- Member]

I'm just about finalising our power requirements for the boat.

 

We're just about to purchase 10 x YUSA 12 volt 78amp batteries which will mainly be charged by 6 x 80 watt solar panels totalling 480 watts with Max 40 Amps output. I've been trying to assess the best charge controller for this set up but find the subject confusing. Can anyone recommend or advise on a decent unit and would a 40amp charge controller suffice or should we go higher?

 

We calculate that engine running through the summer will be minimal but we'll probably have to run the engine on occasion through the winter as the solar output will clearly be a fraction of that obtained in the summer. We do plan to switch off the fridge through the winter though which is our highest output @ 240 volt through inverter and represents just over 50% of our total power requirement.

 

The first six months on the water will act as a trial and from those results we think we can assess quite accurately the power requirement through the winter, adding more solar panels is an option or even back up generation from a diesel genny, basically anything that prevents having to run the boat engine for power unless an emergency or cruising.

 

Bearing the above in mind there's a few things I'm unsure of as follows.

 

The engine has 2 Alt's 1 x 70 amp for the battery bank, pullied up 4.5 to 1 and one 50 amp standard pulley for engine battery.

When getting a good charge from solar and running the boat engine at the same time will this cause any conflict like overload?

 

What happens to the energy a solar panel produces if the batteries are full and no energy being used? ------ Can a charge controller divert this energy elsewhere?

 

Does the distance from the solar panel to the battery bank matter with regard to loss of charge?

 

I'm aware of the 2 best correct ways to wire batteries for equal charging. The optimum though is equal length cable from battery to a single bus bar. The way I have to lay my batteries out might mean that making them all equal might mean each length being over a foot poss 16 inches, will this compromise input/output or will thicker cable overcome this?

 

Thanks all who helped with my YUSA batteries questions.

 

All advice welcome.

 

Julian

[Arthur Brown]

OK you are installing 10 batteries totalling 780 amp hours, that's a LOT remember that self discharge (which is natural) will be 1% per day so you will need to put in ~8AH a day to stand still. These batteries are designed to accept a maximum of 19 amps each but 10 will take 190amps. I'd consider that your "house" generator is small and you would gain benefit from having a bigger one or paralleling the two alternators into the house battery once the starter battery is full.

 

In the summer you can hope for the cells to put out a good power for five hours so you should get 5 x 480 watt hours per day about 2.5kwhrs ie a fair bit but never enough to live well on.

 

solar in parallel with the generator should simply add up, 70 off the genny and 40 off the panels =130 total.

 

The first six months will be a poor measure of the next six as one will be summer the other winter and your power needs will change.

 

solar to battery cable needs to be sized appropriately! for a 40A output current do look at 6 or 10mm^2 cable and put the controller near the batteries.

 

While equal cable length is nice, batteries don't always fit like that in the space allocated, but getting the leads as reasonable equal as possible is good

[Justme]

As you are already planning on fitting more PV panels I would go for a large controller from the start.

 

Some controllers can divert power via a switch / relay controlling a HD relay. Matching the excess to the load is quite difficult so you will still loose some. If your bats are full then the power does not get collected you dont need a dump load like you do for wind turbines.

 

The distance will have an effect on losses but you can minimise them by using thicker cable.

 

Re the alts just make sure you size the cables for the total load / charge inc the PV. Having them working together is not a problem.

[by'eck]

I'm just about finalising our power requirements for the boat.

 

We're just about to purchase 10 x YUSA 12 volt 78amp batteries which will mainly be charged by 6 x 80 watt solar panels totalling 480 watts with Max 40 Amps output. I've been trying to assess the best charge controller for this set up but find the subject confusing. Can anyone recommend or advise on a decent unit and would a 40amp charge controller suffice or should we go higher?

I can recommend Blue Sky products. Check out their SB3024iL 40A 12v Solar Charge Controller here which should be fine since you will rarely see a full 40 amps going into batteries if at all.

 

 

We calculate that engine running through the summer will be minimal but we'll probably have to run the engine on occasion through the winter as the solar output will clearly be a fraction of that obtained in the summer. We do plan to switch off the fridge through the winter though which is our highest output @ 240 volt through inverter and represents just over 50% of our total power requirement.

 

The first six months on the water will act as a trial and from those results we think we can assess quite accurately the power requirement through the winter, adding more solar panels is an option or even back up generation from a diesel genny, basically anything that prevents having to run the boat engine for power unless an emergency or cruising.

 

Bearing the above in mind there's a few things I'm unsure of as follows.

 

The engine has 2 Alt's 1 x 70 amp for the battery bank, pullied up 4.5 to 1 and one 50 amp standard pulley for engine battery.

When getting a good charge from solar and running the boat engine at the same time will this cause any conflict like overload?

It certainly won't cause any harm but the controller/regulator with the highest charge voltage will be dominant. In reality if the battery charge state is holding the controllers below this voltage then they will be working together flat out anyway.

 

 

What happens to the energy a solar panel produces if the batteries are full and no energy being used? ------ Can a charge controller divert this energy elsewhere?

There are controllers with multiple outputs, the one I mentioned above has a second output to feed a separate battery or bank. There is no issue with a multi-stage mppt controller once batteries are fully charged, it will simply run in float mode. Just a minimal current will be drawn from the panels.

 

 

Does the distance from the solar panel to the battery bank matter with regard to loss of charge?

Yes, you want minimal volt drop so use the largest cable gauge recommended for your panels and the shortest run, both from panels to controller & on to the batteries.

 

 

I'm aware of the 2 best correct ways to wire batteries for equal charging. The optimum though is equal length cable from battery to a single bus bar. The way I have to lay my batteries out might mean that making them all equal might mean each length being over a foot poss 16 inches, will this compromise input/output or will thicker cable overcome this?

Doing this may be counter productive. I would use method 2 shown here but its a personal choice.

[Ex- Member]

OK you are installing 10 batteries totalling 780 amp hours, that's a LOT remember that self discharge (which is natural) will be 1% per day so you will need to put in ~8AH a day to stand still. These batteries are designed to accept a maximum of 19 amps each but 10 will take 190amps. I'd consider that your "house" generator is small and you would gain benefit from having a bigger one or paralleling the two alternators into the house battery once the starter battery is full.

 

In the summer you can hope for the cells to put out a good power for five hours so you should get 5 x 480 watt hours per day about 2.5kwhrs ie a fair bit but never enough to live well on.

 

solar in parallel with the generator should simply add up, 70 off the genny and 40 off the panels =130 total.

 

The first six months will be a poor measure of the next six as one will be summer the other winter and your power needs will change.

 

solar to battery cable needs to be sized appropriately! for a 40A output current do look at 6 or 10mm^2 cable and put the controller near the batteries.

 

While equal cable length is nice, batteries don't always fit like that in the space allocated, but getting the leads as reasonable equal as possible is good

 

Thanks Arthur that all makes sense, I forgot to add the alternator on the boat engine has a sterling charging regulator gadget that maximises the charge rate then goes in to float mode.

 

I've been thinking about paralleling the Alt's But might leave this until I see how we get on with the solar (unsure). Our power usage isn't over the top, we don't have auto washing machine or un-necessary gadgets. We're all LED lighting small tv laptop and the fridge which is A+ rated 117kwh although through an inverter, and of course all the usual water pumps.

 

I did a full power audit some time ago and it worked out at 240 amps per day, this was comfortable usage based on our requirements, there's quite a lot of scope for cutting back if necessary like tv and laptop usage i was generous with. so I'm hoping solar might just about cope through the summer. We plan to do washing when cruising using twin tub which washes and dries clothes very quickly in comparison to an Auto and uses less energy.

 

Looking at these charge controllers it's difficult to assess what's what, some cheap ones from China, but are they any good or as good as U.K units up to £300 more even in some cases , any recommendations for particular units welcome, maintaining and protecting the batteries being the main priority though.

 

Plenty to think about, thanks for your input.

 

Julian

 

 

 

 

As you are already planning on fitting more PV panels I would go for a large controller from the start.

 

Some controllers can divert power via a switch / relay controlling a HD relay. Matching the excess to the load is quite difficult so you will still loose some. If your bats are full then the power does not get collected you dont need a dump load like you do for wind turbines.

 

The distance will have an effect on losses but you can minimise them by using thicker cable.

 

Re the alts just make sure you size the cables for the total load / charge inc the PV. Having them working together is not a problem.

 

Hi Justme

 

As you are already planning on fitting more PV panels I would go for a large controller from the start.

 

 

I can only seem to find up to 50 amp units if I add 2 panels it would take me over 50 amps, so I thought if i can get away with a 40amp for the panels i have now, I would have to buy another controller for any additional anyway, if that makes sense.

 

Some controllers can divert power via a switch / relay controlling a HD relay. Matching the excess to the load is quite difficult so you will still loose some. If your bats are full then the power does not get collected you dont need a dump load like you do for wind turbines.

 

 

Thanks, thats useful to know cheers, can you create a dump load say water heater of something?

 

Thanks for your input

 

I can recommend Blue Sky products. Check out their SB3024iL 40A 12v Solar Charge Controller here which should be fine since you will rarely see a full 40 amps going into batteries if at all.

 

 

 

It certainly won't cause any harm but the controller/regulator with the highest charge voltage will be dominant. In reality if the battery charge state is holding the controllers below this voltage then they will be working together flat out anyway.

 

 

 

There are controllers with multiple outputs, the one I mentioned above has a second output to feed a separate battery or bank. There is no issue with a multi-stage mppt controller once batteries are fully charged, it will simply run in float mode. Just a minimal current will be drawn from the panels.

 

 

 

Yes, you want minimal volt drop so use the largest cable gauge recommended for your panels and the shortest run, both from panels to controller & on to the batteries.

 

 

 

Doing this may be counter productive. I would use method 2 shown here but its a personal choice.

 

Great answers cheers Richardhula, I did like the look and spec on the Blue Sky controllers, bit pricy but if they do the job then worth it, thanks for the recommendation.

 

I was thinking the same regarding battery wiring method 2 seems sensible as I'll need loads of new cable more crimping lugs bus bar's etc and as i recall the percentage gain was minimal.

 

 

[Chris Pink]

Don't spend all that money on batteries and panels and go cheap on the controller. Go for an outback mppt controller. I've fitted 2 of these and so wish I could afford one.

 

240 Ah from 480 watts is pushing it. I get 40 -50 from 120w April October and have a surplus June august. But then even in mod-cons mode 240 Ah is generous

[Grace and Favour]

Don't spend all that money on batteries and panels and go cheap on the controller. Go for an outback mppt controller. I've fitted 2 of these and so wish I could afford one.

 

240 Ah from 480 watts is pushing it. I get 40 -50 from 120w April October and have a surplus June august. But then even in mod-cons mode 240 Ah is generous

 

Chris - - I've just had a look at the spec of these Outback mppt's - - - they do look tasty!

 

If I fitted their 60A unit with - lets say, just 300w of panels - with the intention of fitting further panels at a later date (like Julynian) - - will there be any loss of efficiency with 'under-providing' the mppt until such time as I can afford further panels? (you can tell I'm an electrickery dumbo!)

- - but would appreciate your guidance

[Ex- Member]

Don't spend all that money on batteries and panels and go cheap on the controller. Go for an outback mppt controller. I've fitted 2 of these and so wish I could afford one.

 

240 Ah from 480 watts is pushing it. I get 40 -50 from 120w April October and have a surplus June august. But then even in mod-cons mode 240 Ah is generous

 

Hi Chris

 

That is something to mull on, those outback units are well over £500 however if they indeed are more efficient and prolong battery life it could be worth paying. Considering my particular set up do you consider it's worth the extra cost.

 

I realise the amperage output from the 480 watt panels for our needs is boarder line, but we allowed 4 hours tv per day and 4 hours laptop, these are things that can easily be cut down if we want to avoid engine running so there's a bit of leeway there, hopefully a good summer will be on the cards as well

 

Thanks for your input Chris, much appreciated.

 

 

 

[canalowl]

Hi Julian

 

I installed 4 x 90 watt panels around 4 years ago and have 2 x Trojan 6v 420 amp batteries. The solar controller is a SunSaver duo rated at 25 amp. The alternator seems able to put in around 70 amp when batteries are 50% discharged (no controller) and the inverter charger (running off a 5kw generator) is rated at 45 amp charging current. My comments would be:

 

•Although the SunSaver seems to be underspecified the highest solar output to date has been around 27 amp which seems to be well inside its tolerances, possibly because it was at that time a top end controller.

 

•I have a Smart Gauge / Smart Bank monitoring system.

 

•I have thought long and hard about capturing “excess” power but have come to the conclusion that it is negligible and not worth the effort.

 

•I have on occasion had the generator and main engine running on a very sunny day and there has been no problem or conflict between the differing charge sources.

 

•In the winter I tend to do bulk charge with the main engine (up to around 90% charged) and then bring it up to 100% once a week with the generator (when I am doing my weekly wash, hoover and maintenance jobs).

 

•In the height of summer I most probably run the main engine or generator for a couple of hours once a week if not cruising and then let the solar do the topping up.

 

If doing it all again I would definitely fit an MPPT solar controller and may consider another two panels, but this is debatable. My decisions were around convenience and life style (generator curfews used to control my life when working) but prices have come down so much that I suppose investment considerations are increasingly relevant.

 

Dave

[Chris Pink]

If I fitted their 60A unit with - lets say, just 300w of panels - with the intention of fitting further panels at a later date (like Julynian) - - will there be any loss of efficiency with 'under-providing' the mppt until such time as I can afford further panels? (you can tell I'm an electrickery dumbo!)

- - but would appreciate your guidance

 

No you can't 'under-drive' them, although I, for instance, can't really justify one at 120W of panels, I did fit one for 240W and it does its stuff. When i get a moment I intend to get the logged data out of it, that' s one of the great features.

 

the 45A one will go up (in theory) to 550W but I would think in practice it would easily do 600W maybe even more of panels.

 

Considering my particular set up do you consider it's worth the extra cost.

 

 

Yes, definitely, this is the sort of array I would definitely fit one for. the benefits will be immediate and obvious. And budget wise it is in proportion (probably less that either the batteries or the array)

 

I haven't done the sums but there must be a payback point when you load these things up. Claims are 30% extra power.

 

I don't trust the cheaper MPPT controllers at all (there are two technologies) although the Morningstar one looks worth a look but I think the data-logging of the Outback could save a lot of money on monitoring equipment.

[Ex- Member]

Hi Julian

 

I installed 4 x 90 watt panels around 4 years ago and have 2 x Trojan 6v 420 amp batteries. The solar controller is a SunSaver duo rated at 25 amp. The alternator seems able to put in around 70 amp when batteries are 50% discharged (no controller) and the inverter charger (running off a 5kw generator) is rated at 45 amp charging current. My comments would be:

 

•Although the SunSaver seems to be underspecified the highest solar output to date has been around 27 amp which seems to be well inside its tolerances, possibly because it was at that time a top end controller.

 

•I have a Smart Gauge / Smart Bank monitoring system.

 

•I have thought long and hard about capturing "excess" power but have come to the conclusion that it is negligible and not worth the effort.

 

•I have on occasion had the generator and main engine running on a very sunny day and there has been no problem or conflict between the differing charge sources.

 

•In the winter I tend to do bulk charge with the main engine (up to around 90% charged) and then bring it up to 100% once a week with the generator (when I am doing my weekly wash, hoover and maintenance jobs).

 

•In the height of summer I most probably run the main engine or generator for a couple of hours once a week if not cruising and then let the solar do the topping up.

 

If doing it all again I would definitely fit an MPPT solar controller and may consider another two panels, but this is debatable. My decisions were around convenience and life style (generator curfews used to control my life when working) but prices have come down so much that I suppose investment considerations are increasingly relevant.

 

Dave

 

Hi Dave

 

Nothing'd simple when it comes to boats is it LOL And then bring batteries and solar in to the equation as well, we must be mad LOL

 

MPPT definitely seems the way to go though so I'll have to fork out for it. I'm certainly considering a diesel generator rather than running the boat engine if the batteries get to low. Of course days cruising will boost batteries which I consider as bonus power. If we struggle through the summer we'll just add enough panels to suit our needs or cut back on usage which ever we fancy. Adding panels is cheap though if you already have a system set up and the controller capacity to cope with the extra. I'm hoping a diesel genny (Nothing special other than electric start) will suffice through the winter. I've spotted one with flexible exhaust so I can run it in the engine room and exhaust outside, and a lot quieter than the main engine, cost is well under a grand too. I currently run a sterling 20amp charger whilst on dry land, I'll have to up this model to 50amp + so the diesel genny can supply the 240 to run that, Not sure what KVA I'll need for the genny to adequately supply the 50 amp charger? Any idea LOL

 

Thanks for your reply.

 

Julian

 

 

 

[Ex- Member]

No you can't 'under-drive' them, although I, for instance, can't really justify one at 120W of panels, I did fit one for 240W and it does its stuff. When i get a moment I intend to get the logged data out of it, that' s one of the great features.

 

the 45A one will go up (in theory) to 550W but I would think in practice it would easily do 600W maybe even more of panels.

 

 

 

Yes, definitely, this is the sort of array I would definitely fit one for. the benefits will be immediate and obvious. And budget wise it is in proportion (probably less that either the batteries or the array)

 

I haven't done the sums but there must be a payback point when you load these things up. Claims are 30% extra power.

 

I don't trust the cheaper MPPT controllers at all (there are two technologies) although the Morningstar one looks worth a look but I think the data-logging of the Outback could save a lot of money on monitoring equipment.

 

Cheers Chris, looking at the blurb I'm pretty convinced also. The data logging could be really useful too as you can then get a pretty good prediction for the following weeks;months; years as well as having a gist of what to expect on overcast days or hot days so you can adjust your usage appropriately. What I mean is if the weather forecasts a 2 week heat wave, then leave your washing till it comes if you get my drift. Valuable info in so many ways really, be like having a new toy, don't tell er in doors that though Plus it would probably take an additional 3 panels too.

 

If the batteries I want come through the whole lot with said controller cabling etc will be around £1,800 When I was looking at this amount of solar a few years ago it came to over 5k and that's without the posh controller. The cost of diesel today it's a no brainer really.

 

Thanks again Chris.

Edited March 11, 2012 by Julynian

[canalowl]

I currently run a sterling 20amp charger whilst on dry land, I'll have to up this model to 50amp + so the diesel genny can supply the 240 to run that, Not sure what KVA I'll need for the genny to adequately supply the 50 amp charger? Any idea LOL

 

Thanks for your reply.

 

Julian

 

There are others with good experience of suitcase generators on the site but I have often heard 1 kva for 30 amps quoted, although this "feels" a bit tight to me. I think the thing worth noting is that your alternators will most probably do the bulk charge much quicker than the charger and that the important thing about the charger is that it has a good 4 step controller to get you up to 100%. In reality you will rarely use your proposed 50 amp charger to its full capacity if you use the main engine for bulk charging. I like having the bigger generator as it means that I can use lots of power for short periods of time (do various house jobs in multi-tasking mode, the iron is the real killer) - and top up the battery's at the same time.

 

Hope that doesn't confuse further, Dave

[Grace and Favour]

No you can't 'under-drive' them, although I, for instance, can't really justify one at 120W of panels, I did fit one for 240W and it does its stuff. When i get a moment I intend to get the logged data out of it, that' s one of the great features.

 

the 45A one will go up (in theory) to 550W but I would think in practice it would easily do 600W maybe even more of panels.

 

 

 

Yes, definitely, this is the sort of array I would definitely fit one for. the benefits will be immediate and obvious. And budget wise it is in proportion (probably less that either the batteries or the array)

 

I haven't done the sums but there must be a payback point when you load these things up. Claims are 30% extra power.

 

I don't trust the cheaper MPPT controllers at all (there are two technologies) although the Morningstar one looks worth a look but I think the data-logging of the Outback could save a lot of money on monitoring equipment.

 

Chris,

 

That's extremely useful - - - thanks!

 

I think I'll have to start working out how to save up for one now - - but have definitely put one on y wish list!

[smileypete]

Recent thread on Test of cheap MPPT controller.

 

If you really do need to connect 10 batts I'd do it in pairs like this:

 

 

cheers,

Pete.

[Justme]

I would go for the bigger Outback FM80. Yes it costs slightly more than the 60 but you can add more panels as they drop in price. I have 1200watts feeding a FM80. Yes thats more than it can use at peak output (it just does not collect the rest) but it does mean at lower light levels I am getting more power for longer.

 

You could dump to water but as someone else said its costly & it wont happen very often.

 

I would just use it to do an EQ charge cycle.

[Ex- Member]

There are others with good experience of suitcase generators on the site but I have often heard 1 kva for 30 amps quoted, although this "feels" a bit tight to me. I think the thing worth noting is that your alternators will most probably do the bulk charge much quicker than the charger and that the important thing about the charger is that it has a good 4 step controller to get you up to 100%. In reality you will rarely use your proposed 50 amp charger to its full capacity if you use the main engine for bulk charging. I like having the bigger generator as it means that I can use lots of power for short periods of time (do various house jobs in multi-tasking mode, the iron is the real killer) - and top up the battery's at the same time.

Hope that doesn't confuse further, Dave

 

That's helpful Dave not confusing at all.

 

The genny I'm looking at is 3.5 k diesel I'm waiting for conformation that i can fit an extended flexi exhaust so I can keep it in the engine room partly fixed, it has electric start too which is handy. My reasoning for this way is the same as yours, you might well get more charge from the engine but no 240 from it except through the inverter, where as you can do a bit of both with the genny and it uses much less diesel than the main engine and quieter. So like you say we can do hoovering washing, whilst charging. Could also connect the DC charge from the genny and possible get another 8 amps or so. I'm unsure weather that's ok though although I always automatically plugged in the 12 volt charger from the 2kva kippor i have when using it during the build. The other point is the less you have to rely on the main boat engine the more likely it will last longer be more reliable and need less servicing.

 

Being wide beam I have plenty of room for a diesel genny, might even get a 5 or 6 kva enclosed unit in there, but seems a bit over the top.

 

Genny to left of calorifier on ledge.

 

 

 

 

 

Recent thread on Test of cheap MPPT controller.

 

If you really do need to connect 10 batts I'd do it in pairs like this:

 

 

cheers,

Pete.

 

 

That's interesting like making a 156 amp battery at 12 volt from 2 batteries. I'm assuming that's as efficient as wiring one battery in at each end. If so I like it. would the lengths from the battery to the bus bar still need to be of the same length?

 

I would go for the bigger Outback FM80. Yes it costs slightly more than the 60 but you can add more panels as they drop in price. I have 1200watts feeding a FM80. Yes thats more than it can use at peak output (it just does not collect the rest) but it does mean at lower light levels I am getting more power for longer.

 

You could dump to water but as someone else said its costly & it wont happen very often.

 

I would just use it to do an EQ charge cycle.

 

Wow 1200 watts Thought i was the greedy one I'll take a look at the 80 I didn't notice one before, cheers

[smileypete]

That's interesting like making a 156 amp battery at 12 volt from 2 batteries. I'm assuming that's as efficient as wiring one battery in at each end. If so I like it. would the lengths from the battery to the bus bar still need to be of the same length?

As long as the total length of the long and short + and - cables from the common points to each pair of batts are the same, it'll be perfectly balanced.

 

cheers,

Pete.

[Ex- Member]

As long as the total length of the long and short + and - cables from the common points to each pair of batts are the same, it'll be perfectly balanced.

 

cheers,

Pete.

 

Brilliant Pete, thanks for that

[Justme]

 

Wow 1200 watts Thought i was the greedy one

 

 

 

We use on average 3kWh (thats 250ah at 12v) per day (more in winter & less in summer). That includes all laundry & pumping the water out of the ground to our storage tank for a family of 3 & sometimes 4.

 

 

The 1200watt array was sized to give that 3kWh for as much of the year as was cost effective at the time of the install (prices now are about 60% less). In summer we have seen peaks of over 7kWh & in winter we had days (or even weeks) with no power at all.

[Ex- Member]

Thanks to all with the help given on my proposed leccy set up. I do have some further questions I could do with the answer to, I just want to make sure I'm covering all the bases and don't make stupid mistakes.

 

First up Smilypete posted a wiring diagram for the batteries. The batteries I'm hoping yo use dont have normal nipple type studs you simply bolt down the lug in an 8mm stud almost flush with the top of the battery.

 

Photo below

 

http://www.criticalpowersupplies.co.uk/filedata/0000/0381/NPL78-12IFR_UK.pdf

 

As I am proposing 10 x 78amp batteries,Pete suggested doubling up 2 batteries in parallel to make 5 pairs, basically like making a bigger battery so only having to supply 5 Pos and 5 Neg leads of equal size to the bus bars from each pair.

 

Can I link the pairs of batteries with Brass bar 20mm x 6mm thick, or some other type bar, I'll heat shrink where necessary so will this suffice? The other point about this is I can drill a hole in the centre of that bar for each cable destined for the bus bar there for making all connections dead equal to the 2 batteries. This would also save a lot of cable cutting crimping and lugs etc.

 

Due to the way I'll have to lay out the batteries the shortest length of each cable Pos and Neg from each pair of batteries to the bus bar will be 600mm or 60cm What size cable should I use at minimum.

 

Do all lengths have to be the same Pos and Neg?

 

Cables that are naturally near the bus bar, can you coil coil/loop this cable to take up the slack?

 

When batteries are in and fitted the distance then from the alternators to the battery bus bars will be 1.5 metres, If I eventually parallel the Alternators the charge current could be around 150 amps, again what's the minimum cable size via the shunt.

 

With sealed batteries, do they still have to be in a battery box to meet BSS regulations?

 

Thanks again for every ones input thus far, it is much appreciated

[Justme]

I would look for bigger bats & have less than 10 to deal with.

 

Balancing the loads & charging will be an issue when new never mind when one duff cell in one bat starts to mess it all up.

[smileypete]

Can I link the pairs of batteries with Brass bar 20mm x 6mm thick, or some other type bar, I'll heat shrink where necessary so will this suffice? The other point about this is I can drill a hole in the centre of that bar for each cable destined for the bus bar there for making all connections dead equal to the 2 batteries. This would also save a lot of cable cutting crimping and lugs etc.

I'd just use cable to link the pairs of batts, got to be easier than cutting, drilling, tinning and insulating brass bar.

 

 

Due to the way I'll have to lay out the batteries the shortest length of each cable Pos and Neg from each pair of batteries to the bus bar will be 600mm or 60cm What size cable should I use at minimum.

 

Do all lengths have to be the same Pos and Neg?

 

Cables that are naturally near the bus bar, can you coil coil/loop this cable to take up the slack?

OK looking at this diagram:

 

 

The left pair are connected with one short and one medium cable. The middle pair with one medium and another medium cable. The right pair are connected with one long and one short cable.

 

So comparing the lengths:

 

short + long = medium + medium = long + short

 

So each pair of cables from the common points of the bank, has the same total length.

 

Now the voltage drops are directly proportional to the lengths of these cables yes?

 

So the same total length gives the same total voltage drop = balanced bank.

 

 

When batteries are in and fitted the distance then from the alternators to the battery bus bars will be 1.5 metres, If I eventually parallel the Alternators the charge current could be around 150 amps, again what's the minimum cable size via the shunt.

I'd look into using 25mm welding cable throughout, £4 per metre delivered via ebay, maybe buy a meter as a sample to see what it's like? Also use a decent crimp tool and seal over the terminals with glue lined heat-shrink.

 

Now, one thing I would do is space the batts apart a couple of inches. Then in future if you get some wider batts, the cables will still fit OK.

 

 

With sealed batteries, do they still have to be in a battery box to meet BSS regulations?

Don't know but the BSS guide is downloadable from their website, maybe someone here knows for sure.

 

 

I would look for bigger bats & have less than 10 to deal with.

 

Balancing the loads & charging will be an issue when new never mind when one duff cell in one bat starts to mess it all up.

At least it's not a bank of 9 batts.

 

But if 10 is too many it's no problem to remove a couple.

 

cheers,

Pete.

[Ex- Member]

I'd just use cable to link the pairs of batts, got to be easier than cutting, drilling, tinning and insulating brass bar.

 

 

 

OK looking at this diagram:

 

 

The left pair are connected with one short and one medium cable. The middle pair with one medium and another medium cable. The right pair are connected with one long and one short cable.

 

So comparing the lengths:

 

short + long = medium + medium = long + short

 

So each pair of cables from the common points of the bank, has the same total length.

 

Now the voltage drops are directly proportional to the lengths of these cables yes?

 

So the same total length gives the same total voltage drop = balanced bank.

 

 

 

I'd look into using 25mm welding cable throughout, £4 per metre delivered via ebay, maybe buy a meter as a sample to see what it's like? Also use a decent crimp tool and seal over the terminals with glue lined heat-shrink.

 

Now, one thing I would do is space the batts apart a couple of inches. Then in future if you get some wider batts, the cables will still fit OK.

 

 

 

Don't know but the BSS guide is downloadable from their website, maybe someone here knows for sure.

 

 

 

At least it's not a bank of 9 batts.

 

But if 10 is too many it's no problem to remove a couple.

 

cheers,

Pete.

 

Hi Pete

 

Thanks again, I had the wrong end of the stick with regard to cable lengths, think I get it now in that the total length of Neg and Pos combined for each pair of batteries should be the same through the 5 pairs. This will make things somewhat easier and hopefully end up with much shorter equal lengths overall.

 

I have access to a top notch crimper from a boat yard over the way, so no worries there, and I'll cable the battery terminal links as you suggest and use glue lined heat-shrink and 25mm welding cable. The tip about spacing batteries too is taken on board good thinking.

 

These yuasa 78 amp batteries are bigger in overall size than 110 amp wet batteries anyway but I'll still leave a gap for air movement which might assist in keeping them cool anyway.

 

You've been a great help cheers.

 

Julian

 

 

 

[Ex- Member]

I've had some great advice and tips on this thread so thanks to all.

 

Still want to ask a few more things though. Chris Pink recommended the outback charge controller which I'm definitely intending to use. I want to ensure that the new set of batteries I'm getting

8 x 6 volt 232 amp Wet Lead Acid don't get depleted more than 50% in fact I was thinking that no more than 40% drain being the rule and 50% depletion an absolute maximum.

 

Will the Outback controller give an accurate reading of battery power in a percentage term.

 

Or are there other ways also of determining the true level or percentage of the battery banks power. Ie volt readings

 

I want to get this right even to the point of fitting a warning alarm when batteries have drained off 40% or are 60% of total capacity which ever is the more accurate reading.